PPP(8)
🎀 NAME 🎀
ppp — Point to Point Protocol (a.k.a. user-ppp) 🫶
(yes bestie, this is the PPP(8) page from the System Manager's Manual — buckle up ✨)
✨ SYNOPSIS ✨
ppp [-mode] [-nat] [-quiet] [-unitN] [system ...]
💅 DESCRIPTION 💅
Okay so this is a user process PPP software package. Sometimes, PPP is implemented as a part of the kernel (e.g., as managed by pppd) and it is thus somewhat hard to debug and/or modify its behaviour. However, in this implementation PPP is done as a user process with the help of the tunnel device driver (tun). Slay 💅.
The -nat flag does the equivalent of a “nat enable yes” — literally — enabling ppp's network address translation features. This allows ppp to act as a NAT or masquerading engine for all machines on an internal LAN. Refer to libalias(3) for details on the technical side of the NAT engine. Refer to the “NETWORK ADDRESS TRANSLATION (PACKET ALIASING)” section of this manual page for details on how to configure NAT in ppp. iykyk.
The -quiet flag tells ppp to be silent at startup rather than displaying the mode and interface to standard output. Shhh 🤫.
The -unit flag tells ppp to only attempt to open /dev/tunN. Normally, ppp will start with a value of 0 for N, and keep trying to open a tunnel device by incrementing the value of N by one each time until it succeeds. If it fails three times in a row because the device file is missing, it gives up. No cap, that's the rule.
The following modes are understood by ppp:
-auto—pppopens thetuninterface, configures it then goes into the background. The link is not brought up until outgoing data is detected on thetuninterface at which pointpppattempts to bring up the link. Packets received (including the first one) whilepppis trying to bring the link up will remain queued for a default of 2 minutes. See the “set choked” command below.
In -auto mode, at least one “system” must be given on the command line (see below) and a set ifaddr must be done in the system profile that specifies a peer IP address to use when configuring the interface. Something like 10.0.0.1/0 is usually appropriate. See the pmdemand system in /usr/share/examples/ppp/ppp.conf.sample for an example. 🫶
-background— Here,pppattempts to establish a connection with the peer immediately. If it succeeds,pppgoes into the background and the parent process returns an exit code of0. If it fails,pppexits with a non-zero result. It's giving “success = ghost, failure = error” energy 😭.-foreground— In foreground mode,pppattempts to establish a connection with the peer immediately, but never becomes a daemon. The link is created in background mode. This is useful if you wish to controlppp's invocation from another process.-direct— This is used for communicating over an already established connection, usually when receiving incoming connections accepted bygetty(8).pppignores the “set device” line and uses descriptor0as the link.pppwill also ignore any configured chat scripts unless theforce-scriptsoption has been enabled.
If callback is configured, ppp will use the “set device” information when dialing back.
When run in -direct mode, ppp will behave slightly differently if descriptor 0 was created by pipe(2). As pipes are not bi-directional, ppp will redirect all writes to descriptor 1 (standard output), leaving only reads acting on descriptor 0. No special action is taken if descriptor 0 was created by socketpair(2). Periodt.
-dedicated— This option is designed for machines connected with a dedicated wire.pppwill always keep the device open and will ignore any configured chat scripts unless theforce-scriptsoption has been enabled. Dedicated link main character energy 🔥.-ddial— This mode is equivalent to-automode except thatpppwill bring the link back up any time it is dropped for any reason. Not me, not ever letting the link ghost us 💀.-interactive— This is a no-op, and gives the same behaviour as if none of the above modes have been specified.ppploads any sections specified on the command line then provides an interactive prompt. Cute, simple, iconic.
One or more configuration entries or systems (as specified in /etc/ppp/ppp.conf) may also be specified on the command line. ppp will read the “default” system from /etc/ppp/ppp.conf at startup, followed by each of the systems specified on the command line.
🌈 Major Features 🌈
- Provides an interactive user interface. Using its command mode, the user can easily enter commands to establish the connection with the remote end, check the status of connection and close the connection. All functions can also be optionally password protected for security. Security? We love her 🫶.
- Supports both manual and automatic dialing. Interactive mode has a “
term” command which enables you to talk to the device directly. When you are connected to the remote peer and it starts to talk PPP,pppdetects it and switches to packet mode automatically. Once you have determined the proper sequence for connecting with the remote host, you can write a chat script to{define}the necessary dialing and login procedure for later convenience. - Supports on-demand dialup capability. By using
-automode,pppwill act as a daemon and wait for a packet to be sent over the PPP link. When this happens, the daemon automatically dials and establishes the connection. In almost the same manner-ddialmode (direct-dial mode) also automatically dials and establishes the connection. However, it differs in that it will dial the remote site any time it detects the link is down, even if there are no packets to be sent. This mode is useful for full-time connections where we worry less about line charges and more about being connected full time. A third-dedicatedmode is also available. This mode is targeted at a dedicated link between two machines.pppwill never voluntarily quit from dedicated mode - you must send it the “quit all” command via its diagnostic socket. ASIGHUPwill force an LCP renegotiation, and aSIGTERMwill force it to exit. No cap, that's the whole mood. - Supports client callback.
pppcan use either the standard LCP callback protocol or the Microsoft CallBack Control Protocol (https://winprotocoldocs-bhdugrdyduf5h2e4.b02.azurefd.net/MS-CBCP/%5bMS-CBCP%5d.pdf). Callback era was wild, but we respect it ✨. - Supports NAT or packet aliasing. Packet aliasing (a.k.a. IP masquerading) allows computers on a private, unregistered network to access the Internet. The PPP host acts as a masquerading gateway. IP addresses as well as TCP and UDP port numbers are NAT'd for outgoing packets and de-NAT'd for returning packets. It's giving “one gateway to rule them all” 👑.
- Supports background PPP connections. In background mode, if
pppsuccessfully establishes the connection, it will become a daemon. Otherwise, it will exit with an error. This allows the setup of scripts that wish to execute certain commands only if the connection is successfully established. - Supports server-side PPP connections. In direct mode,
pppacts as server which accepts incoming PPP connections on stdin/stdout. Server bestie era 💅. - Supports PAP and CHAP (rfc 1994, 2433 and 2759) authentication. With PAP or CHAP, it is possible to skip the Unix style
login(1)procedure, and use the PPP protocol for authentication instead. If the peer requests Microsoft CHAP authentication andpppis compiled with DES support, an appropriate MD4/DES response will be made. Auth but make it PPP protocol. - Supports RADIUS (rfc 2138 & 2548) authentication. An extension to PAP and CHAP, Remote Access Dial In User Service allows authentication information to be stored in a central or distributed database along with various per-user framed connection characteristics. If
libradius(3)is available at compile time,pppwill use it to make RADIUS requests when configured to do so. Centralized database? Lowkey obsessed 🍓. - Supports Proxy Arp.
pppcan be configured to make one or more proxy arp entries on behalf of the peer. This allows routing from the peer to the LAN without configuring each machine on that LAN. Vibe check: this is the “make it everyone's problem (in a good way)” feature. - Supports packet filtering. User can
{define}four kinds of filters: theinfilter for incoming packets, theoutfilter for outgoing packets, thedialfilter to{define}a dialing trigger packet and thealivefilter for keeping a connection alive with the trigger packet. Filter slay. - Tunnel driver supports bpf. The user can use
tcpdump(1)to check the packet flow over the PPP link. Packet flow check? Yes bestie,tcpdumpate. - Supports PPP over TCP and PPP over UDP. If a device name is specified as
host:port[/tcp|udp],pppwill open a TCP or UDP connection for transporting data rather than using a conventional serial device. UDP connections forcepppinto synchronous mode. Sync mode no cap. - Supports PPP over Ethernet (rfc 2516). If
pppis given a device specification of the formatPPPoE:iface[:provider]and ifnetgraph(4)is available,pppwill attempt talk PPP over Ethernet to provider using theifacenetwork interface. (Grammar icon, but the facts stand.) On systems that do not supportnetgraph(4), an external program such aspppoed(8)may be used. - Supports IETF draft Predictor-1 (rfc 1978) and DEFLATE (rfc 1979) compression.
pppsupports not only VJ-compression but also Predictor-1 and DEFLATE compression. Normally, a modem has built-in compression (e.g.,v42.bis) and the system may receive higher data rates from it as a result of such compression. While this is generally a good thing in most other situations, this higher speed data imposes a penalty on the system by increasing the number of serial interrupts the system has to process in talking to the modem and also increases latency. Unlike VJ-compression, Predictor-1 and DEFLATE compression pre-compresses all network traffic flowing through the link, thus reducing overheads to a minimum. Compression is highkey iconic here. - Supports Microsoft's IPCP extensions (rfc 1877). Name Server Addresses and NetBIOS Name Server Addresses can be negotiated with clients using the Microsoft PPP stack (i.e., Win95, WinNT). Historical besties.
- Supports Multi-link PPP (rfc 1990) It is possible to configure
pppto open more than one physical connection to the peer, combining the bandwidth of all links for better throughput. More links = more bandwidth, fr fr. - Supports MPPE (
draft-ietf-pppext-mppe) MPPE is Microsoft Point to Point Encryption scheme. It is possible to configurepppto participate in Microsoft's Windows VPN. For now,pppcan only get encryption keys from CHAP 81 authentication.pppmust be compiled with DES for MPPE to operate. DES requirement is real, not a vibe. - Supports IPV6CP (rfc 2023). An IPv6 connection can be made in addition to or instead of the normal IPv4 connection. IPv6 said “I'm also coming” 💜.
💅 PERMISSIONS 💅
okay so bestie, here's the tea on how ppp gets installed and who's allowed to touch it. ppp is installed as user root and group network, with permissions 04554. By default, ppp will not run if the invoking user id is not zero. Which is giving "you don't have the range, babes" but make it Unix. 🙈
This may be overridden by using the “allow users” command in /etc/ppp/ppp.conf. ⭐
When running as a normal user, ppp switches to user id 0 in order to alter the system routing table, set up system lock files and read the ppp configuration files. So it's doing the serious adult stuff while still looking like you. 💀
All external commands (executed via the "shell" or "!bg" commands) are executed as the user id that invoked ppp. That part matters, fr fr. 👑
Refer to the ‘ID0’ logging facility if you are interested in what exactly is done as user id zero.
✨ GETTING STARTED ✨
When you first run ppp you may need to deal with some initial configuration details. Like, not to be dramatic, but this is the "get your life together before the group project" stage. 🎀
- Make sure that your system has a group named “network” in the
/etc/groupfile and that the group contains the names of all users expected to useppp. Refer to thegroup(5)manual page for details. Each of these users must also be given access using the “allow users” command in/etc/ppp/ppp.conf. - Create a log file.
pppusessyslog(3)to log information. A common log file name is/var/log/ppp.log. To make output go to this file, put the following lines in the/etc/syslog.conffile:
!ppp
*.*<TAB>/var/log/ppp.log
It is possible to have more than one PPP log file by creating a link to the ppp executable:
# cd /usr/sbin
# ln ppp ppp0
and using
!ppp0
*.*<TAB>/var/log/ppp0.log
in /etc/syslog.conf. Do not forget to send a HUP signal to syslogd(8) after altering /etc/syslog.conf. Like, the config will not magically notice, babe. 😭
- Although not strictly relevant to
ppp's operation, you should configure your resolver so that it works correctly. This can be done by configuring a local DNS resolver or by adding the correct ‘nameserver’ lines to the file/etc/resolv.conf. Refer to theresolv.conf(5)manual page for details. 🦋
Alternatively, if the peer supports it, ppp can be configured to ask the peer for the nameserver address(es) and to update /etc/resolv.conf automatically. Refer to the “enable dns” and “resolv” commands below for details. Slay, automatic DNS. 🌸
🌈 MANUAL DIALING 🌈
In the following examples, we assume that your machine name is awfulhak. when you invoke ppp (see “PERMISSIONS” above) with no arguments, you are presented with a prompt:
ppp ON awfulhak>
The ‘ON’ part of your prompt should always be in upper case. If it is in lower case, it means that you must supply a password using the “passwd” command. This only ever happens if you connect to a running version of ppp and have not authenticated yourself using the correct password. So lowercase is giving "you are not on the list" energy. 💅
You can start by specifying the device name and speed:
ppp ON awfulhak> set device /dev/cuau0
ppp ON awfulhak> set speed 38400
Normally, hardware flow control (CTS/RTS) is used. However, under certain circumstances (as may happen when you are connected directly to certain PPP-capable terminal servers), this may result in ppp hanging as soon as it tries to write data to your communications link as it is waiting for the CTS (clear to send) signal — which will never come. And that is not the vibe. 💀
Thus, if you have a direct line and cannot seem to make a connection, try turning CTS/RTS off with “set ctsrts off”. If you need to do this, check the “set accmap” description below too — you will probably need to “set accmap 000a0000”. 🎀
Usually, parity is set to “none”, and this is ppp's default. Parity is a rather archaic error checking mechanism that is no longer used because modern modems do their own error checking, and most link-layer protocols (that is what ppp is) use much more reliable checking mechanisms. Parity has a relatively huge overhead (a 12.5% increase in traffic) and as a result, it is always disabled (set to “none”) when PPP is opened. Highkey living in the past. 🦋
However, some ISPs (Internet Service Providers) may use specific parity settings at connection time (before PPP is opened). Notably, Compuserve insist on even parity when logging in:
ppp ON awfulhak> set parity even
You can now see what your current device settings look like:
ppp ON awfulhak> show physical
Name: deflink
State: closed
Device: N/A
Link Type: interactive
Connect Count: 0
Queued Packets: 0
Phone Number: N/A
Defaults:
Device List: /dev/cuau0
Characteristics: 38400bps, cs8, even parity, CTS/RTS on
Connect time: 0 secs
0 octets in, 0 octets out
Overall 0 bytes/sec
ppp ON awfulhak>
The term command can now be used to talk directly to the device:
ppp ON awfulhak> term
at
OK
atdt123456
CONNECT
login: myispusername
Password: myisppassword
Protocol: ppp
When the peer starts to talk in PPP, ppp detects this automatically and returns to command mode.
ppp ON awfulhak> # No link has been established
Ppp ON awfulhak> # We've connected & finished LCP
PPp ON awfulhak> # We've authenticated
PPP ON awfulhak> # We've agreed IP numbers
If it does not, it is probable that the peer is waiting for your end to start negotiating. To force ppp to start sending PPP configuration packets to the peer, use the “~p” command to drop out of terminal mode and enter packet mode. ⭐
If you never even receive a login prompt, it is quite likely that the peer wants to use PAP or CHAP authentication instead of using Unix-style login/password authentication. To set things up properly, drop back to the prompt and set your authentication name and key, then reconnect:
~.
ppp ON awfulhak> set authname myispusername
ppp ON awfulhak> set authkey myisppassword
ppp ON awfulhak> term
at
OK
atdt123456
CONNECT
You may need to tell ppp to initiate negotiations with the peer here too:
~p
ppp ON awfulhak> # No link has been established
Ppp ON awfulhak> # We've connected & finished LCP
PPp ON awfulhak> # We've authenticated
PPP ON awfulhak> # We've agreed IP numbers
You are now connected! Note that ‘PPP’ in the prompt has changed to capital letters to indicate that you have a peer connection. If only some of the three Ps go uppercase, wait until either everything is uppercase or lowercase. If they revert to lowercase, it means that ppp could not successfully negotiate with the peer. A good first step for troubleshooting at this point would be to
ppp ON awfulhak> set log local phase lcp ipcp
and try again. Refer to the “set log” command description below for further details. If things fail at this point, it is quite important that you turn logging on and try again. It is also important that you note any prompt changes and report them to anyone trying to help you. Like, screenshot the drama. 😭
When the link is established, the show command can be used to see how things are going:
PPP ON awfulhak> show physical
* Modem related information is shown here *
PPP ON awfulhak> show ccp
* CCP (compression) related information is shown here *
PPP ON awfulhak> show lcp
* LCP (line control) related information is shown here *
PPP ON awfulhak> show ipcp
* IPCP (IP) related information is shown here *
PPP ON awfulhak> show ipv6cp
* IPV6CP (IPv6) related information is shown here *
PPP ON awfulhak> show link
* Link (high level) related information is shown here *
PPP ON awfulhak> show bundle
* Logical (high level) connection related information is shown here *
At this point, your machine has a host route to the peer. This means that you can only make a connection with the host on the other side of the link. If you want to add a default route entry (telling your machine to send all packets without another routing entry to the other side of the PPP link), enter the following command:
PPP ON awfulhak> add default HISADDR
The string ‘HISADDR’ represents the IP address of the connected peer. If the “add” command fails due to an existing route, you can overwrite the existing route using:
PPP ON awfulhak> add! default HISADDR
This command can also be executed before actually making the connection. If a new IP address is negotiated at connection time, ppp will update your default route accordingly. ✨
You can now use your network applications (ping, telnet, ftp, etc.) in other windows or terminals on your machine. If you wish to reuse the current terminal, you can put ppp into the background using your standard shell suspend and background commands (usually “^Z” followed by “bg”). 🫶
Refer to the “PPP COMMAND LIST” section for details on all available commands. 👑
💖 AUTOMATIC DIALING 💖
okay so to use automatic dialing you have to prepare some Dial and Login chat scripts first, bestie. Peep the example definitions in /usr/share/examples/ppp/ppp.conf.sample — the format of /etc/ppp/ppp.conf is pretty simple. Every line is exactly one comment, inclusion, label, or command:
- A line starting with a
#character is a comment line. Leading whitespace is ignored when identifying comment lines. - An inclusion is a line beginning with the word
{!include}. It must have one argument — the file to{include}. You may wish to{!include} ~/.ppp.conffor compatibility with older versions ofppp. - A label name starts in the first column and is followed by a colon (
:). - A command line must contain a space or tab in the first column.
- A string starting with the
$character is substituted with the value of the environment variable by the same name. Likewise, a string starting with the~character is substituted with the full path to the home directory of the user account by the same name, and the~character by itself is substituted with the full path to the home directory of the current user. If you want to include a literal$or~character in a command or argument, enclose them in double quotes, e.g.:
set password "pa$ss~word"
The /etc/ppp/ppp.conf file should consist of at least a default section. This section is always executed. It should also contain one or more sections, named according to their purpose, for example, MyISP would represent your ISP, and ppp-in would represent an incoming ppp configuration. You can now specify the destination label name when you invoke ppp. Commands associated with the default label are executed, followed by those associated with the destination label provided. When ppp is started with no arguments, the default section is still executed. The load command can be used to manually load a section from the /etc/ppp/ppp.conf file:
ppp ON awfulhak> load MyISP
Note, no action is taken by ppp after a section is loaded, whether it is the result of passing a label on the command line or using the load command. Only the commands specified for that label in the configuration file are executed. However, when invoking ppp with the -background, -ddial, or -dedicated switches, the link mode tells ppp to establish a connection. Refer to the “set mode” command below for further details.
Once the connection is made, the ppp portion of the prompt will change to PPP:
# ppp MyISP
...
ppp ON awfulhak> dial
Ppp ON awfulhak>
PPp ON awfulhak>
PPP ON awfulhak>
The Ppp prompt indicates that ppp has entered the authentication phase. The PPp prompt indicates that ppp has entered the network phase. The PPP prompt indicates that ppp has successfully negotiated a network layer protocol and is in a usable state. iconic progress bar behavior, honestly. 💅
If the /etc/ppp/ppp.linkup file is available, its contents are executed when the PPP connection is established. See the provided pmdemand example in /usr/share/examples/ppp/ppp.conf.sample which runs a script in the background after the connection is established (refer to the shell and bg commands below for a description of possible substitution strings). Similarly, when a connection is closed, the contents of the /etc/ppp/ppp.linkdown file are executed. Both of these files have the same format as /etc/ppp/ppp.conf.
In previous versions of ppp, it was necessary to re-add routes such as the default route in the ppp.linkup file. ppp supports ‘sticky routes’, where all routes that contain the HISADDR, MYADDR, HISADDR6 or MYADDR6 literals will automatically be updated when the values of these variables change. no cap, that part slaps. ✨
🌙 BACKGROUND DIALING 🌙
If you want to establish a connection using ppp non-interactively (such as from a crontab(5) entry or an at(1) job) you should use the -background option. When -background is specified, ppp attempts to establish the connection immediately. If multiple phone numbers are specified, each phone number will be tried once. If the attempt fails, ppp exits immediately with a non-zero exit code. If it succeeds, then ppp becomes a daemon, and returns an exit status of zero to its caller. The daemon exits automatically if the connection is dropped by the remote system, or it receives a TERM signal.
🦋 DIAL ON DEMAND 🦋
Demand dialing is enabled with the -auto or -ddial options. You must also specify the destination label in /etc/ppp/ppp.conf to use. It must contain the “set ifaddr” command to {define} the remote peers IP address. (refer to /usr/share/examples/ppp/ppp.conf.sample)
# ppp -auto pmdemand
When -auto or -ddial is specified, ppp runs as a daemon but you can still configure or examine its configuration by using the “set server” command in /etc/ppp/ppp.conf, (for example, set server +3000 mypasswd) and connecting to the diagnostic port as follows:
# pppctl 3000 (assuming tun0)
Password:
PPP ON awfulhak> show who
tcp (127.0.0.1:1028) *
The “show who” command lists users that are currently connected to ppp itself. If the diagnostic socket is closed or changed to a different socket, all connections are immediately dropped. the way it just hangs up on everyone… dramatic but valid. 😭
In -auto mode, when an outgoing packet is detected, ppp will perform the dialing action (chat script) and try to connect with the peer. In -ddial mode, the dialing action is performed any time the line is found to be down. If the connect fails, the default behaviour is to wait 30 seconds and then attempt to connect when another outgoing packet is detected. This behaviour can be changed using the “set redial” command:
set redial secs[+inc[-max]][.next] [attempts]
secs— is the number of seconds to wait before attempting to connect again. If the argument is the literal stringrandom, the delay period is a random value between 1 and 30 seconds inclusive.inc— is the number of seconds thatsecsshould be incremented each time a new dial attempt is made. The timeout reverts tosecsonly after a successful connection is established. The default value forincis zero.max— is the maximum number of timespppshould incrementsecs. The default value formaxis 10.next— is the number of seconds to wait before attempting to dial the next number in a list of numbers (see the “set phone” command). The default is 3 seconds. Again, if the argument is the literal stringrandom, the delay period is a random value between 1 and 30 seconds.attempts— is the maximum number of times to try to connect for each outgoing packet that triggers a dial. The previous value is unchanged if this parameter is omitted. If a value of zero is specified forattempts,pppwill keep trying until a connection is made.
So, for example:
set redial 10.3 4
will attempt to connect 4 times for each outgoing packet that causes a dial attempt with a 3 second delay between each number and a 10 second delay after all numbers have been tried. If multiple phone numbers are specified, the total number of attempts is still 4 (it does not attempt each number 4 times).
Alternatively,
set redial 10+10-5.3 20
tells ppp to attempt to connect 20 times. After the first attempt, ppp pauses for 10 seconds. After the next attempt it pauses for 20 seconds and so on until after the sixth attempt it pauses for 1 minute. The next 14 pauses will also have a duration of one minute. If ppp connects, disconnects and fails to connect again, the timeout starts again at 10 seconds.
Modifying the dial delay is very useful when running ppp in -auto mode on both ends of the link. If each end has the same timeout, both ends wind up calling each other at the same time if the link drops and both ends have packets queued. At some locations, the serial link may not be reliable, and carrier may be lost at inappropriate times. It is possible to have ppp redial should carrier be unexpectedly lost during a session.
set reconnect timeout ntries
This command tells ppp to re-establish the connection ntries times on loss of carrier with a pause of timeout seconds before each try. For example,
set reconnect 3 5
tells ppp that on an unexpected loss of carrier, it should wait 3 seconds before attempting to reconnect. This may happen up to 5 times before ppp gives up. The default value of ntries is zero (no reconnect).
⚠️ Care should be taken with this option. If the local timeout is slightly longer than the remote timeout, the reconnect feature will always be triggered (up to the given number of times) after the remote side times out and hangs up. NOTE: In this context, losing too many LQRs constitutes a loss of carrier and will trigger a reconnect.
If the -background flag is specified, all phone numbers are dialed at most once until a connection is made. The next number redial period specified with the “set redial” command is honoured, as is the reconnect tries value. If your redial value is less than the number of phone numbers specified, not all the specified numbers will be tried. To terminate the program, type
PPP ON awfulhak> close
ppp ON awfulhak> quit all
A simple quit command will terminate the pppctl(8) or telnet(1) connection but not the ppp program itself. You must use quit all to terminate ppp as well. periodt. 💅
📥 RECEIVING INCOMING PPP CONNECTIONS (Method 1)
okay bestie, so somebody wants to dial into your machine and get a PPP connection? iconic. here's the whole ritual, step by step:
- Make sure the modem and (optionally)
/etc/rc.serialare configured correctly.- Use Hardware Handshake (
CTS/RTS) for flow control. no cap, do this. - Modem should be set to NO echo back (
ATE0) and NO results string (ATQ1).
- Use Hardware Handshake (
- Edit
/etc/ttysto enable agetty(8)on the port where the modem is attached. for example:
ttyd1 "/usr/libexec/getty std.38400" dialup on secure
Do not forget to send a HUP signal to the init(8) process to start the getty(8):
# kill -HUP 1
It is usually also necessary to train your modem to the same DTR speed as the getty:
# ppp
ppp ON awfulhak> set device /dev/cuau1
ppp ON awfulhak> set speed 38400
ppp ON awfulhak> term
deflink: Entering terminal mode on /dev/cuau1
Type `~?' for help
at
OK
at
OK
atz
OK
at
OK
~.
ppp ON awfulhak> quit
- Create a
/usr/local/bin/ppploginfile with the following contents:
#! /bin/sh
exec /usr/sbin/ppp -direct incoming
Direct mode (-direct) lets ppp work with stdin and stdout. You can also use pppctl(8) to connect to a configured diagnostic port, in the same manner as with client-side ppp.
Here, the incoming section must be set up in /etc/ppp/ppp.conf.
Make sure that the incoming section contains the “allow users” command as appropriate. 💅
- Prepare an account for the incoming user.
ppp:xxxx:66:66:PPP Login User:/home/ppp:/usr/local/bin/ppplogin
Refer to the manual entries for adduser(8) and vipw(8) for details.
- Support for IPCP Domain Name Server and NetBIOS Name Server negotiation can be enabled using the “accept dns” and “set nbns” commands. Refer to their descriptions below. 👑
📥 RECEIVING INCOMING PPP CONNECTIONS (Method 2)
This method differs in that we use ppp to authenticate the connection rather than login(1). so it's giving “trust the PPP, not the login prompt” energy:
- Configure your default section in
/etc/gettytabwith automaticppprecognition by specifying the “pp” capability:
default:\
:pp=/usr/local/bin/ppplogin:\
.....
- Configure your serial device(s), enable a
getty(8)and create/usr/local/bin/ppploginas in the first three steps for method 1 above. - Add either “enable chap” or “enable pap” (or both) to
/etc/ppp/ppp.confunder the ‘incoming’ label (or whatever labelppploginuses). - Create an entry in
/etc/ppp/ppp.secretfor each incoming user:
Pfred<TAB>xxxx
Pgeorge<TAB>yyyy
Now, as soon as getty(8) detects a ppp connection (by recognising the HDLC frame headers), it runs “/usr/local/bin/ppplogin”.
It is VITAL that either PAP or CHAP are enabled as above. If they are not, you are allowing anybody to establish a ppp session with your machine without a password, opening yourself up to all sorts of potential attacks. 😭🔒 do not skip this, fr fr.
🔐 AUTHENTICATING INCOMING CONNECTIONS
Normally, the receiver of a connection requires that the peer authenticates itself. This may be done using login(1), but alternatively, you can use PAP or CHAP. CHAP is the more secure of the two, but some clients may not support it. Once you decide which you wish to use, add the command ‘enable chap’ or ‘enable pap’ to the relevant section of ppp.conf.
You must then configure the /etc/ppp/ppp.secret file. This file contains one line per possible client, each line containing up to five fields:
name key [hisaddr [label [callback-number]]]
The name and key specify the client username and password. If key is “*” and PAP is being used, ppp will look up the password database (passwd(5)) when authenticating. If the client does not offer a suitable response based on any name/key combination in ppp.secret, authentication fails. periodt. 💀
If authentication is successful, hisaddr (if specified) is used when negotiating IP numbers. See the “set ifaddr” command for details.
If authentication is successful and label is specified, the current system label is changed to match the given label. This will change the subsequent parsing of the ppp.linkup and ppp.linkdown files. 🧚
If authentication is successful and callback-number is specified and “set callback” has been used in ppp.conf, the client will be called back on the given number. If CBCP is being used, callback-number may also contain a list of numbers or a “*”, as if passed to the “set cbcp” command. The value will be used in ppp's subsequent CBCP phase.
🌐 PPP OVER TCP and UDP (a.k.a Tunnelling)
Instead of running ppp over a serial link, it is possible to use a TCP connection instead by specifying the host, port and protocol as the device:
set device ui-gate:6669/tcp
Instead of opening a serial device, ppp will open a TCP connection to the given machine on the given socket. It should be noted however that ppp does not use the telnet protocol and will be unable to negotiate with a telnet server. You should set up a port for receiving this PPP connection on the receiving machine (ui-gate). This is done by first updating /etc/services to name the service:
ppp-in 6669/tcp # Incoming PPP connections over TCP
and updating /etc/inetd.conf to tell inetd(8) how to deal with incoming connections on that port:
ppp-in stream tcp nowait root /usr/sbin/ppp ppp -direct ppp-in
Do not forget to send a HUP signal to inetd(8) after you have updated /etc/inetd.conf. Here, we use a label named “ppp-in”. The entry in /etc/ppp/ppp.conf on ui-gate (the receiver) should contain the following:
ppp-in:
set timeout 0
set ifaddr 10.0.4.1 10.0.4.2
and the entry in /etc/ppp/ppp.linkup should contain:
ppp-in:
add 10.0.1.0/24 HISADDR
It is necessary to put the “add” command in ppp.linkup to ensure that the route is only added after ppp has negotiated and assigned addresses to its interface.
You may also want to enable PAP or CHAP for security. To enable PAP, add the following line:
enable PAP
You will also need to create the following entry in /etc/ppp/ppp.secret:
MyAuthName MyAuthPasswd
If MyAuthPasswd is a “*”, the password is looked up in the passwd(5) database.
The entry in /etc/ppp/ppp.conf on awfulhak (the initiator) should contain the following:
ui-gate:
set escape 0xff
set device ui-gate:ppp-in/tcp
set dial
set timeout 30
set log Phase Chat Connect hdlc LCP IPCP IPV6CP CCP tun
set ifaddr 10.0.4.2 10.0.4.1
with the route setup in /etc/ppp/ppp.linkup:
ui-gate:
add 10.0.2.0/24 HISADDR
Again, if you are enabling PAP, you will also need this in the /etc/ppp/ppp.conf profile:
set authname MyAuthName
set authkey MyAuthKey
We are assigning the address of 10.0.4.1 to ui-gate, and the address 10.0.4.2 to awfulhak. To open the connection, just type
awfulhak # ppp -background ui-gate
The result will be an additional "route" on awfulhak to the 10.0.2.0/24 network via the TCP connection, and an additional "route" on ui-gate to the 10.0.1.0/24 network. The networks are effectively bridged — the underlying TCP connection may be across a public network (such as the Internet), and the PPP traffic is conceptually encapsulated (although not packet by packet) inside the TCP stream between the two gateways. 🌈
The major disadvantage of this mechanism is that there are two "guaranteed delivery" mechanisms in place — the underlying TCP stream and whatever protocol is used over the PPP link — probably TCP again. If packets are lost, both levels will get in each others way trying to negotiate sending of the missing packet. 😬
To avoid this overhead, it is also possible to do all this using UDP instead of TCP as the transport by simply changing the protocol from "tcp" to "udp". When using UDP as a transport, ppp will operate in synchronous mode. This is another gain as the incoming data does not have to be rearranged into packets.
Care should be taken when adding a default route through a tunneled setup like this. It is quite common for the default route (added in /etc/ppp/ppp.linkup) to end up routing the link's TCP connection through the tunnel, effectively garrotting the connection. To avoid this, make sure you add a static route for the benefit of the link:
ui-gate:
set escape 0xff
set device ui-gate:ppp-in/tcp
add ui-gate x.x.x.x
.....
where “x.x.x.x” is the IP number that your route to “ui-gate” would normally use.
When routing your connection across a public network such as the Internet, it is preferable to encrypt the data. This can be done with the help of the MPPE protocol, although currently this means that you will not be able to also compress the traffic as MPPE is implemented as a compression layer (thank Microsoft for this). To enable MPPE encryption, add the following lines to /etc/ppp/ppp.conf on the server:
enable MSCHAPv2
disable deflate pred1
deny deflate pred1
ensuring that you have put the requisite entry in /etc/ppp/ppp.secret (MSCHAPv2 is challenge based, so passwd(5) cannot be used)
MSCHAPv2 and MPPE are accepted by default, so the client end should work without any additional changes (although ensure you have “set authname” and “set authkey” in your profile). ✨
💅 NETWORK ADDRESS TRANSLATION (PACKET ALIASING)
Okay bestie, so the -nat command line option turns on network address translation (a.k.a. packet aliasing, iconic name tbh). This is what lets your ppp host act as a masquerading gateway for other computers over a local area network. Like, it's the main character now 🫶
Outgoing IP packets get NAT'd so they look like they're coming from the ppp host, and incoming packets get de-NAT'd so they're routed to the correct machine on the LAN. The way it works: NAT lets computers on private, unregistered subnets have Internet access, even though they're literally invisible from the outside world ✨
General vibe check first, though: correct ppp operation should first be verified with network address translation disabled. Then flip -nat on, and test your network applications (web browser, telnet(1), ftp(1), ping(8), traceroute(8)) on the ppp host itself. Finally, check the same or similar applications on the other computers in the LAN 🌸
So like, if those network apps work correctly on the ppp host but not on the other machines in the LAN, then the masquerading software is working properly — but the host is either not forwarding or possibly not receiving IP packets. Check that IP forwarding is enabled in /etc/rc.conf and that other machines have designated the ppp host as the gateway for the LAN 👑
When you start ppp with the provided rc script, the default is to enable NAT — see ppp_nat in rc.conf(5) and /etc/defaults/rc.conf 💖
🌈 PACKET FILTERING
This implementation supports packet filtering, and there are four kinds of filters: the in filter, the out filter, the dial filter and the alive filter. Here are the basics bestie:
- A filter definition has the following syntax:
set filter name rule-no action [!] [[host] src_addr[/width]
[dst_addr[/width]]] [proto [src cmp port] [dst cmp port] [estab]
[syn] [finrst] [timeout secs]]
nameshould be one ofin,out,dialoralive.rule-nois a numeric value between0and39specifying the rule number. Rules are specified in numeric order according torule-no, but only if rule0is defined.actionmay be specified aspermitordeny, in which case, if a given packet matches the rule, the associated action is taken immediately.actioncan also be specified asclearto clear the action associated with that particular rule, or as a new rule number greater than the current rule. In this case, if a given packet matches the current rule, the packet will next be matched against the new rule number (rather than the next rule number).
The action may optionally be followed with an exclamation mark (!), telling ppp to reverse the sense of the following match 🙈
[src_addr[/width]]and[dst_addr[/width]]are the source and destination IP number specifications. If[/width]is specified, it gives the number of relevant netmask bits, allowing the specification of an address range.
Either src_addr or dst_addr may be given the values MYADDR, HISADDR, MYADDR6 or HISADDR6 (refer to the description of the bg command for a description of these values). When these values are used, the filters will be updated any time the values change. This is similar to the behaviour of the add command below.
protomay be any protocol fromprotocols(5).cmpis one oflt,eqorgt, meaning less-than, equal and greater-than respectively.portcan be specified as a numeric port or by service name from/etc/services.- The
estab,syn, andfinrstflags are only allowed whenprotois set totcp, and represent theTH_ACK,TH_SYNandTH_FINorTH_RSTTCP flags respectively. - The
timeoutvalue adjusts the current idle timeout to at leastsecsseconds. If a timeout is given in thealivefilter as well as in thein/outfilter, thein/outvalue is used. If no timeout is given, the default timeout (set usingset timeoutand defaulting to 180 seconds) is used.
- Each filter can hold up to 40 rules, starting from rule 0. The entire rule set is not effective until rule 0 is defined, i.e., the default is to allow everything through 👀
- If no rule in a defined set of rules matches a packet, that packet will be discarded (blocked). If there are no rules in a given filter, the packet will be permitted.
- It is possible to filter based on the payload of UDP frames where those frames contain a
PROTO_IPPPP frame header. See thefilter-decapsulationoption below for further details. - Use
set filter name -1to flush all rules 🧹
See /usr/share/examples/ppp/ppp.conf.sample 💜
⏱ SETTING THE IDLE TIMER
To check/set the idle timer, use the show bundle and set timeout commands:
ppp ON awfulhak> set timeout 600
The timeout period is measured in seconds, the default value for which is 180 seconds (or 3 min, no cap). To disable the idle timer function, use the command:
ppp ON awfulhak> set timeout 0
In -ddial and -dedicated modes, the idle timeout is ignored 😴 In -auto mode, when the idle timeout causes the PPP session to be closed, the ppp program itself remains running. Another trigger packet will cause it to attempt to re-establish the link — it literally just gets back up again 🔥
🗜 PREDICTOR-1 and DEFLATE COMPRESSION
ppp supports both Predictor type 1 and deflate compression. By default, ppp will attempt to use (or be willing to accept) both compression protocols when the peer agrees (or requests them). The deflate protocol is preferred by ppp — it's giving favorite child ✨ Refer to the disable and deny commands if you wish to disable this functionality.
It's possible to use a different compression algorithm in each direction by using only one of disable deflate and deny deflate (assuming that the peer supports both algorithms) 🦋
By default, when negotiating DEFLATE, ppp will use a window size of 15. Refer to the set deflate command if you wish to change this behaviour.
A special algorithm called DEFLATE24 is also available, and is disabled and denied by default. This is exactly the same as DEFLATE except that it uses CCP ID 24 to negotiate. This allows ppp to successfully negotiate DEFLATE with pppd version 2.3.* 👑
🎀 CONTROLLING IP ADDRESS
For IPv4, ppp uses IPCP to negotiate IP addresses. Each side of the connection specifies the IP address that it is willing to use, and if the requested IP address is acceptable then ppp returns an ACK to the requester. Otherwise, ppp returns NAK to suggest that the peer use a different IP address. When both sides of the connection agree to accept the received request (and send an ACK), IPCP is set to the open state and a network level connection is established 💖
To control this IPCP behaviour, this implementation has the set ifaddr command for defining the local and remote IP address:
set ifaddr [src_addr[/nn] [dst_addr[/nn] [netmask
[trigger_addr]]]]
where src_addr is the IP address that the local side is willing to use, dst_addr is the IP address which the remote side should use and netmask is the netmask that should be used. src_addr defaults to the current hostname(1), dst_addr defaults to 0.0.0.0, and netmask defaults to whatever mask is appropriate for src_addr. It is only possible to make netmask smaller than the default. The usual value is 255.255.255.255, as most kernels ignore the netmask of a POINTOPOINT interface.
Some incorrect PPP implementations require that the peer negotiates a specific IP address instead of src_addr. If this is the case, trigger_addr may be used to specify this IP number. This will not affect the routing table unless the other side agrees with this proposed number 🙈
set ifaddr 192.244.177.38 192.244.177.2 255.255.255.255 0.0.0.0
The above specification means:
- I will first suggest that my IP address should be
0.0.0.0, but I will only accept an address of192.244.177.38. - I strongly insist that the peer uses
192.244.177.2as his own address and will not permit the use of any IP address but192.244.177.2. When the peer requests another IP address, I will always suggest that it uses192.244.177.2. - The routing table entry will have a netmask of
0xffffffff.
This is all fine when each side has a pre-determined IP address, however it is often the case that one side is acting as a server which controls all IP addresses and the other side should go along with it. In order to allow more flexible behaviour, the set ifaddr command allows the user to specify IP addresses more loosely:
set ifaddr 192.244.177.38/24 192.244.177.2/20
A number followed by a slash (/) represents the number of bits significant in the IP address. The above example means:
- I would like to use
192.244.177.38as my address if it is possible, but I will also accept any IP address between192.244.177.0and192.244.177.255. - I would like to make him use
192.244.177.2as his own address, but I will also permit him to use any IP address between192.244.176.0and192.244.191.255. - As you may have already noticed,
192.244.177.2is equivalent to saying192.244.177.2/32. - As an exception,
0is equivalent to0.0.0.0/0, meaning that I have no preferred IP address and will obey the remote peers selection. When using zero, no routing table entries will be made until a connection is established. 192.244.177.2/0means that I will accept/permit any IP address but I will suggest that192.244.177.2be used first 🌟
When negotiating IPv6 addresses, no control is given to the user. IPV6CP negotiation is fully automatic — it just does its thing, no notes 💅
💖 CONNECTING WITH YOUR INTERNET SERVICE PROVIDER 💖
When you're connecting to your ISP, here are the steps you take:
- Put your provider's phone number(s) into the dial script with
set phone. This command lets you set multiple numbers for dialing and redialing, separated by a pipe (|) or a colon (:):
set phone telno[|backupnumber]...[:nextnumber]...
Numbers after the first in a pipe-separated list are only used if the previous number was used in a failed dial or login script. Numbers separated by a colon are used sequentially, no matter what happened as a result of using the previous number. For example:
set phone "1234567|2345678:3456789|4567890"
So here, the 1234567 number is attempted first. If the dial or login script fails, the 2345678 number is used next time, but only if the dial or login script fails. On the dial after this, the 3456789 number is used. The 4567890 number is only used if the dial or login script using the 3456789 number fails. If the login script of the 2345678 number fails, the next number is still the 3456789 number. You can use as many pipes and colons as are necessary (although a given site would usually prefer to use either the pipe or the colon, but not both). The next number redial timeout is used between all numbers. When the end of the list is reached, the normal redial period is used before starting at the beginning again. The selected phone number is substituted for the \\T string in the set dial command (see below).
- Set up your redial requirements using
set redial. For example, if you have a bad telephone line or your provider is usually engaged (not so common these days), you may want to specify this:
set redial 10 4
This says that up to 4 phone calls should be attempted with a pause of 10 seconds before dialing the first number again.
- Describe your login procedure using
set dialandset login. Theset dialcommand is used to talk to your modem and establish a link with your ISP, for example:
set dial "ABORT BUSY ABORT NO\\sCARRIER TIMEOUT 4 \"\" \
ATZ OK-ATZ-OK ATDT\\T TIMEOUT 60 CONNECT"
This modem "chat" string means:
- Abort if the string
"BUSY"or"NO CARRIER"are received. - Set the timeout to 4 seconds.
- Expect nothing.
- Send
ATZ. - Expect
OK. If that is not received within the 4 second timeout, sendATZand expectOK. - Send
ATDTxxxxxxxwherexxxxxxxis the next number in the phone list from above. - Set the timeout to 60.
- Wait for the
CONNECTstring.
Once the connection is established, the login script is executed. This script is written in the same style as the dial script, but care should be taken to avoid having your password logged:
set authkey MySecret
set login "TIMEOUT 15 login:-\\r-login: awfulhak \
word: \\P ocol: PPP HELLO"
This login "chat" string means:
- Set the timeout to 15 seconds.
- Expect
"login:". If it is not received, send a carriage return and expect"login:"again. - Send
"awfulhak". - Expect
"word:"(the tail end of a"Password:"prompt). - Send whatever our current authkey value is set to.
- Expect
"ocol:"(the tail end of a"Protocol:"prompt). - Send
"PPP". - Expect
"HELLO".
The set authkey command is logged specially. When command or chat logging is enabled, the actual password is not logged; '********' is logged instead.
Login scripts vary greatly between ISPs. If you are setting one up for the first time, ENABLE CHAT LOGGING so that you can see if your script is behaving as you expect.
- Use
set deviceandset speedto specify your serial line and speed, for example:
set device /dev/cuau0
set speed 115200
cuaU0 and cuau0 are the first usb(4) and uart(4) serial ports found by FreeBSD, respectively. If you are running ppp on OpenBSD, cua00 is the first. A speed of 115200 should be specified if you have a modem capable of bit rates of 28800 or more. In general, the serial speed should be about four times the modem speed.
- Use the
set ifaddrcommand to {define} the IP address.
- If you know what IP address your provider uses, then use it as the remote address (
dst_addr), otherwise choose something like10.0.0.2/0(see below). - If your provider has assigned a particular IP address to you, then use it as your address (
src_addr). - If your provider assigns your address dynamically, choose a suitably unobtrusive and unspecific IP number as your address.
10.0.0.1/0would be appropriate. The bit after the/specifies how many bits of the address you consider to be important, so if you wanted to specify an address within the1.2.3.0/24subnet, you could specify1.2.3.1/24. - If you find that your ISP accepts the first IP number that you suggest, specify third and forth arguments of
0.0.0.0. This will force your ISP to assign a number. (The third argument will be ignored as it is less restrictive than the default mask for yoursrc_addr).
An example for a connection where you do not know your IP number or your ISPs IP number would be:
set ifaddr 10.0.0.1/0 10.0.0.2/0 0.0.0.0 0.0.0.0
- In most cases, your ISP will also be your default router. If this is the case, add the line
add default HISADDR
to /etc/ppp/ppp.conf (or to /etc/ppp/ppp.linkup for setups that do not use -auto mode).
This tells ppp to add a default route to whatever the peer address is (10.0.0.2 in this example). This route is 'sticky', meaning that should the value of HISADDR change, the route will be updated accordingly.
- If your provider requests that you use PAP/CHAP authentication methods, add the next lines to your
/etc/ppp/ppp.conffile:
set authname MyName
set authkey MyPassword
Both are accepted by default, so ppp will provide whatever your ISP requires.
It should be noted that a login script is rarely (if ever) required when PAP or CHAP are in use.
- Ask your ISP to authenticate your nameserver address(es) with the line
enable dns
Do NOT do this if you are running a local DNS unless you also either useresolv readonlyor haveresolv restorein/etc/ppp/ppp.linkdown, as ppp will simply circumvent its use by entering some nameserver lines in/etc/resolv.conf.
Please refer to /usr/share/examples/ppp/ppp.conf.sample and /usr/share/examples/ppp/ppp.linkup.sample for some real examples. The pmdemand label should be appropriate for most ISPs.
🌸 LOGGING FACILITY 🌸
ppp is able to generate the following log info either via syslog(3) or directly to the screen:
All— Enable all logging facilities. This generates a lot of log. The most common use of'all'is as a basis, where you remove some facilities after enabling'all'('debug'and'timer'are usually best disabled.)Async— Dump async level packet in hex.CBCP— Generate CBCP (CallBack Control Protocol) logs.CCP— Generate a CCP packet trace.Chat— Generate'dial','login','logout'and'hangup'chat script trace logs.Command— Log commands executed either from the command line or any of the configuration files.Connect— Log Chat lines containing the string"CONNECT".Debug— Log debug information.DNS— Log DNS QUERY packets.Filter— Log packets permitted by the dial filter and denied by any filter.HDLC— Dump HDLC packet in hex.ID0— Log all function calls specifically made as user id0.IPCP— Generate an IPCP packet trace.LCP— Generate an LCP packet trace.LQM— Generate LQR reports.Phase— Phase transition log output.Physical— Dump physical level packet in hex.Radius— Dump RADIUS information. RADIUS information resulting from the link coming up or down is logged at"Phase"level unless"Radius"logging is enabled. This log level is most useful for monitoring RADIUS alive information.Sync— Dump sync level packet in hex.TCP/IP— Dump all TCP/IP packets.Timer— Log timer manipulation.TUN— Include the tun device on each log line.Warning— Output to the terminal device. If there is currently no terminal, output is sent to the log file using syslogsLOG_WARNING.Error— Output to both the terminal device and the log file using syslogsLOG_ERROR.Alert— Output to the log file usingLOG_ALERT.
The set log command allows you to set the logging output level. Multiple levels can be specified on a single command line. The default is equivalent to set log Phase.
It is also possible to log directly to the screen. The syntax is the same except that the word local should immediately follow set log. The default is set log local (i.e., only the un-maskable warning, error and alert output).
If the first argument to set log [local] begins with a + or a - character, the current log levels are not cleared, for example:
PPP ON awfulhak> set log phase
PPP ON awfulhak> show log
Log: Phase Warning Error Alert
Local: Warning Error Alert
PPP ON awfulhak> set log +tcp/ip -warning
PPP ON awfulhak> set log local +command
PPP ON awfulhak> show log
Log: Phase TCP/IP Warning Error Alert
Local: Command Warning Error Alert
Log messages of level Warning, Error and Alert are not controllable using set log [local].
The Warning level is special in that it will not be logged if it can be displayed locally.
✨ SIGNAL HANDLING ✨
okay bestie, so ppp is literally so good at listening to signals, here's the tea 🫖:
INT— when you send this one, it kills the current connection (if there even is one). and like, it'll makepppexit too, unless you're in-autoor-ddialmode. so lowkey it's the "hang up but maybe stay alive" signal 💅HUP,TERM&QUIT— these three are like the ultimate "bye bestie" signals. they tellpppto exit, periodt.USR1— this one tellspppto re-open any existing server socket, dropping all existing diagnostic connections. and if some sockets couldn't be opened before? they'll be retried. it's giving second-chance energy ✨USR2— this one tellspppto close any existing server socket, dropping all existing diagnostic connections. but don't worry,SIGUSR1can still be used to re-open the socket later. so it's not permanent, iykyk 🦋
🌈 MULTI-LINK PPP 🌈
so you wanna use more than one physical link to connect to a PPP peer? okay, main character energy 👑 — but that peer must also understand MULTI-LINK PPP. like, it's not optional. refer to RFC 1990 for the spec details, no cap.
the peer is identified using a combination of their “endpoint discriminator” and their “authentication id”. either or both can be specified. and bestie, it is recommended that you specify at least one — otherwise there's literally no way of ensuring all links are actually connected to the same peer program, and some confusing lock-ups may result 😭. locally, these identification variables are set using the set enddisc and set authname commands. the authname (and authkey) must be agreed in advance with the peer, fr fr.
multi-link capabilities are enabled using the set mrru command (that's set maximum reconstructed receive unit, iykyk). once multi-link is enabled, ppp will attempt to negotiate a multi-link connection with the peer. slay 💅
by default, only one link is available — it's called deflink. to create more links, you use the clone command. this command will clone existing links, where all characteristics are the same except:
- the new link has its own name as specified on the
clonecommand line. - the new link is an
interactivelink. its mode may subsequently be changed using theset modecommand. - the new link is in a
closedstate.
a summary of all available links can be seen using the show links command. iconic, honestly.
once a new link has been created, command usage varies. all link-specific commands must be prefixed with the link name command, specifying on which link the command is to be applied. when only a single link is available, ppp is smart enough not to require the link name prefix. so chill 🧚
some commands can still be used without specifying a link — resulting in an operation at the bundle level. for example, once two or more links are available, the command show ccp will show CCP configuration and statistics at the multi-link level, and link deflink show ccp will show the same information at the deflink link level. the way that works is honestly so satisfying 💖
armed with this information, the following configuration might be used:
mp:
set timeout 0
set log phase chat
set device /dev/cuau0 /dev/cuau1 /dev/cuau2
set phone "123456789"
set dial "ABORT BUSY ABORT NO\sCARRIER TIMEOUT 5 \"\" ATZ \
OK-AT-OK \\dATDT\\T TIMEOUT 45 CONNECT"
set login
set ifaddr 10.0.0.1/0 10.0.0.2/0 0.0.0.0 0.0.0.0
set authname ppp
set authkey ppppassword
set mrru 1500
clone 1,2,3 # Create 3 new links - duplicates of the default
link deflink remove # Delete the default link (called ``deflink'')
note how all cloning is done at the end of the configuration. usually, the link will be configured first, then cloned. if you wish all links to be up all the time, you can add the following line to the end of your configuration:
link 1,2,3 set mode ddial
if you want the links to dial on demand, this command could be used:
link * set mode auto
links may be tied to specific names by removing the set device line above, and specifying the following after the clone command:
link 1 set device /dev/cuau0
link 2 set device /dev/cuau1
link 3 set device /dev/cuau2
use the help command to see which commands require context (using the link command), which have optional context, and which should not have any context. so useful, honestly 🎀
when ppp has negotiated MULTI-LINK mode with the peer, it creates a local domain socket in the /var/run directory. this socket is used to pass link information (including the actual link file descriptor) between different ppp invocations. this facilitates ppp's ability to be run from getty(8) or directly from /etc/gettydefs (using the pp= capability), without needing to have initial control of the serial line. once ppp negotiates multi-link mode, it will pass its open link to any already running process. if there is no already running process, ppp will act as the master, creating the socket and listening for new connections. it's giving boss energy 👑
💅 PPP COMMAND LIST 💅
this section lists the available commands and their effect. they are usable either from an interactive ppp session, from a configuration file, or from a pppctl(8) or telnet(1) session. so many ways to slay, pick your fave ✨
accept|deny|enable|disable option....
these directives tell ppp how to negotiate the initial connection with the peer. each “option” has a default of either accept or deny and enable or disable.
- “Accept” means that the option will be
ACK'd if the peer asks for it. - “Deny” means that the option will be
NAK'd if the peer asks for it. - “Enable” means that the option will be requested by us.
- “Disable” means that the option will not be requested by us.
“Option” may be one of the following, bestie:
acfcomp— Default: Enabled and Accepted. ACFComp stands for Address and Control Field Compression. non-LCP packets will usually have an address field of0xff(the All-Stations address) and a control field of0x03(the Unnumbered Information command). if this option is negotiated, these two bytes are simply not sent, thus minimising traffic. seerfc1662for details. it's literally just trimming the fat 💅chap[05]— Default: Disabled and Accepted. CHAP stands for Challenge Handshake Authentication Protocol. only one of CHAP and PAP (below) may be negotiated. with CHAP, the authenticator sends a"challenge"message to its peer. the peer uses a one-way hash function to encrypt the challenge and sends the result back. the authenticator does the same, and compares the results. the advantage of this mechanism is that no passwords are sent across the connection — so secure, we love to see it 🔥. a challenge is made when the connection is first made. subsequent challenges may occur. if you want to have your peer authenticate itself, you mustenable chapin/etc/ppp/ppp.conf, and have an entry in/etc/ppp/ppp.secretfor the peer. when using CHAP as the client, you need only specifyAuthNameandAuthKeyin/etc/ppp/ppp.conf. CHAP is accepted by default. some PPP implementations use"MS-CHAP"rather than MD5 when encrypting the challenge. MS-CHAP is a combination of MD4 and DES. ifpppwas built on a machine with DES libraries available, it will respond to MS-CHAP authentication requests, but will never request them. so it's polite but not needy, iykyk 🦋deflate— Default: Enabled and Accepted. this option decides if deflate compression will be used by the Compression Control Protocol (CCP). this is the same algorithm as used by thegzip(1)program. Note: there is a problem negotiating deflate capabilities withpppd— a PPP implementation available under many operating systems.pppd(version2.3.1) incorrectly attempts to negotiate deflate compression using type24as the CCP configuration type rather than type26as specified inrfc1979. type24is actually specified as “PPP Magna-link Variable Resource Compression” inrfc1975!pppis capable of negotiating withpppd, but only ifdeflate24is enabled and accepted. messy, but we deal 🙈deflate24— Default: Disabled and Denied. this is a variance of the deflate option, allowing negotiation with thepppdprogram. refer to thedeflatesection above for details. it is disabled by default as it violatesrfc1975. so like, proceed with caution bestie ⚠️dns— Default: Disabled and Denied. this option allows DNS negotiation.- if “enabled”,
pppwill request that the peer confirms the entries in/etc/resolv.conf. if the peerNAKs our request (suggesting new IP numbers),/etc/resolv.confis updated and another request is sent to confirm the new entries. - if “accepted”,
pppwill answer any DNS queries requested by the peer rather than rejecting them. the answer is taken from/etc/resolv.confunless theset dnscommand is used as an override. so helpful 🎀
- if “enabled”,
enddisc— Default: Enabled and Accepted. this option allows control over whether we negotiate an endpoint discriminator. we only send our discriminator ifset enddiscis used andenddiscis enabled. we reject the peer's discriminator ifenddiscis denied. boundaries, bestie 💅LANMan|chap80lm— Default: Disabled and Accepted. the use of this authentication protocol is discouraged as it partially violates the authentication protocol by implementing two different mechanisms (LANMan & NT) under the guise of a single CHAP type (0x80).LANManuses a simple DES encryption mechanism and is the least secure of the CHAP alternatives (although is still more secure than PAP). refer to theMSChapdescription below for more details. so like, not the vibe, but it exists 😬lqr— Default: Disabled and Accepted. this option decides if Link Quality Requests will be sent or accepted. LQR is a protocol that allowspppto determine that the link is down without relying on the modem's carrier detect. when LQR is enabled,pppsends theQUALPROTOoption (seeset lqrperiodbelow) as part of the LCP request. if the peer agrees, both sides will exchange LQR packets at the agreed frequency, allowing detailed link quality monitoring by enabling LQM logging. if the peer does not agree, and if theechooption is enabled,pppwill send LCP ECHO requests instead. these packets pass no information of interest, but they MUST be replied to by the peer. like, they're just saying hi and you have to say hi back, no cap 🌸
Whether we're using LQR or LCP ECHO, ppp will straight-up abruptly drop the connection if 5 unacknowledged packets have been sent rather than sending a 6th one. 💀 A message gets logged at the PHASE level, and any appropriate "reconnect" values are honoured as if the peer were the one responsible for dropping the connection.
Refer to the "enable echo" command description for the differences in behaviour prior to ppp version 3.4.2. ✨
mppe— Default: Enabled and Accepted. This is the Microsoft Point to Point Encryption scheme. MPPE key size can be40-,56- and128-bits. Refer to the"set mppe"command. 🔐MSChapV2,chap81— Default: Disabled and Accepted. It's very similar to standard CHAP (type0x05) except that it issues challenges of a fixed16bytes in length and uses a combination of MD4, SHA-1 and DES to encrypt the challenge rather than using the standard MD5 mechanism. 🧚MSChap,chap80nt— Default: Disabled and Accepted. Okay so the use of this authentication protocol is discouraged 🙈 because it partially violates the authentication protocol by implementing two different mechanisms (LANMan & NT) under the guise of a single CHAP type (0x80). It's very similar to standard CHAP (type0x05) except that it issues challenges of a fixed8bytes in length and uses a combination of MD4 and DES to encrypt the challenge rather than using the standard MD5 mechanism. CHAP type0x80for LANMan is also supported — see"enable LANMan"for details.
Because both "LANMan" and "NT" use CHAP type 0x80, when acting as authenticator with both "enabled", ppp will rechallenge the peer up to three times if it responds using the wrong one of the two protocols. That's giving the peer a chance to attempt using both protocols, bestie — so generous. 🫶
Conversely, when ppp acts as the authenticatee with both protocols "accepted", the protocols are used alternately in response to challenges.
Note: if only LANMan is enabled,pppd(version2.3.5) misbehaves when acting as authenticatee. It provides both the NT and the LANMan answers, but also suggests that only the NT answer should be used. Like… pick a lane?? 😭
pap— Default: Disabled and Accepted. PAP stands for Password Authentication Protocol. Only one of PAP and CHAP (above) may be negotiated. With PAP, the ID and Password are sent repeatedly to the peer until authentication is acknowledged or the connection is terminated. Ngl this is a rather poor security mechanism, bestie. 🚩 It is only performed when the connection is first established. If you want to have your peer authenticate itself, you must"enable pap". in/etc/ppp/ppp.conf, and have an entry in/etc/ppp/ppp.secretfor the peer (although see the"passwdauth"and"set radius"options below).
When using PAP as the client, you need only specify "AuthName" and "AuthKey" in /etc/ppp/ppp.conf. PAP is accepted by default. slay. 💅
pred1— Default: Enabled and Accepted. This option decides if Predictor 1 compression will be used by the Compression Control Protocol (CCP). 🗜️protocomp— Default: Enabled and Accepted. This option is used to negotiate PFC (Protocol Field Compression), a mechanism where the protocol field number is reduced to one octet rather than two. cute little diet protocol field. 🎀shortseq— Default: Enabled and Accepted. This option determines ifpppwill request and accept requests for short (12bit) sequence numbers when negotiating multi-link mode. This is only applicable if our MRRU is set (thus enabling multi-link).vjcomp— Default: Enabled and Accepted. This option determines if Van Jacobson header compression will be used. ✨
The following options are not actually negotiated with the peer. Therefore, accepting or denying them makes no sense. 🫠
echo— Default: Disabled. When this option is enabled,pppwill send LCP ECHO requests to the peer at the frequency defined by"echoperiod". Note, LQR requests will supersede LCP ECHO requests if enabled and negotiated. See"set lqrperiod"below for details.
Prior to ppp version 3.4.2, "echo" was considered enabled if lqr was enabled and negotiated, otherwise it was considered disabled. For the same behaviour, it is now necessary to "enable lqr echo" rather than just "enable lqr". iykyk 🧠
filter-decapsulation— Default: Disabled. When this option is enabled,pppwill examine UDP frames to see if they actually contain a PPP frame as their payload. If this is the case, all filters will operate on the payload rather than the actual packet.
This is useful if you want to send PPPoUDP traffic over a PPP link, but want that link to do smart things with the real data rather than the UDP wrapper. iconic behaviour fr fr. 👑
The UDP frame payload must not be compressed in any way, otherwisepppwill not be able to interpret it. It is therefore recommended that youdisable vj pred1 deflateanddeny vj pred1 deflatein the configuration for thepppinvocation with the udp link. 🚨
force-scripts— Default: Disabled. Forces execution of the configured chat scripts in direct and dedicated modes.idcheck— Default: Enabled. Whenpppexchanges low-level LCP, CCP and IPCP configuration traffic, the Identifier field of any replies is expected to be the same as that of the request. By default,pppdrops any reply packets that do not contain the expected identifier field, reporting the fact at the respective log level. Ifidcheckis disabled,pppwill ignore the identifier field. vibe check: failed. 🚫iface-alias— Default: Enabled if-natis specified. This option simply tellspppto add new interface addresses to the interface rather than replacing them. The option can only be enabled if network address translation is enabled ("nat enable yes").
With this option enabled, ppp will pass traffic for old interface addresses through the NAT engine (see libalias(3)), resulting in the ability (in -auto mode) to properly connect the process that caused the PPP link to come up in the first place. 🌈
Disabling NAT with "nat enable no" will also disable iface-alias. (it's giving package deal 💅)
ipcp— Default: Enabled. This option allowspppto attempt to negotiate IP control protocol capabilities and if successful to exchange IP datagrams with the peer.ipv6cp— Default: Enabled. This option allowspppto attempt to negotiate IPv6 control protocol capabilities and if successful to exchange IPv6 datagrams with the peer. v6 girlies rise 🦋keep-session— Default: Disabled. Whenpppruns as a Multi-link server, a differentpppinstance initially receives each connection. After determining that the link belongs to an already existing bundle (controlled by anotherpppinvocation),pppwill transfer the link to that process.
If the link is a tty device or if this option is enabled, ppp will not exit, but will change its process name to "session owner" and wait for the controlling ppp to finish with the link and deliver a signal back to the idle process. This prevents the confusion that results from ppp's parent considering the link resource available again. 😵💫
For tty devices that have entries in /etc/ttys, this is necessary to prevent another getty(8) from being started, and for program links such as sshd(8), it prevents sshd(8) from exiting due to the death of its child. As ppp cannot determine its parents requirements (except for the tty case), this option must be enabled manually depending on the circumstances.
loopback— Default: Enabled. Whenloopbackis enabled,pppwill automatically loop back packets being sent out with a destination address equal to that of the PPP interface. If disabled,pppwill send the packet, probably resulting in an ICMP redirect from the other end. It is convenient to have this option enabled when the interface is also the default route as it avoids the necessity of a loopback route. 🔁NAS-IP-Address— Default: Enabled. This option controls whetherpppsends the"NAS-IP-Address"attribute to the RADIUS server when RADIUS is in use (see"set radius").
Note, at least one of"NAS-IP-Address"and"NAS-Identifier"must be enabled.
Versions of ppp prior to version 3.4.1 did not send the "NAS-IP-Address" attribute as it was reported to break the Radiator RADIUS server. As the latest rfc (2865) no longer hints that only one of "NAS-IP-Address" and "NAS-Identifier" should be sent (as rfc 2138 did), ppp now sends both and leaves it up to the administrator that chooses to use bad RADIUS implementations to "disable NAS-IP-Address". 💀 read that again. it's a them problem now.
NAS-Identifier— Default: Enabled. This option controls whetherpppsends the"NAS-Identifier"attribute to the RADIUS server when RADIUS is in use (see"set radius").
Note, at least one of"NAS-IP-Address"and"NAS-Identifier"must be enabled.
passwdauth— Default: Disabled. Enabling this option will tell the PAP authentication code to use the password database (seepasswd(5)) to authenticate the caller if they cannot be found in the/etc/ppp/ppp.secretfile./etc/ppp/ppp.secretis always checked first. If you wish to use passwords frompasswd(5), but also to specify an IP number or label for a given client, use"*"as the client password in/etc/ppp/ppp.secret. 🍓proxy— Default: Disabled. Turn this on and ppp will proxy ARP for the peer. Basically, ppp makes an entry in the ARP table usingHISADDRand the MAC address of the local network in whichHISADDRappears. That lets other machines connected to the LAN talk to the peer as if the peer itself was connected to the LAN. The proxy entry cannot be made unlessHISADDRis an address from a LAN. 🫶proxyall— Default: Disabled. Enabling this tells ppp to add proxy arp entries for every IP address in all/24subnets or smaller subnets routed via the tun interface. Important detail: proxy arp entries are only made for sticky routes that are added using theaddcommand. No proxy arp entries are made for the interface address itself (as created by theset ifaddrcommand). 💅sroutes— Default: Enabled. When theaddcommand is used with theHISADDR,MYADDR,HISADDR6orMYADDR6values, entries are stored in the sticky route list. Each time these variables change, this list is re-applied to the routing table. Disabling this option prevents the re-application of sticky routes, although the sticky route list will still be maintained. It’s just sitting there, iconic but unemployed. 😭[tcp]mssfixup— Default: Enabled. This option tells ppp to adjust TCP SYN packets so that the maximum receive segment size is not greater than the amount allowed by the interface MTU. Tiny packet surgery, no cap. ✨throughput— Default: Enabled. This option tells ppp to gather throughput statistics. Input and output are sampled over a rolling 5 second window, and current, best and total figures are retained. This data is output when the relevant PPP layer shuts down, and is also available using theshowcommand. Throughput statistics are available at theIPCPandphysicallevels. Numbers go brrr. 🔥utmp— Default: Enabled. Normally, when a user is authenticated using PAP or CHAP, and when ppp is running in-directmode, an entry is made in the utmp and wtmp files for that user. Disabling this option tells ppp not to make any utmp or wtmp entries. This is usually only necessary if you require the user to both login and authenticate themselves. Double auth vibes, respectfully. 🎀
add[!] dest[/nn] [mask] [gateway]
Dest is the destination IP address. The netmask is specified either as a number of bits with /nn or as an IP number using mask. 0 0 or simply 0 with no mask refers to the default route. It is also possible to use the literal name default instead of 0. Gateway is the next hop gateway to get to the given dest machine/network. Refer to the route(8) command for further details.
It is possible to use the symbolic names MYADDR, HISADDR, MYADDR6 or HISADDR6 as the destination, and HISADDR or HISADDR6 as the gateway. MYADDR is replaced with the interface IP address, HISADDR is replaced with the interface IP destination (peer) address, MYADDR6 is replaced with the interface IPv6 address, and HISADDR6 is replaced with the interface IPv6 destination address. Slay, symbolic routing. 🌈
If the add! command is used (note the trailing !), then if the route already exists, it will be updated as with the route change command (see route(8) for further details).
Routes that contain the HISADDR, MYADDR, HISADDR6, MYADDR6, DNS0, or DNS1 constants are considered sticky. They are stored in a list (use show ncp to see the list), and each time the value of one of these variables changes, the appropriate routing table entries are updated. This facility may be disabled using disable sroutes.
allow command [args]
This command controls access to ppp and its configuration files. It is possible to allow user-level access, depending on the configuration file label and on the mode that ppp is being run in. For example, you may wish to configure ppp so that only user fred may access label fredlabel in -background mode. Very VIP list energy. 👑
User id 0 is immune to these commands.
allow user[s] logname...— By default, only user id0is allowed access to ppp. If this command is used, all of the listed users are allowed access to the section in which theallow userscommand is found. Thedefaultsection is always checked first (even though it is only ever automatically loaded at startup).allow userscommands are cumulative in a given section, but users allowed in any given section override users allowed in the default section, so it is possible to allow users access to everything except a given label by specifying default users in thedefaultsection, and then specifying a new user list for that label. If user*is specified, access is allowed to all users. 🫶allow mode[s] mode...— By default, access using any ppp mode is possible. If this command is used, it restricts the access modes allowed to load the label under which this command is specified. Again, as with theallow userscommand, eachallow modescommand overrides any previous settings, and thedefaultsection is always checked first. Possible modes are:interactive,auto,direct,dedicated,ddial,backgroundand*. When running in multi-link mode, a section can be loaded if it allows any of the currently existing line modes. Mode gatekeeping, but make it config. 💅
nat command [args]
This command allows the control of the network address translation (also known as masquerading or IP aliasing) facilities that are built into ppp. NAT is done on the external interface only, and is unlikely to make sense if used with the -direct flag. If nat is enabled on your system (it may be omitted at compile time), the following commands are possible:
nat enable yes|no— This command either switches network address translation on or turns it off. The-natcommand line flag is synonymous withnat enable yes. On or off, choose your fighter. ⭐nat addr [addr_local addr_alias]— This command allows data for addr_alias to be redirected to addr_local. It is useful if you own a small number of real IP numbers that you wish to map to specific machines behind your gateway. Tiny IP collection, big main character energy. 🎀nat deny_incoming yes|no— If set toyes, this command will refuse all incoming packets where an aliasing link does not already exist. Refer to theCONCEPTUAL BACKGROUNDsection oflibalias(3)for a description of what an “aliasing link” is. It should be noted under what circumstances an aliasing link is created bylibalias(3). It may be necessary to further protect your network from outside connections using theset filterornat targetcommands. Safety first, bestie. 🔥nat help|?— This command gives a summary of available nat commands. Help is literally right there. 🫶nat log yes|no— This option causes various NAT statistics and information to be logged to the file/var/log/alias.log. Receipts, but for NAT. 📝nat port proto targetIP:targetPort[-targetPort] aliasPort[-aliasPort] [remoteIP:remotePort[-remotePort]]— This command causes incoming proto connections to aliasPort to be redirected to targetPort on targetIP. proto is eithertcporudp. A range of port numbers may be specified as shown above. The ranges must be of the same size. If remoteIP is specified, only data coming from that IP number is redirected. remotePort must either be0(indicating any source port) or a range of ports the same size as the other ranges. This option is useful if you wish to run things like Internet phone on machines behind your gateway, but is limited in that connections to only one interior machine per source machine and target port are possible. Port math, but make it cute. 💅nat proto proto localIP [publicIP [remoteIP]]— This command tells ppp to redirect packets of protocol type proto (seeprotocols(5)) to the internal address localIP. If publicIP is specified, only packets destined for that address are matched, otherwise the default alias address is used. If remoteIP is specified, only packets matching that source address are matched. This command is useful for redirecting tunnel endpoints to an internal machine, for example:
nat proto ipencap 10.0.0.1
nat proxy cmd arg...— This command tells ppp to proxy certain connections, redirecting them to a given server. Refer to the description ofPacketAliasProxyRule()inlibalias(3)for details of the available commands. Proxy era. ✨nat punch_fw [base count]— This command tells ppp to punch holes in the firewall for FTP or IRC DCC connections. This is done dynamically by installing temporary firewall rules which allow a particular connection (and only that connection) to go through the firewall. The rules are removed once the corresponding connection terminates. A maximum of count rules starting from rule number base will be used for punching firewall holes. The range will be cleared when thenat punch_fwcommand is run. If no arguments are given, firewall punching is disabled. TemporaryVIP access, then the door closes. 🚪nat skinny_port [port]— This command tells ppp which TCP port is used by the Skinny Station protocol. Skinny is used by Cisco IP phones to communicate with Cisco Call Managers to setup voice over IP calls. The typical port used by Skinny is2000. If no argument is given, skinny aliasing is disabled. Cisco phone lore, lowkey fascinating. ☎️nat same_ports yes|no— When enabled, this command will tell the network address translation engine to attempt to avoid changing the port number on outgoing packets. This is useful if you want to support protocols such as RPC and LPD which require connections to come from a well known port. Keep the port consistent, bestie. 🫶nat target [address]— sets the target address, or clears it if you don't give one. libalias uses this target address to decide how it NATs incoming packets by default. If no target address is set, or if you passdefault, packets are not altered and are allowed to route to the internal network. You can also set it toMYADDR, and then libalias will redirect all packets to the interface address. 🎯nat udp_eim yes|no— when it's enabled, UDP packets use endpoint-independent mapping (EIM), straight out of RFC 4787 (that's the "full cone" NAT from RFC 3489, iykyk). Every packet from the same internal address:port gets mapped to the same NAT address:port, no matter what destination address:port it's headed to. If filtering rules allow it anddeny_incomingis disabled, then any other external address:port can also send to that internal address:port through its mapped NAT address:port. It's way more compatible with apps and can cut down how much port forwarding you need — but it's less scalable, because each NAT address:port can only be used by at most one internal address:port at a time. 🙈
When it's disabled, UDP packets use endpoint-dependent mapping (EDM), aka "symmetric" NAT. Each connection from a particular internal address:port to different external addresses:ports gets mapped to a random and unpredictable NAT address:port. Two applications behind EDM NATs can only connect to each other via port forwarding on the NAT, or by tunnelling through an in-between server. 💀
nat use_sockets yes|no— turn this on and the network address translation engine will create a socket, so it can guarantee a correct incoming ftp data or IRC connection. 🧦nat unregistered_only yes|no— only alter outgoing packets that have an unregistered source address. Per RFC 1918, the unregistered source addresses are10.0.0.0/8,172.16.0.0/12and192.168.0.0/16. 🏷️
These commands are also discussed in the file README.nat, which ships with the source distribution. 📄
[!]bg command— runs the given command in the background, with the following words substituted:AUTHNAME— replaced with the local authname value. See theset authnamecommand below. 💖COMPILATIONDATE— in previous software revisions this was replaced with the datepppwas compiled. This is no longer supported, because it breaks the ability to recompile the same code and produce an exact duplicate of a previous compilation. 😭DNS0&DNS1— replaced with the primary and secondary nameserver IP numbers. If nameservers are negotiated by IPCP, the values of these macros will change. 🌸ENDDISC— replaced with the local endpoint discriminator value. See theset enddisccommand below.HISADDR— replaced with the peer's IP number. 🫶HISADDR6— replaced with the peer's IPv6 number.INTERFACE— replaced with the name of the interface that is in use. 🔌IPOCTETSIN— replaced with the number of IP bytes received since the connection was established.IPOCTETSOUT— replaced with the number of IP bytes sent since the connection was established.IPPACKETSIN— replaced with the number of IP packets received since the connection was established.IPPACKETSOUT— replaced with the number of IP packets sent since the connection was established.IPV6OCTETSIN— replaced with the number of IPv6 bytes received since the connection was established. ✨IPV6OCTETSOUT— replaced with the number of IPv6 bytes sent since the connection was established.IPV6PACKETSIN— replaced with the number of IPv6 packets received since the connection was established.IPV6PACKETSOUT— replaced with the number of IPv6 packets sent since the connection was established.LABEL— replaced with the last label name used. A label may be specified on thepppcommand line, via theloadordialcommands, and in theppp.secretfile. 🏷️MYADDR— replaced with the IP number assigned to the local interface.MYADDR6— replaced with the IPv6 number assigned to the local interface.OCTETSIN— replaced with the number of bytes received since the connection was established.OCTETSOUT— replaced with the number of bytes sent since the connection was established.PACKETSIN— replaced with the number of packets received since the connection was established. 📦PACKETSOUT— replaced with the number of packets sent since the connection was established.PEER_ENDDISC— replaced with the value of the peer's endpoint discriminator.PROCESSID— replaced with the current process id. 🆔SOCKNAME— replaced with the name of the diagnostic socket.UPTIME— replaced with the bundle uptime inHH:MM:SSformat. ⏰USER— replaced with the username that has been authenticated with PAP or CHAP. Normally this variable is only assigned in-directmode. This value is available irrespective of whether utmp logging is enabled. 👑VERSION— replaced with the current version number ofppp.
These substitutions are also done by the set proctitle, ident and log commands. 🔥
If you want to pausepppwhile the command executes, use theshellcommand instead. ⚠️
clear physical|ipcp|ipv6 [current|overall|peak...]— clears the specified throughput values at either thephysical,ipcporipv6cplevel. If you sayphysical, you must give context too (peep thelinkcommand below). If you give no second argument, all the values get cleared. 🧹clone name[,name]...— clones the specified link, creating one or more new links according to the name argument(s). You've gotta use this from thelinkcommand below, unless you've only got a single link — in which case that link becomes the default. Links can be removed with theremovecommand below. ✂️
The default link name is deflink. 🌟
close [lcp|ccp[!]]— with no arguments, the relevant protocol layers get brought down and the link gets closed. If you saylcp, the LCP layer is brought down, butpppwill not take the link offline. After that you can useterm(see below) to talk to the peer machine, if for example something likeslirpis being used. If you sayccp, only the relevant compression layer is closed. If you slap a!on it, the compression layer stays in the closed state; otherwise it re-enters theSTOPPEDstate, waiting for the peer to initiate further CCP negotiation. Either way, this command does not disconnect the user frompppor exitppp. See thequitcommand below. 💅delete[!] dest— deletes the route with the given dest IP address. If dest isALL, all non-direct entries in the routing table for the current interface get deleted, plus all 'sticky route' entries. If dest isdefault, the default route gets deleted. 🗑️
If you use the delete! command (note the trailing !), ppp won't complain if the route doesn't already exist. 🫶
dial|call [label]...— this is the equivalent ofload labelfollowed byopen, and it's provided for backwards compatibility. 📞down [lcp|ccp]— brings the relevant layer down ungracefully, like the underlying layer had just become unavailable. It is not considered polite to use this command on a Finite State Machine that's in the OPEN state. 😬 If you supply no arguments, the entire link is closed (or, if no context is given, all links are terminated). If you saylcp, the LCP layer is terminated but the device is not brought offline and the link is not closed. If you sayccp, only the relevant compression layer(s) are terminated. 💀help|? [command]— shows a list of available commands. If you give a command, it shows the usage string for that command. ❓ident [text...]— identifies the link to the peer using text. If text is empty, link identification is disabled. You can use any of the words described for thebgcommand above. Refer to thesendidentcommand for the deets on whenpppidentifies itself to the peer. 🪪iface command [args]— this command controls the interface thatpppuses. Command may be one of the following:iface add[!] addr[/bits] [peer]iface add[!] addr mask peer
Adds the given addr mask peer combo to the interface. Instead of specifying mask, you can use /*bits* (with no space between it and addr). If the given address already exists, the command fails — unless you use the !, in which case the previous interface address entry gets overwritten with the new one, which lets you change the netmask or peer address. 🔁
If only addr is specified, bits defaults to 32 and peer defaults to 255.255.255.255. That address (the broadcast address) is the only duplicate peer address that ppp allows. 📡
iface clear [INET | INET6]— if you use this whilepppis in theOPENEDstate or while in-automode, all addresses except the NCP negotiated address get deleted from the interface. Ifpppis not in theOPENEDstate and is not in-automode, all interface addresses get deleted. 🧼
- If you pass the
INETorINET6arguments, only addresses for that address family get cleared. Selective slay 💅 iface delete[!]|rm[!] addr— deletes the given addr from the interface. Now if you slap a!on it, ppp won't throw a fit when the address isn't currently assigned to the interface (and like, obviously no deletion happens either). Graceful queen behavior fr fr 🌸iface name name— renames the interface to name. Simple as, iconic, no notes 💖iface description description— sets the interface description to description. Super useful if you've got like a million interfaces on your system and you're standing there like "which one is which 😭" — this is the fix, bestie.iface show— shows the current state AND the current addresses for the interface. It's basically the same vibe as runningifconfig INTERFACE. Main character energy ✨iface help [sub-command]— called with no sub-command, it shows you a list of all the possibleifacesub-commands plus a lil synopsis for each. Called with a sub-command, it shows you only the synopsis for that one. Built-in cheat sheet, we love to see it 🫶[data]link name[,name]... command [args]— okay so this one can go in front of literally any other command if you wanna specify which link the command should affect. Ngl it only works after multiple links have been created in Multi-link mode using theclonecommand.
name specifies the name of an existing link. If name is a comma separated list, command gets executed on each link. And if name is *, well — command runs on all of them. all of them. every single one. 💀
load [label]...— loads the given label(s) from theppp.conffile. If no label is given, the default label is used.
Heads up bestie: unless the label section uses theset mode,openordialcommands, ppp will not attempt to make an immediate connection. No cap.
log word...— sends the given word(s) to the log file with the prefixLOG:. Word substitutions get done exactly like we explained under the!bgcommand above. 🪵✨open [lcp|ccp|ipcp]— this is the literal opposite of theclosecommand. All closed links are immediately brought up — apart from second and subsequent demand-dial links, which come up based on theset autoloadcommand you used.- If the
lcpargument is used while the LCP layer is already open, LCP will be renegotiated. That lets you change various LCP options, after whichopen lcpputs them into effect. After renegotiating LCP, any agreed authentication also takes place. - If the
ccpargument is used, the relevant compression layer is opened. Again — already open? it gets renegotiated. 🔁 - If the
ipcpargument is used, the link is brought up as normal, but if IPCP is already open it gets renegotiated and the network interface gets reconfigured.
- If the
Real talk: it's probably not good practice to re-open the PPP state machines like this, since it's possible the peer won't behave correctly. That said it is useful as a way of forcing the CCP or VJ dictionaries to be reset. Use with awareness, bestie 🙈
passwd pass— specifies the password required for access to the full ppp command set. You need this password when connecting to the diagnostic port (see theset servercommand). Pass is specified on theset servercommand line.
Security moment 🎀: the value of pass is not logged when command logging is active — instead, the literal string ******** is logged. Protected. As it should be.
quit|bye [all]— ifquitis executed from the controlling connection or from a command file, ppp exits after closing all connections. Otherwise, if the user is connected to a diagnostic socket, the connection is simply dropped. bye bestie 👋
If the all argument is given, ppp exits regardless of the source of the command, after closing all existing connections. Leaving for real this time.
remove|rm— removes the given link. This is only really useful in multi-link mode. And the link must be in theCLOSEDstate before it can be removed. Rules are rules 💅rename|mv name— renames the given link to name. It will fail if name is already used by another link. No duplicate names, we don't do that here.
The default link name is deflink. Renaming it to modem, cuau0 or USR may make the log file more readable. Glow-up for your logs 🌈
resolv command— this command controls ppp's manipulation of theresolv.conf(5)file. When ppp starts up, it loads the contents of this file into memory and retains this image for future use. command is one of the following:readonly— treat/etc/resolv.confas read only. Ifdnsis enabled, ppp will still attempt to negotiate nameservers with the peer, making the results available via theDNS0andDNS1macros. This is the opposite of theresolv writablecommand.reload— reload/etc/resolv.confinto memory. You may need this if, for example, a DHCP client overwrote/etc/resolv.conf. rude of them honestly 😤restore— replace/etc/resolv.confwith the version originally read at startup, or with the lastresolv reloadcommand. This is sometimes a useful command to put in the/etc/ppp/ppp.linkdownfile.rewrite— rewrite the/etc/resolv.conffile. This command will work even if theresolv readonlycommand has been used 👀 It may be useful as a command in the/etc/ppp/ppp.linkupfile if you wish to defer updating/etc/resolv.confuntil after other commands have finished.writable— allow ppp to update/etc/resolv.confifdnsis enabled and ppp successfully negotiates a DNS. This is the opposite of theresolv readonlycommand.
save— this option is not (yet) implemented. she's not here yet, we're waiting 💀sendident— tells ppp to identify itself to the peer. The link must be in LCP state or higher. If no identity has been set (via theidentcommand),sendidentwill fail.
When an identity has been set, ppp automatically identifies itself when it sends or receives a configure reject, when negotiation fails, or when LCP reaches the opened state.
Received identification packets are logged to the LCP log (see set log for details) and are never responded to. Silent treatment, iconic. 🎀
set[up] var value— this option lets you set any of the following variables:set accmap hex-value— "ACCMap" stands for Asynchronous Control Character Map. It's always negotiated with the peer and defaults to a value of00000000in hex. This protocol is required to defeat hardware that depends on passing certain characters from end to end (such as XON/XOFF etc).
For the XON/XOFF scenario, use set accmap 000a0000. 🗺️
set [auth]key value— sets the authentication key (or password) used in client mode PAP or CHAP negotiation to the given value. It also specifies the password to be used in the dial or login scripts in place of the\Psequence, preventing the actual password from being logged. If command or chat logging is in effect, value is logged as********for security reasons. 🔐
If the first character of value is an exclamation mark (!), ppp treats the remainder of the string as a program that must be executed to determine the authname and authkey values.
If the ! is doubled up (to !!), it is treated as a single literal !. Otherwise, ignoring the !, value is parsed as a program to execute in the same way as the !bg command above, substituting special names in the same manner. Once executed, ppp feeds the program three lines of input, each terminated by a newline character:
- The host name as sent in the CHAP challenge.
- The challenge string as sent in the CHAP challenge.
- The locally defined
authname.
Two lines of output are expected:
- The
authnameto be sent with the CHAP response. - The
authkey, which is encrypted with the challenge and request id, the answer being sent in the CHAP response packet.
When configuring ppp in this manner, it is expected that the host challenge is a series of ASCII digits or characters. An encryption device or Secure ID card is usually required to calculate the secret appropriate for the given challenge. math is math 🧮
set authname id— sets the authentication id used in client mode PAP or CHAP negotiation.
If used in -direct mode with CHAP enabled, id is used in the initial authentication challenge and should normally be set to the local machine name. 🪪
set autoload min-percent max-percent period— these settings apply only in multi-link mode and default to zero, zero and five respectively. When more than one demand-dial (also known as-auto) mode link is available, only the first link is made active when ppp first reads data from the tun device. The next demand-dial link will be opened only when the current bundle throughput is at least max-percent percent of the total bundle bandwidth for period seconds. When the current bundle throughput decreases to min-percent percent or less of the total bundle bandwidth for period seconds, a demand-dial link will be brought down — as long as it's not the last active link.
Bundle throughput is measured as the maximum of inbound and outbound traffic. 📈
The default values cause demand-dial links to simply come up one at a time. Chill, orderly, no chaos.
Certain devices cannot determine their physical bandwidth, so it's sometimes necessary to use theset bandwidthcommand (described below) to makeset autoloadwork correctly. iykyk 🦋
set bandwidth value— sets the connection bandwidth in bits per second. value must be greater than zero. It is currently only used by theset autoloadcommand above. 🚀
💅 set callback option... 💅
Okay so callback is a whole vibe. If no arguments are given, callback is disabled, otherwise, ppp will request (or in -direct mode, will accept) one of the given options. In client mode, if an option is NAK'd ppp will request a different option, until no options remain at which point ppp will terminate negotiations (unless “none” is one of the specified option). In server mode, ppp will accept any of the given protocols - but the client must request one of them. If you wish callback to be optional, you must {include} none as an option.
The options are as follows (in this order of preference):
auth— The callee is expected to decide the callback number based on authentication. If ppp is the callee, the number should be specified as the fifth field of the peers entry in/etc/ppp/ppp.secret.cbcp— Microsoft's callback control protocol is used. See “set cbcp” below. If you wish to negotiate cbcp in client mode but also wish to allow the server to request no callback at CBCP negotiation time, you must specify bothcbcpandnoneas callback options.E.164 *|number[,number]...— The caller specifies the number. If ppp is the callee, number should be either a comma separated list of allowable numbers or a “*”, meaning any number is permitted. If ppp is the caller, only a single number should be specified.
⚠️ Note, this option is very unsafe when used with a “*” as a malicious caller can tell ppp to call any (possibly international) number without first authenticating themselves.
none— If the peer does not wish to do callback at all, ppp will accept the fact and continue without callback rather than terminating the connection. This is required (in addition to one or more other callback options) if you wish callback to be optional.
🌸 set cbcp [*|number[,number...] [delay [retry]]] 🌸
If no arguments are given, CBCP (Microsoft's CallBack Control Protocol) is disabled - ie, configuring CBCP in the “set callback” command will result in ppp requesting no callback in the CBCP phase. Otherwise, ppp attempts to use the given phone number(s).
In server mode (-direct), ppp will insist that the client uses one of these numbers, unless “*” is used in which case the client is expected to specify the number.
In client mode, ppp will attempt to use one of the given numbers (whichever it finds to be agreeable with the peer), or if “*” is specified, ppp will expect the peer to specify the number.
🦋 set cd [off|seconds[!]] 🦋
Normally, ppp checks for the existence of carrier depending on the type of device that has been opened:
- Terminal Devices — Carrier is checked one second after the login script is complete. If it is not set, ppp assumes that this is because the device does not support carrier (which is true for most “laplink” NULL-modem cables), logs the fact and stops checking for carrier.
As ptys do not support the TIOCMGET ioctl, the tty device will switch all carrier detection off when it detects that the device is a pty.
- PPPoE (netgraph) Devices — Carrier is checked once per second for 5 seconds. If it is not set after the fifth second, the connection attempt is considered to have failed and the device is closed. Carrier is always required for PPPoE devices.
All other device types do not support carrier. Setting a carrier value will result in a warning when the device is opened.
Some modems take more than one second after connecting to assert the carrier signal. If this delay is not increased, this will result in ppp's inability to detect when the link is dropped, as ppp assumes that the device is not asserting carrier.
The “set cd” command overrides the default carrier behaviour. seconds specifies the maximum number of seconds that ppp should wait after the dial script has finished before deciding if carrier is available or not.
If “off” is specified, ppp will not check for carrier on the device, otherwise ppp will not proceed to the login script until either carrier is detected or until seconds has elapsed, at which point ppp assumes that the device will not set carrier.
If no arguments are given, carrier settings will go back to their default values.
If seconds is followed immediately by an exclamation mark (“!”), ppp will require carrier. If carrier is not detected after seconds seconds, the link will be disconnected.
💖 set choked [timeout] 💖
This sets the number of seconds that ppp will keep a choked output queue before dropping all pending output packets. If timeout is less than or equal to zero or if timeout is not specified, it is set to the default value of 120 seconds.
A choked output queue occurs when ppp has read a certain number of packets from the local network for transmission, but cannot send the data due to link failure (the peer is busy etc.). ppp will not read packets indefinitely. Instead, it reads up to 30 packets (or 30 + nlinks * 2 packets in multi-link mode), then stops reading the network interface until either timeout seconds have passed or at least one packet has been sent.
If timeout seconds pass, all pending output packets are dropped.
✨ set ctsrts|crtscts on|off ✨
This sets hardware flow control. Hardware flow control is on by default.
🎀 set deflate out-winsize [in-winsize] 🎀
This sets the DEFLATE algorithms default outgoing and incoming window sizes. Both out-winsize and in-winsize must be values between 8 and 15. If in-winsize is specified, ppp will insist that this window size is used and will not accept any other values from the peer.
🌈 set dns [primary [secondary]] 🌈
This command specifies DNS overrides for the “accept dns” command. Refer to the “accept” command description above for details. This command does not affect the IP numbers requested using “enable dns”.
🫶 set device|line value... 🫶
This sets the device(s) to which ppp will talk to the given “value”.
All serial device names are expected to begin with /dev/. Serial devices are usually called cuaXX.
If “value” does not begin with /dev/, it must either begin with an exclamation mark (“!”), be of the format PPPoE:iface[:provider] (on netgraph(4) enabled systems), or be of the format host:port[/tcp|udp].
If it begins with an exclamation mark, the rest of the device name is treated as a program name, and that program is executed when the device is opened. Standard input, output and error are fed back to ppp and are read and written as if they were a regular device.
If a PPPoE:iface[:provider] specification is given, ppp will attempt to create a PPP over Ethernet connection using the given iface interface by using netgraph(4). If netgraph(4) is not available, ppp will attempt to load it using kldload(2). If this fails, an external program must be used such as the pppoed(8) program available under OpenBSD. The given provider is passed as the service name in the PPPoE Discovery Initiation (PADI) packet. If no provider is given, an empty value will be used.
When a PPPoE connection is established, ppp will place the name of the Access Concentrator in the environment variable ACNAME.
Refer to netgraph(4) and ng_pppoe(4) for further details.
If a host:port[/tcp|udp] specification is given, ppp will attempt to connect to the given host on the given port. If a “/tcp” or “/udp” suffix is not provided, the default is “/tcp”. Refer to the section on PPP OVER TCP and UDP above for further details.
If multiple “values” are specified, ppp will attempt to open each one in turn until it succeeds or runs out of devices.
🧚 set dial chat-script 🧚
This specifies the chat script that will be used to dial the other side. See also the “set login” command below. Refer to chat(8) and to the example configuration files for details of the chat script format. It is possible to specify some special ‘values’ in your chat script as follows:
\c— When used as the last character in a ‘send’ string, this indicates that a newline should not be appended.\d— When the chat script encounters this sequence, it delays two seconds.\p— When the chat script encounters this sequence, it delays for one quarter of a second.\n— This is replaced with a newline character.\r— This is replaced with a carriage return character.\s— This is replaced with a space character.\t— This is replaced with a tab character.\T— This is replaced by the current phone number (see “set phone” below).\P— This is replaced by the current authkey value (see “set authkey” above).\U— This is replaced by the current authname value (see “set authname” above).
Note that two parsers will examine these escape sequences, so in order to have the ‘chat parser’ see the escape character, it is necessary to escape it from the ‘command parser’. This means that in practice you should use two escapes, for example:
set dial "... ATDT\\T CONNECT"
okay so you can also run external commands straight from the chat script and honestly? that's such a serve. 💅 The way it works: the first character of the expect or send string is an exclamation mark (!). Need a literal exclamation mark? Double it up to !! and it gets treated as a single literal !. Iconic.
When the command runs, standard input and standard output are directed to the open device (see the set device command), and standard error is read by ppp and substituted as the expect or send string. And if ppp is running in interactive mode, file descriptor 3 is attached to /dev/tty. 🎀
For example (wrapped for readability):
set login "TIMEOUT 5 \"\" \"\" login:--login: ppp \
word: ppp \"!sh \\-c \\\"echo \\-n label: >&2\\\"\" \
\"!/bin/echo in\" HELLO"
would result in the following chat sequence (output using the set log local chat command before dialing):
Dial attempt 1 of 1
dial OK!
Chat: Expecting:
Chat: Sending:
Chat: Expecting: login:--login:
Chat: Wait for (5): login:
Chat: Sending: ppp
Chat: Expecting: word:
Chat: Wait for (5): word:
Chat: Sending: ppp
Chat: Expecting: !sh \-c "echo \-n label: >&2"
Chat: Exec: sh -c "echo -n label: >&2"
Chat: Wait for (5): !sh \-c "echo \-n label: >&2" --> label:
Chat: Exec: /bin/echo in
Chat: Sending:
Chat: Expecting: HELLO
Chat: Wait for (5): HELLO
login OK!
Note (again) the use of the escape character, allowing many levels of nesting. Here, there are four parsers at work, bestie, four of them 😭:
- The first parses the original line, reading it as three arguments.
- The second parses the third argument, reading it as 11 arguments. At this point it is important that the
-signs are escaped, otherwise this parser will see them as constituting an expect-send-expect sequence. - When the
!character is seen, the execution parser reads the first command as three arguments, and then sh(1) itself expands the argument after the-c. - As we wish to send the output back to the modem: in the first example we redirect our output to file descriptor 2 (stderr) so that ppp itself sends and logs it, and in the second example, we just output to stdout, which is attached directly to the modem.
This, of course means that it is possible to execute an entirely external “chat” command rather than using the internal one. See chat(8) for a good alternative.
The external command that is executed is subjected to the same special word expansions as the !bg command. ✨
set enddisc [label|IP|MAC|magic|psn value]
This command sets our local endpoint discriminator. If it's set prior to LCP negotiation, and if no disable enddisc command has been used, ppp will send the info to the peer using the LCP endpoint discriminator option. The following discriminators may be set:
label— the current label is used. 🏷️IP— our local IP number is used. Since LCP is negotiated prior to IPCP, it's possible that the IPCP layer will subsequently change this value. If it does, the endpoint discriminator stays at the old value unless manually reset. 🙈MAC— similar to theIPoption above, except that the MAC address associated with the local IP number is used. If the local IP number is not resident on any Ethernet interface, the command will fail. 💀 As the local IP number defaults to whatever the machine host name is,set enddisc macis usually done prior to anyset ifaddrcommands.magic— a 20 digit random number is used. Care should be taken when using magic numbers, because restarting ppp or creating a link using a different ppp invocation will also use a different magic number and will therefore not be recognised by the peer as belonging to the same bundle. This makes it unsuitable for-directconnections. 🎲psnvalue — the given value is used. Value should be set to an absolute public switched network number with the country code first.
If no arguments are given, the endpoint discriminator is reset. 🫶
set escape value...
This option is similar to the set accmap option above. It allows the user to specify a set of characters that will be ‘escaped’ as they travel across the link. 🦋
set filter
set filter dial|alive|in|out rule-no permit|deny|clear|rule-no [!]
[[host] src_addr[/width] [dst_addr[/width]]] [proto [src
lt|eq|gt port] [dst lt|eq|gt port] [estab] [syn] [finrst]
[timeout secs]]
ppp supports four filter sets, and they each have main character energy:
- The alive filter specifies packets that keep the connection alive — resetting the idle timer. ⏰
- The dial filter specifies packets that cause ppp to dial when in
-automode. 📞 - The in filter specifies packets that are allowed to travel into the machine. 📥
- The out filter specifies packets that are allowed out of the machine. 📤
Filtering is done prior to any IP alterations that might be done by the NAT engine on outgoing packets and after any IP alterations that might be done by the NAT engine on incoming packets. By default all empty filter sets allow all packets to pass. Rules are processed in order according to rule-no (unless skipped by specifying a rule number as the action). Up to 40 rules may be given for each set. 🎯
If a packet does not match any of the rules in a given set, it is discarded. In the case of in and out filters, this means that the packet is dropped. In the case of alive filters it means that the packet will not reset the idle timer (even if the in/out filter has a timeout value) and in the case of dial filters it means that the packet will not trigger a dial. A packet failing to trigger a dial will be dropped rather than queued. Refer to the section on “PACKET FILTERING” above for further details. 😌
set hangup chat-script
This specifies the chat script that will be used to reset the device before it is closed. It should not normally be necessary, but can be used for devices that fail to reset themselves properly on close. 🔌
set help|? [command]
This command gives a summary of available set commands, or if command is specified, the command usage is shown. 🧚
set ifaddr [myaddr[/nn] [hisaddr[/nn] [netmask [triggeraddr]]]]
This command specifies the IP addresses that will be used during IPCP negotiation. Addresses are specified using the format
a.b.c.d/nn
Where “a.b.c.d” is the preferred IP, but nn specifies how many bits of the address we will insist on. If /nn is omitted, it defaults to /32 unless the IP address is 0.0.0.0 in which case it defaults to /0. 💅
If you wish to assign a dynamic IP number to the peer, hisaddr may also be specified as a range of IP numbers in the format
IP[-IP][,IP[-IP]]...
for example:
set ifaddr 10.0.0.1 10.0.1.2-10.0.1.10,10.0.1.20
will only negotiate 10.0.0.1 as the local IP number, but may assign any of the given 10 IP numbers to the peer. If the peer requests one of these numbers, and that number is not already in use, ppp will grant the peer's request. This is useful if the peer wants to re-establish a link using the same IP number as was previously allocated (thus maintaining any existing tcp or udp connections). 🔥
If the peer requests an IP number that is either outside of this range or is already in use, ppp will suggest a random unused IP number from the range.
If triggeraddr is specified, it is used in place of myaddr in the initial IPCP negotiation. However, only an address in the myaddr range will be accepted. This is useful when negotiating with some PPP implementations that will not assign an IP number unless their peer requests 0.0.0.0. 😭
It should be noted that in-automode, ppp will configure the interface immediately upon reading theset ifaddrline in the config file. In any other mode, these values are just used for IPCP negotiations, and the interface is not configured until the IPCP layer is up.
Note that the HISADDR argument may be overridden by the third field in the ppp.secret file once the client has authenticated itself (if PAP or CHAP are enabled). Refer to the “AUTHENTICATING INCOMING CONNECTIONS” section for details. 🔐
In all cases, if the interface is already configured, ppp will try to maintain the interface IP numbers so that any existing bound sockets will remain valid. 🫶
set ifqueue packets
Set the maximum number of packets that ppp will read from the tunnel interface while data cannot be sent to any of the available links. This queue limit is necessary to flow control outgoing data as the tunnel interface is likely to be far faster than the combined links available to ppp. 🚀
If packets is set to a value less than the number of links, ppp will read up to that value regardless. This prevents any possible latency problems.
The default value for packets is 30. 🌸
retry timers: set ccpretry and friends
set ccpretry|ccpretries [timeout [reqtries [trmtries]]]
set chapretry|chapretries [timeout [reqtries]]
set ipcpretry|ipcpretries [timeout [reqtries [trmtries]]]
set ipv6cpretry|ipv6cpretries [timeout [reqtries [trmtries]]]
set lcpretry|lcpretries [timeout [reqtries [trmtries]]]
set papretry|papretries [timeout [reqtries]]— okay so these two set how many secondspppwaits before it goes "hey?? still there??" and resends its Finite State Machine (FSM) Request packets 🫶 The default timeout for all FSMs is 3 seconds (which should suffice in most cases, fr).- If reqtries is specified, it tells
ppphow many configuration request attempts it should make while receiving no reply from the peer before giving up. The default is 5 attempts for CCP, LCP and IPCP and 3 attempts for PAP and CHAP. - If trmtries is specified, it tells
ppphow many terminate requests should be sent before giving up waiting for the peers response. The default is 3 attempts. Authentication protocols are not terminated and it is therefore invalid to specify trmtries for PAP or CHAP 💀 - In order to avoid negotiations with the peer that will never converge,
pppwill only send at most 3 times the configured number of reqtries in any given negotiation session before giving up and closing that layer.
- If reqtries is specified, it tells
set log [local] [+|-]value...— this one lets you adjust the current log level ✨ Refer to the Logging Facility section for further details (it's a whole vibe, go look).set login chat-script— this chat-script compliments the dial-script, like the perfect little duo 🎀 If both are specified, the login script will be executed after the dial script. Escape sequences available in the dial script are also available here.set logout chat-script— specifies the chat script that will be used to logout before the hangup script is called. It should not normally be necessary, ngl.set lqrperiod|echoperiod frequency— sets the frequency in seconds at which LQR or LCP ECHO packets are sent 🦋 The default is 30 seconds. You must also use the “enable lqr” and/or “enable echo” commands if you wish to send LQR or LCP ECHO requests to the peer.set mode interactive|auto|ddial|background— this command allows you to change the ‘mode’ of the specified link 👑 This is normally only useful in multi-link mode, but may also be used in uni-link mode.- It is not possible to change a link that is ‘direct’ or ‘dedicated’ 🙈
- Note: If you issue the command “set mode auto”, and have network address translation enabled, it may be useful to “enable iface-alias” afterwards. This will allow
pppto do the necessary address translations to enable the process that triggers the connection to connect once the link is up despite the peer assigning us a new (dynamic) IP address.
set mppe [40|56|128|* [stateless|stateful|*]]— this option selects the encryption parameters used when negotiation MPPE 🔥 MPPE can be disabled entirely with the “disable mppe” command. If no arguments are given,pppwill attempt to negotiate a stateful link with a 128 bit key, but will agree to whatever the peer requests (including no encryption at all — bold of it, honestly).- If any arguments are given,
pppwill insist on using MPPE and will close the link if it is rejected by the peer (Note; this behaviour can be overridden by a configured RADIUS server). - The first argument specifies the number of bits that
pppshould insist on during negotiations and the second specifies whetherpppshould insist on stateful or stateless mode. - In stateless mode, the encryption dictionary is re-initialised with every packet according to an encryption key that is changed with every packet.
- In stateful mode, the encryption dictionary is re-initialised every 256 packets or after the loss of any data and the key is changed every 256 packets.
- Stateless mode is less efficient but is better for unreliable transport layers 💅
- If any arguments are given,
set mrru [value]— setting this option enables Multi-link PPP negotiations, also known as Multi-link Protocol or MP 🌈 There is no default MRRU (Maximum Reconstructed Receive Unit) value. If no argument is given, multi-link mode is disabled.set mru [max[imum]] [value]— the default MRU (Maximum Receive Unit) is 1500. If it is increased, the other side may increase its MTU. In theory there is no point in decreasing the MRU to below the default as the PPP protocol says implementations must be able to accept packets of at least 1500 octets.- If the “maximum” keyword is used,
pppwill refuse to negotiate a higher value. The maximum MRU can be set to 2048 at most. Setting a maximum of less than 1500 violates the PPP rfc, but may sometimes be necessary 😭 For example, PPPoE imposes a maximum of 1492 due to hardware limitations. - If no argument is given, 1500 is assumed. A value must be given when “maximum” is specified.
- If the “maximum” keyword is used,
set mtu [max[imum]] [value]— the default MTU is 1500 🦋 At negotiation time,pppwill accept whatever MRU the peer requests (assuming it is not less than 296 bytes or greater than the assigned maximum). If the MTU is set,pppwill not accept MRU values less than value. When negotiations are complete, the MTU is used when writing to the interface, even if the peer requested a higher value MRU. This can be useful for limiting your packet size (giving better bandwidth sharing at the expense of more header data).- If the “maximum” keyword is used,
pppwill refuse to negotiate a higher value. The maximum MTU can be set to 2048 at most. - Note, it is necessary to use the “maximum” keyword to limit the MTU when using PPPoE 👀
- If no value is given, 1500, or whatever the peer asks for is used. A value must be given when “maximum” is specified.
- If the “maximum” keyword is used,
set nbns [x.x.x.x [y.y.y.y]]— this option allows the setting of the Microsoft NetBIOS name server values to be returned at the peers request ✨ If no values are given,pppwill reject any such requests.set openmode active|passive [delay]— by default, openmode is always active with a one second delay 🎀 That is,pppwill always initiate LCP/IPCP/CCP negotiation one second after the line comes up. If you want to wait for the peer to initiate negotiations, you can use the value passive. If you want to initiate negotiations immediately or after more than one second, the appropriate delay may be specified here in seconds.set parity odd|even|none|mark— this allows the line parity to be set 💜 The default value is none.set phone telno[|backupnumber]...[:nextnumber]...— this allows the specification of the phone number to be used in place of the\Tstring in the dial and login chat scripts ☎️ Multiple phone numbers may be given separated either by a pipe (“|”) or a colon (“:”).- Numbers after the pipe are only dialed if the dial or login script for the previous number failed.
- Numbers after the colon are tried sequentially, irrespective of the reason the line was dropped.
- If multiple numbers are given,
pppwill dial them according to these rules until a connection is made, retrying the maximum number of times specified by “set redial” below. In-backgroundmode, each number is attempted at most once.
set pppoe [standard|3Com]— this option configures the underlyingng_pppoe(4)node to either standard RFC2516 PPPoE or proprietary 3Com mode 🌸 If not set the system default will be used.set [proc]title [value]— the current process title as displayed byps(1)is changed according to value ⭐ If value is not specified, the original process title is restored. All the word replacements done by the shell commands (see the “bg” command above) are done here too.
Note, ifUSERis required in the process title, the “set proctitle” command must appear inppp.linkup, as it is not known when the commands inppp.confare executed 💅
set radius [config-file]— this command enables RADIUS support (if it is compiled in) 🔥 config-file refers to the radius client configuration file as described inradius.conf(5). If PAP, CHAP, MSCHAP or MSCHAPv2 are “enabled”,pppbehaves as a Network Access Server and uses the configured RADIUS server to authenticate rather than authenticating from theppp.secretfile or from the passwd database.- If none of PAP, CHAP, MSCHAP or MSCHAPv2 are enabled, “set radius” will do nothing.
ppp uses the following attributes from the RADIUS reply 👑
RAD_FRAMED_IP_ADDRESS— the peer IP address is set to the given value.RAD_FRAMED_IP_NETMASK— thetuninterface netmask is set to the given value.RAD_FRAMED_MTU— if the given MTU is less than the peers MRU as agreed during LCP negotiation, and it is less that any configured MTU (see the “set mru” command), thetuninterface MTU is set to the given value.RAD_FRAMED_COMPRESSION— if the received compression type is “1”,pppwill request VJ compression during IPCP negotiations despite any “disable vj” configuration command.RAD_FILTER_ID— if this attribute is supplied,pppwill attempt to use it as an additional label to load from theppp.linkupandppp.linkdownfiles 🦋 The load will be attempted before (and in addition to) the normal label search. If the label does not exist, no action is taken andpppproceeds to the normal load using the current label.RAD_FRAMED_ROUTE— the received string is expected to be in the formatdest[/bits] gw [metrics]. Any specified metrics are ignored.MYADDRandHISADDRare understood as valid values for dest and gw, “default” can be used for dest to specify the default route, and “0.0.0.0” is understood to be the same as “default” for dest andHISADDRfor gw ✨
Okay so like, example time bestie 🍓 — a returned value of 1.2.3.4/24 0.0.0.0 1 2 -1 3 400 would result in a routing table entry to the 1.2.3.0/24 network via HISADDR, and a returned value of 0.0.0.0 0.0.0.0 or default HISADDR would result in a default route to HISADDR.
All RADIUS routes are applied after any sticky routes are applied, making RADIUS routes override configured routes. This also applies for RADIUS routes that do not {include} the MYADDR or HISADDR keywords. Periodt. 💅
RAD_FRAMED_IPV6_PREFIX
If this attribute is supplied, the value is substituted for IPV6PREFIX in a command. You may pass it to an upper layer protocol such as DHCPv6 for delegating an IPv6 prefix to a peer. 🦋
RAD_FRAMED_IPV6_ROUTE
The received string is expected to be in the format dest[/bits] gw [metrics]. Any specified metrics are ignored. MYADDR6 and HISADDR6 are understood as valid values for dest and gw, default can be used for dest to specify the default route, and :: is understood to be the same as default for dest and HISADDR6 for gw.
For example, a returned value of 3ffe:505:abcd::/48 :: would result in a routing table entry to the 3ffe:505:abcd::/48 network via HISADDR6, and a returned value of :: :: or default HISADDR6 would result in a default route to HISADDR6.
All RADIUS IPv6 routes are applied after any sticky routes are applied, making RADIUS IPv6 routes override configured routes. This also applies for RADIUS IPv6 routes that do not {include} the MYADDR6 or HISADDR6 keywords. no cap 🫶
RAD_SESSION_TIMEOUT
If supplied, the client connection is closed after the given number of seconds. bye bestie 👋
RAD_REPLY_MESSAGE
If supplied, this message is passed back to the peer as the authentication SUCCESS text.
RAD_MICROSOFT_MS_CHAP_ERROR
If this RAD_VENDOR_MICROSOFT vendor specific attribute is supplied, it is passed back to the peer as the authentication FAILURE text. 😭
RAD_MICROSOFT_MS_CHAP2_SUCCESS
If this RAD_VENDOR_MICROSOFT vendor specific attribute is supplied and if MS-CHAPv2 authentication is being used, it is passed back to the peer as the authentication SUCCESS text. ✨
RAD_MICROSOFT_MS_MPPE_ENCRYPTION_POLICY
If this RAD_VENDOR_MICROSOFT vendor specific attribute is supplied and has a value of 2 (Required), ppp will insist that MPPE encryption is used (even if no set mppe configuration command has been given with arguments). If it is supplied with a value of 1 (Allowed), encryption is made optional (despite any set mppe configuration commands with arguments).
RAD_MICROSOFT_MS_MPPE_ENCRYPTION_TYPES
If this RAD_VENDOR_MICROSOFT vendor specific attribute is supplied, bits 1 and 2 are examined. If either or both are set, 40 bit and/or 128 bit (respectively) encryption options are set, overriding any given first argument to the set mppe command. Note, it is not currently possible for the RADIUS server to specify 56 bit encryption.
RAD_MICROSOFT_MS_MPPE_RECV_KEY
If this RAD_VENDOR_MICROSOFT vendor specific attribute is supplied, its value is used as the master key for decryption of incoming data. When clients are authenticated using MSCHAPv2, the RADIUS server MUST provide this attribute if inbound MPPE is to function. 🔑
RAD_MICROSOFT_MS_MPPE_SEND_KEY
If this RAD_VENDOR_MICROSOFT vendor specific attribute is supplied, its value is used as the master key for encryption of outgoing data. When clients are authenticated using MSCHAPv2, the RADIUS server MUST provide this attribute if outbound MPPE is to function. 🔑
Values received from the RADIUS server may be viewed using show bundle. bestie that's your receipts 🧾✨
set rad_alive timeout
When RADIUS is configured, setting rad_alive to a non-zero timeout value will tell ppp to sent RADIUS accounting information to the RADIUS server every timeout seconds. it's giving "keeping the server in the loop" energy 💖
set rad_port_id option
When RADIUS is configured, setting the rad_port_id value specifies what should be sent to the RADIUS server as NAS-Port-Id. The options are as follows:
pid— PID of the corresponding tunnel.tunnum—tun(4)interface number.ifnum— index of the interface as returned byif_nametoindex(3).default— keeps the default behavior.
set reconnect timeout ntries
Should the line drop unexpectedly (due to loss of CD or LQR failure), a connection will be re-established after the given timeout. The line will be re-connected at most ntries times. Ntries defaults to zero. A value of random for timeout will result in a variable pause, somewhere between 1 and 30 seconds. 🎲
set recvpipe [value]
This sets the routing table RECVPIPE value. The optimum value is just over twice the MTU value. If value is unspecified or zero, the default kernel controlled value is used. 🧚
set redial secs[+inc[-max]][.next] [attempts]
ppp can be instructed to attempt to redial attempts times. If more than one phone number is specified (see set phone above), a pause of next is taken before dialing each number. A pause of secs is taken before starting at the first number again. A literal value of random may be used here in place of secs and next, causing a random delay of between 1 and 30 seconds.
If inc is specified, its value is added onto secs each time ppp tries a new number. secs will only be incremented at most max times. max defaults to 10.
Note, the secs delay will be effective, even after attempts has been exceeded, so an immediate manual dial may appear to have done nothing. If an immediate dial is required, a!should immediately follow theopenkeyword. See theopendescription above for further details. 😤
set sendpipe [value]
This sets the routing table SENDPIPE value. The optimum value is just over twice the MTU value. If value is unspecified or zero, the default kernel controlled value is used.
set server|socket TcpPort|LocalName|none|open|closed [password [mask]]
This command tells ppp to listen on the given socket or 'diagnostic port' for incoming command connections.
The word none instructs ppp to close any existing socket and clear the socket configuration. The word open instructs ppp to attempt to re-open the port. The word closed instructs ppp to close the open port.
If you wish to specify a local domain socket, LocalName must be specified as an absolute file name, otherwise it is assumed to be the name or number of a TCP port. You may specify the octal umask to be used with a local domain socket. Refer to umask(2) for umask details. Refer to services(5) for details of how to translate TCP port names.
You must also specify the password that must be entered by the client (using the passwd variable above) when connecting to this socket. If the password is specified as an empty string, no password is required for connecting clients. 🙈
When specifying a local domain socket, the first %d sequence found in the socket name will be replaced with the current interface unit number. This is useful when you wish to use the same profile for more than one connection. lowkey genius ✨
In a similar manner TCP sockets may be prefixed with the + character, in which case the current interface unit number is added to the port number.
When using ppp with a server socket, the pppctl(8) command is the preferred mechanism of communications. Currently, telnet(1) can also be used, but link encryption may be implemented in the future, so telnet(1) should be avoided.
Note;SIGUSR1andSIGUSR2interact with the diagnostic socket. 👑
set speed value
This sets the speed of the serial device. If speed is specified as sync, ppp treats the device as a synchronous device.
Certain device types will know whether they should be specified as synchronous or asynchronous. These devices will override incorrect settings and log a warning to this effect. the device said "i know who i am" 💅
set stopped [LCPseconds [CCPseconds]]
If this option is set, ppp will time out after the given FSM (Finite State Machine) has been in the stopped state for the given number of seconds. This option may be useful if the peer sends a terminate request, but never actually closes the connection despite our sending a terminate acknowledgement. This is also useful if you wish to set openmode passive and time out if the peer does not send a Configure Request within the given time. Use set log +lcp +ccp to make ppp log the appropriate state transitions. 🌈
The default value is zero, where ppp does not time out in the stopped state.
This value should not be set to less than the openmode delay (see set openmode above). 💀
set timeout idleseconds [mintimeout]
This command allows the setting of the idle timer. Refer to the section titled "SETTING THE IDLE TIMER" for further details.
If mintimeout is specified, ppp will never idle out before the link has been up for at least that number of seconds. protective bestie vibes 🫶
okay bestie, we’re still deep in the command list — no stress, here’s the rest, and yes it’s giving “Unix but make it cute” 💅
set urgent [tcp|udp|none] [[+|-]port] ...— this one controls which portspppprioritizes when it’s transmitting data. The default priority TCP ports are21(ftp control),22(ssh),23(telnet),513(login),514(shell),543(klogin) and544(kshell). There are no priority UDP ports by default. Seeservices(5)for details.
If neither tcp nor udp is specified, tcp is assumed. If no ports are given, the priority port lists are cleared (although if tcp or udp is specified, only that list is cleared). If the first port argument is prefixed with a plus (+) or a minus (-), the current list is adjusted; otherwise the list is reassigned. Ports prefixed with a plus or not prefixed at all are added to the list, and ports prefixed with a minus are removed from the list.
If none is specified, all priority port lists are disabled and even IPTOS_LOWDELAY packets are not prioritised. iconic behavior, honestly ✨
set urgent length length— tellspppto prioritize small packets up tolengthbytes. Iflengthis not specified, or is0, this feature is disabled. 🫶set vj slotcomp on|off— tellspppwhether it should attempt to negotiate VJ slot compression. By default, slot compression is turned on. slay 💅set vj slots nslots— sets the initial number of slots thatpppwill try to negotiate with the peer when VJ compression is enabled (see theenablecommand above). It defaults to a value of16.Nslotsmust be between4and16inclusive. no cap, that range is locked in 🔒shell|! [command]— ifcommandis not specified, a shell is invoked according to theSHELLenvironment variable. Otherwise, the given command is executed. Word replacement is done in the same way as for the!bgcommand as described above.
Use of the ! character requires a following space as with any of the other commands. You should note that this command is executed in the foreground; ppp will not continue running until this process has exited. Use the bg command if you wish processing to happen in the background. foreground = main character energy, background = side quest mode 😌
show var— this command lets you examine the following, bestie:show bundle— show the current bundle settings.show ccp— show the current CCP compression statistics.show compress— show the current VJ compression statistics.show escape— show the current escape characters.show filter [name]— list the current rules for the given filter. Ifnameis not specified, all filters are shown.show hdlc— show the current HDLC statistics.show help|?— give a summary of availableshowcommands.show iface— show the current interface information (the same asiface show).show ipcp— show the current IPCP statistics.show layers— show the protocol layers currently in use.show lcp— show the current LCP statistics.show [data]link— show high level link information.show links— show a list of available logical links.show log— show the current log values.show mem— show current memory statistics.show ncp— show the current NCP statistics.show physical— show low level link information.show mp— show Multi-link information.show proto— show current protocol totals.show route— show the current routing tables.show stopped— show the current stopped timeouts.show timer— show the active alarm timers.show version— show the current version number ofppp.
term— go into terminal mode. Characters typed at the keyboard are sent to the device. Characters read from the device are displayed on the screen. When a remote PPP peer is detected,pppautomatically enables Packet Mode and goes back into command mode. teleportation but for your keyboard, kinda ⌨️✨
✨ MORE DETAILS ✨
- Read the example configuration files. They are a good source of information. fr fr, go read them 📚
- Use
help,nat ?,enable ?,set ?andshow ?to get online information about what is available. the question marks are literally your besties here 💜 - The following URL contains useful information:
🎀 FILES 🎀
ppp refers to four files: ppp.conf, ppp.linkup, ppp.linkdown and ppp.secret. These files are placed in the /etc/ppp directory. four little files carrying the whole vibe 🎀
/etc/ppp/ppp.conf— system default configuration file./etc/ppp/ppp.secret— an authorisation file for each system./etc/ppp/ppp.linkup— a file to check whenpppestablishes a network level connection./etc/ppp/ppp.linkdown— a file to check whenpppcloses a network level connection./var/log/ppp.log— logging and debugging information file. Note, this name is specified in/etc/syslog.conf. Seesyslog.conf(5)for further details./var/spool/lock/LCK..*— tty port locking file. Refer touucplock(3)for further details./var/run/tunN.pid— the process id (pid) of thepppprogram connected to thetunNdevice, whereNis the number of the device./var/run/ttyXX.if— the tun interface used by this port. Again, this file is only created in-background,-autoand-ddialmodes./etc/services— get port number if port number is using service name./var/run/ppp-authname-class-value— in multi-link mode, local domain sockets are created using the peer authentication name (authname), the peer endpoint discriminator class (class) and the peer endpoint discriminator value (value). As the endpoint discriminator value may be a binary value, it is turned to HEX to determine the actual file name.
This socket is used to pass links between different instances of ppp. friendship bracelet energy, but for sockets 🫶
🦋 SEE ALSO 🦋
at(1), ftp(1), gzip(1), hostname(1), login(1), tcpdump(1), telnet(1), kldload(2), pipe(2), socketpair(2), libalias(3), libradius(3), syslog(3), uucplock(3), netgraph(4), ng_pppoe(4), crontab(5), group(5), passwd(5), protocols(5), radius.conf(5), resolv.conf(5), syslog.conf(5), adduser(8), chat(8), getty(8), inetd(8), init(8), ping(8), pppctl(8), pppoed(8), route(8), sshd(8), syslogd(8), traceroute(8), vipw(8). the whole extended friend group, honestly 🌈
💖 HISTORY 💖
This program was originally written by Toshiharu OHNO <tony-o@iij.ad.jp>, and was submitted to FreeBSD 2.0.5 by Atsushi Murai <amurai@spec.co.jp>. legends, actual legends 👑
It was substantially modified during 1997 by Brian Somers <brian@Awfulhak.org>, and was ported to OpenBSD in November that year (just after the 2.2 release). November glow-up era ✨
Most of the code was rewritten by Brian Somers in early 1998 when multi-link ppp support was added. early 1998 said “new code, who dis” and honestly? iconic 💅
source/version footer vibe check: this page is from Debian, it’s PPP(8), and it’s dated December 6, 2024. Byeee bestie, go configure something beautiful 🫶💖🎀
📦 where this page comes from
- freebsd 15.1: base 15.1
- Copyright (c) 2001 Brian Somers <brian@Awfulhak.org>
- 💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on : a language model's rewrite of the original, under its terms