Pcap(3)

📦
version 0.21 · 12 versions
, in opensuse-leap 16.0

💖 NAME 💖

okay so bestie, this is Pcap(3), and the actual main character is Net::Pcap — interface to the pcap(3) LBL packet capture library. That's the whole name, slay. 💅

✨ VERSION ✨

Version 0.21 — iconic, periodt. 🎀

🦋 SYNOPSIS 🦋

here's the group-chat demo, exactly:

use Net::Pcap;

my $err = '';
my $dev = pcap_lookupdev(\$err);  # find a device

# open the device for live listening
my $pcap = pcap_open_live($dev, 1024, 1, 0, \$err);

# loop over next 10 packets
pcap_loop($pcap, 10, \&process_packet, "just for the demo");

# close the device
pcap_close($pcap);

sub process_packet {
    my ($user_data, $header, $packet) = @_;
    # do something ...
}

🌈 DESCRIPTION 🌈

Net::Pcap is literally a Perl binding to the LBL pcap(3) library and its Win32 counterpart, the WinPcap library. Pcap (packet capture) is a portable API to capture network packet: it lets applications capture packets at link-layer, bypassing the normal protocol stack. It also provides features like kernel-level packet filtering and access to internal statistics. ✨

Common applications include network statistics collection, security monitoring, network debugging, etc. no cap, it's giving powerful. 👑

🌸 NOTES 🌸

💜 Signals handling 💜

Since version 5.7.3, Perl uses a mechanism called "deferred signals" to delay signals delivery until "safe" points in the interpreter. See "Deferred Signals (Safe Signals)" in perlipc for a detailed explanation.

Since Net::Pcap version 0.08, released in October 2005, the module modified the internal variable PL_signals to re-enable immediate signals delivery in Perl 5.8 and later within some XS functions (CPAN-RT #6320). However, it can create situations where the Perl interpreter is less stable and can crash (CPAN-RT #43308). Therefore, as of version 0.17, Net::Pcap no longer modifies PL_signals by itself, but provides facilities so the user has full control of how signals are delivered. 🫶

First, the pcap_perl_settings() function allows one to select how signals are handled:

pcap_perl_settings(PERL_SIGNALS_UNSAFE);
pcap_loop($pcap, 10, \&process_packet, "");
pcap_perl_settings(PERL_SIGNALS_SAFE);

Then, to easily make code interruptable, Net::Pcap provides the UNSAFE_SIGNALS pseudo-bloc:

UNSAFE_SIGNALS {
    pcap_loop($pcap, 10, \&process_packet, "");
};

(Stolen from Rafael Garcia-Suarez's Perl::Unsafe::Signals) 😭💖

🎀 EXPORTS 🎀

Net::Pcap supports the following Exporter tags:

  • :bpf — exports a few BPF related constants:
BPF_ALIGNMENT  BPF_MAJOR_VERSION  BPF_MAXBUFSIZE  BPF_MAXINSNS
BPF_MEMWORDS  BPF_MINBUFSIZE  BPF_MINOR_VERSION  BPF_RELEASE
  • :datalink — exports the data link types macros:
DLT_AIRONET_HEADER  DLT_APPLE_IP_OVER_IEEE1394  DLT_ARCNET
DLT_ARCNET_LINUX  DLT_ATM_CLIP  DLT_ATM_RFC1483  DLT_AURORA
DLT_AX25  DLT_CHAOS  DLT_CHDLC  DLT_CISCO_IOS  DLT_C_HDLC
DLT_DOCSIS  DLT_ECONET  DLT_EN10MB  DLT_EN3MB  DLT_ENC  DLT_FDDI
DLT_FRELAY  DLT_HHDLC  DLT_IBM_SN  DLT_IBM_SP  DLT_IEEE802
DLT_IEEE802_11  DLT_IEEE802_11_RADIO DLT_IEEE802_11_RADIO_AVS
DLT_IPFILTER  DLT_IP_OVER_FC  DLT_JUNIPER_ATM1 DLT_JUNIPER_ATM2
DLT_JUNIPER_ES  DLT_JUNIPER_GGSN  DLT_JUNIPER_MFR DLT_JUNIPER_MLFR
DLT_JUNIPER_MLPPP  DLT_JUNIPER_MONITOR  DLT_JUNIPER_SERVICES
DLT_LINUX_IRDA  DLT_LINUX_SLL  DLT_LOOP  DLT_LTALK  DLT_NULL
DLT_OLD_PFLOG  DLT_PCI_EXP  DLT_PFLOG  DLT_PFSYNC  DLT_PPP
DLT_PPP_BSDOS  DLT_PPP_ETHER  DLT_PPP_SERIAL  DLT_PRISM_HEADER
DLT_PRONET  DLT_RAW  DLT_RIO  DLT_SLIP  DLT_SLIP_BSDOS  DLT_SUNATM
DLT_SYMANTEC_FIREWALL  DLT_TZSP  DLT_USER0  DLT_USER1  DLT_USER2
DLT_USER3  DLT_USER4  DLT_USER5  DLT_USER6  DLT_USER7  DLT_USER8
DLT_USER9  DLT_USER10  DLT_USER11  DLT_USER12  DLT_USER13
DLT_USER14  DLT_USER15
  • :pcap — exports the following pcap constants:
PCAP_ERRBUF_SIZE    PCAP_IF_LOOPBACK
PCAP_VERSION_MAJOR  PCAP_VERSION_MINOR
  • :mode — exports the following constants:
MODE_CAPT  MODE_MON  MODE_STAT
  • :openflag — exports the following constants:
OPENFLAG_PROMISCUOUS  OPENFLAG_DATATX_UDP  OPENFLAG_NOCAPTURE_RPCAP
  • :source — exports the following constants:
PCAP_SRC_FILE  PCAP_SRC_IFLOCAL  PCAP_SRC_IFREMOTE
  • :sample — exports the following constants:
PCAP_SAMP_NOSAMP  PCAP_SAMP_1_EVERY_N  PCAP_SAMP_FIRST_AFTER_N_MS
  • :rpcap — exports the following constants:
RMTAUTH_NULL  RMTAUTH_PWD
  • :functions — short names of the functions (without the pcap_ prefix) for those which would not cause a clash with an already defined name. Namely, the following functions are not available in short form: open(), close(), next(), dump(), file(), fileno(). Using these short names is now discouraged, and may be removed in the future. 💀

By default, this module exports the symbols from the :datalink and :pcap tags, and all the functions, with the same names as the C library.

🔥 FUNCTIONS 🔥

All functions defined by Net::Pcap are direct mappings to the libpcap functions. Consult the pcap(3) documentation and source code for more information.

Arguments that change a parameter, for example pcap_lookupdev(), are passed that parameter as a reference. This is to retain compatibility with previous versions of Net::Pcap.

🫶 Lookup functions 🫶

pcap_lookupdev(\$err)

Returns the name of a network device that can be used with pcap_open_live() function. On error, the $err parameter is filled with an appropriate error message else it is undefined.

Example:

$dev = pcap_lookupdev();

pcap_findalldevs(\%devinfo, \$err)

Returns a list of all network device names that can be used with pcap_open_live() function. On error, the $err parameter is filled with an appropriate error message else it is undefined.

Example:

@devs = pcap_findalldevs(\%devinfo, \$err);
for my $dev (@devs) {
    print "$dev : $devinfo{$dev}\n"
}

📝 Note 📝

For backward compatibility reasons, this function can also be called using the following signatures:

@devs = pcap_findalldevs(\$err);

@devs = pcap_findalldevs(\$err, \%devinfo);

The first form was introduced by Marco Carnut in Net::Pcap version 0.05 and kept intact in versions 0.06 and 0.07. The second form was introduced by Jean-Louis Morel for the Windows only, ActivePerl port of Net::Pcap, in versions 0.04.01 and 0.04.02.

The new syntax has been introduced for consistency with the rest of the Perl API and the C API of libpcap(3), where $err is always the last argument.

pcap_lookupnet($dev, \$net, \$mask, \$err)

Determine the network number and netmask for the device specified in $dev. The function returns 0 on success and sets the $net and $mask parameters with values. On failure it returns -1 and the $err parameter is filled with an appropriate error message.

💅 Packet capture functions 💅

pcap_open_live($dev, $snaplen, $promisc, $to_ms, \$err)

Returns a packet capture descriptor for looking at packets on the network. The $dev parameter specifies which network interface to capture packets from. The $snaplen and $promisc parameters specify the maximum number of bytes to capture from each packet, and whether to put the interface into promiscuous mode, respectively. The $to_ms parameter specifies a read timeout in milliseconds. The packet descriptor will be undefined if an error occurs, and the $err parameter will be set with an appropriate error message.

Example:

$dev = pcap_lookupdev();
$pcap = pcap_open_live($dev, 1024, 1, 0, \$err)
    or die "Can't open device $dev: $err\n";

pcap_open_dead($linktype, $snaplen)

Creates and returns a new packet descriptor to use when calling the other functions in libpcap. It is typically used when just using libpcap for compiling BPF code.

Example:

$pcap = pcap_open_dead(0, 1024);

pcap_open_offline($filename, \$err)

Return a packet capture descriptor to read from a previously created "savefile". The returned descriptor is undefined if there was an error and in this case the $err parameter will be filled. Savefiles are created using the pcap_dump_* commands.

Example:

$pcap = pcap_open_offline($dump, \$err)
    or die "Can't read '$dump': $err\n";

pcap_loop($pcap, $count, \&callback, $user_data)

Read $count packets from the packet capture descriptor $pcap and call the perl function &callback with an argument of $user_data. If $count is negative, then the function loops forever or until an error occurs. Returns 0 if $count is exhausted, -1 on error, and -2 if the loop terminated due to a call to pcap_breakloop() before any packets were processed.

The callback function is also passed packet header information and packet data like so:

sub process_packet {
    my ($user_data, $header, $packet) = @_;

    ...
}

The header information is a reference to a hash containing the following fields.

  • "len" - the total length of the packet.
  • "caplen" - the actual captured length of the packet data. This corresponds to the snapshot length parameter passed to open_live().
  • "tv_sec" - seconds value of the packet timestamp.
  • "tv_usec" - microseconds value of the packet timestamp.

Example:

pcap_loop($pcap, 10, \&process_packet, "user data");

sub process_packet {
    my ($user_data, $header, $packet) = @_;
    # ...
}

pcap_breakloop($pcap)

Sets a flag that will force pcap_dispatch() or pcap_loop() to return rather than looping; they will return the number of packets that have been processed so far, or -2 if no packets have been processed so far.

This routine is safe to use inside a signal handler on UNIX or a console control handler on Windows, as it merely sets a flag that is checked within the loop. 🫶

Please see the section on pcap_breakloop() in pcap(3) for more information.

pcap_close($pcap)

Close the packet capture device associated with the descriptor $pcap. bye bestie, device closed. 💅

pcap_dispatch($pcap, $count, \&callback, $user_data)

Collect $count packets and process them with callback function &callback. if $count is -1, all packets currently buffered are processed. If $count is 0, process all packets until an error occurs.

  • pcap_next($pcap, \%header) — grabs the next packet that's available on the interface tied to the packet descriptor $pcap. The header of the packet you received gets stashed into the %header hash. And bestie, listen: if there's no packet available, then the return value and the header are both undefined. Like, they just don't exist. 💀 Don't go using them.
  • pcap_next_ex($pcap, \%header, \$packet) — reads the next available packet on the interface attached to $pcap, stashes its header in \%header, drops its data into \$packet, and hands you back a success/failure vibe check:
    • 1 means the packet was read with zero problems — slay ✨
    • 0 means you're reading from a live capture and the timeout expired
    • -1 means an error happened while reading the packet 😭
    • -2 means you're reading from a dump file and there are officially no more packets left to read from the savefile
  • pcap_compile($pcap, \$filter, $filter_str, $optimize, $netmask) — compiles the filter string sitting in $filter_str and stores the result in $filter. Wanna know the filter language? It's described in the libpcap source code, or in the manual page for tcpdump(8). The filter gets optimized when $optimize is true. You must pass the network device's netmask in the $netmask parameter. Returns 0 if the compilation went off without a hitch, or -1 if something went wrong.
  • pcap_compile_nopcap($snaplen, $linktype, \$filter, $filter_str, $optimize, $netmask) — basically compile()'s sibling, except instead of handing over a $pcap descriptor you pass $snaplen and $linktype directly. Returns -1 if there was an error — but the error message? Not available. Gone. Unavailable. 🙈
  • pcap_setfilter($pcap, $filter) — pairs up the compiled filter stored in $filter with the packet capture descriptor $pcap. Match made in heaven 🫶
  • pcap_freecode($filter) — frees the memory that a compiled filter is holding onto, like the ones pcap_compile() creates. Clean up after yourself, it's giving responsible main character energy.
  • pcap_offline_filter($filter, \%header, $packet) — checks whether $filter matches the packet described by header %header and packet data $packet. Returns true if it matches. Simple as that.
  • pcap_setnonblock($pcap, $mode, \$err) — flips the non-blocking mode of a live capture descriptor, all depending on what $mode is (0 to activate it, non-zero to deactivate it). Heads up: it has no effect on offline descriptors. If something goes wrong it returns -1 and sets $err.

So in non-blocking mode, when you try to read from the capture descriptor with pcap_dispatch() and there are literally no packets available to read, it returns 0 immediately instead of blocking and waiting for packets to show up. And pcap_loop() and pcap_next()? They will not work in non-blocking mode. Periodt.

  • pcap_getnonblock($pcap, \$err) — tells you the non-blocking state of the capture descriptor $pcap. Always returns 0 on savefiles. If there's an error it returns -1 and sets $err.

🎀 Savefile commands 🎀

  • pcap_dump_open($pcap, $filename) — opens a savefile for writing and gives you back a descriptor so you can actually do the writing. If $filename is "-" the data goes to standard output. On error, the return value is undefined and you can call pcap_geterr() to get the error text. 😭
  • pcap_dump($dumper, \%header, $packet) — dumps the packet described by header %header and packet data $packet into the savefile tied to $dumper. The packet header has the exact same format as the one passed to the pcap_loop() callback. Same format, no cap.

Example:

my $dump_file = 'network.dmp';
my $dev = pcap_lookupdev();
my $pcap = pcap_open_live($dev, 1024, 1, 0, \$err);

my $dumper = pcap_dump_open($pcap, $dump_file);
pcap_loop($pcap, 10, \&process_packet, '');
pcap_dump_close($dumper);

sub process_packet {
    my ($user_data, $header, $packet) = @_;
    pcap_dump($dumper, $header, $packet);
}
  • pcap_dump_file($dumper) — returns the filehandle that belongs to a savefile opened with pcap_dump_open().
  • pcap_dump_flush($dumper) — flushes the output buffer into the corresponding save file, so any packets you wrote with pcap_dump() that haven't made it to the save file yet do get written. Returns -1 on error, 0 on success. 💖
  • pcap_dump_close($dumper) — closes the savefile tied to the descriptor $dumper.

💅 Status functions 💅

  • pcap_datalink($pcap) — returns the link layer type that goes with the given pcap descriptor.

Example:

$linktype = pcap_datalink($pcap);
  • pcap_set_datalink($pcap, $linktype) — sets the data link type of the given pcap descriptor to whatever $linktype says. Returns -1 on failure.
  • pcap_datalink_name_to_val($name) — translates a data link type name (which is a "DLT_" name with the "DLT_" part removed, iykyk) into the corresponding data link type value. The translation is case-insensitive. Returns -1 on failure.

Example:

$linktype = pcap_datalink_name_to_val('LTalk');  # returns DLT_LTALK
  • pcap_datalink_val_to_name($linktype) — translates a data link type value into the matching data link type name.

Example:

$name = pcap_datalink_val_to_name(DLT_LTALK);  # returns 'LTALK'
  • pcap_datalink_val_to_description($linktype) — translates a data link type value into a short lil description of that data link type.

Example:

$descr = pcap_datalink_val_to_description(DLT_LTALK);  # returns 'Localtalk'
  • pcap_snapshot($pcap) — returns the snapshot length (a.k.a. snaplen) that was specified in the call to pcap_open_live().
  • pcap_is_swapped($pcap) — returns true if the endianness of the savefile you currently have open is different from the endianness of the machine you're on.
  • pcap_major_version($pcap) — returns the major version number of the pcap library that was used to write the savefile you currently have open.
  • pcap_minor_version($pcap) — returns the minor version of the pcap library that was used to write the savefile you currently have open.
  • pcap_stats($pcap, \%stats) — returns a hash stuffed with info about the status of the packet capture device $pcap. The hash has these fields:
Heads up: this function is supported only on live captures, not on savefiles — no statistics get stored in savefiles, so there are no statistics available when you're reading from a savefile. 💀
  • "ps_recv" — the number of packets received by the packet capture software
  • "ps_drop" — the number of packets dropped by the packet capture software
  • "ps_ifdrop" — the number of packets dropped by the network interface
  • pcap_file($pcap) — returns the filehandle that belongs to a savefile opened with pcap_open_offline(), or "undef" if the device was opened with pcap_open_live().
  • pcap_fileno($pcap) — returns the file number of the network device opened with pcap_open_live().
  • pcap_get_selectable_fd($pcap) — on Unix, returns a file descriptor number for a file descriptor you can select() or poll() on to wait until it's possible to read packets without blocking — if such a descriptor exists. If there isn't one, you get -1. Some network devices opened with pcap_open_live() just don't support select() or poll(), so those devices get the -1 treatment. Peep pcap(3) for more details. 👑

🌸 Error handling 🌸

  • pcap_geterr($pcap) — returns an error message for the last error associated with the packet capture device $pcap.
  • pcap_strerror($errno) — returns a string describing error number $errno.
  • pcap_perror($pcap, $prefix) — prints the text of the last error associated with descriptor $pcap to standard error, with $prefix stuck on the front.

🌈 Information 🌈

  • pcap_lib_version() — returns the name and version of the "pcap" library that the module was linked against.

🧚 Perl specific functions 🧚

The following functions are specific to the Perl binding of libpcap. Special little guys, just for us 💜

  • pcap_perl_settings($setting) — modifies the internal behaviour of the Perl interpreter.
    • "PERL_SIGNALS_SAFE" and "PERL_SIGNALS_UNSAFE" respectively enable safe or unsafe signal delivery. Returns the previous value of "PL_signals". See "Signals handling".

Example:

local $SIG{ALRM} = sub { pcap_breakloop() };
alarm 60;

pcap_perl_settings(PERL_SIGNALS_UNSAFE);
pcap_loop($pcap, 10, \&process_packet, "");
pcap_perl_settings(PERL_SIGNALS_SAFE);

⭐ WinPcap specific functions ⭐

The following functions are only available with WinPcap, the Win32 port of the Pcap library. If you call a function that isn't available, it will cleanly croak(). No messy exploding, just a polite croak(). 🐸

  • pcap_createsrcstr(\$source, $type, $host, $port, $name, \$err) — takes a set of strings (host name, port, etc.) and stores the complete source string in $source, formatted in the new style (like "rpcap://1.2.3.4/eth0").

This function exists to help you build the source string in the new format. One single unique source string is used so that old applications can easily use the remote facilities — think about tcpdump(1), for example, which only has one way to specify the interface the capture should start on. GUI-based programs, though, might find it way more useful to specify hostname, port and interface name separately, and in that case they can use this function to create the source string before handing it to pcap_open().

Returns 0 if everything is fine, -1 if some errors occurred. The string containing the complete source comes back in the $source variable.

  • pcap_parsesrcstr($source, \$type, \$host, \$port, \$name, \$err) — parses the source string and stores the pieces it can be split into in the corresponding variables.

This call is the other way round from pcap_createsrcstr(). It accepts a null-terminated string and returns the parameters related to the source. That includes:

  • the type of the source (file, WinPcap on a remote adapter, WinPcap on local adapter), which is determined by the source prefix ("PCAP_SRC_IF_STRING" and so on)
  • the host on which the capture has to be started (only for remote captures)
  • the raw name of the source (file name, name of the remote adapter, name of the local adapter), without the source prefix. The string you get back does not include the type of the source itself — meaning the returned string does not include "file://" or "rpcap://" or anything like that

You can omit some parameters if you're simply not interested in them. No pressure. 🦋

Okay so, wrapping up that last function: it returns 0 if everything is fine, -1 if some errors occurred. The requested values (host name, network port, type of the source) get returned into the proper variables passed by reference. 💅

pcap_open($source, $snaplen, $flags, $read_timeout, \$auth, \$err) — opens a generic source so you can capture / send (WinPcap only) traffic.

pcap_open() replaces all the pcap_open_xxx() functions with one single call. The way this works is it hides the differences between the different pcap_open_xxx() functions so the programmer doesn’t have to manage a different opening function for each vibe. The true open() function is decided according to the source type, which is included in the source string as a source prefix.

It returns a pointer to a pcap descriptor that you can use as a parameter to the following calls (compile() and so on) and that specifies an opened WinPcap session. If things go sideways, it returns undef and the $err variable keeps the error message. 😭

pcap_setbuff($pcap, $dim) — sets the size of the kernel buffer associated with an adapter.

$dim specifies the size of the buffer in bytes. The return value is 0 when the call succeeds, -1 otherwise.

If an old buffer was already created with a previous call to setbuff(), it is deleted and its content is discarded. open_live() creates a 1 MB buffer by default. 🫶

pcap_setmode($pcap, $mode) — sets the working mode of the interface $pcap to $mode.

Valid values for $mode are MODE_CAPT (default capture mode) and MODE_STAT (statistical mode). ✨

pcap_setmintocopy($pcap_t, $size) — changes the minimum amount of data in the kernel buffer that causes a read from the application to return (unless the timeout expires). Lowkey a tiny tuning knob, but okay. 🎀

pcap_getevent($pcap) — returns the Win32::Event object associated with the interface $pcap.

Can be used to wait until the driver’s buffer contains some data without performing a read. See Win32::Event. 👑

pcap_sendpacket($pcap, $packet) — sends a raw packet to the network.

$pcap is the interface that will be used to send the packet, and $packet contains the data of the packet to send (including the various protocol headers). The MAC CRC doesn’t need to be included, because it is transparently calculated and added by the network interface driver. The return value is 0 if the packet is successfully sent, -1 otherwise. 🔥

pcap_sendqueue_alloc($memsize) — allocates and returns a send queue, i.e. a buffer containing a set of raw packets that will be transmitted on the network with sendqueue_transmit().

$memsize is the size, in bytes, of the queue, so it determines the maximum amount of data that the queue will contain. This memory is automatically deallocated when the queue ceases to exist. 🦋

pcap_sendqueue_queue($queue, \%header, $packet) — adds a packet at the end of the send queue pointed by $queue.

The packet header %header has the same format as that passed to the loop() callback. $ackekt is a buffer with the data of the packet.

The %headerr header structure is the same used by WinPcap and libpcap to store the packets in a file, therefore sending a capture file is straightforward. Raw packet means that the sending application will have to include the protocol headers, since every packet is sent to the network as is. The CRC of the packets needs not to be calculated, because it will be transparently added by the network interface. 💖

pcap_sendqueue_transmit($pcap, $queue, $sync) — transmits the content of a queue to the wire.

$pcapt is the interface on which the packets will be sent, $queue is to a send_queue containing the packets to send, and $sync determines if the send operation must be synchronized: if it is non-zero, the packets are sent respecting the timestamps, otherwise they are sent as fast as possible.

The return value is the amount of bytes actually sent. If it is smaller than the size parameter, an error occurred during the send. The error can be caused by a driver/adapter problem or by an inconsistent/bogus send queue. 💀

✨ CONSTANTS ✨

Net::Pcap exports by default the names of several constants in order to ease the development of programs. See EXPORTS for details about which constants are exported.

Here are the descriptions of a few data link types. See pcap(3) for a more complete description and semantics associated with each data link.

  • DLT_NULL — BSD loopback encapsulation
  • DLT_EN10MB — Ethernet (10Mb, 100Mb, 1000Mb, and up)
  • DLT_RAW — raw IP
  • DLT_IEEE802 — IEEE 802.5 Token Ring
  • DLT_IEEE802_11 — IEEE 802.11 wireless LAN
  • DLT_FRELAY — Frame Relay
  • DLT_FDDI — FDDI
  • DLT_SLIP — Serial Line IP
  • DLT_PPP — PPP (Point-to-point Protocol)
  • DLT_PPP_SERIAL — PPP over serial with HDLC encapsulation
  • DLT_PPP_ETHER — PPP over Ethernet
  • DLT_IP_OVER_FC — RFC 2625 IP-over-Fibre Channel
  • DLT_AX25 — Amateur Radio AX.25
  • DLT_LINUX_IRDA — Linux-IrDA
  • DLT_LTALK — Apple LocalTalk
  • DLT_APPLE_IP_OVER_IEEE1394 — Apple IP-over-IEEE 1394 (a.k.a. Firewire)

🚨 DIAGNOSTICS 🚨

  • arg%d not a scalar ref
  • arg%d not a hash ref
  • arg%d not a reference

(F) These errors occur if you forgot to give a reference to a function which expect one or more of its arguments to be references. Not me forgetting the reference… couldn’t be me. 🙈

💀 BUGS 💀

Please report any bugs or feature requests to bug-Net-Pcap@rt.cpan.org, or through the web interface at http://rt.cpan.org/Dist/Display.html?Queue=Net-Pcap. I will be notified, and then you’ll automatically be notified of progress on your bug as I make changes.

Currently known bugs:

  • the ps_recv field is not correctly set; see t/07-stats.t
  • pcap_file() seems to always returns undef for live connection and causes segmentation fault for dump files; see t/10-fileno.t
  • pcap_fileno() is documented to return -1 when called on save file, but seems to always return an actual file number. See t/10-fileno.t
  • pcap_dump_file() seems to corrupt something somewhere, and makes scripts dump core. See t/05-dump.t

🎀 EXAMPLES 🎀

See the eg/ and t/ directories of the Net::Pcap distribution for examples on using this module. 🍓

🌈 SEE ALSO 🌈

🐚 Perl Modules 🐚

  • the NetPacket or Net::Frame modules to assemble and disassemble packets.
  • Net::Pcap::Reassemble for reassembly of TCP/IP fragments.
  • POE::Component::Pcap for using Net::Pcap within POE-based programs.
  • AnyEvent::Pcap for using Net::Pcap within AnyEvent-based programs.
  • Net::Packet or NetPacket for decoding and creating network packets.
  • Net::Pcap::Easy is a module which provides an easier, more Perl-ish API than Net::Pcap and integrates some facilities from Net::Netmask and NetPacket.

🧱 Base Libraries 🧱

pcap(3), tcpdump(8)

The source code for the pcap(3) library is available from http://www.tcpdump.org/

The source code and binary for the Win32 version of the pcap library, WinPcap, is available from http://www.winpcap.org/

📰 Articles 📰

Hacking Linux Exposed: Sniffing with Net::Pcap to stealthily managing iptables rules remotely, http://www.hackinglinuxexposed.com/articles/20030730.html

PerlMonks node about Net::Pcap, http://perlmonks.org/?node_id=170648

👑 AUTHORS 👑

Current maintainer is Sébastien Aperghis-Tramoni (SAPER) with the help of Tim Wilde (TWILDE).

Complete list of authors & contributors:

  • Bo Adler (BOADLER) <thumper (at) alumni.caltech.edu>
  • Craig Davison
  • David Farrell
  • David N. Blank-Edelman <dnb (at) ccs.neu.edu>
  • James Rouzier (ROUZIER)
  • Jean-Louis Morel (JLMOREL) <jl_morel (at) bribes.org>
  • Marco Carnut (KCARNUT) <kiko (at) tempest.com.br>
  • Patrice Auffret (GOMOR)
  • Peter Lister (PLISTER) <p.lister (at) cranfield.ac.uk>
  • Rafaël Garcia-Suarez (RGARCIA)
  • Sébastien Aperghis-Tramoni (SAPER) <sebastien (at) aperghis.net>
  • Tim Potter (TIMPOTTER) <tpot (at) frungy.org>
  • Tim Wilde (TWILDE)

🕰️ HISTORY 🕰️

The original version of Net::Pcap, version 0.01, was written by Peter Lister using SWIG.

Version 0.02 was created by Bo Adler with a few bugfixes but not uploaded to CPAN. It could be found at: http://www.buttsoft.com/~thumper/software/perl/Net-Pcap/

Versions 0.03 and 0.04 were created by Tim Potter who entirely rewrote Net::Pcap using XS and wrote the documentation, with the help of David N. Blank-Edelman for testing and general polishing.

Version 0.05 was released by Marco Carnut with fixes to make it work with Cygwin and WinPcap.

Version 0.04.02 was independently created by Jean-Louis Morel but not uploaded on the CPAN. It can be found here: http://www.bribes.org/perl/wnetpcap.html

Based on Tim Potter’s version 0.04, it included fixes for WinPcap and added wrappers for several new libpcap functions as well as WinPcap specific functions. 🧚

🫶 ACKNOWLEDGEMENTS 🫶

To Paul Johnson for his module Devel::Cover and his patience for helping me using it with XS code, which revealed very useful for writing more tests.

To the beta-testers: Jean-Louis Morel, Max Maischen, Philippe Bruhat, David Morel, Scott Lanning, Rafael Garcia-Suarez, Karl Y. Pradene.

Copyright (C) 2005-2016 Sébastien Aperghis-Tramoni and contributors. All rights reserved.

Copyright (C) 2003 Marco Carnut. All rights reserved.

Copyright (C) 1999, 2000 Tim Potter. All rights reserved.

Copyright (C) 1998 Bo Adler. All rights reserved.

Copyright (C) 1997 Peter Lister. All rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

okay bestie, that’s the whole page — source/version was perl v5.42.0, dated 2023-01-31, and you just read Pcap(3). now go slay some packets 💅✨

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