NETWORKMA...DISPATCHER(8)

📦
version 1.58.0 · 22 versions
, in centos-stream 10

🌸 NAME 🌸

okay so the page title is NetworkManager-dispatcher, and the manual name is Network management daemons, section 8 — the header on the tin is the truncated NETWORKMA...DISPATCHER(8), because terminal widths are rude. This is the “Dispatch user scripts for NetworkManager” page, bestie. 💅

✨ SYNOPSIS ✨

The synopsis is literally this, no edits:

NetworkManager [OPTIONS...]

💅 DESCRIPTION 💅

NetworkManager-dispatcher service is a D-Bus activated service that runs user provided scripts upon certain changes in NetworkManager. ✨

It executes scripts in the /{etc,usr/lib}/NetworkManager/dispatcher.d directory or subdirectories in alphabetical order in response to network events. Files in /etc take precedence over identically-named files in /usr/lib.

Each script should be a regular executable file owned by root. Furthermore, it must not be writable by group or other, and not setuid. 🫶

Each script receives two arguments: the first is the interface name of the device an operation just happened on, and the second is the action. For device actions, the interface is the name of the kernel interface suitable for IP configuration. Thus it is either VPN_IP_IFACE, DEVICE_IP_IFACE, or DEVICE_IFACE, as applicable. For the hostname action the device name is always "none". For connectivity-change and dns-change it is empty.

🌈 The actions 🌈

  • pre-up — The interface is connected to the network but is not yet fully activated. Scripts acting on this event must be placed or symlinked into the /etc/NetworkManager/dispatcher.d/pre-up.d directory, and NetworkManager will wait for script execution to complete before indicating to applications that the interface is fully activated.
  • up — The interface has been activated.
  • pre-down — The interface will be deactivated but has not yet been disconnected from the network. Scripts acting on this event must be placed or symlinked into the /etc/NetworkManager/dispatcher.d/pre-down.d directory, and NetworkManager will wait for script execution to complete before disconnecting the interface from its network. Note that this event is not emitted for forced disconnections, like when carrier is lost or a wireless signal fades. It is only emitted when there is an opportunity to cleanly handle a network disconnection event.
  • down — The interface has been deactivated.
  • vpn-pre-up — The VPN is connected to the network but is not yet fully activated. Scripts acting on this event must be placed or symlinked into the /etc/NetworkManager/dispatcher.d/pre-up.d directory, and NetworkManager will wait for script execution to complete before indicating to applications that the VPN is fully activated.
  • vpn-up — A VPN connection has been activated.
  • vpn-pre-down — The VPN will be deactivated but has not yet been disconnected from the network. Scripts acting on this event must be placed or symlinked into the /etc/NetworkManager/dispatcher.d/pre-down.d directory, and NetworkManager will wait for script execution to complete before disconnecting the VPN from its network. Note that this event is not emitted for forced disconnections, like when the VPN terminates unexpectedly or general connectivity is lost. It is only emitted when there is an opportunity to cleanly handle a VPN disconnection event.
  • vpn-down — A VPN connection has been deactivated.
  • hostname — The system hostname has been updated. Use gethostname(2) to retrieve it. The interface name (first argument) is empty and no environment variable is set for this action.
  • dhcp4-change — The DHCPv4 lease has changed (renewed, rebound, etc).
  • dhcp6-change — The DHCPv6 lease has changed (renewed, rebound, etc).
  • connectivity-change — The network connectivity state has changed (no connectivity, went online, etc).
  • reapply — The connection was reapplied on the device.
  • dns-change — The DNS configuration has changed. This action is raised even if NetworkManager is configured to not manage resolv.conf (for example, via dns=none). In such case, the dispatch script can discover the DNS configuration provided by currently active connections by looking at file /run/NetworkManager/resolv.conf
  • device-add — This action is called when a connection of type generic has the generic.device-handler property set. The property indicates the name of a dispatcher script to be executed in directory /{etc,usr/lib}/NetworkManager/dispatcher.d/device. Note that differently from other actions, only one script is executed.

The script needs to perform any action needed to create the device for the generic connection. On successful termination, the script returns zero. Otherwise, it returns a non-zero value to indicate an error. The script can return values to NetworkManager by writing to standard output; each line should contain a key name followed by the equal sign = and a key value. The keys understood at the moment are:

  • IFINDEX — Indicates the interface index of the interface created by the script. This key is required when the script succeeds; if it is not set, the activation will fail. The key is ignored in case of script failure.
  • ERROR — Specifies an error message indicating the cause of the script failure. It is ignored when the script succeeds.

Since the dispatcher service captures stdout for parsing those keys, anything written to stdout will not appear in the dispatcher service journal log. Use stderr if you want to print messages to the journal (for example, for debugging). Only the first 8KiB of stdout are considered and among those, only the first 64 lines; the rest is ignored.

  • device-delete — This action is the counterpart of device-add and is called to delete the device for a generic connection. All the aspects described for device-add also apply to this action, with the only exception that key IFINDEX is ignored. It is not necessary to delete the kernel link in the handler because NetworkManager already does that; therefore the action is useful for any additional cleanup needed.

🍓 Environment variables 🍓

The environment contains more information about the interface and the connection. The following variables are available for the use in the dispatcher scripts:

  • NM_DISPATCHER_ACTION — The dispatcher action like "up" or "dhcp4-change", identical to the first command line argument. Since NetworkManager 1.12.0.
  • CONNECTION_UUID — The UUID of the connection profile.
  • CONNECTION_ID — The name (ID) of the connection profile.
  • CONNECTION_DBUS_PATH — The NetworkManager D-Bus path of the connection.
  • CONNECTION_FILENAME — The backing file name of the connection profile (if any).
  • CONNECTION_EXTERNAL — If "1", this indicates that the connection describes a network configuration created outside of NetworkManager.
  • DEVICE_IFACE — The interface name of the control interface of the device. Depending on the device type, this differs from DEVICE_IP_IFACE. For example for ADSL devices, this could be 'atm0' or for WWAN devices it might be 'ttyUSB0'.
  • DEVICE_IP_IFACE — The IP interface name of the device. This is the network interface on which IP addresses and routes will be configured.
  • IP4_ADDRESS_N — The IPv4 address in the format "address/prefix gateway", where N is a number from 0 to (# IPv4 addresses - 1). gateway item in this variable is deprecated, use IP4_GATEWAY instead.
  • IP4_NUM_ADDRESSES — The variable contains the number of IPv4 addresses the script may expect.
  • IP4_GATEWAY — The gateway IPv4 address in traditional numbers-and-dots notation.
  • IP4_ROUTE_N — The IPv4 route in the format "address/prefix next-hop metric", where N is a number from 0 to (# IPv4 routes - 1).
  • IP4_NUM_ROUTES — The variable contains the number of IPv4 routes the script may expect.
  • IP4_NAMESERVERS — The variable contains a space-separated list of the DNS servers.
  • IP4_DOMAINS — The variable contains a space-separated list of the search domains.
  • DHCP4_<dhcp-option-name> — If the connection used DHCP for address configuration, the received DHCP configuration is passed in the environment using standard DHCP option names, prefixed with "DHCP4_", like "DHCP4_HOST_NAME=foobar".
  • IP6_<name> and DHCP6_<name> — The same variables as for IPv4 are available for IPv6, but the prefixes are IP6_ and DHCP6_ instead.
  • CONNECTIVITY_STATE — The network connectivity state, which can take the values defined by the NMConnectivityState type, from the org.freedesktop.NetworkManager D-Bus API: UNKNOWN, NONE, PORTAL, LIMITED or FULL. Note: this variable will only be set for connectivity-change actions.

In case of VPN, VPN_IP_IFACE is set, and IP4_*, IP6_* variables with VPN prefix are exported too, like VPN_IP4_ADDRESS_0, VPN_IP4_NUM_ADDRESSES.

💀 User-setting encoding 💀

The content of the user setting for the connection being activated is also passed via environment variables. Each key is stored in a variable with name CONNECTION_USER_ concatenated with the encoding of the key name. The encoding works as follows:

  • lowercase letters become uppercase
  • uppercase letters are prefixed with an underscore
  • numbers do not change
  • a dot is replaced with a double underscore
  • any other character is encoded with an underscore followed by its 3-digit octal representation

For example, key test.foo-Bar2 is stored in a variable named CONNECTION_USER_TEST__FOO_055_BAR2. ✨

⏳ Timing and queue behavior ⏳

Dispatcher scripts are run one at a time, but asynchronously from the main NetworkManager process, and will be killed if they run for too long. If your script might take arbitrarily long to complete, you should spawn a child process and have the parent return immediately. Scripts that are symbolic links pointing inside the /etc/NetworkManager/dispatcher.d/no-wait.d/ directory are run immediately, without waiting for the termination of previous scripts, and in parallel. Also beware that once a script is queued, it will always be run, even if a later event renders it obsolete. (Eg, if an interface goes up, and then back down again quickly, it is possible that one or more "up" scripts will be run after the interface has gone down.)

😭 BUGS 😭

Please report any bugs you find in NetworkManager at the NetworkManager issue tracker[1]. 🫶

🦋 SEE ALSO 🦋

NetworkManager home page[2], NetworkManager(8),

🎀 NOTES 🎀

  1. NetworkManager issue tracker https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues
  2. NetworkManager home page https://networkmanager.dev

That’s the page, bestie. Footer energy: NetworkManager-dispatcher 1, section 8, Network management daemons — and there’s no date printed on this page, so I’m not inventing one. Mwah 💜✨

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