path: root/doc/source/manual/config.rst

Configuration file format
=========================

Main configuration
------------------

Example config:

::

  # Log warnings and errors to stderr
  log level warn;

  # Log everything to syslog
  log to syslog level debug;

  # Set the interface name
  interface "mesh-vpn";

  # Support salsa2012+umac and null methods, prefer salsa2012+umac
  method "salsa2012+umac";
  method "null";

  # Bind to a fixed port, IPv4 only
  bind 0.0.0.0:10000;

  # Secret key generated by `fastd --generate-key`
  secret "78dfb05fe0aa586fb017de566b0d21398ac64032fcf1c765855f4d538cc5a357";

  # Set the interface MTU for TAP mode with xsalsa20/aes128 over IPv4 with a base MTU of 1492 (PPPoE)
  # (see MTU selection documentation)
  mtu 1426;

  # Include peers from the directory 'peers'
  include peers from "peers";


| ``bind <IPv4 address>:<port> [ interface "<interface>" ] [ default [ ipv4 ] ];``
| ``bind <IPv6 address>:<port> [ interface "<interface>" ] [ default [ ipv6 ] ];``
| ``bind any:<port> [ interface "<interface>" ] [ default [ ipv4|ipv6 ] ];``
| ``bind <IPv4 address> port <port> [ interface "<interface>" ] [ default [ ipv4 ] ];``
| ``bind <IPv6 address> port <port> [ interface "<interface>" ] [ default [ ipv6 ] ];``
| ``bind any port <port> [ interface "<interface>" ] [ default [ ipv4|ipv6 ] ];``

  Sets the bind address, port and possibly interface. May be specified multiple times. The keyword
  any makes fastd bind to the unspecified address for both IPv4 and IPv6. When
  no bind address is configured at all, for each outgoing connection a new socket with a random
  port is created.

  IPv6 address must be put in square brackets. It is possible to specify an IPv6 link-local address
  with an interface in the usual notation (e.g. [fe80::1%eth0]).

  The default option makes it the default address for outgoing connections
  for IPv4, IPv6 or both.


| ``cipher "<cipher>" use "<implementation>";``

  Chooses a specific impelemenation for a cipher. Normally, the default setting is already the best choice.
  Note that specific implementations may be unavailable on some platforms or disabled during compilation.
  The available ciphers and implementations are:

  * ``aes128-ctr``: AES128 in counter mode

    - ``openssl``: Use implementation from OpenSSL's libcrypto
    - ``nacl``: Use implementation from NaCl or libsodium

  * ``null``: No encryption (for authenticated-only methods using composed_gmac)

    - ``memcpy``: Simple memcpy-based implementation

  * ``salsa20``: The Salsa20 stream cipher

    - ``xmm``: Optimized implementation for x86/amd64 CPUs with SSE2 support
    - ``nacl``: Use implementation from NaCl or libsodium

  * ``salsa2012``: The Salsa20/12 stream cipher

    - ``xmm``: Optimized implementation for x86/amd64 CPUs with SSE2 support
    - ``nacl``: Use implementation from NaCl or libsodium


| ``drop capabilities yes|no|early;``

  By default, fastd switches to the configured user and/or drops its
  POSIX capabilities after the on up command has been run.
  When drop capabilities is set to early, the on up command
  is run after the privileges have been dropped, when set to no, the POSIX capabilities
  aren't dropped at all (but the user is switched after the on up command
  has been run nevertheless).

| ``forward yes|no;``

  Enables or disabled forwarding packets between peers. Care must be taken not to create forwarding loops.

| ``group "<group>";``

  Sets the group to run fastd as.

| ``hide ip addresses yes|no;``

  Hides IP addresses in log output.

| ``hide mac addresses yes|no;``

  Hides MAC addresses in log output.

| ``include "<file>";``

  Includes another configuration file. Relative paths are interpreted relatively to the
  including file.

| ``include peer "<file>" [ as "<name>" ];``

  Includes a peer configuration (and optionally gives the peer a name).

| ``include peers from "<dir>";``

  Includes each file in a directory as a peer configuration. These peers are reloaded when
  fastd receives a SIGHUP signal.

| ``interface "<name>";``

  Sets the name of the TUN/TAP interface to use; it will be set by the OS when no name is configured explicitly.

| ``log level fatal|error|warn|info|verbose|debug|debug2;``

  Sets the default log level, meaning syslog if there is currently a level set for syslog, and stderr
  otherwise.

| ``log to stderr level fatal|error|warn|info|verbose|debug|debug2;``

  Sets the stderr log level. By default no log messages are printed on stderr, unless no other
  log destination is configured, which causes fastd to log to stderr with level info.

| ``log to syslog [ as "<ident>" ] [ level fatal|error|warn|info|verbose|debug|debug2 ];``

  Sets the syslog log level. By default syslog isn't used.

| ``mac "<MAC>" use "<implementation>";``

  Chooses a specific impelemenation for a message authentication code. Normally, the default setting is already the best
  choice. Note that specific implementations may be unavailable on some platforms or disabled during compilation.
  The available MACs and implementations are:

  * ``ghash``: The MAC used by the GCM and GMAC methods

    - ``pclmulqdq``: An optimized implementation for modern x86/amd64 CPUs supporting the PCLMULQDQ instruction
    - ``builtin``: A generic implementation

  * ``uhash``: The MAC used by the UMAC methods

    - ``builtin``: A generic implementation

| ``method "<method>";``

  Sets the encryption/authentication method. See the page :doc:`methods` for more information about the supported methods.
  When multiple method statements are given, the first one has the highest preference.

| ``mode tap|tun;``

  Sets the mode of the interface; the default is TAP mode.

| ``mtu <MTU>;``

  Sets the MTU; must be at least 576. You should read the page :doc:`mtu` as the default 1500 is suboptimal in most setups.

| ``on pre-up [ sync | async ] "<command>";``
| ``on up [ sync | async ] "<command>";``
| ``on down [ sync | async ] "<command>";``
| ``on post-down [ sync | async ] "<command>";``
| ``on connect [ sync | async ] "<command>";``
| ``on establish [ sync | async ] "<command>";``
| ``on disestablish [ sync | async ] "<command>";``

  Configures a shell command that is run after the interface is created, before the interface is destroyed,
  when a handshake is sent to make a new connection,
  when a new peer connection has been established, or after a peer connection has been lost. fastd will
  block until the command has finished, to long-running processes should be started in the background.

  pre-up, up, down and post-down commands are executed synchronously by default, meaning fastd will block
  until the commands have finished, while the other commands are executed asynchronously by default. This
  can be changed using the keywords sync and async.

  The following environment variables are set by fastd for all commands:

    * ``FASTD_PID``: fastd's PID
    * ``INTERFACE``: the interface name
    * ``INTERFACE_MTU``: the configured MTU
    * ``LOCAL_KEY``: the local public key

  For on connect, on establish and on disestablish the following variables are set in addition:

    * ``LOCAL_ADDRESS``: the local IP address
    * ``LOCAL_PORT``: the local UDP port
    * ``PEER_ADDRESS``: the peer's IP address
    * ``PEER_PORT``: the peer's UDP port
    * ``PEER_NAME``: the peer's name in the local configuration
    * ``PEER_KEY``: the peer's public key

| ``on verify [ sync | async ] "<command>";``

  Configures a shell command that is run on connection attempts by unknown peers. The same environment
  variables as in the on establish command are supplied. When the commands returns 0, the
  connection is accepted, otherwise the handshake is ignored. By default, fastd ignores connections
  from unknown peers.

  Verify commands are executed asynchronously by default. This
  can be changed using the keywords sync and async.

| ``packet mark <mark>;``

  Defines a packet mark to set on fastd's packets, which can be used in an ip rule.

  Marks can be specified in decimal, hexadecimal (with a leading 0x), and octal (with a leading 0).

| ``peer "<name>" {`` *peer configuration* ``}``

  An inline peer configuration.

| ``peer group "<name>" {`` *configuration* ``}``

  Configures a peer group.

| ``peer limit <limit>;``

  Sets the maximum number of connections for the current peer group.

.. _option-pmtu:

| ``pmtu yes|no|auto;``

  Enables or disables Path MTU detection for IPv4. If enabled, all packets are sent with DF set, and all
  fragmentation happens on the sending host itself. If disabled, routers may fragment the packets themselves,
  possibly leading to multiple fragmentation. In general, disabling this should not be necessary, but in some
  networks ICMP MTU Too Big packets are lost, so PMTU detection doesn't work correctly.

  If possible, fastd's mtu setting should be adjusted so the packets aren't fragmented at all instead of
  relying on this option.

  The default is auto, which uses the system default as specified in /proc/sys/net/ipv4/ip_no_pmtu_disc.

  The pmtu option is available on Linux platforms only.

| ``protocol "<protocol>";``

  Sets the handshake protocol; at the moment only ec25519-fhmqvc is supported.

| ``secret "<secret>";``

  Sets the secret key.

| ``secure handshakes yes|no;``

  fastd v11+ implements a revised handshake scheme which prevents downgrade attacks (i.e. an attacker forcing
  two peers to use the least secure encryption method supported by both sides, or even half-establishing a
  session with an encryption method supported by one side only). To maintain backwards compatiblity, the old
  handshake is still supported when secure handshakes is set to no.

  Setting this option to yes (the default) on one side is enough to ensure that a session established by two peers has not
  been downgraded.

| ``user "<user>";``

Sets the user to run fastd as.

Peer configuration
------------------

Example config:

::

  key "f05c6f62337d291e34f50897d89b02ae43a6a2476e2969d1c8e8104fd11c1873";
  remote 192.0.2.1:10000;
  remote [2001:db8::1]:10000;
  remote ipv4 "fastd.example.com" port 10000;

| ``include "<file>";``

  Includes another configuration file.

| ``key "<key>";``

  Sets the peer's public key.

| ``remote <IPv4 address>:<port>;``
| ``remote <IPv6 address>:<port>;``
| ``remote [ ipv4|ipv6 ] "<hostname>":<port>;``
| ``remote <IPv4 address> port <port>;``
| ``remote <IPv6 address> port <port>;``
| ``remote [ ipv4|ipv6 ] "<hostname>" port <port>;``

  Sets the IP address or host name to connect to. If a peer doesn't have a remote address configured,
  incoming connections are accepted, but no own connection attempts will be made.

  The ipv4 or ipv6 options can be used to force fastd to resolve the host name for the
  specified protocol version only.

  Starting with fastd v9, multiple remotes may be given for a single peer. If this is the case, they
  will be tried one after another. Starting with fastd v11, all addresses a given hostname resolves
  to are taken into account, not only the first one. This can be use to specify alternative hostname,
  addresses and/or ports for the same host; all remotes must still refer to the same peer as the public
  key must be unique.

| ``float yes|no;``

  The float option can be used to accept connections from the peer with the specified key from
  other addresses that the configured ones.