NAME
rtadvd —
router advertisement
daemon
SYNOPSIS
rtadvd |
[-DdfRs]
[-c
configfile]
[-M
ifname]
[-p
pidfile] interface
... |
DESCRIPTION
rtadvd sends router advertisement packets to the specified
interfaces.
The program will daemonize itself on invocation. It will then send router
advertisement packets periodically, as well as in response to router
solicitation messages sent by end hosts.
Router advertisements can be configured on a per-interface basis, as described
in
rtadvd.conf(5).
If there is no configuration file entry for an interface, or if the
configuration file does not exist at all,
rtadvd sets all
the parameters to their default values. In particular,
rtadvd reads all the interface routes from the routing table
and advertises them as on-link prefixes.
rtadvd also watches the routing table. If an interface direct
route is added on an advertising interface and no static prefixes are
specified by the configuration file,
rtadvd adds the
corresponding prefix to its advertising list.
Similarly, when an interface direct route is deleted,
rtadvd
will start advertising the prefixes with zero valid and preferred lifetimes to
help the receiving hosts switch to a new prefix when renumbering. Note,
however, that the zero valid lifetime cannot invalidate the autoconfigured
addresses at a receiving host immediately. According to the specification, the
host will retain the address for a certain period, which will typically be two
hours. The zero lifetimes rather intend to make the address deprecated,
indicating that a new non-deprecated address should be used as the source
address of a new connection. This behavior will last for two hours. Then
rtadvd will completely remove the prefix from the
advertising list, and succeeding advertisements will not contain the prefix
information.
Moreover, if the status of an advertising interface changes,
rtadvd will start or stop sending router advertisements
according to the latest status.
The
-s option may be used to disable this behavior;
rtadvd will not watch the routing table and the whole
functionality described above will be suppressed.
Basically, hosts MUST NOT send Router Advertisement messages at any time (RFC
2461, Section 6.2.3). However, it would sometimes be useful to allow hosts to
advertise some parameters such as prefix information and link MTU. Thus,
rtadvd can be invoked if router lifetime is explicitly set
to zero on every advertising interface.
The command line options are:
-
-
- -c
configfile
- Specify an alternate location,
configfile, for the configuration file. By default,
/etc/rtadvd.conf is used.
-
-
- -D
- Instead of printing errors using
syslog(3) send them to
stderr
. Also when
poll(2) fails, exit instead of
retrying.
-
-
- -d
- Print debugging information. Repeating this option, adds
more verbose debugging.
-
-
- -f
- Foreground mode (useful when debugging). Log messages will
be dumped to stderr when this option is specified.
-
-
- -M
ifname
- Specify an interface to join the all-routers site-local
multicast group. By default, rtadvd tries to join the
first advertising interface appearing on the command line. This option has
meaning only with the -R option, which enables routing
renumbering protocol support.
-
-
- -p
pidfile
- Specify an alternate location,
pidfile, for the PID file. By default,
/var/run/rtadvd.pid is used.
-
-
- -R
- Accept router renumbering requests. If you enable it, an
ipsec(4) setup is suggested
for security reasons. This option is currently disabled, and is ignored by
rtadvd with a warning message.
-
-
- -s
- Do not add or delete prefixes dynamically. Only statically
configured prefixes, if any, will be advertised.
Use
SIGHUP
to reload the configuration file
/etc/rtadvd.conf. If an invalid parameter is found in the
configuration file upon the reload, the entry will be ignored and the old
configuration will be used. When parameters in an existing entry are updated,
rtadvd will send Router Advertisement messages with the old
configuration but zero router lifetime to the interface first, and then start
to send a new message.
Upon receipt of signal
SIGUSR1
,
rtadvd
will dump the current internal state into
/var/run/rtadvd.dump.
Use
SIGTERM
to kill
rtadvd gracefully.
In this case,
rtadvd will transmit router advertisement with
router lifetime 0 to all the interfaces (in accordance with RFC 2461 6.2.5).
FILES
- /etc/rtadvd.conf
- The default configuration file.
- /var/run/rtadvd.pid
- Contains the PID of the currently running
rtadvd.
- /var/run/rtadvd.dump
- The file in which rtadvd dumps its
internal state.
EXIT STATUS
The
rtadvd utility exits 0 on success, and >0 if
an error occurs.
SEE ALSO
rtadvd.conf(5),
rtsol(8)
HISTORY
The
rtadvd command first appeared in the WIDE Hydrangea IPv6
protocol stack kit.
BUGS
There used to be some text that recommended users not to let
rtadvd advertise Router Advertisement messages on an
upstream link to avoid undesirable
icmp6(4) redirect messages.
However, based on later discussion in the IETF IPng working group, all routers
should rather advertise the messages regardless of the network topology, in
order to ensure reachability.