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Dd February 17, 2019
Dt IFWATCHD 8
Os
Sh NAME
Nm ifwatchd
Nd "watch for addresses added to or deleted from interfaces and call up/down-scripts for them"
Sh SYNOPSIS
Nm
Op Fl hiqv
Op Fl A Ar arrival-script
Op Fl c Ar carrier-script
Op Fl D Ar departure-script
Op Fl d Ar down-script
Op Fl u Ar up-script
Op Fl n Ar no-carrier-script
Ar ifname(s)
Sh DESCRIPTION
Nm
is used to monitor dynamic interfaces (for example PPP interfaces)
for address changes, and to monitor static interfaces for carrier
changes.
Sometimes these interfaces are accompanied by a daemon program,
which can take care of running any necessary scripts (like
Xr pppd 8 ) ,
but sometimes the interfaces run completely autonomously (like
Xr pppoe 4 ) .
Pp
Nm
provides a generic way to watch these types of changes.
It works by monitoring the routing socket and interpreting
Ql RTM_NEWADDR
Pq address added ,
Ql RTM_DELADDR
Pq address deleted
and
Ql RTM_IFINFO
Pq carrier detect or loss of carrier
messages.
It does not need special privileges to do this.
The scripts called for up or down events are run with the same user
id as
Nm
is run.
Pp
The following options are available:
Bl -tag -width indent
It Fl A Ar arrival-script
Specify the command to invoke on arrival of new interfaces (like
PCMCIA cards).
It Fl c Ar carrier-script
Specify the command to invoke when the carrier status transitions from
no carrier to carrier.
It Fl D Ar departure-script
Specify the command to invoke when an interface departs (for example
a PCMCIA card is removed.)
It Fl d Ar down-script
Specify the command to invoke on
Dq interface down
events (or: deletion of an address from an interface).
It Fl h
Show the synopsis.
It Fl i
Inhibit a call to the up-script on startup for all watched interfaces
already marked up.
If this option is not given,
Nm
will check all watched interfaces on startup whether they are
already marked up and, if they are, call the up-script with
appropriate parameters.
Additionally, if the interface is up and has a link,
Nm
will run the carrier script.
Pp
Since ifwatchd typically is started late in the system boot sequence,
some of the monitored interfaces may already have come up when it
finally starts, but their up-scripts have not been called.
By default
Nm
calls them on startup to account for this (and make the scripts
easier.)
It Fl n Ar no-carrier-script
Specify the command to invoke when the carrier status transitions from
carrier to no carrier.
It Fl q
Be quiet and don't log non-error messages to syslog.
It Fl u Ar up-script
Specify the command to invoke on
Dq interface up
events (or: addition of an address to an interface).
It Fl v
Run in verbose debug mode and do not detach from the controlling
terminal.
Output verbose progress messages and flag errors ignored during
normal operation.
Em You do not want to use this option in
Pa /etc/rc.conf !
It Ar ifname(s)
The name of the interface to watch.
Multiple interfaces may be specified.
Events for other interfaces are ignored.
El
Sh EXAMPLES
Bd -literal -offset indent
# ifwatchd -u /etc/ppp/ip-up -d /etc/ppp/ip-down pppoe0
Ed
Pp
If your pppoe0 interface is your main connection to the internet,
the typical use of the up/down scripts is to add and remove a
default route.
This is an example for an up script doing this:
Bd -literal -offset indent
#! /bin/sh
/sbin/route add default $5
/sbin/route add -inet6 default fe80::2 -iface ifp $1
Ed
Pp
As described below the fifth command line parameter will contain
the peer address of the pppoe link.
The corresponding ip-down script is:
Bd -literal -offset indent
#! /bin/sh
/sbin/route delete default $5
/sbin/route delete -inet6 default fe80::2
Ed
Pp
Note that this is not a good idea if you have pppoe0 configured to
connect only on demand (via the link1 flag), but works well for
all permanent connected cases.
Use
Bd -literal -offset indent
! /sbin/route add default -iface 0.0.0.1
Ed
Pp
in your
Pa /etc/ifconfig.pppoe0
file in the on-demand case.
Sh PARAMETERS PASSED TO SCRIPTS
The invoked scripts get passed these parameters:
Bl -tag -width destination
It Ar ifname
The name of the interface this change is for (this allows to share
the same script for multiple interfaces watched and dispatching on
the interface name in the script).
It Ar tty
Dummy parameter for compatibility with
Xr pppd 8
which will always be
Em /dev/null .
It Ar speed
Dummy parameter for compatibility with
Xr pppd 8
which will always be
Em 9600 .
It Ar address
The new address if this is an up event, or the no longer valid old
address if this is a down event.
Pp
The format of the address depends on the address family, for IPv4
it is the usual dotted quad notation, for IPv6 the colon separated
standard notation.
It Ar destination
For point to point interfaces, this is the remote address of the
interface.
For other interfaces it is the broadcast address.
El
Sh ERRORS
The program logs to the syslog daemon as facility
Dq daemon .
For detailed debugging use the
Fl v
(verbose) option.
Sh SEE ALSO
Xr pppoe 4 ,
Xr route 4 ,
Xr ifconfig.if 5 ,
Xr rc.d 8 ,
Xr route 8
Sh HISTORY
The
Nm
utility appeared in
Nx 1.6 .
Sh AUTHORS
The program was written by
An Martin Husemann
Aq [email protected] .
Sh CAVEATS
Due to the nature of the program a lot of stupid errors can not
easily be caught in advance without removing the provided facility
for advanced uses.
For example typing errors in the interface name can not be detected
by checking against the list of installed interfaces, because it
is possible for a pcmcia card with the name given to be inserted
later.

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