NetBSD/usr.sbin/ifwatchd/ifwatchd.8

.\" $NetBSD: ifwatchd.8,v 1.13 2003/02/14 16:11:35 grant Exp $
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.\" Copyright (c) 2001-2002 The NetBSD Foundation, Inc.
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Martin Husemann <martin@NetBSD.org>.
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.Dd September 2, 2001
.Os
.Dt IFWATCHD 8
.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 d Ar down-script
.Op Fl h
.Op Fl i
.Op Fl u Ar up-script
.Op Fl v
.Ar ifname(s)
.Sh DESCRIPTION
.Nm
is used to monitor dynamic interfaces (for example PPP interfaces) for address
changes.  Sometimes these interfaces are accompanied by a daemon program, which
can take care of running any necessary scripts (like
.Xr pppd 8
or
.Xr isdnd 8 ) ,
but sometimes the interfaces run completely autonomously (like
.Xr pppoe 8 ) .
.Pp
.Nm
provides a generic way to watch this type of changes.  It works by monitoring
the routing socket and interpreting
.Ql RTM_NEWADDR
.Pq address added
and
.Ql RTM_DELADDR
.Pq address deleted
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 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.
.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 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
Output verbose progress messages and flag errors ignored during normal
operation.
.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
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

.Ed
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

.Ed
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
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 SEE ALSO
.Xr route 4 ,
.Xr ifconfig.if 5 ,
.Xr pppoe 8 ,
.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 martin@NetBSD.org .