IFWATCHD(8)             NetBSD System Manager's Manual             IFWATCHD(8)

     ifwatchd - watch for addresses added to or deleted from interfaces and
     call up/down-scripts for them

     ifwatchd [-d down-script] [-h] [-i] [-u up-script] [-v] ifname(s)

     ifwatchd is used to monitor dynamic interfaces (for example PPP inter-
     faces) for address changes.  Sometimes these interfaces are accompanied
     by a daemon program, which can take care of running any necessary scripts
     (like pppd(8) or isdnd(8)), but sometimes the interfaces run completely
     autonomously (like pppoe(8)).

     ifwatchd provides a generic way to watch this type of changes.  It works
     by monitoring the routing socket and interpreting `RTM_NEWADDR' (address
     added) and `RTM_DELADDR' (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 ifwatchd is run.

     The following options are available:

     -d down-script
             Specify the command to invoke on ``interface down'' events (or:
             deletion of an address from an interface).

     -h      Show the synopsis.

     -i      Inhibit a call to the up-script on startup for all watched inter-
             faces already marked up. If this option is not given, ifwatchd
             will check all watched interfaces on startup whether they are al-
             ready marked up and, if they are, call the up-script with appro-
             priate parameters.

             Since ifwatchd typically is started late in the system boot se-
             quence, some of the monitored interfaces may already have come up
             when it finally starts, but their up-scripts have not been
             called. By default ifwatchd calls them on startup to account for
             this (and make the scripts easier.)

     -u up-script
             Specify the command to invoke on ``interface up'' events (or: ad-
             dition of an address to an interface).

     -v      Output verbose progress messages and flag errors ignored during
             normal operation.

             The name of the interface to watch.  Multiple interfaces may be
             specified.  Events for other interfaces are ignored.

           # ifwatchd -u /etc/ppp/ip-up -d /etc/ppp/ip-down pppoe0

     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:

           #! /bin/sh
           /sbin/route add default $5

     As described below the fifth command line parameter will contain the peer
     address of the pppoe link. The corresponding ip-down script is:

           #! /bin/sh
           /sbin/route delete default $5

     Note that this is not a good idea if you have pppoe0 configured to con-
     nect only on demand (via the link1 flag), but works well for all perma-
     nent connected cases. Use

           ! /sbin/route add default -iface

     in your /etc/ifconfig.pppoe0 file in the on-demand case.

     The invoked scripts get passed these parameters:

     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).

     tty          Dummy parameter for compatibility with pppd(8) which will
                  always be /dev/null.

     speed        Dummy parameter for compatibility with pppd(8) which will
                  always be 9600.

     address      The new address if this is an up event, or the no longer
                  valid old address if this is a down event.

                  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.

     destination  For point to point interfaces, this is the remote address of
                  the interface.  For other interfaces it is the broadcast ad-

     route(4), ifconfig.if(5), pppoe(8), rc.d(8), route(8)

     The ifwatchd utility appeared in NetBSD 1.6.

     The program was written by Martin Husemann <martin@netbsd.org>.

NetBSD 1.6                     September 2, 2001                             2

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