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NetBSD 6.1.5 - man page for ifwatchd (netbsd section 8)

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

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

     ifwatchd [-hiqv] [-A arrival-script] [-c carrier-script] [-D departure-script]
	      [-d down-script] [-u up-script] [-n no-carrier-script] ifname(s)

     ifwatchd 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 pppd(8) or isdnd(8)), but sometimes the interfaces run completely autonomously (like

     ifwatchd provides a generic way to watch these types of changes.  It works by monitoring the
     routing socket and interpreting 'RTM_NEWADDR' (address added), 'RTM_DELADDR' (address
     deleted) and 'RTM_IFINFO' (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 ifwatchd is run.

     The following options are available:

     -A arrival-script
	     Specify the command to invoke on arrival of new interfaces (like PCMCIA cards).

     -c carrier-script
	     Specify the command to invoke when the carrier status transitions from no carrier to

     -D departure-script
	     Specify the command to invoke when an interface departs (for example a PCMCIA card
	     is removed.)

     -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 interfaces already marked
	     up.  If this option is not given, ifwatchd 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,
	     ifwatchd will run the carrier script.

	     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 ifwatchd calls them on startup to account
	     for this (and make the scripts easier.)

     -n no-carrier-script
	     Specify the command to invoke when the carrier status transitions from carrier to no

     -q      Be quiet and don't log non-error messages to syslog.

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

     -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.  You do
	     not want to use this option in /etc/rc.conf!

	     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
	   /sbin/route add -inet6 default fe80::2 -iface ifp $1

     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
	   /sbin/route delete -inet6 default fe80::2

     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

	   ! /sbin/route add default -iface

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

     The next example is for dhclient users.

	   # ifwatchd -i -c /etc/dhcp/carrier-detect tlp0

     With the above command, the carrier-detect script will be invoked when a carrier is detected
     on the interface tlp0.  Note that the -i flag prevents any action based on the initial
     state.  A script like the following should work for most users, although it will not work
     for machines with multiple interfaces running dhclient.

	   #! /bin/sh
	   # Arguments:  ifname tty speed address destination
	   # If there is a dhclient already running, kill it.
	   # (This step could be put in a distinct no-carrier script,
	   # if desired.)
	   if [ -f /var/run/dhclient.pid ]; then
		  /bin/kill `/bin/cat /var/run/dhclient.pid`
	   # Start dhclient again on this interface
	   /sbin/dhclient $1

     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 address.

     The program logs to the syslog daemon as facility ``daemon''.  For detailed debugging use
     the -v (verbose) option.

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

     The ifwatchd utility appeared in NetBSD 1.6.

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

     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.

BSD					  April 16, 2010				      BSD

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