ifwatchd(8) - NetBSD Manual Pages

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


NAME
ifwatchd - watch for addresses added to or deleted from interfaces and call up/down-scripts for them
SYNOPSIS
ifwatchd [-d down-script] [-h] [-i] [-u up-script] [-v] ifname(s)
DESCRIPTION
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. ifname(s) The name of the interface to watch. Multiple interfaces may be specified. Events for other interfaces are ignored.
EXAMPLES
# 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 0.0.0.1 in your /etc/ifconfig.pppoe0 file in the on-demand case.
PARAMETERS PASSED TO SCRIPTS
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- dress.
SEE ALSO
route(4), ifconfig.if(5), pppoe(8), rc.d(8), route(8)
HISTORY
The ifwatchd utility appeared in NetBSD 1.6.
AUTHORS
The program was written by Martin Husemann <martin@netbsd.org>. NetBSD 1.6 September 2, 2001 2
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