IFWATCHD(8) | NetBSD System Manager's Manual | IFWATCHD(8) |
ifwatchd | [-hiqv] [-A arrival-script] [-c carrier-script] [-D departure-script] [-d down-script] [-u up-script] [-n no-carrier-script] ifname(s) |
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:
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.)
# 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 0.0.0.1
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` fi # Start dhclient again on this interface /sbin/dhclient $1
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.
April 16, 2010 | NetBSD 5.99 |