.PP
Allows you to check interface states. First, an interface needs to be selected
for comparison. Exactly one option of the following three must be specified:
.TP
\fB\-\-iface\fP \fIname\fP
Check the states on the given interface.
.TP
\fB\-\-dev\-in\fP
Check the states on the interface on which the packet came in. If the input
device is not set, because for example you are using \-m iface in the OUTPUT
chain, this submatch returns false.
.TP
\fB\-\-dev\-out\fP
Check the states on the interface on which the packet will go out. If the
output device is not set, because for example you are using \-m iface in the
INPUT chain, this submatch returns false.
.PP
Following that, one can select the interface properties to check for:
.TP
[\fB!\fP] \fB\-\-up\fP, [\fB!\fP] \fB\-\-down\fP
Check the UP flag.
.TP
[\fB!\fP] \fB\-\-broadcast\fP
Check the BROADCAST flag.
.TP
[\fB!\fP] \fB\-\-loopback\fP
Check the LOOPBACK flag.
.TP
[\fB!\fP] \fB\-\-pointtopoint\fP
Check the POINTTOPOINT flag.
.TP
[\fB!\fP] \fB\-\-running\fP
Check the RUNNING flag. Do NOT rely on it!
.TP
[\fB!\fP] \fB\-\-noarp\fP, [\fB!\fP] \fB\-\-arp\fP
Check the NOARP flag.
.TP
[\fB!\fP] \fB\-\-promisc\fP
Check the PROMISC flag.
.TP
[\fB!\fP] \fB\-\-multicast\fP
Check the MULTICAST flag.
.TP
[\fB!\fP] \fB\-\-dynamic\fP
Check the DYNAMIC flag.
.TP
[\fB!\fP] \fB\-\-lower\-up\fP
Check the LOWER_UP flag.
.TP
[\fB!\fP] \fB\-\-dormant\fP
Check the DORMANT flag.