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:

--iface name
    Check the states on the given interface.

--dev-in
    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.

--dev-out
    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.

Following that, one can select the interface properties to check for:

[!] --up, [!] --down
    Check the UP flag.

[!] --broadcast
    Check the BROADCAST flag.

[!] --loopback
    Check the LOOPBACK flag.

[!] --pointtopoint
    Check the POINTTOPOINT flag.

[!] --running
    Check the RUNNING flag. Do NOT rely on it!

[!] --noarp, [!] --arp
    Check the NOARP flag.

[!] --promisc
    Check the PROMISC flag.

[!] --multicast
    Check the MULTICAST flag.

[!] --dynamic
    Check the DYNAMIC flag.

[!] --lower-up
    Check the LOWER_UP flag.

[!] --dormant
    Check the DORMANT flag.