"me" in ipfw rules - does it include aliases?

Nikos Vassiliadis nvass9573 at gmx.com
Tue Sep 8 06:59:06 UTC 2009

Tom Worster wrote:
> the ipfw man page says:
>   me   matches any IP address configured on an interface in the system.
> which suggests that if i code my rules using "me" then when i add an alias
> ip address to an interface with ifconfig, these "me" rules will immediately
> work for the newly added address as they do for other addresses.

> is that correct?

Yes, the "me" keyword is expanded to whatever IP address is
assigned on any interface in the system. It's updated whenever
an IP address is added to or removed from an interface. Use the
simple ruleset bellow to test it yourself:

lab# ipfw list
00100 allow ip from me to me
65535 deny ip from any to any

add alias & ping alias => success
remove alias & ping alias => failure

It's a really useful keyword, yet it's not panacea. When
using it, one has to think the possibility of an attacker
who uses "me" addresses. Use some interface checking as
well in your ruleset...


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