Date: Sat, 7 Jul 2007 18:25:51 +1000 (EST) From: Ian Smith <smithi@nimnet.asn.au> To: Dave McCammon <davemac11@yahoo.com> Cc: stable@freebsd.org Subject: Re: ipfw with if_bridge oddity Message-ID: <Pine.BSF.3.96.1070707180324.4516A-100000@gaia.nimnet.asn.au> In-Reply-To: <868934.77972.qm@web32811.mail.mud.yahoo.com>
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On Fri, 6 Jul 2007, Dave McCammon wrote:
> I can't seem to grasp why this is working differently.
> FreeBSD 6.2 using ipfw + if_bridge
>
> LAN -- em1(if_bridge + ipfw)em0 -- internet
>
> I am at xx.xx.16.6 and try to ping say www.yahoo.com
>
> in ruleset:
> 1100 allow icmp from any to xx.xx.16.0/27{1-10,13,14,19,22,23} icmptypes 0,3,11,12,13,14
> 2100 allow ip from xx.xx.16.0/27 to any in via em1
Seeing noone more knowledgeable has had a go, and with the caveat that
I've never setup an if_bridge(4) but still maintain a bridge(4)+ipfw ..
Rule 2100 lets your ping in, and 1100 allows the response (in and out)
> gets dropped by following rule as shown in logs:
>
> 4700 deny log ip from any to any
>
> Log entry: ipfw: 4700 Deny ICMP:8.0 xx.xx.16.6 69.147.114.210 out via em0
Denied because you have no rule letting it go out, it seems.
> If I add this rule all works great:
>
> 2101 allow icmp from xx.xx.16.0/27 to any recv em1
Which allows it both in and out (neither specified)
> Why would the "recv em1" work and the "in via em1" get blocked?
>
> I just changed from using bridge(4) to if_bridge using the same ruleset.
Only inbound bridged packets are passed to ipfw from bridge(4) .. once
allowed in, they go out. My reading of if_bridge(4) suggests that ipfw
(etc) may also be examining outbound bridged packets, depending on the
sysctls. How have you got the sysctls mentioned in if_bridge(4) set?
> The rest of my ruleset seems to be working fine but this problem is causing me a little paranoia
> about the effectiveness of the firewall.
>
> Also, should I still be seeing "deny (snip) in via bridge0" messages in by logs
> if I have this set "net.link.bridge.pfil_bridge: 0"?
Dunno.
Cheers, Ian
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