bpf does not see packets forwarded with ipfw fwd

[Eugene Grosbein]

On Sat, Apr 12, 2008 at 07:10:38PM +0100, Robert Watson wrote:

> If you ping from host A to host B, does tcpdump see both the ICMP echo 
> request and reply on both boxes?  In principle, ipfw fwd uses the same 
> output paths as the rest of the IP stack, so it would be useful to know 
> whether it sees other outbound traffic properly or not.

Yes, it does. It sees oubound traffic that is not processed with 'ipfw fwd'.
That's so funny:

1) A has IP 10.58.0.2/24 and B has. 10.58.0.1/24. From A, I start to
ping 10.58.0.1, tcpdump shows requests and replys.
2) I add a rule: "ipfw add 5 fwd 10.58.0.1 from any to 10.58.0.1"
ping contiunes to run Ok, ipfw shows that rule maches packes
(counters increase) but now tcpdump shows only replies. No request.
Very funny.

Eugene Grosbein