bpf does not see packets forwarded with ipfw fwd

[Alireza Torabi]

Is BIOCFEEDBACK set?


On Sat, Apr 12, 2008 at 7:22 AM, Eugene Grosbein <eugen at kuzbass.ru> wrote:
> Hi!
>
>  One of 7.0 users has reported in some cyrillic newsgroup
>  a problem that I have reproduced in my 7.0-STABLE system.
>  That is: tcpdump does not show locally originated outgoing IP packets
>  that were processed by 'ipfw fwd' rule. The same configuration presents
>  no problems with 6.3-STABLE.
>
>  Consider simple schema: two FreeBSD boxes (A and B) directly connected
>  with ethernet intefaces. The box A has another ethernet interface and uses
>  "ipfw fwd" as its very first ipfw rule to forward some packets to B,
>  while these packets would normally go out trough mentioned another
>  interface. Now, tcpdump does NOT show outgoing packets but host B also
>  runs tcpdump on its incoming interface and does see them.
>
>  I double-checked all paramerets for tcpdump, all routing tables.
>  I even connected A and B with cross-over ethernet cable, without a switch.
>  Still, B sees incoming packets coming over the cable and A does not see
>  them leaving. This bothers me a bit :-)
>
>  Eugene Grosbein
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