Re: Bug#10955: with IP masquerading, tcpdump doesn't show what's on the wire (fwd)
Eric.Schenk@dna.lth.se
Wed, 02 Jul 1997 03:52:35 +0200
Phil Karn <karn@ka9q.ampr.org> writes:
>When running tcpdump on an interface when IP masquerading is in
>use, tcpdump doesn't necessarily show the packet as it appears
>on the wire.
>
>In particular, incoming packets are displayed after the destination
>IP address and TCP port number have been translated back to their
>local values. On the other hand, masqueraded outbound packets are
>shown correctly, after translation to external form.
>
>If the purpose of tcpdump is to show what is actually being sent or
>received on the specified interface, then the behavior on incoming
>packets is arguably incorrect.
Ah. Yes. This one is a bit sticky. It should be possible to fix this,
but it will be a bit delicate. I'll try to look at this tomorrow.
Perhaps I can put it into the next 2.0.31 prepatch. In either
case I'll try to get a test patch to you.
--
Eric Schenk www: http://www.dna.lth.se/~erics
Dept. of Comp. Sci., Lund University email: Eric.Schenk@dna.lth.se
Box 118, S-221 00 LUND, Sweden fax: +46-46 13 10 21 ph: +46-46 222 96 38