Re: LibIPQ issue

["Sérgio Bernardino" <sergio.bernardino@gmail.com>]

On Mon, 07 Mar 2005 14:10:03 +0100, Patrick McHardy <kaber@trash.net> wrote:
> Sérgio Bernardino wrote:
> >
> > iptables -t filter -A OUTPUT -p ip -j QUEUE
> >
> > I can alter the destination address of the outgoing packet (for
> > example, a packet that goes from A to B becomes a packet that goes
> > from A to A, a localhost packet), and it all works fine.
> > I seems like i'm doing something wrong but i can't quite figure out
> > what. Any ideas?
> 
> Packets in LOCAL_OUT are manually rerouted by ip_queue. Packets
> mangled in PRE_ROUTING should be routed correctly according to
> the data contained in the new packet. Could it be that you are
> testing on loopback ?
> 
> Regards
> Patrick
> 

I've always tested it with two or three different machines and the
only rerouting that always worked was the one that occurred when i
changed packet caught in LOCAL_OUT. Curiously enough the packet that i
mangle in PRE_ROUTING seems to disappear. It doesn't "show" on the
current machine (machine B, according to my previous example), on the
intended machine (machine C) and i can't seem to track it with tcpdump
after i committed the changes and ACCEPTed the packet.
The example i gave with LOCAL_OUT rerouting a packet to make it seem
like it's a localhost packet is just that, an example. In fact, i can
reroute packets intended to a machine so that they show up on another
one by changing them in LOCAL_OUT. It works fine. But since you say
that that ip_queue manually reroutes the packets, the situation is
clearly different from what occurs in PRE_ROUTING. I pretty certain
that the information is modified correctly. In fact, the code i use to
change packets caught in PRE_ROUTING is virtually identical to the
code i use to change packets caught in LOCAL_OUT. So, basically, i'm
quite unsure of what's exactly wrong. Specially since you've confirmed
that it should work.
Thank you for your time.

-- 
Sérgio Bernardino

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