Question about pcap_send

[Calum <caluml () gmail com>]

Hello all,

I'm hoping that someone on this list can help, as I've run out of ideas.

I am using Java with jpcap which I believe hooks into libpcap.
(This one - http://netresearch.ics.uci.edu/kfujii/jpcap/doc/index.html,
not the SF project of the same name).

I am capturing packets by sniffing on a dummy interface on a Linux
machine, and transporting them to a second machine, where I write them
out on the dummy interface on that machine.
(The transport doesn't mangle the packets in any way.)
A sort of tunnel, if you like.

The problem is this:

If, say, the dummy interface on the receiving machine is configured as
1.1.1.1, and the packet has src=1.2.3.4, dst=1.1.1.1, when it is
written out onto that interface, nothing happens with it.
I can see it in tcpdump -npi dummy0, but if it's an ICMP echo request
packet, the receiving machine doesn't seem to "process" it - i.e. I
can't see an ICMP echo reply going anywhere.

I assume either a: I'm doing something wrong, or b: this is the
expected behaviour.

Any light shed upon this would be gratefully received.
Please let me know if you need more information.

C
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