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Bridging between user processes

Bridge Derek Smalls 1 participant 1 message Jun 16, 2004 1 message not in the archive Ethernet bridge

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Thanks for the response!

Running the application produces the same result (no result actually) as ping -I. Looks like tcpdump can see the tap interfaces: tcpdump on tap4 can see outgoing pings sent out on tap4. Moreover, I can send pings through the bridge and tcpdump on tap4 picks them up.

I guess in order to bridge between taps I really do need a separate utility that would copy frames between /dev/tap4 and /dev/tap5 .

Quoted 32 lines · --- "John W. Linville
Quoted 9 lines · Derek Smalls

I then do a ping over tap4:

Quoted 1 line

ping -I tap4 8.8.8.8

and tcpdump on tap5:

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tcpdump -i tap5

and see nothing. Shouldn't I see the ping requests

on

Quoted 1 line

tap5 now?

My guess is that your ping -I is completely bypassing the bridging
code. I haven't looked at it lately, but I'd guess that the bridging
functionality is geared toward receiving frames on the "slave" interface
and transmitting frames through the "master" interface. You example is
transmitting on the "slave" interface (to use my terminology).

A better test would be to setup your bridge, then start the application
you mentioned on the transmitting side and monitor the other side for
traffic (probably with another instance of your application).

Quoted 8 lines

BTW, I don't think tcpdump will be useful. You'll need something that
is "tap-aware".

Good luck!

John

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