2.4.22 multicast address problem, pcap workaround
From: Dominic Robinson
Date: Fri Sep 19 2003 - 03:07:30 EST
Please cc to d.robinson@xxxxxxxxxxxxxxxxx
My source machine sends multicast packets on all the following
addresses: 230.1.1.1, 230.1.1.2 through to 230.1.1.64
My target machine (on local network, or with cross-over cable)
joins all these multicast groups, and receives packets on all
of these addresses EXCEPT 230.1.1.18 and 230.1.1.32.
However, if I run tcpdump at the same time as my program, I
find my program suddenly starts receiving on 230.1.1.[18,32]
If I kill tcpdump, my program stops receiving. It's the
"pcap_open_live()" function in tcpdump which causes this,
and as a workaround I just call it direct in my receiver.
Could this be a bug in the multicast kernel code?
NOTES:
(1) 230.1.1.1 to 230.1.64.1 and 230.1.1.1 to 230.64.1.1
has the same problem.
(2) 230.1.1.1 to 230.1.1.63 works
(3) 230.1.1.1 to 230.1.1.128 fails with slightly different
behaviour
(4) It makes no difference if I run a single program
listening on all addresses, or 64 individual programs
each listening on a single address.
Thanks and regards,
Dominic
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/