2.4.22 multicast address problem, pcap workaround
From: Dominic Robinson (d.robinson_at_videonetworks.com)
Date: Fri, 19 Sep 2003 09:11:54 +0100 To: firstname.lastname@example.org
Please cc to email@example.com
My source machine sends multicast packets on all the following
addresses: 220.127.116.11, 18.104.22.168 through to 22.214.171.124
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 126.96.36.199 and 188.8.131.52.
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?
(1) 184.108.40.206 to 220.127.116.11 and 18.104.22.168 to 22.214.171.124
has the same problem.
(2) 126.96.36.199 to 188.8.131.52 works
(3) 184.108.40.206 to 220.127.116.11 fails with slightly different
(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,
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