Red Hat Bugzilla – Bug 437937
udp packet duplication in localhost with multicast sendto()
Last modified: 2009-03-23 07:11:20 EDT
Description of problem:
UDP Packet duplication occurs when sendto() called within many process
at the same time. each processes are joined to different multicast addr,port.
ratio of duplication is around 0.6%-2.0% of all sent packet per 1 addr.
(verified by tcpdump)
Version-Release number of selected component (if applicable):
Linux xxxxxxx 2.6.9-5.EL #1 Wed Jan 5 19:21:57 EST 2005 x86_64 x86_64 x86_64
As the number of the processes increases, the packet repetition rate rises.
Steps to Reproduce:
1.send multicast packet with sendto().
2.capture any multicast group with tcpdump
when 20 process startup, each process sent 10000 udp packet.
captured 1 multicast addr with tcpdump, and received 10003packet.
3 packets was the same one sent just before.
it never happen if sendto() called sequential.
I'm going to set up a system to reproduce this. In the interim, if you have a
copy of the tcpdump that you captured for me to review, that would be helpful.
ping, any word on that tcpdump?
closing, no response