Subject: 2.6.32 and Multicast group membership

From: "Mr. Berkley Shands" <[email-masked]>
Date: Tue, 01 Jun 2010 16:39:00 -0500

starting in 2.6.32, my multicast connections stop getting data after 
60-100 seconds.
The identical user code works fine under 2.6.22 through 2.6.31.

The NIC (an intel 82586) has two ports on the same subnet
(eth0 at 172.16.21.55/24 and eth1 at 172.16.21.56/24)

      if (setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char*)&req, 
sizeof(req)))
      {
         perror("setsockopt IP_ADD_MEMBERSHIP failed");
         ::exit(-1);
      }

If I do ADD_MEMBERSHIP on just one of these interfaces, the sockets 
still get data.
But if I join on both interfaces, one or both will stop getting packets
after 60-100 seconds. Sniffing with tcpdump shows the Cisco layer 3 switch
is not getting its responses back to keep the multicast group open.
The HP layer 2 switch does not seem to care, it keeps the data flowing 
regardless
of which physical port the join is executed on.

Changing IP_MULTICAST_ALL has no effect :-(
Did I miss something? New code that I have to specify to keep the Cisco 
happy?

tia

Berkley

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// E. F. Berkley Shands, MSc//

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