New: Multicast packets with TTL 0 sent out if not local listener

Bugme-new Andrew Morton 1 participant 1 message Nov 27, 2008 1 message not in the archive

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Andrew Morton

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2008-11-27 17:34 UTC #1 lore raw

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Quoted 29 lines · On Thu, 27 Nov 2008 02:32:27 -0800 (PST) [email protected] wrote:

http://bugzilla.kernel.org/show_bug.cgi?id=12109
           Summary: Multicast packets with TTL 0 sent out if not local
                    listener
           Product: Networking
           Version: 2.5
     KernelVersion: 2.6.27
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: IPV4
        AssignedTo: [email protected]
        ReportedBy: [email protected]
According to what I have read, setting the IP_MULTICAST_TTL option to 0 on a multicast sending socket should prevent it sending to the network, and be destined only for listeners on the local computer.
This only seems to work if there is a local listener on that particular group. If such a listener app is stopped other computers on the LAN get the messages, and tcpdump -v shows they have TTL 0
I am not sure if this is intended behaviour but it is unexpected.