Messages in this thread | ![/](/images/icornerl.gif) | | Date | Fri, 19 Sep 2003 09:11:54 +0100 | From | Dominic Robinson <> | Subject | 2.4.22 multicast address problem, pcap workaround |
| |
Please cc to d.robinson@videonetworks.com
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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| ![\](/images/icornerr.gif) |