[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] (repeatable) cross-domain networking failure
Maybe add some tracing to the backend driver -- it's possible the backend isn't sending responses for those packets back to domU, and so things seize up for a while. If no responses are being generated it is because the backend thinks the packets are still in flight, so there would be some bug-hunting to find out why that is. -- Keir > > Summary: > > After sending some UDP traffic between two xen domains (Domain 0 and > Domain 1) the networking between the domains fails. This failure is 100% > repeatable. > > In more detail: > > I have two xen domains. They run the kernels from the 2.0.3 release. (I've > run > into the same problem with 2.0.1 as well.) Domain 0 has 5 physical ethernet > interfaces, and a virtual interface to Domain 1. Domain 1 has just the > virtual > interface to Domain 0. > > D0 is configured with IP address 192.168.0.1, and D1 with 192.168.1.1. The > netmask is set to 255.255.0.0. > > When I bring up D1, I can ping D1 from D0, ssh into D1, etc. > > I then start a UDP server in D0, and a traffic generator in D1. After the > traffic generator sends its 128-th packet, networking between the domains > fails. The 128th packet is received successfully by the UDP server, but no > later traffic arrives in D0. This includes UDP, TCP, ICMP, and ARP. > > Looking at the interrupt counts in /proc/interrupts, I see that D0 no longer > receives packets sent by D1. D1, however, does receive packets sent by D0. > (To > be clear, D0->D1 traffic is ICMP ping requests, unrelated to the UDP traffic. > There is not UDP traffic sent from D0 to D1.) > > (I suspect the stuff in this paragraph doesn't matter, but include it for > completeness.) Eventually, D0's ARP cache entry for D1 expires. D0 ARPs for > D1, > and D1 replies. But D0 never receives these replies. And eventually, D1 stops > replying to the ARPs entirely. (D1's sending behavior is observed via tcpdump > running in the console connection to D1.) > > Note that the networking failure only occurs if the UDP packets are delivered > to a user-level process in D0. In particular, UDP traffic to D0's kernel NFS > server does not induce the failure. Nor does traffic sent to D0 for which > there > is no user process to accept the packets. And neither does traffic which is > forwarded on to other hosts via NAT. (I haven't tested the regular forwarding > case.) > > Also, for what it's worth, Domain 0's network connectivity on its other > interfaces (which are connected to the world at large) are unaffected. > > Looking through the mailing list archive, I saw a prior bug that seemed > similar, but involved IP fragmentation. That is not the case here, as the UDP > packets sent by D1 are small (<100 bytes). > > Any suggestions for debugging this? > > Thanks, > mukesh > > > ------------------------------------------------------- > The SF.Net email is sponsored by: Beat the post-holiday blues > Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. > It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.sourceforge.net/lists/listinfo/xen-devel > ------------------------------------------------------- The SF.Net email is sponsored by: Beat the post-holiday blues Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/xen-devel
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