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Message-ID: <4C855385.7030203@ans.pl> Date: Mon, 06 Sep 2010 22:48:05 +0200 From: Krzysztof Olędzki <ole@....pl> To: Eric Dumazet <eric.dumazet@...il.com> CC: netdev@...r.kernel.org Subject: Re: 2.6.34: Problem with UDP traffic on lo + poll(?) On 2010-09-06 22:44, Krzysztof Olędzki wrote: > On 2010-09-06 22:29, Eric Dumazet wrote: >> Le lundi 06 septembre 2010 à 21:55 +0200, Krzysztof Olędzki a écrit : >> >>> Yes, conntrack is one of possibilities. However, this problem only >>> manifests on 2.6.34 and never on 2.6.31 where iptables and conntrack >>> configurations are identically. And of course, each time it is a >>> different port. >>> >>> Please also note that this problem only exists when communication is >>> handled over a loopback interface - I'm not able to trigger this from a >>> remote host even if I run the test on two hosts (local& remote) >>> simultaneously. >>> >> >> No particular error shown in "netstat -s" ? > > No... :( > > Udp: > 8542243 packets received > 489605 packets to unknown port received. > 1 packet receive errors > 4254527 packets sent > RcvbufErrors: 1 > >> port randomization on UDP changed in the past, and conntracking changed >> a bit too ;) > > I know but AFAIR all important changs were alredy included in 2.6.31. > And again: there is no problem in quering DNS from a remote host: > [client 2.6.24.6]<-ethernet-> [server 2.6.34.6] > > BTW: I have been able to reproduce this problem on a different, less > critical host after upgrading its kernel to 2.6.34.6. Unfortunately I'm > still not able to do in on my lab environment. :( Anyway, I'll try to > catch "conntrack -E" output and see what conntrack thinks about such > packets. OK, got it: *strace (1682.t.lan): socket(PF_INET, SOCK_DGRAM|SOCK_NONBLOCK, IPPROTO_IP) = 4 connect(4, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("192.168.130.53")}, 28) = 0 poll([{fd=4, events=POLLOUT}], 1, 0) = 1 ([{fd=4, revents=POLLOUT}]) sendto(4, "Gz\1\0\0\1\0\0\0\0\0\0\0041683\1t\3lan\0\0\1\0\1", 28, MSG_NOSIGNAL, NULL, 0) = 28 poll([{fd=4, events=POLLIN}], 1, 5000) = 0 (Timeout) poll([{fd=4, events=POLLOUT}], 1, 0) = 1 ([{fd=4, revents=POLLOUT}]) * tcpdump: 1283805361.395859 IP (tos 0x0, ttl 64, id 47011, offset 0, flags [DF], proto UDP (17), length 56) 192.168.130.53.49279 > 192.168.130.53.53: 27611+ A? 1682.t.lan. (28) 1283805361.395933 IP (tos 0x0, ttl 64, id 10738, offset 0, flags [none], proto UDP (17), length 112) 192.168.130.53.53 > 192.168.130.53.49279: 27611* 1/1/1 1682.t.lan. A 127.0.0.1 (84) * conntrack: [1283805361.395862] [NEW] ipv4 2 udp 17 30 src=192.168.130.53 dst=192.168.130.53 sport=49279 dport=53 [UNREPLIED] src=192.168.130.53 dst=192.168.130.53 sport=53 dport=49279 id=3423125776 [1283805361.395939] [UPDATE] ipv4 2 udp 17 30 src=192.168.130.53 dst=192.168.130.53 sport=49279 dport=53 src=192.168.130.53 dst=192.168.130.53 sport=53 dport=49279 id=3423125776 Pozdrawiam, Krzysztof Olędzki -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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