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Date: Fri, 18 Nov 2011 14:38:57 +0100 From: Pozsár Balázs <pozsy@...linux.hu> To: Eric Dumazet <eric.dumazet@...il.com> CC: Sven-Haegar Koch <haegar@...net.de>, Linux-Kernel-Mailinglist <linux-kernel@...r.kernel.org>, Tamási János <janusz@...linux.hu>, netdev@...r.kernel.org Subject: Re: routing bug? On 2011-11-18 14:33, Eric Dumazet wrote: > Le vendredi 18 novembre 2011 à 14:23 +0100, Pozsár Balázs a écrit : > >> On 2011-11-18 14:09, Eric Dumazet wrote: >> >>> Le vendredi 18 novembre 2011 à 13:48 +0100, Sven-Haegar Koch a écrit : >>> >>> >>>> Added netdev list to CC:, there you should have a higher chance of a >>>> usefull answer. >>>> >>>> On Fri, 18 Nov 2011, Pozsár Balázs wrote: >>>> >>>> >>>> >>>>> Hi all, >>>>> >>>>> I have been struggling with this not easily reproducible issue since a while. >>>>> I am using linux kernel v3.1.0, and sometimes routing to a few IP addresses >>>>> does not work. What seems to happen is that instead of sending the packet to >>>>> the gateway, the kernel treats the destination address as local, and tries to >>>>> gets its MAC address via ARP. >>>>> >>>>> For example, now my current IP address is 172.16.1.104/24, the gateway is >>>>> 172.16.1.254: >>>>> >>>>> |# ifconfig eth0 eth0 Link encap:Ethernet HWaddr 00:1B:63:97:FC:DC >>>>> inet addr:172.16.1.104 Bcast:172.16.1.255 Mask:255.255.255.0 >>>>> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 >>>>> RX packets:230772 errors:0 dropped:0 overruns:0 frame:0 >>>>> TX packets:171013 errors:0 dropped:0 overruns:0 carrier:0 >>>>> collisions:0 txqueuelen:1000 >>>>> RX bytes:191879370 (182.9 Mb) TX bytes:47173253 (44.9 Mb) >>>>> Interrupt:17 >>>>> >>>>> # route -n >>>>> Kernel IP routing table >>>>> Destination Gateway Genmask Flags Metric Ref Use Iface >>>>> 0.0.0.0 172.16.1.254 0.0.0.0 UG 0 0 0 eth0 >>>>> 172.16.1.0 0.0.0.0 255.255.255.0 U 1 0 0 eth0 >>>>> | >>>>> >>>>> I can ping a few addresses, but not 172.16.0.59: >>>>> >>>>> |# ping -c1 172.16.1.254 >>>>> PING 172.16.1.254 (172.16.1.254) 56(84) bytes of data. >>>>> 64 bytes from 172.16.1.254: icmp_seq=1 ttl=64 time=0.383 ms >>>>> >>>>> --- 172.16.1.254 ping statistics --- >>>>> 1 packets transmitted, 1 received, 0% packet loss, time 0ms >>>>> rtt min/avg/max/mdev = 0.383/0.383/0.383/0.000 ms >>>>> root@...sybook:~# ping -c1 172.16.0.1 >>>>> PING 172.16.0.1 (172.16.0.1) 56(84) bytes of data. >>>>> 64 bytes from 172.16.0.1: icmp_seq=1 ttl=63 time=5.54 ms >>>>> >>>>> --- 172.16.0.1 ping statistics --- >>>>> 1 packets transmitted, 1 received, 0% packet loss, time 0ms >>>>> rtt min/avg/max/mdev = 5.545/5.545/5.545/0.000 ms >>>>> root@...sybook:~# ping -c1 172.16.0.2 >>>>> PING 172.16.0.2 (172.16.0.2) 56(84) bytes of data. >>>>> 64 bytes from 172.16.0.2: icmp_seq=1 ttl=62 time=7.92 ms >>>>> >>>>> --- 172.16.0.2 ping statistics --- >>>>> 1 packets transmitted, 1 received, 0% packet loss, time 0ms >>>>> rtt min/avg/max/mdev = 7.925/7.925/7.925/0.000 ms >>>>> root@...sybook:~# ping -c1 172.16.0.59 >>>>> PING 172.16.0.59 (172.16.0.59) 56(84) bytes of data. >>>>> From 172.16.1.104 icmp_seq=1 Destination Host Unreachable >>>>> >>>>> --- 172.16.0.59 ping statistics --- >>>>> 1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms >>>>> | >>>>> >>>>> When trying to ping 172.16.0.59, I can see in tcpdump that an ARP req was >>>>> sent: >>>>> >>>>> |# tcpdump -n -i eth0|grep ARP >>>>> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode >>>>> listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes >>>>> 15:25:16.671217 ARP, Request who-has 172.16.0.59 tell 172.16.1.104, length 28 >>>>> | >>>>> >>>>> and /proc/net/arp has an incomplete entry for 172.16.0.59: >>>>> >>>>> |# grep 172.16.0.59 /proc/net/arp >>>>> >>>>> 172.16.0.59 0x1 0x0 00:00:00:00:00:00 * eth0 >>>>> | >>>>> >>>>> Please note, that 172.16.0.59 /is/ accessible from this LAN from other >>>>> computers. >>>>> >>>>> >>>>> Does anyone have any idea of what's going on? Thanks, >>>>> >>>>> >>>>> Balazs Pozsar >>>>> >>>>> ps: I think it is related to this one: https://lkml.org/lkml/2011/11/16/292 >>>>> >>>>> -- >>>>> >>>>> >>> Could you send us result of : >>> >>> ip route get 172.16.0.59 >>> ip route list cache match 172.16.0.59 >>> >>> >> I did not tell you in my first mail, that some times different hosts are >> reachable and unreachable. I will try to not confuse you :) >> As of now, 172.16.0.59 is OK, and 172.16.0.37 is NOT OK. >> Also, 172.16.0.64 is OK now, and 172.16.0.42 is NOT OK now. >> >> The two commands you have requested give the following output for these >> IP addresses: >> >> These are OK: >> >> # ip route get 172.16.0.64 >> 172.16.0.64 via 172.16.1.254 dev eth0 src 172.16.1.22 >> cache >> # ip route get 172.16.0.59 >> 172.16.0.59 via 172.16.1.254 dev eth0 src 172.16.1.22 >> cache >> >> These are NOT OK: >> >> # ip route get 172.16.0.37 >> 172.16.0.37 dev eth0 src 172.16.1.22 >> cache<redirected> ipid 0x97a4 >> # ip route get 172.16.0.42 >> 172.16.0.42 dev eth0 src 172.16.1.22 >> cache<redirected> ipid 0x0d21 >> >> These are OK: >> >> # ip route list cache match 172.16.0.59 >> 172.16.0.59 via 172.16.1.254 dev eth0 src 172.16.1.22 >> cache >> # ip route list cache match 172.16.0.64 >> 172.16.0.64 via 172.16.1.254 dev eth0 src 172.16.1.22 >> cache >> >> These are NOT OK: >> >> # ip route list cache match 172.16.0.37 >> 172.16.0.37 dev eth0 src 172.16.1.22 >> cache<redirected> ipid 0x97a4 >> 172.16.0.37 from 172.16.1.22 dev eth0 >> cache<redirected> ipid 0x97a4 >> 172.16.0.37 from 172.16.1.22 dev eth0 >> cache<redirected> ipid 0x97a4 >> # ip route list cache match 172.16.0.42 >> 172.16.0.42 dev eth0 src 172.16.1.22 >> cache<redirected> ipid 0x0d21 >> 172.16.0.42 from 172.16.1.22 dev eth0 >> cache<redirected> ipid 0x0d21 >> >> >> How can I fix this? >> >> Thanks! >> > We are working on it (see threads in netdev) > > You can in the meantime > > echo 0>/proc/sys/net/ipv4/conf/eth0/accept_redirects > Unfortunately it does not solve the problem for me, I have have these "cache <redirected>" entries even after that echo command. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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