| Message ID | 1347270171.1234.1353.camel@edumazet-glaptop |
|---|---|
| State | RFC, archived |
| Delegated to: | David Miller |
| Headers | show |
On Mon, 2012-09-10 at 11:42 +0200, Eric Dumazet wrote: > On Mon, 2012-09-10 at 12:59 +0400, Andrei Dolnikov wrote: > > Hello all, > > > > The following issue is observed on most Linux distributions: > > Transmission of fragmented IP packets in case of missing ARP entry for > > destination IP fails. > > Actually ARP request is sent, and, once ARP response is received, only > > few queued fragments are transmitted. Remaining fragments are lost. > > It can be easily reproduced as follows: > > # arp -d <dst IP> > > # ping -s 65000 -c 1 <dst IP> > > Ping result is: "1 packets transmitted, 0 received, 100% packet loss, > > time 0ms". > > > > The latest kernel version I tried was 3.5.0-1 x86_64, but I also was > > able to reproduce it with 3.2.x, 3.0.x and 2.6.32. > > It doesn't depend on hardware: was able to reproduce with VMWare Player, > > Intel based laptop, Intel Atom and ARM based custom boards. > > As I'm not a networking standards expert I'm not sure if it's a real bug > > or acceptable behaviour, but decided to raise the issue here as I can't > > reproduce this anomaly with the Windows 7 PC. > > > > Thanks, > > Andrei. > > -- > > Its a bit better with linux-3.3, with commit > 8b5c171bb3dc0686b2647a84e990199c5faa9ef8 > (neigh: new unresolved queue limits) > > +neigh/default/unres_qlen_bytes - INTEGER > + The maximum number of bytes which may be used by packets > + queued for each unresolved address by other network layers. > + (added in linux 3.3) > + > +neigh/default/unres_qlen - INTEGER > + The maximum number of packets which may be queued for each > + unresolved address by other network layers. > + (deprecated in linux 3.3) : use unres_qlen_bytes instead. > > > Problem is : unres_qlen_bytes default value is 65536, so its a bit too > small once you take into account truesize overhead > > I guess following patch would be needed : > > diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c > index 4780045..3395bb6 100644 > --- a/net/ipv4/arp.c > +++ b/net/ipv4/arp.c > @@ -171,7 +171,7 @@ struct neigh_table arp_tbl = { > .gc_staletime = 60 * HZ, > .reachable_time = 30 * HZ, > .delay_probe_time = 5 * HZ, > - .queue_len_bytes = 64*1024, > + .queue_len_bytes = 64 * SKB_TRUESIZE(1024), > .ucast_probes = 3, > .mcast_probes = 3, > .anycast_delay = 1 * HZ, In the mean time, you can also do echo 50 >/proc/sys/net/ipv4/neigh/eth0/unres_qlen (change eth0 by the name of your interface) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Works for me. Thank you! Andrei. On 09/10/2012 01:53 PM, Eric Dumazet wrote: > On Mon, 2012-09-10 at 11:42 +0200, Eric Dumazet wrote: >> On Mon, 2012-09-10 at 12:59 +0400, Andrei Dolnikov wrote: >>> Hello all, >>> >>> The following issue is observed on most Linux distributions: >>> Transmission of fragmented IP packets in case of missing ARP entry for >>> destination IP fails. >>> Actually ARP request is sent, and, once ARP response is received, only >>> few queued fragments are transmitted. Remaining fragments are lost. >>> It can be easily reproduced as follows: >>> # arp -d <dst IP> >>> # ping -s 65000 -c 1 <dst IP> >>> Ping result is: "1 packets transmitted, 0 received, 100% packet loss, >>> time 0ms". >>> >>> The latest kernel version I tried was 3.5.0-1 x86_64, but I also was >>> able to reproduce it with 3.2.x, 3.0.x and 2.6.32. >>> It doesn't depend on hardware: was able to reproduce with VMWare Player, >>> Intel based laptop, Intel Atom and ARM based custom boards. >>> As I'm not a networking standards expert I'm not sure if it's a real bug >>> or acceptable behaviour, but decided to raise the issue here as I can't >>> reproduce this anomaly with the Windows 7 PC. >>> >>> Thanks, >>> Andrei. >>> -- >> Its a bit better with linux-3.3, with commit >> 8b5c171bb3dc0686b2647a84e990199c5faa9ef8 >> (neigh: new unresolved queue limits) >> >> +neigh/default/unres_qlen_bytes - INTEGER >> + The maximum number of bytes which may be used by packets >> + queued for each unresolved address by other network layers. >> + (added in linux 3.3) >> + >> +neigh/default/unres_qlen - INTEGER >> + The maximum number of packets which may be queued for each >> + unresolved address by other network layers. >> + (deprecated in linux 3.3) : use unres_qlen_bytes instead. >> >> >> Problem is : unres_qlen_bytes default value is 65536, so its a bit too >> small once you take into account truesize overhead >> >> I guess following patch would be needed : >> >> diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c >> index 4780045..3395bb6 100644 >> --- a/net/ipv4/arp.c >> +++ b/net/ipv4/arp.c >> @@ -171,7 +171,7 @@ struct neigh_table arp_tbl = { >> .gc_staletime = 60 * HZ, >> .reachable_time = 30 * HZ, >> .delay_probe_time = 5 * HZ, >> - .queue_len_bytes = 64*1024, >> + .queue_len_bytes = 64 * SKB_TRUESIZE(1024), >> .ucast_probes = 3, >> .mcast_probes = 3, >> .anycast_delay = 1 * HZ, > In the mean time, you can also do > > echo 50 >/proc/sys/net/ipv4/neigh/eth0/unres_qlen > > (change eth0 by the name of your interface) > > > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c index 4780045..3395bb6 100644 --- a/net/ipv4/arp.c +++ b/net/ipv4/arp.c @@ -171,7 +171,7 @@ struct neigh_table arp_tbl = { .gc_staletime = 60 * HZ, .reachable_time = 30 * HZ, .delay_probe_time = 5 * HZ, - .queue_len_bytes = 64*1024, + .queue_len_bytes = 64 * SKB_TRUESIZE(1024), .ucast_probes = 3, .mcast_probes = 3, .anycast_delay = 1 * HZ,