| View previous topic :: View next topic |
| Author |
Message |
haven
Tux's lil' helper
Joined: 19 Nov 2003
Posts: 141
Location: Belfast, Uk
|
 Posted: Tue Oct 28, 2008 1:18 pm Post subject: [Closed]2.6.27.3 tcp_sack is broken |
 |
|
This may affect linux-2.6.27-gentoo-r1, I have not had time to check.
It appears that tcp_sack has broken somewhere between 2.6.26.5 (where I was) and 2.6.27.3 (where I upgraded to). I have replicated this on two boxes now and noticed it causing havok with my network.
The symptoms from the destination box using tcpdump will show lots of checksum errors. The example below is me attempting to create a ssh connection:
Source machine 2.6.27 kernel (broken tcp_sack):
| Quote: | | 09:36:11.975259 IP sourceip.46325 > destinationip.ssh: S 1435066715:1435066715(0) win 5840 <sackOK,timestamp 349132422 0,mss 1460,nop,wscale 7> |
Source machine is using sack.
Target machine 2.6.26.5 kernel (working tcp_sack):
| Quote: | | 09:36:09.872556 IP (tos 0x0, ttl 53, id 14301, offset 0, flags [DF], proto TCP (6), length 60) sourceip.46325 > destinationip.ssh: S, cksum 0x1a58 (incorrect (-> 0xb1c0), 1435066715:1435066715(0) win 5840 <sackOK,timestamp 2026854022 0[len 5],mss 1460,nop,wscale 7> |
You can see that both the checksum is invalid: cksum 0x1a58 (incorrect and sack is enabled: sackOK
The target machine refuses to validate the 2.6.27.3's sack chksum. If you change the source machine to 2.6.26.5 or disable sack on 2.6.27.3 then either option fixes the problem.
NB you disable tcp_sack via:
| Quote: | | echo 0 > /proc/sys/net/ipv4/tcp_sack |
I haven't posted this upstream to the kernel devs so feel free as I'm short on time. My fix on one box was to roll back to previous kernel revision and avoid 2.6.27.x until I see something mentioning this in the Changelogs (didn't notice anything about it in 2.6.27.4).
Regards
Haven.
Last edited by haven on Wed Oct 29, 2008 9:19 pm; edited 1 time in total |
|
| Back to top |
|
 |
VoidMage
Watchman
Joined: 14 Oct 2006
Posts: 6196
|
| Posted: Tue Oct 28, 2008 5:24 pm Post subject: |
|
|
So you seems to have missed both the gentoo and the upstream bug about it.
Search for the gentoo bug first, there you'll find the link to the upstream bug. |
|
| Back to top |
|
|
haven
Tux's lil' helper
Joined: 19 Nov 2003
Posts: 141
Location: Belfast, Uk
|
| Posted: Tue Oct 28, 2008 6:15 pm Post subject: |
|
|
| Took a look and still didn't spot it, can you throw me a link ? |
|
| Back to top |
|
|
VoidMage
Watchman
Joined: 14 Oct 2006
Posts: 6196
|
| Posted: Tue Oct 28, 2008 8:41 pm Post subject: |
|
|
| Sure thing. It's this one. |
|
| Back to top |
|
|
haven
Tux's lil' helper
Joined: 19 Nov 2003
Posts: 141
Location: Belfast, Uk
|
| Posted: Wed Oct 29, 2008 9:19 pm Post subject: |
|
|
| Thanks, updated subject to reflect the fact its being tracked. |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
|
Kernel & Hardware
