[Intrepid] Intermittent TCP issues with 2.6.27

[Dean Holland]

I am having intermittent TCP issues with 2.6.27 in a KVM guest. Pings, email and many websites work without issue however several sites do not, e.g:
 - store.apple.com
 - youtube.com
 - www.anz.com (https)
 - msn messenger

I have narrowed it down specifically to 2.6.27 through the following troubleshooting:
 - rebuilt guest as a clean Intrepid amd64 install (current was upgraded from Hardy)
 - rebuilt guest as a clean i386 install
 - changed guest network device type from virtio to default (rtl8139)
 - tried clamping MSS to 1460 and 1420 (PPP MTU is 1492), as well as auto (--clamp-mss-to-pmtu)
 - clean iptables firewall with just a MASQUERADE rule
 - removed tc htb QoS rules
 - built a vanilla 2.6.26 kernel with kernel-package (this worked fine)
 - disabled various TCP options, such as tcp_sack, tcp_timestamps and tcp_window_scaling

Basically to go from a problematic state with 2.6.27 to having no issues I simply change the default kernel to 2.6.26 or 2.6.24-21 (Hardy kernel) in /boot/grub/menu.lst and reboot, nothing else resolves the issue.

Originally this was thought to be a symptom of bug #264019 but it appears it may be something different. I will attach PCAP and tcpdump outputs to assist with troubleshooting.

Thanks

[Leann Ogasawara (leannogasawara)]

Hi Dean,

Can you paste the output of 'cat /proc/version_signature' so we can see the specific 2.6.27-7 kernel version you are running. You also mention you tested a vanilla 2.6.26 kernel. Just curious if you've tested an newer 2.6.28-rc4 vanilla kernel and if this issue exists there? Thanks.

[Dean Holland (speedster-3fl)]

Hi Leann,

Thanks for the response.

speedster@whinge:~$ cat /proc/version_signature
Ubuntu 2.6.27-7.16-server

I have tried -generic however, with the same result. Also with 2.6.28-rc4 I am still seeing the issue.

[Leann Ogasawara (leannogasawara)]

Thanks Dean. Since you have tested and verified this is also an issue with the upstream kernel it would be great if you could open an upstream kernel bug report at http://bugzilla.kernel.org so that the upstream developers are also aware of the issue. We can set up and upstream bug watch from this report as well. If you can please post the upstream buglink here for others to reference that would be great. Thanks.

[Dean Holland (speedster-3fl)]

No worries Leann,

I haven't got around to this due to the holidays and family commitments but will attempt to do so in the near future.

Dean

[Dean Holland (speedster-3fl)]

Lodged in Bugzilla as 12327 (http://bugzilla.kernel.org/show_bug.cgi?id=12327)

[andre (andrew-dorrell)]

See also

linkedin very slow on Firefox Linux only
https://bugs.launchpad.net/bugs/314713

[Jeremy Foshee (jeremyfoshee)]

This bug report was marked as Triaged a while ago but has not had any updated comments for quite some time. Please let us know if this issue remains in the current Ubuntu release, http://www.ubuntu.com/getubuntu/download . If the issue remains, click on the current status under the Status column and change the status back to "New". Thanks.

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[Brad Figg (brad-figg)]

This bug was filed against a series that is no longer supported and so is being marked as Won't Fix. If this issue still exists in a supported series, please file a new bug.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.