Per route MTU settings are broken in linux kernel 3.2

DISCUSSION Yura Pakhuchiy 2 participants 4 messages Jun 24, 2013 – Jun 26, 2013

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Yura Pakhuchiy

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2013-06-24 08:43 UTC #0 lore raw

Hello Ben,

Looks like setting per route MTU (as described in [1]) is broken in Linux kernel 3.2. I tested with newer Ubuntu kernels 3.5 and 3.8 and it looks like problem is fixed there. I filled Ubuntu bug report [2] with more details and sample script which illustrates problem. But since this problem is probably also present in stock kernel (not just in Ubuntu), is it possible to backport fixes to stable 3.2 series?

1. http://lartc.org/howto/lartc.cookbook.mtu-discovery.html
2. https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1177507

Signature · 2 lines

Best regards,
        Yura

Ben Hutchings

2013-06-24 12:45 UTC #1 lore raw

Quoted 11 lines · Yura Pakhuchiy

Hello Ben,
Looks like setting per route MTU (as described in [1]) is broken in Linux kernel 3.2. I tested with newer Ubuntu kernels 3.5 and 3.8 and it looks like problem is fixed there. I filled Ubuntu bug report [2] with more details and sample script which illustrates problem. But since this problem is probably also present in stock kernel (not just in Ubuntu), is it possible to backport fixes to stable 3.2 series?
1. http://lartc.org/howto/lartc.cookbook.mtu-discovery.html
2. https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1177507

Sure, what are the fixes?

Ben.

Signature · 3 lines

Ben Hutchings
Lowery's Law:
             If it jams, force it. If it breaks, it needed replacing anyway.

Yura Pakhuchiy

author

2013-06-24 13:08 UTC #2 lore raw

Quoted 10 lines · Ben Hutchings

Quoted 9 lines · Yura Pakhuchiy
Hello Ben,
Looks like setting per route MTU (as described in [1]) is broken in Linux kernel 3.2. I tested with newer Ubuntu kernels 3.5 and 3.8 and it looks like problem is fixed there. I filled Ubuntu bug report [2] with more details and sample script which illustrates problem. But since this problem is probably also present in stock kernel (not just in Ubuntu), is it possible to backport fixes to stable 3.2 series?

Quoted 4 lines

Quoted 2 lines
1. http://lartc.org/howto/lartc.cookbook.mtu-discovery.html
2. https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1177507
Sure, what are the fixes?

However I'm not sure whether they all are required or sufficient to fix everything correctly.

Signature · 2 lines

Best regards,
        Yura

Ben Hutchings

2013-06-26 01:12 UTC #3 lore raw

Quoted 29 lines · Yura Pakhuchiy

Quoted 10 lines · Ben Hutchings
Quoted 9 lines · Yura Pakhuchiy
Hello Ben,
Looks like setting per route MTU (as described in [1]) is broken in Linux kernel 3.2. I tested with newer Ubuntu kernels 3.5 and 3.8 and it looks like problem is fixed there. I filled Ubuntu bug report [2] with more details and sample script which illustrates problem. But since this problem is probably also present in stock kernel (not just in Ubuntu), is it possible to backport fixes to stable 3.2 series?
Quoted 4 lines
Quoted 2 lines
1. http://lartc.org/howto/lartc.cookbook.mtu-discovery.html
2. https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1177507
Sure, what are the fixes?
Actually, I do not know :-( Ubuntu devs have not fixed this problem in Ubuntu 3.2 kernel. But these commits in mainline kernel looks related:
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=9b04f350057863d1fad1ba071e09362a1da3503e
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=5f2d04f1f9b52604fca6ee08a77972c0df67e082
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=d851c12b60471188e15e5c8405b289073e8dd025
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=7f92d334ba19a0d8e96f8f8f092219553367d921
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=ee9a8f7ab2edf801b8b514c310455c94acc232f6
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=38d523e2948162776903349c89d65f7b9370dadb
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=fa1e492aa3cbafba9f8fc6d05e5b08a3091daf4a
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=05ab86c55683410593720003442dde629782aaac
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=9cb3a50c5f63ed745702972f66eaee8767659acd
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=b44108dbdbaa07c609bb5755e8dd6c2035236251

Quoted 2 lines

However I'm not sure whether they all are required or sufficient to fix everything correctly.

Sorry, but I really do need someone to tell me exactly what's required. I'm not likely to find the time to work this out myself.

Ben.

Signature · 2 lines

Ben Hutchings
Knowledge is power.  France is bacon.