Subject: Re: IPv6 path MTU discovery broken

From: "Steinar H. Gunderson" <[email-masked]>
Date: Sun, 6 Oct 2013 14:06:12 +0200

On Sat, Sep 28, 2013 at 10:33:18PM +0200, Hannes Frederic Sowa wrote:
>> So the “packet too big” packets really look like they're being ignored.
>> However, they _do_ reach the kernel somehow, since Icmp6InPktTooBigs
>> seems to increase.
>> 
>> Could this be related somehow to the packets coming from 2001:67c:29f4::31,
>> while the default route is to a link-local address? (An RPF issue?) This used
>> to work (although it was often flaky for me) in 3.10 and before. I can't
>> easily bisect, though, as I don't boot this machine too often.
> This looks like a bug and should definitely get fixed. There should be
> no RPF issue. May I have a look at your /proc/net/ipv6_route?

It started again, so now I could capture what you asked for:

pannekake:~> cat /proc/net/ipv6_route 
20010500007200000000000000000000 30 00000000000000000000000000000000 00 2001067c29f400000000000000000001 00000400 00000000 00000000 00000003     eth0
2001067c00a400037c4d9ae8ab73230f 80 00000000000000000000000000000000 00 fe80000000000000023048fffe555743 00000000 00000001 00000137 01000023     eth0
2001067c00a400000000000000000000 30 00000000000000000000000000000000 00 fe80000000000000023048fffe555743 00000064 00000000 00000000 00000003     eth0
2001067c29f400000000000000000001 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000001 00003dc0 01000001     eth0
2001067c29f400000000000000000031 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000001 00047359 01000001     eth0
2001067c29f400000000000000000000 40 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000001 00000001     eth0
2001067c29f400010000000000000000 40 00000000000000000000000000000000 00 fe80000000000000023048fffe555743 00000064 00000000 00000000 00000003     eth0
2001067c29f410000000000000000000 40 00000000000000000000000000000000 00 fe80000000000000023048fffe555743 00000064 00000000 00000000 00000003     eth0
2001067c29f410010000000000000000 40 00000000000000000000000000000000 00 fe80000000000000023048fffe555743 00000064 00000000 00000000 00000003     eth0
2001067c29f410030000000000000000 40 00000000000000000000000000000000 00 fe80000000000000023048fffe555743 00000064 00000000 00000000 00000003     eth0
2001067c29f410050000000000000000 40 00000000000000000000000000000000 00 fe80000000000000023048fffe555743 00000064 00000000 00000000 00000003     eth0
2001067c29f410070000000000000000 40 00000000000000000000000000000000 00 fe80000000000000023048fffe555743 00000064 00000000 00000000 00000003     eth0
2001067c29f400000000000000000000 30 00000000000000000000000000000000 00 2001067c29f400000000000000000001 00000400 00000000 00000000 00000003     eth0
20010700000000000000000000000000 20 00000000000000000000000000000000 00 2001067c29f400000000000000000001 00000400 00000000 00000000 00000003     eth0
2001070800402001a822bafffec42428 80 00000000000000000000000000000000 00 2001067c29f400000000000000000001 00000000 00000001 0000ab13 01000003     eth0
20010840000010000001000000000001 80 00000000000000000000000000000000 00 2001067c29f400000000000000000001 00000000 00000001 0001114c 01000003     eth0
26200000105f0004be305bfffed17063 80 00000000000000000000000000000000 00 2001067c29f400000000000000000001 00000000 00000003 0000002f 01000003     eth0
2a01023842d7aa006667669799990042 80 00000000000000000000000000000000 00 2001067c29f400000000000000000001 00000000 00000001 000081ef 01000003     eth0
2a022368000000000000000000000000 20 00000000000000000000000000000000 00 2001067c29f400000000000000000001 00000400 00000000 00000000 00000003     eth0
fe80000000000000000000002ae38049 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000001 00000001 01000001  k_magne
fe80000000000000000000002cb7a217 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 00000004 01000001 k_molvenfinnoy
fe8000000000000000000000315e851e 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000001 00000001 01000001 k_trygve
fe8000000000000000000000419b407a 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000001 00000001 01000001 k_molven
fe80000000000000000000005ccc2ed1 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000001 00000001 01000001 k_sessesveits
fe800000000000000000000077707d72 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000001 00000001 01000001  k_berge
fe8000000000000000000000c2faf88c 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000001 00000001 01000001 k_wikene
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_sessesveits
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_trygve
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_wikene
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_molven
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001  k_magne
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001  k_berge
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_molvenfinnoy
fe800000000000000000000000000000 40 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001     eth0
fe800000000000000000000000000000 40 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_sessesveits
fe800000000000000000000000000000 40 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_trygve
fe800000000000000000000000000000 40 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_wikene
fe800000000000000000000000000000 40 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_molven
fe800000000000000000000000000000 40 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001  k_magne
fe800000000000000000000000000000 40 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001  k_berge
fe800000000000000000000000000000 40 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_molvenfinnoy
00000000000000000000000000000000 00 00000000000000000000000000000000 00 2001067c29f400000000000000000001 00000400 00000000 00000000 00000003     eth0
00000000000000000000000000000000 00 00000000000000000000000000000000 00 00000000000000000000000000000000 ffffffff 00000001 0009a4db 00200200       lo
00000000000000000000000000000001 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000001 0000a62c 80200001       lo
2001067c29f400000000000000000000 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000001 00000000 00300001       lo
2001067c29f400000000000000000050 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 0000000a 1a692b94 80200001       lo
fe800000000000000000000000000000 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000001 00000000 00300001       lo
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000002 0000602f 80200001       lo
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000002 00003c59 80200001       lo
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000002 0000530e 80200001       lo
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000002 00005bbb 80200001       lo
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000002 00003fad 80200001       lo
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000002 00002953 80200001       lo
fe8000000000000000000000c30b9a61 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000001 00000000 80200001       lo
fe80000000000000022590fffe006b52 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000001 0000541c 80200001       lo
ff020000000000000000000000000001 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 00000002 01000001     eth0
ff02000000000000000000000000000d 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 0000003a 01000001     eth0
ff02000000000000000000000000000d 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 0000000b 01000001 k_sessesveits
ff02000000000000000000000000000d 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 0000000b 01000001 k_molven
ff020000000000000000000000010002 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 00000004 01000001     eth0
ff0200000000000000000001ff000020 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 00000001 01000001     eth0
ff0200000000000000000001ff000029 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 0000000a 01000001     eth0
ff0200000000000000000001ff000030 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 00000004 01000001     eth0
ff0200000000000000000001ff000031 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 00000001 01000001     eth0
ff0200000000000000000001ff000032 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 00000045 01000001     eth0
ff0200000000000000000001ff000057 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 00000001 01000001     eth0
ff0200000000000000000001ff003004 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 00000001 01000001     eth0
ff0200000000000000000001ff003005 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 00000002 01000001     eth0
ff0200000000000000000001ff4793da 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 00000003 01000001     eth0
ff0200000000000000000001ff5945c2 80 00000000000000000000000000000000 00 00000000000000000000000000000000 00000000 00000000 00000003 01000001     eth0
ff000000000000000000000000000000 08 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001     eth0
ff000000000000000000000000000000 08 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_sessesveits
ff000000000000000000000000000000 08 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_trygve
ff000000000000000000000000000000 08 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_wikene
ff000000000000000000000000000000 08 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_molven
ff000000000000000000000000000000 08 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001  k_magne
ff000000000000000000000000000000 08 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001  k_berge
ff000000000000000000000000000000 08 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001 k_molvenfinnoy
00000000000000000000000000000000 00 00000000000000000000000000000000 00 00000000000000000000000000000000 ffffffff 00000001 0009a4db 00200200       lo

/* Steinar */
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