IPv6 problems with 2.4.19?

From: Noah L. Meyerhans (frodo@morgul.net)
Date: Wed Sep 04 2002 - 10:59:18 EST


I was recently made aware of a problem with traceroute6 from the
iputils package, and I've only been able to duplicate the
problem when running kernel 2.4.19. But, that's not to say that *all*
2.4.19 systems are effected; the laptop I'm using now doesn't exhibit
the problem under 2.4.19, but my workstation does.

The symtoms of the problem are traceroute6 outputs that look like:
ant:~$ traceroute6 -n www.linux-ipv6.org
traceroute to moon.linux-ipv6.org (2001:200:0:1003:200:f8ff:fe1e:2d69) from 2002:d03b:fa68:dead:2a0:ccff:fe57:a34e, 30 hops max, 16 byte packets
 1 98fc:ffbf:4e51:1240:e0a0:408:70a2:408 0.258 ms 0.163 ms 0.159 ms
 2 98fc:ffbf:4e51:1240:e0a0:408:70a2:408 479.163 ms 472.151 ms 483.137 ms
 3 98fc:ffbf:4e51:1240:e0a0:408:70a2:408 449.042 ms 461.665 ms 469.646 ms
 4 98fc:ffbf:4e51:1240:e0a0:408:70a2:408 309.023 ms 315.5 ms 314.552 ms
 5 * 2002:d03b:fa68:dead::1 409.508 ms 422.063 ms
 6 2002:d03b:fa68:dead::1 411.045 ms 418.124 ms 417.661 ms
 7 2002:d03b:fa68:dead::1 383.046 ms 383.544 ms 396.091 ms
 8 2002:d03b:fa68:dead::1 388.026 ms 409.155 ms 386.63 ms
 9 2002:d03b:fa68:dead::1 403.959 ms 422.665 ms 430.162 ms
10 2002:d03b:fa68:dead::1 384.55 ms 396.111 ms 379.592 ms
                                                                                
I can watch network traffic with tcpdump and see that the right bits are
going over the network, but completely incorrect addresses are printed.
2002:d03b:fa68:dead::1 is the IPv6 gateway, and should be the first hop.
98fc:ffbf:4e51:1240:e0a0:408:70a2:408 is obviously bogus. I suppose
it's possible that the problem is with traceroute6, but it's only
present under kernel 2.4.19.
                                                                                
tracepath6 does not show this problem, and if I reboot the system to
2.4.17 traceroute6 works fine. The person who first notified me about
this was able to determine that the problem occurs for him under
2.4.19-rc3, but not 2.4.19-pre8. On the systems that have this problem,
the it is persistant across reboots and occurs with every execution of
traceroute6. I haven't found a workaround for it yet. If anybody has
any suggestions or if this is a known bug, please let me know. Thanks.

noah

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