dummynet damages ICMPv6 packets

[Crest]

On 07.11.2011 11:04, Przemyslaw Frasunek wrote:
> Hello,
>
> we are experiencing interesing behaviour of dummynet enabled on IPv6 interfaces.
> When the following rules are added:
>
> add pipe 24 ip from any to any in recv vlan1
> add pipe 25 ip from any to any out xmit vlan1
>
> all ICMPv6 packets passing on vlan1 are being damaged:
>
> 10:55:53.180801 IP6 fe80::215:17ff:feae:4d99>  ff02::1: ip-proto-64 16
>          0x0000:  6000 0000 0010 403a fe80 0000 0000 0000  `.....@:........
>          0x0010:  0215 17ff feae 4d99 ff02 0000 0000 0000  ......M.........
>          0x0020:  0000 0000 0000 0001 8000 2dc9 31f2 002e  ..........-.1...
>          0x0030:  4eb7 ab29 0002 c207                      N..)....
>
> Please note invalid protocol shown by tcpdump and shifted bytes at offset 7 and
> 8 (it reads 0x403a but should be 0x3a40).
>
> After changing dummynet rule to:
>
> add pipe 24 ip4 from any to any in recv vlan1
> add pipe 25 ip4 from any to any out xmit vlan1
>
> packets are no longer malformed:
>
> 11:01:49.934348 IP6 fe80::215:17ff:feae:4d99>  ff02::1: ICMP6, echo request, seq
> 0, length 16
>          0x0000:  6000 0000 0010 3a40 fe80 0000 0000 0000  `.....:@........
>          0x0010:  0215 17ff feae 4d99 ff02 0000 0000 0000  ......M.........
>          0x0020:  0000 0000 0000 0001 8000 ab9a 3341 0000  ............3A..
>          0x0030:  4eb7 ac8d 000e 41a5                      N.....A.
>
> The above problem affects 8.2-STABLE compiled on 3rd May 2011.
>

Looks like you ran into kern/157239.