dummynet damages ICMPv6 packets

[Przemyslaw Frasunek]

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.