[ovs-discuss] Checksum incorrect when rewriting icmpv6 packet

[Neal Shrader]

Hi there --

I came across an issue today what I was attempting to modify the source
ipv6 address of a router advertisement generated from a local server.  The
flow in question looks like:

ovs-ofctl add-flow public
'priority=2040,icmp6,in_port=LOCAL,ipv6_dst=ff02::1,table=1,idle_timeout=0,actions=set_field:fe80::1->ipv6_src,strip_vlan,flood'

When I generate an RA, I see that it has an incorrect checksum, and
therefore is rejected by the destination host:

17:54:34.927522 IP6 (class 0xc0, hlim 255, next-header ICMPv6 (58) payload
length: 88) fe80::1 > ip6-allnodes: [bad icmp6 cksum 0x53ff -> 0xb08e!]
ICMP6, router advertisement, length 88
hop limit 64, Flags [managed, other stateful], pref medium, router lifetime
1800s, reachable time 0s, retrans time 0s
  prefix info option (3), length 32 (4): 2400:6180:0:d0::/64, Flags
[onlink], valid time infinity, pref. time infinity
    0x0000:  4080 ffff ffff ffff ffff 0000 0000 2400
    0x0010:  6180 0000 00d0 0000 0000 0000 0000
  mtu option (5), length 8 (1):  1500
    0x0000:  0000 0000 05dc
  source link-address option (1), length 8 (1): b8:ca:3a:68:68:5d
    0x0000:  b8ca 3a68 685d
  rdnss option (25), length 24 (3):  lifetime 4294967295s, addr:
2001:4860:4860::8888
    0x0000:  0000 ffff ffff 2001 4860 4860 0000 0000
    0x0010:  0000 0000 8888
0x0000:  6c00 0000 0058 3aff fe80 0000 0000 0000  l....X:.........
0x0010:  0000 0000 0000 0001 ff02 0000 0000 0000  ................
0x0020:  0000 0000 0000 0001 8600 53ff 40c0 0708  ..........S. at ...
0x0030:  0000 0000 0000 0000 0304 4080 ffff ffff  .......... at .....
0x0040:  ffff ffff 0000 0000 2400 6180 0000 00d0  ........$.a.....
0x0050:  0000 0000 0000 0000 0501 0000 0000 05dc  ................
0x0060:  0101 b8ca 3a68 685d 1903 0000 ffff ffff  ....:hh]........
0x0070:  2001 4860 4860 0000 0000 0000 0000 8888  ..H`H`..........

Is there anything here that I can do to have it properly regenerate the
checksum? The environment is running 1.10.2, and I'm not sure of the
possibility of upgrading it across the board.  If there's some solution or
insight within the current version to work around this, it would be highly
appreciated!
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://openvswitch.org/pipermail/ovs-discuss/attachments/20140814/e70d63a5/attachment-0002.html>