On Fri, Jan 22, 2010 at 9:58 AM, Toni Mueller <[email protected]> wrote:
> Hi,
>
> On Thu, 21.01.2010 at 21:48:01 +0000, Christian Weisgerber
> <[email protected]> wrote:
>> Toni Mueller <[email protected]> wrote:
>> > today I see tons of these on a 4.6-stable/amd64 machine (sample):
>> > 17:21:00.848135 esp 1.1.1.1 > 2.2.2.2 spi 0x54d46678 seq 132642 len 84
>> > (DF) (ttl 64, id 49897, len 104, bad cksum 0! differs by 8b3c)
>>
>> This looks like outgoing packets on an interface that does IPv4
>> header checksumming in hardware. tcpdump sees the packets before
>> the checksum is actually filled in. This has nothing to do with
>> IPsec.
>
> thanks for the explanation. I didn't think of it, but it's a bge(4)
> interface.
>From bge(4)
The bge driver supports IPv4 IP, TCP, and UDP checksum offload for re-
ceive, IP checksum offload for transmit, VLAN tag insertion and strip-
ping, as well as a 256-bit multicast hash filter. The BCM5723, BCM5754,
BCM5755, BCM5761, BCM5764, BCM5784, BCM5785, BCM5787 and BCM577x0 chips
also support IPv6 receive TCP/UDP checksum offload.
A netstat -ss will show if it is used. You will see entries like
6575 input datagrams checksum-processed by hardware
5765 output datagrams checksum-processed by hardware
=Adriaan=
