Re: How to do TCP tx checksums

[Ben Greear <greearb@candelatech.com>]

On 11/17/2015 10:26 AM, Eric Dumazet wrote:
> On Tue, 2015-11-17 at 09:44 -0800, Ben Greear wrote:
>
>> And in case it helps, here is the output from dmesg.
>>
>> This is an Ethernet frame, and in this case csum-start is the
>> index of the first byte of the TCP header as far as I can tell.
>>
>> [64967.194251] check: 0xf51b  csum-start: 34  offset: 16 summed: 0x3  saddr: 0x201010a  daddr: 0x101010a len: 1514
>>
>
> You forgot to clear tcp header @check before calling
> __tcp_v4_send_check(), I think.
>
> ( th->check = 0; )

 From printk I added to e1000e, it looks like I have bad offsets
somehow.  I'll try clearing check as well, however.

> Anyway, just use trafgen and get ~6 Mpps, more easily than with pktgen.

I do plan to look at this...but need to make sure I can get similar
features before I ditch pktgen.  It's not just raw throughput that is
of interest to me, but also randomizing, sequential, etc header fields
to test various network equipment (routers, MAC tables in switches, etc).

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com