Networking under Xen

[George Neville-Neil]

On 15 Jul 2015, at 3:54, Colin Percival wrote:

> On 07/15/15 00:44, Kristof Provost wrote:
>>> On 14 Jul 2015, at 21:23, Mark Felder <feld at FreeBSD.org> wrote:
>>> On Tue, Jul 14, 2015, at 13:54, Colin Percival wrote:
>>>> More precisely *pf* is a known issue.  It's inserting TCP checksums
>>>> into TSO packets.  I reported this a long time ago and I don't know
>>>> why pf still hasn't been fixed.
>>>
>>> I think Kristof may have solved this in HEAD with all of the care 
>>> and
>>> feeding he has been doing to pf, but I haven't verified.
>>
>> I wouldn’t expect so. As far as I know I’ve not fixed anything 
>> TSO or
>> checksum related.
>
> In my tests, deleting these lines from pf_ioctl.c
>
> 3570	/* We need a proper CSUM befor we start (s. OpenBSD ip_output) */
> 3571	if ((*m)->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
> 3572		in_delayed_cksum(*m);
> 3573		(*m)->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
> 3574	}
>
> unbreaks pf+TSO on EC2 instances.  I'm not entirely sure why these 
> lines
> are there in the first place, which is why I didn't want to simply go 
> in
> and remove them -- but it may be that wrapping those lines in 
> something
> like "if ((csum_flags & CSUM_TSO) == 0)" would solve the problem 
> without
> breaking anything else.
>

Since Kristof is already working on this, I'll let him address it.  If 
necessary
open a PR on this specifically please.

Best,
George