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Date:      Wed, 12 Feb 2014 12:36:16 +0000
From:      Karl Pielorz <kpielorz_lst@tdx.co.uk>
To:        =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= <roger.pau@citrix.com>, freebsd-xen@freebsd.org
Subject:   Re: Xen PV Networking issue - disable PV NIC in XENHVM FreeBSD?
Message-ID:  <F315231A406BDA0F89DF2D14@Mail-PC.tdx.co.uk>
In-Reply-To: <52FA5BEA.6030307@citrix.com>
References:  <D280F84BE886E8D6110B93D0@study64.tdx.co.uk> <52F8FE87.1010705@citrix.com> <72C34BC121BD5A0FBDAEFA37@Mail-PC.tdx.co.uk> <52FA5BEA.6030307@citrix.com>

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--On 11 February 2014 18:20 +0100 Roger Pau Monn=C3=A9 =
<roger.pau@citrix.com>=20
wrote:

> Just to clarify, are you unable to reach a FreeBSD PV DomU from a
> Windows PV DomU on the same host, or are you unable to route traffic
> trough a FreeBSD PV DomU (on the same host)?
>
> (ie. can you ssh from the Windows PV DomU into the FreeBSD PV DomU?)

ssh from the Windows PV host to the FreeBSD PV DomU host appears to work=20
fine. Attempting to 'route' traffic from the Windows PV host 'through' the=20
FreeBSD PV DomU fails - pings go, DNS goes, initial TCP 'setups' go - but=20
stuff dies thereafter (i.e. may be packet size related or something).

Move the FreeBSD PV DomU host to the other XenServer - works. Disabled PV=20
NIC in windows, it works. Run up the FreeBSD PV as HVM (i.e. Realtek) -=20
works. Replace FreeBSD with Linux - it works. So FreeBSD PV on same=20
XenServer as Windows, fails.

The only combination I've not tested is FreeBSD DomU PV host trying to use=20
the FreeBSD DomU PV other host as a gateway. I've no reason to believe that =

won't fail (with the same circumstances as above).

The Windows PV Host has 1 NIC which is attached to Xen network 'Office=20
Network' (using e.g. 10.0.0.10).

The FreeBSD PV Host has 2 NIC's - Interface 0 is attached to Xen network=20
'Office Network' (using e.g. 10.0.0.1) - Interface 1 is attached to Xen=20
network 'ADSL Network' (using e.g. 192.168.1.10)

The FreeBSD DomU PV host gateway can ping / fetch data fine from the ADSL=20
connection itself, fine. It's setup to NAT for the Office Network (standard =

rc.conf setup).

>> So it looks like it might actually be a FreeBSD/Xen issue?
>
> Yes, it looks that way (dunno if netback might also be involved in this)

Doh! :( That's annoying ;)

> I have to look into this, FreeBSD should not panic when trying to boot
> without XENHVM on a DomU.

Ok the panic wasn't reproducible - I don't know what I did to that kernel=20
build, but re-building GENERIC without the Xen options results in a kernel=20
that boots ok in with HVM drivers (i.e. Realtek NIC's) - and using these=20
fixes the problem (as evidenced above).

> You could try to disable the following:
>
> ifconfig xnX -rxcsum -txcsum -tso4 -lro

No combination of those made any difference (which I guess is both a good=20
and a bad thing).

Anything else you can think of / worth trying? - As I said I'm running the=20
XenServer distribution ISO (with SP1) - I'm not sure if that has support=20
for much debugging stuff built in?

-Karl









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