Xen PV Networking issue - disable PV NIC in XENHVM FreeBSD?

[Karl Pielorz]

--On 11 February 2014 18:20 +0100 Roger Pau Monné <roger.pau at citrix.com> 
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 
fine. Attempting to 'route' traffic from the Windows PV host 'through' the 
FreeBSD PV DomU fails - pings go, DNS goes, initial TCP 'setups' go - but 
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 
NIC in windows, it works. Run up the FreeBSD PV as HVM (i.e. Realtek) - 
works. Replace FreeBSD with Linux - it works. So FreeBSD PV on same 
XenServer as Windows, fails.

The only combination I've not tested is FreeBSD DomU PV host trying to use 
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 
Network' (using e.g. 10.0.0.10).

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

The FreeBSD DomU PV host gateway can ping / fetch data fine from the ADSL 
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 
build, but re-building GENERIC without the Xen options results in a kernel 
that boots ok in with HVM drivers (i.e. Realtek NIC's) - and using these 
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 
and a bad thing).

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

-Karl