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RE: [Xen-users] Strange TCP-Problem with GPL PV 0.8.8

To: "Stephan Schnitzer" <hakker@xxxxxxx>, <Xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-users] Strange TCP-Problem with GPL PV 0.8.8
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Thu, 3 Apr 2008 09:38:20 +1100
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Thread-topic: [Xen-users] Strange TCP-Problem with GPL PV 0.8.8
> I have a strange problem with GPL PV 0.8.8 (0.6.4 did work).
> On my 2nd vif I cannot establish TCP connections. The 3rd IP packet
> from XEN-Image) is not forwarded by XEN/DOM0-Bridge.
> If I boot Windows without /GPLPV option, everything works fine.
> I did some investigation and found out that the packages arrive
> differently if GPLPV is enabled.
> "br_inet" is a bridge connected to the DSL router via peth1.
> With /GPLPV:
> iptables log: IN=br_inet OUT=br_inet PHYSIN=tap3 PHYSOUT=peth1
> SRC= DST= LEN=40 TOS=0x00 PREC=0x00 TTL=128
> ID=465 DF PROTO=TCP SPT=1050 DPT=80 WINDOW=65535 RES=0x00 ACK URGP=0
> => Those packets are never forwarded to peth1. To be sure I verified
> this by using port mirroring on the switch that connects peth1 with
> DSL router.
> Without /GPLPV:
> iptables log: IN=br_inet OUT=br_inet PHYSIN=vif44.1 PHYSOUT=peth1
> SRC= DST= LEN=40 TOS=0x00 PREC=0x00 TTL=128
> ID=22627 DF PROTO=TCP SPT=1137 DPT=80 WINDOW=65535 RES=0x00 ACK URGP=0
> => Those packets are forwarded to peth1
> The only relevant difference seems to be the PHYSIN interface.
> I have to mention that the communication between Dom0 and DomU works
> perfectly with GPLPV (first vif, more than 10 times faster than
> GPLPV). The only problem are TCP connections to the internet (second
> My System:
> Ubuntu 7.10 64bit with XEN 3.1 on Intel Xeon 5130
> Windows XP x64 SP2 (english with German MUI)

Are both the bridges in question linked to hardware adapters? What are
the hardware adapters?

Can you do a 'ethtool -k peth0' and 'ethtool -k peth1'? (assuming that
your physical Ethernet adapters are peth0 and peth1.

My best guess at this stage is that the working interface supports
hardware offload while the non-working one doesn't.

Another thing you can try is to right click on the network adapter in
'device manager' and select properties, and try turning off checksum and
large send offload.

Please let me know what you find.



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