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RE: [Xen-users] Another GPLPV pre-release 0.9.11-pre20

"James Harper" <james.harper@xxxxxxxxxxxxxxxx> wrote on 05.11.2008 10:49:52:

> > I still see atleast some incorrect tcp chksums if Checksum Offloading
> is enabled.
> >
> Where are you seeing these? If you are seeing them at any point before
> the packet has passed through a physical network card then they will
> indeed have an incorrect checksum. The checksum calculation should be
> deferred until the latest possible time.

I am using tcpdump in my Dom0, eg. tcpdump -vv -i br13.

Here is one example:
10:22:23.172581 IP (tos 0x0, ttl 128, id 18177, offset 0, flags [DF], proto: TCP (6), length: 74) 213.250.XX.XX.ms-wbt-server > 213.250.XX.XX.41635: P, cksum 0x6884 (incorrect (-> 0xc813), 39:61(22) ack 1 win 64620 <nop,nop,timestamp 46147 22223084>

I am bridging VLAN interfaces to Xen DomUs

vconfig add peth0 13
brctl addbr br13
brctl addif br13 peth0.13
ifconfig br13 up

and DomU configuration vif -line:
vif = [ 'mac=00:16:3e:1b:c1:4a,type=ioemu, bridge=br13' ]

> > Large Send Offload is also makeing Bacula to have very slow to
> transfer
> > speeds, if Large Send offload is enabled Bacula transfer speed is
> > something like 30kB/sec, if i disable Large Send Offload it will go to
> > about 70-80Mbit/sec.
> Do you have a Linux PV DomU with lso enabled on that you can test also?

Not at the moment on my test server, i might install one to test.
But i have couple PV Linux DomUs in production and Bacula is working fine there.

> Can you describe (again, if you have done so previously) precisely your
> network layout? Eg what vif is bridged to what physical adapter, and
> where abouts on the network you are sending packets to and from.

I got BladeCenter where my Xen servers are running. I got many networks (usually 1 per customer) which i do bring to DomUs as bridged vlan. My Bacula is not on BladeCenter, it's a dedicated server and theres one switch between BladeCenter and Bacula, link is 1 Gbit/sec (copper).

If i now use brctl show it gives:
br13                8000.001a645c97e4        no                vif65.0
> Also, what is the output of 'cat
> /proc/sys/net/bridge/bridge-nf-call-iptables'. If it's not 0, then
> please try 'echo 0 > /proc/sys/net/bridge/bridge-nf-call-iptables'. This
> will stop bridge packets being touched by iptables, which may be the
> cause of the problems you are seeing. If the Dom0 actually routes the
> packets instead of bridging them (eg if the packet needs to go out a
> Dom0 interface that is not on the same bridge) then iptables may become
> involved, but by then hopefully it's okay.

Did test with 0 to bridge-nf-call-iptables, also did set /proc/sys/net/bridge/bridge-nf-filter-vlan-tagged as 0 but nothing changes, speed is still extreme slow betweeen DomU and Bacula.

  Pekka Panula, Net Servant Oy
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