[Xen-users] Network problem: packets are lost in domU

[Jacek Konieczny <jajcus@xxxxxxxxxx>]

Hello,

I am having big problems with Xen virtual network interfaces. First
I tried typical bridge support, no luck. The packets sent from dom0
to domU seemed to disappear somewhere. Then, to debug the problem
I have set up a simple point-to-point link and still have the same
problem.

I am using Xen 3.0.4-1 and Linux 2.6.16.x in both dom0 and domU.
I have tried kernel 2.6.16.35 and 2.6.16.41. 
I have compiled the kernel and xen with PAE support and without it,
using gcc 3.3 and gcc 4.2 (snapshot). I have played with various kernel
compilation options. No luck: the same problem in every case.

My system configuration:

in domain config file:

        vif = [ 'ip=192.168.16.2' ]

in xend-config.sxp:

        (network-script 'network-route netdev=dummy0')
        (vif-script     'vif-route netdev=dummy0')

dom0 interface setup:

# ip addr show dev dummy0
10: dummy0: <BROADCAST,NOARP,UP> mtu 1500 qdisc noqueue
    link/ether 1a:aa:f1:3f:c5:4e brd ff:ff:ff:ff:ff:ff
    inet 192.168.16.1/32 scope global dummy0
# ip addr show dev vif2.0
14: vif2.0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 32
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
    inet 192.168.16.1/32 brd 192.168.16.255 scope global vif2.0
# ip route show 192.168.16.2
192.168.16.2 dev vif2.0  scope link  src 192.168.16.1

domU interface setup:

# ip addr show dev eth0
2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:16:3e:32:a3:70 brd ff:ff:ff:ff:ff:ff
    inet 192.168.16.2/24 brd 192.168.16.255 scope global eth0
# ip route
192.168.16.0/24 dev eth0  proto kernel  scope link  src 192.168.16.2

And "ping" does not work in either direction. Tcpdump shows that frames
sent from dom0 do not reach domU. So does "ip":

# ip -s link show dev eth0
2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:16:3e:32:a3:70 brd ff:ff:ff:ff:ff:ff
    RX: bytes  packets  errors  dropped overrun mcast
    0          0        72      0       0       0
    TX: bytes  packets  errors  dropped carrier collsns
    2394       57       0       0       0       0

And there are errors in dmesg of domU for each package lost this way:

netfront: rx->offset: 12, size: 4294967295
netfront: rx->offset: 12, size: 4294967295
netfront: rx->offset: 12, size: 4294967295
netfront: rx->offset: 12, size: 4294967295
[...]

No other suspicious messages in dmesg of domU, nothing worying in dmesg
of dom0.

Any ideas or hints?

Greets,
        Jacek

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