Hello,

i'd like to understand more deeply xen networking.
My purpose is to modify the dscp ip field in guest's packet, to perform Qos, thanks to iptables.

I'm using a FC7 with xen 3.1.
I've installed a windows guest, with virt-manager, and I have used the default nat network option. Unfortunatelly, i couldn't use the bridge option because no network card was proposed! but this isn't the subject...

I was quite surprised when i saw, in my xen-config.sxp : (network-script : network-bridge). it should be network-nat, am I wrong?

the ifconfig command displays :

lo        Link encap:Boucle locale
          inet adr:127.0.0.1 Masque:255.0.0.0
          adr inet6: ::1/128 Scope:Hôte
          UP LOOPBACK RUNNING MTU:16436 Metric:1
          RX packets:731062 errors:0 dropped:0 overruns:0 frame:0
          TX packets:731062 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:0
          RX bytes:7695075004 (7.1 GiB) TX bytes:7695075004 (7.1 GiB)

tap0      Link encap:Ethernet HWaddr 82:E3:26:59:DC:BF
          adr inet6: fe80::80e3:26ff:fe59:dcbf/64 Scope:Lien
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:17783 errors:0 dropped:0 overruns:0 frame:0
          TX packets:513 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:500
          RX bytes:24458454 (23.3 MiB) TX bytes:181392 (177.1 KiB)

tmpbridge Link encap:Ethernet HWaddr 00:00:00:00:00:00
          inet adr: 192.168.1.5 Bcast:192.168.1.255 Masque:255.255.255.0
          adr inet6: fe80::200:ff:fe00:0/64 Scope:Lien
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:34 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:0
          RX bytes:0 (0.0 b) TX bytes:9046 ( 8.8 KiB)

vif11.0   Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF
          UP BROADCAST MULTICAST MTU:1500 Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:32
          RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)

virbr0    Link encap:Ethernet HWaddr 82:E3:26:59:DC:BF
          inet adr:192.168.122.1 Bcast:192.168.122.255 Masque:255.255.255.0
          adr inet6: fe80::200:ff:fe00:0/64 Scope:Lien
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:21958 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1377 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:0
          RX bytes:24771762 (23.6 MiB) TX bytes:304511 (297.3 KiB)

the "network-bridge status" displays :
============================================================
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: peth0: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:08:02:f5:71:e6 brd ff:ff:ff:ff:ff:ff
3: virbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
    link/ether 82:e3:26:59:dc:bf brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
    inet6 fe80::200:ff:fe00:0/64 scope link
       valid_lft forever preferred_lft forever
4: tmpbridge: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
    link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.5/24 brd 192.168.1.255 scope global tmpbridge
    inet6 fe80::200:ff:fe00:0/64 scope link
       valid_lft forever preferred_lft forever
21: vif11.0: <NO-CARRIER,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
22: tap0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 500
    link/ether 82:e3:26:59:dc:bf brd ff:ff:ff:ff:ff:ff
    inet6 fe80::80e3:26ff:fe59:dcbf/64 scope link
       valid_lft forever preferred_lft forever

it seems like the network-bridge scripts crashes, because the tmpbridge is not renamed, and when I start the xend service or when I run network-bridge start, the eth0 interface is disable!!

can anyone helps me debug this situation?

thanks