[Xen-users] Re: PV DomUs can't get ip via dhcp

[X Waple <xwaple@xxxxxxxxx>]

I have fixed it by adding the PV DomU's vifX.0 interface to the bridge manually.
Could anybody tell which script/code should be responsible for doing this? then I can do further investigate.

# brctl addif xenbr1 vif1.0

On Tue, Nov 1, 2011 at 2:19 PM, X Waple <xwaple@xxxxxxxxx> wrote:

Hi guys,

I'm trying xen with Fedora (Xen 4.1.2 + Linux 3.1.0-5.fc16.x86_64), but hit some issue with getting dhcp ip for PV DomUs.

[1] host setup is like this (MACs and ip are substituted due to privacy):

[root@localhost ~]# cat /etc/sysconfig/network-scripts/ifcfg-em1
DEVICE="em1"
HWADDR="02:23:7D:1A:2B:16"
BRIDGE=xenbr1
BOOTPROTO="dhcp"
> NM_CONTROLLED="no"
[root@localhost ~]# cat /etc/sysconfig/network-scripts/ifcfg-xenbr1
DEVICE=xenbr1
TYPE=Bridge
BOOTPROTO=dhcp
>
so I get the bridge topo as:

[root@localhost ~]# brctl show
bridge name    bridge id        STP enabled    interfaces
xenbr1        8000.02237d1a2b16    no        em1

[root@localhost ~]# ifconfig -a
em1       Link encap:Ethernet  HWaddr 02:23:7D:1A:2B:16
         inet6 addr: fe80::4637:e6ff:fe6a:7bed/64 Scope:Link
         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
         RX packets:220585 errors:0 dropped:0 overruns:0 frame:0
         TX packets:65020 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:1000
         RX bytes:21377675 (20.3 MiB)  TX bytes:12133827 (11.5 MiB)
         Interrupt:20 Memory:fe400000-fe420000

lo        Link encap:Local Loopback
         inet addr:127.0.0.1  Mask:255.0.0.0
         inet6 addr: ::1/128 Scope:Host
         UP LOOPBACK RUNNING  MTU:16436  Metric:1
         RX packets:107 errors:0 dropped:0 overruns:0 frame:0
         TX packets:107 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:0
         RX bytes:7596 (7.4 KiB)  TX bytes:7596 (7.4 KiB)

xenbr1    Link encap:Ethernet  HWaddr 02:23:7D:1A:2B:16
         inet addr:192.168.0.20  Bcast:192.168.0.255  Mask:255.255.255.0
         inet6 addr: fe80::4637:e6ff:fe6a:7bed/64 Scope:Link
         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
         RX packets:218102 errors:0 dropped:0 overruns:0 frame:0
         TX packets:61087 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:0
         RX bytes:17253427 (16.4 MiB)  TX bytes:11510311 (10.9 MiB)

[2] after I started a centos 5 pv guest:

[root@localhost ~]# cat /etc/xen/centos-5-pv
name = "centos-5-pv"
maxmem = 1024
memory = 1024
vcpus = 1
bootloader = "/usr/bin/pygrub"
> > > vfb = [ 'type=vnc,vncunused=1,keymap=en-us,vnclisten=0.0.0.0' ]
disk = [ "tap:aio:/var/lib/xen/images/centos-5-pv.img,xvda,w" ]
vif = [ "mac=00:16:36:1e:2d:01,bridge=xenbr1,script=vif-bridge" ]
serial = "pty"

[root@localhost ~]# xl create -c /etc/xen/centos-5-pv

[root@localhost ~]# xl list
Name                                        ID   Mem VCPUs    State    Time(s)
Domain-0                                     0  4638     4     r-----     403.0
centos-5-pv                                  1  1024     1     -b----     166.8

I got the network interfaces like this:

[root@localhost ~]# brctl show
bridge name    bridge id        STP enabled    interfaces
xenbr1        8000.02237d1a2b16    no        em1

[root@localhost ~]# ifconfig -a
em1       Link encap:Ethernet  HWaddr 02:23:7D:1A:2B:16
         inet6 addr: fe80::4637:e6ff:fe6a:7bed/64 Scope:Link
         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
         RX packets:220585 errors:0 dropped:0 overruns:0 frame:0
         TX packets:65020 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:1000
         RX bytes:21377675 (20.3 MiB)  TX bytes:12133827 (11.5 MiB)
         Interrupt:20 Memory:fe400000-fe420000

lo        Link encap:Local Loopback
         inet addr:127.0.0.1  Mask:255.0.0.0
         inet6 addr: ::1/128 Scope:Host
         UP LOOPBACK RUNNING  MTU:16436  Metric:1
         RX packets:107 errors:0 dropped:0 overruns:0 frame:0
         TX packets:107 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:0
         RX bytes:7596 (7.4 KiB)  TX bytes:7596 (7.4 KiB)

vif1.0    Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
         inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
         RX packets:1046 errors:0 dropped:0 overruns:0 frame:0
         TX packets:26 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:32
         RX bytes:339763 (331.7 KiB)  TX bytes:7308 (7.1 KiB)

xenbr1    Link encap:Ethernet  HWaddr 02:23:7D:1A:2B:16
         inet addr:192.168.0.20  Bcast:192.168.0.255  Mask:255.255.255.0
         inet6 addr: fe80::4637:e6ff:fe6a:7bed/64 Scope:Link
         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
         RX packets:218102 errors:0 dropped:0 overruns:0 frame:0
         TX packets:61087 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:0
         RX bytes:17253427 (16.4 MiB)  TX bytes:11510311 (10.9 MiB)

After the PV guest boot up, it can't get ip from dhcp, I tried to capture the dhcp packets on the interfaces of em1, xenbr1 and vif1.0 by:
[root@localhost ~]#  tcpdump -i em1 port 67 or port 68

I can only see dhcp request packets on vif1.0, no request packets visible on em1 or xenb1. (selinux and iptables are disabled in both Dom0 and DomU).

[3] Then I started a HVM guest (DomId = 3), it can get ip successfully on the same host. I only see it's different that there are tap3.0 and vif3.0 interfaces created for the HVM guest, and tap3.0 is added in the bridge:

[root@localhost ~]# brctl show
bridge name    bridge id        STP enabled    interfaces
xenbr1        8000.02237d1a2b16    no        em1
                           tap3.0

Could someone tell me what I need to do further or explain to me how xen setup the network interfaces for PV guests compare to the HVM guests when using bridge mode?

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