Re: [Xen-users] newbie in trouble with CentOS Xen

[Alexandre Kouznetsov <alk@xxxxxxxxxx>]

Hello.

El 04/04/13 10:13, Dave Stevens escribió:
> [root@skeena ~]# xm list
> Name                                      ID Mem(MiB) VCPUs State   Time(s)
> Domain-0                                   0     9879     8 r-----    870.8
> bulkley                                    1     2048     4 -b----   3283.0
> [root@skeena ~]#
>
> [root@skeena ~]# brctl show
> bridge name    bridge id        STP enabled    interfaces
> virbr0        8000.000000000000    yes
> xenbr0        8000.feffffffffff    no        vif1.0
>                              vif0.0
>                              peth0
> xenbr1        8000.feffffffffff    no        vif1.1
>                              vif0.1
>                              peth1
This tells us what Domains have network interfaces in what bridges.
It seems like there is a mix of configurations. Looks fine, for a 
bridged networking (not NATted, see below), except there might be a 
problem with peth0 and peth1.
> [root@skeena ~]# ifconfig
> eth1      Link encap:Ethernet  HWaddr 00:30:48:CE:84:7F
>            inet addr:10.10.254.240  Bcast:10.10.254.255  Mask:255.255.255.0
>            inet6 addr: fe80::230:48ff:fece:847f/64 Scope:Link
>            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>            RX packets:81102 errors:0 dropped:0 overruns:0 frame:0
>            TX packets:34828 errors:0 dropped:0 overruns:0 carrier:0
>            collisions:0 txqueuelen:0
>            RX bytes:10772813 (10.2 MiB)  TX bytes:2721383 (2.5 MiB)
>
> 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:3086 errors:0 dropped:0 overruns:0 frame:0
>            TX packets:3086 errors:0 dropped:0 overruns:0 carrier:0
>            collisions:0 txqueuelen:0
>            RX bytes:4816900 (4.5 MiB)  TX bytes:4816900 (4.5 MiB)
>
> peth0     Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
>            UP BROADCAST NOARP  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 txqueuelen:1000
>            RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
>            Interrupt:250 Base address:0xc000
>
> peth1     Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
>            inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
>            UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
>            RX packets:42346 errors:0 dropped:0 overruns:0 frame:0
>            TX packets:73652 errors:0 dropped:0 overruns:0 carrier:0
>            collisions:0 txqueuelen:1000
>            RX bytes:9145360 (8.7 MiB)  TX bytes:5504883 (5.2 MiB)
>            Interrupt:251 Base address:0xe000
This is weired.

The common way to give network to DomUs is to define a bridge, put the 
physical interface into it permanently, and plug DomU's interfaces there 
ion demand (you probably found that in the Wiki).
The very old network-bridge xen script was defining the bridges as 
following:
save IP configuration from eth0,
rename eth0 to peth0 (aka "physical eth0"),
create bridge called "eth0" (now that the name is free),
set IP configuration it took from the physical eth0 on the new bridge.

That way, before xend was brought up you had a plain eth0 to your 
network. After xend startup you had the same eth0 to your network. This 
proved to be little bit confusing and the configuration scripts produced 
unstable results, so late Xen documentation suggests to set up bridges 
using you platform means, and just tell Xen what bridge to use for what 
DomU's NIC.
Check this oldier wiki http://wiki.xensource.com/xenwiki/XenNetworking. 
It probably reflect better your scenario (and imho has nicer pictures)
What I see here are peth0 and peth1, they are supposed to be physical 
interfaces with a valid MAC, and be of the same nature. Actually, they 
have HWaddr FE:FF:FF:FF:FF:FF and one of them have a inet6 addr. eth1 
seems to be a plain physical interface (I bet it's the one you use to 
connect to your server) while a bridge called "eth1" is expected. eth0 
is simply missing.

Please tell me, how many physical network cards does your server have? 
How are they supposed to be used? Was any physical NIC added or removed 
recently? Maybe some NIC just died? The change of NIC number could 
confuse the network-script that badly. Did I told it was unstable?
It would be of great reference if you attach your DomU .cfg (under 
/etc/xen) file and /etc/xen/xend-config.sxp (I took the path form a 
Debian, it may be different in CentOS).
Please check what version of this components do you have installed:
Xen hypervisor
Linux kernel
xenutils (the name of package may be different in CentOS)
xentools (the name of package may be different in CentOS)

> [root@skeena ~]# iptables -L -v
> [...]
>      0     0 ACCEPT     all  --  any    virbr0  anywhere
> 192.168.122.0/24    state RELATED,ESTABLISHED
>      0     0 ACCEPT     all  --  virbr0 any     192.168.122.0/24
> anywhere
>      0     0 ACCEPT     all  --  virbr0 virbr0  anywhere
> anywhere
>      0     0 REJECT     all  --  any    virbr0  anywhere
> anywhere            reject-with icmp-port-unreachable
>      0     0 REJECT     all  --  virbr0 any     anywhere
> anywhere            reject-with icmp-port-unreachable
This must be the rules to restrict traffic within a bridge, dedicated to 
internal communication between Dom0 and DomU's. Unused, apparently. The 
rest of ipfilter configuration is permissive, so it shall not be the issue.

As the general solution to your problem, in case you just want to "make 
it work back" and not doing any new implementation (Dom0 OS and Xe 
upgrade would be probably cleaner if reinstalled), I would suggest to 
re-do the networking configuration.
Probably your DomU was configured with NATted networking, when it broke 
Dom0 kept it' sexternal IP address. The bridged networking is simpler 
and easer to debug.
Greetings.

--
Alexandre Kouznetsov


_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxx
http://lists.xen.org/xen-users