Re: [Xen-users] Re: [Xen-devel] xen 4.1.2* dhcp issue/bug when installing/booting HVM domU domains (CentOS 6, unbuntu 11.04 server). Debian/OpenSolaris work fine.

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Tue, Aug 16, 2011 at 01:16:18AM +0200, Mark Schneider wrote:
> Am 16.08.2011 00:57, schrieb Mark Schneider:
>> Am 16.08.2011 00:23, schrieb Pasi Kärkkäinen:
>>> On Mon, Aug 15, 2011 at 11:58:24PM +0200, Mark Schneider wrote:
>>>>>
>>>>>>      Pings from *centos-hvm* to default gateway *no ip-traffic 
>>>>>> on peth0*
>>>>>>
>>>>>>
>>>>> So here's your problem. Your bridge in dom0 is NOT forwarding the 
>>>>> packets out to peth0..
>>>>>
>>>>>
>>>>>
>>>>>>      root@xen411dom0:/ftp/HVM# tcpdump  -i eth0 'icmp[icmptype] 
>>>>>> = icmp-echo and
>>>>>>      icmp[icmptype] != icmp-echoreply'
>>>>>>      tcpdump: verbose output suppressed, use -v or -vv for full 
>>>>>> protocol decode
>>>>>>      listening on eth0, link-type EN10MB (Ethernet), capture 
>>>>>> size 65535 bytes
>>>>>>      19:54:00.770442 IP 192.168.1.180>   192.168.1.1: ICMP echo 
>>>>>> request, id 518,
>>>>>>      seq 23, length 64
>>>>>>      19:54:01.770958 IP 192.168.1.180>   192.168.1.1: ICMP echo 
>>>>>> request, id 518,
>>>>>>      seq 24, length 64
>>>>>>
>>>>> So where are these packets going to ? They're not getting out of  
>>>>> dom0..
>>>>>
>>>>> Do you have a firewall rule in dom0 that drops them?
>>>>>
>>>>> Try these:
>>>>> - In the HVM guest: run "arp -an" and check what MAC address you  
>>>>> see for the gateway-IP.
>>>>> - In dom0: run "brctl showmacs eth0" and verify which port has 
>>>>> the MAC of the gateway.
>>>>>
>>>> [root@centoshvm ~]# arp -an
>>>> ? (192.168.1.102) auf 00:1c:25:7e:fb:b7 [ether] auf eth0
>>>> ? (192.168.1.124) auf b4:99:ba:c1:27:36 [ether] auf eth0
>>>>
>>> So the HVM guest has NOT received a MAC address for the gateway..
>>> so ARP requests are not working from the HVM guest.
>>>
>>> Do this:
>>> - Shutdown the VM.
>>> - Start the VM.
>>> - Run tcpdump in dom0 (tcpdump -i tap<x>  -nn)
>>> - Try pinging the gateway from the HVM guest.
>>> - Paste the whole tcpdump output here.
>>>
>>>
>>>> root@xen411dom0:~# brctl showmacs eth0
>>>> port no mac addr                is local?       ageing timer
>>>>    6     00:16:3e:27:17:67       no                 3.22
>>>>    3     00:16:3e:27:20:67       no                40.85
>>>>    1     00:1c:25:7e:fb:b7       no                 0.00
>>>>    1     00:1d:7e:ad:35:a8       no                12.66
>>>>    1     b4:99:ba:c1:27:36       yes                0.00
>>>>    2     fe:ff:ff:ff:ff:ff       yes                0.00
>>>> root@xen411dom0:~# arp -an
>>>> ? (192.168.1.102) auf 00:1c:25:7e:fb:b7 [ether] auf eth0
>>>> ? (192.168.1.180) auf 00:16:3e:27:17:67 [ether] auf eth0
>>>> ? (192.168.1.1) auf 00:1d:7e:ad:35:a8 [ether] auf eth0
>>>>
>>> Are you running some firewall (iptables or ebtables) in dom0 ?
>> No. It is plane wheezy with 3.0.1 kernel
>>

and "iptables -L -n -v" does not list any rules? 

>
> Trace inside HVM (s. default gateway: 192.168.1.1 is-at 00:1d:7e:ad:35:a8)
> # ---------------------------
> [root@centoshvm ~]# tcpdump -i eth0 -nn | tee /tmp/tcpdum-eth0.txt
> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
> listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
> 01:05:31.996278 IP 192.168.1.180.22 > 192.168.1.124.40173: Flags [P.],  
> seq 1128465923:1128466115, ack 1021543041, win 135, options [nop,nop,TS  
> val 1036128 ecr 3459996], length 192
> 01:05:31.998526 IP 192.168.1.124.40173 > 192.168.1.180.22: Flags [.],  
> ack 192, win 176, options [nop,nop,TS val 3460006 ecr 1036128], length 0
> 01:05:55.401107 ARP, Request who-has 192.168.1.1 tell 192.168.1.180,  
> length 28
> 01:05:55.402608 ARP, Reply 192.168.1.1 is-at 00:1d:7e:ad:35:a8, length 46
> 01:05:55.402681 IP 192.168.1.180 > 192.168.1.1: ICMP echo request, id  
> 5894, seq 1, length 64
> 01:05:56.399192 IP 192.168.1.180 > 192.168.1.1: ICMP echo request, id  
>

So the HVM domU gets the correct MAC of the gateway,
and starts sending packets to it.

The next step would be to dump on eth0 on dom0.. do you see the same packets 
there? 

At the same time also dump on peth0, do the packets go out there to the 
physical network? 


-- Pasi


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