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Re: [Xen-users] network (NAT?) problem

To: Markus Lude <lude@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
From: James Bulpin <James.Bulpin@xxxxxxxxxxxx>
Date: Sun, 26 Jun 2005 11:44:33 +0100
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Delivery-date: Sun, 26 Jun 2005 10:43:36 +0000
List-id: Xen user discussion <xen-users.lists.xensource.com>

Marcus,

Thanks for the details. I have a suspicion that there may be an issuewith connection tracking. Each packet from dom2 to the outside worldmakes two passages through dom0: once when traversing xen-br1 goingbetween dom2 and dom1 and once when coming in from dom1 to dom0. I'mwondering is connection tracking is getting confused. I'm going to tryto replicate this configuration and investigate.


James

Markus Lude wrote:

On Thu, Jun 23, 2005 at 10:55:11AM +0100, James Bulpin wrote:
Markus,
You say the routing of packets between dom2 and dom0 doesn't work asintended - can you elaborate on this, i.e. where do packets get to, doyou see them if you tcpdump eth1 and eth0 in dom1?
Ehm, the routing between dom2 and dom0 _does_ work, but something with NAT
in dom0 seems to go wrong for packets from dom2. I see the traffic between
dom0 and dom2 on the interfaces in dom1.
Do you have any IP tables rules in dom0 that would affect packets onxen-br1?
Can you post the following for all domains:
- iptables details (both nat and filter tables)
- routing tables
- ifconfig
- cat /proc/sys/net/ipv4/ip_forward
dom2

xsarge2:~# iptables -nvL -t filter
modprobe: QM_MODULES: Function not implemented

modprobe: QM_MODULES: Function not implemented

modprobe: Can't locate module ip_tables
iptables v1.2.11: can't initialize iptables table `filter': iptables who? (do 
you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.

xsarge2:~# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
172.30.1.0      0.0.0.0         255.255.255.0   U     0      0        0 eth0
0.0.0.0         172.30.1.21     0.0.0.0         UG    0      0        0 eth0

xsarge2:~# ifconfig
eth0 Link encap:Ethernet HWaddr 0A:00:00:00:01:20inet addr:172.30.1.22 Bcast:172.30.255.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:61 errors:0 dropped:0 overruns:0 frame:0
          TX packets:79 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000RX bytes:5866 (5.7 KiB) TX bytes:6622 (6.4 KiB)
lo Link encap:Local Loopbackinet addr:127.0.0.1 Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:22 errors:0 dropped:0 overruns:0 frame:0
          TX packets:22 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0RX bytes:2328 (2.2 KiB) TX bytes:2328 (2.2 KiB)
xsarge2:~# cat /proc/sys/net/ipv4/ip_forward
1

---------------------------------------
dom1

xsarge1:~# iptables -nvL -t filter
modprobe: QM_MODULES: Function not implemented

modprobe: QM_MODULES: Function not implemented

modprobe: Can't locate module ip_tables
iptables v1.2.11: can't initialize iptables table `filter': iptables who? (do 
you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.

xsarge1:~# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
172.30.1.0      0.0.0.0         255.255.255.0   U     0      0        0 eth0
172.30.0.0      0.0.0.0         255.255.255.0   U     0      0        0 eth1
0.0.0.0         172.30.0.1      0.0.0.0         UG    0      0        0 eth1

xsarge1:~# ifconfig
eth0 Link encap:Ethernet HWaddr 0A:00:00:00:01:10inet addr:172.30.1.21 Bcast:172.30.255.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:61 errors:0 dropped:0 overruns:0 frame:0
          TX packets:72 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000RX bytes:5866 (5.7 KiB) TX bytes:6328 (6.1 KiB)
eth1 Link encap:Ethernet HWaddr 0A:00:00:00:10:11inet addr:172.30.0.21 Bcast:172.30.255.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:17 errors:0 dropped:0 overruns:0 frame:0
          TX packets:22 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000RX bytes:1330 (1.2 KiB) TX bytes:1820 (1.7 KiB)
lo Link encap:Local Loopbackinet addr:127.0.0.1 Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:30 errors:0 dropped:0 overruns:0 frame:0
          TX packets:30 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0RX bytes:2996 (2.9 KiB) TX bytes:2996 (2.9 KiB)
xsarge1:~# cat /proc/sys/net/ipv4/ip_forward
1

---------------------------------------
dom0: arras

arras:~# iptables -nvL -t filter
Chain INPUT (policy ACCEPT 6004 packets, 450K bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 123 packets, 10332 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 5312 packets, 338K bytes)
pkts bytes target prot opt in out source destinationarras:~# iptables -nvL -t natChain PREROUTING (policy ACCEPT 1866 packets, 401K bytes)pkts bytes target prot opt in out source destination
Chain POSTROUTING (policy ACCEPT 82 packets, 6653 bytes)
pkts bytes target prot opt in out source destination0 0 MASQUERADE all -- * xen-br0 172.30.0.0/16 0.0.0.0/0
Chain OUTPUT (policy ACCEPT 22 packets, 1613 bytes)
pkts bytes target prot opt in out source destinationarras:~# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
172.30.1.0      172.30.0.21     255.255.255.0   UG    0      0        0 xen-br10
172.30.0.0      0.0.0.0         255.255.255.0   U     0      0        0 xen-br10
134.2.8.0       0.0.0.0         255.255.248.0   U     0      0        0 xen-br0
0.0.0.0         134.2.15.254    0.0.0.0         UG    0      0        0 xen-br0

arras:~# ifconfig
eth0 Link encap:Ethernet HWaddr 00:0D:56:83:0C:A9inet addr:134.2.11.153 Bcast:134.2.15.255 Mask:255.255.248.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:49972 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1000 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000RX bytes:4690589 (4.4 MiB) TX bytes:95473 (93.2 KiB)Base address:0xdf40 Memory:feae0000-feb00000lo Link encap:Local Loopbackinet addr:127.0.0.1 Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:4937 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4937 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0RX bytes:308890 (301.6 KiB) TX bytes:308890 (301.6 KiB)
vif1.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FFUP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:116 errors:0 dropped:0 overruns:0 frame:0
          TX packets:61 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0RX bytes:8176 (7.9 KiB) TX bytes:5866 (5.7 KiB)
vif1.1 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FFUP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:93 errors:0 dropped:0 overruns:0 frame:0
          TX packets:65 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0RX bytes:8050 (7.8 KiB) TX bytes:5866 (5.7 KiB)
vif2.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FFUP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:105 errors:0 dropped:0 overruns:0 frame:0
          TX packets:61 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0RX bytes:7714 (7.5 KiB) TX bytes:5866 (5.7 KiB)
xen-br0 Link encap:Ethernet HWaddr 00:0D:56:83:0C:A9inet addr:134.2.11.153 Bcast:134.2.15.255 Mask:255.255.255.255
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:46551 errors:0 dropped:0 overruns:0 frame:0
          TX packets:989 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0RX bytes:2681480 (2.5 MiB) TX bytes:89935 (87.8 KiB)
xen-br1 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FFUP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:1 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0RX bytes:28 (28.0 b) TX bytes:0 (0.0 b)
xen-br10 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FFinet addr:172.30.0.1 Bcast:172.30.255.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:65 errors:0 dropped:0 overruns:0 frame:0
          TX packets:65 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0RX bytes:5964 (5.8 KiB) TX bytes:5866 (5.7 KiB)
arras:~# cat /proc/sys/net/ipv4/ip_forward
1
And brctl show for dom0.
arras:~# brctl show
bridge name     bridge id               STP enabled     interfaces
xen-br0         8000.000d56830ca9       no              eth0
xen-br10                8000.feffffffffff       no              vif1.1
xen-br1         8000.feffffffffff       no              vif1.0
                                                        vif2.0

hmm, is it normal, that xen-br1 and xen-br10 have the same bridge id?
If not, any hints were to change them?
Thanks,

James
Regards,
Markus
Markus Lude wrote:
Hello,

my current network setup looks like the following:

  dom2-eth0 (172.30.1.22) netmask /24
      |
      | xen-br1 (no ip)
      |
  dom1-eth0 (172.30.1.21) netmask /24
  dom1-eth1 (172.30.0.21) netmask /24
      |
      | xen-br10 (172.30.0.1) netmask /24
      |
    dom0
      |
      | xen-br0 (normal IP)
      |
     eth0 (same IP as xen-br0)
      |
      |
     LAN

Basically I want to route all traffic between dom0 and dom2 through dom1.
This does work as intended.
I further would like to have access to the LAN from dom1 and dom2 through
NAT in dom0. It works for dom1, but not for dom2. The addresses of packets
from dom2 were not changed (noticed with tcpdump -n -i eth0 in dom0).
In dom0 NAT is set up with:
iptables -t nat -A POSTROUTING -s 172.30.0.0/16 -o xen-br0 -j MASQUERADE

If I leave out the -s parameter nothing changes.

I'm running debian sarge in all doms and xen-2.0.6.

Any suggestions? What am I missing?

Regards,
Markus Lude
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References:
- [Xen-users] network (NAT?) problem
  - From: Markus Lude
- Re: [Xen-users] network (NAT?) problem
  - From: James Bulpin
- Re: [Xen-users] network (NAT?) problem
  - From: Markus Lude

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