[Xen-users] Can't access the domU's from the LAN (only from the dom0)

[Jaume Sabater <jsabater@xxxxxxxxxxxxx>]

Hello everyone!

I have a machine with two network interfaces, eth0 and eth1. Eth0 is 
connected to the LAN  (192.168.1.0/24) and eth1 to my router 
(ip:80.36.214.x, gw: 80.36.214.y). This server is acting as a 
proxy-cache as well. I also have a VPN between the two
subnets 192.168.0.0/24 and 192.168.1.0/24.

I have a running kernel 2.6.16.19 with Xen 3.0.2 on a Debian x86_64 Sid
(custom kernel). I want to use Xen virtual machines only internally (as 
any other normal PC inside the 192.168.1.0/24 network, but with no need 
to be accessed from the Internet). So, I have created a virtual machine 
using the xen-tools package provided by Steve:
[1] http://packages.debian.org/unstable/utils/xen-tools

These are the parameters of /etc/xen-tools/xen-tools.conf:

dir         = /home/xen
debootstrap = 1
size        = 2Gb
memory      = 128Mb
swap        = 256Mb
fs          = ext3
dist        = etch
image       = sparse
gateway     = 192.168.1.3
netmask     = 255.255.255.0
passwd      = 1
kernel      = /boot/xen0-linux-2.6.16.19-xen
initrd      =
mirror      = http://ftp.se.debian.org/debian/

I created the image with this command:

xen-create-image --hostname=xen01 --ip=192.168.1.10 --passwd

The /etc/network/interfaces in the virtual machine (dom1):

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
 address 192.168.1.10
 gateway 192.168.1.3
 netmask 255.255.255.0

Everything went fine:

- I can connect to the virtual machine from the host (192.168.1.3)
- I can connect to the Internet from inside the virtual machine.

But:

- I can't ping the virtual machine 192.168.1.10 from any other PC in the
192.168.1.0/24 network (but the host 192.168.1.3). It says "Destination
Host Unreachable".
- I can't ping any host in the 192.168.1.0/24 network from inside the
virtual machine 192.168.1.10. It does not complain, though.

I have set up /etc/xen/xend-config.sxp using:

(network-script network-route)
(vif-script     vif-route)

Honestly, I don't have any other reason to choose routing instead of
bridging except the fact that I tried for days and days with the
bridging thing and I could make it work, so I said "next try another
option".

When I was using bridging, I could ping from inside a VM to a PC, but
not from a PC to the VM. Again, I could really tell what was wrong (I am
not an expert with iptables, I admit it).

My firewall looks like this (short version):

BOF ----------------------------

iptables --policy INPUT DROP
iptables --append INPUT --in-interface ! eth1 --jump ACCEPT
iptables --append INPUT --match state --state ESTABLISHED,RELATED \
            --jump ACCEPT
iptables --append INPUT --proto ICMP --jump ACCEPT

# SSH
iptables --append INPUT --proto tcp --match state --dport ssh \
            --state NEW --source a.b.c.d --jump ACCEPT

# VPN
iptables --append INPUT --in-interface eth1 --proto udp \
            --sport isakmp --dport isakmp --source 213.96.x.y \
            --destination ${VPN_SRC} --jump ACCEPT
iptables --append INPUT --in-interface eth1 --proto tcp \
            --sport isakmp --dport isakmp --source 213.96.x.y \
            --destination 80.36.x.y --jump ACCEPT
iptables --append INPUT --in-interface eth1 --proto ah \
            --source 213.96.x.y --destination 80.36.x.y --jump ACCEPT
iptables --append INPUT --in-interface eth1 --proto esp \
            --source 213.96.x.y --destination 80.36.x.y --jump ACCEPT

# Transparent proxy
iptables --table nat --append PREROUTING --in-interface eth0 \
         --source 192.168.1.0/24 --destination ! 192.168.1.0/24 \
         --proto tcp --dport 80 --jump REDIRECT --to-port 3128

# Activate Network Address Translation
/bin/echo "1" > /proc/sys/net/ipv4/ip_forward
iptables --table nat --append POSTROUTING --source 192.168.1.0/24 \
         --destination ! 192.168.0.0/24 --out-interface eth1 \
         --jump MASQUERADE

EOF ----------------------------

80.36.x.y is the gateway in the machine (my end)
213.96.x.y is the gateway of the other end of the VPN

So, as far as I know, after reading as many docs as Google could provide
me with, I guess the problem is that traffic is not "routed" from the
eth0 to the vif. My ifconfig (summarized version) looks like this:

eth0   Link encap:Ethernet  HWaddr ------
       inet addr:192.168.1.3  Bcast:192.168.1.255  Mask:255.255.255.0
eth1   Link encap:Ethernet  HWaddr ------
       inet addr:80.36.x.y  Bcast:80.36.214.191  Mask:255.255.255.224
lo     Link encap:Local Loopback
       inet addr:127.0.0.1  Mask:255.0.0.0
vif3.0 Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
       inet addr:192.168.1.3  Bcast:192.168.1.255  Mask:255.255.255.255

Also, as a final note, when I was attempting to make it work by using
bridging, my server stopped forwarding connections from the LAN to the
Internet, so that was one more reason to try the "routed" setup. At
least now I can let people work while I try to finish up this setup and
don't have to go to the office on Saturday :)

Any hints? If you need any more information, please let me know. Thanks
in advance.

--
Jaume Sabater
http://linuxsilo.net/

"Ubi sapientas ibi libertas"

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