[Xen-users] xen (3.0.3_0) + iptables in dom0

[Arnaud JAYET <ajayet@xxxxxxx>]

Hello,

I have little trouble with using iptables in dom0 with Xen 3.0.

i allow all OUTPUT and FORWARD in default iptables policy, the default 
policy for INPUT chain is DROP except for ssh in domO from fixed IPs in 
network 10.131.12.0/24
I've the following iptables script and network configuration (I'm using 
Debian Sarge) :
#!/bin/sh
# /etc/network/if-pre-up.d/iptables-start
iptables=$(which iptables)

$iptables -F

$iptables -P INPUT DROP
$iptables -P FORWARD ACCEPT
$iptables -P OUTPUT ACCEPT


$iptables -A INPUT -i lo -j ACCEPT
$iptables -A INPUT -p icmp -j ACCEPT
$iptables -A INPUT -p igmp -j ACCEPT

$iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT

# SSH
$iptables -A INPUT -p tcp -s 10.131.12.0/24 --dport 22 -j ACCEPT

---------

With this iptables configuration, i can't go out from dom0 (no ping, no 
ssh, no http for apt-get update/upgrade)
if i set the INPUT chain default policy to ACCEPT, it works of course 
(e.g. like no iptables ptrotection at all)...
I wonder why the output stream from dom0 is blocked (default policy = 
ACCEPT) ? Does the output stream initiated by dom0 re-enter into any 
INPUT chain due to the xen bridge or the renaming of eth0 in peth0 ? 
it's a little bit cloudy for me...
Does anybody have a sample iptables script for protecting a dom0 machine ?


My network configuration for the dom0 :


eth0      Lien encap:Ethernet  HWaddr 00:30:48:68:20:18
          inet adr:10.131.12.5  Bcast:10.131.255.255  Masque:255.255.0.0
          adr inet6: fe80::230:48ff:fe68:2018/64 Scope:Lien
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:657163 errors:0 dropped:0 overruns:0 frame:0
          TX packets:10908 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:0
          RX bytes:58172954 (55.4 MiB)  TX bytes:1811066 (1.7 MiB)

lo        Lien encap:Boucle locale
          inet adr:127.0.0.1  Masque:255.0.0.0
          adr inet6: ::1/128 Scope:Hôte
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:8 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:0
          RX bytes:560 (560.0 b)  TX bytes:560 (560.0 b)

peth0     Lien encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
          adr inet6: fe80::fcff:ffff:feff:ffff/64 Scope:Lien
          UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
          RX packets:664303 errors:0 dropped:0 overruns:0 frame:0
          TX packets:11059 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:1000
          RX bytes:61532959 (58.6 MiB)  TX bytes:1873537 (1.7 MiB)
          Adresse de base:0x2000 Mémoire:da200000-da220000

vif0.0    Lien encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
          adr inet6: fe80::fcff:ffff:feff:ffff/64 Scope:Lien
          UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
          RX packets:11009 errors:0 dropped:0 overruns:0 frame:0
          TX packets:662689 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:0
          RX bytes:1825551 (1.7 MiB)  TX bytes:58733912 (56.0 MiB)

xenbr0    Lien encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
          adr inet6: fe80::200:ff:fe00:0/64 Scope:Lien
          UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
          RX packets:646462 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:0
          RX bytes:46504320 (44.3 MiB)  TX bytes:0 (0.0 b)


# route
Table de routage IP du noyau
Destination     Passerelle      Genmask         Indic Metric Ref    Use 
Iface
localnet        *               255.255.0.0     U     0      0        0 eth0
default         10.131.255.254  0.0.0.0         UG    0      0        0 eth0


Thank you for your help.


--
Arnaud

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