Am 08.07.2013 16:59, schrieb Sven Schwedas:
Hi,
I'm trying to configure nwfilter for KVM, but so far I haven't managed
to figure out a working configuration.
I had the same problem.
The linked rules produce the following iptables chains:
Chain INPUT (policy ACCEPT)
target prot opt source destination
libvirt-host-in all -- 0.0.0.0/0 0.0.0.0/0
ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:53
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:53
ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:67
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:67
Chain FORWARD (policy ACCEPT)
target prot opt source destination
libvirt-in all -- 0.0.0.0/0 0.0.0.0/0
libvirt-out all -- 0.0.0.0/0 0.0.0.0/0
libvirt-in-post all -- 0.0.0.0/0 0.0.0.0/0
ACCEPT all -- 0.0.0.0/0 192.168.128.160/28
ACCEPT all -- 192.168.128.160/28 0.0.0.0/0
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable
REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with
icmp-port-unreachable
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Chain FI-vnet0 (1 references)
target prot opt source destination
RETURN tcp -- 0.0.0.0/0 0.0.0.0/0 tcp spt:22 state
ESTABLISHED ctdir ORIGINAL
RETURN tcp -- 0.0.0.0/0 0.0.0.0/0 tcp spt:80 state
ESTABLISHED ctdir ORIGINAL
RETURN icmp -- 0.0.0.0/0 0.0.0.0/0 state
NEW,ESTABLISHED ctdir REPLY
RETURN udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:53 state
NEW,ESTABLISHED ctdir REPLY
DROP all -- 0.0.0.0/0 0.0.0.0/0
Chain FO-vnet0 (1 references)
target prot opt source destination
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:22 state
NEW,ESTABLISHED ctdir REPLY
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 state
NEW,ESTABLISHED ctdir REPLY
ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0 state ESTABLISHED
ctdir ORIGINAL
ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp spt:53 state
ESTABLISHED ctdir ORIGINAL
DROP all -- 0.0.0.0/0 0.0.0.0/0
Chain HI-vnet0 (1 references)
target prot opt source destination
RETURN tcp -- 0.0.0.0/0 0.0.0.0/0 tcp spt:22 state
ESTABLISHED ctdir ORIGINAL
RETURN tcp -- 0.0.0.0/0 0.0.0.0/0 tcp spt:80 state
ESTABLISHED ctdir ORIGINAL
RETURN icmp -- 0.0.0.0/0 0.0.0.0/0 state
NEW,ESTABLISHED ctdir REPLY
RETURN udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:53 state
NEW,ESTABLISHED ctdir REPLY
DROP all -- 0.0.0.0/0 0.0.0.0/0
Chain libvirt-host-in (1 references)
target prot opt source destination
HI-vnet0 all -- 0.0.0.0/0 0.0.0.0/0 [goto] PHYSDEV
match --physdev-in vnet0
Chain libvirt-in (1 references)
target prot opt source destination
FI-vnet0 all -- 0.0.0.0/0 0.0.0.0/0 [goto] PHYSDEV
match --physdev-in vnet0
Chain libvirt-in-post (1 references)
target prot opt source destination
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 PHYSDEV match
--physdev-in vnet0
Chain libvirt-out (1 references)
target prot opt source destination
FO-vnet0 all -- 0.0.0.0/0 0.0.0.0/0 [goto] PHYSDEV
match --physdev-out vnet0
What am I missing?
In my opinion the network filter rules of libvirt for GNU/Linux do not work.
I tested "libvirt-bin 0.9.8-2ubuntu17.10" and "libvirt-1.1.0" without success.
As you can see in your iptables output above, libvirt creates rules with the target
"RETURN" instead of "ACCEPT".
From the fine manual of iptables:
"RETURN means stop traversing this chain and resume at the next rule in the previous
(calling) chain."
Only one new libvirt chain is in the INPUT chain (libvirt-host-in).
The other three libvirt-in, libvirt-out, libvirt-in-post are in the forward
chain.
I have no idea what the concept should be.
I inserted the following rules in the INPUT chain _after_ the guest was started
and had success:
iptables -I INPUT 1 -j libvirt-out
iptables -I INPUT 1 -j libvirt-in-post
iptables -I INPUT 1 -j libvirt-in
iptables -I INPUT 1 -j libvirt-host-in
If you use the command:
iptables -nvL
instead of just
iptables -nL
you can see the number of packets that arrive in the different chains.
Then you can see that the number of returned packets increases and the packets end up in
the chain "libvirt-in-post" which finally ACCEPTs the packets.
To sum it up: file a bug report against libvirt and insert your own iptables
rules with -I in the mean time - if you know what you are doing.
Best regards
Hans Meier
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