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On Fri, 1 Aug 2008, Marco Lorig wrote:
With the tunnel in place, can you initiate an outbound
SSH connection from the realserver to the client machine?
Are you absolutely sure that the path this will follow
the same route as the data from the realserver under
normal conditions?
I have a sneaking feeling that the realserver is sending
packets of 1460 bytes (ethernet MTU less L2 framing) but
the "secondary" director, ie. the tunnel endpoint at the
realserver's end, is dropping them because they don't fit
inside the tunnel.
I do a scp both times only from the client to the server:
client:# scp file root@IPVSADM-address:/tmp/
This works. The client sends the first packets with a mtu
which doesn´t fit into the tunnel and recieves ICMP
UNREACHABLE Need to fragment.
client:# scp root@IPVSADM-address:/tmp/file .
This doesn´t work. The Realserver tries to send packets
which doesn´t fit into the tunnel but DOES NOT receive any
ICMP packet.
so ip_vs() is not handling icmp correctly at least for
LVS-NAT. Thanks for tracking this down. icmp handling has
been built into LVS since the really early days. I doubt if
gre was in anyone's mind at the time. I think it was mostly
for host unreachable.
Horms, Julian,
Is there a fix for this?
I tried setting sysctl nat_icmp_send to 1 but that doesn´t
change the behaviour at all.
ip_vs() does its own nat'ing, so using commands from
iptables will not help.
Joe
There was only one attempt which worked (the realserver
got an ICMP UNREACHABLE NEED TO FRAG) but unfortunately I
can´t reproduce it.
So the realserver is never going to realise that it´s
packets are too big.
I think, that´s the gist of the matter.
Any ideas?
Thanks in advance.
Have a nice weekend.
cheers
Marco
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