Il 26/10/2011 21:43, Julian Anastasov ha scritto:
I looked at broken-spoofing-server.pcap and
broken-spoofing-client.pcap
It looks like that this packet comes after some
packet that is dropped before server:
IP 2.119.245.36.80> 88.38.77.130.39243: Flags [P.], seq 1449:1534, ack 602, win 438, options [nop,nop,TS val 17124611 ecr 56937089], length 85
May be the seq 1:1449 packet can not reach 2.119.245.36.80,
that is why it does not go to client 88.38.77.130.39243.
May be server is a virtual server or something like that.
I guess someone before 2.119.245.36.80 is sending
large packets and some MTU is low and may be due to missing
ICMP the sender there can not learn the lower path MTU.
May be client can use ip route add ... advmss 1400 to check
if problem is fixed that way. May be there is some tunnel
behind the server that uses lower MTU.
Note that some 3.0.X kernels have problem that
ICMP is not sent and this can cause PMTU problems.
SOLVED! Thanks Julian Anastasov.
Niccolò