Sven Riedel wrote:
Hi,
I've run into a strange problem where large file transfers start
stalling over a NATed connection. Packet traces reveal that ACK
packets are sometimes not being passed through to the inside (NATed)
host, which results in a transfer stall until a tcp timeout occurrs
and the other side retransmits the ACK.
This only seems to happen if the conntrack table on the firewall
already contains an entry for the same source and destination in
TIME_WAIT state. If no conntrack entries exist for the same source and
destination, the packets flow fine.
The problem seems to be alevated by setting ip_conntrac_tcp_be_liberal
to 1, but this seems to be only a workaround not a real solution.
Scatter gather and tcp segment offloading have been disabled in the
relevant NICs on the firewall during debugging, to make sure this
isn't a hardware issue.
Is this issue known/is there a patch available or would further
information be needed to help debug the problem?
2.6.24.3 includes a patches that was supposed to fix problems
with connections in TIME_WAIT state. Does 2.6.24.2 work better
for you?
Please enable conntrack logging for TCP by executing:
echo 6 >/proc/sys/net/netfilter/nf_conntrack_log_invalid
and check whether you get any messages in the ring buffer.
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