Re: cups slow on linux-2.6.24

Jozsef Kadlecsik
2008-02-02T14:44:43Z

Hi Jeff,

On Fri, 1 Feb 2008, Jeff Chua wrote:

> I recaptured it again, and attached are the logs.
[...]

Thank you! One can see a plain connection-initiating SYN, which triggers
the message. No reply from the server, then three seconds later comes a
retransmitted SYN and immediately after the SYN/ACK reply. What makes it
interesting is that the first SYN was let through by the conntrack: it was
*not* blocked at all.

In the dump file there is no other previous connection between
127.0.0.1:1021 -> 127.0.0.1:515. But there must be a previous connection
which was not captured by tcpdump.

Could I ask you to make two another tests? (I have been unable to
reproduce the bug so far, but it must be my fault.) In both cases enable
loggin invalid messages as Patrick wrote in a previous mail:

# modprobe ipt_LOG
# echo 255 >/proc/sys/net/netfilter/nf_conntrack_log_invalid

In the first case run the unpatched 2.4.24 kernel and before doing
any printing, start dumping all the traffic at the 515 port so that we
won't miss any connection and send the dump file:

# tcpdump -i lo -s 0 -w dump.pcap tcp port 515

In the second case run the patched kernel and just start printing: do you
get any 'nf_ct_tcp: invalid SYN' kernel message?

Best regards,
Jozsef
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