From: Eric Dumazet <eric.dumazet@gmail.com>
To: parasytic@gmail.com
Cc: jlyo@jlyo.org, netdev@vger.kernel.org, davem@davemloft.net
Subject: Re: Missing TCP SYN on loopback, retransmits after 1s
Date: Sat, 23 Mar 2013 09:58:05 -0700 [thread overview]
Message-ID: <1364057885.29473.4.camel@edumazet-glaptop> (raw)
In-Reply-To: <c873451a-71aa-418b-96e2-d8875e7fec3e@googlegroups.com>
On Fri, 2013-03-22 at 19:03 -0700, parasytic@gmail.com wrote:
> Hi List!
>
>
> First, I'm sorry for resurrecting an extremely old thread, but I've
> exhausted all other resources. We're experiencing this same "1 second
> retransmit" with ipv4 (including loopback). And the best part is, it
> can be replicated very easily using the 'closed' and 'tcping' tests
> provided by Jesse Young in the initial post. For reference:
>
>
> $ git clone git://github.com/jlyo/tcping.git
> $ cd tcping && make
>
>
> $ git clone git://github.com/jlyo/closed.git
> $ cd closed && make
>
>
> $ ./closed 0.0.0.0
>
>
> $ time ./tcping -f -p8009 0.0.0.0
>
>
> Results:
>
>
> ...
> response from 0.0.0.0:8009, seq=1907 time=0.02 ms
> response from 0.0.0.0:8009, seq=1908 time=0.03 ms
> response from 0.0.0.0:8009, seq=1909 time=999.11 ms
> --- 0.0.0.0:8009 ping statistics ---
> 1909 responses, 1910 ok, 0.00% failed
> round-trip min/avg/max = 0.0/0.6/999.1 ms
>
>
> real 0m1.125s
> user 0m0.008s
> sys 0m0.104s
>
>
>
>
> Packet captures from tcpdump look remarkably similar to what Eric
> Dumazet shared. That eventually lead me to this thread.
>
>
> This happens on a fresh Ubuntu 12.10 install, and also with our tuning
> parameters. (Includes increasing the syn backlog, open file
> descriptors, TCP memory, max orphans, etc.) I've also seen the
> problem with other kernels, within EC2 and Azure. I have not been able
> to test with ipv6 yet.
>
>
> $ uname -a
> Linux test 3.5.0-21-generic #32-Ubuntu SMP Tue Dec 11 18:51:59 UTC
> 2012 x86_64 x86_64 x86_64 GNU/Linux
>
>
> I'm hoping to spark some interest in revisiting this issue (with focus
> on ipv4, this time).
>
>
> Thanks everyone!
> Jay
>
Hi Jay
Not reproducible on current kernels (net-next tree for example)
ip netns add eric
ip netns exec eric ifconfig -a
ip netns exec eric ifconfig lo 127.0.0.1 up
ip netns exec eric ./closed 0.0.0.0 &
ip netns exec eric nstat
ip netns exec eric ./tcping -f -p8009 0.0.0.0
127.0.0.1:40832 Connected...response from 0.0.0.0:8009, seq=32799
time=0.04 ms
closed
127.0.0.1:40999 Connected...response from 0.0.0.0:8009, seq=32800
time=0.04 ms
closed
127.0.0.1:42795 Connected...response from 0.0.0.0:8009, seq=32801
time=0.20 ms
closed
127.0.0.1:43226 Connected...response from 0.0.0.0:8009, seq=32802
time=0.07 ms
closed
error connecting to host (99): Cannot assign requested address
................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
................................................................................................................................................................^C.--- 0.0.0.0:8009 ping statistics ---
33765 responses, 32803 ok, 0.00% failed
round-trip min/avg/max = 0.0/0.0/0.5 ms
# ip netns exec eric nstat
#kernel
IpInReceives 197087 0.0
IpInDelivers 197087 0.0
IpOutRequests 197087 0.0
TcpActiveOpens 32803 0.0
TcpPassiveOpens 32803 0.0
TcpInSegs 197087 0.0
TcpOutSegs 197084 0.0
TcpRetransSegs 3 0.0
TcpOutRsts 11 0.0
TcpExtSyncookiesFailed 11 0.0
TcpExtDelayedACKs 238 0.0
TcpExtDelayedACKLocked 248 0.0
TcpExtTCPPureAcks 65838 0.0
TcpExtTCPTimeouts 3 0.0
IpExtInOctets 10773240 0.0
IpExtOutOctets 10773240 0.0
But yes, on 3.5.X kernel you might hit a bug somewhere.
Since the same sequence gives suspect TcpExtListenDrops :
# ip netns exec eric nstat
#kernel
IpInReceives 49367 0.0
IpInDelivers 49367 0.0
IpOutRequests 49367 0.0
TcpActiveOpens 8184 0.0
TcpPassiveOpens 8184 0.0
TcpInSegs 49367 0.0
TcpOutSegs 49362 0.0
TcpRetransSegs 5 0.0
TcpExtDelayedACKs 63 0.0
TcpExtDelayedACKLocked 32 0.0
TcpExtListenOverflows 4 0.0
TcpExtListenDrops 4 0.0
TcpExtTCPPureAcks 16624 0.0
TcpExtTCPLossUndo 1 0.0
TcpExtTCPTimeouts 5 0.0
IpExtInOctets 2698036 0.0
IpExtOutOctets 2698036 0.0
next prev parent reply other threads:[~2013-03-23 16:58 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-23 0:13 Missing TCP SYN on loopback, retransmits after 1s Jesse Young
2011-11-23 0:23 ` David Miller
2011-11-23 0:37 ` Jesse Young
2011-11-23 1:44 ` Hagen Paul Pfeifer
2011-11-23 14:38 ` Eric Dumazet
2011-11-23 22:29 ` David Miller
[not found] ` <c873451a-71aa-418b-96e2-d8875e7fec3e@googlegroups.com>
2013-03-23 16:58 ` Eric Dumazet [this message]
2013-03-23 19:17 ` Jason Oster
2013-03-24 0:08 ` Jason Oster
2011-11-23 2:06 ` John Heffner
2011-11-23 5:24 ` Eric Dumazet
2011-11-23 5:58 ` Eric Dumazet
2011-11-23 6:09 ` Eric Dumazet
2011-11-23 6:13 ` Eric Dumazet
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