From: Eric Dumazet <eric.dumazet@gmail.com>
To: John Heffner <johnwheffner@gmail.com>
Cc: Jesse Young <jlyo@jlyo.org>, netdev@vger.kernel.org
Subject: Re: Missing TCP SYN on loopback, retransmits after 1s
Date: Wed, 23 Nov 2011 06:58:31 +0100 [thread overview]
Message-ID: <1322027911.1298.4.camel@edumazet-laptop> (raw)
In-Reply-To: <1322025880.29324.1.camel@edumazet-laptop>
Le mercredi 23 novembre 2011 à 06:24 +0100, Eric Dumazet a écrit :
> Le mardi 22 novembre 2011 à 21:06 -0500, John Heffner a écrit :
> > Offhand, I'd guess you're overflowing the TCP SYN queue. (You can try
> > tuning tcp_max_syn_backlog.)
> >
>
> There is one litle thing called "netstat -s", a very useful tool,
> included in many distros :)
This is related to TIMEWAIT syndrom ?
06:47:42.090522 IP6 ::1.49374 > ::1.8009: Flags [SEW], seq 2646115915, win 32752, options [mss 16376,sackOK,TS val 26574090 ecr 0,nop,wscale 6], length 0
06:47:42.090579 IP6 ::1.8009 > ::1.49374: Flags [S.E], seq 184529170, ack 2646115916, win 32728, options [mss 16376,sackOK,TS val 26574090 ecr 26574090,nop,wscale 6], length 0
06:47:42.090616 IP6 ::1.49374 > ::1.8009: Flags [.], ack 1, win 512, options [nop,nop,TS val 26574090 ecr 26574090], length 0
06:47:42.090718 IP6 ::1.8009 > ::1.49374: Flags [F.], seq 1, ack 1, win 512, options [nop,nop,TS val 26574090 ecr 26574090], length 0
06:47:42.090780 IP6 ::1.49374 > ::1.8009: Flags [F.], seq 1, ack 2, win 512, options [nop,nop,TS val 26574090 ecr 26574090], length 0
06:47:42.090843 IP6 ::1.8009 > ::1.49374: Flags [.], ack 2, win 512, options [nop,nop,TS val 26574090 ecr 26574090], length 0
First connection went well.
Now we try to reuse tuple (ports 49374, 8009 on loopback) while a socket is in TIMEWAIT, and first
SYN packet (time 06:48:20.337335) is dropped (considered as a packet part of previous session)
Now why the first SYN packet is dropped and not the second one, I dont know yet.
06:48:20.337335 IP6 ::1.49374 > ::1.8009: Flags [SEW], seq 3243722104, win 32752, options [mss 16376,sackOK,TS val 26612337 ecr 0,nop,wscale 6], length 0
06:48:21.340112 IP6 ::1.49374 > ::1.8009: Flags [SEW], seq 3243722104, win 32752, options [mss 16376,sackOK,TS val 26613340 ecr 0,nop,wscale 6], length 0
06:48:21.340162 IP6 ::1.8009 > ::1.49374: Flags [S.E], seq 797804014, ack 3243722105, win 32728, options [mss 16376,sackOK,TS val 26613340 ecr 26613340,nop,wscale 6], length 0
06:48:21.340217 IP6 ::1.49374 > ::1.8009: Flags [.], ack 1, win 512, options [nop,nop,TS val 26613340 ecr 26613340], length 0
06:48:21.340360 IP6 ::1.8009 > ::1.49374: Flags [F.], seq 1, ack 1, win 512, options [nop,nop,TS val 26613340 ecr 26613340], length 0
06:48:21.340466 IP6 ::1.49374 > ::1.8009: Flags [F.], seq 1, ack 2, win 512, options [nop,nop,TS val 26613340 ecr 26613340], length 0
06:48:21.340541 IP6 ::1.8009 > ::1.49374: Flags [.], ack 2, win 512, options [nop,nop,TS val 26613340 ecr 26613340], length 0
next prev parent reply other threads:[~2011-11-23 5:58 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
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 [this message]
2011-11-23 6:09 ` Eric Dumazet
2011-11-23 6:13 ` Eric Dumazet
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