linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
* [PATCH 1/1] tcp: Wrong timeout for SYN segments
@ 2012-08-21 23:29 Alex Bergmann
  2012-08-22  8:06 ` Eric Dumazet
                   ` (2 more replies)
  0 siblings, 3 replies; 31+ messages in thread
From: Alex Bergmann @ 2012-08-21 23:29 UTC (permalink / raw)
  To: davem; +Cc: netdev, linux-kernel

Hi David,

I'm not 100% sure, but it looks like I found an RFC mismatch with the 
current default values of the TCP implementation.

Alex

>From 8b854a525eb45f64ad29dfab16f9d9f681e84495 Mon Sep 17 00:00:00 2001
From: Alexander Bergmann <alex@linlab.net>
Date: Wed, 22 Aug 2012 00:29:08 +0200
Subject: [PATCH 1/1] tcp: Wrong timeout for SYN segments

Commit 9ad7c049 changed the initRTO from 3secs to 1sec in accordance to
RFC6298 (former RFC2988bis). This introduced a gap with RFC1122 that
defines a minimum retransmission window for SYN segments of at least
180secs.

Prior to 9ad7c049 the timeout was defined with 189secs. Now we have only
a timeout of 63secs.

        ((2 << 5) - 1) * 3 secs = 189 secs
        ((2 << 5) - 1) * 1 secs = 63 secs

To fulfill the MUST constraint in RFC1122 section 4.2.3.5 about R2 for
SYN segments, the values of TCP_SYN_RETRIES and TCP_SYNACK_RETRIES must
be changed to 7 reties.

        ((2 << 7) - 1) * 1 secs = 255 secs

This would result in an ETIMEDOUT of 4 minutes 15 seconds.

Signed-off-by: Alexander Bergmann <alex@linlab.net>
---
 include/net/tcp.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 1f000ff..7eaae19 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -98,10 +98,10 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo);
                                 * 15 is ~13-30min depending on RTO.
                                 */
 
-#define TCP_SYN_RETRIES         5      /* number of times to retry active opening a
+#define TCP_SYN_RETRIES         7      /* number of times to retry active opening a
                                 * connection: ~180sec is RFC minimum   */
 
-#define TCP_SYNACK_RETRIES 5   /* number of times to retry passive opening a
+#define TCP_SYNACK_RETRIES 7   /* number of times to retry passive opening a
                                 * connection: ~180sec is RFC minimum   */
 
 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
-- 
1.7.8.6


^ permalink raw reply related	[flat|nested] 31+ messages in thread

end of thread, other threads:[~2012-08-31 19:47 UTC | newest]

Thread overview: 31+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2012-08-21 23:29 [PATCH 1/1] tcp: Wrong timeout for SYN segments Alex Bergmann
2012-08-22  8:06 ` Eric Dumazet
2012-08-22  8:48   ` Alex Bergmann
2012-08-22  8:58     ` Eric Dumazet
2012-08-22  9:29       ` Alex Bergmann
2012-08-22  9:59         ` Eric Dumazet
2012-08-22 10:03           ` Eric Dumazet
2012-08-22 17:29             ` H.K. Jerry Chu
2012-08-22 16:44 ` H.K. Jerry Chu
     [not found] ` <CAFbMe2M7ekc94bQk7vTS1LhScPd49VZ-zKOCUXhqwxXtL-nkuA@mail.gmail.com>
2012-08-23 11:58   ` Alex Bergmann
2012-08-23 12:15     ` Eric Dumazet
2012-08-23 12:35       ` David Laight
2012-08-23 12:51         ` Eric Dumazet
2012-08-23 12:37       ` Alex Bergmann
2012-08-23 12:49         ` Eric Dumazet
2012-08-24 12:17           ` Alex Bergmann
2012-08-24 17:42           ` David Miller
2012-08-25  8:48             ` Alexander Bergmann
2012-08-25  9:01               ` Eric Dumazet
2012-08-28  8:44               ` Carsten Wolff
     [not found]                 ` <1346414260.2591.8.camel@edumazet-glaptop>
2012-08-31 12:48                   ` Alexander Bergmann
2012-08-31 13:25                     ` Eric Dumazet
2012-08-31 19:42                       ` David Miller
2012-08-31 19:47                         ` David Miller
2012-08-29  4:34               ` H.K. Jerry Chu
2012-08-29  8:51                 ` Eric Dumazet
2012-08-29 17:25                   ` H.K. Jerry Chu
2012-08-30 13:12                     ` Eric Dumazet
2012-08-30 16:45                       ` David Miller
2012-08-30 18:04                         ` H.K. Jerry Chu
2012-08-30 17:59                       ` H.K. Jerry Chu

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).