From: Alex Bergmann <alex@linlab.net>
To: davem@davemloft.net
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 1/1] tcp: Wrong timeout for SYN segments
Date: Wed, 22 Aug 2012 01:29:23 +0200 [thread overview]
Message-ID: <503419D3.1080700@linlab.net> (raw)
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
next reply other threads:[~2012-08-21 23:59 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-21 23:29 Alex Bergmann [this message]
2012-08-22 8:06 ` [PATCH 1/1] tcp: Wrong timeout for SYN segments 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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=503419D3.1080700@linlab.net \
--to=alex@linlab.net \
--cc=davem@davemloft.net \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).