On 08/22/2012 06:41 PM, H.K. Jerry Chu wrote:
On Tue, Aug 21, 2012 at 4:29 PM, Alex Bergmann <a...@linlab.net
<mailto:a...@linlab.net>> wrote:
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 <a...@linlab.net <mailto:a...@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.
This issue occurred to me right after I submitted the patch for RFC6298.
I did not commit any more change because RFC compliance aside, 180secs
just seem like eternity in the Internet age.
(See my past post on this at
http://marc.info/?l=linux-netdev&m=130759078118866&w=2)
Okay, I missed that post during my search about the current situation.
Thanks,
Alex
Jerry
Signed-off-by: Alexander Bergmann <a...@linlab.net
<mailto:a...@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
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majord...@vger.kernel.org
<mailto:majord...@vger.kernel.org>
More majordomo info at http://vger.kernel.org/majordomo-info.html
--
|. _ | _ |_ _ _ _|_
||| ||(_||_).| |(/_ |
email/sip/xmpp: a...@linlab.net
phone/enum: +49 2871 2355378
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
