[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20091217035656.995669356@mini.kroah.org>
Date: Wed, 16 Dec 2009 19:56:45 -0800
From: Greg KH <gregkh@...e.de>
To: linux-kernel@...r.kernel.org, stable@...nel.org
Cc: stable-review@...nel.org, torvalds@...ux-foundation.org,
akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
Damian Lukowski <damian@....rwth-aachen.de>,
Ilpo JÀrvinen <ilpo.jarvinen@...sinki.fi>,
"David S. Miller" <davem@...emloft.net>
Subject: [108/151] tcp: Stalling connections: Fix timeout calculation routine
2.6.32-stable review patch. If anyone has any objections, please let us know.
------------------
From: Damian Lukowski <damian@....rwth-aachen.de>
[ Upstream commit 07f29bc5bbae4e53e982ab956fed7207990a7786 ]
This patch fixes a problem in the TCP connection timeout calculation.
Currently, timeout decisions are made on the basis of the current
tcp_time_stamp and retrans_stamp, which is usually set at the first
retransmission.
However, if the retransmission fails in tcp_retransmit_skb(),
retrans_stamp is not updated and remains zero. This leads to wrong
decisions in retransmits_timed_out() if tcp_time_stamp is larger than
the specified timeout, which is very likely.
In this case, the TCP connection dies after the first attempted
(and unsuccessful) retransmission.
With this patch, tcp_skb_cb->when is used instead, when retrans_stamp
is not available.
This bug has been introduced together with retransmits_timed_out() in
2.6.32, as the number of retransmissions has been used for timeout
decisions before. The corresponding commit was
6fa12c85031485dff38ce550c24f10da23b0adaa (Revert Backoff [v3]:
Calculate TCP's connection close threshold as a time value.).
Thanks to Ilpo Järvinen for code suggestions and Frederic Leroy for
testing.
Reported-by: Frederic Leroy <fredo@...rox.org>
Signed-off-by: Damian Lukowski <damian@....rwth-aachen.de>
Acked-by: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
include/net/tcp.h | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1263,14 +1263,20 @@ static inline struct sk_buff *tcp_write_
* TCP connection after "boundary" unsucessful, exponentially backed-off
* retransmissions with an initial RTO of TCP_RTO_MIN.
*/
-static inline bool retransmits_timed_out(const struct sock *sk,
+static inline bool retransmits_timed_out(struct sock *sk,
unsigned int boundary)
{
unsigned int timeout, linear_backoff_thresh;
+ unsigned int start_ts;
if (!inet_csk(sk)->icsk_retransmits)
return false;
+ if (unlikely(!tcp_sk(sk)->retrans_stamp))
+ start_ts = TCP_SKB_CB(tcp_write_queue_head(sk))->when;
+ else
+ start_ts = tcp_sk(sk)->retrans_stamp;
+
linear_backoff_thresh = ilog2(TCP_RTO_MAX/TCP_RTO_MIN);
if (boundary <= linear_backoff_thresh)
@@ -1279,7 +1285,7 @@ static inline bool retransmits_timed_out
timeout = ((2 << linear_backoff_thresh) - 1) * TCP_RTO_MIN +
(boundary - linear_backoff_thresh) * TCP_RTO_MAX;
- return (tcp_time_stamp - tcp_sk(sk)->retrans_stamp) >= timeout;
+ return (tcp_time_stamp - start_ts) >= timeout;
}
static inline struct sk_buff *tcp_send_head(struct sock *sk)
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists