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authorDamian Lukowski <damian@tvk.rwth-aachen.de>2009-12-07 06:06:15 +0000
committerDavid S. Miller <davem@davemloft.net>2009-12-08 20:56:11 -0800
commit07f29bc5bbae4e53e982ab956fed7207990a7786 (patch)
treeb44506c37ce4886220439b38ef647c3cd7fbc6ce /include
parentcb19054697e92a793f336380fd72c588521178ff (diff)
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tcp: Stalling connections: Fix timeout calculation routine
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@starox.org> Signed-off-by: Damian Lukowski <damian@tvk.rwth-aachen.de> Acked-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
-rw-r--r--include/net/tcp.h10
1 files changed, 8 insertions, 2 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h
index e2d2ca2509b..e54bd85d9d4 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1265,14 +1265,20 @@ static inline struct sk_buff *tcp_write_queue_prev(struct sock *sk, struct sk_bu
* 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)
@@ -1281,7 +1287,7 @@ static inline bool retransmits_timed_out(const struct sock *sk,
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)