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authorEric Dumazet <edumazet@google.com>2012-10-27 23:16:46 +0000
committerDavid S. Miller <davem@davemloft.net>2012-11-03 14:45:00 -0400
commite6c022a4fa2d2d9ca9d0a7ac3b05ad988f39fc30 (patch)
tree6dcd4e2dfc7895f33329fb16653a93f7d52f4bd7 /include/net/request_sock.h
parent25b1e67921f448cdddf70042ba233ffe43d33a9c (diff)
tcp: better retrans tracking for defer-accept
For passive TCP connections using TCP_DEFER_ACCEPT facility, we incorrectly increment req->retrans each time timeout triggers while no SYNACK is sent. SYNACK are not sent for TCP_DEFER_ACCEPT that were established (for which we received the ACK from client). Only the last SYNACK is sent so that we can receive again an ACK from client, to move the req into accept queue. We plan to change this later to avoid the useless retransmit (and potential problem as this SYNACK could be lost) TCP_INFO later gives wrong information to user, claiming imaginary retransmits. Decouple req->retrans field into two independent fields : num_retrans : number of retransmit num_timeout : number of timeouts num_timeout is the counter that is incremented at each timeout, regardless of actual SYNACK being sent or not, and used to compute the exponential timeout. Introduce inet_rtx_syn_ack() helper to increment num_retrans only if ->rtx_syn_ack() succeeded. Use inet_rtx_syn_ack() from tcp_check_req() to increment num_retrans when we re-send a SYNACK in answer to a (retransmitted) SYN. Prior to this patch, we were not counting these retransmits. Change tcp_v[46]_rtx_synack() to increment TCP_MIB_RETRANSSEGS only if a synack packet was successfully queued. Reported-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Julian Anastasov <ja@ssi.bg> Cc: Vijay Subramanian <subramanian.vijay@gmail.com> Cc: Elliott Hughes <enh@google.com> Cc: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/request_sock.h')
-rw-r--r--include/net/request_sock.h12
1 files changed, 8 insertions, 4 deletions
diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index b01d8dd9ee7..a51dbd17c2d 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -49,13 +49,16 @@ struct request_sock_ops {
struct request_sock *req);
};
+extern int inet_rtx_syn_ack(struct sock *parent, struct request_sock *req);
+
/* struct request_sock - mini sock to represent a connection request
*/
struct request_sock {
struct request_sock *dl_next; /* Must be first member! */
u16 mss;
- u8 retrans;
- u8 cookie_ts; /* syncookie: encode tcpopts in timestamp */
+ u8 num_retrans; /* number of retransmits */
+ u8 cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
+ u8 num_timeout:7; /* number of timeouts */
/* The following two fields can be easily recomputed I think -AK */
u32 window_clamp; /* window clamp at creation time */
u32 rcv_wnd; /* rcv_wnd offered first time */
@@ -231,7 +234,7 @@ static inline int reqsk_queue_removed(struct request_sock_queue *queue,
{
struct listen_sock *lopt = queue->listen_opt;
- if (req->retrans == 0)
+ if (req->num_timeout == 0)
--lopt->qlen_young;
return --lopt->qlen;
@@ -269,7 +272,8 @@ static inline void reqsk_queue_hash_req(struct request_sock_queue *queue,
struct listen_sock *lopt = queue->listen_opt;
req->expires = jiffies + timeout;
- req->retrans = 0;
+ req->num_retrans = 0;
+ req->num_timeout = 0;
req->sk = NULL;
req->dl_next = lopt->syn_table[hash];