From e6c022a4fa2d2d9ca9d0a7ac3b05ad988f39fc30 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 27 Oct 2012 23:16:46 +0000 Subject: 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 Signed-off-by: Eric Dumazet Cc: Julian Anastasov Cc: Vijay Subramanian Cc: Elliott Hughes Cc: Neal Cardwell Signed-off-by: David S. Miller --- net/ipv4/inet_connection_sock.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) (limited to 'net/ipv4/inet_connection_sock.c') diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c index d34ce2972c8f..2026542d6836 100644 --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -521,21 +521,31 @@ static inline void syn_ack_recalc(struct request_sock *req, const int thresh, int *expire, int *resend) { if (!rskq_defer_accept) { - *expire = req->retrans >= thresh; + *expire = req->num_timeout >= thresh; *resend = 1; return; } - *expire = req->retrans >= thresh && - (!inet_rsk(req)->acked || req->retrans >= max_retries); + *expire = req->num_timeout >= thresh && + (!inet_rsk(req)->acked || req->num_timeout >= max_retries); /* * Do not resend while waiting for data after ACK, * start to resend on end of deferring period to give * last chance for data or ACK to create established socket. */ *resend = !inet_rsk(req)->acked || - req->retrans >= rskq_defer_accept - 1; + req->num_timeout >= rskq_defer_accept - 1; } +int inet_rtx_syn_ack(struct sock *parent, struct request_sock *req) +{ + int err = req->rsk_ops->rtx_syn_ack(parent, req, NULL); + + if (!err) + req->num_retrans++; + return err; +} +EXPORT_SYMBOL(inet_rtx_syn_ack); + void inet_csk_reqsk_queue_prune(struct sock *parent, const unsigned long interval, const unsigned long timeout, @@ -599,13 +609,14 @@ void inet_csk_reqsk_queue_prune(struct sock *parent, req->rsk_ops->syn_ack_timeout(parent, req); if (!expire && (!resend || - !req->rsk_ops->rtx_syn_ack(parent, req, NULL) || + !inet_rtx_syn_ack(parent, req) || inet_rsk(req)->acked)) { unsigned long timeo; - if (req->retrans++ == 0) + if (req->num_timeout++ == 0) lopt->qlen_young--; - timeo = min((timeout << req->retrans), max_rto); + timeo = min(timeout << req->num_timeout, + max_rto); req->expires = now + timeo; reqp = &req->dl_next; continue; -- cgit v1.2.3-58-ga151