Author: tuexen
Date: Wed Sep 12 10:27:58 2018
New Revision: 338614
URL: https://svnweb.freebsd.org/changeset/base/338614
Log:
Fix TCP Fast Open for the TCP RACK stack.
* Fix a bug where the SYN handling during established state was
applied to a front state.
* Move a check for retransmission after the timer handling.
This was suppressing timer based retransmissions.
* Fix an off-by one byte in the sequence number of retransmissions.
* Apply fixes corresponding to
https://svnweb.freebsd.org/changeset/base/336934
Reviewed by: rrs@
Approved by: re (kib@)
MFC after: 1 month
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D16912
Modified:
head/sys/netinet/tcp_stacks/rack.c
Modified: head/sys/netinet/tcp_stacks/rack.c
==============================================================================
--- head/sys/netinet/tcp_stacks/rack.c Wed Sep 12 10:09:59 2018
(r338613)
+++ head/sys/netinet/tcp_stacks/rack.c Wed Sep 12 10:27:58 2018
(r338614)
@@ -5401,14 +5401,6 @@ rack_do_syn_recv(struct mbuf *m, struct tcphdr *th, st
if (thflags & TH_RST)
return (rack_process_rst(m, th, so, tp));
/*
- * RFC5961 Section 4.2 Send challenge ACK for any SYN in
- * synchronized state.
- */
- if (thflags & TH_SYN) {
- rack_challenge_ack(m, th, tp, &ret_val);
- return (ret_val);
- }
- /*
* RFC 1323 PAWS: If we have a timestamp reply on this segment and
* it's less than ts_recent, drop it.
*/
@@ -5478,6 +5470,16 @@ rack_do_syn_recv(struct mbuf *m, struct tcphdr *th, st
* FIN-WAIT-1
*/
tp->t_starttime = ticks;
+ if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) {
+ tcp_fastopen_decrement_counter(tp->t_tfo_pending);
+ tp->t_tfo_pending = NULL;
+
+ /*
+ * Account for the ACK of our SYN prior to
+ * regular ACK processing below.
+ */
+ tp->snd_una++;
+ }
if (tp->t_flags & TF_NEEDFIN) {
tcp_state_change(tp, TCPS_FIN_WAIT_1);
tp->t_flags &= ~TF_NEEDFIN;
@@ -5485,16 +5487,6 @@ rack_do_syn_recv(struct mbuf *m, struct tcphdr *th, st
tcp_state_change(tp, TCPS_ESTABLISHED);
TCP_PROBE5(accept__established, NULL, tp,
mtod(m, const char *), tp, th);
- if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) {
- tcp_fastopen_decrement_counter(tp->t_tfo_pending);
- tp->t_tfo_pending = NULL;
-
- /*
- * Account for the ACK of our SYN prior to regular
- * ACK processing below.
- */
- tp->snd_una++;
- }
/*
* TFO connections call cc_conn_init() during SYN
* processing. Calling it again here for such connections
@@ -6924,16 +6916,6 @@ rack_output(struct tcpcb *tp)
if (tp->t_flags & TF_TOE)
return (tcp_offload_output(tp));
#endif
-
- /*
- * For TFO connections in SYN_RECEIVED, only allow the initial
- * SYN|ACK and those sent by the retransmit timer.
- */
- if (IS_FASTOPEN(tp->t_flags) &&
- (tp->t_state == TCPS_SYN_RECEIVED) &&
- SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN|ACK sent */
- (rack->r_ctl.rc_resend == NULL)) /* not a retransmit */
- return (0);
#ifdef INET6
if (rack->r_state) {
/* Use the cache line loaded if possible */
@@ -6976,6 +6958,17 @@ rack_output(struct tcpcb *tp)
rack->r_wanted_output = 0;
rack->r_timer_override = 0;
/*
+ * For TFO connections in SYN_SENT or SYN_RECEIVED,
+ * only allow the initial SYN or SYN|ACK and those sent
+ * by the retransmit timer.
+ */
+ if (IS_FASTOPEN(tp->t_flags) &&
+ ((tp->t_state == TCPS_SYN_RECEIVED) ||
+ (tp->t_state == TCPS_SYN_SENT)) &&
+ SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent
*/
+ (tp->t_rxtshift == 0)) /* not a retransmit */
+ return (0);
+ /*
* Determine length of data that should be transmitted, and flags
* that will be used. If there is some data or critical controls
* (SYN, RST) to send, then transmit; otherwise, investigate
@@ -7353,8 +7346,10 @@ again:
(((flags & TH_SYN) && (tp->t_rxtshift > 0)) ||
((tp->t_state == TCPS_SYN_SENT) &&
(tp->t_tfo_client_cookie_len == 0)) ||
- (flags & TH_RST)))
+ (flags & TH_RST))) {
+ sack_rxmit = 0;
len = 0;
+ }
/* Without fast-open there should never be data sent on a SYN */
if ((flags & TH_SYN) && (!IS_FASTOPEN(tp->t_flags)))
len = 0;
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