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Fix TCP Fast Open for the TCP RACK stack.

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* 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
This commit is contained in:
Michael Tuexen 2018-09-12 10:27:58 +00:00
parent e6895e8049
commit a8a8a8a808
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=338614
1 changed files with 24 additions and 29 deletions
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53
sys/netinet/tcp_stacks/rack.c
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@ -5400,14 +5400,6 @@ rack_do_syn_recv(struct mbuf *m, struct tcphdr *th, struct socket *so,
}
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, struct socket *so,
* 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, struct socket *so,
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 */
@ -6975,6 +6957,17 @@ 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
@ -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;