Author: rscheff Date: Thu May 21 19:46:11 2020 New Revision: 361342 URL: https://svnweb.freebsd.org/changeset/base/361342
Log: MFC r360477: Correctly set up the initial TCP congestion window in all cases by not including the SYN bit sequence space in cwnd related calculations. Snd_und is adjusted explicitly in all cases, outside the cwnd update, instead. This fixes an off-by-one conformance issue with regular TCP sessions not using Appropriate Byte Counting (RFC3465), sending one more packet during the initial window than expected. PR: 235256 Reviewed by: tuexen (mentor), rgrimes (mentor, blanket) Approved by: tuexen (mentor), rgrimes (mentor, blanket) MFC after: 3 weeks Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D19000 Modified: stable/12/sys/netinet/tcp_input.c stable/12/sys/netinet/tcp_stacks/rack.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/netinet/tcp_input.c ============================================================================== --- stable/12/sys/netinet/tcp_input.c Thu May 21 19:45:14 2020 (r361341) +++ stable/12/sys/netinet/tcp_input.c Thu May 21 19:46:11 2020 (r361342) @@ -1519,7 +1519,7 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, stru struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos) { int thflags, acked, ourfinisacked, needoutput = 0, sack_changed; - int rstreason, todrop, win; + int rstreason, todrop, win, incforsyn = 0; uint32_t tiwin; uint16_t nsegs; char *s; @@ -2432,12 +2432,6 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, stru 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); @@ -2458,6 +2452,13 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, stru tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); } /* + * Account for the ACK of our SYN prior to + * regular ACK processing below, except for + * simultaneous SYN, which is handled later. + */ + if (SEQ_GT(th->th_ack, tp->snd_una) && !(tp->t_flags & TF_NEEDSYN)) + incforsyn = 1; + /* * If segment contains data or ACK, will call tcp_reass() * later; if not, do so now to pass queued data to user. */ @@ -2751,6 +2752,15 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, stru process_ACK: INP_WLOCK_ASSERT(tp->t_inpcb); + /* + * Adjust for the SYN bit in sequence space, + * but don't account for it in cwnd calculations. + * This is for the SYN_RECEIVED, non-simultaneous + * SYN case. SYN_SENT and simultaneous SYN are + * treated elsewhere. + */ + if (incforsyn) + tp->snd_una++; acked = BYTES_THIS_ACK(tp, th); KASSERT(acked >= 0, ("%s: acked unexepectedly negative " "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__, Modified: stable/12/sys/netinet/tcp_stacks/rack.c ============================================================================== --- stable/12/sys/netinet/tcp_stacks/rack.c Thu May 21 19:45:14 2020 (r361341) +++ stable/12/sys/netinet/tcp_stacks/rack.c Thu May 21 19:46:11 2020 (r361342) @@ -5580,12 +5580,6 @@ rack_do_syn_recv(struct mbuf *m, struct tcphdr *th, st 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); @@ -5603,6 +5597,13 @@ rack_do_syn_recv(struct mbuf *m, struct tcphdr *th, st if (!IS_FASTOPEN(tp->t_flags)) cc_conn_init(tp); } + /* + * Account for the ACK of our SYN prior to + * regular ACK processing below, except for + * simultaneous SYN, which is handled later. + */ + if (SEQ_GT(th->th_ack, tp->snd_una) && !(tp->t_flags & TF_NEEDSYN)) + tp->snd_una++; /* * If segment contains data or ACK, will call tcp_reass() later; if * not, do so now to pass queued data to user. _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
