Author: rscheff Date: Wed Apr 29 21:48:52 2020 New Revision: 360477 URL: https://svnweb.freebsd.org/changeset/base/360477
Log: 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) Approved by: tuexen (mentor), rgrimes (mentor) MFC after: 3 weeks Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D19000 Modified: head/sys/netinet/tcp_input.c head/sys/netinet/tcp_stacks/bbr.c head/sys/netinet/tcp_stacks/rack.c Modified: head/sys/netinet/tcp_input.c ============================================================================== --- head/sys/netinet/tcp_input.c Wed Apr 29 21:12:32 2020 (r360476) +++ head/sys/netinet/tcp_input.c Wed Apr 29 21:48:52 2020 (r360477) @@ -1470,7 +1470,7 @@ 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; @@ -2374,12 +2374,6 @@ 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); @@ -2400,6 +2394,13 @@ 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. */ @@ -2693,6 +2694,15 @@ 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: head/sys/netinet/tcp_stacks/bbr.c ============================================================================== --- head/sys/netinet/tcp_stacks/bbr.c Wed Apr 29 21:12:32 2020 (r360476) +++ head/sys/netinet/tcp_stacks/bbr.c Wed Apr 29 21:48:52 2020 (r360477) @@ -9326,11 +9326,6 @@ bbr_do_syn_recv(struct mbuf *m, struct tcphdr *th, str 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++; } /* * Make transitions: SYN-RECEIVED -> ESTABLISHED SYN-RECEIVED* -> @@ -9353,6 +9348,13 @@ bbr_do_syn_recv(struct mbuf *m, struct tcphdr *th, str 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. Modified: head/sys/netinet/tcp_stacks/rack.c ============================================================================== --- head/sys/netinet/tcp_stacks/rack.c Wed Apr 29 21:12:32 2020 (r360476) +++ head/sys/netinet/tcp_stacks/rack.c Wed Apr 29 21:48:52 2020 (r360477) @@ -6540,12 +6540,6 @@ 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); @@ -6563,6 +6557,13 @@ 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"
