From 8e4ad3b84abff0a3107ea94e9d5f21897f68ae55 Mon Sep 17 00:00:00 2001 From: tuexen Date: Fri, 25 Jan 2019 13:57:09 +0000 Subject: [PATCH] Fix a bug in the restart window computation of TCP New Reno When implementing support for IW10, an update in the computation of the restart window used after an idle phase was missed. To minimize code duplication, implement the logic in tcp_compute_initwnd() and call it. This fixes a bug in NewReno, which was not aware of IW10. Submitted by: Richard Scheffenegger Reviewed by: tuexen@ MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D18940 --- sys/netinet/cc/cc_newreno.c | 8 ++---- sys/netinet/tcp_input.c | 48 +++++++++++++++++++++-------------- sys/netinet/tcp_stacks/rack.c | 18 +++---------- sys/netinet/tcp_var.h | 1 + 4 files changed, 35 insertions(+), 40 deletions(-) diff --git a/sys/netinet/cc/cc_newreno.c b/sys/netinet/cc/cc_newreno.c index 988cdb087f3b..50c0b79660e2 100644 --- a/sys/netinet/cc/cc_newreno.c +++ b/sys/netinet/cc/cc_newreno.c @@ -199,7 +199,7 @@ newreno_ack_received(struct cc_var *ccv, uint16_t type) static void newreno_after_idle(struct cc_var *ccv) { - int rw; + uint32_t rw; /* * If we've been idle for more than one retransmit timeout the old @@ -214,11 +214,7 @@ newreno_after_idle(struct cc_var *ccv) * * See RFC5681 Section 4.1. "Restarting Idle Connections". */ - if (V_tcp_do_rfc3390) - rw = min(4 * CCV(ccv, t_maxseg), - max(2 * CCV(ccv, t_maxseg), 4380)); - else - rw = CCV(ccv, t_maxseg) * 2; + rw = tcp_compute_initwnd(tcp_maxseg(ccv->ccvc.tcp)); CCV(ccv, snd_cwnd) = min(rw, CCV(ccv, snd_cwnd)); } diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c index c4a4746d4218..750046407fbd 100644 --- a/sys/netinet/tcp_input.c +++ b/sys/netinet/tcp_input.c @@ -371,31 +371,14 @@ cc_conn_init(struct tcpcb *tp) /* * Set the initial slow-start flight size. * - * RFC5681 Section 3.1 specifies the default conservative values. - * RFC3390 specifies slightly more aggressive values. - * RFC6928 increases it to ten segments. - * Support for user specified value for initial flight size. - * * If a SYN or SYN/ACK was lost and retransmitted, we have to * reduce the initial CWND to one segment as congestion is likely * requiring us to be cautious. */ if (tp->snd_cwnd == 1) tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */ - else if (V_tcp_initcwnd_segments) - tp->snd_cwnd = min(V_tcp_initcwnd_segments * maxseg, - max(2 * maxseg, V_tcp_initcwnd_segments * 1460)); - else if (V_tcp_do_rfc3390) - tp->snd_cwnd = min(4 * maxseg, max(2 * maxseg, 4380)); - else { - /* Per RFC5681 Section 3.1 */ - if (maxseg > 2190) - tp->snd_cwnd = 2 * maxseg; - else if (maxseg > 1095) - tp->snd_cwnd = 3 * maxseg; - else - tp->snd_cwnd = 4 * maxseg; - } + else + tp->snd_cwnd = tcp_compute_initwnd(maxseg); if (CC_ALGO(tp)->conn_init != NULL) CC_ALGO(tp)->conn_init(tp->ccv); @@ -3818,3 +3801,30 @@ tcp_compute_pipe(struct tcpcb *tp) tp->sackhint.sack_bytes_rexmit - tp->sackhint.sacked_bytes); } + +uint32_t +tcp_compute_initwnd(uint32_t maxseg) +{ + /* + * Calculate the Initial Window, also used as Restart Window + * + * RFC5681 Section 3.1 specifies the default conservative values. + * RFC3390 specifies slightly more aggressive values. + * RFC6928 increases it to ten segments. + * Support for user specified value for initial flight size. + */ + if (V_tcp_initcwnd_segments) + return min(V_tcp_initcwnd_segments * maxseg, + max(2 * maxseg, V_tcp_initcwnd_segments * 1460)); + else if (V_tcp_do_rfc3390) + return min(4 * maxseg, max(2 * maxseg, 4380)); + else { + /* Per RFC5681 Section 3.1 */ + if (maxseg > 2190) + return (2 * maxseg); + else if (maxseg > 1095) + return (3 * maxseg); + else + return (4 * maxseg); + } +} diff --git a/sys/netinet/tcp_stacks/rack.c b/sys/netinet/tcp_stacks/rack.c index d2db801b1f85..8201dc514bf0 100644 --- a/sys/netinet/tcp_stacks/rack.c +++ b/sys/netinet/tcp_stacks/rack.c @@ -1425,21 +1425,9 @@ rack_cc_after_idle(struct tcpcb *tp, int reduce_largest) if (tp->snd_cwnd == 1) i_cwnd = tp->t_maxseg; /* SYN(-ACK) lost */ - else if (V_tcp_initcwnd_segments) - i_cwnd = min((V_tcp_initcwnd_segments * tp->t_maxseg), - max(2 * tp->t_maxseg, V_tcp_initcwnd_segments * 1460)); - else if (V_tcp_do_rfc3390) - i_cwnd = min(4 * tp->t_maxseg, - max(2 * tp->t_maxseg, 4380)); - else { - /* Per RFC5681 Section 3.1 */ - if (tp->t_maxseg > 2190) - i_cwnd = 2 * tp->t_maxseg; - else if (tp->t_maxseg > 1095) - i_cwnd = 3 * tp->t_maxseg; - else - i_cwnd = 4 * tp->t_maxseg; - } + else + i_cwnd = tcp_compute_initwnd(tcp_maxseg(tp)); + if (reduce_largest) { /* * Do we reduce the largest cwnd to make diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h index 2fbe07ade5dc..09316343cb2a 100644 --- a/sys/netinet/tcp_var.h +++ b/sys/netinet/tcp_var.h @@ -942,6 +942,7 @@ void tcp_sack_partialack(struct tcpcb *, struct tcphdr *); void tcp_free_sackholes(struct tcpcb *tp); int tcp_newreno(struct tcpcb *, struct tcphdr *); int tcp_compute_pipe(struct tcpcb *); +uint32_t tcp_compute_initwnd(uint32_t); void tcp_sndbuf_autoscale(struct tcpcb *, struct socket *, uint32_t); struct mbuf * tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen,