Implement TCP NewReno, as documented in RFC 2582. This allows
better recovery for multiple packet losses in a single window. The algorithm can be toggled via the sysctl net.inet.tcp.newreno, which defaults to "on". Submitted by: Jayanth Vijayaraghavan <jayanth@yahoo-inc.com>
This commit is contained in:
parent
e003b0836e
commit
46f5848237
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=60067
@ -118,6 +118,8 @@ struct tcphdr {
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#define TCP_MAX_WINSHIFT 14 /* maximum window shift */
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#define TCP_MAXBURST 4 /* maximum segments in a burst */
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#define TCP_MAXHLEN (0xf<<2) /* max length of header in bytes */
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#define TCP_MAXOLEN (TCP_MAXHLEN - sizeof(struct tcphdr))
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/* max space left for options */
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@ -148,6 +148,7 @@ static void tcp_pulloutofband __P((struct socket *,
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static int tcp_reass __P((struct tcpcb *, struct tcphdr *, int *,
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struct mbuf *));
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static void tcp_xmit_timer __P((struct tcpcb *, int));
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static int tcp_newreno __P((struct tcpcb *, struct tcphdr *));
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/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
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#ifdef INET6
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@ -1104,6 +1105,7 @@ tcp_input(m, off0, proto)
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tp->irs = th->th_seq;
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tcp_sendseqinit(tp);
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tcp_rcvseqinit(tp);
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tp->snd_recover = tp->snd_una;
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/*
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* Initialization of the tcpcb for transaction;
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* set SND.WND = SEG.WND,
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@ -1780,10 +1782,20 @@ tcp_input(m, off0, proto)
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u_int win =
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min(tp->snd_wnd, tp->snd_cwnd) / 2 /
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tp->t_maxseg;
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if (tcp_do_newreno && SEQ_LT(th->th_ack,
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tp->snd_recover)) {
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/* False retransmit, should not
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* cut window
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*/
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tp->snd_cwnd += tp->t_maxseg;
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tp->t_dupacks = 0;
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(void) tcp_output(tp);
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goto drop;
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}
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if (win < 2)
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win = 2;
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tp->snd_ssthresh = win * tp->t_maxseg;
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tp->snd_recover = tp->snd_max;
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callout_stop(tp->tt_rexmt);
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tp->t_rtttime = 0;
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tp->snd_nxt = th->th_ack;
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@ -1807,10 +1819,26 @@ tcp_input(m, off0, proto)
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* If the congestion window was inflated to account
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* for the other side's cached packets, retract it.
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*/
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if (tp->t_dupacks >= tcprexmtthresh &&
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tp->snd_cwnd > tp->snd_ssthresh)
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tp->snd_cwnd = tp->snd_ssthresh;
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tp->t_dupacks = 0;
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if (tcp_do_newreno == 0) {
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if (tp->t_dupacks >= tcprexmtthresh &&
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tp->snd_cwnd > tp->snd_ssthresh)
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tp->snd_cwnd = tp->snd_ssthresh;
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tp->t_dupacks = 0;
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} else if (tp->t_dupacks >= tcprexmtthresh &&
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!tcp_newreno(tp, th)) {
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/*
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* Window inflation should have left us with approx.
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* snd_ssthresh outstanding data. But in case we
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* would be inclined to send a burst, better to do
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* it via the slow start mechanism.
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*/
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if (SEQ_GT(th->th_ack + tp->snd_ssthresh, tp->snd_max))
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tp->snd_cwnd =
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tp->snd_max - th->th_ack + tp->t_maxseg;
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else
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tp->snd_cwnd = tp->snd_ssthresh;
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tp->t_dupacks = 0;
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}
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if (SEQ_GT(th->th_ack, tp->snd_max)) {
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tcpstat.tcps_rcvacktoomuch++;
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goto dropafterack;
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@ -1903,7 +1931,8 @@ tcp_input(m, off0, proto)
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if (cw > tp->snd_ssthresh)
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incr = incr * incr / cw;
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tp->snd_cwnd = min(cw + incr, TCP_MAXWIN << tp->snd_scale);
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if (tcp_do_newreno == 0 || SEQ_GEQ(th->th_ack, tp->snd_recover))
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tp->snd_cwnd = min(cw + incr,TCP_MAXWIN<<tp->snd_scale);
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}
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if (acked > so->so_snd.sb_cc) {
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tp->snd_wnd -= so->so_snd.sb_cc;
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@ -2791,3 +2820,41 @@ tcp_mssopt(tp)
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return rt->rt_ifp->if_mtu - min_protoh;
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}
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/*
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* Checks for partial ack. If partial ack arrives, force the retransmission
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* of the next unacknowledged segment, do not clear tp->t_dupacks, and return
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* 1. By setting snd_nxt to ti_ack, this forces retransmission timer to
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* be started again. If the ack advances at least to tp->snd_recover, return 0.
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*/
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static int
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tcp_newreno(tp, th)
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struct tcpcb *tp;
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struct tcphdr *th;
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{
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if (SEQ_LT(th->th_ack, tp->snd_recover)) {
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tcp_seq onxt = tp->snd_nxt;
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tcp_seq ouna = tp->snd_una; /* Haven't updated snd_una yet*/
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u_long ocwnd = tp->snd_cwnd;
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callout_stop(tp->tt_rexmt);
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tp->t_rtttime = 0;
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tp->snd_nxt = th->th_ack;
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tp->snd_cwnd = tp->t_maxseg;
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tp->snd_una = th->th_ack;
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(void) tcp_output(tp);
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tp->snd_cwnd = ocwnd;
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tp->snd_una = ouna;
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if (SEQ_GT(onxt, tp->snd_nxt))
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tp->snd_nxt = onxt;
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/*
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* Partial window deflation. Relies on fact that tp->snd_una
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* not updated yet.
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*/
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tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg);
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return (1);
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}
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return (0);
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}
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@ -98,6 +98,9 @@ int ss_fltsz_local = TCP_MAXWIN; /* something large */
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SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW,
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&ss_fltsz_local, 1, "Slow start flight size for local networks");
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int tcp_do_newreno = 1;
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SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno,
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0, "Enable NewReno Algorithms");
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/*
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* Tcp output routine: figure out what should be sent and send it.
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*/
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@ -118,6 +121,7 @@ tcp_output(tp)
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u_char opt[TCP_MAXOLEN];
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unsigned ipoptlen, optlen, hdrlen;
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int idle, sendalot;
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int maxburst = TCP_MAXBURST;
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struct rmxp_tao *taop;
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struct rmxp_tao tao_noncached;
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#ifdef INET6
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@ -778,12 +782,12 @@ tcp_output(tp)
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*/
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if (!callout_active(tp->tt_rexmt) &&
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tp->snd_nxt != tp->snd_una) {
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callout_reset(tp->tt_rexmt, tp->t_rxtcur,
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tcp_timer_rexmt, tp);
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if (callout_active(tp->tt_persist)) {
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callout_stop(tp->tt_persist);
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tp->t_rxtshift = 0;
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}
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callout_reset(tp->tt_rexmt, tp->t_rxtcur,
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tcp_timer_rexmt, tp);
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}
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} else
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if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
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@ -889,7 +893,7 @@ tcp_output(tp)
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tp->t_flags &= ~TF_ACKNOW;
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if (tcp_delack_enabled)
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callout_stop(tp->tt_delack);
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if (sendalot)
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if (sendalot && (!tcp_do_newreno || --maxburst))
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goto again;
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return (0);
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}
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@ -148,6 +148,7 @@ static void tcp_pulloutofband __P((struct socket *,
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static int tcp_reass __P((struct tcpcb *, struct tcphdr *, int *,
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struct mbuf *));
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static void tcp_xmit_timer __P((struct tcpcb *, int));
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static int tcp_newreno __P((struct tcpcb *, struct tcphdr *));
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/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
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#ifdef INET6
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@ -1104,6 +1105,7 @@ tcp_input(m, off0, proto)
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tp->irs = th->th_seq;
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tcp_sendseqinit(tp);
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tcp_rcvseqinit(tp);
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tp->snd_recover = tp->snd_una;
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/*
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* Initialization of the tcpcb for transaction;
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* set SND.WND = SEG.WND,
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@ -1780,10 +1782,20 @@ tcp_input(m, off0, proto)
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u_int win =
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min(tp->snd_wnd, tp->snd_cwnd) / 2 /
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tp->t_maxseg;
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if (tcp_do_newreno && SEQ_LT(th->th_ack,
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tp->snd_recover)) {
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/* False retransmit, should not
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* cut window
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*/
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tp->snd_cwnd += tp->t_maxseg;
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tp->t_dupacks = 0;
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(void) tcp_output(tp);
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goto drop;
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}
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if (win < 2)
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win = 2;
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tp->snd_ssthresh = win * tp->t_maxseg;
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tp->snd_recover = tp->snd_max;
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callout_stop(tp->tt_rexmt);
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tp->t_rtttime = 0;
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tp->snd_nxt = th->th_ack;
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@ -1807,10 +1819,26 @@ tcp_input(m, off0, proto)
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* If the congestion window was inflated to account
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* for the other side's cached packets, retract it.
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*/
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if (tp->t_dupacks >= tcprexmtthresh &&
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tp->snd_cwnd > tp->snd_ssthresh)
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tp->snd_cwnd = tp->snd_ssthresh;
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tp->t_dupacks = 0;
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if (tcp_do_newreno == 0) {
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if (tp->t_dupacks >= tcprexmtthresh &&
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tp->snd_cwnd > tp->snd_ssthresh)
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tp->snd_cwnd = tp->snd_ssthresh;
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tp->t_dupacks = 0;
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} else if (tp->t_dupacks >= tcprexmtthresh &&
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!tcp_newreno(tp, th)) {
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/*
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* Window inflation should have left us with approx.
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* snd_ssthresh outstanding data. But in case we
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* would be inclined to send a burst, better to do
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* it via the slow start mechanism.
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*/
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if (SEQ_GT(th->th_ack + tp->snd_ssthresh, tp->snd_max))
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tp->snd_cwnd =
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tp->snd_max - th->th_ack + tp->t_maxseg;
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else
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tp->snd_cwnd = tp->snd_ssthresh;
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tp->t_dupacks = 0;
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}
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if (SEQ_GT(th->th_ack, tp->snd_max)) {
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tcpstat.tcps_rcvacktoomuch++;
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goto dropafterack;
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@ -1903,7 +1931,8 @@ tcp_input(m, off0, proto)
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if (cw > tp->snd_ssthresh)
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incr = incr * incr / cw;
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tp->snd_cwnd = min(cw + incr, TCP_MAXWIN << tp->snd_scale);
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if (tcp_do_newreno == 0 || SEQ_GEQ(th->th_ack, tp->snd_recover))
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tp->snd_cwnd = min(cw + incr,TCP_MAXWIN<<tp->snd_scale);
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}
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if (acked > so->so_snd.sb_cc) {
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tp->snd_wnd -= so->so_snd.sb_cc;
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@ -2791,3 +2820,41 @@ tcp_mssopt(tp)
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return rt->rt_ifp->if_mtu - min_protoh;
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}
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/*
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* Checks for partial ack. If partial ack arrives, force the retransmission
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* of the next unacknowledged segment, do not clear tp->t_dupacks, and return
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* 1. By setting snd_nxt to ti_ack, this forces retransmission timer to
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* be started again. If the ack advances at least to tp->snd_recover, return 0.
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*/
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static int
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tcp_newreno(tp, th)
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struct tcpcb *tp;
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struct tcphdr *th;
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{
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if (SEQ_LT(th->th_ack, tp->snd_recover)) {
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tcp_seq onxt = tp->snd_nxt;
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tcp_seq ouna = tp->snd_una; /* Haven't updated snd_una yet*/
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u_long ocwnd = tp->snd_cwnd;
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callout_stop(tp->tt_rexmt);
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tp->t_rtttime = 0;
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tp->snd_nxt = th->th_ack;
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tp->snd_cwnd = tp->t_maxseg;
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tp->snd_una = th->th_ack;
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(void) tcp_output(tp);
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tp->snd_cwnd = ocwnd;
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tp->snd_una = ouna;
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if (SEQ_GT(onxt, tp->snd_nxt))
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tp->snd_nxt = onxt;
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/*
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* Partial window deflation. Relies on fact that tp->snd_una
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* not updated yet.
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*/
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tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg);
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return (1);
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}
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return (0);
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}
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tp->t_srtt = 0;
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}
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tp->snd_nxt = tp->snd_una;
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/*
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* Note: We overload snd_recover to function also as the
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* snd_last variable described in RFC 2582
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*/
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tp->snd_recover = tp->snd_max;
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/*
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* Force a segment to be sent.
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*/
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@ -119,6 +119,8 @@ struct tcpcb {
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* for slow start exponential to
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* linear switch
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*/
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tcp_seq snd_recover; /* for use in fast recovery */
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u_int t_maxopd; /* mss plus options */
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u_long t_rcvtime; /* inactivity time */
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@ -365,6 +367,7 @@ extern struct inpcbinfo tcbinfo;
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extern struct tcpstat tcpstat; /* tcp statistics */
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extern int tcp_mssdflt; /* XXX */
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extern int tcp_delack_enabled;
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extern int tcp_do_newreno;
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extern int ss_fltsz;
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extern int ss_fltsz_local;
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