--- /dev/null
+/*
+ * Copyright (c) 2010 Apple Inc. All rights reserved.
+ *
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. The rights granted to you under the License
+ * may not be used to create, or enable the creation or redistribution of,
+ * unlawful or unlicensed copies of an Apple operating system, or to
+ * circumvent, violate, or enable the circumvention or violation of, any
+ * terms of an Apple operating system software license agreement.
+ *
+ * Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
+ */
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/protosw.h>
+
+#include <net/route.h>
+#include <netinet/in.h>
+#include <netinet/in_systm.h>
+#include <netinet/ip.h>
+
+#if INET6
+#include <netinet/ip6.h>
+#endif
+#include <netinet/ip_var.h>
+#include <netinet/tcp.h>
+#include <netinet/tcp_fsm.h>
+#include <netinet/tcp_timer.h>
+#include <netinet/tcp_var.h>
+#include <netinet/tcpip.h>
+#include <netinet/tcp_cc.h>
+#include <libkern/OSAtomic.h>
+
+int tcp_newreno_init(struct tcpcb *tp);
+int tcp_newreno_cleanup(struct tcpcb *tp);
+void tcp_newreno_cwnd_init_or_reset(struct tcpcb *tp);
+void tcp_newreno_inseq_ack_rcvd(struct tcpcb *tp, struct tcphdr *th);
+void tcp_newreno_ack_rcvd(struct tcpcb *tp, struct tcphdr *th);
+void tcp_newreno_pre_fr(struct tcpcb *tp, struct tcphdr *th);
+void tcp_newreno_post_fr(struct tcpcb *tp, struct tcphdr *th);
+void tcp_newreno_after_idle(struct tcpcb *tp);
+void tcp_newreno_after_timeout(struct tcpcb *tp);
+int tcp_newreno_delay_ack(struct tcpcb *tp, struct tcphdr *th);
+void tcp_newreno_switch_cc(struct tcpcb *tp, uint16_t old_index);
+
+struct tcp_cc_algo tcp_cc_newreno = {
+ .name = "newreno",
+ .init = tcp_newreno_init,
+ .cleanup = tcp_newreno_cleanup,
+ .cwnd_init = tcp_newreno_cwnd_init_or_reset,
+ .inseq_ack_rcvd = tcp_newreno_inseq_ack_rcvd,
+ .ack_rcvd = tcp_newreno_ack_rcvd,
+ .pre_fr = tcp_newreno_pre_fr,
+ .post_fr = tcp_newreno_post_fr,
+ .after_idle = tcp_newreno_cwnd_init_or_reset,
+ .after_timeout = tcp_newreno_after_timeout,
+ .delay_ack = tcp_newreno_delay_ack,
+ .switch_to = tcp_newreno_switch_cc
+};
+
+extern int tcp_do_rfc3465;
+extern int tcp_do_rfc3465_lim2;
+extern int maxseg_unacked;
+
+int tcp_newreno_init(struct tcpcb *tp) {
+#pragma unused(tp)
+ OSIncrementAtomic((volatile SInt32 *)&tcp_cc_newreno.num_sockets);
+ return 0;
+}
+
+int tcp_newreno_cleanup(struct tcpcb *tp) {
+#pragma unused(tp)
+ OSDecrementAtomic((volatile SInt32 *)&tcp_cc_newreno.num_sockets);
+ return 0;
+}
+
+/* Initialize the congestion window for a connection or
+ * handles connections that have been idle for
+ * some time. In this state, no acks are
+ * expected to clock out any data we send --
+ * slow start to get ack "clock" running again.
+ *
+ * Set the slow-start flight size depending on whether
+ * this is a local network or not.
+ */
+void
+tcp_newreno_cwnd_init_or_reset(struct tcpcb *tp) {
+ if ( tp->t_flags & TF_LOCAL )
+ tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local;
+ else {
+ /* Calculate initial cwnd according to RFC3390,
+ * - On a standard link, this will result in a higher cwnd
+ * and improve initial transfer rate.
+ * - Keep the old ss_fltsz sysctl for ABI compabitility issues.
+ * but it will be overriden if tcp_do_rfc3390 sysctl is set.
+ */
+
+ if (tcp_do_rfc3390)
+ tp->snd_cwnd = min(4 * tp->t_maxseg, max(2 * tp->t_maxseg, 4380));
+
+ else
+ tp->snd_cwnd = tp->t_maxseg * ss_fltsz;
+ }
+}
+
+
+/* Function to handle an in-sequence ack during congestion avoidance phase.
+ * This will get called from header prediction code.
+ */
+void
+tcp_newreno_inseq_ack_rcvd(struct tcpcb *tp, struct tcphdr *th) {
+ int acked = 0;
+ acked = th->th_ack - tp->snd_una;
+ /*
+ * Grow the congestion window, if the
+ * connection is cwnd bound.
+ */
+ if (tp->snd_cwnd < tp->snd_wnd) {
+ tp->t_bytes_acked += acked;
+ if (tp->t_bytes_acked > tp->snd_cwnd) {
+ tp->t_bytes_acked -= tp->snd_cwnd;
+ tp->snd_cwnd += tp->t_maxseg;
+ }
+ }
+}
+/* Function to process an ack.
+ */
+void
+tcp_newreno_ack_rcvd(struct tcpcb *tp, struct tcphdr *th) {
+ /*
+ * RFC 3465 - Appropriate Byte Counting.
+ *
+ * If the window is currently less than ssthresh,
+ * open the window by the number of bytes ACKed by
+ * the last ACK, however clamp the window increase
+ * to an upper limit "L".
+ *
+ * In congestion avoidance phase, open the window by
+ * one segment each time "bytes_acked" grows to be
+ * greater than or equal to the congestion window.
+ */
+
+ register u_int cw = tp->snd_cwnd;
+ register u_int incr = tp->t_maxseg;
+ int acked = 0;
+
+ acked = th->th_ack - tp->snd_una;
+ if (tcp_do_rfc3465) {
+
+ if (cw >= tp->snd_ssthresh) {
+ tp->t_bytes_acked += acked;
+ if (tp->t_bytes_acked >= cw) {
+ /* Time to increase the window. */
+ tp->t_bytes_acked -= cw;
+ } else {
+ /* No need to increase yet. */
+ incr = 0;
+ }
+ } else {
+ /*
+ * If the user explicitly enables RFC3465
+ * use 2*SMSS for the "L" param. Otherwise
+ * use the more conservative 1*SMSS.
+ *
+ * (See RFC 3465 2.3 Choosing the Limit)
+ */
+ u_int abc_lim;
+
+ abc_lim = (tcp_do_rfc3465_lim2 &&
+ tp->snd_nxt == tp->snd_max) ? incr * 2 : incr;
+
+ incr = lmin(acked, abc_lim);
+ }
+ } else {
+ /*
+ * If the window gives us less than ssthresh packets
+ * in flight, open exponentially (segsz per packet).
+ * Otherwise open linearly: segsz per window
+ * (segsz^2 / cwnd per packet).
+ */
+
+ if (cw >= tp->snd_ssthresh)
+ incr = max((incr * incr / cw), 1);
+ }
+ tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale);
+}
+
+void
+tcp_newreno_pre_fr(struct tcpcb *tp, struct tcphdr *th) {
+#pragma unused(th)
+
+ uint32_t win;
+
+ win = min(tp->snd_wnd, tp->snd_cwnd) /
+ 2 / tp->t_maxseg;
+ if ( win < 2 )
+ win = 2;
+ tp->snd_ssthresh = win * tp->t_maxseg;
+}
+
+void
+tcp_newreno_post_fr(struct tcpcb *tp, struct tcphdr *th) {
+ int32_t ss;
+
+ ss = tp->snd_max - th->th_ack;
+
+ /*
+ * Complete ack. Inflate the congestion window to
+ * ssthresh and exit fast recovery.
+ *
+ * Window inflation should have left us with approx.
+ * snd_ssthresh outstanding data. But in case we
+ * would be inclined to send a burst, better to do
+ * it via the slow start mechanism.
+ */
+ if (ss < (int32_t)tp->snd_ssthresh)
+ tp->snd_cwnd = ss + tp->t_maxseg;
+ else
+ tp->snd_cwnd = tp->snd_ssthresh;
+ tp->t_bytes_acked = 0;
+}
+
+/* Function to change the congestion window when the retransmit
+ * timer fires.
+ */
+void
+tcp_newreno_after_timeout(struct tcpcb *tp) {
+ /*
+ * Close the congestion window down to one segment
+ * (we'll open it by one segment for each ack we get).
+ * Since we probably have a window's worth of unacked
+ * data accumulated, this "slow start" keeps us from
+ * dumping all that data as back-to-back packets (which
+ * might overwhelm an intermediate gateway).
+ *
+ * There are two phases to the opening: Initially we
+ * open by one mss on each ack. This makes the window
+ * size increase exponentially with time. If the
+ * window is larger than the path can handle, this
+ * exponential growth results in dropped packet(s)
+ * almost immediately. To get more time between
+ * drops but still "push" the network to take advantage
+ * of improving conditions, we switch from exponential
+ * to linear window opening at some threshhold size.
+ * For a threshhold, we use half the current window
+ * size, truncated to a multiple of the mss.
+ *
+ * (the minimum cwnd that will give us exponential
+ * growth is 2 mss. We don't allow the threshhold
+ * to go below this.)
+ */
+ if (tp->t_state >= TCPS_ESTABLISHED) {
+ u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
+ if (win < 2)
+ win = 2;
+ tp->snd_cwnd = tp->t_maxseg;
+ tp->snd_ssthresh = win * tp->t_maxseg;
+ tp->t_bytes_acked = 0;
+ tp->t_dupacks = 0;
+ }
+}
+
+/*
+ * Indicate whether this ack should be delayed.
+ * We can delay the ack if:
+ * - delayed acks are enabled and set to 1, same as when value is set to 2.
+ * We kept this for binary compatibility.
+ * - delayed acks are enabled and set to 2, will "ack every other packet"
+ * - if our last ack wasn't a 0-sized window.
+ * - if the peer hasn't sent us a TH_PUSH data packet (this solves 3649245).
+ * If TH_PUSH is set, take this as a clue that we need to ACK
+ * with no delay. This helps higher level protocols who won't send
+ * us more data even if the window is open because their
+ * last "segment" hasn't been ACKed
+ * - delayed acks are enabled and set to 3, will do "streaming detection"
+ * (see the comment in tcp_input.c) and
+ * - if we receive more than "maxseg_unacked" full packets in the last 100ms
+ * - if the connection is not in slow-start or idle or loss/recovery states
+ * - if those criteria aren't met, it will ack every other packet.
+ */
+
+int
+tcp_newreno_delay_ack(struct tcpcb *tp, struct tcphdr *th) {
+ switch (tcp_delack_enabled) {
+ case 1:
+ case 2:
+ if ((tp->t_flags & TF_RXWIN0SENT) == 0 &&
+ (th->th_flags & TH_PUSH) == 0 &&
+ (tp->t_flags & TF_DELACK) == 0)
+ return(1);
+ break;
+ case 3:
+ if ((tp->t_flags & TF_RXWIN0SENT) == 0 &&
+ (th->th_flags & TH_PUSH) == 0 &&
+ ((tp->t_unacksegs == 0) ||
+ ((tp->t_flags & TF_STRETCHACK) != 0 &&
+ tp->t_unacksegs < (maxseg_unacked - 1))))
+ return(1);
+ break;
+ }
+ return(0);
+}
+
+/* Switch to newreno from a different CC. If the connection is in
+ * congestion avoidance state, it can continue to use the current
+ * congestion window because it is going to be conservative. But
+ * if the connection is in slow-start, we will halve the congestion
+ * window and let newreno work from there.
+ */
+void
+tcp_newreno_switch_cc(struct tcpcb *tp, uint16_t old_index) {
+#pragma unused(old_index)
+
+ uint32_t cwnd = min(tp->snd_wnd, tp->snd_cwnd);
+ if (tp->snd_cwnd >= tp->snd_ssthresh) {
+ cwnd = cwnd / tp->t_maxseg;
+ } else {
+ cwnd = cwnd / 2 / tp->t_maxseg;
+ }
+ if (cwnd < 1)
+ cwnd = 1;
+ tp->snd_cwnd = cwnd * tp->t_maxseg;
+
+ /* Start counting bytes for RFC 3465 again */
+ tp->t_bytes_acked = 0;
+
+ OSIncrementAtomic((volatile SInt32 *)&tcp_cc_newreno.num_sockets);
+}
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