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/*
* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
* $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.16 2001/08/22 00:59:12 silby Exp $
*/
#include "tcp_includes.h"
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/socketvar.h>
#include <net/route.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#include <netinet/ip_var.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_congestion_avd(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);
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);
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,
.congestion_avd = tcp_newreno_congestion_avd,
.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
};
int
tcp_newreno_init(struct tcpcb *tp)
{
#pragma unused(tp)
os_atomic_inc(&tcp_cc_newreno.num_sockets, relaxed);
return 0;
}
int
tcp_newreno_cleanup(struct tcpcb *tp)
{
#pragma unused(tp)
os_atomic_dec(&tcp_cc_newreno.num_sockets, relaxed);
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)
{
tcp_cc_cwnd_init_or_reset(tp);
}
/* Function to handle an in-sequence ack during congestion avoidance phase.
* This will get called from header prediction code.
*/
void
tcp_newreno_congestion_avd(struct tcpcb *tp, struct tcphdr *th)
{
uint32_t acked = 0;
acked = BYTES_ACKED(th, tp);
/*
* 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.
*/
uint32_t cw = tp->snd_cwnd;
uint32_t incr = tp->t_maxseg;
uint32_t acked = 0;
acked = BYTES_ACKED(th, tp);
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)
*/
uint32_t abc_lim;
abc_lim = (tp->snd_nxt == tp->snd_max) ? incr * 2 : incr;
incr = ulmin(acked, abc_lim);
}
tp->snd_cwnd = min(cw + incr, TCP_MAXWIN << tp->snd_scale);
}
void
tcp_newreno_pre_fr(struct tcpcb *tp)
{
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;
tcp_cc_resize_sndbuf(tp);
}
void
tcp_newreno_post_fr(struct tcpcb *tp, struct tcphdr *th)
{
int32_t ss;
if (th) {
ss = tp->snd_max - th->th_ack;
} else {
ss = tp->snd_max - tp->snd_una;
}
/*
* 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 the flight size is zero, then make congestion
* window to be worth at least 2 segments to avoid
* delayed acknowledgement (draft-ietf-tcpm-rfc3782-bis-05).
*/
if (ss < (int32_t)tp->snd_ssthresh) {
tp->snd_cwnd = max(ss, tp->t_maxseg) + 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_ssthresh = win * tp->t_maxseg;
tp->snd_cwnd = tp->t_maxseg;
tcp_cc_resize_sndbuf(tp);
}
}
/*
* 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)
{
return tcp_cc_delay_ack(tp, th);
}
/* 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)
{
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;
}
tp->snd_cwnd = max(tcp_initial_cwnd(tp), cwnd * tp->t_maxseg);
/* Start counting bytes for RFC 3465 again */
tp->t_bytes_acked = 0;
os_atomic_inc(&tcp_cc_newreno.num_sockets, relaxed);
}