v4.19.13 snapshot.
diff --git a/net/ipv4/tcp_htcp.c b/net/ipv4/tcp_htcp.c
new file mode 100644
index 0000000..082d479
--- /dev/null
+++ b/net/ipv4/tcp_htcp.c
@@ -0,0 +1,316 @@
+/*
+ * H-TCP congestion control. The algorithm is detailed in:
+ * R.N.Shorten, D.J.Leith:
+ * "H-TCP: TCP for high-speed and long-distance networks"
+ * Proc. PFLDnet, Argonne, 2004.
+ * http://www.hamilton.ie/net/htcp3.pdf
+ */
+
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <net/tcp.h>
+
+#define ALPHA_BASE (1<<7) /* 1.0 with shift << 7 */
+#define BETA_MIN (1<<6) /* 0.5 with shift << 7 */
+#define BETA_MAX 102 /* 0.8 with shift << 7 */
+
+static int use_rtt_scaling __read_mostly = 1;
+module_param(use_rtt_scaling, int, 0644);
+MODULE_PARM_DESC(use_rtt_scaling, "turn on/off RTT scaling");
+
+static int use_bandwidth_switch __read_mostly = 1;
+module_param(use_bandwidth_switch, int, 0644);
+MODULE_PARM_DESC(use_bandwidth_switch, "turn on/off bandwidth switcher");
+
+struct htcp {
+ u32 alpha; /* Fixed point arith, << 7 */
+ u8 beta; /* Fixed point arith, << 7 */
+ u8 modeswitch; /* Delay modeswitch
+ until we had at least one congestion event */
+ u16 pkts_acked;
+ u32 packetcount;
+ u32 minRTT;
+ u32 maxRTT;
+ u32 last_cong; /* Time since last congestion event end */
+ u32 undo_last_cong;
+
+ u32 undo_maxRTT;
+ u32 undo_old_maxB;
+
+ /* Bandwidth estimation */
+ u32 minB;
+ u32 maxB;
+ u32 old_maxB;
+ u32 Bi;
+ u32 lasttime;
+};
+
+static inline u32 htcp_cong_time(const struct htcp *ca)
+{
+ return jiffies - ca->last_cong;
+}
+
+static inline u32 htcp_ccount(const struct htcp *ca)
+{
+ return htcp_cong_time(ca) / ca->minRTT;
+}
+
+static inline void htcp_reset(struct htcp *ca)
+{
+ ca->undo_last_cong = ca->last_cong;
+ ca->undo_maxRTT = ca->maxRTT;
+ ca->undo_old_maxB = ca->old_maxB;
+
+ ca->last_cong = jiffies;
+}
+
+static u32 htcp_cwnd_undo(struct sock *sk)
+{
+ struct htcp *ca = inet_csk_ca(sk);
+
+ if (ca->undo_last_cong) {
+ ca->last_cong = ca->undo_last_cong;
+ ca->maxRTT = ca->undo_maxRTT;
+ ca->old_maxB = ca->undo_old_maxB;
+ ca->undo_last_cong = 0;
+ }
+
+ return tcp_reno_undo_cwnd(sk);
+}
+
+static inline void measure_rtt(struct sock *sk, u32 srtt)
+{
+ const struct inet_connection_sock *icsk = inet_csk(sk);
+ struct htcp *ca = inet_csk_ca(sk);
+
+ /* keep track of minimum RTT seen so far, minRTT is zero at first */
+ if (ca->minRTT > srtt || !ca->minRTT)
+ ca->minRTT = srtt;
+
+ /* max RTT */
+ if (icsk->icsk_ca_state == TCP_CA_Open) {
+ if (ca->maxRTT < ca->minRTT)
+ ca->maxRTT = ca->minRTT;
+ if (ca->maxRTT < srtt &&
+ srtt <= ca->maxRTT + msecs_to_jiffies(20))
+ ca->maxRTT = srtt;
+ }
+}
+
+static void measure_achieved_throughput(struct sock *sk,
+ const struct ack_sample *sample)
+{
+ const struct inet_connection_sock *icsk = inet_csk(sk);
+ const struct tcp_sock *tp = tcp_sk(sk);
+ struct htcp *ca = inet_csk_ca(sk);
+ u32 now = tcp_jiffies32;
+
+ if (icsk->icsk_ca_state == TCP_CA_Open)
+ ca->pkts_acked = sample->pkts_acked;
+
+ if (sample->rtt_us > 0)
+ measure_rtt(sk, usecs_to_jiffies(sample->rtt_us));
+
+ if (!use_bandwidth_switch)
+ return;
+
+ /* achieved throughput calculations */
+ if (!((1 << icsk->icsk_ca_state) & (TCPF_CA_Open | TCPF_CA_Disorder))) {
+ ca->packetcount = 0;
+ ca->lasttime = now;
+ return;
+ }
+
+ ca->packetcount += sample->pkts_acked;
+
+ if (ca->packetcount >= tp->snd_cwnd - (ca->alpha >> 7 ? : 1) &&
+ now - ca->lasttime >= ca->minRTT &&
+ ca->minRTT > 0) {
+ __u32 cur_Bi = ca->packetcount * HZ / (now - ca->lasttime);
+
+ if (htcp_ccount(ca) <= 3) {
+ /* just after backoff */
+ ca->minB = ca->maxB = ca->Bi = cur_Bi;
+ } else {
+ ca->Bi = (3 * ca->Bi + cur_Bi) / 4;
+ if (ca->Bi > ca->maxB)
+ ca->maxB = ca->Bi;
+ if (ca->minB > ca->maxB)
+ ca->minB = ca->maxB;
+ }
+ ca->packetcount = 0;
+ ca->lasttime = now;
+ }
+}
+
+static inline void htcp_beta_update(struct htcp *ca, u32 minRTT, u32 maxRTT)
+{
+ if (use_bandwidth_switch) {
+ u32 maxB = ca->maxB;
+ u32 old_maxB = ca->old_maxB;
+
+ ca->old_maxB = ca->maxB;
+ if (!between(5 * maxB, 4 * old_maxB, 6 * old_maxB)) {
+ ca->beta = BETA_MIN;
+ ca->modeswitch = 0;
+ return;
+ }
+ }
+
+ if (ca->modeswitch && minRTT > msecs_to_jiffies(10) && maxRTT) {
+ ca->beta = (minRTT << 7) / maxRTT;
+ if (ca->beta < BETA_MIN)
+ ca->beta = BETA_MIN;
+ else if (ca->beta > BETA_MAX)
+ ca->beta = BETA_MAX;
+ } else {
+ ca->beta = BETA_MIN;
+ ca->modeswitch = 1;
+ }
+}
+
+static inline void htcp_alpha_update(struct htcp *ca)
+{
+ u32 minRTT = ca->minRTT;
+ u32 factor = 1;
+ u32 diff = htcp_cong_time(ca);
+
+ if (diff > HZ) {
+ diff -= HZ;
+ factor = 1 + (10 * diff + ((diff / 2) * (diff / 2) / HZ)) / HZ;
+ }
+
+ if (use_rtt_scaling && minRTT) {
+ u32 scale = (HZ << 3) / (10 * minRTT);
+
+ /* clamping ratio to interval [0.5,10]<<3 */
+ scale = min(max(scale, 1U << 2), 10U << 3);
+ factor = (factor << 3) / scale;
+ if (!factor)
+ factor = 1;
+ }
+
+ ca->alpha = 2 * factor * ((1 << 7) - ca->beta);
+ if (!ca->alpha)
+ ca->alpha = ALPHA_BASE;
+}
+
+/*
+ * After we have the rtt data to calculate beta, we'd still prefer to wait one
+ * rtt before we adjust our beta to ensure we are working from a consistent
+ * data.
+ *
+ * This function should be called when we hit a congestion event since only at
+ * that point do we really have a real sense of maxRTT (the queues en route
+ * were getting just too full now).
+ */
+static void htcp_param_update(struct sock *sk)
+{
+ struct htcp *ca = inet_csk_ca(sk);
+ u32 minRTT = ca->minRTT;
+ u32 maxRTT = ca->maxRTT;
+
+ htcp_beta_update(ca, minRTT, maxRTT);
+ htcp_alpha_update(ca);
+
+ /* add slowly fading memory for maxRTT to accommodate routing changes */
+ if (minRTT > 0 && maxRTT > minRTT)
+ ca->maxRTT = minRTT + ((maxRTT - minRTT) * 95) / 100;
+}
+
+static u32 htcp_recalc_ssthresh(struct sock *sk)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+ const struct htcp *ca = inet_csk_ca(sk);
+
+ htcp_param_update(sk);
+ return max((tp->snd_cwnd * ca->beta) >> 7, 2U);
+}
+
+static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 acked)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct htcp *ca = inet_csk_ca(sk);
+
+ if (!tcp_is_cwnd_limited(sk))
+ return;
+
+ if (tcp_in_slow_start(tp))
+ tcp_slow_start(tp, acked);
+ else {
+ /* In dangerous area, increase slowly.
+ * In theory this is tp->snd_cwnd += alpha / tp->snd_cwnd
+ */
+ if ((tp->snd_cwnd_cnt * ca->alpha)>>7 >= tp->snd_cwnd) {
+ if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+ tp->snd_cwnd++;
+ tp->snd_cwnd_cnt = 0;
+ htcp_alpha_update(ca);
+ } else
+ tp->snd_cwnd_cnt += ca->pkts_acked;
+
+ ca->pkts_acked = 1;
+ }
+}
+
+static void htcp_init(struct sock *sk)
+{
+ struct htcp *ca = inet_csk_ca(sk);
+
+ memset(ca, 0, sizeof(struct htcp));
+ ca->alpha = ALPHA_BASE;
+ ca->beta = BETA_MIN;
+ ca->pkts_acked = 1;
+ ca->last_cong = jiffies;
+}
+
+static void htcp_state(struct sock *sk, u8 new_state)
+{
+ switch (new_state) {
+ case TCP_CA_Open:
+ {
+ struct htcp *ca = inet_csk_ca(sk);
+
+ if (ca->undo_last_cong) {
+ ca->last_cong = jiffies;
+ ca->undo_last_cong = 0;
+ }
+ }
+ break;
+ case TCP_CA_CWR:
+ case TCP_CA_Recovery:
+ case TCP_CA_Loss:
+ htcp_reset(inet_csk_ca(sk));
+ break;
+ }
+}
+
+static struct tcp_congestion_ops htcp __read_mostly = {
+ .init = htcp_init,
+ .ssthresh = htcp_recalc_ssthresh,
+ .cong_avoid = htcp_cong_avoid,
+ .set_state = htcp_state,
+ .undo_cwnd = htcp_cwnd_undo,
+ .pkts_acked = measure_achieved_throughput,
+ .owner = THIS_MODULE,
+ .name = "htcp",
+};
+
+static int __init htcp_register(void)
+{
+ BUILD_BUG_ON(sizeof(struct htcp) > ICSK_CA_PRIV_SIZE);
+ BUILD_BUG_ON(BETA_MIN >= BETA_MAX);
+ return tcp_register_congestion_control(&htcp);
+}
+
+static void __exit htcp_unregister(void)
+{
+ tcp_unregister_congestion_control(&htcp);
+}
+
+module_init(htcp_register);
+module_exit(htcp_unregister);
+
+MODULE_AUTHOR("Baruch Even");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("H-TCP");