1 files changed, 356 insertions, 0 deletions

diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c
new file mode 100644
index 000000000000..4adc47c55351
--- /dev/null
+++ b/net/ipv4/tcp_illinois.c
@@ -0,0 +1,356 @@
+/*
+ * TCP Illinois congestion control.
+ * Home page:
+ *      http://www.ews.uiuc.edu/~shaoliu/tcpillinois/index.html
+ *
+ * The algorithm is described in:
+ * "TCP-Illinois: A Loss and Delay-Based Congestion Control Algorithm
+ *  for High-Speed Networks"
+ * http://www.ews.uiuc.edu/~shaoliu/papersandslides/liubassri06perf.pdf
+ *
+ * Implemented from description in paper and ns-2 simulation.
+ * Copyright (C) 2007 Stephen Hemminger <shemminger@linux-foundation.org>
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/inet_diag.h>
+#include <asm/div64.h>
+#include <net/tcp.h>
+
+#define ALPHA_SHIFT     7
+#define ALPHA_SCALE     (1u<<ALPHA_SHIFT)
+#define ALPHA_MIN       ((3*ALPHA_SCALE)/10)    /* ~0.3 */
+#define ALPHA_MAX       (10*ALPHA_SCALE)        /* 10.0 */
+#define ALPHA_BASE      ALPHA_SCALE             /* 1.0 */
+#define U32_MAX         ((u32)~0U)
+#define RTT_MAX         (U32_MAX / ALPHA_MAX)   /* 3.3 secs */
+
+#define BETA_SHIFT      6
+#define BETA_SCALE      (1u<<BETA_SHIFT)
+#define BETA_MIN        (BETA_SCALE/8)          /* 0.125 */
+#define BETA_MAX        (BETA_SCALE/2)          /* 0.5 */
+#define BETA_BASE       BETA_MAX
+
+static int win_thresh __read_mostly = 15;
+module_param(win_thresh, int, 0);
+MODULE_PARM_DESC(win_thresh, "Window threshold for starting adaptive sizing");
+
+static int theta __read_mostly = 5;
+module_param(theta, int, 0);
+MODULE_PARM_DESC(theta, "# of fast RTT's before full growth");
+
+/* TCP Illinois Parameters */
+struct illinois {
+        u64     sum_rtt;        /* sum of rtt's measured within last rtt */
+        u16     cnt_rtt;        /* # of rtts measured within last rtt */
+        u32     base_rtt;       /* min of all rtt in usec */
+        u32     max_rtt;        /* max of all rtt in usec */
+        u32     end_seq;        /* right edge of current RTT */
+        u32     alpha;          /* Additive increase */
+        u32     beta;           /* Muliplicative decrease */
+        u16     acked;          /* # packets acked by current ACK */
+        u8      rtt_above;      /* average rtt has gone above threshold */
+        u8      rtt_low;        /* # of rtts measurements below threshold */
+};
+
+static void rtt_reset(struct sock *sk)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        struct illinois *ca = inet_csk_ca(sk);
+
+        ca->end_seq = tp->snd_nxt;
+        ca->cnt_rtt = 0;
+        ca->sum_rtt = 0;
+
+        /* TODO: age max_rtt? */
+}
+
+static void tcp_illinois_init(struct sock *sk)
+{
+        struct illinois *ca = inet_csk_ca(sk);
+
+        ca->alpha = ALPHA_MAX;
+        ca->beta = BETA_BASE;
+        ca->base_rtt = 0x7fffffff;
+        ca->max_rtt = 0;
+
+        ca->acked = 0;
+        ca->rtt_low = 0;
+        ca->rtt_above = 0;
+
+        rtt_reset(sk);
+}
+
+/* Measure RTT for each ack. */
+static void tcp_illinois_acked(struct sock *sk, u32 pkts_acked, ktime_t last)
+{
+        struct illinois *ca = inet_csk_ca(sk);
+        u32 rtt;
+
+        ca->acked = pkts_acked;
+
+        rtt = ktime_to_us(net_timedelta(last));
+
+        /* ignore bogus values, this prevents wraparound in alpha math */
+        if (rtt > RTT_MAX)
+                rtt = RTT_MAX;
+
+        /* keep track of minimum RTT seen so far */
+        if (ca->base_rtt > rtt)
+                ca->base_rtt = rtt;
+
+        /* and max */
+        if (ca->max_rtt < rtt)
+                ca->max_rtt = rtt;
+
+        ++ca->cnt_rtt;
+        ca->sum_rtt += rtt;
+}
+
+/* Maximum queuing delay */
+static inline u32 max_delay(const struct illinois *ca)
+{
+        return ca->max_rtt - ca->base_rtt;
+}
+
+/* Average queuing delay */
+static inline u32 avg_delay(const struct illinois *ca)
+{
+        u64 t = ca->sum_rtt;
+
+        do_div(t, ca->cnt_rtt);
+        return t - ca->base_rtt;
+}
+
+/*
+ * Compute value of alpha used for additive increase.
+ * If small window then use 1.0, equivalent to Reno.
+ *
+ * For larger windows, adjust based on average delay.
+ * A. If average delay is at minimum (we are uncongested),
+ *    then use large alpha (10.0) to increase faster.
+ * B. If average delay is at maximum (getting congested)
+ *    then use small alpha (0.3)
+ *
+ * The result is a convex window growth curve.
+ */
+static u32 alpha(struct illinois *ca, u32 da, u32 dm)
+{
+        u32 d1 = dm / 100;      /* Low threshold */
+
+        if (da <= d1) {
+                /* If never got out of low delay zone, then use max */
+                if (!ca->rtt_above)
+                        return ALPHA_MAX;
+
+                /* Wait for 5 good RTT's before allowing alpha to go alpha max.
+                 * This prevents one good RTT from causing sudden window increase.
+                 */
+                if (++ca->rtt_low < theta)
+                        return ca->alpha;
+
+                ca->rtt_low = 0;
+                ca->rtt_above = 0;
+                return ALPHA_MAX;
+        }
+
+        ca->rtt_above = 1;
+
+        /*
+         * Based on:
+         *
+         *      (dm - d1) amin amax
+         * k1 = -------------------
+         *         amax - amin
+         *
+         *       (dm - d1) amin
+         * k2 = ----------------  - d1
+         *        amax - amin
+         *
+         *             k1
+         * alpha = ----------
+         *          k2 + da
+         */
+
+        dm -= d1;
+        da -= d1;
+        return (dm * ALPHA_MAX) /
+                (dm + (da  * (ALPHA_MAX - ALPHA_MIN)) / ALPHA_MIN);
+}
+
+/*
+ * Beta used for multiplicative decrease.
+ * For small window sizes returns same value as Reno (0.5)
+ *
+ * If delay is small (10% of max) then beta = 1/8
+ * If delay is up to 80% of max then beta = 1/2
+ * In between is a linear function
+ */
+static u32 beta(u32 da, u32 dm)
+{
+        u32 d2, d3;
+
+        d2 = dm / 10;
+        if (da <= d2)
+                return BETA_MIN;
+
+        d3 = (8 * dm) / 10;
+        if (da >= d3 || d3 <= d2)
+                return BETA_MAX;
+
+        /*
+         * Based on:
+         *
+         *       bmin d3 - bmax d2
+         * k3 = -------------------
+         *         d3 - d2
+         *
+         *       bmax - bmin
+         * k4 = -------------
+         *         d3 - d2
+         *
+         * b = k3 + k4 da
+         */
+        return (BETA_MIN * d3 - BETA_MAX * d2 + (BETA_MAX - BETA_MIN) * da)
+                / (d3 - d2);
+}
+
+/* Update alpha and beta values once per RTT */
+static void update_params(struct sock *sk)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        struct illinois *ca = inet_csk_ca(sk);
+
+        if (tp->snd_cwnd < win_thresh) {
+                ca->alpha = ALPHA_BASE;
+                ca->beta = BETA_BASE;
+        } else if (ca->cnt_rtt > 0) {
+                u32 dm = max_delay(ca);
+                u32 da = avg_delay(ca);
+
+                ca->alpha = alpha(ca, da, dm);
+                ca->beta = beta(da, dm);
+        }
+
+        rtt_reset(sk);
+}
+
+/*
+ * In case of loss, reset to default values
+ */
+static void tcp_illinois_state(struct sock *sk, u8 new_state)
+{
+        struct illinois *ca = inet_csk_ca(sk);
+
+        if (new_state == TCP_CA_Loss) {
+                ca->alpha = ALPHA_BASE;
+                ca->beta = BETA_BASE;
+                ca->rtt_low = 0;
+                ca->rtt_above = 0;
+                rtt_reset(sk);
+        }
+}
+
+/*
+ * Increase window in response to successful acknowledgment.
+ */
+static void tcp_illinois_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
+                                    u32 in_flight, int flag)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        struct illinois *ca = inet_csk_ca(sk);
+
+        if (after(ack, ca->end_seq))
+                update_params(sk);
+
+        /* RFC2861 only increase cwnd if fully utilized */
+        if (!tcp_is_cwnd_limited(sk, in_flight))
+                return;
+
+        /* In slow start */
+        if (tp->snd_cwnd <= tp->snd_ssthresh)
+                tcp_slow_start(tp);
+
+        else {
+                u32 delta;
+
+                /* snd_cwnd_cnt is # of packets since last cwnd increment */
+                tp->snd_cwnd_cnt += ca->acked;
+                ca->acked = 1;
+
+                /* This is close approximation of:
+                 * tp->snd_cwnd += alpha/tp->snd_cwnd
+                */
+                delta = (tp->snd_cwnd_cnt * ca->alpha) >> ALPHA_SHIFT;
+                if (delta >= tp->snd_cwnd) {
+                        tp->snd_cwnd = min(tp->snd_cwnd + delta / tp->snd_cwnd,
+                                           (u32) tp->snd_cwnd_clamp);
+                        tp->snd_cwnd_cnt = 0;
+                }
+        }
+}
+
+static u32 tcp_illinois_ssthresh(struct sock *sk)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        struct illinois *ca = inet_csk_ca(sk);
+
+        /* Multiplicative decrease */
+        return max((tp->snd_cwnd * ca->beta) >> BETA_SHIFT, 2U);
+}
+
+
+/* Extract info for Tcp socket info provided via netlink. */
+static void tcp_illinois_info(struct sock *sk, u32 ext,
+                              struct sk_buff *skb)
+{
+        const struct illinois *ca = inet_csk_ca(sk);
+
+        if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
+                struct tcpvegas_info info = {
+                        .tcpv_enabled = 1,
+                        .tcpv_rttcnt = ca->cnt_rtt,
+                        .tcpv_minrtt = ca->base_rtt,
+                };
+                u64 t = ca->sum_rtt;
+
+                do_div(t, ca->cnt_rtt);
+                info.tcpv_rtt = t;
+
+                nla_put(skb, INET_DIAG_VEGASINFO, sizeof(info), &info);
+        }
+}
+
+static struct tcp_congestion_ops tcp_illinois = {
+        .flags          = TCP_CONG_RTT_STAMP,
+        .init           = tcp_illinois_init,
+        .ssthresh       = tcp_illinois_ssthresh,
+        .min_cwnd       = tcp_reno_min_cwnd,
+        .cong_avoid     = tcp_illinois_cong_avoid,
+        .set_state      = tcp_illinois_state,
+        .get_info       = tcp_illinois_info,
+        .pkts_acked     = tcp_illinois_acked,
+
+        .owner          = THIS_MODULE,
+        .name           = "illinois",
+};
+
+static int __init tcp_illinois_register(void)
+{
+        BUILD_BUG_ON(sizeof(struct illinois) > ICSK_CA_PRIV_SIZE);
+        return tcp_register_congestion_control(&tcp_illinois);
+}
+
+static void __exit tcp_illinois_unregister(void)
+{
+        tcp_unregister_congestion_control(&tcp_illinois);
+}
+
+module_init(tcp_illinois_register);
+module_exit(tcp_illinois_unregister);
+
+MODULE_AUTHOR("Stephen Hemminger, Shao Liu");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("TCP Illinois");
+MODULE_VERSION("1.0");