1 files changed, 411 insertions, 0 deletions

diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
new file mode 100644
index 000000000000..31a4986dfbf7
--- /dev/null
+++ b/net/ipv4/tcp_cubic.c
@@ -0,0 +1,411 @@
+/*
+ * TCP CUBIC: Binary Increase Congestion control for TCP v2.0
+ *
+ * This is from the implementation of CUBIC TCP in
+ * Injong Rhee, Lisong Xu.
+ *  "CUBIC: A New TCP-Friendly High-Speed TCP Variant
+ *  in PFLDnet 2005
+ * Available from:
+ *  http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/cubic-paper.pdf
+ *
+ * Unless CUBIC is enabled and congestion window is large
+ * this behaves the same as the original Reno.
+ */
+
+#include <linux/config.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <net/tcp.h>
+#include <asm/div64.h>
+
+#define BICTCP_BETA_SCALE    1024       /* Scale factor beta calculation
+                                         * max_cwnd = snd_cwnd * beta
+                                         */
+#define BICTCP_B                4        /*
+                                          * In binary search,
+                                          * go to point (max+min)/N
+                                          */
+#define BICTCP_HZ               10      /* BIC HZ 2^10 = 1024 */
+
+static int fast_convergence = 1;
+static int max_increment = 16;
+static int beta = 819;          /* = 819/1024 (BICTCP_BETA_SCALE) */
+static int initial_ssthresh = 100;
+static int bic_scale = 41;
+static int tcp_friendliness = 1;
+
+static u32 cube_rtt_scale;
+static u32 beta_scale;
+static u64 cube_factor;
+
+/* Note parameters that are used for precomputing scale factors are read-only */
+module_param(fast_convergence, int, 0644);
+MODULE_PARM_DESC(fast_convergence, "turn on/off fast convergence");
+module_param(max_increment, int, 0644);
+MODULE_PARM_DESC(max_increment, "Limit on increment allowed during binary search");
+module_param(beta, int, 0444);
+MODULE_PARM_DESC(beta, "beta for multiplicative increase");
+module_param(initial_ssthresh, int, 0644);
+MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold");
+module_param(bic_scale, int, 0444);
+MODULE_PARM_DESC(bic_scale, "scale (scaled by 1024) value for bic function (bic_scale/1024)");
+module_param(tcp_friendliness, int, 0644);
+MODULE_PARM_DESC(tcp_friendliness, "turn on/off tcp friendliness");
+
+#include <asm/div64.h>
+
+/* BIC TCP Parameters */
+struct bictcp {
+        u32     cnt;            /* increase cwnd by 1 after ACKs */
+        u32     last_max_cwnd;  /* last maximum snd_cwnd */
+        u32     loss_cwnd;      /* congestion window at last loss */
+        u32     last_cwnd;      /* the last snd_cwnd */
+        u32     last_time;      /* time when updated last_cwnd */
+        u32     bic_origin_point;/* origin point of bic function */
+        u32     bic_K;          /* time to origin point from the beginning of the current epoch */
+        u32     delay_min;      /* min delay */
+        u32     epoch_start;    /* beginning of an epoch */
+        u32     ack_cnt;        /* number of acks */
+        u32     tcp_cwnd;       /* estimated tcp cwnd */
+#define ACK_RATIO_SHIFT 4
+        u32     delayed_ack;    /* estimate the ratio of Packets/ACKs << 4 */
+};
+
+static inline void bictcp_reset(struct bictcp *ca)
+{
+        ca->cnt = 0;
+        ca->last_max_cwnd = 0;
+        ca->loss_cwnd = 0;
+        ca->last_cwnd = 0;
+        ca->last_time = 0;
+        ca->bic_origin_point = 0;
+        ca->bic_K = 0;
+        ca->delay_min = 0;
+        ca->epoch_start = 0;
+        ca->delayed_ack = 2 << ACK_RATIO_SHIFT;
+        ca->ack_cnt = 0;
+        ca->tcp_cwnd = 0;
+}
+
+static void bictcp_init(struct sock *sk)
+{
+        bictcp_reset(inet_csk_ca(sk));
+        if (initial_ssthresh)
+                tcp_sk(sk)->snd_ssthresh = initial_ssthresh;
+}
+
+/* 64bit divisor, dividend and result. dynamic precision */
+static inline u_int64_t div64_64(u_int64_t dividend, u_int64_t divisor)
+{
+        u_int32_t d = divisor;
+
+        if (divisor > 0xffffffffULL) {
+                unsigned int shift = fls(divisor >> 32);
+
+                d = divisor >> shift;
+                dividend >>= shift;
+        }
+
+        /* avoid 64 bit division if possible */
+        if (dividend >> 32)
+                do_div(dividend, d);
+        else
+                dividend = (uint32_t) dividend / d;
+
+        return dividend;
+}
+
+/*
+ * calculate the cubic root of x using Newton-Raphson
+ */
+static u32 cubic_root(u64 a)
+{
+        u32 x, x1;
+
+        /* Initial estimate is based on:
+         * cbrt(x) = exp(log(x) / 3)
+         */
+        x = 1u << (fls64(a)/3);
+
+        /*
+         * Iteration based on:
+         *                         2
+         * x    = ( 2 * x  +  a / x  ) / 3
+         *  k+1          k         k
+         */
+        do {
+                x1 = x;
+                x = (2 * x + (uint32_t) div64_64(a, x*x)) / 3;
+        } while (abs(x1 - x) > 1);
+
+        return x;
+}
+
+/*
+ * Compute congestion window to use.
+ */
+static inline void bictcp_update(struct bictcp *ca, u32 cwnd)
+{
+        u64 offs;
+        u32 delta, t, bic_target, min_cnt, max_cnt;
+
+        ca->ack_cnt++;  /* count the number of ACKs */
+
+        if (ca->last_cwnd == cwnd &&
+            (s32)(tcp_time_stamp - ca->last_time) <= HZ / 32)
+                return;
+
+        ca->last_cwnd = cwnd;
+        ca->last_time = tcp_time_stamp;
+
+        if (ca->epoch_start == 0) {
+                ca->epoch_start = tcp_time_stamp;       /* record the beginning of an epoch */
+                ca->ack_cnt = 1;                        /* start counting */
+                ca->tcp_cwnd = cwnd;                    /* syn with cubic */
+
+                if (ca->last_max_cwnd <= cwnd) {
+                        ca->bic_K = 0;
+                        ca->bic_origin_point = cwnd;
+                } else {
+                        /* Compute new K based on
+                         * (wmax-cwnd) * (srtt>>3 / HZ) / c * 2^(3*bictcp_HZ)
+                         */
+                        ca->bic_K = cubic_root(cube_factor
+                                               * (ca->last_max_cwnd - cwnd));
+                        ca->bic_origin_point = ca->last_max_cwnd;
+                }
+        }
+
+        /* cubic function - calc*/
+        /* calculate c * time^3 / rtt,
+         *  while considering overflow in calculation of time^3
+         * (so time^3 is done by using 64 bit)
+         * and without the support of division of 64bit numbers
+         * (so all divisions are done by using 32 bit)
+         *  also NOTE the unit of those veriables
+         *        time  = (t - K) / 2^bictcp_HZ
+         *        c = bic_scale >> 10
+         * rtt  = (srtt >> 3) / HZ
+         * !!! The following code does not have overflow problems,
+         * if the cwnd < 1 million packets !!!
+         */
+
+        /* change the unit from HZ to bictcp_HZ */
+        t = ((tcp_time_stamp + ca->delay_min - ca->epoch_start)
+             << BICTCP_HZ) / HZ;
+
+        if (t < ca->bic_K)              /* t - K */
+                offs = ca->bic_K - t;
+        else
+                offs = t - ca->bic_K;
+
+        /* c/rtt * (t-K)^3 */
+        delta = (cube_rtt_scale * offs * offs * offs) >> (10+3*BICTCP_HZ);
+        if (t < ca->bic_K)                                      /* below origin*/
+                bic_target = ca->bic_origin_point - delta;
+        else                                                    /* above origin*/
+                bic_target = ca->bic_origin_point + delta;
+
+        /* cubic function - calc bictcp_cnt*/
+        if (bic_target > cwnd) {
+                ca->cnt = cwnd / (bic_target - cwnd);
+        } else {
+                ca->cnt = 100 * cwnd;              /* very small increment*/
+        }
+
+        if (ca->delay_min > 0) {
+                /* max increment = Smax * rtt / 0.1  */
+                min_cnt = (cwnd * HZ * 8)/(10 * max_increment * ca->delay_min);
+                if (ca->cnt < min_cnt)
+                        ca->cnt = min_cnt;
+        }
+
+        /* slow start and low utilization  */
+        if (ca->loss_cwnd == 0)         /* could be aggressive in slow start */
+                ca->cnt = 50;
+
+        /* TCP Friendly */
+        if (tcp_friendliness) {
+                u32 scale = beta_scale;
+                delta = (cwnd * scale) >> 3;
+                while (ca->ack_cnt > delta) {           /* update tcp cwnd */
+                        ca->ack_cnt -= delta;
+                        ca->tcp_cwnd++;
+                }
+
+                if (ca->tcp_cwnd > cwnd){       /* if bic is slower than tcp */
+                        delta = ca->tcp_cwnd - cwnd;
+                        max_cnt = cwnd / delta;
+                        if (ca->cnt > max_cnt)
+                                ca->cnt = max_cnt;
+                }
+        }
+
+        ca->cnt = (ca->cnt << ACK_RATIO_SHIFT) / ca->delayed_ack;
+        if (ca->cnt == 0)                       /* cannot be zero */
+                ca->cnt = 1;
+}
+
+
+/* Keep track of minimum rtt */
+static inline void measure_delay(struct sock *sk)
+{
+        const struct tcp_sock *tp = tcp_sk(sk);
+        struct bictcp *ca = inet_csk_ca(sk);
+        u32 delay;
+
+        /* No time stamp */
+        if (!(tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) ||
+             /* Discard delay samples right after fast recovery */
+            (s32)(tcp_time_stamp - ca->epoch_start) < HZ)
+                return;
+
+        delay = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
+        if (delay == 0)
+                delay = 1;
+
+        /* first time call or link delay decreases */
+        if (ca->delay_min == 0 || ca->delay_min > delay)
+                ca->delay_min = delay;
+}
+
+static void bictcp_cong_avoid(struct sock *sk, u32 ack,
+                              u32 seq_rtt, u32 in_flight, int data_acked)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        struct bictcp *ca = inet_csk_ca(sk);
+
+        if (data_acked)
+                measure_delay(sk);
+
+        if (!tcp_is_cwnd_limited(sk, in_flight))
+                return;
+
+        if (tp->snd_cwnd <= tp->snd_ssthresh)
+                tcp_slow_start(tp);
+        else {
+                bictcp_update(ca, tp->snd_cwnd);
+
+                /* In dangerous area, increase slowly.
+                 * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
+                 */
+                if (tp->snd_cwnd_cnt >= ca->cnt) {
+                        if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+                                tp->snd_cwnd++;
+                        tp->snd_cwnd_cnt = 0;
+                } else
+                        tp->snd_cwnd_cnt++;
+        }
+
+}
+
+static u32 bictcp_recalc_ssthresh(struct sock *sk)
+{
+        const struct tcp_sock *tp = tcp_sk(sk);
+        struct bictcp *ca = inet_csk_ca(sk);
+
+        ca->epoch_start = 0;    /* end of epoch */
+
+        /* Wmax and fast convergence */
+        if (tp->snd_cwnd < ca->last_max_cwnd && fast_convergence)
+                ca->last_max_cwnd = (tp->snd_cwnd * (BICTCP_BETA_SCALE + beta))
+                        / (2 * BICTCP_BETA_SCALE);
+        else
+                ca->last_max_cwnd = tp->snd_cwnd;
+
+        ca->loss_cwnd = tp->snd_cwnd;
+
+        return max((tp->snd_cwnd * beta) / BICTCP_BETA_SCALE, 2U);
+}
+
+static u32 bictcp_undo_cwnd(struct sock *sk)
+{
+        struct bictcp *ca = inet_csk_ca(sk);
+
+        return max(tcp_sk(sk)->snd_cwnd, ca->last_max_cwnd);
+}
+
+static u32 bictcp_min_cwnd(struct sock *sk)
+{
+        return tcp_sk(sk)->snd_ssthresh;
+}
+
+static void bictcp_state(struct sock *sk, u8 new_state)
+{
+        if (new_state == TCP_CA_Loss)
+                bictcp_reset(inet_csk_ca(sk));
+}
+
+/* Track delayed acknowledgment ratio using sliding window
+ * ratio = (15*ratio + sample) / 16
+ */
+static void bictcp_acked(struct sock *sk, u32 cnt)
+{
+        const struct inet_connection_sock *icsk = inet_csk(sk);
+
+        if (cnt > 0 && icsk->icsk_ca_state == TCP_CA_Open) {
+                struct bictcp *ca = inet_csk_ca(sk);
+                cnt -= ca->delayed_ack >> ACK_RATIO_SHIFT;
+                ca->delayed_ack += cnt;
+        }
+}
+
+
+static struct tcp_congestion_ops cubictcp = {
+        .init           = bictcp_init,
+        .ssthresh       = bictcp_recalc_ssthresh,
+        .cong_avoid     = bictcp_cong_avoid,
+        .set_state      = bictcp_state,
+        .undo_cwnd      = bictcp_undo_cwnd,
+        .min_cwnd       = bictcp_min_cwnd,
+        .pkts_acked     = bictcp_acked,
+        .owner          = THIS_MODULE,
+        .name           = "cubic",
+};
+
+static int __init cubictcp_register(void)
+{
+        BUG_ON(sizeof(struct bictcp) > ICSK_CA_PRIV_SIZE);
+
+        /* Precompute a bunch of the scaling factors that are used per-packet
+         * based on SRTT of 100ms
+         */
+
+        beta_scale = 8*(BICTCP_BETA_SCALE+beta)/ 3 / (BICTCP_BETA_SCALE - beta);
+
+        cube_rtt_scale = (bic_scale << 3) / 10; /* 1024*c/rtt */
+
+        /* calculate the "K" for (wmax-cwnd) = c/rtt * K^3
+         *  so K = cubic_root( (wmax-cwnd)*rtt/c )
+         * the unit of K is bictcp_HZ=2^10, not HZ
+         *
+         *  c = bic_scale >> 10
+         *  rtt = 100ms
+         *
+         * the following code has been designed and tested for
+         * cwnd < 1 million packets
+         * RTT < 100 seconds
+         * HZ < 1,000,00  (corresponding to 10 nano-second)
+         */
+
+        /* 1/c * 2^2*bictcp_HZ * srtt */
+        cube_factor = 1ull << (10+3*BICTCP_HZ); /* 2^40 */
+
+        /* divide by bic_scale and by constant Srtt (100ms) */
+        do_div(cube_factor, bic_scale * 10);
+
+        return tcp_register_congestion_control(&cubictcp);
+}
+
+static void __exit cubictcp_unregister(void)
+{
+        tcp_unregister_congestion_control(&cubictcp);
+}
+
+module_init(cubictcp_register);
+module_exit(cubictcp_unregister);
+
+MODULE_AUTHOR("Sangtae Ha, Stephen Hemminger");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("CUBIC TCP");
+MODULE_VERSION("2.0");