1 files changed, 231 insertions, 0 deletions

diff --git a/net/ipv4/tcp_veno.c b/net/ipv4/tcp_veno.c
new file mode 100644
index 000000000000..11b42a7135c1
--- /dev/null
+++ b/net/ipv4/tcp_veno.c
@@ -0,0 +1,231 @@
+/*
+ * TCP Veno congestion control
+ *
+ * This is based on the congestion detection/avoidance scheme described in
+ *    C. P. Fu, S. C. Liew.
+ *    "TCP Veno: TCP Enhancement for Transmission over Wireless Access Networks."
+ *    IEEE Journal on Selected Areas in Communication,
+ *    Feb. 2003.
+ *      See http://www.ntu.edu.sg/home5/ZHOU0022/papers/CPFu03a.pdf
+ */
+
+#include <linux/config.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/inet_diag.h>
+
+#include <net/tcp.h>
+
+/* Default values of the Veno variables, in fixed-point representation
+ * with V_PARAM_SHIFT bits to the right of the binary point.
+ */
+#define V_PARAM_SHIFT 1
+static const int beta = 3 << V_PARAM_SHIFT;
+
+/* Veno variables */
+struct veno {
+        u8 doing_veno_now;      /* if true, do veno for this rtt */
+        u16 cntrtt;             /* # of rtts measured within last rtt */
+        u32 minrtt;             /* min of rtts measured within last rtt (in usec) */
+        u32 basertt;            /* the min of all Veno rtt measurements seen (in usec) */
+        u32 inc;                /* decide whether to increase cwnd */
+        u32 diff;               /* calculate the diff rate */
+};
+
+/* There are several situations when we must "re-start" Veno:
+ *
+ *  o when a connection is established
+ *  o after an RTO
+ *  o after fast recovery
+ *  o when we send a packet and there is no outstanding
+ *    unacknowledged data (restarting an idle connection)
+ *
+ */
+static inline void veno_enable(struct sock *sk)
+{
+        struct veno *veno = inet_csk_ca(sk);
+
+        /* turn on Veno */
+        veno->doing_veno_now = 1;
+
+        veno->minrtt = 0x7fffffff;
+}
+
+static inline void veno_disable(struct sock *sk)
+{
+        struct veno *veno = inet_csk_ca(sk);
+
+        /* turn off Veno */
+        veno->doing_veno_now = 0;
+}
+
+static void tcp_veno_init(struct sock *sk)
+{
+        struct veno *veno = inet_csk_ca(sk);
+
+        veno->basertt = 0x7fffffff;
+        veno->inc = 1;
+        veno_enable(sk);
+}
+
+/* Do rtt sampling needed for Veno. */
+static void tcp_veno_rtt_calc(struct sock *sk, u32 usrtt)
+{
+        struct veno *veno = inet_csk_ca(sk);
+        u32 vrtt = usrtt + 1;   /* Never allow zero rtt or basertt */
+
+        /* Filter to find propagation delay: */
+        if (vrtt < veno->basertt)
+                veno->basertt = vrtt;
+
+        /* Find the min rtt during the last rtt to find
+         * the current prop. delay + queuing delay:
+         */
+        veno->minrtt = min(veno->minrtt, vrtt);
+        veno->cntrtt++;
+}
+
+static void tcp_veno_state(struct sock *sk, u8 ca_state)
+{
+        if (ca_state == TCP_CA_Open)
+                veno_enable(sk);
+        else
+                veno_disable(sk);
+}
+
+/*
+ * If the connection is idle and we are restarting,
+ * then we don't want to do any Veno calculations
+ * until we get fresh rtt samples.  So when we
+ * restart, we reset our Veno state to a clean
+ * state. After we get acks for this flight of
+ * packets, _then_ we can make Veno calculations
+ * again.
+ */
+static void tcp_veno_cwnd_event(struct sock *sk, enum tcp_ca_event event)
+{
+        if (event == CA_EVENT_CWND_RESTART || event == CA_EVENT_TX_START)
+                tcp_veno_init(sk);
+}
+
+static void tcp_veno_cong_avoid(struct sock *sk, u32 ack,
+                                u32 seq_rtt, u32 in_flight, int flag)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        struct veno *veno = inet_csk_ca(sk);
+
+        if (!veno->doing_veno_now)
+                return tcp_reno_cong_avoid(sk, ack, seq_rtt, in_flight, flag);
+
+        /* limited by applications */
+        if (!tcp_is_cwnd_limited(sk, in_flight))
+                return;
+
+        /* We do the Veno calculations only if we got enough rtt samples */
+        if (veno->cntrtt <= 2) {
+                /* We don't have enough rtt samples to do the Veno
+                 * calculation, so we'll behave like Reno.
+                 */
+                tcp_reno_cong_avoid(sk, ack, seq_rtt, in_flight, flag);
+        } else {
+                u32 rtt, target_cwnd;
+
+                /* We have enough rtt samples, so, using the Veno
+                 * algorithm, we determine the state of the network.
+                 */
+
+                rtt = veno->minrtt;
+
+                target_cwnd = ((tp->snd_cwnd * veno->basertt)
+                               << V_PARAM_SHIFT) / rtt;
+
+                veno->diff = (tp->snd_cwnd << V_PARAM_SHIFT) - target_cwnd;
+
+                if (tp->snd_cwnd <= tp->snd_ssthresh) {
+                        /* Slow start.  */
+                        tcp_slow_start(tp);
+                } else {
+                        /* Congestion avoidance. */
+                        if (veno->diff < beta) {
+                                /* In the "non-congestive state", increase cwnd
+                                 *  every rtt.
+                                 */
+                                if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
+                                        if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+                                                tp->snd_cwnd++;
+                                        tp->snd_cwnd_cnt = 0;
+                                } else
+                                        tp->snd_cwnd_cnt++;
+                        } else {
+                                /* In the "congestive state", increase cwnd
+                                 * every other rtt.
+                                 */
+                                if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
+                                        if (veno->inc
+                                            && tp->snd_cwnd <
+                                            tp->snd_cwnd_clamp) {
+                                                tp->snd_cwnd++;
+                                                veno->inc = 0;
+                                        } else
+                                                veno->inc = 1;
+                                        tp->snd_cwnd_cnt = 0;
+                                } else
+                                        tp->snd_cwnd_cnt++;
+                        }
+
+                }
+                if (tp->snd_cwnd < 2)
+                        tp->snd_cwnd = 2;
+                else if (tp->snd_cwnd > tp->snd_cwnd_clamp)
+                        tp->snd_cwnd = tp->snd_cwnd_clamp;
+        }
+        /* Wipe the slate clean for the next rtt. */
+        /* veno->cntrtt = 0; */
+        veno->minrtt = 0x7fffffff;
+}
+
+/* Veno MD phase */
+static u32 tcp_veno_ssthresh(struct sock *sk)
+{
+        const struct tcp_sock *tp = tcp_sk(sk);
+        struct veno *veno = inet_csk_ca(sk);
+
+        if (veno->diff < beta)
+                /* in "non-congestive state", cut cwnd by 1/5 */
+                return max(tp->snd_cwnd * 4 / 5, 2U);
+        else
+                /* in "congestive state", cut cwnd by 1/2 */
+                return max(tp->snd_cwnd >> 1U, 2U);
+}
+
+static struct tcp_congestion_ops tcp_veno = {
+        .init           = tcp_veno_init,
+        .ssthresh       = tcp_veno_ssthresh,
+        .cong_avoid     = tcp_veno_cong_avoid,
+        .rtt_sample     = tcp_veno_rtt_calc,
+        .set_state      = tcp_veno_state,
+        .cwnd_event     = tcp_veno_cwnd_event,
+
+        .owner          = THIS_MODULE,
+        .name           = "veno",
+};
+
+static int __init tcp_veno_register(void)
+{
+        BUG_ON(sizeof(struct veno) > ICSK_CA_PRIV_SIZE);
+        tcp_register_congestion_control(&tcp_veno);
+        return 0;
+}
+
+static void __exit tcp_veno_unregister(void)
+{
+        tcp_unregister_congestion_control(&tcp_veno);
+}
+
+module_init(tcp_veno_register);
+module_exit(tcp_veno_unregister);
+
+MODULE_AUTHOR("Bin Zhou, Cheng Peng Fu");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("TCP Veno");