[TCP] YeAH-TCP: algorithm implementation

YeAH-TCP is a sender-side high-speed enabled TCP congestion control
algorithm, which uses a mixed loss/delay approach to compute the
congestion window. It's design goals target high efficiency, internal,
RTT and Reno fairness, resilience to link loss while keeping network
elements load as low as possible.

For further details look here:
    http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf

Signed-off-by: Angelo P. Castellani <angelo.castellani@gmail.con>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 134 insertions, 0 deletions

diff --git a/net/ipv4/tcp_yeah.h b/net/ipv4/tcp_yeah.h
new file mode 100644
index 000000000000..b3255dba4e2d
--- /dev/null
+++ b/net/ipv4/tcp_yeah.h
@@ -0,0 +1,134 @@
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/inet_diag.h>
+
+#include <net/tcp.h>
+
+/* Vegas variables */
+struct vegas {
+        u32     beg_snd_nxt;    /* right edge during last RTT */
+        u32     beg_snd_una;    /* left edge  during last RTT */
+        u32     beg_snd_cwnd;   /* saves the size of the cwnd */
+        u8      doing_vegas_now;/* if true, do vegas 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 Vegas RTT measurements seen (in usec) */
+};
+
+/* There are several situations when we must "re-start" Vegas:
+ *
+ *  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)
+ *
+ * In these circumstances we cannot do a Vegas calculation at the
+ * end of the first RTT, because any calculation we do is using
+ * stale info -- both the saved cwnd and congestion feedback are
+ * stale.
+ *
+ * Instead we must wait until the completion of an RTT during
+ * which we actually receive ACKs.
+ */
+static inline void vegas_enable(struct sock *sk)
+{
+        const struct tcp_sock *tp = tcp_sk(sk);
+        struct vegas *vegas = inet_csk_ca(sk);
+
+        /* Begin taking Vegas samples next time we send something. */
+        vegas->doing_vegas_now = 1;
+
+        /* Set the beginning of the next send window. */
+        vegas->beg_snd_nxt = tp->snd_nxt;
+
+        vegas->cntRTT = 0;
+        vegas->minRTT = 0x7fffffff;
+}
+
+/* Stop taking Vegas samples for now. */
+static inline void vegas_disable(struct sock *sk)
+{
+        struct vegas *vegas = inet_csk_ca(sk);
+
+        vegas->doing_vegas_now = 0;
+}
+
+static void tcp_vegas_init(struct sock *sk)
+{
+        struct vegas *vegas = inet_csk_ca(sk);
+
+        vegas->baseRTT = 0x7fffffff;
+        vegas_enable(sk);
+}
+
+static void tcp_vegas_state(struct sock *sk, u8 ca_state)
+{
+
+        if (ca_state == TCP_CA_Open)
+                vegas_enable(sk);
+        else
+                vegas_disable(sk);
+}
+
+/* Do RTT sampling needed for Vegas.
+ * Basically we:
+ *   o min-filter RTT samples from within an RTT to get the current
+ *     propagation delay + queuing delay (we are min-filtering to try to
+ *     avoid the effects of delayed ACKs)
+ *   o min-filter RTT samples from a much longer window (forever for now)
+ *     to find the propagation delay (baseRTT)
+ */
+static void tcp_vegas_rtt_calc(struct sock *sk, u32 usrtt)
+{
+        struct vegas *vegas = inet_csk_ca(sk);
+        u32 vrtt = usrtt + 1; /* Never allow zero rtt or baseRTT */
+
+        /* Filter to find propagation delay: */
+        if (vrtt < vegas->baseRTT)
+                vegas->baseRTT = vrtt;
+
+        /* Find the min RTT during the last RTT to find
+         * the current prop. delay + queuing delay:
+         */
+        vegas->minRTT = min(vegas->minRTT, vrtt);
+        vegas->cntRTT++;
+}
+
+/*
+ * If the connection is idle and we are restarting,
+ * then we don't want to do any Vegas calculations
+ * until we get fresh RTT samples.  So when we
+ * restart, we reset our Vegas state to a clean
+ * slate. After we get acks for this flight of
+ * packets, _then_ we can make Vegas calculations
+ * again.
+ */
+static void tcp_vegas_cwnd_event(struct sock *sk, enum tcp_ca_event event)
+{
+        if (event == CA_EVENT_CWND_RESTART ||
+            event == CA_EVENT_TX_START)
+                tcp_vegas_init(sk);
+}
+
+/* Extract info for Tcp socket info provided via netlink. */
+static void tcp_vegas_get_info(struct sock *sk, u32 ext,
+                               struct sk_buff *skb)
+{
+        const struct vegas *ca = inet_csk_ca(sk);
+        if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
+                struct tcpvegas_info *info;
+
+                info = RTA_DATA(__RTA_PUT(skb, INET_DIAG_VEGASINFO,
+                                          sizeof(*info)));
+
+                info->tcpv_enabled = ca->doing_vegas_now;
+                info->tcpv_rttcnt = ca->cntRTT;
+                info->tcpv_rtt = ca->baseRTT;
+                info->tcpv_minrtt = ca->minRTT;
+        rtattr_failure: ;
+        }
+}
+
+