From: Stephen Hemminger <shemminger@osdl.org>
Add TCP Westwood+ support back in as a separate pluggable algorithm. The
mechanism and policy is unchanged from existing code.
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/net/ipv4/Kconfig | 14 +
25-akpm/net/ipv4/Makefile | 1
25-akpm/net/ipv4/tcp_westwood.c | 349 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 364 insertions(+)
diff -puN net/ipv4/Kconfig~tcp-westwood-support net/ipv4/Kconfig
--- 25/net/ipv4/Kconfig~tcp-westwood-support 2005-03-18 23:40:47.000000000 -0800
+++ 25-akpm/net/ipv4/Kconfig 2005-03-18 23:40:47.000000000 -0800
@@ -424,6 +424,20 @@ config TCP_CONG_BIC
increase provides TCP friendliness.
See http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/
+config TCP_CONG_WESTWOOD
+ tristate "TCP Westwood+"
+ default y
+ ---help---
+ TCP Westwood+ is a sender-side only modification of the TCP Reno
+ protocol stack that optimizes the performance of TCP congestion
+ control. It is based on end-to-end bandwidth estimation to set
+ congestion window and slow start threshold after a congestion
+ episode. Using this estimation, TCP Westwood+ adaptively sets a
+ slow start threshold and a congestion window which takes into
+ account the bandwidth used at the time congestion is experienced.
+ TCP Westwood+ significantly increases fairness wrt TCP Reno in
+ wired networks and throughput over wireless links.
+
endmenu
source "net/ipv4/ipvs/Kconfig"
diff -puN net/ipv4/Makefile~tcp-westwood-support net/ipv4/Makefile
--- 25/net/ipv4/Makefile~tcp-westwood-support 2005-03-18 23:40:47.000000000 -0800
+++ 25-akpm/net/ipv4/Makefile 2005-03-18 23:40:47.000000000 -0800
@@ -29,6 +29,7 @@ obj-$(CONFIG_NETFILTER) += netfilter/
obj-$(CONFIG_IP_VS) += ipvs/
obj-$(CONFIG_IP_TCPDIAG) += tcp_diag.o
obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o
+obj-$(CONFIG_TCP_CONG_WESTWOOD) += tcp_westwood.o
obj-$(CONFIG_IP_ROUTE_MULTIPATH_CACHED) += multipath.o
obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
diff -puN /dev/null net/ipv4/tcp_westwood.c
--- /dev/null 2003-09-15 06:40:47.000000000 -0700
+++ 25-akpm/net/ipv4/tcp_westwood.c 2005-03-18 23:40:47.000000000 -0800
@@ -0,0 +1,349 @@
+/*
+ * TCP Westwood+
+ *
+ * Angelo Dell'Aera: TCP Westwood+ support
+ */
+
+#include <linux/config.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/tcp_diag.h>
+#include <net/tcp.h>
+
+/* TCP Westwood structure */
+struct westwood_ca {
+ u32 bw_ns_est; /* first bandwidth estimation..not too smoothed 8) */
+ u32 bw_est; /* bandwidth estimate */
+ u32 rtt_win_sx; /* here starts a new evaluation... */
+ u32 bk;
+ u32 snd_una; /* used for evaluating the number of acked bytes */
+ u32 cumul_ack;
+ u32 accounted;
+ u32 rtt;
+ u32 rtt_min; /* minimum observed RTT */
+};
+
+
+/* TCP Westwood functions and constants */
+#define TCP_WESTWOOD_INIT_RTT (20*HZ) /* maybe too conservative?! */
+#define TCP_WESTWOOD_RTT_MIN (HZ/20) /* 50ms */
+
+/*
+ * @tcp_westwood_create
+ * This function initializes fields used in TCP Westwood+. We can't
+ * get no information about RTTmin at this time so we simply set it to
+ * TCP_WESTWOOD_INIT_RTT. This value was chosen to be too conservative
+ * since in this way we're sure it will be updated in a consistent
+ * way as soon as possible. It will reasonably happen within the first
+ * RTT period of the connection lifetime.
+ */
+static void tcp_westwood_start(struct tcp_sock *tp)
+{
+ struct westwood_ca *w = tcp_ca(tp);
+
+ w->bw_ns_est = 0;
+ w->bw_est = 0;
+ w->accounted = 0;
+ w->cumul_ack = 0;
+ w->rtt_win_sx = tcp_time_stamp;
+ w->rtt = TCP_WESTWOOD_INIT_RTT;
+ w->rtt_min = TCP_WESTWOOD_INIT_RTT;
+ w->snd_una = tp->snd_una;
+}
+
+/*
+ * @westwood_do_filter
+ * Low-pass filter. Implemented using constant coefficents.
+ */
+static inline u32 westwood_do_filter(u32 a, u32 b)
+{
+ return (((7 * a) + b) >> 3);
+}
+
+static inline void westwood_filter(struct westwood_ca *w, u32 delta)
+{
+ w->bw_ns_est = westwood_do_filter(w->bw_ns_est, w->bk / delta);
+ w->bw_est = westwood_do_filter(w->bw_est, w->bw_ns_est);
+}
+
+/*
+ * @westwood_update_rttmin
+ * It is used to update RTTmin. In this case we MUST NOT use
+ * WESTWOOD_RTT_MIN minimum bound since we could be on a LAN!
+ */
+static inline u32 westwood_update_rttmin(const struct westwood_ca *w)
+{
+ u32 rttmin = w->rtt_min;
+
+ if (w->rtt != 0 &&
+ (w->rtt < w->rtt_min || !rttmin))
+ rttmin = w->rtt;
+
+ return rttmin;
+}
+
+static void tcp_westwood_sample_rtt(struct tcp_sock *tp, u32 rtt)
+{
+ struct westwood_ca *w = tcp_ca(tp);
+ w->rtt = tp->srtt >> 3;
+}
+
+/*
+ * @westwood_acked
+ * Evaluate increases for dk.
+ */
+static inline u32 westwood_acked(struct tcp_sock *tp)
+{
+ struct westwood_ca *w = tcp_ca(tp);
+ return tp->snd_una - w->snd_una;
+}
+
+/*
+ * @westwood_new_window
+ * It evaluates if we are receiving data inside the same RTT window as
+ * when we started.
+ * Return value:
+ * It returns 0 if we are still evaluating samples in the same RTT
+ * window, 1 if the sample has to be considered in the next window.
+ */
+static inline int westwood_new_window(const struct tcp_sock *tp)
+{
+ struct westwood_ca *w = tcp_ca(tp);
+ u32 left_bound;
+ u32 rtt;
+ int ret = 0;
+
+ left_bound = w->rtt_win_sx;
+ rtt = max(w->rtt, (u32) TCP_WESTWOOD_RTT_MIN);
+
+ /*
+ * A RTT-window has passed. Be careful since if RTT is less than
+ * 50ms we don't filter but we continue 'building the sample'.
+ * This minimum limit was choosen since an estimation on small
+ * time intervals is better to avoid...
+ * Obvioulsy on a LAN we reasonably will always have
+ * right_bound = left_bound + WESTWOOD_RTT_MIN
+ */
+
+ if ((left_bound + rtt) < tcp_time_stamp)
+ ret = 1;
+
+ return ret;
+}
+
+/*
+ * @westwood_update_window
+ * It updates RTT evaluation window if it is the right moment to do
+ * it. If so it calls filter for evaluating bandwidth.
+ */
+static void westwood_update_window(struct tcp_sock *tp, u32 now)
+{
+ struct westwood_ca *w = tcp_ca(tp);
+ if (westwood_new_window(tp)) {
+ u32 delta = now - w->rtt_win_sx;
+
+ if (delta) {
+ if (w->rtt)
+ westwood_filter(w, delta);
+
+ w->bk = 0;
+ w->rtt_win_sx = tcp_time_stamp;
+ }
+ }
+}
+
+/*
+ * @tcp_westwood_fast_bw
+ * It is called when we are in fast path. In particular it is called when
+ * header prediction is successfull. In such case infact update is
+ * straight forward and doesn't need any particular care.
+ */
+static void tcp_westwood_fast_bw(struct tcp_sock *tp)
+{
+ struct westwood_ca *w = tcp_ca(tp);
+ westwood_update_window(tp, tcp_time_stamp);
+
+ w->bk += westwood_acked(tp);
+ w->snd_una = tp->snd_una;
+ w->rtt_min = westwood_update_rttmin(w);
+}
+
+/*
+ * @westwood_acked_count
+ * This function evaluates cumul_ack for evaluating dk in case of
+ * delayed or partial acks.
+ */
+static u32 westwood_acked_count(struct tcp_sock *tp)
+{
+ struct westwood_ca *w = tcp_ca(tp);
+
+ w->cumul_ack = westwood_acked(tp);
+
+ /* If cumul_ack is 0 this is a dupack since it's not moving
+ * tp->snd_una.
+ */
+ if (!w->cumul_ack) {
+ w->accounted += tp->mss_cache_std;
+ w->cumul_ack = tp->mss_cache_std;
+ }
+
+ if (w->cumul_ack > tp->mss_cache_std) {
+ /* Partial or delayed ack */
+ if (w->accounted >= w->cumul_ack) {
+ w->accounted -= w->cumul_ack;
+ w->cumul_ack = tp->mss_cache_std;
+ } else {
+ w->cumul_ack -= w->accounted;
+ w->accounted = 0;
+ }
+ }
+
+ w->snd_una = tp->snd_una;
+
+ return w->cumul_ack;
+}
+
+
+/*
+ * @tcp_westwood_slow_bw
+ * It is called when something is going wrong..even if there could
+ * be no problems! Infact a simple delayed packet may trigger a
+ * dupack. But we need to be careful in such case.
+ */
+static void tcp_westwood_slow_bw(struct tcp_sock *tp)
+{
+ struct westwood_ca *w = tcp_ca(tp);
+
+ westwood_update_window(tp, tcp_time_stamp);
+
+ w->bk += westwood_acked_count(tp);
+ w->rtt_min = westwood_update_rttmin(w);
+}
+
+static inline u32 tcp_westwood_bw_rttmin(const struct tcp_sock *tp)
+{
+ struct westwood_ca *w = tcp_ca(tp);
+
+ return max((w->bw_est) * (w->rtt_min) / (u32) (tp->mss_cache_std),
+ 2U);
+}
+
+static inline u32 tcp_westwood_ssthresh(struct tcp_sock *tp)
+{
+ u32 ssthresh = tcp_westwood_bw_rttmin(tp);
+ if (ssthresh)
+ tp->snd_ssthresh = ssthresh;
+
+ return (ssthresh != 0);
+}
+
+static inline int tcp_westwood_cwnd(struct tcp_sock *tp)
+{
+ u32 cwnd = 0;
+
+ cwnd = tcp_westwood_bw_rttmin(tp);
+ if (cwnd)
+ tp->snd_cwnd = cwnd;
+
+ return (cwnd != 0);
+}
+
+/*
+ * TCP Westwood
+ * Here limit is evaluated as BWestimation*RTTmin (for obtaining it
+ * in packets we use mss_cache). If sysctl_tcp_westwood is off
+ * tcp_westwood_bw_rttmin() returns 0. In such case snd_ssthresh is
+ * still used as usual. It prevents other strange cases in which
+ * BWE*RTTmin could assume value 0. It should not happen but...
+ */
+static u32 tcp_westwood_cwnd_min(struct tcp_sock *tp)
+{
+ u32 limit;
+
+ limit = tcp_westwood_bw_rttmin(tp);
+ if (limit == 0)
+ limit = tp->snd_ssthresh/2;
+ return limit;
+}
+
+static void tcp_westwood_event(struct tcp_sock *tp, enum tcp_ca_event event)
+{
+ switch(event) {
+ case CA_EVENT_CWND_RESTART:
+ break;
+
+ case CA_EVENT_COMPLETE_CWR:
+ if (tcp_westwood_cwnd(tp))
+ tp->snd_ssthresh = tp->snd_cwnd;
+ break;
+
+ case CA_EVENT_FRTO:
+ if (!tcp_westwood_ssthresh(tp))
+ tp->snd_ssthresh = tcp_westwood_ssthresh(tp);
+ break;
+
+ case CA_EVENT_FAST_ACK:
+ tcp_westwood_fast_bw(tp);
+ break;
+
+ case CA_EVENT_SLOW_ACK:
+ tcp_westwood_slow_bw(tp);
+ break;
+
+ default:
+ break;
+ }
+}
+
+
+/* Extract info for Tcp socket info provided via netlink. */
+static void tcp_westwood_info(struct tcp_sock *tp, u32 ext,
+ struct sk_buff *skb)
+{
+
+ if (ext & (1<<(TCPDIAG_VEGASINFO-1))) {
+ struct tcpvegas_info *info
+ = tcpdiag_put(skb, TCPDIAG_VEGASINFO, sizeof(*info));
+ if (info) {
+ struct westwood_ca *ca = tcp_ca(tp);
+ info->tcpv_enabled = 1;
+ info->tcpv_rttcnt = 0;
+ info->tcpv_rtt = jiffies_to_usecs(ca->rtt);
+ info->tcpv_minrtt = jiffies_to_usecs(ca->rtt_min);
+ }
+ }
+}
+
+
+static struct tcp_ca_type tcp_westwood = {
+ .start = tcp_westwood_start,
+ .ssthresh = tcp_reno_ssthresh,
+ .rtt_sample = tcp_westwood_sample_rtt,
+ .cong_avoid = tcp_reno_cong_avoid,
+ .min_cwnd = tcp_westwood_cwnd_min,
+ .cwnd_event = tcp_westwood_event,
+ .get_info = tcp_westwood_info,
+
+ .owner = THIS_MODULE,
+ .name = "westwood"
+};
+
+static int __init tcp_westwood_init(void)
+{
+ BUG_ON(sizeof(struct westwood_ca) > TCP_CA_PRIV_SIZE);
+ tcp_ca_register(&tcp_westwood);
+ return 0;
+}
+
+static void __exit tcp_westwood_exit(void)
+{
+ tcp_ca_unregister(&tcp_westwood);
+}
+
+module_init(tcp_westwood_init);
+module_exit(tcp_westwood_exit);
+
+MODULE_AUTHOR("Stephen Hemminger, Angelo Del'Aera");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("TCP Westwood+");
_