/*
- * TCP Westwood+
+ * TCP Westwood+: end-to-end bandwidth estimation for TCP
*
- * Angelo Dell'Aera: TCP Westwood+ support
+ * Angelo Dell'Aera: author of the first version of TCP Westwood+ in Linux 2.4
+ *
+ * Support at http://c3lab.poliba.it/index.php/Westwood
+ * Main references in literature:
+ *
+ * - Mascolo S, Casetti, M. Gerla et al.
+ * "TCP Westwood: bandwidth estimation for TCP" Proc. ACM Mobicom 2001
+ *
+ * - A. Grieco, s. Mascolo
+ * "Performance evaluation of New Reno, Vegas, Westwood+ TCP" ACM Computer
+ * Comm. Review, 2004
+ *
+ * - A. Dell'Aera, L. Grieco, S. Mascolo.
+ * "Linux 2.4 Implementation of Westwood+ TCP with Rate-Halving :
+ * A Performance Evaluation Over the Internet" (ICC 2004), Paris, June 2004
+ *
+ * Westwood+ employs end-to-end bandwidth measurement to set cwnd and
+ * ssthresh after packet loss. The probing phase is as the original Reno.
*/
-#include <linux/config.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/skbuff.h>
-#include <linux/tcp_diag.h>
+#include <linux/inet_diag.h>
#include <net/tcp.h>
/* TCP Westwood structure */
u32 accounted;
u32 rtt;
u32 rtt_min; /* minimum observed RTT */
+ u8 first_ack; /* flag which infers that this is the first ack */
+ u8 reset_rtt_min; /* Reset RTT min to next RTT sample*/
};
struct westwood *w = inet_csk_ca(sk);
w->bk = 0;
- w->bw_ns_est = 0;
- w->bw_est = 0;
- w->accounted = 0;
- w->cumul_ack = 0;
+ w->bw_ns_est = 0;
+ w->bw_est = 0;
+ w->accounted = 0;
+ w->cumul_ack = 0;
+ w->reset_rtt_min = 1;
w->rtt_min = w->rtt = TCP_WESTWOOD_INIT_RTT;
w->rtt_win_sx = tcp_time_stamp;
w->snd_una = tcp_sk(sk)->snd_una;
+ w->first_ack = 1;
}
/*
return (((7 * a) + b) >> 3);
}
-static inline void westwood_filter(struct westwood *w, u32 delta)
+static void westwood_filter(struct westwood *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);
+ /* If the filter is empty fill it with the first sample of bandwidth */
+ if (w->bw_ns_est == 0 && w->bw_est == 0) {
+ w->bw_ns_est = w->bk / delta;
+ w->bw_est = w->bw_ns_est;
+ } else {
+ 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);
+ }
}
/*
* Called after processing group of packets.
* but all westwood needs is the last sample of srtt.
*/
-static void tcp_westwood_pkts_acked(struct sock *sk, u32 cnt)
+static void tcp_westwood_pkts_acked(struct sock *sk, u32 cnt, s32 rtt)
{
struct westwood *w = inet_csk_ca(sk);
- if (cnt > 0)
- w->rtt = tcp_sk(sk)->srtt >> 3;
+
+ if (rtt > 0)
+ w->rtt = usecs_to_jiffies(rtt);
}
/*
struct westwood *w = inet_csk_ca(sk);
s32 delta = tcp_time_stamp - w->rtt_win_sx;
+ /* Initialize w->snd_una with the first acked sequence number in order
+ * to fix mismatch between tp->snd_una and w->snd_una for the first
+ * bandwidth sample
+ */
+ if (w->first_ack) {
+ w->snd_una = tcp_sk(sk)->snd_una;
+ w->first_ack = 0;
+ }
+
/*
* See if a RTT-window has passed.
* Be careful since if RTT is less than
}
}
+static inline void update_rtt_min(struct westwood *w)
+{
+ if (w->reset_rtt_min) {
+ w->rtt_min = w->rtt;
+ w->reset_rtt_min = 0;
+ } else
+ w->rtt_min = min(w->rtt, w->rtt_min);
+}
+
+
/*
* @westwood_fast_bw
* It is called when we are in fast path. In particular it is called when
w->bk += tp->snd_una - w->snd_una;
w->snd_una = tp->snd_una;
- w->rtt_min = min(w->rtt, w->rtt_min);
+ update_rtt_min(w);
}
/*
w->cumul_ack = tp->snd_una - w->snd_una;
- /* If cumul_ack is 0 this is a dupack since it's not moving
- * tp->snd_una.
- */
- if (!w->cumul_ack) {
+ /* 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;
w->cumul_ack = tp->mss_cache;
}
- if (w->cumul_ack > tp->mss_cache) {
+ if (w->cumul_ack > tp->mss_cache) {
/* Partial or delayed ack */
if (w->accounted >= w->cumul_ack) {
w->accounted -= w->cumul_ack;
return w->cumul_ack;
}
-static inline u32 westwood_bw_rttmin(const struct sock *sk)
-{
- const struct tcp_sock *tp = tcp_sk(sk);
- const struct westwood *w = inet_csk_ca(sk);
- return max_t(u32, (w->bw_est * w->rtt_min) / tp->mss_cache, 2);
-}
/*
* TCP Westwood
* in packets we use mss_cache). Rttmin is guaranteed to be >= 2
* so avoids ever returning 0.
*/
-static u32 tcp_westwood_cwnd_min(struct sock *sk)
+static u32 tcp_westwood_bw_rttmin(const struct sock *sk)
{
- return westwood_bw_rttmin(sk);
+ const struct tcp_sock *tp = tcp_sk(sk);
+ const struct westwood *w = inet_csk_ca(sk);
+ return max_t(u32, (w->bw_est * w->rtt_min) / tp->mss_cache, 2);
}
static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event)
struct tcp_sock *tp = tcp_sk(sk);
struct westwood *w = inet_csk_ca(sk);
- switch(event) {
+ switch (event) {
case CA_EVENT_FAST_ACK:
westwood_fast_bw(sk);
break;
case CA_EVENT_COMPLETE_CWR:
- tp->snd_cwnd = tp->snd_ssthresh = westwood_bw_rttmin(sk);
+ tp->snd_cwnd = tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk);
break;
case CA_EVENT_FRTO:
- tp->snd_ssthresh = westwood_bw_rttmin(sk);
+ tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk);
+ /* Update RTT_min when next ack arrives */
+ w->reset_rtt_min = 1;
break;
case CA_EVENT_SLOW_ACK:
westwood_update_window(sk);
w->bk += westwood_acked_count(sk);
- w->rtt_min = min(w->rtt, w->rtt_min);
+ update_rtt_min(w);
break;
default:
struct sk_buff *skb)
{
const struct westwood *ca = inet_csk_ca(sk);
- if (ext & (1<<(TCPDIAG_VEGASINFO-1))) {
- struct rtattr *rta;
- struct tcpvegas_info *info;
-
- rta = __RTA_PUT(skb, TCPDIAG_VEGASINFO, sizeof(*info));
- info = RTA_DATA(rta);
- 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);
- rtattr_failure: ;
+ if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
+ struct tcpvegas_info info = {
+ .tcpv_enabled = 1,
+ .tcpv_rtt = jiffies_to_usecs(ca->rtt),
+ .tcpv_minrtt = jiffies_to_usecs(ca->rtt_min),
+ };
+
+ nla_put(skb, INET_DIAG_VEGASINFO, sizeof(info), &info);
}
}
.init = tcp_westwood_init,
.ssthresh = tcp_reno_ssthresh,
.cong_avoid = tcp_reno_cong_avoid,
- .min_cwnd = tcp_westwood_cwnd_min,
+ .min_cwnd = tcp_westwood_bw_rttmin,
.cwnd_event = tcp_westwood_event,
.get_info = tcp_westwood_info,
.pkts_acked = tcp_westwood_pkts_acked,
static int __init tcp_westwood_register(void)
{
- BUG_ON(sizeof(struct westwood) > ICSK_CA_PRIV_SIZE);
+ BUILD_BUG_ON(sizeof(struct westwood) > ICSK_CA_PRIV_SIZE);
return tcp_register_congestion_control(&tcp_westwood);
}
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff