[TCP] Westwood: reset RTT min after FRTO
RTT_min is updated each time a timeout event occurs
in order to cope with hard handovers in wireless scenarios such as UMTS.
Signed-off-by: Luca De Cicco <ldecicco@gmail.com>
Signed-off-by: Stephen Hemminger <shemminger@dxpl.pdx.osdl.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c
index edf2ee1..4247da1 100644
--- a/net/ipv4/tcp_westwood.c
+++ b/net/ipv4/tcp_westwood.c
@@ -40,6 +40,7 @@
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*/
};
@@ -67,6 +68,7 @@
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;
@@ -142,6 +144,16 @@
}
}
+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
@@ -157,7 +169,7 @@
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);
}
/*
@@ -226,12 +238,14 @@
case CA_EVENT_FRTO:
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: