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[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>
This commit is contained in:
Luca De Cicco 2006-06-11 23:02:19 -07:00 committed by David S. Miller
parent b3a92eabe5
commit bc726a71d2
1 changed files with 16 additions and 2 deletions
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18
net/ipv4/tcp_westwood.c
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@ -40,6 +40,7 @@ struct westwood {
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 @@ static void tcp_westwood_init(struct sock *sk)
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 void westwood_update_window(struct sock *sk)
}
}
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 @@ static inline void westwood_fast_bw(struct sock *sk)
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 @@ static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event)
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: