[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>
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@ -40,6 +40,7 @@ struct westwood {
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u32 rtt;
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u32 rtt_min; /* minimum observed RTT */
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u8 first_ack; /* flag which infers that this is the first ack */
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u8 reset_rtt_min; /* Reset RTT min to next RTT sample*/
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};
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@ -67,6 +68,7 @@ static void tcp_westwood_init(struct sock *sk)
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w->bw_est = 0;
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w->accounted = 0;
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w->cumul_ack = 0;
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w->reset_rtt_min = 1;
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w->rtt_min = w->rtt = TCP_WESTWOOD_INIT_RTT;
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w->rtt_win_sx = tcp_time_stamp;
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w->snd_una = tcp_sk(sk)->snd_una;
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@ -142,6 +144,16 @@ static void westwood_update_window(struct sock *sk)
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}
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}
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static inline void update_rtt_min(struct westwood *w)
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{
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if (w->reset_rtt_min) {
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w->rtt_min = w->rtt;
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w->reset_rtt_min = 0;
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} else
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w->rtt_min = min(w->rtt, w->rtt_min);
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}
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/*
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* @westwood_fast_bw
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* It is called when we are in fast path. In particular it is called when
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@ -157,7 +169,7 @@ static inline void westwood_fast_bw(struct sock *sk)
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w->bk += tp->snd_una - w->snd_una;
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w->snd_una = tp->snd_una;
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w->rtt_min = min(w->rtt, w->rtt_min);
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update_rtt_min(w);
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}
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/*
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@ -226,12 +238,14 @@ static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event)
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case CA_EVENT_FRTO:
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tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk);
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/* Update RTT_min when next ack arrives */
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w->reset_rtt_min = 1;
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break;
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case CA_EVENT_SLOW_ACK:
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westwood_update_window(sk);
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w->bk += westwood_acked_count(sk);
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w->rtt_min = min(w->rtt, w->rtt_min);
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update_rtt_min(w);
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break;
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default:
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