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Commit bc726a71 authored by Luca De Cicco's avatar Luca De Cicco Committed by David S. Miller
Browse files

[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: default avatarLuca De Cicco <ldecicco@gmail.com>
Signed-off-by: default avatarStephen Hemminger <shemminger@dxpl.pdx.osdl.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b3a92eab

net/ipv4/tcp_westwood.c

+16 −2
Original line number Diff line number Diff line
@@ -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: