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Commit b701a99e authored by Jon Maxwell's avatar Jon Maxwell Committed by David S. Miller
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tcp: Add tcp_clamp_rto_to_user_timeout() helper to improve accuracy 



Create the tcp_clamp_rto_to_user_timeout() helper routine. To calculate
the correct rto, so that the TCP_USER_TIMEOUT socket option is more
accurate. Taking suggestions and feedback into account from
Eric Dumazet, Neal Cardwell and David Laight. Due to the 1st commit we
can avoid the msecs_to_jiffies() and jiffies_to_msecs() dance.

Signed-off-by: default avatarJon Maxwell <jmaxwell37@gmail.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a7fa3770

net/ipv4/tcp_timer.c

+17 −1
Original line number Diff line number Diff line
@@ -36,6 +36,21 @@ u32 tcp_retransmit_stamp(const struct sock *sk) 
	return start_ts;

}



static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk)

{

	struct inet_connection_sock *icsk = inet_csk(sk);

	u32 elapsed, start_ts;



	start_ts = tcp_retransmit_stamp(sk);

	if (!icsk->icsk_user_timeout || !start_ts)

		return icsk->icsk_rto;

	elapsed = tcp_time_stamp(tcp_sk(sk)) - start_ts;

	if (elapsed >= icsk->icsk_user_timeout)

		return 1; /* user timeout has passed; fire ASAP */

	else

		return min_t(u32, icsk->icsk_rto, msecs_to_jiffies(icsk->icsk_user_timeout - elapsed));

}



/**

 *  tcp_write_err() - close socket and save error info

 *  @sk:  The socket the error has appeared on.
@@ -544,7 +559,8 @@ void tcp_retransmit_timer(struct sock *sk) 
		/* Use normal (exponential) backoff */

		icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);

	}

	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);

	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,

				  tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX);

	if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1 + 1, 0))

		__sk_dst_reset(sk);