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Commit 5eb4f3dc authored by Yuchung Cheng's avatar Yuchung Cheng Committed by Kaustubh Pandey
Browse files

tcp: create a helper to model exponential backoff 



Create a helper to model TCP exponential backoff for the next patch.
This is pure refactor w no behavior change.

Change-Id: I2a95973a9d906b91e4c6adb483dd280d2c66ed65
Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarNeal Cardwell <ncardwell@google.com>
Reviewed-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Git-Commit: 01a523b071618abbc634d1958229fe3bd2dfa5fa
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: default avatarKaustubh Pandey <kapandey@codeaurora.org>
parent 2aa81b16

net/ipv4/tcp_timer.c

+18 −13
Original line number Diff line number Diff line
@@ -192,7 +192,20 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) 
	tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);

}



static unsigned int tcp_model_timeout(struct sock *sk,

				      unsigned int boundary,

				      unsigned int rto_base)

{

	unsigned int linear_backoff_thresh, timeout;



	linear_backoff_thresh = ilog2(TCP_RTO_MAX / rto_base);

	if (boundary <= linear_backoff_thresh)

		timeout = ((2 << boundary) - 1) * rto_base;

	else

		timeout = ((2 << linear_backoff_thresh) - 1) * rto_base +

			(boundary - linear_backoff_thresh) * TCP_RTO_MAX;

	return jiffies_to_msecs(timeout);

}

/**

 *  retransmits_timed_out() - returns true if this connection has timed out

 *  @sk:       The current socket
@@ -210,23 +223,15 @@ static bool retransmits_timed_out(struct sock *sk, 
				  unsigned int boundary,

				  unsigned int timeout)

{

	const unsigned int rto_base = TCP_RTO_MIN;

	unsigned int linear_backoff_thresh, start_ts;

	unsigned int start_ts;



	if (!inet_csk(sk)->icsk_retransmits)

		return false;



	start_ts = tcp_sk(sk)->retrans_stamp;

	if (likely(timeout == 0)) {

		linear_backoff_thresh = ilog2(TCP_RTO_MAX/rto_base);

	if (likely(timeout == 0))

		timeout = tcp_model_timeout(sk, boundary, TCP_RTO_MIN);



		if (boundary <= linear_backoff_thresh)

			timeout = ((2 << boundary) - 1) * rto_base;

		else

			timeout = ((2 << linear_backoff_thresh) - 1) * rto_base +

				(boundary - linear_backoff_thresh) * TCP_RTO_MAX;

		timeout = jiffies_to_msecs(timeout);

	}

	return (s32)(tcp_time_stamp(tcp_sk(sk)) - start_ts - timeout) >= 0;

}