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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.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yuchung Cheng 2019-01-16 15:05:32 -08:00 committed by David S. Miller
parent c7d13c8faa
commit 01a523b071
1 changed files with 16 additions and 11 deletions
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27
net/ipv4/tcp_timer.c
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@ -159,7 +159,20 @@ 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
@ -177,23 +190,15 @@ 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;
}