Re: [net-next, 3/3] tcp: convert icsk_user_timeout from jiffies to msecs

From: Eric Dumazet
Date: Mon Jul 16 2018 - 12:00:14 EST




On 07/12/2018 05:49 PM, Jon Maxwell wrote:
> The final patch in this series. 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: Jon Maxwell <jmaxwell37@xxxxxxxxx>
> ---
> net/ipv4/tcp_timer.c | 19 ++++++++++++++++++-
> 1 file changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
> index 8ab8c9645294..d4d4b30a6bec 100644
> --- a/net/ipv4/tcp_timer.c
> +++ b/net/ipv4/tcp_timer.c
> @@ -36,6 +36,22 @@ 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));

if (elapsed >= icsk->icsk_user_timeout)
return 1; /* user timeout has passed; fire ASAP */

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

Thanks !