netdev - Re: [PATCH net-next 15/15] tcp: switch TCP TS option (RFC 7323) to 1ms clock

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Date:   Thu, 18 May 2017 05:33:45 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Neal Cardwell <ncardwell@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Wei Wang <weiwan@...gle.com>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 15/15] tcp: switch TCP TS option (RFC 7323) to
 1ms clock

On Tue, 2017-05-16 at 14:00 -0700, Eric Dumazet wrote:
> TCP Timestamps option is defined in RFC 7323
> 
> Traditionally on linux, it has been tied to the internal
> 'jiffies' variable, because it had been a cheap and good enough
> generator.

...

> @@ -3003,7 +3004,7 @@ void tcp_rearm_rto(struct sock *sk)
>  			struct sk_buff *skb = tcp_write_queue_head(sk);
>  			const u32 rto_time_stamp =
>  				tcp_skb_timestamp(skb) + rto;
> -			s32 delta = (s32)(rto_time_stamp - tcp_time_stamp);
> +			s32 delta = (s32)(rto_time_stamp - tcp_jiffies32);
>  			/* delta may not be positive if the socket is locked
>  			 * when the retrans timer fires and is rescheduled.
>  			 */

RTO is broken, I will send a fix after tests.