netdev - Re: [PATCH] TCP: avoid to send keepalive probes if it is receiving data

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Date:	Sun, 18 Apr 2010 11:06:00 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Flavio Leitner <fleitner@...hat.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] TCP: avoid to send keepalive probes if it is receiving
 data

Le samedi 17 avril 2010 à 14:28 -0300, Flavio Leitner a écrit :
> RFC 1122 says the following:
> ...
>   Keep-alive packets MUST only be sent when no data or
>   acknowledgement packets have been received for the
>   connection within an interval.
> ...
> 
> Fix this by storing the timestamp of last received data
> packet and checking for it when the keepalive timer expires.
> 
> Signed-off-by: Flavio Leitner <fleitner@...hat.com>

Thanks Flavio !

Shouldnt you also change do_tcp_setsockopt() TCP_KEEPIDLE for
consistency ?

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 0f8caf6..a4048d7 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2298,7 +2298,10 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
 			if (sock_flag(sk, SOCK_KEEPOPEN) &&
 			    !((1 << sk->sk_state) &
 			      (TCPF_CLOSE | TCPF_LISTEN))) {
-				__u32 elapsed = tcp_time_stamp - tp->rcv_tstamp;
+				u32 elapsed = min_t(u32,
+						      tcp_time_stamp - tp->rcv_tstamp,
+						      tcp_time_stamp - tp->lrcvtime);
+
 				if (tp->keepalive_time > elapsed)
 					elapsed = tp->keepalive_time - elapsed;
 				else






> ---
>  include/linux/tcp.h  |    1 +
>  net/ipv4/tcp_input.c |    3 +++
>  net/ipv4/tcp_timer.c |    8 ++++++++
>  3 files changed, 12 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/tcp.h b/include/linux/tcp.h
> index a778ee0..405678f 100644
> --- a/include/linux/tcp.h
> +++ b/include/linux/tcp.h
> @@ -314,6 +314,7 @@ struct tcp_sock {
>   	u32	snd_sml;	/* Last byte of the most recently transmitted small packet */
>  	u32	rcv_tstamp;	/* timestamp of last received ACK (for keepalives) */
>  	u32	lsndtime;	/* timestamp of last sent data packet (for restart window) */
> +	u32	lrcvtime;	/* timestamp of last received data packet (for keepalives) */
>  
>  	/* Data for direct copy to user */
>  	struct {
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index f240f57..60d2980 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -5391,6 +5391,8 @@ no_ack:
>  				__kfree_skb(skb);
>  			else
>  				sk->sk_data_ready(sk, 0);
> +
> +			tp->lrcvtime = tcp_time_stamp;
>  			return 0;
>  		}
>  	}
> @@ -5421,6 +5423,7 @@ step5:
>  
>  	tcp_data_snd_check(sk);
>  	tcp_ack_snd_check(sk);
> +	tp->lrcvtime = tcp_time_stamp;
>  	return 0;
>  
>  csum_error:
> diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
> index 8a0ab29..74dd804 100644
> --- a/net/ipv4/tcp_timer.c
> +++ b/net/ipv4/tcp_timer.c
> @@ -554,6 +554,14 @@ static void tcp_keepalive_timer (unsigned long data)
>  	if (tp->packets_out || tcp_send_head(sk))
>  		goto resched;
>  
> +	elapsed = tcp_time_stamp - tp->lrcvtime;
> +	
> +	/* receiving data means alive */
> +	if (elapsed < keepalive_time_when(tp)) {
> +		elapsed = keepalive_time_when(tp) - elapsed;
> +		goto resched;
> +	}
> +
>  	elapsed = tcp_time_stamp - tp->rcv_tstamp;
>  
>  	if (elapsed >= keepalive_time_when(tp)) {


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