Re: [PATCH 8/8] tcp: Skip redundant ACK on partial sendmsg() failure

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Dec 04, 2025 at 08:45:41AM +0100, Stefano Brivio wrote:
> ...we'll send a duplicate ACK right away in this case, and this
> redundant, earlier check is not just useless, but it might actually
> be harmful as we'll now send a triple ACK which might cause two
> retransmissions.
> 
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  tcp.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/tcp.c b/tcp.c
> index 76a9daf..fc986a2 100644
> --- a/tcp.c
> +++ b/tcp.c
> @@ -1972,13 +1972,10 @@ eintr:
>  		return -1;
>  	}
>  
> -	if (n < (int)(seq_from_tap - conn->seq_from_tap)) {
> +	if (n < (int)(seq_from_tap - conn->seq_from_tap))
>  		partial_send = 1;
> -		conn->seq_from_tap += n;
> -		tcp_send_flag(c, conn, ACK_IF_NEEDED);
> -	} else {
> -		conn->seq_from_tap += n;
> -	}
> +
> +	conn->seq_from_tap += n;
>  
>  out:
>  	if (keep != -1 || partial_send) {
> -- 
> 2.43.0
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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