Re: [PATCH 7/8] tcp: Send a duplicate ACK also on complete sendmsg() failure

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

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On Thu, Dec 04, 2025 at 08:45:40AM +0100, Stefano Brivio wrote:
> ...in order to trigger a fast retransmit as soon as possible. There's
> no benefit in forcing the sender to wait for a longer time than that.
> 
> We already do this on partial failures (short socket writes), but for
> historical reason not on complete failures. Make these two cases
> consistent between each other.
> 
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

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

> ---
>  tcp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tcp.c b/tcp.c
> index 454df69..76a9daf 100644
> --- a/tcp.c
> +++ b/tcp.c
> @@ -1965,7 +1965,7 @@ eintr:
>  			goto eintr;
>  
>  		if (errno == EAGAIN || errno == EWOULDBLOCK) {
> -			tcp_send_flag(c, conn, ACK_IF_NEEDED);
> +			tcp_send_flag(c, conn, ACK | DUP_ACK);
>  			return p->count - idx;
>  
>  		}
> -- 
> 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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