netdev - Re: [PATCH] net:ipv4: send an ack when seg.ack

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Message-ID: <20220319100443.GA13956@breakpoint.cc>
Date:   Sat, 19 Mar 2022 11:04:43 +0100
From:   Florian Westphal <fw@...len.de>
To:     zhouzhouyi@...il.com
Cc:     edumazet@...gle.com, davem@...emloft.net, yoshfuji@...ux-ipv6.org,
        dsahern@...nel.org, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Wei Xu <xuweihf@...c.edu.cn>
Subject: Re: [PATCH] net:ipv4: send an ack when seg.ack > snd.nxt

zhouzhouyi@...il.com <zhouzhouyi@...il.com> wrote:
> -	if (after(ack, tp->snd_nxt))
> +	if (after(ack, tp->snd_nxt)) {
> +		tcp_send_ack(sk);
>  		return -1;
> +	}

If we really need to do this we need to
  if (!(flag & FLAG_NO_CHALLENGE_ACK))
	tcp_send_challenge_ack(sk);

... else this might result in two acks?
Whats the problem thats being fixed here?