netdev - Re: updates to syncookies - timestamps not needed any more (freebsd)

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Message-ID: <20130726064544.GC24247@order.stressinduktion.org>
Date:	Fri, 26 Jul 2013 08:45:44 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Florian Westphal <fw@...len.de>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: updates to syncookies - timestamps not needed any more (freebsd)

Hi Eric!

On Fri, Jul 12, 2013 at 07:04:45AM -0700, Eric Dumazet wrote:
> BTW, following patch allows to test more easily syncookies behavior.
> 
> If sysctl_tcp_syncookies is set to 2, we always use syncookies.
> 
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index 35675e4..590659e 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -1462,7 +1462,8 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
>  	 * limitations, they conserve resources and peer is
>  	 * evidently real one.
>  	 */
> -	if (inet_csk_reqsk_queue_is_full(sk) && !isn) {
> +	if ((sysctl_tcp_syncookies == 2 ||
> +	     inet_csk_reqsk_queue_is_full(sk)) && !isn) {
>  		want_cookie = tcp_syn_flood_action(sk, skb, "TCP");
>  		if (!want_cookie)
>  			goto drop;
> 

While cleaning up my patch directory I found this snippet. Perhaps you
could send it for inclusion for net-next? Three nice additions: a similar
change in tcp_ipv6.c and perhaps get rid of the warning messages printed
to the console in case of syncookies == 2? A small update to ip-sysctl.txt
wouldn't hurt either.

If you want to, I can take it and refresh it.

Thanks,

  Hannes

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