From mboxrd@z Thu Jan 1 00:00:00 1970 From: Franchoze Eric Subject: Re: Re: why do we need printk on sending syn flood cookie? Date: Mon, 02 Aug 2010 20:11:36 +0400 Message-ID: <23001280765498@web50.yandex.ru> References: <480391280735894@web102.yandex.ru> <20100802081716.GA8374@Chamillionaire.breakpoint.cc> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: Florian Westphal Return-path: Received: from forward1.mail.yandex.net ([77.88.46.6]:46836 "EHLO forward1.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753948Ab0HBQLk (ORCPT ); Mon, 2 Aug 2010 12:11:40 -0400 In-Reply-To: <20100802081716.GA8374@Chamillionaire.breakpoint.cc> Sender: netdev-owner@vger.kernel.org List-ID: 02.08.10, 12:17, "Florian Westphal" : > Franchoze Eric wrote: > > Just sirious why do we need printk each 1 second (60*HZ) about possible syn-flood? It really floods dmesg. Is there something dengerous? I have suggestion to turn off printk about sending tcp cookie each 1 second. > > It is handled exactly like other printks in the networking path, > e.g. receipt of tcp wscale == 15. > > Why does this need special treatment? > For now I see "possible SYN flooding on port %d. Sending cookies.\n" message each second on my server. I know that there are a lot of SYNs and I know that kernel sends cookie. Why do I need so mach printk? So I suggested add new value to /proc/sys/net/ipv4/tcp_syncookies, which will enable cookie but this printk will be turned off.