From owner-freebsd-net@FreeBSD.ORG Thu Mar 15 20:12:28 2012 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id BF7561065676 for ; Thu, 15 Mar 2012 20:12:28 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from asmtpout028.mac.com (asmtpout028.mac.com [17.148.16.103]) by mx1.freebsd.org (Postfix) with ESMTP id A668B8FC08 for ; Thu, 15 Mar 2012 20:12:28 +0000 (UTC) MIME-version: 1.0 Content-type: text/plain; charset=iso-8859-1 Received: from cswiger1.apple.com (unknown [17.209.4.71]) by asmtp028.mac.com (Oracle Communications Messaging Server 7u4-23.01 (7.0.4.23.0) 64bit (built Aug 10 2011)) with ESMTPSA id <0M0Y0025D04RXX60@asmtp028.mac.com> for freebsd-net@freebsd.org; Thu, 15 Mar 2012 13:12:28 -0700 (PDT) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.6.7498,1.0.260,0.0.0000 definitions=2012-03-15_04:2012-03-15, 2012-03-14, 1970-01-01 signatures=0 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 ipscore=0 suspectscore=0 phishscore=0 bulkscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=6.0.2-1012030000 definitions=main-1203150210 From: Chuck Swiger In-reply-to: <3807CE6F3BF4B04EB897F4EBF2D258CE5C05F221@yuhanna.magnetdigital.local> Date: Thu, 15 Mar 2012 13:12:26 -0700 Content-transfer-encoding: quoted-printable Message-id: <38FA7BAB-AC2B-4515-85CF-27F77C3F4313@mac.com> References: <3807CE6F3BF4B04EB897F4EBF2D258CE5C05F221@yuhanna.magnetdigital.local> To: =?iso-8859-1?Q?Seyit_=D6zg=FCr?= X-Mailer: Apple Mail (2.1084) Cc: "freebsd-net@freebsd.org" Subject: Re: Malformed syn packet cause %100 cpu and interrupts FreeBSD 9.0 release X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 15 Mar 2012 20:12:28 -0000 On Mar 15, 2012, at 12:49 PM, Seyit =D6zg=FCr wrote: > Today we tried to see what happens Malformed syn packets on FreeBSD = 9.0 release.. >=20 > Those packets rise to CPU %100 and stucks.. >=20 > listening on ix0, link-type EN10MB (Ethernet), capture size 65535 = bytes > 18:33:30.010215 IP vgn44-1-88-123-89-40.fbx.proxad.net > = 85.xxx.xxx.90: tcp > 18:33:30.010242 IP 225.74.196.88.sta.estpak.ee > 85.xxx.xxx.90: tcp > 18:33:30.010269 IP Nnov-Prospekt.71.quantum.rn > 85.xxx.xxx.90: tcp > 18:33:30.010296 IP host52-108-static.49-88-b.business.telecomitalia.it = > 85.xxx.xxx.90: tcp > 18:33:30.010325 IP 125.Red-88-1-75.dynamicIP.rima-tde.net > = 85.xxx.xxx.90: tcp >=20 > i dont know which tool generate those packets.. but as we see i dont = see seq, flag, lenth etc.. just this ouput on tcpdump... >=20 > Is there any kernel feature for do NOT process malformed syn packets = ?? A firewall can block them before the system will see and try to process = them as incoming traffic. Also, running tcpdump with -X will give both hex and ASCII rendition of = the packets, which would be helpful to identify what you mean by = "malformed". Regards, --=20 -Chuck