From owner-freebsd-ipfw@FreeBSD.ORG Thu Jul 16 20:22:45 2009 Return-Path: Delivered-To: freebsd-ipfw@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 5A93C106566B for ; Thu, 16 Jul 2009 20:22:45 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from asmtpout021.mac.com (asmtpout021.mac.com [17.148.16.96]) by mx1.freebsd.org (Postfix) with ESMTP id 468AE8FC2E for ; Thu, 16 Jul 2009 20:22:45 +0000 (UTC) (envelope-from cswiger@mac.com) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Received: from cswiger1.apple.com ([17.227.140.124]) by asmtp021.mac.com (Sun Java(tm) System Messaging Server 6.3-8.01 (built Dec 16 2008; 32bit)) with ESMTPSA id <0KMW001DH35KAP70@asmtp021.mac.com> for freebsd-ipfw@freebsd.org; Thu, 16 Jul 2009 12:22:33 -0700 (PDT) Message-id: <2CE3CD12-D430-4378-92C1-591227888428@mac.com> From: Chuck Swiger To: Dmitriy Demidov In-reply-to: <200907162219.04986.dima_bsd@inbox.lv> Date: Thu, 16 Jul 2009 12:22:32 -0700 References: <200907142355.34973.dima_bsd@inbox.lv> <200907162219.04986.dima_bsd@inbox.lv> X-Mailer: Apple Mail (2.935.3) Cc: freebsd-ipfw@freebsd.org Subject: Re: ipfw nat and localy initiated UDP traffic (bad udp cksum) X-BeenThere: freebsd-ipfw@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: IPFW Technical Discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 16 Jul 2009 20:22:45 -0000 On Jul 16, 2009, at 12:19 PM, Dmitriy Demidov wrote: > Update about this issue. > There is somthing wrong with UDP pass through - ipfw nat makes it > "bad cksum". tcpdump receives local network traffic before the checksums are computed (especially if hardware checksums are enabled); this is a non- issue, although you could confirm by sniffing the traffic from an external machine like a laptop. Regards, -- -Chuck