From owner-freebsd-net@FreeBSD.ORG Fri Oct 7 17:02:25 2011 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id E0019106564A for ; Fri, 7 Oct 2011 17:02:25 +0000 (UTC) (envelope-from mike@sentex.net) Received: from smarthost1.sentex.ca (smarthost1-6.sentex.ca [IPv6:2607:f3e0:0:1::12]) by mx1.freebsd.org (Postfix) with ESMTP id A36BB8FC13 for ; Fri, 7 Oct 2011 17:02:25 +0000 (UTC) Received: from [IPv6:2607:f3e0:0:4:f025:8813:7603:7e4a] (saphire3.sentex.ca [IPv6:2607:f3e0:0:4:f025:8813:7603:7e4a]) by smarthost1.sentex.ca (8.14.5/8.14.4) with ESMTP id p97H2LL8036122; Fri, 7 Oct 2011 13:02:22 -0400 (EDT) (envelope-from mike@sentex.net) Message-ID: <4E8F3091.6040106@sentex.net> Date: Fri, 07 Oct 2011 13:02:09 -0400 From: Mike Tancsa Organization: Sentex Communications User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.13) Gecko/20101207 Thunderbird/3.1.7 MIME-Version: 1.0 To: Ryan Stone References: In-Reply-To: X-Enigmail-Version: 1.1.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.71 on IPv6:2607:f3e0:0:1::12 Cc: freebsd-net Subject: Re: [PATCH] Don't have ICMP Echo Replies copy fragmentation flags from Echo Request 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: Fri, 07 Oct 2011 17:02:26 -0000 On 10/7/2011 11:54 AM, Ryan Stone wrote: > Currently when FreeBSD responds to a ICMP Echo Request, it takes the > original mbuf, rewrites a couple of fields (like the src/dst IP and > the ICMP type), and then sends that mbuf back. As things are > currently implemented, the Don't Fragment bit is kept in the ICMP > replay. This can cause problems for large ICMP Echo Requests if the > MTU on the return route is less than the MTU on the incoming route and > the DF bit is set(Linux's ping command sets it by default). Not sure, but would this not be a "good thing" in some cases ? Having ping behave in this manner would help you discover such PMTU issues no ? ---Mike -- ------------------- Mike Tancsa, tel +1 519 651 3400 Sentex Communications, mike@sentex.net Providing Internet services since 1994 www.sentex.net Cambridge, Ontario Canada http://www.tancsa.com/