From owner-freebsd-net@FreeBSD.ORG Mon May 7 18:40:31 2012 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 204E3106567F; Mon, 7 May 2012 18:40:31 +0000 (UTC) (envelope-from adrian.chadd@gmail.com) Received: from mail-pb0-f54.google.com (mail-pb0-f54.google.com [209.85.160.54]) by mx1.freebsd.org (Postfix) with ESMTP id DC4268FC16; Mon, 7 May 2012 18:40:30 +0000 (UTC) Received: by pbbro2 with SMTP id ro2so7787940pbb.13 for ; Mon, 07 May 2012 11:40:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; bh=HtycGNeWVwLnG4Q0PQML/22SWUv20q2fnEmpCBCl2BI=; b=S9ebutVeVYw/CiHcU701RnK1HNESXR2qG2UMbRqtO9cvRo2D20/WAX8Rxl/DDCOklN jTLyL4EAzq0gQ7U+sAXwhTFDIafcRby81cEm02h//Pdv42z0Pqs9FihY3Ml9cInl3CtX I9bQwLRweNe0G1e4fwhOD583LeB2+JqnKan2RPavYoyDdi8cKIAiH6Du5winrMNgwpEs ecHLnhPcxe8p1W3VRs9/k+W7Cp64En7UXXHXh4mm77q2bsVOkSr6zDOSwhwumqSe4Ud7 wevhqtQ2nKIKm7r2guh4RIPmjrfkQfnsG0HElIDILYyYm/FZSOveLeMkXCMJva6qKjsm 000A== MIME-Version: 1.0 Received: by 10.68.221.74 with SMTP id qc10mr4493313pbc.80.1336416030513; Mon, 07 May 2012 11:40:30 -0700 (PDT) Sender: adrian.chadd@gmail.com Received: by 10.142.101.9 with HTTP; Mon, 7 May 2012 11:40:30 -0700 (PDT) In-Reply-To: <4FA6E03B.2000706@zonov.org> References: <20120427230400.GB17009@michelle.cdnetworks.com> <4FA6E03B.2000706@zonov.org> Date: Mon, 7 May 2012 11:40:30 -0700 X-Google-Sender-Auth: WBzgQRiEfJDc92P6SNSHvpNZYU0 Message-ID: From: Adrian Chadd To: Andrey Zonov Content-Type: text/plain; charset=ISO-8859-1 Cc: pyunyh@gmail.com, freebsd-net@freebsd.org, davidch@freebsd.org Subject: Re: bce: jumbo not working since r218423 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: Mon, 07 May 2012 18:40:31 -0000 .. I think you're misunderstanding how PMTU discovery works. The _point_ is that you refuse to send said frame in the first place. Any number of intermediary L2 devices may decide to drop your jumbo TX'ed frame and not generate an ICMP error message, thus breaking PMTU discovery anyway. In any case, someone from broadcom piped up and pointed out that at least for their driver, the "force strict RX MTU" is for compliance testing. Adrian