From owner-freebsd-net@FreeBSD.ORG Wed May 22 15:54:40 2013 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 7CF8383D for ; Wed, 22 May 2013 15:54:40 +0000 (UTC) (envelope-from wonko@4amlunch.net) Received: from mail-pd0-f179.google.com (mail-pd0-f179.google.com [209.85.192.179]) by mx1.freebsd.org (Postfix) with ESMTP id 5ABA1F9A for ; Wed, 22 May 2013 15:54:40 +0000 (UTC) Received: by mail-pd0-f179.google.com with SMTP id q11so1830189pdj.38 for ; Wed, 22 May 2013 08:54:39 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=date:from:to:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:x-useless-header :user-agent:x-gm-message-state; bh=WudUE93ZmTCaQLI4DA9BP4HgELwWr6s2xcnnNBw6o8U=; b=dcrAv05Gby0qpL1NEFvQzlMHrVaFRL4w0604MHwoHWoAm65BVOn4YWcTl9mC//ucOl 4+P3Bs31u/28zANfk+11D1Q5hF7eFD6JwIlTCpJPdYRm8IdLeKtxetacZIuCcGzY+MPE Nhvh5150HQGqTlv3yzdulKKgUTO9pZOHSDMEOx/hQcajRwJlCG7Wk5sKdkhC+g+6zZCn Pi/gLTrNKFIlQGU+27uoc8cUNtfRlTJXxS8OgRYOekH7f7oOXwhYPeDMEFkClnLrzhO6 +OULTvYhSpYbNAHulTki969ORLShtDsilEnFnpX74fbnXpTYl/FyVfjU4OanuWm+vhMD dlDw== X-Received: by 10.66.27.174 with SMTP id u14mr4196138pag.97.1369238079828; Wed, 22 May 2013 08:54:39 -0700 (PDT) Received: from wiggum (wiggum.4amlunch.net. [65.19.130.45]) by mx.google.com with ESMTPSA id vb8sm7761908pbc.11.2013.05.22.08.54.38 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 22 May 2013 08:54:39 -0700 (PDT) Date: Wed, 22 May 2013 11:54:37 -0400 From: Brian Hechinger To: freebsd-net@freebsd.org Subject: Re: GRE and BPF Message-ID: <20130522155437.GQ887@wiggum> References: <20130522153905.GP887@wiggum> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Useless-Header: Why? Because i can. User-Agent: Mutt/1.5.21 (2010-09-15) X-Gm-Message-State: ALoCoQlPwfVCvclUR+QfgrtBROl33R9AqF0UrTN2pt5rB4dCAKjWyfIC/P50ZowewBWl+grs1bLU X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 22 May 2013 15:54:40 -0000 On Wed, May 22, 2013 at 08:48:36AM -0700, Michael Sierchio wrote: > On Wed, May 22, 2013 at 8:39 AM, Brian Hechinger wrote: > > > Hello all, > > > > I've been having some trouble with a GRE tunnel. Specifically with > > non-IP traffic (DECnet, in this case) and BPF. > > > > I can see the GRE packets containing the DECnet packets coming over the > > physical interface but when I do a tcpdump of bge0 I never see them. > > > > This is an issue because the program I want to use will be using pcap to > > pull packets off of the bge0 interface. > > > > I can get IP packets off of the bge0 interface with tcpdump, however. > > > > Is this just never going to work or am I missing something here? > > > > > What does ifconfig report for the MTU of the gre interface? Does it match > the Cisco? Is grekey set? On the Cisco: Tunnel transport MTU 1476 bytes On the FreeBSD box: gre0: flags=9051 metric 0 mtu 1476 No grekey set. > Do you have a route to the network that is encapsulated on the other side? It will once communication is established. DECnet does dynamic routing. > is net.inet.ip.forwarding set to 1? I don't see how that's relevant unless that turns on some sort of magic? I'm not trying to do IP forwarding at all. In fact, I'm not trying to do any forwarding. I have a user mode application that just wants to read and write packets off the the GRE tunnel. -brian