Date: Wed, 22 May 2013 11:54:37 -0400 From: Brian Hechinger <wonko@4amlunch.net> To: freebsd-net@freebsd.org Subject: Re: GRE and BPF Message-ID: <20130522155437.GQ887@wiggum> In-Reply-To: <CAHu1Y73NkeeiywK7FkpXa68dz6_Hng_0dtbSZ3USt0xb%2BG2eog@mail.gmail.com> References: <20130522153905.GP887@wiggum> <CAHu1Y73NkeeiywK7FkpXa68dz6_Hng_0dtbSZ3USt0xb%2BG2eog@mail.gmail.com>
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On Wed, May 22, 2013 at 08:48:36AM -0700, Michael Sierchio wrote: > On Wed, May 22, 2013 at 8:39 AM, Brian Hechinger <wonko@4amlunch.net> 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<UP,POINTOPOINT,RUNNING,LINK0,MULTICAST> 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
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