From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Schultz Subject: Re: [PATCH 1/1] gtp: support SGSN-side tunnels Date: Mon, 6 Feb 2017 18:27:09 +0100 (CET) Message-ID: <1174391417.758308.1486402029809.JavaMail.zimbra@tpip.net> References: <20170203091231.10142-1-jonas@southpole.se> <20170206110858.GA3896@salvia> <3efa90fe-3f66-1da0-6038-4fbf9ec2b7ce@southpole.se> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: pablo , laforge , netdev To: Jonas Bonn Return-path: Received: from mail.tpip.net ([92.43.49.48]:48513 "EHLO mail.tpip.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750953AbdBFR1M (ORCPT ); Mon, 6 Feb 2017 12:27:12 -0500 In-Reply-To: <3efa90fe-3f66-1da0-6038-4fbf9ec2b7ce@southpole.se> Sender: netdev-owner@vger.kernel.org List-ID: Hi Jonas, Sorry, for later reply, I'm currently on vacation with almost no internet access. ----- On Feb 6, 2017, at 2:33 PM, Jonas Bonn jonas@southpole.se wrote: > Hi Pablo, > > On 02/06/2017 12:08 PM, Pablo Neira Ayuso wrote: >> Hi Jonas, >> >> On Fri, Feb 03, 2017 at 10:12:31AM +0100, Jonas Bonn wrote: >>> The GTP-tunnel driver is explicitly GGSN-side as it searches for PDP >>> contexts based on the incoming packets _destination_ address. If we >>> want to write an SGSN, then we want to be idenityfing PDP contexts >>> based on _source_ address. >>> >>> This patch adds a "flags" argument at GTP-link creation time to specify >>> whether we are on the GGSN or SGSN side of the tunnel; this flag is then >>> used to determine which part of the IP packet to use in determining >>> the PDP context. >> So far the implementation that I saw in osmocom relies on userspace code >> to tunnel data from ME to the SSGN/SGW running on the base station. >> >> The data we get from GGSN -> SGSN needs to be places into a SN-PDU (via >> SNDCP) when sending it to the BTS, right? So I wonder how this can be >> useful given that we would need to see real IP packets coming to the >> SSGN that we tunnel into GTP. > > Fair enough. The use-case I am looking at involves PGW load-testing > where the simulated load is generated locally on the SGSN so it _is_ > seeing IP packets and the SNDCP is left out altogether. Perhaps this is > too pathological to warrant messing with the upstream driver... I don't > know: the symmetry does not cost much even if it's of limited use. Sounds reasonable. I'll review change with that in mind next week. Andreas > Couldn't the SNDCP theoretically be a separate node and push IP packets > to the SGSN, thus making this useful? Perhaps it's a stretch... > > /Jonas