From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jonas Bonn Subject: Re: [PATCH 1/1] gtp: support SGSN-side tunnels Date: Mon, 6 Feb 2017 14:33:07 +0100 Message-ID: <3efa90fe-3f66-1da0-6038-4fbf9ec2b7ce@southpole.se> References: <20170203091231.10142-1-jonas@southpole.se> <20170206110858.GA3896@salvia> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: laforge@gnumonks.org, netdev@vger.kernel.org To: Pablo Neira Ayuso Return-path: Received: from mail.southpole.se ([37.247.8.11]:48070 "EHLO mail.southpole.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752764AbdBFNdM (ORCPT ); Mon, 6 Feb 2017 08:33:12 -0500 In-Reply-To: <20170206110858.GA3896@salvia> Sender: netdev-owner@vger.kernel.org List-ID: 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. 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