Subject: Re: [PATCH 1/1] gtp: support SGSN-side tunnels

From: Pablo Neira Ayuso <[email-masked]>
Date: Mon, 13 Feb 2017 12:16:40 +0100

On Mon, Feb 13, 2017 at 10:25:19AM +0100, Andreas Schultz wrote:
> Hi,
> 
> I'm a bit late to comment, but maybe you can consider an additional
> change for v2...
> 
> ----- On Feb 3, 2017, at 10:12 AM, Jonas Bonn [email-masked] 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.
> > 
> > Signed-off-by: Jonas Bonn <[email-masked]>
> > ---
> > 
> > drivers/net/gtp.c            | 43 ++++++++++++++++++++++++++++++++-----------
> > include/uapi/linux/gtp.h     |  2 +-
> > include/uapi/linux/if_link.h |  5 +++++
> > 3 files changed, 38 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
> > index 50349a9..1bbac69 100644
> > --- a/drivers/net/gtp.c
> > +++ b/drivers/net/gtp.c
> > @@ -72,6 +72,7 @@ struct gtp_dev {
> > 	struct net		*net;
> > 	struct net_device	*dev;
> > 
> > +	unsigned int		flags;
> 
> This should IMHO not go into the gtp_dev, the right place
> is the PDP context.

So you want to allow mixed configurations where some PDP ctx may be in
SGSN mode while others in GGSN.

This doesn't make any sense to me. On top of this, don't forget this
is just for testing, so I don't see any valid usecase for such a fine
grain thing.