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

Hi,

----- On Feb 13, 2017, at 12:16 PM, pablo pablo@netfilter.org wrote:

On Mon, Feb 13, 2017 at 10:25:19AM +0100, Andreas Schultz wrote:

quoted

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 jonas@southpole.se wrote:

quoted

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 <jonas@southpole.se>
---

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.

You are right, running such a configuration does not make sense.
However, when I wrote this the PDP context looked like the most
sensible palace to me.

Anyhow, thinking about this again, I think that integrating that flag
in a rewrite of the validation logic in the Rx path make more sense.
Currently we validate the MS as soon as we have found the PDP context.
This should be delayed a bit and the validation should happen after
pulling the GTP header and right before injecting the payload into
the net device. The flag would then indeed go into the gtp_dev.

Andreas