netdev - Re: [PATCH net-next 09/14] gtp: Allow configuring GTP interface as standalone

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Date:   Wed, 20 Sep 2017 08:57:26 -0700
From:   Tom Herbert <tom@...bertland.com>
To:     Andreas Schultz <aschultz@...p.net>
Cc:     Tom Herbert <tom@...ntonium.net>,
        "David S. Miller" <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Harald Welte <laforge@...monks.org>,
        Rohit Seth <rohit@...ntonium.net>
Subject: Re: [PATCH net-next 09/14] gtp: Allow configuring GTP interface as standalone

On Wed, Sep 20, 2017 at 8:27 AM, Andreas Schultz <aschultz@...p.net> wrote:
> On 19/09/17 02:38, Tom Herbert wrote:
>>
>> Add new configuration of GTP interfaces that allow specifying a port to
>> listen on (as opposed to having to get sockets from a userspace control
>> plane). This allows GTP interfaces to be configured and the data path
>> tested without requiring a GTP-C daemon.
>
>
> This would imply that you can have multiple independent GTP sockets on the
> same IP address.That is not permitted by the GTP specifications. 3GPP TS
> 29.281, section 4.3 states clearly that there is "only" one GTP entity per
> IP address.A PDP context is defined by the destination IP and the TEID. The
> destination port is not part of the identity of a PDP context.
>
We are in no way trying change GTP, if someone runs this in a real GTP
network then they need to abide by the specification. However, there
is nothing inconsistent and it breaks nothing if someone wishes to use
different port numbers in their own private network for testing or
development purposes. Every other UDP application that has assigned
port number allows configurable ports, I don't see that GTP is so
special that it should be an exception.

Tom