netdev - Re: [PATCH net-next v2] gtp: add notification mechanism

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Date:   Tue, 25 Aug 2020 19:01:09 +0200
From:   Harald Welte <laforge@...monks.org>
To:     Nicolas Dichtel <nicolas.dichtel@...nd.com>
Cc:     davem@...emloft.net, kuba@...nel.org, pablo@...filter.org,
        osmocom-net-gprs@...ts.osmocom.org, netdev@...r.kernel.org,
        Gabriel Ganne <gabriel.ganne@...nd.com>
Subject: Re: [PATCH net-next v2] gtp: add notification mechanism

Hi Nicolas,

thanks a lot for your patch.

On Tue, Aug 25, 2020 at 05:57:15PM +0200, Nicolas Dichtel wrote:
> Like all other network functions, let's notify gtp context on creation and
> deletion.

While this may be in-line with typical kernel tunnel device practises, I am not
convinced it is the right way to go for GTP.

Contrary to other tunneling mechansims, GTP doesn't have a 1:1 rlationship between
tunnels and netdev's.  You can easily have tens of thousands - or even many more -
PDP contexts (at least one per subscriber) within one "gtp0" netdev.  Also, the state
is highly volatile.  Every time a subscriber registers/deregisters, goes in or out of
coverage, in or out of airplane mode, etc. those PDP contexts go up and down.

Sending (unsolicited) notifications about all of those seems quite heavyweight to me.

-- 
- Harald Welte <laforge@...monks.org>           http://laforge.gnumonks.org/
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