netdev - Re: [PATCH v2 net-next 0/2] add ppp_generic ioctl(s) to bridge channels

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Date:   Wed, 2 Dec 2020 10:34:43 +0000
From:   James Chapman <jchapman@...alix.com>
To:     Tom Parkin <tparkin@...alix.com>, netdev@...r.kernel.org
Cc:     gnault@...hat.com
Subject: Re: [PATCH v2 net-next 0/2] add ppp_generic ioctl(s) to bridge
 channels

On 01/12/2020 11:52, Tom Parkin wrote:
> Following on from my previous RFC[1], this series adds two ioctl calls
> to the ppp code to implement "channel bridging".
>
> When two ppp channels are bridged, frames presented to ppp_input() on
> one channel are passed to the other channel's ->start_xmit function for
> transmission.
>
> The primary use-case for this functionality is in an L2TP Access
> Concentrator where PPP frames are typically presented in a PPPoE session
> (e.g. from a home broadband user) and are forwarded to the ISP network in
> a PPPoL2TP session.
>
> The two new ioctls, PPPIOCBRIDGECHAN and PPPIOCUNBRIDGECHAN form a
> symmetric pair.
>
> Userspace code testing and illustrating use of the ioctl calls is
> available in the go-l2tp[2] and l2tp-ktest[3] repositories.
>
> [1]. Previous RFC series:
>
> https://lore.kernel.org/netdev/20201106181647.16358-1-tparkin@katalix.com/
>
> [2]. go-l2tp: a Go library for building L2TP applications on Linux
> systems. Support for the PPPIOCBRIDGECHAN ioctl is on a branch:
>
> https://github.com/katalix/go-l2tp/tree/tp_002_pppoe_2
>
> [3]. l2tp-ktest: a test suite for the Linux Kernel L2TP subsystem.
> Support for the PPPIOCBRIDGECHAN ioctl is on a branch:
>
> https://github.com/katalix/l2tp-ktest/tree/tp_ac_pppoe_tests_2
>
> Changelog:
>
> v2:
>     * Add missing __rcu annotation to struct channel 'bridge' field in
>       order to squash a sparse warning from a C=1 build
>     * Integrate review comments from gnault@...hat.com
>     * Have ppp_unbridge_channels return -EINVAL if the channel isn't
>       part of a bridge: this better aligns with the return code from
>       ppp_disconnect_channel.
>     * Improve docs update by including information on ioctl arguments
>       and error return codes.
>
> Tom Parkin (2):
>   ppp: add PPPIOCBRIDGECHAN and PPPIOCUNBRIDGECHAN ioctls
>   docs: update ppp_generic.rst to document new ioctls
>
>  Documentation/networking/ppp_generic.rst |   9 ++
>  drivers/net/ppp/ppp_generic.c            | 143 ++++++++++++++++++++++-
>  include/uapi/linux/ppp-ioctl.h           |   2 +
>  3 files changed, 152 insertions(+), 2 deletions(-)
>
Reviewed-by: James Chapman <jchapman@...alix.com>