netdev - [PATCH net-next 0/3] mlxsw: Removing dependency of mlxsw on GRE

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Message-Id: <20180311074549.14112-1-idosch@mellanox.com>
Date:   Sun, 11 Mar 2018 09:45:46 +0200
From:   Ido Schimmel <idosch@...lanox.com>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, petrm@...lanox.com, jiri@...lanox.com,
        dsahern@...il.com, mlxsw@...lanox.com,
        Ido Schimmel <idosch@...lanox.com>
Subject: [PATCH net-next 0/3] mlxsw: Removing dependency of mlxsw on GRE

Petr says:

mlxsw_spectrum supports offloading of a tc action mirred egress mirror
to a gretap or ip6gretap netdevice, which necessitates calls to
functions defined in ip_gre, ip6_gre and ip6_tunnel modules. Previously
this was enabled by introducing a hard dependency of MLXSW_SPECTRUM on
NET_IPGRE and IPV6_GRE. However the rest of mlxsw is careful about
picking which modules are absolutely required, and therefore the better
approach is to make mlxsw_spectrum tolerant of absence of one or both of
the GRE flavors.

One way this might be resolved is by keeping the code in mlxsw_spectrum
intact, and defining defaults for functions that mlxsw_spectrum depends
on. The downsides are that other modules end up littered with these
do-nothing defaults; that the driver ends up carrying quite a bit of
dead code; and that the driver ends up having to explicitly depend on
IPV6_TUNNEL to prevent configurations where mlxsw_spectrum is compiled
in and and ip6_tunnel is a module, something that it currently can treat
as an implementation detail of the IPV6_GRE dependency.

Alternatively, the driver should just bite the bullet and ifdef-out the
code that handles configurations that are not supported. Since that's
what we are doing for IPv6 dependency, let's do the same for the GRE
flavors.

Patch #1 introduces a wrapper function for determining the value of
ipv6.sysctl.multipath_hash_policy, which defaults to 0 on non-IPv6
builds. That function is then used from spectrum_router.c, instead of
the direct variable reference that was introduced there during the short
window when the Spectrum driver had a hard dependency on IPv6.

Patch #2 moves one function to keep together in one block all the
callbacks for handling (IPv4) gretap mirroring.

Patch #3 then introduces the ifdefs to hide the irrelevant code.

Petr Machata (3):
  net: ipv6: Introduce ip6_multipath_hash_policy()
  mlxsw: spectrum: Move mlxsw_sp_span_gretap4_route()
  mlxsw: spectrum: Don't depend on ip_gre and ip6_gre

 drivers/net/ethernet/mellanox/mlxsw/Kconfig        |  6 +-
 .../net/ethernet/mellanox/mlxsw/spectrum_router.c  |  2 +-
 .../net/ethernet/mellanox/mlxsw/spectrum_span.c    | 76 ++++++++++++----------
 include/net/ipv6.h                                 | 11 ++++
 4 files changed, 56 insertions(+), 39 deletions(-)

-- 
2.14.3