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Date:   Mon, 27 Feb 2023 09:57:03 +0000
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From:   "Josef Miegl" <josef@miegl.cz>
Message-ID: <79dee14b9b96d5916a8652456b78c7a5@miegl.cz>
Subject: Re: [PATCH v2 0/1] net: geneve: accept every ethertype
To:     "Eyal Birger" <eyal.birger@gmail.com>
Cc:     "David S. Miller" <davem@davemloft.net>,
        "Eric Dumazet" <edumazet@google.com>,
        "Jakub Kicinski" <kuba@kernel.org>,
        "Paolo Abeni" <pabeni@redhat.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
In-Reply-To: <CAHsH6GtArNCyA3UAJbSYYD86fb2QxskbSoNQo2RVHQzKC643zg@mail.gmail.com>
References: <CAHsH6GtArNCyA3UAJbSYYD86fb2QxskbSoNQo2RVHQzKC643zg@mail.gmail.com>
 <20230227074104.42153-1-josef@miegl.cz>
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February 27, 2023 10:30 AM, "Eyal Birger" <eyal.birger@gmail.com> wrote:

> Hi,
>=20
>=20On Mon, Feb 27, 2023 at 10:19 AM Josef Miegl <josef@miegl.cz> wrote:
>=20
>>=20The Geneve encapsulation, as defined in RFC 8926, has a Protocol Typ=
e
>> field, which states the Ethertype of the payload appearing after the
>> Geneve header.
>>=20
>>=20Commit 435fe1c0c1f7 ("net: geneve: support IPv4/IPv6 as inner protoc=
ol")
>> introduced a new IFLA_GENEVE_INNER_PROTO_INHERIT flag that allowed the
>> use of other Ethertypes than Ethernet. However, for a reason not known
>> to me, it imposed a restriction that prohibits receiving payloads othe=
r
>> than IPv4, IPv6 and Ethernet.
>=20
>=20FWIW I added support for IPv4/IPv6 because these are the use cases I =
had
> and could validate. I don't know what problems could arise from support=
ing
> all possible ethertypes and can't test that.

Yeah, I am hoping someone knowledgeable will tell whether this is a good
or bad idea. However I think that if any problem could arise, this is not
the place to artificially restrict payload types and potentional safeguar=
ding
should be done somewhere down the packet chain.

I can't imagine adding a payload Ethertype every time someone needs a
specific use-case would be a good idea.

>> This patch removes this restriction, making it possible to receive any
>> Ethertype as a payload, if the IFLA_GENEVE_INNER_PROTO_INHERIT flag is
>> set.
>=20
>=20This seems like an addition not a bugfix so personally seems like it =
should
> be targeting net-next (which is currently closed afaik).

One could say the receive function should have behaved like that, the
transmit function already encapsulates every possible Ethertype and
IFLA_GENEVE_INNER_PROTO_INHERIT doesn't sound like it should be limited t=
o
IPv4 and IPv6.

If no further modifications down the packet chain are required, I'd say i=
t's
50/50. However I haven't contributed to the Linux kernel ever before, so =
I
really have no clue as to how things go.

> Eyal.
>=20
>>=20This is especially useful if one wants to encapsulate MPLS, because =
with
>> this patch the control-plane traffic (IP, LLC) and the data-plane
>> traffic (MPLS) can be encapsulated without an Ethernet frame, making
>> lightweight overlay networks a possibility.
>>=20
>>=20Changes in v2:
>> - added a cover letter
>> - lines no longer exceed 80 columns
>>=20
>>=20Josef Miegl (1):
>> net: geneve: accept every ethertype
>>=20
>>=20drivers/net/geneve.c | 15 ++++-----------
>> 1 file changed, 4 insertions(+), 11 deletions(-)
>>=20
>>=20--
>> 2.37.1