February 27, 2023 10:30 AM, "Eyal Birger" [off-list ref] wrote:

Hi,

On Mon, Feb 27, 2023 at 10:19 AM Josef Miegl [off-list ref] wrote:

quoted

The Geneve encapsulation, as defined in RFC 8926, has a Protocol Type
field, which states the Ethertype of the payload appearing after the
Geneve header.

Commit 435fe1c0c1f7 ("net: geneve: support IPv4/IPv6 as inner protocol")
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 other
than IPv4, IPv6 and Ethernet.

FWIW 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 supporting
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 safeguarding
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.

quoted

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.

This 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 to
IPv4 and IPv6.

If no further modifications down the packet chain are required, I'd say it'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.

quoted

This 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.

Changes in v2:
- added a cover letter
- lines no longer exceed 80 columns

Josef Miegl (1):
net: geneve: accept every ethertype

drivers/net/geneve.c | 15 ++++-----------
1 file changed, 4 insertions(+), 11 deletions(-)

--
2.37.1