netdev - Re: [PATCH iproute2] vxlan: add support for flowlab inherit

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Message-ID: <1e2ff78d-d130-46d4-b7ad-31a0f6796e1a@gmail.com>
Date: Thu, 25 Jan 2024 08:50:56 -0700
From: David Ahern <dsahern@...il.com>
To: Vincent Bernat <vincent@...nat.ch>, Ido Schimmel <idosch@...sch.org>,
 Alce Lafranque <alce@...ranque.net>
Cc: netdev@...r.kernel.org, stephen@...workplumber.org
Subject: Re: [PATCH iproute2] vxlan: add support for flowlab inherit

On 1/24/24 3:00 PM, Vincent Bernat wrote:
> On 2024-01-23 17:19, David Ahern wrote:
> 
>>>>> My personal
>>>>> preference would be to add a new keyword for the new attribute:
>>>>>
>>>>> # ip link set dev vx0 type vxlan flowlabel_policy inherit
>>>>> # ip link set dev vx0 type vxlan flowlabel_policy fixed flowlabel 10
>>>>>
>>>>> But let's see what David thinks.
>>>>>
>>>>
>>>> A new keyword for the new attribute seems like the most robust.
>>>>
>>>> That said, inherit is already used in several ip commands for dscp, ttl
>>>> and flowlabel for example; I do not see a separate keyword - e.g.,
>>>> ip6tunnel.c.
>>>
>>> The implementation for flowlabel was modeled along ttl. We did diverge
>>> for kernel, we can diverge for iproute2 as well. However, I am unsure if
>>> you say we should go for option A (new attribute) or option B (do like
>>> for dscp/ttl).
>>
>> A divergent kernel API does not mean the command line for iproute2 needs
>> to be divergent. Consistent syntax across ip commands is best from a
>> user perspective. What are the downsides to making 'inherit' for
>> flowlabel work for vxlan like it does for ip6tunnel, ip6tnl and gre6?
>> Presumably inherit is relevant for geneve? (We really need to stop
>> making these tweaks on a single protocol basis.)
> 
> Currently, the patch implements "inherit" without a new keyword, like
> this is done for the other protocols. I don't really see a downside,
> except the kernel could one day implement a policy that may be difficult
> to express this way (inherit-during-the-day-fixed-during-the-night).

Wouldn't other uses of inherit be subject to the same kind of problem?
ie., my primary point is for consistency in behavior across commands.