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

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Date: Wed, 24 Jan 2024 23:00:58 +0100
From: Vincent Bernat <vincent@...nat.ch>
To: David Ahern <dsahern@...il.com>, 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 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).