Re: [PATCH mptcp-next v3 5/8] mptcp: userspace pm set_flags id support

[Matthieu Baerts <matttbe@kernel.org>]

Hi Geliang,

On 08/01/2025 05:21, Geliang Tang wrote:
> From: Geliang Tang <tanggeliang@kylinos.cn>
> 
> Similar to in-kernel PM, this patch adds address ID support to set_flags()
> interface of userspace PM, allowing it to work with either an address or
> an address ID.
> 
> When an address ID is used, mptcp_userspace_pm_lookup_addr_by_id() helper
> is used to look up the address entry in the local address list instead of
> using mptcp_userspace_pm_lookup_addr().

Mmh, I'm still not sure about that. As I was saying in [1], if I'm not
mistaken, with the userspace PM, it is possible not to find any entries
here, e.g.: if a subflow using this address has not been added or the
address has not been announced. (I guess the initial address is not
there then).

Do you think this patch is worth it? Setting by ID for the in-kernel PM
makes sense: unique ID for the netns, easier to type the ID than the
full address. While for the userspace PM, it will be managed by a daemon
that will have to track addresses anyway.

Or in other words, do you have a use-case for this? To me, it looks like
"yes, you can only set the ID, but it might not always work". Then maybe
better to always set the full address, no?

[1]
https://lore.kernel.org/mptcp/d01d0e8a-5606-4152-aabe-32e4402adeeb@kernel.org/

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.