From: Theo Buehler <tb@theobuehler.org>
Subject: Re: bgpd: drop PREFIX_ADJOUT_FLAG_STALE use
To: tech@openbsd.org
Date: Mon, 15 Dec 2025 06:10:24 +0100

On Sun, Dec 14, 2025 at 11:05:08AM +0100, Claudio Jeker wrote:
> up_generate_addpath() is the only user of PREFIX_ADJOUT_FLAG_STALE.
> 
> Instead of marking prefixes with PREFIX_ADJOUT_FLAG_STALE
> up_generate_addpath() can use a local array of path ids to track which
> paths were present at the start of the call, clear the path id during
> updates and then add then end remove all paths that are still present in
> the list. 
> 
> While this does a lot of linear walks I doubt this matters. The number of
> paths is normally very small and so this linear search is all cached.
> It is possible to further optimize this by also tracking the adjout_prefix
> pointer to drop the adjout_prefix_get() call at the end.
> 
> This also uses a fixed maximum of 2000 paths which is more than a
> magnitude more than the amount the nlnog looking glass needs. Which is
> AFAIK the biggest system using addpath. Normally people will limit the
> amounts of selected paths to a handful.

Reads fine and if it helps you move forward it looks like a decent
enough tradeoff.

ok tb