netdev - Re: [PATCH net-next v4 1/2] tcp: Update bind bucket state on port release

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Message-ID: <CAAVpQUCiH6pE9zG_iEfFGNrXW=+A3rLT-JLe0AaBqpu0Q43Pew@mail.gmail.com>
Date: Mon, 15 Sep 2025 22:45:46 -0700
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: Jakub Sitnicki <jakub@...udflare.com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Neal Cardwell <ncardwell@...gle.com>, Paolo Abeni <pabeni@...hat.com>, kernel-team@...udflare.com, 
	Lee Valentine <lvalentine@...udflare.com>
Subject: Re: [PATCH net-next v4 1/2] tcp: Update bind bucket state on port release

On Sat, Sep 13, 2025 at 3:09 AM Jakub Sitnicki <jakub@...udflare.com> wrote:
>
> Today, once an inet_bind_bucket enters a state where fastreuse >= 0 or
> fastreuseport >= 0 after a socket is explicitly bound to a port, it remains
> in that state until all sockets are removed and the bucket is destroyed.
>
> In this state, the bucket is skipped during ephemeral port selection in
> connect(). For applications using a reduced ephemeral port
> range (IP_LOCAL_PORT_RANGE socket option), this can cause faster port
> exhaustion since blocked buckets are excluded from reuse.
>
> The reason the bucket state isn't updated on port release is unclear.
> Possibly a performance trade-off to avoid scanning bucket owners, or just
> an oversight.
>
> Fix it by recalculating the bucket state when a socket releases a port. To
> limit overhead, each inet_bind2_bucket stores its own (fastreuse,
> fastreuseport) state. On port release, only the relevant port-addr bucket
> is scanned, and the overall state is derived from these.
>
> Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@...gle.com>