netdev - Re: [PATCH] udp: Allow to defer reception until connect() happened

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Message-ID: <CANn89iJT3khAiCzFDTk55d=mg_hmEZqMXs0xxSuXuOR8cqpggg@mail.gmail.com>
Date:   Thu, 29 Nov 2018 14:59:36 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Christoph Paasch <cpaasch@...le.com>
Cc:     jri.ietf@...il.com, netdev <netdev@...r.kernel.org>,
        Ian Swett <ianswett@...gle.com>, lhedstrom@...le.com
Subject: Re: [PATCH] udp: Allow to defer reception until connect() happened

On Thu, Nov 29, 2018 at 2:47 PM Christoph Paasch <cpaasch@...le.com> wrote:

> Indeed, the UDP-stack is not fully 4-tuple ready.
>
>
> What are your thoughts on getting it there?

This would request an additional lookup, and heavy duty servers using
non connected sockets
would pay the price for an extra lookup for each incoming packets.

DNS servers and QUIC servers would not like that, since they have better use
of a single (unconnected) UDP socket per cpu/thread.

>
> Should be doable by simply using a similar approach as TCP, no? Any caveats
> you see with that?
>
> Then, when one sets the "wait-for-connect"-flag we would add the socket to
> the hash-table only at connect()-time also addressing the cache-line miss
> you mentioned above.

Sure.