netdev - Re: [PATCH net-next v4 4/6] docs: tls: document TLS1.3 key updates

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Message-ID: <Z1GJPUUR-wllqX3w@hog>
Date: Thu, 5 Dec 2024 12:06:37 +0100
From: Sabrina Dubroca <sd@...asysnail.net>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, Vadim Fedorenko <vfedorenko@...ek.ru>,
	Frantisek Krenzelok <fkrenzel@...hat.com>,
	Kuniyuki Iwashima <kuniyu@...zon.com>,
	Apoorv Kothari <apoorvko@...zon.com>,
	Boris Pismenny <borisp@...dia.com>,
	John Fastabend <john.fastabend@...il.com>,
	Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
	Gal Pressman <gal@...dia.com>,
	Marcel Holtmann <marcel@...tmann.org>,
	Simon Horman <horms@...nel.org>
Subject: Re: [PATCH net-next v4 4/6] docs: tls: document TLS1.3 key updates

2024-12-03, 19:51:29 -0800, Jakub Kicinski wrote:
> On Thu, 14 Nov 2024 16:50:51 +0100 Sabrina Dubroca wrote:
> > +To prevent attempting to decrypt incoming records using the wrong key,
> > +decryption will be paused when a KeyUpdate message is received by the
> > +kernel, until the new key has been provided using the TLS_RX socket
> > +option. Any read occurring after the KeyUpdate has been read and
> > +before the new key is provided will fail with EKEYEXPIRED. Poll()'ing
> > +the socket will also sleep until the new key is provided. There is no
> > +pausing on the transmit side.
> 
> Thanks for the doc update, very useful. I'm not a socket expert so dunno
> if suppressing POLLIN is the right thing to do.

Not an expert either. I picked that because there's no data to be
read, which is what POLLIN should mean.

man 2 poll:
       POLLIN There is data to read.

man 3 poll:
       POLLIN      Data other than high-priority data may be read
                   without blocking.

Based on this, reporting POLLIN seems wrong to me.

> But a nit on the
> phrasing - I'd say "poll() will not report any events from the socket
> until.." ? Could be just me but sleep is a second order effect.

Agree, thanks for the suggestion. Maybe actually "will not report read
events"? Other events are unaffected by a pending rekey.

-- 
Sabrina