netdev - RE: [net-next v6 1/2] net/tls: Use socket data_ready callback on record availability

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Date:   Wed, 25 Jul 2018 05:51:32 +0000
From:   Vakul Garg <vakul.garg@....com>
To:     David Miller <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "borisp@...lanox.com" <borisp@...lanox.com>,
        "aviadye@...lanox.com" <aviadye@...lanox.com>,
        "davejwatson@...com" <davejwatson@...com>
Subject: RE: [net-next v6 1/2] net/tls: Use socket data_ready callback on
 record availability

> -----Original Message-----
> From: David Miller [mailto:davem@...emloft.net]
> Sent: Wednesday, July 25, 2018 1:43 AM
> To: Vakul Garg <vakul.garg@....com>
> Cc: netdev@...r.kernel.org; borisp@...lanox.com;
> aviadye@...lanox.com; davejwatson@...com
> Subject: Re: [net-next v6 1/2] net/tls: Use socket data_ready callback on
> record availability
> 
> From: Vakul Garg <vakul.garg@....com>
> Date: Tue, 24 Jul 2018 15:44:02 +0530
> 
> > On receipt of a complete tls record, use socket's saved data_ready
> > callback instead of state_change callback.
> >
> > Signed-off-by: Vakul Garg <vakul.garg@....com>
> 
> I don't think this is correct.
> 
> Here, the stream parser has given us a complete TLS record.
> 
> But we haven't decrypted this packet yet.  It sits on the stream parser's
> queue to be processed by tls_sw_recvmsg(), not the saved socket's receive
> queue.

I understand that at this point in code, the TLS record is still queued in encrypted
state. But the decryption happens inline when tls_sw_recvmsg() gets invokved.
So it should be ok to notify the  waiting context about the availability of data as soon
as we could collect a full TLS record.

For new data availability notification, sk_data_ready callback should be more
more appropriate. It points to sock_def_readable() which wakes up specifically for
EPOLLIN event. 

This is in contrast to the socket callback sk_state_change which points
to sock_def_wakeup() which issues a wakeup unconditionally (without event mask).