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

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Date:   Sun, 29 Jul 2018 06:01:29 +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

Hi David

Could you please correct me if my counter-reasoning behind changing the socket callback is wrong?

Thanks & Regards

Vakul

> -----Original Message-----
> From: Vakul Garg
> Sent: Wednesday, July 25, 2018 11:22 AM
> To: David Miller <davem@...emloft.net>
> 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
> 
> 
> 
> > -----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).