netdev - Re: [RFC PATCH net-next 1/2] tcp: ulp: add functions to dump ulp-specific information

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Date:   Mon, 17 Jun 2019 10:41:18 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Davide Caratti <dcaratti@...hat.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Dave Watson <davejwatson@...com>,
        Boris Pismenny <borisp@...lanox.com>,
        Aviad Yehezkel <aviadye@...lanox.com>,
        John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org
Subject: Re: [RFC PATCH net-next 1/2] tcp: ulp: add functions to dump
 ulp-specific information

On Mon, 17 Jun 2019 15:06:33 +0200, Davide Caratti wrote:
> > > +		if (icsk->icsk_ulp_ops->get_info_size)
> > > +			size += icsk->icsk_ulp_ops->get_info_size(sk);  
> > 
> > I don't know the diag code, is the socket locked at this point?  
> 
> as far as I can see, it's not. Thanks a lot for noticing this!
> 
> anyway, I see a similar pattern for icsk_ca_ops: when we set the congestion
> control with do_tcp_setsockopt(), the socket is locked - but then, when 'ss'
> reads a diag request with INET_DIAG_CONG bit set, the value of icsk->icsk_ca_ops
> is accessed with READ_ONCE(), surrounded by rcu_read_{,un}lock(). 
> 
> Maybe it's sufficient to do something similar, and then the socket lock can be
> optionally taken within icsk_ulp_ops->get_info(), only in case we need to access
> members of sk that are protected with the socket lock?

Sounds reasonable, we just need to keep that in mind as we extend TLS
code do dump more information.