netdev - Re: [bpf PATCH v2 2/6] bpf: tls fix transition through disconnect with close

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Date:   Thu, 11 Jul 2019 11:32:18 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        edumazet@...gle.com, bpf@...r.kernel.org
Subject: Re: [bpf PATCH v2 2/6] bpf: tls fix transition through disconnect
 with close

On Thu, 11 Jul 2019 09:47:16 -0700, John Fastabend wrote:
> Jakub Kicinski wrote:
> > On Wed, 10 Jul 2019 12:34:17 -0700, Jakub Kicinski wrote:  
> > > > > > +		if (sk->sk_prot->unhash)
> > > > > > +			sk->sk_prot->unhash(sk);
> > > > > > +	}
> > > > > > +
> > > > > > +	ctx = tls_get_ctx(sk);
> > > > > > +	if (ctx->tx_conf == TLS_SW || ctx->rx_conf == TLS_SW)
> > > > > > +		tls_sk_proto_cleanup(sk, ctx, timeo);  
> > 
> > Do we still need to hook into unhash? With patch 6 in place perhaps we
> > can just do disconnect 🥺  
> 
> ?? "can just do a disconnect", not sure I folow. We still need unhash
> in cases where we have a TLS socket transition from ESTABLISHED
> to LISTEN state without calling close(). This is independent of if
> sockmap is running or not.
> 
> Originally, I thought this would be extremely rare but I did see it
> in real applications on the sockmap side so presumably it is possible
> here as well.

Ugh, sorry, I meant shutdown. Instead of replacing the unhash callback
replace the shutdown callback. We probably shouldn't release the socket
lock either there, but we can sleep, so I'll be able to run the device
connection remove callback (which sleep).

> > cleanup is going to kick off TX but also:
> > 
> > 	if (unlikely(sk->sk_write_pending) &&
> > 	    !wait_on_pending_writer(sk, &timeo))
> > 		tls_handle_open_record(sk, 0);
> > 
> > Are we guaranteed that sk_write_pending is 0?  Otherwise
> > wait_on_pending_writer is hiding yet another release_sock() :(  
> 
> Not seeing the path to release_sock() at the moment?
> 
>    tls_handle_open_record
>      push_pending_record
>       tls_sw_push_pending_record
>         bpf_exec_tx_verdict

wait_on_pending_writer
  sk_wait_event
    release_sock

> If bpf_exec_tx_verdict does a redirect we could hit a relase but that
> is another fix I have to get queued up shortly. I think we can fix
> that in another series.

Ugh.