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bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the c
From: |
Lars Ingebrigtsen |
Subject: |
bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous |
Date: |
Sat, 30 Jan 2016 23:55:57 +0100 |
User-agent: |
Gnus/5.130014 (Ma Gnus v0.14) Emacs/25.1.50 (gnu/linux) |
Eli Zaretskii <eliz@gnu.org> writes:
>> The problem is, though, that the process isn't marked as a gnutls
>> process until gnutls_boot is called, so this needs to happen much
>> earlier. Possibly by adding another keyword to make-network-process
>> that just sets
>>
>> XPROCESS (proc)->gnutls_p = 1;
>
> Why do you need to mark a process gnutls_p, when it definitely still
> isn't, not until the GnuTLS negotiation is successfully completed?
It is a socket that will only be used for TLS. And the current way
we're creating TLS streams is by calling `open-gnutls-stream', which
(simplified) just calls `make-network-stream' and then `gnutls-boot' in
rapid succession. So any stream you get out of `open-gnutls-stream'
will look just the same -- it'll have gnutls_p set.
It'll just happen slightly earlier.
> That'd just add confusion (a.k.a. "bugs waiting to happen") on the C
> level. Can't we use a GnuTLS-specific sentinel instead?
I'm not sure I follow... a sentinel?
>> The other problem is that reading/writing from these things will just
>> send plain text if the gnutls stuff hasn't been initialised:
>>
>> #ifdef HAVE_GNUTLS
>> if (p->gnutls_p && p->gnutls_state)
>> written = emacs_gnutls_write (p, cur_buf, cur_len);
>> else
>> #endif
>> written = emacs_write_sig (outfd, cur_buf, cur_len);
>>
>> I think that looks rather nonsensical.
>
> Does this happen today? If so, in what scenario?
It does not happen today, but it will happen if we open the TLS stream
:nowait. For instance, url.el calls `open-network-stream' and then
sends a "GET /" on the socket immediately. Since setup is synchronous
today, that's fine, but when it gets async, then that p->gnutls_state
will be 0, and url.el will send an unencrypted "GET /" to the server,
which will fail, of course.
> If you want GnuTLS negotiation to happen from the sentinel, you need
> some machinery to block such process objects from communicating.
> I'm not sure silently skipping I/O is TRT for that: won't Lisp
> programs that happen to start communicating too early become confused
> about what's going on?
The "GET /" will block, sort of, as it would on any socket that's backed
up. I don't think there will be anything user-noticeable from, say, the
perspective of `send-process-string'...
> More generally, what advantages do we expect to gain by making these
> changes? Let DNS resolution proceed in the background, only to have
> to wait for GnuTLS negotiations anyway, before we can start using the
> stream? Or are there more significant advantages?
It makes the entire connection, both the DNS resolution and the TLS
negotiation, asynchronous. So Emacs doesn't hang while eww is
connecting to https://google.com.
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no
- bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous, Lars Ingebrigtsen, 2016/01/29
- bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous, Lars Ingebrigtsen, 2016/01/29
- bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous, Eli Zaretskii, 2016/01/30
- bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous,
Lars Ingebrigtsen <=
- bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous, Lars Ingebrigtsen, 2016/01/30
- bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous, Lars Ingebrigtsen, 2016/01/30
- bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous, Eli Zaretskii, 2016/01/31
- bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous, Eli Zaretskii, 2016/01/31
- bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous, Lars Ingebrigtsen, 2016/01/31
- bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous, Lars Ingebrigtsen, 2016/01/31
- bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous, Eli Zaretskii, 2016/01/31
- bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous, Lars Ingebrigtsen, 2016/01/31
- bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous, Eli Zaretskii, 2016/01/31