* [Feature #21347] Add `open_timeout` as an overall timeout option for `TCPSocket.new`

With this change, `TCPSocket.new` now accepts the `open_timeout` option.
This option raises an exception if the specified number of seconds has elapsed since the start of the method call,
even if the operation is still in the middle of name resolution or connection attempts.

The addition of this option follows the same intent as the previously merged change to `Socket.tcp`.
[Feature #21347](https://bugs.ruby-lang.org/issues/21347)
https://github.com/ruby/ruby/pull/13368

* Tidy up: Extract rsock_raise_user_specified_timeout()

* Added a note to the documentation of `Socket.tcp`

* Fix `rsock_init_inetsock` for `FAST_FALLBACK_INIT_INETSOCK_IMPL`

* Introduction of Happy Eyeballs Version 2 (RFC8305) in TCPSocket.new

This is an implementation of Happy Eyeballs version 2 (RFC 8305) in `TCPSocket.new`.
See https://github.com/ruby/ruby/pull/11653

1. Background
Prior to this implementation, I implemented Happy Eyeballs Version 2 (HEv2) for `Socket.tcp` in https://github.com/ruby/ruby/pull/9374.
HEv2 is an algorithm defined in [RFC 8305](https://datatracker.ietf.org/doc/html/rfc8305), aimed at improving network connectivity.
For more details on the specific cases that HEv2 helps, please refer to https://bugs.ruby-lang.org/issues/20108.

2. Proposal & Outcome
This proposal implements the same HEv2 algorithm in `TCPSocket.new`.
Since `TCPSocket.new` is used more widely than `Socket.tcp`, this change is expected to broaden the impact of HEv2's benefits.
Like `Socket.tcp`, I have also added `fast_fallback` keyword argument to `TCPSocket.new`.
This option is set to true by default, enabling the HEv2 functionality.
However, users can explicitly set it to false to disable HEv2 and use the previous behavior of `TCPSocket.new`.

It should be noted that HEv2 is enabled only in environments where pthreads are available.
This specification follows the approach taken in https://bugs.ruby-lang.org/issues/19965 , where name resolution can be interrupted.
(In environments where pthreads are not available, the `fast_fallback` option is ignored.)

3. Performance
Below is the benchmark of 100 requests to `www.ruby-lang.org` with the fast_fallback option set to true and false, respectively.
While there is a slight performance degradation when HEv2 is enabled, the degradation is smaller compared to that seen in `Socket.tcp`.

```
~/s/build ❯❯❯ ../install/bin/ruby ../ruby/test.rb
Rehearsal --------------------------------------------------------
fast_fallback: true    0.017588   0.097045   0.114633 (  1.460664)
fast_fallback: false   0.014033   0.078984   0.093017 (  1.413951)
----------------------------------------------- total: 0.207650sec

                           user     system      total        real
fast_fallback: true    0.020891   0.124054   0.144945 (  1.473816)
fast_fallback: false   0.018392   0.110852   0.129244 (  1.466014)
```

* Update debug prints

Co-authored-by: Nobuyoshi Nakada <nobu.nakada@gmail.com>

* Remove debug prints

* misc

* Disable HEv2 in Win

* Raise resolution error with hostname resolution

* Fix to handle errors

* Remove warnings

* Errors that do not need to be handled

* misc

* Improve doc

* Fix bug on cancellation

* Avoid EAI_ADDRFAMILY for resolving IPv6

* Follow upstream

* misc

* Refactor connection_attempt_fds management

- Introduced allocate_connection_attempt_fds and reallocate_connection_attempt_fds for improved memory allocation of connection_attempt_fds
- Added remove_connection_attempt_fd to resize connection_attempt_fds dynamically.
- Simplified the in_progress_fds function to only check the size of connection_attempt_fds.

* Rename do_pthread_create to raddrinfo_pthread_create to avoid conflicting

---------

Co-authored-by: Nobuyoshi Nakada <nobu.nakada@gmail.com>

[Misc #18891]

Add connect_timeout to TCPSocket.new in the same way as Socket.tcp.

Closes [Feature #17187]

* ext/socket/init.c (rsock_s_accept_nonblock): avoid parsing args
  [ruby-core:71439] [Feature #11339]
* ext/socket/rubysocket.h: adjust prototype
* ext/socket/socket.c (sock_accept_nonblock): make private
* ext/socket/tcpserver.c (tcp_accept_nonblock): ditto
* ext/socket/unixserver.c (unix_accept_nonblock): ditto
* ext/socket/lib/socket.rb (Socket#accept_nonblock):
  implement as wrapper, move RDoc
  (TCPServer#accept_nonblock): ditto
  (UNIXServer#accept_nonblock): ditto

target 0: a (ruby 2.3.0dev (2015-11-12 trunk 52550) [x86_64-linux])
target 1: b (ruby 2.3.0dev (2015-11-12 avoid-kwarg-capi 52550) [x86_64-linux]

-----------------------------------------------------------
accept_nonblock

require 'tempfile'
require 'socket'
require 'io/wait'
nr = 500000
Tempfile.create(%w(accept_nonblock .sock)) do |tmp|
  path = tmp.path
  File.unlink(path)
  s = UNIXServer.new(path)
  addr = Socket.sockaddr_un(path).freeze
  nr.times do
    s.accept_nonblock(exception: false)
    c = UNIXSocket.new(path)
    s.wait_readable
    s.accept_nonblock(exception: false).close
    c.close
  end
end

-----------------------------------------------------------
raw data:

[["accept_nonblock",
  [[4.807877402752638,
    4.930681671947241,
    4.738454818725586,
    4.69268161803484,
    4.684675686061382],
   [4.253904823213816,
    4.255124930292368,
    4.295955188572407,
    4.248479191213846,
    4.213303029537201]]]]

Elapsed time: 45.123040065 (sec)
-----------------------------------------------------------
benchmark results:
minimum results in each 5 measurements.
Execution time (sec)
name            a       b
accept_nonblock   4.685   4.213

Speedup ratio: compare with the result of `a' (greater is better)
name            b
accept_nonblock   1.112

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52601 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

* ext/socket/socket.c: ditto

* ext/socket/tcpserver.c: ditto

* ext/socket/udpsocket.c: ditto

* ext/socket/unixserver.c: ditto

* io.c: ditto

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51221 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

This is analogous to functionality found in IO#read_nonblock and
IO#wait_nonblock.  Raising exceptions for common failures on
non-blocking servers is expensive and makes $DEBUG too noisy.

Benchmark results:
                                    user     system      total        real
default                         2.790000   0.870000   3.660000 (  3.671597)
exception: false                1.120000   0.800000   1.920000 (  1.922032)
exception: false (cached arg)   0.820000   0.770000   1.590000 (  1.589267)
--------------------- benchmark script ------------------------
require 'socket'
require 'benchmark'
require 'tmpdir'
nr = 1000000
Dir.mktmpdir('nb_bench') do |path|
  sock_path = "#{path}/test.sock"
  s = UNIXServer.new(sock_path)
  Benchmark.bmbm do |x|
    x.report("default") do
      nr.times do
        begin
          s.accept_nonblock
        rescue IO::WaitReadable
        end
      end
    end
    x.report("exception: false") do
      nr.times do
        begin
          s.accept_nonblock(exception: false)
        rescue IO::WaitReadable
          abort "should not raise"
        end
      end
    end
    x.report("exception: false (cached arg)") do
      arg = { exception: false }
      nr.times do
        begin
          s.accept_nonblock(arg)
        rescue IO::WaitReadable
          abort "should not raise"
        end
      end
    end
  end
end

* ext/socket/init.c (rsock_s_accept_nonblock):
  support exception: false
  [ruby-core:66385] [Feature #10532]
* ext/socket/init.c (rsock_init_socket_init): define new symbols
* ext/socket/rubysocket.h: adjust prototype
* ext/socket/socket.c (sock_accept_nonblock): support exception: false
* ext/openssl/ossl_ssl.c (ossl_ssl_accept_nonblock): ditto
* ext/socket/socket.c (Init_socket): adjust accept_nonblock definition
* ext/openssl/ossl_ssl.c (Init_ossl_ssl): ditto
* ext/socket/tcpserver.c (rsock_init_tcpserver): ditto
* ext/socket/unixserver.c (rsock_init_unixserver): ditto
* ext/socket/tcpserver.c (tcp_accept_nonblock): adjust
  rsock_s_accept_nonblock call
* ext/socket/unixserver.c (unix_accept_nonblock): ditto
* ext/openssl/ossl_ssl.c (ossl_start_ssl): support no_exception
* ext/openssl/ossl_ssl.c (ossl_ssl_connect): adjust ossl_start_ssl call
* ext/openssl/ossl_ssl.c (ossl_ssl_connect_nonblock): ditto
* ext/openssl/ossl_ssl.c (ossl_ssl_accept): ditto
* test/socket/test_nonblock.rb (test_accept_nonblock): test for
  "exception :false"
* test/socket/test_tcp.rb (test_accept_nonblock): new test
* test/socket/test_unix.rb (test_accept_nonblock): ditto
* test/openssl/test_pair.rb (test_accept_nonblock_no_exception): ditto

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49948 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

* ext/socket/tcpserver.c: ditto
* ext/socket/udpsocket.c: [DOC] Fix indentation of documentation
* ext/socket/socket.c: ditto
  Patches by David Rodríguez [ruby-core:56734] [Bug #8802]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42629 b2dd03c8-39d4-4d8f-98ff-823fe69b080e