bug#23658: 25.1.50; make-network-connection fails to connect to IPv6 address on Windows

[Francis Litterio]

Using Emacs built from the latest sources (obtained by cloning the Git
repo at git://git.savannah.gnu.org/emacs.git), make-network-connection
fails when connecting to an IPv6 address from a Windows machine that has
an IPv6 address assigned via DHCP.  To reproduce:

1. On Windows 7 SP1 (with all updates installed), launch Emacs using:
   emacs.exe -Q

2. Evaluate the following form in the *scratch* buffer:

   (progn
     (defun my-sentinel (proc event)
       (with-current-buffer "*scratch*"
         (save-excursion
           (goto-char (point-max))
           (insert (format "\n>> proc = '%s', status = '%s', event = '%s'"
                           proc (process-status proc) event)))))

     (defun my-filter (proc str)
       (with-current-buffer "*scratch*"
         (save-excursion
           (goto-char (point-max))
           (insert (format "\n>> proc = '%s', status = '%s', str = '%s'"
                           proc (process-status proc) str)))))

     ;; These IP addresses are both for host rajaniemi.freenode.net.
     (let* ((ipv6-host "2001:708:40:2001:a822:baff:fec4:2428")
            (ipv4-host "195.148.124.79")
            (process (make-network-process :name "zzz"
                                           :buffer nil
                                           :host ipv6-host
                                           ;; :host ipv4-host
                                           :service 6667
                                           :nowait t)))
       (set-process-sentinel process 'my-sentinel)
       (set-process-filter process 'my-filter)))

3. The following text will appear at the end of the *scratch* buffer
   (inserted by function my-sentinel, above):

    >> proc = 'zzz', status = 'failed', event = 'failed with code 14
    '

4. If you change "ipv6-host" to "ipv4-host" in the call to
   make-network-process, the connection is established successfully, and
   you see the data sent by the IRC server accumulate at the end of the
   *scratch* buffer (inserted by function my-filter, above).

My local system has an IPv6 address, but I'm not sure if that is
required for this problem to happen.
--
Fran Litterio



In GNU Emacs 25.1.50.1 (i686-pc-mingw32)
 of 2016-05-28 built on PUPPY
Repository revision: 549470fdf234acb4da7941e3bb9b28ed63a51876
Windowing system distributor 'Microsoft Corp.', version 6.1.7601
Recent messages:
Quit
Mark set
File 'my-erc.el' has changed!  Reload ~/.emacs! [2 times]
Type "q" to delete help window.
C-M-d runs the command my-kill-to-bottom
File 'my-erc.el' has changed!  Reload ~/.emacs!
Making completion list...
report-emacs-bug is on <menu-bar> <help-menu> <send-emacs-bug-report>
funcall-interactively: Beginning of buffer
Making completion list...

Configured using:
 'configure --prefix=/c/apps/emacs --without-x --without-xpm
 --without-png --without-jpeg --without-tiff --without-gif'

Configured features:
SOUND NOTIFY ACL TOOLKIT_SCROLL_BARS

Important settings:
  value of $LANG: C.ISO-8859-1
  locale-coding-system: cp1252

Major mode: Buffer Menu

Minor modes in effect:
  erc-list-mode: t
  erc-menu-mode: t
  erc-ring-mode: t
  erc-networks-mode: t
  erc-pcomplete-mode: t
  erc-track-mode: t
  erc-track-minor-mode: t
  erc-match-mode: t
  erc-button-mode: t
  erc-fill-mode: t
  erc-netsplit-mode: t
  erc-irccontrols-mode: t
  erc-noncommands-mode: t
  erc-move-to-prompt-mode: t
  erc-readonly-mode: t
  diff-auto-refine-mode: t
  show-paren-mode: t
  save-place-mode: t
  icomplete-mode: t
  savehist-mode: t
  shell-dirtrack-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t
  abbrev-mode: t

Load-path shadows:
None found.

Features:
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erc-match erc-button erc-fill erc-stamp erc-netsplit erc-goodies erc
erc-backend erc-compat thingatpt source-safe ediff-merg ediff-wind
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Memory information:
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