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

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:
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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...

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

[Ken Brown]

On 5/30/2016 7:44 PM, Francis Litterio wrote:
>
> 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)))

What happens if you add
                                            :family 'ipv6

Ken

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

[Fran]

I see the exact same failure with ":family 'ipv6" added to the
arguments to make-network-connection (when it's also passed ":host
ipv6-host", of course).
--
Fran Litterio

On Wed, Jun 1, 2016 at 10:54 AM, Ken Brown <kbrown@cornell.edu> wrote:
> On 5/30/2016 7:44 PM, Francis Litterio wrote:
>>
>>
>> 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)))
>
>
> What happens if you add
>                                            :family 'ipv6
>
> Ken
>

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

[Ken Brown]

On 6/1/2016 11:30 AM, Fran wrote:
> I see the exact same failure with ":family 'ipv6" added to the
> arguments to make-network-connection (when it's also passed ":host
> ipv6-host", of course).

And what if you remove the ":nowait t"?

Ken

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

[Fran]

Removing the ":nowait t" makes it connect successfully to the IPv6
address. In that case, it works regardless of whether ":family 'ipv6"
is present. If this were my personal code that would be a sufficient
workaround, but I found this bug in ERC (the Emacs IRC client), and I
think it is designed so that make-network-process has to connect
asynchronously.
--
Fran Litterio


On Wed, Jun 1, 2016 at 12:29 PM, Ken Brown <kbrown@cornell.edu> wrote:
> On 6/1/2016 11:30 AM, Fran wrote:
>>
>> I see the exact same failure with ":family 'ipv6" added to the
>> arguments to make-network-connection (when it's also passed ":host
>> ipv6-host", of course).
>
>
> And what if you remove the ":nowait t"?
>
> Ken
>

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

[Ken Brown]

On 6/1/2016 3:57 PM, Fran wrote:
> Removing the ":nowait t" makes it connect successfully to the IPv6
> address. In that case, it works regardless of whether ":family 'ipv6"
> is present. If this were my personal code that would be a sufficient
> workaround, but I found this bug in ERC (the Emacs IRC client), and I
> think it is designed so that make-network-process has to connect
> asynchronously.

This sounds similar to the situation I faced in bug#23606.  (But in that 
case specifying :family solved the problem).  Here's what I suspect is 
happening:

In src/process.c there's a loop starting at line 3138 in which the code 
runs through a list of possible addrinfo structures in the hopes of 
finding one it can connect to.  In the asynchronous case, it doesn't 
wait to see if the connection is successful; this is only discovered 
later (around line 5495).  At this point it's too late to try another 
addrinfo structure, and a "failed" message is generated (line 5523) if 
the connection didn't succeed.

I think it would be better if the loop would delay making the connection 
asynchronous (line 3160 or 3171) until it's known that the connection 
has succeeded.

Lars, is there any reason not to do it that way?

Ken

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

[Ken Brown]

On 6/1/2016 5:55 PM, Ken Brown wrote:
> On 6/1/2016 3:57 PM, Fran wrote:
>> Removing the ":nowait t" makes it connect successfully to the IPv6
>> address. In that case, it works regardless of whether ":family 'ipv6"
>> is present. If this were my personal code that would be a sufficient
>> workaround, but I found this bug in ERC (the Emacs IRC client), and I
>> think it is designed so that make-network-process has to connect
>> asynchronously.
> 
> This sounds similar to the situation I faced in bug#23606.  (But in that
> case specifying :family solved the problem).  Here's what I suspect is
> happening:
> 
> In src/process.c there's a loop starting at line 3138 in which the code
> runs through a list of possible addrinfo structures in the hopes of
> finding one it can connect to.  In the asynchronous case, it doesn't
> wait to see if the connection is successful; this is only discovered
> later (around line 5495).  At this point it's too late to try another
> addrinfo structure, and a "failed" message is generated (line 5523) if
> the connection didn't succeed.

While we're waiting for an expert to respond to this, it's easy to test if my guess is correct.  Please apply the following patch, rebuild, and retry your tests.

diff --git a/src/process.c b/src/process.c
index 9ca3e594..30a200f 100644
--- a/src/process.c
+++ b/src/process.c
@@ -3135,6 +3135,7 @@ connect_network_socket (Lisp_Object proc, Lisp_Object addrinfos,
   count1 = SPECPDL_INDEX ();
   s = -1;
 
+  int addrinfo_count = 0;
   while (!NILP (addrinfos))
     {
       Lisp_Object addrinfo = XCAR (addrinfos);
@@ -3142,6 +3143,8 @@ connect_network_socket (Lisp_Object proc, Lisp_Object addrinfos,
       int protocol = XINT (XCAR (addrinfo));
       Lisp_Object ip_address = XCDR (addrinfo);
 
+      message ("Trying addrinfo structure %d", ++addrinfo_count);
+
 #ifdef WINDOWSNT
     retry_connect:
 #endif

This will print a message in the echo area (and the *Messages* buffer) on each iteration of the loop.  If my guess is correct, you should see more than one iteration in the IPv6 case if ":nowait t" is removed.  It would also be interesting to see if ":family 'ipv6" has any effect, again without ":nowait t".

Ken

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

[Fran Litterio]

Ken Brown <kbrown <at> cornell.edu> writes:

> While we're waiting for an expert to respond to this, it's easy
> to test if my guess is correct.  Please apply
> the following patch, rebuild, and retry your tests.

[snip]

> This will print a message in the echo area (and the *Messages*
> buffer) on each iteration of the loop.  If my guess is correct,
> you should see more than one iteration in the IPv6 case if
> ":nowait t" is removed.  It would also be interesting to see
> if ":family 'ipv6" has any effect, again without ":nowait t".
> 
> Ken

Thanks, Ken.  Sorry to delay on this (work intrudes, as it does).
I'll try this experiment this weekend and report back.
--
Fran Litterio

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

[Fran Litterio]

Ken Brown <kbrown <at> cornell.edu> writes:

> While we're waiting for an expert to respond to this, it's
> easy to test if my guess is correct.  Please apply
> the following patch, rebuild, and retry your tests.

Hi Ken,

Unfortunately, your patch doesn't apply cleanly.  My source near
those lines no longer looks like the context in your patch.
In particular, I no longer have a call to connect_network_socket
at line 3142.  I see this commit by Paul Eggert in my source:

commit 918ef71538fd43049496e4370eba63e3096a4933
Author: Paul Eggert <eggert@cs.ucla.edu>
Date:   Mon May 23 08:56:42 2016 -0700

  Don't use only last protocol from getaddrinfo
    
  Problem reported by Ken Brown in:
  http://lists.gnu.org/archive/html/emacs-devel/2016-05/msg00483.html
  * src/process.c (conv_addrinfo_to_lisp): New function.
  (connect_network_socket): Arg is now a list of addrinfos, not
  merely IP addresses.  All uses changed.  Use protocol from
  each addrinfo.
  (Fmake_network_process): Accumulate protocols into addrinfos
  rather than just using the last one found.
  (check_for_dns): Accumulate protocols here, too.
  * src/process.h (struct Lisp_Process): Remove ai_protocol;
  no longer needed.

I built Emacs from source containing that commit, but it didn't fix
the problem.  Let me know if there's any more I can do to help.  I
will leave my local repo in the state where the above commit is
the most recent commit to src/process.c, in case you need me to
try another patch.
--
Fran Litterio

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

[Ken Brown]

[-- Attachment #1: Type: text/plain, Size: 562 bytes --]

On 6/5/2016 11:04 AM, Fran Litterio wrote:
> Ken Brown <kbrown <at> cornell.edu> writes:
>
>> While we're waiting for an expert to respond to this, it's
>> easy to test if my guess is correct.  Please apply
>> the following patch, rebuild, and retry your tests.
>
> Hi Ken,
>
> Unfortunately, your patch doesn't apply cleanly.

Hi Fran,

It applies cleanly for me to the current git HEAD.  Could you do a 'git 
pull' and try again?  I'm resending the patch as an attachment in case 
my mailer (or yours) messed something up, e.g., by wrapping a long line.

Ken


[-- Attachment #2: process.c.patch --]
[-- Type: text/plain, Size: 654 bytes --]

diff --git a/src/process.c b/src/process.c
index 9ca3e594..30a200f 100644
--- a/src/process.c
+++ b/src/process.c
@@ -3135,6 +3135,7 @@ connect_network_socket (Lisp_Object proc, Lisp_Object addrinfos,
   count1 = SPECPDL_INDEX ();
   s = -1;
 
+  int addrinfo_count = 0;
   while (!NILP (addrinfos))
     {
       Lisp_Object addrinfo = XCAR (addrinfos);
@@ -3142,6 +3143,8 @@ connect_network_socket (Lisp_Object proc, Lisp_Object addrinfos,
       int protocol = XINT (XCAR (addrinfo));
       Lisp_Object ip_address = XCDR (addrinfo);
 
+      message ("Trying addrinfo structure %d", ++addrinfo_count);
+
 #ifdef WINDOWSNT
     retry_connect:
 #endif

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

[Fran]

On Sun, Jun 5, 2016 at 11:31 AM, Ken Brown <kbrown@cornell.edu> wrote:
> On 6/5/2016 11:04 AM, Fran Litterio wrote:
>
>> Unfortunately, your patch doesn't apply cleanly.
>
>
> Hi Fran,
>
> It applies cleanly for me to the current git HEAD.  Could you do a 'git
> pull' and try again?  I'm resending the patch as an attachment in case my
> mailer (or yours) messed something up, e.g., by wrapping a long line.

This time it applied cleanly. Rebuilding now. Will update.
--
Fran

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

[Fran]

On Thu, Jun 2, 2016 at 10:50 AM, Ken Brown <kbrown@cornell.edu> wrote:
> On 6/1/2016 5:55 PM, Ken Brown wrote:

> While we're waiting for an expert to respond to this, it's easy to
> test if my guess is correct.  Please apply the following patch,
> rebuild, and retry your tests.

[...]

> This will print a message in the echo area (and the *Messages* buffer)
> on each iteration of the loop.  If my guess is correct, you should see
> more than one iteration in the IPv6 case if ":nowait t" is removed.
> It would also be interesting to see if ":family 'ipv6" has any effect,
> again without ":nowait t".

I did a "git pull", applied that patch, and rebuilt.  I see the
following in *Messages* no matter if ":nowait t" or ":family 'ipv6" is
present or absent (I tried all four combinations):

    Trying addrinfo structure 1

I never see that message with the value 2 in it.
--
Fran

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

[Ken Brown]

On 6/5/2016 12:56 PM, Fran wrote:
> On Thu, Jun 2, 2016 at 10:50 AM, Ken Brown <kbrown@cornell.edu> wrote:
>> On 6/1/2016 5:55 PM, Ken Brown wrote:
>
>> While we're waiting for an expert to respond to this, it's easy to
>> test if my guess is correct.  Please apply the following patch,
>> rebuild, and retry your tests.
>
> [...]
>
>> This will print a message in the echo area (and the *Messages* buffer)
>> on each iteration of the loop.  If my guess is correct, you should see
>> more than one iteration in the IPv6 case if ":nowait t" is removed.
>> It would also be interesting to see if ":family 'ipv6" has any effect,
>> again without ":nowait t".
>
> I did a "git pull", applied that patch, and rebuilt.  I see the
> following in *Messages* no matter if ":nowait t" or ":family 'ipv6" is
> present or absent (I tried all four combinations):
>
>     Trying addrinfo structure 1
>
> I never see that message with the value 2 in it.

OK, my guess was wrong.  I'm out of ideas.  I hope one of the experts 
can help you.

Ken

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

[Ken Brown]

On 6/5/2016 1:20 PM, Ken Brown wrote:
> OK, my guess was wrong.  I'm out of ideas.  I hope one of the experts
> can help you.

One last thought: Your original report mentioned an error code of 14.  That may be bogus, for the reasons explained in bug#23615.  The following patch might get a more reliable error code, which you could then look up.  (On my system you would look in /usr/include/sys/errno.h.)

diff --git a/src/process.c b/src/process.c
index 9ca3e594..d71c50c 100644
--- a/src/process.c
+++ b/src/process.c
@@ -5492,7 +5492,7 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
 
              p = XPROCESS (proc);
 
-#ifdef GNU_LINUX
+#if 1
              /* getsockopt(,,SO_ERROR,,) is said to hang on some systems.
                 So only use it on systems where it is known to work.  */
              {


Ken

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

[Ken Brown]

On 6/5/2016 2:00 PM, Ken Brown wrote:
> On 6/5/2016 1:20 PM, Ken Brown wrote:
>> OK, my guess was wrong.  I'm out of ideas.  I hope one of the experts
>> can help you.
>
> One last thought: Your original report mentioned an error code of 14.  That may be bogus, for the reasons explained in bug#23615.  The following patch might get a more reliable error code, which you could then look up.  (On my system you would look in /usr/include/sys/errno.h.)
>
> diff --git a/src/process.c b/src/process.c
> index 9ca3e594..d71c50c 100644
> --- a/src/process.c
> +++ b/src/process.c
> @@ -5492,7 +5492,7 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
>
>               p = XPROCESS (proc);
>
> -#ifdef GNU_LINUX
> +#if 1
>               /* getsockopt(,,SO_ERROR,,) is said to hang on some systems.
>                  So only use it on systems where it is known to work.  */
>               {

Fran, you may want to try the patch that Paul recently posted to 
bug#17976.  This may help with your problem.

Ken

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

[Ken Brown]

On 6/12/2016 4:04 PM, Ken Brown wrote:
> On 6/5/2016 2:00 PM, Ken Brown wrote:
>> On 6/5/2016 1:20 PM, Ken Brown wrote:
>>> OK, my guess was wrong.  I'm out of ideas.  I hope one of the experts
>>> can help you.
>>
>> One last thought: Your original report mentioned an error code of 14.
>> That may be bogus, for the reasons explained in bug#23615.  The
>> following patch might get a more reliable error code, which you could
>> then look up.  (On my system you would look in /usr/include/sys/errno.h.)
>>
>> diff --git a/src/process.c b/src/process.c
>> index 9ca3e594..d71c50c 100644
>> --- a/src/process.c
>> +++ b/src/process.c
>> @@ -5492,7 +5492,7 @@ wait_reading_process_output (intmax_t
>> time_limit, int nsecs, int read_kbd,
>>
>>               p = XPROCESS (proc);
>>
>> -#ifdef GNU_LINUX
>> +#if 1
>>               /* getsockopt(,,SO_ERROR,,) is said to hang on some
>> systems.
>>                  So only use it on systems where it is known to work.  */
>>               {
>
> Fran, you may want to try the patch that Paul recently posted to
> bug#17976.  This may help with your problem.

On second thought, the part of Paul's patch that I thought might help 
doesn't seem to apply to MS-Windows.  I'm not sure how hard it would be 
to extend it to Windows.

Ken

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

[Live System User]

Hi,

        I get an Emacs crash (see bug#23669).

Thanks.

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

[Ken Brown]

On 6/2/2016 4:16 AM, Live System User wrote:
>         I get an Emacs crash (see bug#23669).

Sorry, but I can't reproduce this on my system (Cygwin), and I'm not 
skilled enough to walk you through debugging it.

Maybe someone else can help.

Ken

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

[Lars Ingebrigtsen]

flitterio@gmail.com (Francis Litterio) writes:

> 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:

(I have only skimmed this thread.)

The last update to this bug report was four years ago.  Some work on
this problem was done in this bug report, but it's unclear whether any
problems remain, and I can't recall seeing any bug reports about ipv6 on
Windows lately.

So has this problem been resolved by now?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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

[Lars Ingebrigtsen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> The last update to this bug report was four years ago.  Some work on
> this problem was done in this bug report, but it's unclear whether any
> problems remain, and I can't recall seeing any bug reports about ipv6 on
> Windows lately.
>
> So has this problem been resolved by now?

This was five weeks ago, and there was no response, so I'm closing this
bug report.  If this is still a problem, please respond to the debbugs
mail address, and we'll reopen the bug report.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no