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From: Robert Pluim <rpluim@gmail.com>
To: Robin Tarsiger <rtt@dasyatidae.com>
Cc: Eli Zaretskii <eliz@gnu.org>, emacs-devel@gnu.org
Subject: Re: ai_flags in calls to getaddrinfo, broader call for reproducibility check
Date: Mon, 11 Jan 2021 19:42:02 +0100	[thread overview]
Message-ID: <8735z748p1.fsf@gmail.com> (raw)
In-Reply-To: <5cb6a0ac-9fe9-bfc2-5642-3423bd043238@dasyatidae.com> (Robin Tarsiger's message of "Mon, 11 Jan 2021 12:30:22 -0600")

[-- Attachment #1: Type: text/plain, Size: 1727 bytes --]

Robin Tarsiger <rtt@dasyatidae.com> writes:

> Robert Pluim wrote:
>>> There is no _reliable_ way I know of to determine this programmatically,
>>> certainly not without sending some probe queries with a high level of
>>> specific control over them, and I expect that would be a rather hairy
>>> thing to do just for a few tests, and not reasonably maintainable.
>> 
>> (require 'dns)
>> (skip-unless (dns-query "google.com" 'AAAA))
>
> Oh, wow, there's _already_ a dns.el in core? Huh. Well, that obviates
> my primary concerns about doing direct DNS probes, provided it works
> and is a reasonable thing to load for the test suite otherwise...
>
>> and then do the network-lookup-address-info tests (although on Windows
>> this depends on DNS over TCP working,
>
> Ergh. I just checked with `dig +tcp` against my crappy ISP CPE and it
> rejects the connection, which seems like anecdata toward that failing
> in a lot of configurations.
>

Yep.

> Do you happen to know OTTOYH _why_ datagram sockets aren't supported
> in Emacs on Windows to start with... ?
>

Because the select implementation on windows does a one-byte readahead
to see if data is available, which breaks UDP. I had a patch at one
point to fix this, but I remember Eli not being very enthusiastic
about it. Iʼve attached what I think is the right version below (my
windows box died, so I can't be sure)

>> and either /etc/resolv.conf or a
>> working nslookup).
> The latter should at least be stock on Windows AFAIK. I'd forgotten that
> it shows the list of resolver addresses too.

Itʼs my least preferred option, it depends on running an external
binary and parsing the output, which is fragile.

Robert


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: sys_select_improvement.patch --]
[-- Type: text/x-diff, Size: 1745 bytes --]

diff --git i/src/w32.c w/src/w32.c
index 698e10e234..d14abc2f8e 100644
--- i/src/w32.c
+++ w/src/w32.c
@@ -8798,6 +8798,37 @@ _sys_wait_accept (int fd)
   return cp->status;
 }
 
+int
+_sys_wait_readable (int fd)
+{
+  HANDLE hEv;
+  child_process * cp;
+  int rc;
+
+  if (fd < 0 || fd >= MAXDESC)
+    return STATUS_READ_ERROR;
+
+  cp = fd_info[fd].cp;
+
+  if (cp == NULL || cp->fd != fd || cp->status != STATUS_READ_READY)
+    return STATUS_READ_ERROR;
+
+  cp->status = STATUS_READ_FAILED;
+
+  hEv = pfn_WSACreateEvent ();
+  rc = pfn_WSAEventSelect (SOCK_HANDLE (fd), hEv, FD_READ);
+  if (rc != SOCKET_ERROR)
+    {
+	rc = WaitForSingleObject (hEv, INFINITE);
+        pfn_WSAEventSelect (SOCK_HANDLE (fd), NULL, 0);
+        if (rc == WAIT_OBJECT_0)
+          cp->status = STATUS_READ_SUCCEEDED;
+    }
+  pfn_WSACloseEvent (hEv);
+
+  return cp->status;
+}
+
 int
 _sys_wait_connect (int fd)
 {
diff --git i/src/w32.h w/src/w32.h
index cf1dadf64c..4a6b7c4b53 100644
--- i/src/w32.h
+++ w/src/w32.h
@@ -175,6 +175,7 @@ #define FILE_SERIAL             0x0800
 
 extern int _sys_read_ahead (int fd);
 extern int _sys_wait_accept (int fd);
+extern int _sys_wait_readable (int fd);
 extern int _sys_wait_connect (int fd);
 
 extern HMODULE w32_delayed_load (Lisp_Object);
diff --git i/src/w32proc.c w/src/w32proc.c
index de33726905..1e109669f7 100644
--- i/src/w32proc.c
+++ w/src/w32proc.c
@@ -1225,7 +1225,7 @@ reader_thread (void *arg)
       else if (cp->fd >= 0 && (fd_info[cp->fd].flags & FILE_LISTEN) != 0)
 	rc = _sys_wait_accept (cp->fd);
       else
-	rc = _sys_read_ahead (cp->fd);
+	rc = _sys_wait_readable (cp->fd);
 
       /* Don't bother waiting for the event if we already have been
 	 told to exit by delete_child.  */

  reply	other threads:[~2021-01-11 18:42 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-31 15:06 ai_flags in calls to getaddrinfo Eli Zaretskii
2020-12-31 22:40 ` Robin Tarsiger
2021-01-01  7:43   ` Eli Zaretskii
2021-01-01 11:40     ` Robin Tarsiger
2021-01-01 12:04       ` Robin Tarsiger
2021-01-01 12:48       ` Eli Zaretskii
2021-01-02  0:19         ` Robin Tarsiger
2021-01-03 16:00   ` Eli Zaretskii
2021-01-11 10:47     ` ai_flags in calls to getaddrinfo, broader call for reproducibility check Robin Tarsiger
2021-01-11 12:42       ` Robert Pluim
2021-01-11 15:25       ` Eli Zaretskii
2021-01-11 15:47         ` Robert Pluim
2021-01-11 16:44           ` Eli Zaretskii
2021-01-11 17:07             ` Robin Tarsiger
2021-01-11 17:53               ` Robert Pluim
2021-01-11 18:30                 ` Robin Tarsiger
2021-01-11 18:42                   ` Robert Pluim [this message]
2021-01-11 19:28                     ` Stefan Monnier
2021-01-11 20:12                       ` Robert Pluim
2021-01-11 20:41                         ` Eli Zaretskii
2021-01-11 20:55                           ` Stefan Monnier
2021-01-11 21:02                           ` Robert Pluim
2021-01-11 21:09                             ` Lars Ingebrigtsen
2021-01-11 21:15                               ` Robert Pluim
2021-01-11 22:42                                 ` Lars Ingebrigtsen
2021-01-12  9:40                                   ` Robert Pluim
2021-01-12 12:49                                     ` Lars Ingebrigtsen
2021-01-12 13:04                                       ` Robert Pluim
2021-01-12 14:08                                         ` Lars Ingebrigtsen
2021-01-12 14:29                                           ` Robert Pluim
2021-01-12 18:06                                             ` Lars Ingebrigtsen
2021-01-12 15:14                                       ` Stefan Monnier
2021-01-12 15:45                                         ` Eli Zaretskii
2021-01-12  3:29                             ` Eli Zaretskii
2021-01-11 20:46                 ` Eli Zaretskii
2021-01-11 20:56                   ` Robert Pluim
2021-01-12 15:01                     ` Eli Zaretskii
2021-01-12 15:36                       ` Robert Pluim
2021-01-12 15:42                       ` Eli Zaretskii
2021-01-12 16:00                         ` Robert Pluim
2021-01-12 16:05                           ` Eli Zaretskii
2021-01-12 17:56                             ` Robert Pluim
2021-01-11 19:32           ` Basil L. Contovounesios
2021-01-11 20:19             ` Robert Pluim
2021-01-11 23:57           ` Andy Moreton
2021-01-12  9:44             ` Robert Pluim
2021-01-12 11:56               ` tomas
2021-01-01 10:59 ` ai_flags in calls to getaddrinfo Lars Ingebrigtsen
2021-01-01 12:50   ` Eli Zaretskii
2021-01-02  5:40     ` Lars Ingebrigtsen

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