Re: dbus-daemon on Windows: Failed to bind socket "localhost:59367": Address already in use

Am 03.01.2015 um 01:43 schrieb Thomas Sondergaard:
> On 2015-01-02 23:17, Thomas Sondergaard wrote:
>> When I run the attached test programs I get a handful or so of cases
>> where the dbus-daemon fails to start with a message like
>>
>> Failed to bind socket "localhost:59367": Address already in use
>>
>> This surprises me. First I thought it was some kind of race condition
>> when starting multiple buses at the same time (dbus-test.cc), but it
>> also fails a handful of times out of a thousand when only one process is
>> started at a time (dbus-test-nothreads.cc).
>>
>> This is using D-Bus Message Bus Daemon 1.8.10 on Windows.
>>
>> Steps to reproduce:
>>
>> 1. Compile the small test program on Windows
>> 2. Make sure dbus-daemon is in the path
>> 3. Run the test program
>>
>> The nothreads version takes about 4 minutes to run.
>>
>> Regards,
>> Thomas
>
> I've digged a little further and I think I see a bug in
> _dbus_server_new_for_tcp_socket() in dbus-sysdeps-win.c. If I
> understand _dbus_server_new_for_tcp_socket() it is working hard to
> bind the same port on both IPv4 and IPv6. If it starts with port=0 it
> will do a bind with that and then extract the port number with
> getsockname(), and then it will goto redo_lookup_with_port and do the
> same binds again.
>
> The bug that I'm seeing is that it is not correctly extracting the
> port number that the first bind with port=0 produces. It is doing:
>
> snprintf( portbuf, sizeof( portbuf ) - 1, "%d", addr.AddressIn.sin_port);
>
> which fails to account for sin_port being in network byte order. The
> effect is that subsequent binds will be to another "arbitrary" port
> that may or may not be available.
>
> Just adding ntohs() around addr.AddressIn.sin_port will make the
> function find the correct port, but it wont work as the next bind()
> will then fail with EADDRINUSE.
>
> I compared the Windows and the Unix version of
> _dbus_server_new_for_tcp_socket() and it seems that the two versions
> of the functions have grown apart over time. Perhaps the unix version
> has some tricks that the Windows version needs to learn?
The difference in _dbus_listen_tcp_socket is that the unix version uses
getnameinfo() to fetch the port, which is implemented in the appended
patch for windows too. Can you check if this works ?

Regards
 Ralf

From 2c490e405e7cb2b42047f9c771ef74407b2c429d Mon Sep 17 00:00:00 2001
From: Ralf Habacker <[email protected]>
Date: Sat, 3 Jan 2015 10:08:22 +0100
Subject: [PATCH] Keep fetching of tcp port in sync with unix part.

---
 dbus/dbus-sysdeps-win.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/dbus/dbus-sysdeps-win.c b/dbus/dbus-sysdeps-win.c
index 208e852..d05890e 100644
--- a/dbus/dbus-sysdeps-win.c
+++ b/dbus/dbus-sysdeps-win.c
@@ -1752,19 +1752,24 @@ _dbus_listen_tcp_socket (const char     *host,
              to use the same port */
           if (!port || !strcmp(port, "0"))
             {
-              mysockaddr_gen addr;
-              socklen_t addrlen = sizeof(addr);
-              char portbuf[10];
-
-              if (getsockname(fd, &addr.Address, &addrlen) == SOCKET_ERROR)
+              int result;
+              struct sockaddr_storage addr;
+              socklen_t addrlen;
+              char portbuf[50];
+
+              addrlen = sizeof(addr);
+              result = getsockname(fd, (struct sockaddr*) &addr, &addrlen);
+
+              if (result == -1 ||
+                  (res = getnameinfo ((struct sockaddr*)&addr, addrlen, NULL, 0,
+                                      portbuf, sizeof(portbuf),
+                                      NI_NUMERICHOST)) != 0)
                 {
-                  DBUS_SOCKET_SET_ERRNO ();
                   dbus_set_error (error, _dbus_error_from_errno (errno),
-                                  "Failed to resolve port \"%s:%s\": %s",
-                                  host ? host : "*", port, _dbus_strerror_from_errno());
+                                  "Failed to resolve port \"%s:%s\": %s (%s)",
+                                  host ? host : "*", port, gai_strerror(res), res);
                   goto failed;
                 }
-              snprintf( portbuf, sizeof( portbuf ) - 1, "%d", addr.AddressIn.sin_port );
               if (!_dbus_string_append(retport, portbuf))
                 {
                   dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);