Submitted upstream: https://github.com/canonical/lightdm/pull/312

diff --git a/src/vnc-server.c b/src/vnc-server.c
index d3500764..00a2fc02 100644
--- a/src/vnc-server.c
+++ b/src/vnc-server.c
@@ -126,18 +126,10 @@ vnc_server_start (VNCServer *server)
 
     g_return_val_if_fail (server != NULL, FALSE);
 
-    g_autoptr(GError) ipv4_error = NULL;
-    priv->socket = open_tcp_socket (G_SOCKET_FAMILY_IPV4, priv->port, priv->listen_address, &ipv4_error);
-    if (ipv4_error)
-        g_warning ("Failed to create IPv4 VNC socket: %s", ipv4_error->message);
-
-    if (priv->socket)
-    {
-        GSource *source = g_socket_create_source (priv->socket, G_IO_IN, NULL);
-        g_source_set_callback (source, (GSourceFunc) read_cb, server, NULL);
-        g_source_attach (source, NULL);
-    }
-
+    // Bind to IPv6 first, as this implies binding to 0.0.0.0 in the
+    // Linux kernel default configuration, which would otherwise cause
+    // IPv6 clients to fail with "Error binding to address [::]:5900:
+    // Address already in use" (#266).
     g_autoptr(GError) ipv6_error = NULL;
     priv->socket6 = open_tcp_socket (G_SOCKET_FAMILY_IPV6, priv->port, priv->listen_address, &ipv6_error);
     if (ipv6_error)
@@ -150,6 +142,18 @@ vnc_server_start (VNCServer *server)
         g_source_attach (source, NULL);
     }
 
+    g_autoptr(GError) ipv4_error = NULL;
+    priv->socket = open_tcp_socket (G_SOCKET_FAMILY_IPV4, priv->port, priv->listen_address, &ipv4_error);
+    if (ipv4_error)
+        g_warning ("Failed to create IPv4 VNC socket: %s", ipv4_error->message);
+
+    if (priv->socket)
+    {
+        GSource *source = g_socket_create_source (priv->socket, G_IO_IN, NULL);
+        g_source_set_callback (source, (GSourceFunc) read_cb, server, NULL);
+        g_source_attach (source, NULL);
+    }
+
     if (!priv->socket && !priv->socket6)
         return FALSE;
 
tion>
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<div class='path'>path: <a href='/guix/log/?id=3d363715fad0ce0fec5f22b29a97dc0fe90b3ebf'>root</a>/<a href='/guix/log/gnu?id=3d363715fad0ce0fec5f22b29a97dc0fe90b3ebf'>gnu</a>/<a href='/guix/log/gnu/build?id=3d363715fad0ce0fec5f22b29a97dc0fe90b3ebf'>build</a>/<a href='/guix/log/gnu/build/bootloader.scm?id=3d363715fad0ce0fec5f22b29a97dc0fe90b3ebf'>bootloader.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/build/bootloader.scm?id=3d363715fad0ce0fec5f22b29a97dc0fe90b3ebf&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-06-24 10:21:06 +0200'>2022-06-24</span></td><td><a href='/guix/commit/gnu/build/bootloader.scm?id=62c86c8391ceb8953ca972498fd75ea9298b85ff'>image: Add support for 32bit UEFI.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/bootloader/grub.scm (grub-efi32-bootloader): New variable.
(install-grub-efi32): New variable.
* gnu/build/bootloader.scm (install-efi): Add a 'targets' keyword
argument.
(install-efi-loader): Likewise.
* gnu/build/image.scm (initialize-efi32-partition): New procedure.
* gnu/packages/bootloaders.scm (grub-efi32): New variable.
* gnu/system/image.scm (esp32-partition): New variable
(efi32-disk-image): New variable.
(efi32-raw-image-type): New variable.
(system-disk-image)[partition-image]: Set '#:grub-efi32' when
calling the partition initializer.

Signed-off-by: Mathieu Othacehe &lt;othacehe@gnu.org&gt;
</span></span></td><td>Denis 'GNUtoo' Carikli</td></tr>
<tr><td><span title='2021-11-12 13:26:52 +0000'>2021-11-12</span></td><td><a href='/guix/commit/gnu/build/bootloader.scm?id=fb3df2011692b2a6fea9f4fefd71dd788453fbae'>build: bootloader: Add GPT support.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/build/bootloader.scm (install-efi-loader): Add GPT support.
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2020-11-03 07:59:59 +0100'>2020-11-03</span></td><td><a href='/guix/commit/gnu/build/bootloader.scm?id=a38d861e571c952f78ca588b50bdcc4adcb0c88c'>system: reconfigure: Use the disk-installer if provided.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes: &lt;https://issues.guix.gnu.org/44101&gt;.

* gnu/build/bootloader.scm (write-file-on-device): Pass 'no-fail flag instead
of 'no-create. Use a latin-1 transcoder.
* guix/scripts/system/reconfigure.scm (install-bootloader-program): Add a
"disk-installer" argument and use it as a fallback.
(install-bootloader): Adapt accordingly.
* gnu/tests/reconfigure.scm (run-install-bootloader-test): Ditto.
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2020-10-05 11:10:35 +0200'>2020-10-05</span></td><td><a href='/guix/commit/gnu/build/bootloader.scm?id=b97b423e3f61c80d5877dadc95b3f316cd61788f'>bootloader: Fix u-boot installation.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a follow-up of f19cf27c2b9ff92e2c0fd931ef7fde39c376adaa. The
bootloader installation must be done on the final disk-image, hence using
"disk-image-installer" instead of "installer" callback.

* gnu/bootloader/u-boot.scm: Turn all installer callbacks into
disk-image-installer callbacks.
* gnu/build/bootloader.scm (write-file-on-device): Open the output file with
'no-truncate and 'no-create options.
* gnu/system/image.scm (with-imported-modules*): Add (gnu build bootloader)
module.
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2020-05-05 16:08:33 +0200'>2020-05-05</span></td><td><a href='/guix/commit/gnu/build/bootloader.scm?id=f8fd1157174fd523d36dcfa756c965a54c30d5ae'>build: bootloader: Add install-efi procedure.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/build/bootloader.scm (install-efi): New procedure copied from (gnu build vm).
(install-efi-loader): New exported procedure, wrapping install-efi.
* gnu/build/vm.scm (initialize-hard-disk): Adapt to use install-efi-loader.
</span></span></td><td>Mathieu Othacehe</td></tr>