client: Allow absolute paths in WAYLAND_DISPLAY
In order to support system compositor instances, it is necessary to
allow clients' wl_display_connect() to find the compositor's listening
socket somewhere outside of XDG_RUNTIME_DIR. For a full account, see
the discussion beginning here:
https://lists.freedesktop.org/archives/wayland-devel/2017-November/035664.html
This change adjusts the client-side connection logic so that, if
WAYLAND_DISPLAY is formatted as an absolute pathname, the socket
connection attempt is made to just $WAYLAND_DISPLAY rather than
usual user-private location $XDG_RUNTIME_DIR/$WAYLAND_DISPLAY.
This change is based on Davide Bettio's submission of the same concept
at:
https://lists.freedesktop.org/archives/wayland-devel/2015-August/023838.html.
v4 changes:
* Improved internal comments and some boundary-condition
error checks in test case.
* Refer to compositor as "Wayland server" rather than "Wayland
display" in wl_display_connect() doxygen comments.
* Remove redundant descriptions of parameter-interpretation
mechanics from wl_display_connect() manpage. Reworked things
to make it clear that 'name' and $WAYLAND_DISLAY are each
capable of encoding absolute server socket paths.
* Remove callout to reference implementation behavior in protocol
documented. In its place there is now a simple statement that
implementations can optionally support absolute socket paths.
v3 changes:
* Added test case.
* Clarified documentation to note that 'name' parameter to wl_display_connect()
can also be an absolute path.
v2 changes:
* Added backward incompatibility note to wl_display_connect() manpage.
* Rephased wl_display_connect() manpage changes to precisely match actual
changed behavior.
* Added mention of new absolute path behavior in wl_display_connect()
doxygen comments.
* Mentioned new absolute path interpretation of WAYLAND_DISPLAY in
protocol documentation.
Signed-off-by: Matt Hoosier <matt.hoosier@gmail.com>
Acked-by: Jonas Ådahl <jadahl@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/doc/man/wl_display_connect.xml b/doc/man/wl_display_connect.xml
index 7e6e05c..dab4ddb 100644
--- a/doc/man/wl_display_connect.xml
+++ b/doc/man/wl_display_connect.xml
@@ -55,15 +55,39 @@
<title>Description</title>
<para><function>wl_display_connect</function> connects to a Wayland socket
that was previously opened by a Wayland server. The server socket must
- be placed in <envar>XDG_RUNTIME_DIR</envar> for this function to
- find it. The <varname>name</varname> argument specifies the name of
+ be placed in <envar>XDG_RUNTIME_DIR</envar> when <envar>WAYLAND_DISPLAY</envar>
+ (or <varname>name</varname>, see below) is a simple name, for this
+ function to find it. The server socket is also allowed to exist at an
+ arbitrary path; usage details follow. See below for compatibility issue
+ details.</para>
+
+ <para>The <varname>name</varname> argument specifies the name of
the socket or <constant>NULL</constant> to use the default (which is
<constant>"wayland-0"</constant>). The environment variable
- <envar>WAYLAND_DISPLAY</envar> replaces the default value. If
- <envar>WAYLAND_SOCKET</envar> is set, this function behaves like
+ <envar>WAYLAND_DISPLAY</envar> replaces the default value.
+
+ If <varname>name</varname> is an absolute path, then that path is used
+ as the Wayland socket to which the connection is attempted. Note that
+ in combination with the default-value behavior described above, this
+ implies that setting <envar>WAYLAND_DISPLAY</envar> to an absolute
+ path will implicitly cause <varname>name</varname> to take on that
+ absolute path if <varname>name</varname> is <constant>NULL</constant>.
+
+ If <envar>WAYLAND_SOCKET</envar> is set, this function behaves like
<function>wl_display_connect_to_fd</function> with the file-descriptor
number taken from the environment variable.</para>
+ <para>Support for interpreting <envar>WAYLAND_DISPLAY</envar> as an
+ absolute path is a change in behavior compared to
+ <function>wl_display_connect</function>'s behavior in versions
+ 1.14 and older of Wayland. It is no longer guaranteed in versions
+ 1.15 and higher that the Wayland socket chosen is equivalent to
+ manually constructing a socket pathname by concatenating
+ <envar>XDG_RUNTIME_DIR</envar> and <envar>WAYLAND_DISPLAY</envar>.
+ Manual construction of the socket path must account for the
+ possibility that <envar>WAYLAND_DISPLAY</envar> contains an absolute
+ path.</para>
+
<para><function>wl_display_connect_to_fd</function> connects to a Wayland
socket with an explicit file-descriptor. The file-descriptor is passed
as argument <varname>fd</varname>.</para>
diff --git a/doc/publican/sources/Protocol.xml b/doc/publican/sources/Protocol.xml
index ba6b5f1..9fdee9a 100644
--- a/doc/publican/sources/Protocol.xml
+++ b/doc/publican/sources/Protocol.xml
@@ -94,7 +94,10 @@
The protocol is sent over a UNIX domain stream socket, where the endpoint
usually is named <systemitem class="service">wayland-0</systemitem>
(although it can be changed via <emphasis>WAYLAND_DISPLAY</emphasis>
- in the environment).
+ in the environment). Beginning in Wayland 1.15, implementations can
+ optionally support server socket endpoints located at arbitrary
+ locations in the filesystem by setting <emphasis>WAYLAND_DISPLAY</emphasis>
+ to the absolute path at which the server endpoint listens.
</para>
<para>
Every message is structured as 32-bit words; values are represented in the
diff --git a/src/wayland-client.c b/src/wayland-client.c
index 8fb2dbd..795b4e9 100644
--- a/src/wayland-client.c
+++ b/src/wayland-client.c
@@ -857,9 +857,17 @@
socklen_t size;
const char *runtime_dir;
int name_size, fd;
+ bool path_is_absolute;
+
+ if (name == NULL)
+ name = getenv("WAYLAND_DISPLAY");
+ if (name == NULL)
+ name = "wayland-0";
+
+ path_is_absolute = name[0] == '/';
runtime_dir = getenv("XDG_RUNTIME_DIR");
- if (!runtime_dir) {
+ if (!runtime_dir && !path_is_absolute) {
wl_log("error: XDG_RUNTIME_DIR not set in the environment.\n");
/* to prevent programs reporting
* "failed to create display: Success" */
@@ -867,25 +875,32 @@
return -1;
}
- if (name == NULL)
- name = getenv("WAYLAND_DISPLAY");
- if (name == NULL)
- name = "wayland-0";
-
fd = wl_os_socket_cloexec(PF_LOCAL, SOCK_STREAM, 0);
if (fd < 0)
return -1;
memset(&addr, 0, sizeof addr);
addr.sun_family = AF_LOCAL;
- name_size =
- snprintf(addr.sun_path, sizeof addr.sun_path,
- "%s/%s", runtime_dir, name) + 1;
+ if (!path_is_absolute) {
+ name_size =
+ snprintf(addr.sun_path, sizeof addr.sun_path,
+ "%s/%s", runtime_dir, name) + 1;
+ } else {
+ /* absolute path */
+ name_size =
+ snprintf(addr.sun_path, sizeof addr.sun_path,
+ "%s", name) + 1;
+ }
assert(name_size > 0);
if (name_size > (int)sizeof addr.sun_path) {
- wl_log("error: socket path \"%s/%s\" plus null terminator"
- " exceeds 108 bytes\n", runtime_dir, name);
+ if (!path_is_absolute) {
+ wl_log("error: socket path \"%s/%s\" plus null terminator"
+ " exceeds %i bytes\n", runtime_dir, name, (int) sizeof(addr.sun_path));
+ } else {
+ wl_log("error: socket path \"%s\" plus null terminator"
+ " exceeds %i bytes\n", name, (int) sizeof(addr.sun_path));
+ }
close(fd);
/* to prevent programs reporting
* "failed to add socket: Success" */
@@ -994,6 +1009,16 @@
* its value will be replaced with the WAYLAND_DISPLAY environment
* variable if it is set, otherwise display "wayland-0" will be used.
*
+ * If \c name is an absolute path, then that path is used as-is for
+ * the location of the socket at which the Wayland server is listening;
+ * no qualification inside XDG_RUNTIME_DIR is attempted.
+ *
+ * If \c name is \c NULL and the WAYLAND_DISPLAY environment variable
+ * is set to an absolute pathname, then that pathname is used as-is
+ * for the socket in the same manner as if \c name held an absolute
+ * path. Support for absolute paths in \c name and WAYLAND_DISPLAY
+ * is present since Wayland version 1.15.
+ *
* \memberof wl_display
*/
WL_EXPORT struct wl_display *
diff --git a/tests/socket-test.c b/tests/socket-test.c
index bb034f4..e970562 100644
--- a/tests/socket-test.c
+++ b/tests/socket-test.c
@@ -26,10 +26,14 @@
#include <errno.h>
#include <string.h>
#include <stdio.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/wait.h>
#include <sys/un.h>
#include <unistd.h>
#include "wayland-client.h"
+#include "wayland-os.h"
#include "wayland-server.h"
#include "test-runner.h"
@@ -173,3 +177,108 @@
wl_display_destroy(d);
}
+
+struct client_create_listener {
+ struct wl_listener listener;
+ struct wl_display *display;
+};
+
+struct client_destroy_listener {
+ struct wl_listener listener;
+ struct wl_display *display;
+};
+
+static void
+client_destroy_notify(struct wl_listener *l, void *data)
+{
+ struct client_destroy_listener *listener =
+ wl_container_of(l, listener, listener);
+ wl_display_terminate(listener->display);
+ free(listener);
+}
+
+static void
+client_create_notify(struct wl_listener *l, void *data)
+{
+ struct wl_client *client = data;
+ struct client_create_listener *listener =
+ wl_container_of(l, listener, listener);
+ struct client_destroy_listener *destroy_listener = (struct client_destroy_listener *)malloc(sizeof *destroy_listener);
+ assert(destroy_listener != NULL);
+ destroy_listener->display = listener->display;
+ destroy_listener->listener.notify = client_destroy_notify;
+ wl_client_add_destroy_listener(client, &destroy_listener->listener);
+}
+
+TEST(absolute_socket_path)
+{
+ struct wl_display *display;
+ struct client_create_listener client_create_listener;
+ struct sockaddr_un addr;
+ int fd;
+ socklen_t size;
+ const char *xdg_runtime_dir;
+ size_t len;
+ int ret;
+ pid_t pid;
+
+ /* It's a little weird that this test about absolute socket paths
+ * uses XDG_RUNTIME_DIR, but that's the only location guaranteed
+ * by test-runner to be both writable and unique. This isn't
+ * really a problem; we'll just take care that the leaf-level
+ * filename used for the socket isn't anything that would
+ * accidentally be generated by a default usage of wl_display_connect(). */
+ xdg_runtime_dir = require_xdg_runtime_dir();
+ memset(&addr, 0, sizeof addr);
+ len = snprintf(addr.sun_path, sizeof addr.sun_path,
+ "%s/%s", xdg_runtime_dir, "wayland-absolute-0");
+ assert(len < sizeof addr.sun_path
+ && "Bug in test. Path too long");
+
+ /* The path must not exist prior to binding. */
+ assert(access(addr.sun_path, F_OK) == -1);
+
+ size = offsetof (struct sockaddr_un, sun_path) + strlen(addr.sun_path);
+ addr.sun_family = AF_LOCAL;
+ fd = wl_os_socket_cloexec(PF_LOCAL, SOCK_STREAM, 0);
+ assert(fd >= 0 );
+ ret = bind(fd, (struct sockaddr *) &addr, size);
+ assert(ret >= 0);
+ ret = listen(fd, 128);
+ assert(ret >= 0);
+
+ /* Start server display. Be careful (by avoiding wl_display_add_socket_auto()
+ * to offer only the absolutely qualified socket made above. */
+ display = wl_display_create();
+ assert(display != NULL);
+ client_create_listener.listener.notify = client_create_notify;
+ client_create_listener.display = display;
+ wl_display_add_client_created_listener(display, &client_create_listener.listener);
+ ret = wl_display_add_socket_fd(display, fd);
+ assert(ret == 0);
+
+ /* Execute client that connects to the absolutely qualified server socket path. */
+ pid = fork();
+ assert(pid != -1);
+
+ if (pid == 0) {
+ ret = setenv("WAYLAND_DISPLAY", addr.sun_path, 1);
+ assert(ret == 0);
+ struct wl_display *client_display = wl_display_connect(NULL);
+ assert(client_display != NULL);
+ ret = wl_display_roundtrip(client_display);
+ assert(ret != -1);
+ wl_display_disconnect(client_display);
+ exit(0);
+ assert(false);
+ }
+
+ wl_display_run(display);
+ ret = waitpid(pid, NULL, 0);
+ assert(ret == pid);
+
+ wl_display_destroy(display);
+
+ ret = unlink(addr.sun_path);
+ assert(ret == 0);
+}
