From 5cfd162864213c5247d97ea31cfacce98b1caefc Mon Sep 17 00:00:00 2001

From: David Tardon <dtardon@redhat.com>

Date: Fri, 10 Jun 2022 15:07:01 +0200

Subject: [PATCH] logind-session-dbus: allow to set display name via dbus

Currently, the only way to set display name of a graphical session is to

pass it to CreateSession(). But modern display managers like gdm start

the display server as part of the user session, which means that the

display name isn't known yet when the session is being created. Hence,

let's make it possible to set it later.

(cherry picked from commit 4885d7490b23e08d8444e5a68927ce9ce8727e5a)

Resolves: #2100340

---

 man/org.freedesktop.login1.xml        |  8 ++++++++

 src/login/logind-session-dbus.c       | 29 +++++++++++++++++++++++++++

 src/login/logind-session.c            | 20 ++++++++++++++++++

 src/login/logind-session.h            |  1 +

 src/login/org.freedesktop.login1.conf |  4 ++++

 5 files changed, 62 insertions(+)

diff --git a/man/org.freedesktop.login1.xml b/man/org.freedesktop.login1.xml

index d25287b18b..c11324ee3b 100644

--- a/man/org.freedesktop.login1.xml

+++ b/man/org.freedesktop.login1.xml

@@ -1045,6 +1045,7 @@ node /org/freedesktop/login1/session/1 {

       TakeControl(in  b force);

       ReleaseControl();

       SetType(in  s type);

+      SetDisplay(in  s display);

       TakeDevice(in  u major,

                  in  u minor,

                  out h fd,

@@ -1142,6 +1143,8 @@ node /org/freedesktop/login1/session/1 {

     <variablelist class="dbus-method" generated="True" extra-ref="SetType()"/>

+    <variablelist class="dbus-method" generated="True" extra-ref="SetDisplay()"/>

+

     <variablelist class="dbus-method" generated="True" extra-ref="TakeDevice()"/>

     <variablelist class="dbus-method" generated="True" extra-ref="ReleaseDevice()"/>

@@ -1238,6 +1241,11 @@ node /org/freedesktop/login1/session/1 {

       connection. This should help prevent a session from entering an inconsistent state, for example if the

       controller crashes. The only argument <varname>type</varname> is the new session type.</para>

+      <para><function>SetDisplay()</function> allows the display name of the graphical session to be changed. This is

+      useful if the display server is started as part of the session. It can only be called by session's current

+      controller. If <function>TakeControl()</function> has not been called, this method will fail. The only argument

+      <varname>display</varname> is the new display name.</para>

+

       <para><function>TakeDevice()</function> allows a session controller to get a file descriptor for a

       specific device. Pass in the major and minor numbers of the character device and

       <filename>systemd-logind</filename> will return a file descriptor for the device. Only a limited set of

diff --git a/src/login/logind-session-dbus.c b/src/login/logind-session-dbus.c

index ff4cd0a631..5480d7b2f4 100644

--- a/src/login/logind-session-dbus.c

+++ b/src/login/logind-session-dbus.c

@@ -413,6 +413,30 @@ static int method_set_type(sd_bus_message *message, void *userdata, sd_bus_error

         return sd_bus_reply_method_return(message, NULL);

 }

+static int method_set_display(sd_bus_message *message, void *userdata, sd_bus_error *error) {

+        Session *s = ASSERT_PTR(userdata);

+        const char *display;

+        int r;

+

+        assert(message);

+

+        r = sd_bus_message_read(message, "s", &display);

+        if (r < 0)

+                return r;

+

+        if (!session_is_controller(s, sd_bus_message_get_sender(message)))

+                return sd_bus_error_set(error, BUS_ERROR_NOT_IN_CONTROL, "You must be in control of this session to set display");

+

+        if (!SESSION_TYPE_IS_GRAPHICAL(s->type))

+                return sd_bus_error_set(error, SD_BUS_ERROR_NOT_SUPPORTED, "Setting display is only supported for graphical sessions");

+

+        r = session_set_display(s, display);

+        if (r < 0)

+                return r;

+

+        return sd_bus_reply_method_return(message, NULL);

+}

+

 static int method_take_device(sd_bus_message *message, void *userdata, sd_bus_error *error) {

         Session *s = userdata;

         uint32_t major, minor;

@@ -901,6 +925,11 @@ static const sd_bus_vtable session_vtable[] = {

                                 SD_BUS_NO_RESULT,

                                 method_set_type,

                                 SD_BUS_VTABLE_UNPRIVILEGED),

+        SD_BUS_METHOD_WITH_ARGS("SetDisplay",

+                                SD_BUS_ARGS("s", display),

+                                SD_BUS_NO_RESULT,

+                                method_set_display,

+                                SD_BUS_VTABLE_UNPRIVILEGED),

         SD_BUS_METHOD_WITH_ARGS("TakeDevice",

                                 SD_BUS_ARGS("u", major, "u", minor),

                                 SD_BUS_RESULT("h", fd, "b", inactive),

diff --git a/src/login/logind-session.c b/src/login/logind-session.c

index ab98a5055d..a052596e57 100644

--- a/src/login/logind-session.c

+++ b/src/login/logind-session.c

@@ -1044,6 +1044,26 @@ void session_set_type(Session *s, SessionType t) {

         session_send_changed(s, "Type", NULL);

 }

+int session_set_display(Session *s, const char *display) {

+        int r;

+

+        assert(s);

+        assert(display);

+

+        if (streq(s->display, display))

+                return 0;

+

+        r = free_and_strdup(&s->display, display);

+        if (r < 0)

+                return r;

+

+        session_save(s);

+

+        session_send_changed(s, "Display", NULL);

+

+        return 1;

+}

+

 static int session_dispatch_fifo(sd_event_source *es, int fd, uint32_t revents, void *userdata) {

         Session *s = userdata;

diff --git a/src/login/logind-session.h b/src/login/logind-session.h

index 5c35071dc5..6b6ac2d573 100644

--- a/src/login/logind-session.h

+++ b/src/login/logind-session.h

@@ -137,6 +137,7 @@ int session_set_idle_hint(Session *s, bool b);

 int session_get_locked_hint(Session *s);

 void session_set_locked_hint(Session *s, bool b);

 void session_set_type(Session *s, SessionType t);

+int session_set_display(Session *s, const char *display);

 int session_create_fifo(Session *s);

 int session_start(Session *s, sd_bus_message *properties, sd_bus_error *error);

 int session_stop(Session *s, bool force);

diff --git a/src/login/org.freedesktop.login1.conf b/src/login/org.freedesktop.login1.conf

index 95d2ef0f06..6113b64aa7 100644

--- a/src/login/org.freedesktop.login1.conf

+++ b/src/login/org.freedesktop.login1.conf

@@ -346,6 +346,10 @@

                        send_interface="org.freedesktop.login1.User"

                        send_member="Kill"/>

+                

+                       send_interface="org.freedesktop.login1.Session"

+                       send_member="SetDisplay"/>

+

                 <allow receive_sender="org.freedesktop.login1"/>

         </policy>