vt protocols

Signed-off-by: Mattias Andrée <maandree@operamail.com>

5 files changed, 157 insertions, 12 deletions

diff --git a/Makefile b/Makefile
index b9cb6ed..67fe54e 100644
--- a/Makefile
+++ b/Makefile
@@ -15,6 +15,9 @@ LIBOBJ = linked-list client-list hash-table fd-table mds-message util
 SERVERS = mds mds-respawn mds-server mds-echo mds-registry mds-clipboard  \
           mds-kkbd mds-vt
 
+# Servers that need setuid and root owner.
+SETUID_SERVERS = mds mds-vt
+
 
 
 OBJ_mds-server_ = mds-server interception-condition client multicast  \
@@ -40,8 +43,8 @@ include mk/build.mk
 
 .PHONY: perms
 perms: all
-	sudo chown 'root:root' bin/mds
-	sudo chmod 4755 bin/mds
+	sudo chown 'root:root' $(foreach S,$(SETUID_SERVERS),bin/$(S))
+	sudo chmod 4755 $(foreach S,$(SETUID_SERVERS),bin/$(S))
 
 # Clean rules.
 
diff --git a/doc/protocols b/doc/protocols
index d40123b..54ace79 100644
--- a/doc/protocols
+++ b/doc/protocols
@@ -736,3 +736,103 @@ Compulsivity: optional
 
 ---------------------------------------------------------------------
 
+Command: get-vt
+  Get the index of the virtual terminal the server is display on
+  and the servers file descriptor for that tty
+
+Required header: Client ID
+  Your ID, provided by `ID assignment`
+  in response to `Command: assign-id`
+
+Response: The server will response with the header `VT index`
+	  and the index of the virtual terminal the server is
+	  display on in decimal format. Additionally the server
+	  will respond with the header `Active` with the value
+	  `yes` if the VT is in the foreground or the value
+	  `no` if the VT is in the background.
+
+Purpose: Allow programs to be aware of whether the display
+	 is in the foreground or the background
+Purpose: Allow programs to be aware of which VT the
+	 server is running on
+Purpose: Allow programs to gain access of the TTY associated
+	 with the VT such that they can use ioctl and similar
+	 calls on that TTY
+
+Compulsivity: required
+
+Reference implementation: vt
+
+---------------------------------------------------------------------
+
+Command: configure-vt
+  Reconfigure the virtual terminal the server is display on
+
+Required header: Client ID
+  Your ID, provided by `ID assignment`
+  in response to `Command: assign-id`
+
+Optional header: graphical
+  yes) Set the TTY graphical mode
+  no)  Set the TTY text mode
+  The server implementing this protocol should not set the
+  TTY to  text mode temporarily when switching TTY. It is
+  up the the server that set the request for graphical mode
+  to temporarily switch to text mode when switching TTY.
+
+Optional header: exclusive
+  yes) The server may block other process from opening the TTY.
+  no)  The server may not block other process from opening the TTY.
+
+Response: The server will response with a `Command: error`
+
+Purpose: Allow presentation servers to enter and leave graphical mode
+Purpose: Allow programs to gain access of the TTY associated
+	 with the VT such that they can use ioctl and similar
+	 calls on that TTY
+
+Compulsivity: required
+
+Reference implementation: vt
+
+---------------------------------------------------------------------
+
+Command: switching-vt
+  Notify servers about an ongoing virtual terminal switch
+
+Required header: Status
+  deactivating)  The kernel wants to place the display in the background
+  activating)    The kernel wants to place the display in the foreground
+
+Instructions: When a virtual terminal switch is requested the
+	      server implementing control VT switching involving
+	      the display's virtual terminal will get signaled by
+	      the kernel. Upon this signal the server should
+	      roadcast this command. All servers that need to
+	      release or acquire resouces should intercept this
+	      message with the possibility of modifying it.
+	      Once a server is ready for the VT to switch it should
+	      let the message pass to the next server by telling
+	      the master server that it is no modification to do.
+	      Once all servers are read for the switch the server
+	      that emitted this message should signal the kernel
+	      that it may switch VT. The server should detect
+	      this by setting up secondary contection to the
+	      display that intercepts this message. This connection
+	      should intercept this message with priority −2³²,
+	      all servers that need to perform actions before the
+	      switch takes place must have a priority higher than
+	      −2³², preferably 0.
+
+Purpose: Allow servers to release resources when the user switch
+	 virtual terminal before the terminal actually changes and
+	 to reacquire resources when the virtual terminal become
+	 active again
+
+Compulsivity: required
+
+Reference implementation: vt
+Reference implementation: kkbd
+
+---------------------------------------------------------------------
+
diff --git a/src/mds-kkbd.c b/src/mds-kkbd.c
index b699ea0..842da90 100644
--- a/src/mds-kkbd.c
+++ b/src/mds-kkbd.c
@@ -16,6 +16,9 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 #include "mds-kkbd.h"
+/* TODO: This server should wait for `Command: get-vt` to be available,
+         query the active VT and connect to that TTY instead of stdin. */
+/* TODO: Release control on `Command: switching-vt`. */
 
 #include <libmdsserver/macros.h>
 #include <libmdsserver/util.h>
diff --git a/src/mds-vt.c b/src/mds-vt.c
index 2167fb1..a6124c9 100644
--- a/src/mds-vt.c
+++ b/src/mds-vt.c
@@ -50,7 +50,7 @@ server_characteristics_t server_characteristics =
   {
     .require_privileges = 1, /* we want to open the new tty (the rest is fine without root for some reason) */
     .require_display = 1,
-    .require_respawn_info = 0,
+    .require_respawn_info = 1,
     .sanity_check_argc = 1,
     .fork_for_safety = 0,
     .danger_is_deadly = 0
@@ -98,9 +98,10 @@ int initialise_server(void)
   const char* const message =
     "Command: intercept\n"
     "Message ID: 0\n"
-    "Length: 14\n"
+    "Length: 38\n"
     "\n"
-    "Command: echo\n";
+    "Command: get-vt\n";
+    "Command: configure-vt\n";
   
   if (full_send(message, strlen(message)))
     return 1;
@@ -337,16 +338,44 @@ int vt_set_active(int vt)
 /**
  * Open a virtual terminal
  * 
- * @param   vt  The index of the terminal
- * @return      The file descriptor for the terminal, -1 on error
+ * @param   vt        The index of the terminal
+ * @param   old_stat  Output parameter for the old file stat for the terminal
+ * @return            The file descriptor for the terminal, -1 on error
  */
-int vt_open(int vt)
+int vt_open(int vt, struct stat* restrict old_stat)
 {
   char vtpath[64]; /* Should be small enought and large enought for any
 		      lunatic alternative to /dev/ttyNNN, if not you
 		      will need to apply a patch (or fix your system.) */
+  int fd;
   sprintf(vtpath, VT_PATH_PATTERN, vt);
-  return open(vtpath, O_RDWR);
+  fd = open(vtpath, O_RDWR);
+  if (fd < 0)
+    return -1;
+  if ((fstat(fd, old_stat) < 0) ||
+      (fchown(fd, getuid(), getgid()) < 0))
+    {
+      close(fd);
+      return -1;
+    }
+  return fd;
+}
+
+
+/**
+ * Close a virtual terminal
+ * 
+ * @param  vt        The index of the terminal
+ * @param  old_stat  The old file stat for the terminal
+ */
+void vt_close(int fd, struct stat* restrict old_stat)
+{
+  if (fchown(fd, old_stat->st_uid, old_stat->st_gid) < 0)
+    {
+      xperror(*argv);
+      eprint("while resetting TTY ownership.");
+    }
+  close(fd);
 }
 
 
diff --git a/src/mds-vt.h b/src/mds-vt.h
index 1f87726..60204fc 100644
--- a/src/mds-vt.h
+++ b/src/mds-vt.h
@@ -62,10 +62,20 @@ int vt_set_active(int vt);
 /**
  * Open a virtual terminal
  * 
- * @param   vt  The index of the terminal
- * @return      The file descriptor for the terminal, -1 on error
+ * @param   vt        The index of the terminal
+ * @param   old_stat  Output parameter for the old file stat for the terminal
+ * @return            The file descriptor for the terminal, -1 on error
+ */
+int vt_open(int vt, struct stat* restrict old_stat);
+
+
+/**
+ * Close a virtual terminal
+ * 
+ * @param  vt        The index of the terminal
+ * @param  old_stat  The old file stat for the terminal
  */
-int vt_open(int vt);
+void vt_close(int fd, struct stat* restrict old_stat);