audio: fix reacting on mic enable/disable requests

First of all, after getting an event of QubesDB FD, actually call
qdb_read_watch() so the event is cleared and the next one can be
received.

But that's not enough. libqubesdb's queueing of watches doesn't handle
well using the same connection for both watches and commands, and using
non-blocking mode (monitoring qdb_watch_fd(), instead of calling
qdb_read_watch() in a loop). While this issue wants fixing on the
libqubesdb side, for now use separate connection to workaround the
issue.

Fixes QubesOS/qubes-issues#9619

pulse/pacat-simple-vchan.c

@@ -847,10 +847,19 @@ static void control_socket_callback(pa_mainloop_api *UNUSED(a),
 
     struct userdata *u = userdata;
     int new_rec_allowed = -1;
+    char *watch_path;
 
     if (!(f & PA_IO_EVENT_INPUT))
         return;
 
+    watch_path = qdb_read_watch(u->watch_qdb);
+    if (!watch_path) {
+        pacat_log("Failed to read the qdb watch");
+        return;
+    }
+    /* don't bother checking which watch fired, there is just one */
+    free(watch_path);
+
     new_rec_allowed = is_rec_allowed_from_qdb(u);
     if (new_rec_allowed >= 0) {
         g_mutex_lock(&u->prop_mutex);
@@ -903,13 +912,20 @@ static int setup_control(struct userdata *u) {
         u->qdb_config_path = NULL;
         goto fail;
     }
+
     // Setup a QubesDB watch to get authorization on demand
-    if (!qdb_watch(u->qdb, u->qdb_config_path)) {
+    u->watch_qdb = qdb_open(NULL);
+    if (!u->watch_qdb) {
+        pacat_log("qdb_open (watch) failed: %s", strerror(errno));
+        goto fail;
+    }
+
+    if (!qdb_watch(u->watch_qdb, u->qdb_config_path)) {
         pacat_log("failed to setup watch on %s: %m\n", u->qdb_config_path);
         goto fail;
     }
 
-    socket_fd = qdb_watch_fd(u->qdb);
+    socket_fd = qdb_watch_fd(u->watch_qdb);
     if (socket_fd < 0)
         goto fail;
 
@@ -946,8 +962,9 @@ static int setup_control(struct userdata *u) {
     if (u->control_socket_event)
         u->mainloop_api->io_free(u->control_socket_event);
     u->control_socket_event = NULL;
-    if (socket_fd >= 0)
-        close(socket_fd);
+    if (u->watch_qdb)
+        qdb_close(u->watch_qdb);
+    u->watch_qdb = NULL;
 
     return 1;
 }
@@ -964,6 +981,8 @@ static void control_cleanup(struct userdata *u) {
         free(u->qdb_status_path);
     if (u->qdb_request_path)
         free(u->qdb_request_path);
+    if (u->watch_qdb)
+        qdb_close(u->watch_qdb);
     if (u->qdb)
         qdb_close(u->qdb);
 }

pulse/pacat-simple-vchan.h

@@ -32,6 +32,7 @@ struct userdata {
 
     GMutex prop_mutex;
     qdb_handle_t qdb;
+    qdb_handle_t watch_qdb; // separate connection for watches
     char *qdb_config_path;
     char *qdb_status_path;
     char *qdb_request_path;