Revert "remote: remove probing logic from virtproxyd dispatcher"

This reverts commit 05bd8db60b.

It is true that the remote driver client now contains logic for probing
the driver to connect to when using modular daemons. This logic, however,
only runs when the remote driver is NOT running inside a daemon since we
don't want it activated inside libvirtd. Since the same remote driver
build is used in all daemons, we can't rely on it in virtproxyd either.
Thus we need to keep the virtproxyd probing logic

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

src/remote/remote_daemon_dispatch.c

@@ -1948,6 +1948,73 @@ void *remoteClientNew(virNetServerClient *client,
 
 /*----- Functions. -----*/
 
+#ifdef VIRTPROXYD
+/*
+ * When running in virtproxyd regular auto-probing of drivers
+ * does not work as we don't have any drivers present (except
+ * stateless ones inside libvirt.so). All the interesting
+ * drivers are in separate daemons. Thus when we get a NULL
+ * URI we need to simulate probing that virConnectOpen would
+ * previously do. We use the existence of the UNIX domain
+ * socket as our hook for probing.
+ *
+ * This assumes no stale sockets left over from a now dead
+ * daemon, but that's reasonable since libvirtd unlinks
+ * sockets it creates on shutdown, or uses systemd activation
+ *
+ * We only try to probe for primary hypervisor drivers,
+ * not the secondary drivers.
+ */
+static int
+remoteDispatchProbeURI(bool readonly,
+                       char **probeduri)
+{
+    g_autofree char *driver = NULL;
+    const char *suffix;
+    *probeduri = NULL;
+    VIR_DEBUG("Probing for driver daemon sockets");
+
+    /*
+     * If running root, either the daemon is running and the socket
+     * exists, or we're using socket activation so the socket exists
+     * too.
+     *
+     * If running non-root, the daemon may or may not already be
+     * running, and socket activation probably isn't relevant.
+     * So if no viable socket exists, we need to check which daemons
+     * are actually installed. This is not a big deal as only QEMU &
+     * VBox run as non-root, anyway.
+     */
+    if (geteuid() != 0) {
+        if (remoteProbeSessionDriverFromSocket(false, &driver) < 0)
+            return -1;
+
+        if (driver == NULL &&
+            remoteProbeSessionDriverFromBinary(&driver) < 0)
+            return -1;
+
+        suffix = "session";
+    } else {
+        if (remoteProbeSystemDriverFromSocket(readonly, &driver) < 0)
+            return -1;
+
+        suffix = "system";
+    }
+
+    /* Even if we didn't probe any socket, we won't
+     * return error. Just let virConnectOpen's normal
+     * logic run which will likely return an error anyway
+     */
+    if (!driver)
+        return 0;
+
+    *probeduri = g_strdup_printf("%s:///%s", driver, suffix);
+    VIR_DEBUG("Probed URI %s for driver %s", *probeduri, driver);
+    return 0;
+}
+#endif /* VIRTPROXYD */
+
+
 static int
 remoteDispatchConnectOpen(virNetServer *server G_GNUC_UNUSED,
                           virNetServerClient *client,
@@ -1956,6 +2023,9 @@ remoteDispatchConnectOpen(virNetServer *server G_GNUC_UNUSED,
                           struct remote_connect_open_args *args)
 {
     const char *name;
+#ifdef VIRTPROXYD
+    g_autofree char *probeduri = NULL;
+#endif
     unsigned int flags;
     struct daemonClientPrivate *priv = virNetServerClientGetPrivateData(client);
     int rv = -1;
@@ -1984,6 +2054,13 @@ remoteDispatchConnectOpen(virNetServer *server G_GNUC_UNUSED,
     priv->readonly = flags & VIR_CONNECT_RO;
 
 #ifdef VIRTPROXYD
+    if (!name || STREQ(name, "")) {
+        if (remoteDispatchProbeURI(priv->readonly, &probeduri) < 0)
+            goto cleanup;
+
+        name = probeduri;
+    }
+
     preserveIdentity = true;
 #endif /* VIRTPROXYD */