bus: add support for attaching name to bus connections for debugging purposes

[elogind.git] / src / libudev / libudev-monitor.c

diff --git a/src/libudev/libudev-monitor.c b/src/libudev/libudev-monitor.c
index e07e462af3bb861cfeb563543d66a0b441996269..ea7263f2808a6721b542a099a6dd83e907bd73ff 100644 (file)
--- a/src/libudev/libudev-monitor.c
+++ b/src/libudev/libudev-monitor.c
@@ -35,6 +35,7 @@
 #include "libudev.h"
 #include "libudev-private.h"
 #include "socket-util.h"
+#include "missing.h"
 
 /**
  * SECTION:libudev-monitor
@@ -105,6 +106,61 @@ static struct udev_monitor *udev_monitor_new(struct udev *udev)
         return udev_monitor;
 }
 
+/* we consider udev running when /dev is on devtmpfs */
+static bool udev_has_devtmpfs(struct udev *udev) {
+        struct file_handle *h;
+        int mount_id;
+        _cleanup_fclose_ FILE *f = NULL;
+        char line[LINE_MAX], *e;
+        int r;
+
+        h = alloca(MAX_HANDLE_SZ);
+        h->handle_bytes = MAX_HANDLE_SZ;
+        r = name_to_handle_at(AT_FDCWD, "/dev", h, &mount_id, 0);
+        if (r < 0)
+                return false;
+
+
+        f = fopen("/proc/self/mountinfo", "re");
+        if (!f)
+                return false;
+
+        FOREACH_LINE(line, f, return false) {
+                int mid;
+
+                if (sscanf(line, "%i", &mid) != 1)
+                        continue;
+
+                if (mid != mount_id)
+                        continue;
+
+                e = strstr(line, " - ");
+                if (!e)
+                        continue;
+
+                /* accept any name that starts with the currently expected type */
+                if (startswith(e + 3, "devtmpfs"))
+                        return true;
+        }
+
+        return false;
+}
+
+/* we consider udev running when we have running udev service */
+static bool udev_has_service(struct udev *udev) {
+        struct udev_queue *queue;
+        bool active;
+
+        queue = udev_queue_new(udev);
+        if (!queue)
+                return false;
+
+        active = udev_queue_get_udev_is_active(queue);
+        udev_queue_unref(queue);
+
+        return active;
+}
+
 struct udev_monitor *udev_monitor_new_from_netlink_fd(struct udev *udev, const char *name, int fd)
 {
         struct udev_monitor *udev_monitor;
@@ -115,21 +171,29 @@ struct udev_monitor *udev_monitor_new_from_netlink_fd(struct udev *udev, const c
 
         if (name == NULL)
                 group = UDEV_MONITOR_NONE;
-        else if (streq(name, "udev"))
-                group = UDEV_MONITOR_UDEV;
-        else if (streq(name, "kernel"))
+        else if (streq(name, "udev")) {
+                /*
+                 * We do not support subscribing to uevents if no instance of
+                 * udev is running. Uevents would otherwise broadcast the
+                 * processing data of the host into containers, which is not
+                 * desired.
+                 *
+                 * Containers will currently not get any udev uevents, until
+                 * a supporting infrastructure is available.
+                 *
+                 * We do not set a netlink multicast group here, so the socket
+                 * will not receive any messages.
+                 */
+                if (!udev_has_service(udev) && !udev_has_devtmpfs(udev)) {
+                        udev_dbg(udev, "the udev service seems not to be active, disable the monitor\n");
+                        group = UDEV_MONITOR_NONE;
+                } else
+                        group = UDEV_MONITOR_UDEV;
+        } else if (streq(name, "kernel"))
                 group = UDEV_MONITOR_KERNEL;
         else
                 return NULL;
 
-        /*
-         * We do not support subscribing to uevents if no instance of udev
-         * is running. Uevents would otherwise broadcast the processing data
-         * of the host into containers, which is not acceptable. Containers
-         * will currently just not get any uevents.
-         */
-        
-
         udev_monitor = udev_monitor_new(udev);
         if (udev_monitor == NULL)
                 return NULL;