device: allow easy identification of network interfaces without their full sysfs device path

2 files changed, 33 insertions, 3 deletions

diff --git a/99-systemd.rules b/99-systemd.rules
index 9a9b27a022..c5c330f936 100644
--- a/99-systemd.rules
+++ b/99-systemd.rules
@@ -19,7 +19,20 @@ ACTION!="add|change", GOTO="systemd_end"
 
 KERNEL=="tty[0-9]|tty1[0-2]", ENV{SYSTEMD_EXPOSE}="1"
 KERNEL=="ttyS*", ENV{SYSTEMD_EXPOSE}="1"
+
 SUBSYSTEM=="block", ENV{SYSTEMD_EXPOSE}="1"
-SUBSYSTEM=="net", ENV{SYSTEMD_EXPOSE}="1"
+
+# We need a hardware independant way to identify network devices. We
+# use the /sys/subsystem path for this. Current vanilla kernels don't
+# actually support that hierarchy right now, however upcoming kernels
+# will. HAL and udev internally support /sys/subsystem already, hence
+# it should be safe to use this here, too. This is mostly just an
+# identification string for systemd, so whether the path actually is
+# accessible or not does not matter as long as it is unique and in the
+# filesystem namespace.
+#
+# http://git.kernel.org/?p=linux/hotplug/udev.git;a=blob;f=libudev/libudev-enumerate.c;h=da831449dcaf5e936a14409e8e68ab12d30a98e2;hb=HEAD#l742
+
+SUBSYSTEM=="net", KERNEL!="lo", ENV{SYSTEMD_EXPOSE}="1", ENV{SYSTEMD_ALIAS}="/sys/subsystem/net/devices/%k"
 
 LABEL="systemd_end"
diff --git a/device.c b/device.c
index 95c458f3d7..70936808be 100644
--- a/device.c
+++ b/device.c
@@ -144,7 +144,7 @@ static int device_find_escape_name(Manager *m, const char *dn, Unit **_u) {
 }
 
 static int device_process_new_device(Manager *m, struct udev_device *dev, bool update_state) {
-        const char *dn, *wants, *sysfs, *expose, *model;
+        const char *dn, *wants, *sysfs, *expose, *model, *alias;
         Unit *u = NULL;
         int r;
         char *w, *state;
@@ -172,6 +172,15 @@ static int device_process_new_device(Manager *m, struct udev_device *dev, bool u
         /* Check whether this entry is even relevant for us. */
         dn = udev_device_get_devnode(dev);
         wants = udev_device_get_property_value(dev, "SYSTEMD_WANTS");
+        alias = udev_device_get_property_value(dev, "SYSTEMD_ALIAS");
+
+        /* We allow exactly one alias to be configured a this time and
+         * it must be a path */
+
+        if (alias && !is_path(alias)) {
+                log_warning("SYSTEMD_ALIAS for %s is not a path, ignoring: %s", sysfs, alias);
+                alias = NULL;
+        }
 
         if ((r = device_find_escape_name(m, sysfs, &u)) < 0)
                 return r;
@@ -191,12 +200,16 @@ static int device_process_new_device(Manager *m, struct udev_device *dev, bool u
                 }
         }
 
+        if (r == 0 && alias)
+                if ((r = device_find_escape_name(m, alias, &u)) < 0)
+                        return r;
+
         /* FIXME: this needs proper merging */
 
         assert((r > 0) == !!u);
 
         /* If this is a different unit, then let's not merge things */
-        if (u && DEVICE(u)->sysfs && !streq(DEVICE(u)->sysfs, sysfs))
+        if (u && DEVICE(u)->sysfs && !path_equal(DEVICE(u)->sysfs, sysfs))
                 u = NULL;
 
         if (!u) {
@@ -218,6 +231,10 @@ static int device_process_new_device(Manager *m, struct udev_device *dev, bool u
                         goto fail;
                 }
 
+        if (alias)
+                if ((r = device_add_escaped_name(u, alias, true)) < 0)
+                        goto fail;
+
         if (dn)
                 if ((r = device_add_escaped_name(u, dn, true)) < 0)
                         goto fail;