platform: add nm_platform_link_get_dev_id()

Some devices (s390 OSA and ipvlan) use the same link layer address
for different interfaces, and dev_id is what differentiates them.

src/platform/nm-fake-platform.c

@@ -488,6 +488,15 @@ link_get_physical_port_id (NMPlatform *platform, int ifindex)
 	return NULL;
 }
 
+static guint
+link_get_dev_id (NMPlatform *platform, int ifindex)
+{
+	/* We call link_get just to cause an error to be set if @ifindex is bad. */
+	link_get (platform, ifindex);
+
+	return 0;
+}
+
 static gboolean
 link_get_wake_on_lan (NMPlatform *platform, int ifindex)
 {
@@ -1406,6 +1415,7 @@ nm_fake_platform_class_init (NMFakePlatformClass *klass)
 	platform_class->link_set_mtu = link_set_mtu;
 
 	platform_class->link_get_physical_port_id = link_get_physical_port_id;
+	platform_class->link_get_dev_id = link_get_dev_id;
 	platform_class->link_get_wake_on_lan = link_get_wake_on_lan;
 
 	platform_class->link_supports_carrier_detect = link_supports_carrier_detect;

src/platform/nm-linux-platform.c

@@ -2744,6 +2744,30 @@ link_get_physical_port_id (NMPlatform *platform, int ifindex)
 	return id;
 }
 
+static guint
+link_get_dev_id (NMPlatform *platform, int ifindex)
+{
+	const char *ifname;
+	gs_free char *path = NULL, *id = NULL;
+	gint64 int_val;
+
+	ifname = nm_platform_link_get_name (ifindex);
+	if (!ifname)
+		return 0;
+
+	ifname = ASSERT_VALID_PATH_COMPONENT (ifname);
+
+	path = g_strdup_printf ("/sys/class/net/%s/dev_id", ifname);
+	id = sysctl_get (platform, path);
+	if (!id || !*id)
+		return 0;
+
+	/* Value is reported as hex */
+	int_val = _nm_utils_ascii_str_to_int64 (id, 16, 0, G_MAXUINT16, 0);
+
+	return errno ? 0 : (int) int_val;
+}
+
 static int
 vlan_add (NMPlatform *platform, const char *name, int parent, int vlan_id, guint32 vlan_flags)
 {
@@ -4608,6 +4632,7 @@ nm_linux_platform_class_init (NMLinuxPlatformClass *klass)
 	platform_class->link_set_mtu = link_set_mtu;
 
 	platform_class->link_get_physical_port_id = link_get_physical_port_id;
+	platform_class->link_get_dev_id = link_get_dev_id;
 	platform_class->link_get_wake_on_lan = link_get_wake_on_lan;
 
 	platform_class->link_supports_carrier_detect = link_supports_carrier_detect;

src/platform/nm-platform.c

@@ -1031,6 +1031,28 @@ nm_platform_link_get_physical_port_id (int ifindex)
 	return klass->link_get_physical_port_id (platform, ifindex);
 }
 
+/**
+ * nm_platform_link_get_dev_id:
+ * @ifindex: Interface index
+ *
+ * In contrast to the physical device ID (which indicates which parent a
+ * child has) the device ID differentiates sibling devices that may share
+ * the same MAC address.
+ *
+ * Returns: device ID for the interface, or 0 on error or if the
+ * interface has no device ID.
+ */
+guint
+nm_platform_link_get_dev_id (int ifindex)
+{
+	reset_error ();
+
+	g_return_val_if_fail (ifindex >= 0, 0);
+	g_return_val_if_fail (klass->link_get_dev_id, 0);
+
+	return klass->link_get_dev_id (platform, ifindex);
+}
+
 /**
  * nm_platform_link_get_wake_onlan:
  * @ifindex: Interface index

src/platform/nm-platform.h

@@ -374,6 +374,7 @@ typedef struct {
 	gboolean (*link_set_mtu) (NMPlatform *, int ifindex, guint32 mtu);
 
 	char *   (*link_get_physical_port_id) (NMPlatform *, int ifindex);
+	guint    (*link_get_dev_id) (NMPlatform *, int ifindex);
 	gboolean (*link_get_wake_on_lan) (NMPlatform *, int ifindex);
 
 	gboolean (*link_supports_carrier_detect) (NMPlatform *, int ifindex);
@@ -524,6 +525,7 @@ guint32 nm_platform_link_get_mtu (int ifindex);
 gboolean nm_platform_link_set_mtu (int ifindex, guint32 mtu);
 
 char    *nm_platform_link_get_physical_port_id (int ifindex);
+guint    nm_platform_link_get_dev_id (int ifindex);
 gboolean nm_platform_link_get_wake_on_lan (int ifindex);
 
 gboolean nm_platform_link_supports_carrier_detect (int ifindex);