device: tune down warning about failure to set userspace IPv6LL on non-existing device

When a device gets removed externally, we still try to clear userspace IPv6LL address handling.
That fails, due to non-existing device. Such a failure should not be logged as warning.

    <debug> [1467723214.2078] device[0x558c59335ca0] (enp0s25): disposing
    <debug> [1467723214.2079] device[0x558c59335ca0] (enp0s25): remove_pending_action (0): 'dhcp6' not pending (expected)
    <debug> [1467723214.2079] device[0x558c59335ca0] (enp0s25): remove_pending_action (0): 'autoconf6' not pending (expected)
    <debug> [1467723214.2079] device[0x558c59335ca0] (enp0s25): will disable userland IPv6LL
    <debug> [1467723214.2079] platform-linux: link: change 20: user-ipv6ll: set IPv6 address generation mode to eui64
    <trace> [1467723214.2080] platform-linux: delayed-action: schedule wait-for-nl-response (seq 92, timeout in 0.199998611)
    <trace> [1467723214.2080] platform-linux: delayed-action: schedule refresh-link (ifindex 20)
    <trace> [1467723214.2080] platform-linux: delayed-action: handle refresh-link (ifindex 20)
    <debug> [1467723214.2080] platform-linux: do-request-link: 20
    <trace> [1467723214.2080] platform-linux: netlink: recvmsg: new message type 2, seq 92
    <debug> [1467723214.2080] platform-linux: netlink: recvmsg: error message from kernel: No such device (19) for request 92
    <trace> [1467723214.2081] platform-linux: delayed-action: complete wait-for-nl-response (seq 92, timeout in 0.199895684, failure 19 (No such device))
    <trace> [1467723214.2081] platform-linux: delayed-action: schedule wait-for-nl-response (seq 93, timeout in 0.199999306)
    <trace> [1467723214.2081] platform-linux: delayed-action: handle wait-for-nl-response (any)
    <trace> [1467723214.2081] platform-linux: netlink: recvmsg: new message type 2, seq 93
    <debug> [1467723214.2081] platform-linux: netlink: recvmsg: error message from kernel: No such device (19) for request 93
    <trace> [1467723214.2082] platform-linux: delayed-action: complete wait-for-nl-response (seq 93, timeout in 0.199921142, failure 19 (No such device))
    <debug> [1467723214.2082] platform-linux: do-change-link[20]: failure changing link: failure 19 (No such device)
    <warn>  [1467723214.2082] device (enp0s25): failed to disable userspace IPv6LL address handling

https://bugzilla.redhat.com/show_bug.cgi?id=1323571

src/devices/nm-device.c

@@ -6440,11 +6440,18 @@ set_nm_ipv6ll (NMDevice *self, gboolean enable)
 
 	priv->nm_ipv6ll = enable;
 	if (ifindex > 0) {
+		NMPlatformError plerr;
 		const char *detail = enable ? "enable" : "disable";
 
 		_LOGD (LOGD_IP6, "will %s userland IPv6LL", detail);
-		if (!nm_platform_link_set_user_ipv6ll_enabled (NM_PLATFORM_GET, ifindex, enable))
-			_LOGW (LOGD_IP6, "failed to %s userspace IPv6LL address handling", detail);
+		plerr = nm_platform_link_set_user_ipv6ll_enabled (NM_PLATFORM_GET, ifindex, enable);
+		if (plerr != NM_PLATFORM_ERROR_SUCCESS) {
+			_NMLOG (plerr == NM_PLATFORM_ERROR_NOT_FOUND ? LOGL_DEBUG : LOGL_WARN,
+			        LOGD_IP6,
+			        "failed to %s userspace IPv6LL address handling (%s)",
+			        detail,
+			        nm_platform_error_to_string (plerr));
+		}
 
 		if (enable) {
 			/* Bounce IPv6 to ensure the kernel stops IPv6LL address generation */

src/platform/nm-linux-platform.c

@@ -4328,7 +4328,7 @@ link_get_udev_device (NMPlatform *platform, int ifindex)
 	return obj_cache ? (GObject *) obj_cache->_link.udev.device : NULL;
 }
 
-static gboolean
+static NMPlatformError
 link_set_user_ipv6ll_enabled (NMPlatform *platform, int ifindex, gboolean enabled)
 {
 	nm_auto_nlmsg struct nl_msg *nlmsg = NULL;
@@ -4336,7 +4336,7 @@ link_set_user_ipv6ll_enabled (NMPlatform *platform, int ifindex, gboolean enable
 
 	if (!_support_user_ipv6ll_get ()) {
 		_LOGD ("link: change %d: user-ipv6ll: not supported", ifindex);
-		return FALSE;
+		return NM_PLATFORM_ERROR_OPNOTSUPP;
 	}
 
 	_LOGD ("link: change %d: user-ipv6ll: set IPv6 address generation mode to %s",
@@ -4351,9 +4351,9 @@ link_set_user_ipv6ll_enabled (NMPlatform *platform, int ifindex, gboolean enable
 	                          0);
 	if (   !nlmsg
 	    || !_nl_msg_new_link_set_afspec (nlmsg, mode, NULL))
-		g_return_val_if_reached (FALSE);
+		g_return_val_if_reached (NM_PLATFORM_ERROR_BUG);
 
-	return do_change_link (platform, ifindex, nlmsg) == NM_PLATFORM_ERROR_SUCCESS;
+	return do_change_link (platform, ifindex, nlmsg);
 }
 
 static gboolean

src/platform/nm-platform.c

@@ -205,6 +205,7 @@ NM_UTILS_LOOKUP_STR_DEFINE (_nm_platform_error_to_string, NMPlatformError,
 	NM_UTILS_LOOKUP_STR_ITEM (NM_PLATFORM_ERROR_WRONG_TYPE,  "wrong-type"),
 	NM_UTILS_LOOKUP_STR_ITEM (NM_PLATFORM_ERROR_NOT_SLAVE,   "not-slave"),
 	NM_UTILS_LOOKUP_STR_ITEM (NM_PLATFORM_ERROR_NO_FIRMWARE, "no-firmware"),
+	NM_UTILS_LOOKUP_STR_ITEM (NM_PLATFORM_ERROR_OPNOTSUPP,   "not-supported"),
 	NM_UTILS_LOOKUP_ITEM_IGNORE (_NM_PLATFORM_ERROR_MININT),
 );
 
@@ -981,18 +982,16 @@ nm_platform_link_get_user_ipv6ll_enabled (NMPlatform *self, int ifindex)
  * platform or OS doesn't support changing the IPv6LL address mode, this call
  * will fail and return %FALSE.
  *
- * Returns: %TRUE if the operation was successful, %FALSE if it failed.
+ * Returns: %NM_PLATFORM_ERROR_SUCCESS if the operation was successful or an error code otherwise.
  */
-gboolean
+NMPlatformError
 nm_platform_link_set_user_ipv6ll_enabled (NMPlatform *self, int ifindex, gboolean enabled)
 {
-	_CHECK_SELF (self, klass, FALSE);
+	_CHECK_SELF (self, klass, NM_PLATFORM_ERROR_BUG);
 
-	g_return_val_if_fail (ifindex >= 0, FALSE);
+	g_return_val_if_fail (ifindex > 0, NM_PLATFORM_ERROR_BUG);
 
-	if (klass->link_set_user_ipv6ll_enabled)
-		return klass->link_set_user_ipv6ll_enabled (self, ifindex, enabled);
-	return FALSE;
+	return klass->link_set_user_ipv6ll_enabled (self, ifindex, enabled);
 }
 
 /**

src/platform/nm-platform.h

@@ -88,6 +88,7 @@ typedef enum { /*< skip >*/
 	NM_PLATFORM_ERROR_WRONG_TYPE,
 	NM_PLATFORM_ERROR_NOT_SLAVE,
 	NM_PLATFORM_ERROR_NO_FIRMWARE,
+	NM_PLATFORM_ERROR_OPNOTSUPP,
 } NMPlatformError;
 
 
@@ -519,7 +520,7 @@ typedef struct {
 	const char *(*link_get_udi) (NMPlatform *self, int ifindex);
 	GObject *(*link_get_udev_device) (NMPlatform *self, int ifindex);
 
-	gboolean (*link_set_user_ipv6ll_enabled) (NMPlatform *, int ifindex, gboolean enabled);
+	NMPlatformError (*link_set_user_ipv6ll_enabled) (NMPlatform *, int ifindex, gboolean enabled);
 	gboolean (*link_set_token) (NMPlatform *, int ifindex, NMUtilsIPv6IfaceId iid);
 
 	gboolean (*link_get_permanent_address) (NMPlatform *,
@@ -753,7 +754,7 @@ const char *nm_platform_link_get_udi (NMPlatform *self, int ifindex);
 
 GObject *nm_platform_link_get_udev_device (NMPlatform *self, int ifindex);
 
-gboolean nm_platform_link_set_user_ipv6ll_enabled (NMPlatform *self, int ifindex, gboolean enabled);
+NMPlatformError nm_platform_link_set_user_ipv6ll_enabled (NMPlatform *self, int ifindex, gboolean enabled);
 gboolean nm_platform_link_set_ipv6_token (NMPlatform *self, int ifindex, NMUtilsIPv6IfaceId iid);
 
 gboolean nm_platform_link_get_permanent_address (NMPlatform *self, int ifindex, guint8 *buf, size_t *length);