net: if: Add NET_IF_UP flag

This adds NET_IF_UP flag support indicating the interface is up,
currently this shall only be used internally by the driver, later on it
shall be possible to make it public by using dedicated functions.

Change-Id: I38090da4030395b2341733b846004789416d61c1
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

include/net/net_if.h

diff --git a/include/net/net_if.h b/include/net/net_if.h
index 55b6386..c7f3739 100644
--- a/include/net/net_if.h
+++ b/include/net/net_if.h
@@ -150,6 +150,14 @@
  */
 #define __net_if_align __aligned(32)
 
+enum {
+	/* interface is up/ready to receive and transmit */
+	NET_IF_UP,
+
+	/* Total number of flags - must be at the end of the enum */
+	NET_IF_NUM_FLAGS
+};
+
 /**
  * @brief Network Interface structure
  *
@@ -167,6 +175,9 @@
 	/** The actually device driver instance the net_if is related to */
 	struct device *dev;
 
+	/* For internal use */
+	ATOMIC_DEFINE(flags, NET_IF_NUM_FLAGS);
+
 	/** Interface's L2 layer */
 	const struct net_l2 const *l2;
 
@@ -409,22 +420,20 @@
  * @param iface Pointer to a network interface structure
  * @param addr a pointer on a uint8_t buffer representing the address
  * @param len length of the address buffer
+ *
+ * @return 0 on success
  */
-static inline void net_if_set_link_addr(struct net_if *iface,
+static inline int net_if_set_link_addr(struct net_if *iface,
 					uint8_t *addr, uint8_t len)
 {
+	if (atomic_test_bit(iface->flags, NET_IF_UP)) {
+		return -EPERM;
+	}
+
 	iface->link_addr.addr = addr;
 	iface->link_addr.len = len;
 
-#if defined(CONFIG_NET_IPV6_DAD)
-	NET_DBG("Starting DAD for iface %p", iface);
-	net_if_start_dad(iface);
-#endif
-
-#if defined(CONFIG_NET_IPV6_ND)
-	NET_DBG("Starting ND/RS for iface %p", iface);
-	net_if_start_rs(iface);
-#endif
+	return 0;
 }
 
 /**
@@ -1088,6 +1097,24 @@
  */
 void net_if_foreach(net_if_cb_t cb, void *user_data);
 
+/**
+ * @brief Bring interface up
+ *
+ * @param iface Pointer to network interface
+ *
+ * @return 0 on success
+ */
+int net_if_up(struct net_if *iface);
+
+/*
+ * @brief Bring interface down
+ *
+ * @param iface Pointer to network interface
+ *
+ * @return 0 on success
+ */
+int net_if_down(struct net_if *iface);
+
 struct net_if_api {
 	void (*init)(struct net_if *iface);
 	int (*send)(struct net_if *iface, struct net_buf *buf);