[api] add API to test whether the IPv6 address is a link local unicast address (#11902)

include/openthread/instance.h

@@ -52,7 +52,7 @@ extern "C" {
  *
  * @note This number versions both OpenThread platform and user APIs.
  */
-#define OPENTHREAD_API_VERSION (535)
+#define OPENTHREAD_API_VERSION (536)
 
 /**
  * @addtogroup api-instance

include/openthread/ip6.h

@@ -556,6 +556,16 @@ const uint16_t *otIp6GetUnsecurePorts(otInstance *aInstance, uint8_t *aNumEntrie
  */
 bool otIp6IsAddressEqual(const otIp6Address *aFirst, const otIp6Address *aSecond);
 
+/**
+ * Test whether or not the IPv6 address is a link-local unicast address.
+ *
+ * @param[in]  aAddress   A pointer to the IPv6 address to test.
+ *
+ * @retval TRUE   If the IPv6 address is a link-local unicast address.
+ * @retval FALSE  If the IPv6 address is not a link-local unicast address.
+ */
+bool otIp6IsLinkLocalUnicast(const otIp6Address *aAddress);
+
 /**
  * Test if two IPv6 prefixes are the same.
  *

src/core/api/ip6_api.cpp

@@ -171,6 +171,8 @@ bool otIp6IsAddressEqual(const otIp6Address *aFirst, const otIp6Address *aSecond
     return AsCoreType(aFirst) == AsCoreType(aSecond);
 }
 
+bool otIp6IsLinkLocalUnicast(const otIp6Address *aAddress) { return AsCoreType(aAddress).IsLinkLocalUnicast(); }
+
 bool otIp6ArePrefixesEqual(const otIp6Prefix *aFirst, const otIp6Prefix *aSecond)
 {
     return AsCoreType(aFirst) == AsCoreType(aSecond);