Add API to get ipv6 link local address.

Protocols like mdns requires IPv6 link local address to be advertised in its
records (AAAA record). LWIP::Interface::bringup() API is creating IPv6 link
local address;But as of now there is no API exposed by mbed-os to get the
IPv6 link local address.

This new API is required to deliver mDNS library support on mbed-os for Cypress
platforms. Unit tested it by invoking get_ipv6_link_local_address with a simple
application.

Author: Jayasankar Nara

features/lwipstack/LWIPInterface.cpp

@@ -273,6 +273,52 @@ char *LWIP::Interface::get_interface_name(char *buf)
     return buf;
 }
 
+static bool convert_lwip_addr_to_mbed(nsapi_addr_t *out, const ip_addr_t *in)
+{
+#if LWIP_IPV6
+    if (IP_IS_V6(in)) {
+        out->version = NSAPI_IPv6;
+        SMEMCPY(out->bytes, ip_2_ip6(in), sizeof(ip6_addr_t));
+        return true;
+    }
+#endif
+#if LWIP_IPV4
+    if (IP_IS_V4(in)) {
+        out->version = NSAPI_IPv4;
+        SMEMCPY(out->bytes, ip_2_ip4(in), sizeof(ip4_addr_t));
+        return true;
+    }
+#endif
+#if LWIP_IPV6 && LWIP_IPV4
+    return false;
+#endif
+}
+
+nsapi_error_t LWIP::Interface::get_ipv6_link_local_address(SocketAddress *address)
+{
+#if LWIP_IPV6
+    const ip_addr_t *addr = LWIP::get_ipv6_link_local_addr(&netif);
+    nsapi_addr_t out;
+    bool ret;
+
+    if (!addr) {
+        return NSAPI_ERROR_PARAMETER;
+    }
+
+    ret = convert_lwip_addr_to_mbed(&out, addr);
+    if(ret != true)
+    {
+        return NSAPI_ERROR_PARAMETER;
+    }
+
+    address->set_addr(out);
+
+    return NSAPI_ERROR_OK;
+#else
+    return NSAPI_ERROR_PARAMETER;
+#endif
+}
+
 char *LWIP::Interface::get_ip_address(char *buf, nsapi_size_t buflen)
 {
     const ip_addr_t *addr = LWIP::get_ip_addr(true, &netif);

features/lwipstack/LWIPStack.h

@@ -100,6 +100,13 @@ class LWIP : public OnboardNetworkStack, private mbed::NonCopyable<LWIP> {
          */
         virtual char *get_ip_address(char *buf, nsapi_size_t buflen);
 
+        /** Get the IPv6 link local address in SocketAddress representation
+         *
+         *  @address        SocketAddress representation of the link local IPv6 address
+         *  @return         NSAPI_ERROR_OK on success, or error code
+         */
+        nsapi_error_t get_ipv6_link_local_address(SocketAddress *address);
+
         /** Copies IP address of the name based network interface to user supplied buffer
          *
          * @param    buf        buffer to which IP address will be copied as "W:X:Y:Z"
@@ -548,6 +555,7 @@ class LWIP : public OnboardNetworkStack, private mbed::NonCopyable<LWIP> {
     static const ip_addr_t *get_ip_addr(bool any_addr, const struct netif *netif);
     static const ip_addr_t *get_ipv4_addr(const struct netif *netif);
     static const ip_addr_t *get_ipv6_addr(const struct netif *netif);
+    static const ip_addr_t *get_ipv6_link_local_addr(const struct netif *netif);
 
     static void add_dns_addr(struct netif *lwip_netif, const char *interface_name);
 

features/lwipstack/lwip_tools.cpp

@@ -74,6 +74,23 @@ const ip_addr_t *LWIP::get_ipv4_addr(const struct netif *netif)
     return NULL;
 }
 
+const ip_addr_t *LWIP::get_ipv6_link_local_addr(const struct netif *netif)
+{
+#if LWIP_IPV6
+    if (!netif_is_up(netif)) {
+        return NULL;
+    }
+
+    for (int i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
+        if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
+                ip6_addr_islinklocal(netif_ip6_addr(netif, i))) {
+            return netif_ip_addr6(netif, i);
+        }
+    }
+#endif
+    return NULL;
+}
+
 const ip_addr_t *LWIP::get_ipv6_addr(const struct netif *netif)
 {
 #if LWIP_IPV6

features/netsocket/EMACInterface.cpp

@@ -95,6 +95,15 @@ const char *EMACInterface::get_ip_address()
     return NULL;
 }
 
+nsapi_error_t EMACInterface::get_ipv6_link_local_address(SocketAddress *address)
+{
+    if (_interface && _interface->get_ipv6_link_local_address(address)) {
+        return NSAPI_ERROR_PARAMETER;
+    }
+
+    return NSAPI_ERROR_OK;
+}
+
 const char *EMACInterface::get_netmask()
 {
     if (_interface && _interface->get_netmask(_netmask, sizeof(_netmask))) {

features/netsocket/EMACInterface.h

@@ -103,6 +103,13 @@ class EMACInterface : public virtual NetworkInterface {
      */
     virtual const char *get_ip_address();
 
+    /** Get the IPv6 link local address
+     *
+     *  @address        SocketAddress representation of the link local IPv6 address
+     *  @return         0 on success, negative error code on failure
+     */
+    virtual nsapi_error_t get_ipv6_link_local_address(SocketAddress *address);
+
     /** Get the local network mask
      *
      *  @return         Null-terminated representation of the local network mask

features/netsocket/NetworkInterface.cpp

@@ -37,6 +37,11 @@ const char *NetworkInterface::get_ip_address()
     return 0;
 }
 
+nsapi_error_t NetworkInterface::get_ipv6_link_local_address(SocketAddress *address)
+{
+    return NSAPI_ERROR_UNSUPPORTED;
+}
+
 const char *NetworkInterface::get_netmask()
 {
     return 0;

features/netsocket/NetworkInterface.h

@@ -106,6 +106,8 @@ class NetworkInterface: public DNS {
      */
     virtual const char *get_ip_address();
 
+    virtual nsapi_error_t get_ipv6_link_local_address(SocketAddress *address);
+
     /** Get the local network mask.
      *
      *  @return         Null-terminated representation of the local network mask

features/netsocket/OnboardNetworkStack.h

@@ -118,6 +118,19 @@ class OnboardNetworkStack : public NetworkStack {
 
         virtual char *get_ip_address(char *buf, nsapi_size_t buflen) = 0;
 
+        /** Copies IPv6 link local address of the network interface to user supplied buffer
+         *
+         * @param    buf        buffer to which IP address will be copied as "W:X:Y:Z"
+         * @param    buflen     size of supplied buffer
+         * @param    interface_name  Network interface name
+         * @return              Pointer to a buffer, or NULL if the buffer is too small
+         */
+
+        virtual nsapi_error_t get_ipv6_link_local_address(SocketAddress *address)
+        {
+            return NSAPI_ERROR_OK;
+        }
+
         /** Copies IP address of the network interface to user supplied buffer
          *
          * @param    buf        buffer to which IP address will be copied as "W:X:Y:Z"