Register to multicast groups (ARMmbed#66)

* Register to multicast groups

COAP service registers automatically to COAP multicast groups:
-ff02::fd (link-local according to RFC 7390)
-ff05::fd (site local according to RFC 7390)

coap-service/coap_service_api.h

@@ -58,6 +58,10 @@ extern "C" {
 #define COAP_REQUEST_OPTIONS_MULTICAST          0x04 //!< indicates that CoAP library support multicasting
 #define COAP_REQUEST_OPTIONS_SECURE_BYPASS      0x08
 
+extern const uint8_t COAP_MULTICAST_ADDR_LINK_LOCAL[16]; //!< ff02::fd, COAP link local multicast address
+extern const uint8_t COAP_MULTICAST_ADDR_ADMIN_LOCAL[16]; //!< ff03::fd, COAP admin-local multicast address
+extern const uint8_t COAP_MULTICAST_ADDR_SITE_LOCAL[16]; //!> ff05::fd, COAP site-local multicast address
+
 /**
  * \brief Service message response receive callback.
  *

source/coap_connection_handler.c

@@ -42,6 +42,10 @@ typedef struct internal_socket_s {
     ns_list_link_t link;
 } internal_socket_t;
 
+const uint8_t COAP_MULTICAST_ADDR_LINK_LOCAL[16] = { 0xff, 0x02, [15] = 0xfd }; // ff02::fd, COAP link-local multicast (rfc7390)
+const uint8_t COAP_MULTICAST_ADDR_ADMIN_LOCAL[16] = { 0xff, 0x03, [15] = 0xfd }; // ff02::fd, COAP admin-local multicast (rfc7390)
+const uint8_t COAP_MULTICAST_ADDR_SITE_LOCAL[16] = { 0xff, 0x05, [15] = 0xfd }; // ff05::fd, COAP site-local multicast (rfc7390)
+
 static NS_LIST_DEFINE(socket_list, internal_socket_t, link);
 
 static void timer_cb(void* param);
@@ -223,7 +227,9 @@ static secure_session_t *secure_session_find(internal_socket_t *parent, const ui
 
 static internal_socket_t *int_socket_create(uint16_t listen_port, bool use_ephemeral_port, bool is_secure, bool real_socket, bool bypassSec, int8_t socket_interface_selection)
 {
+    ns_ipv6_mreq_t ns_ipv6_mreq;
     internal_socket_t *this = ns_dyn_mem_alloc(sizeof(internal_socket_t));
+
     if (!this) {
         return NULL;
     }
@@ -265,10 +271,22 @@ static internal_socket_t *int_socket_create(uint16_t listen_port, bool use_ephem
 
         // Set socket option to receive packet info
         socket_setsockopt(this->socket, SOCKET_IPPROTO_IPV6, SOCKET_IPV6_RECVPKTINFO, &(const bool) {1}, sizeof(bool));
-        if (socket_interface_selection != -1) {
-            // Select socket interface if selection requested
-            socket_setsockopt(this->socket, SOCKET_IPPROTO_IPV6, SOCKET_INTERFACE_SELECT, &socket_interface_selection, sizeof(int8_t));
+        if (socket_interface_selection > 0) {
+            // Interface selection requested as socket_interface_selection set
+            socket_setsockopt(this->socket, SOCKET_IPPROTO_IPV6, SOCKET_INTERFACE_SELECT, &socket_interface_selection, sizeof(socket_interface_selection));
         }
+
+        // Join COAP multicast group(s)
+        ns_ipv6_mreq.ipv6mr_interface = socket_interface_selection; // It is OK to use 0 or real interface id here
+
+        memcpy(ns_ipv6_mreq.ipv6mr_multiaddr, COAP_MULTICAST_ADDR_LINK_LOCAL, 16);
+        socket_setsockopt(this->socket, SOCKET_IPPROTO_IPV6, SOCKET_IPV6_JOIN_GROUP, &ns_ipv6_mreq, sizeof(ns_ipv6_mreq));
+
+        memcpy(ns_ipv6_mreq.ipv6mr_multiaddr, COAP_MULTICAST_ADDR_ADMIN_LOCAL, 16);
+        socket_setsockopt(this->socket, SOCKET_IPPROTO_IPV6, SOCKET_IPV6_JOIN_GROUP, &ns_ipv6_mreq, sizeof(ns_ipv6_mreq));
+
+        memcpy(ns_ipv6_mreq.ipv6mr_multiaddr, COAP_MULTICAST_ADDR_SITE_LOCAL, 16);
+        socket_setsockopt(this->socket, SOCKET_IPPROTO_IPV6, SOCKET_IPV6_JOIN_GROUP, &ns_ipv6_mreq, sizeof(ns_ipv6_mreq));
     } else {
         this->socket = virtual_socket_id_allocate();
     }

source/coap_service_api.c

@@ -280,7 +280,7 @@ static int get_passwd_cb(int8_t socket_id, uint8_t address[static 16], uint16_t
 int8_t coap_service_initialize(int8_t interface_id, uint16_t listen_port, uint8_t service_options,
                                  coap_service_security_start_cb *start_ptr, coap_service_security_done_cb *coap_security_done_cb)
 {
-    int8_t socket_interface_selection = -1;
+    int8_t socket_interface_selection = 0; // zero is illegal interface ID
     coap_service_t *this = ns_dyn_mem_alloc(sizeof(coap_service_t));
     if (!this) {
         return -1;