coap_session.[hc]: Added function to retrieve PSK identity from session

The new function coap_session_get_psk_identity() returns the given
session's psk_identity as provided during the handhake (for CoAP server)
or a session setup (for CoAP client).

include/coap3/coap_session.h

@@ -287,6 +287,15 @@ coap_session_t *coap_new_client_session_psk2(
 const coap_bin_const_t * coap_session_get_psk_hint(
                                                const coap_session_t *session);
 
+/**
+ * Get the server session's current PSK identity (PSK).
+ *
+ * @param session  The current coap_session_t object.
+ *
+ * @return PSK identity if successful, else @c NULL.
+ */
+const coap_bin_const_t *coap_session_get_psk_identity(
+                                               const coap_session_t *session);
 /**
  * Get the session's current pre-shared key (PSK).
  *

libcoap-3.map

@@ -188,6 +188,7 @@ global:
   coap_session_get_max_retransmit;
   coap_session_get_proto;
   coap_session_get_psk_hint;
+  coap_session_get_psk_identity;
   coap_session_get_psk_key;
   coap_session_get_state;
   coap_session_get_tls;

libcoap-3.sym

@@ -186,6 +186,7 @@ coap_session_get_ifindex
 coap_session_get_max_retransmit
 coap_session_get_proto
 coap_session_get_psk_hint
+coap_session_get_psk_identity
 coap_session_get_psk_key
 coap_session_get_state
 coap_session_get_tls

src/coap_session.c

@@ -1131,6 +1131,18 @@ coap_session_get_psk_hint(const coap_session_t *session) {
 }
 #endif /* COAP_SERVER_SUPPORT */
 
+const coap_bin_const_t *
+coap_session_get_psk_identity(const coap_session_t *session) {
+  const coap_bin_const_t *psk_identity = NULL;
+  if (session) {
+    psk_identity = session->psk_identity;
+    if (psk_identity == NULL) {
+      psk_identity = &session->cpsk_setup_data.psk_info.identity;
+    }
+  }
+  return psk_identity;
+}
+
 const coap_bin_const_t *
 coap_session_get_psk_key(const coap_session_t *session) {
   if (session)