Added user-defined callback for finding oscore context

include/coap3/coap_net_internal.h

@@ -28,6 +28,24 @@
  * @{
  */
 
+/**
+ * Optional user callback to be used, when oscore_find_context can't find any context.
+ * Could be used to check external storage (e.g. FLASH).
+ *
+ * @param c_context The CoAP COntext to search.
+ * @param rcpkey_id The Recipient kid.
+ * @param ctxkey_id The ID Context to match (or NULL if no check).
+ * @param oscore_r2 Partial id_context to match against or NULL.
+ * @param recipient_ctx The recipient context to update.
+ *
+ * return The OSCORE context and @p recipient_ctx updated, or NULL is error.
+ */
+typedef oscore_ctx_t * (*external_oscore_find_context_handler_t)(const coap_context_t *c_context,
+                                                                 const coap_bin_const_t rcpkey_id,
+                                                                 const coap_bin_const_t *ctxkey_id,
+                                                                 uint8_t *oscore_r2,
+                                                                 oscore_recipient_ctx_t **recipient_ctx);
+
 /**
  * Queue entry
  */
@@ -93,6 +111,8 @@ struct coap_context_t {
 #endif /* WITH_LWIP */
 #if COAP_OSCORE_SUPPORT
   struct oscore_ctx_t *p_osc_ctx; /**< primary oscore context  */
+  external_oscore_find_context_handler_t external_oscore_find_context_handler;
+    /**< Called  when oscore_find_context didn't find any context*/
 #endif /* COAP_OSCORE_SUPPORT */
 
 #if COAP_CLIENT_SUPPORT
@@ -430,6 +450,17 @@ coap_mid_t coap_send_internal(coap_session_t *session, coap_pdu_t *pdu);
  */
 int coap_client_delay_first(coap_session_t *session);
 
+#if COAP_OSCORE_SUPPORT
+/**
+ * Register optional user callback to be used, when oscore_find_context can't find any context.
+ * Callback could be used to check external storage (e.g. FLASH).
+ * 
+ * @param ctx       The current coap context to use.
+ * @param handler   User callback.
+ */
+void coap_register_find_context_handler(coap_context_t *ctx, external_oscore_find_context_handler_t handler);
+#endif
+
 /** @} */
 
 extern int coap_started;

src/coap_net.c

@@ -576,6 +576,15 @@ coap_new_context(const coap_address_t *listen_addr) {
 #endif /* COAP_EPOLL_SUPPORT || COAP_SERVER_SUPPORT */
 }
 
+#if COAP_OSCORE_SUPPORT
+void
+coap_register_find_context_handler(coap_context_t *ctx, external_oscore_find_context_handler_t handler)
+{
+  assert(ctx);
+  ctx->external_oscore_find_context_handler = handler;
+}
+#endif
+
 void
 coap_set_app_data(coap_context_t *ctx, void *app_data) {
   assert(ctx);

src/oscore/oscore_context.c

@@ -227,6 +227,13 @@ oscore_find_context(const coap_context_t *c_context,
     } /* while rpt */
     pt = pt->next;
   } /* end while */
+
+  /* no context was found in libcoap RAM - call user function to also check external storage (e.g. FLASH) */
+  if (c_context->external_oscore_find_context_handler)
+  {
+    return c_context->external_oscore_find_context_handler(c_context, rcpkey_id, ctxkey_id, oscore_r2, recipient_ctx);
+  }
+
   return NULL;
 }