fixup! gcoap: add nanocoap_cache support for clients

sys/net/application_layer/gcoap/gcoap.c

@@ -1155,14 +1155,24 @@ static ssize_t _cache_build_response(nanocoap_cache_entry_t *ce, coap_pkt_t *pdu
         return -ENOTSUP;
     }
     if (len < ce->response_len) {
-        puts("Too short");
         return -ENOBUFS;
     }
+    /* Use the same code from the cached content. Use other header
+     * fields from the incoming request */
+    gcoap_resp_init(pdu, buf, len, ce->response_pkt.hdr->code);
     /* copy all options and possible payload from the cached response
      * to the new response */
-    memcpy(buf, ce->response_buf, ce->response_len);
-    /* parse into pdu */
-    coap_parse(pdu, buf, ce->response_len);
+    unsigned header_len_req = coap_get_total_hdr_len(pdu);
+    unsigned header_len_cached = coap_get_total_hdr_len(&ce->response_pkt);
+    unsigned opt_payload_len = ce->response_len - header_len_cached;
+
+    /* copy all options and possible payload from the cached response
+     * to the new response */
+    memcpy((buf + header_len_req),
+           (ce->response_buf + header_len_cached),
+           opt_payload_len);
+    /* parse into pdu including all options and payload pointers etc */
+    coap_parse(pdu, buf, header_len_req + opt_payload_len);
     return ce->response_len;
 }
 
@@ -1179,6 +1189,12 @@ static void _receive_from_cache_cb(void *ctx)
         if (memo->resp_handler) {
             coap_pkt_t pdu;
 
+            if (memo->send_limit == GCOAP_SEND_LIMIT_NON) {
+                pdu.hdr = (coap_hdr_t *)(&memo->msg.hdr_buf[0]);
+            }
+            else {
+                pdu.hdr = (coap_hdr_t *)memo->msg.data.pdu_buf;
+            }
             if (_cache_build_response(ce, &pdu, _listen_buf, sizeof(_listen_buf)) >= 0) {
                 /* TODO somehow find out if cached response was truncated? */
                 memo->state = GCOAP_MEMO_RESP;