nanocoap_server: use zero-copy network buffer for parsing request

sys/include/net/nanocoap_sock.h

@@ -310,7 +310,7 @@
  * @param[in]   len     Payload length
  *
  * @retval      0               Success
  * @retval      -ECANCELED      Request contained no-response option that did match the given @p code
  * @retval      <0              Negative errno code indicating the error
  */
 int nanocoap_server_send_separate(const nanocoap_server_response_ctx_t *ctx,
@@ -339,7 +339,7 @@
  * @param[in]   msg_id  Message ID to send
  *
  * @return      Length of the header build in bytes
  * @retval      -ECANCELED      Request contained no-response option that did match the given @p code
  * @retval      <0              Negative errno code indicating the error
  */
 ssize_t nanocoap_server_build_separate(const nanocoap_server_response_ctx_t *ctx,
@@ -476,18 +476,17 @@
 }
 
 /**
- * @brief   Start a nanocoap server instance
+ * @brief   Start a nanoCoAP server instance
  *
- * This function only returns if there's an error binding to @p local, or if
- * receiving of UDP packets fails.
+ * This function only returns if there's an error binding to @p local.
  *
  * @param[in]   local   local UDP endpoint to bind to
- * @param[in]   buf     input buffer to use
+ * @param[in]   buf     response buffer to use
  * @param[in]   bufsize size of @p buf
  *
- * @returns     -1 on error
+ * @returns     return code of @see sock_udp_create on error
  */
-int nanocoap_server(sock_udp_ep_t *local, uint8_t *buf, size_t bufsize);
+int nanocoap_server(sock_udp_ep_t *local, void *buf, size_t bufsize);
 
 /**
  * @brief   Create and start the nanoCoAP server thread

sys/net/application_layer/nanocoap/nanocoap.c

@@ -778,6 +778,9 @@
                    ntohs(pkt->hdr->id));
     len += payload_len;
 
+    /* HACK: many CoAP handlers assume that the pkt buffer is also used for the response */
+    pkt->hdr = (void *)rbuf;
+
     return len;
 }
 
@@ -983,7 +986,7 @@
     return offset;
 }
 
 size_t coap_put_option(uint8_t *buf, uint16_t lastonum, uint16_t onum, const void *odata, size_t olen)
 {
     assert(lastonum <= onum);
 

sys/net/application_layer/nanocoap/sock.c

@@ -248,7 +248,7 @@
 
     /* random timeout, deadline for receive retries */
     uint32_t timeout = random_uint32_range((uint32_t)CONFIG_COAP_ACK_TIMEOUT_MS * US_PER_MS,
                                            (uint32_t)CONFIG_COAP_ACK_TIMEOUT_MS * CONFIG_COAP_RANDOM_FACTOR_1000);
     uint32_t deadline = _deadline_from_interval(timeout);
 
     /* check if we expect a reply */
@@ -1131,7 +1131,7 @@
     return (res < 0) ? (ssize_t)res : (ssize_t)_buf.len;
 }
 
-int nanocoap_server(sock_udp_ep_t *local, uint8_t *buf, size_t bufsize)
+int nanocoap_server(sock_udp_ep_t *local, void *rsp_buf, size_t rsp_buf_len)
 {
     sock_udp_t sock;
     sock_udp_ep_t remote;
@@ -1145,11 +1145,20 @@
 
     ssize_t res = sock_udp_create(&sock, local, NULL, 0);
     if (res != 0) {
-        return -1;
+        return res;
     }
 
+    void *buf;
+    void *buf_ctx = NULL;
+
     while (1) {
 
+        if (buf_ctx) {
+            /* free the buffer */
+            res = sock_udp_recv_buf_aux(&sock, &buf, &buf_ctx, 0, NULL, NULL);
+            assert(res == 0);
+        }
+
         sock_udp_aux_rx_t *aux_in_ptr = NULL;
 #ifdef MODULE_SOCK_AUX_LOCAL
         sock_udp_aux_rx_t aux_in = {
@@ -1158,14 +1167,14 @@
         aux_in_ptr = &aux_in;
 #endif
 
-        res = sock_udp_recv_aux(&sock, buf, bufsize, SOCK_NO_TIMEOUT,
-                                &remote, aux_in_ptr);
+        res = sock_udp_recv_buf_aux(&sock, &buf, &buf_ctx, SOCK_NO_TIMEOUT,
+                                    &remote, aux_in_ptr);
         if (res <= 0) {
             DEBUG("nanocoap: error receiving UDP packet %" PRIdSIZE "\n", res);
             continue;
         }
         coap_pkt_t pkt;
-        if (coap_parse(&pkt, (uint8_t *)buf, res) < 0) {
+        if (coap_parse(&pkt, buf, res) < 0) {
             DEBUG("nanocoap: error parsing packet\n");
             continue;
         }
@@ -1183,12 +1192,12 @@
         }
         ctx.local = &aux_in.local;
 #endif
-        if ((res = coap_handle_req(&pkt, buf, bufsize, &ctx)) <= 0) {
+        if ((res = coap_handle_req(&pkt, rsp_buf, rsp_buf_len, &ctx)) <= 0) {
             DEBUG("nanocoap: error handling request %" PRIdSIZE "\n", res);
             continue;
         }
 
-        sock_udp_send_aux(&sock, buf, res, &remote, aux_out_ptr);
+        sock_udp_send_aux(&sock, rsp_buf, res, &remote, aux_out_ptr);
     }
 
     return 0;
@@ -1396,7 +1405,7 @@
                 && (_observer_pool[i].response.tkl == coap_get_token_len(req_pkt))
                 && !memcmp(_observer_pool[i].response.token, coap_get_token(req_pkt),
                            _observer_pool[i].response.tkl)
                 && sock_udp_ep_equal(&_observer_pool[i].response.remote, coap_request_ctx_get_remote_udp(req_ctx))) {
             DEBUG("nanocoap: observer at index %" PRIuSIZE " unregistered\n", i);
             _observer_pool[i].resource = NULL;
         }
@@ -1427,7 +1436,7 @@
         if (_observer_pool[i].resource == res) {
             uint8_t rbuf[sizeof(coap_hdr_t) + COAP_TOKEN_LENGTH_MAX + 1];
 
             ssize_t hdr_len = nanocoap_server_build_separate(&_observer_pool[i].response, rbuf, sizeof(rbuf),
                                                              COAP_CODE_CONTENT, COAP_TYPE_NON,
                                                              ++_observer_pool[i].msg_id);
             if (hdr_len < 0) {