From d48eaf15aaba75a6b4e55de590675d53461a4255 Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benjamin.valentin@ml-pa.com>
Date: Thu, 7 Aug 2025 17:26:57 +0200
Subject: [PATCH] nanocoap_server: use zero-copy network buffer for parsing
 request

---
 sys/include/net/nanocoap_sock.h           | 11 +++++------
 sys/net/application_layer/nanocoap/sock.c | 23 ++++++++++++++++-------
 2 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/sys/include/net/nanocoap_sock.h b/sys/include/net/nanocoap_sock.h
index 7559b29f07..9c57176688 100644
--- a/sys/include/net/nanocoap_sock.h
+++ b/sys/include/net/nanocoap_sock.h
@@ -476,18 +476,17 @@ static inline uint16_t nanocoap_sock_next_msg_id(nanocoap_sock_t *sock)
 }
 
 /**
- * @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
diff --git a/sys/net/application_layer/nanocoap/sock.c b/sys/net/application_layer/nanocoap/sock.c
index 8df1547ade..19cee5ecd9 100644
--- a/sys/net/application_layer/nanocoap/sock.c
+++ b/sys/net/application_layer/nanocoap/sock.c
@@ -1131,7 +1131,7 @@ ssize_t nanocoap_get_blockwise_to_buf(nanocoap_sock_t *sock, const char *path,
     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 @@ int nanocoap_server(sock_udp_ep_t *local, uint8_t *buf, size_t bufsize)
 
     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 @@ int nanocoap_server(sock_udp_ep_t *local, uint8_t *buf, size_t bufsize)
         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 @@ int nanocoap_server(sock_udp_ep_t *local, uint8_t *buf, size_t bufsize)
         }
         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;