fixup! nanocoap: add coap_build_reply_header()

RIOT-OS · Jan 23, 2024 · 8930092 · 8930092
1 parent 3d25404
commit 8930092
Showing 1 changed file with 6 additions and 2 deletions.
diff --git a/sys/net/application_layer/nanocoap/nanocoap.c b/sys/net/application_layer/nanocoap/nanocoap.c
@@ -591,10 +591,14 @@ ssize_t coap_build_reply_header(coap_pkt_t *pkt, unsigned code,
         }
         *bufpos++ = COAP_PAYLOAD_MARKER;
         *payload = bufpos;
-        *payload_len_max = len - (bufpos - (uint8_t *)buf);
+        hdr_len += bufpos - (uint8_t *)buf;
+        *payload_len_max = len - hdr_len;
     }
 
-    return bufpos - (uint8_t *)buf;
+    /* with the nanoCoAP API we can't detect the overflow before it happens */
+    assert(hdr_len <= len);
+
+    return hdr_len;
 }
 
 ssize_t coap_reply_simple(coap_pkt_t *pkt,