From df90dfd7b1ab69661d09b1da713ba4bcddbd7a47 Mon Sep 17 00:00:00 2001
From: Jon Shallow <supjps-libcoap@jpshallow.com>
Date: Mon, 11 May 2026 15:44:21 +0100
Subject: [PATCH] coap_subscribe.c: Sanity check persist startup logic

---
 include/coap3/coap_resource_internal.h | 11 +++++++++
 src/coap_net.c                         | 20 ++--------------
 src/coap_resource.c                    | 33 +++++++++++++++++++++++++-
 src/coap_subscribe.c                   | 17 +++++--------
 4 files changed, 51 insertions(+), 30 deletions(-)

diff --git a/include/coap3/coap_resource_internal.h b/include/coap3/coap_resource_internal.h
index 5d107a07..b094afda 100644
--- a/include/coap3/coap_resource_internal.h
+++ b/include/coap3/coap_resource_internal.h
@@ -253,6 +253,17 @@ coap_print_status_t coap_print_wellknown_lkd(coap_context_t *context,
                                              size_t offset,
                                              const coap_string_t *query_filter);
 
+/**
+ * Check to see if a dynamic resource needs to be added.
+ *
+ * @param session Session potentiall adding a new dynamic resource.
+ * @param pdu     PDU that is asking for an unknown resource.
+ *
+ * @return Created resource or NULL is resource eneration not applicable.
+ */
+coap_resource_t *coap_add_dynamic_resource(coap_session_t *session,
+                                           coap_pdu_t *pdu);
+
 /** @} */
 
 #endif /* COAP_SERVER_SUPPORT */
diff --git a/src/coap_net.c b/src/coap_net.c
index 8396396a..d26630a9 100644
--- a/src/coap_net.c
+++ b/src/coap_net.c
@@ -3870,28 +3870,12 @@ handle_request(coap_context_t *context, coap_session_t *session, coap_pdu_t *pdu
                      uri_path->s);
       resp = 202;
       goto fail_response;
-    } else if ((context->dyn_create_handler != NULL) &&
-               (pdu->code == COAP_REQUEST_CODE_PUT || pdu->code == COAP_REQUEST_CODE_POST)) {
-      /* Above test must be the same as in coap_op_dyn_resource_load_disk() */
-      if (context->dynamic_cur < context->dynamic_max || context->dynamic_max == 0) {
-#if COAP_WITH_OBSERVE_PERSIST
-        /* If we are maintaining Observe persist */
-        context->unknown_pdu = pdu;
-        context->unknown_session = session;
-#endif /* COAP_WITH_OBSERVE_PERSIST */
-        coap_lock_callback_ret(resource, context->dyn_create_handler(session, pdu));
-#if COAP_WITH_OBSERVE_PERSIST
-        /* If we are maintaining Observe persist */
-        context->unknown_pdu = NULL;
-        context->unknown_session = NULL;
-#endif /* COAP_WITH_OBSERVE_PERSIST */
-      }
+    } else if (context->dyn_create_handler != NULL) {
+      resource = coap_add_dynamic_resource(session, pdu);
       if (!resource) {
         resp = 406;
         goto fail_response;
       }
-      context->dynamic_cur++;
-      resource->is_dynamic = 1;
     } else { /* request for any another resource, return 4.04 */
 
       coap_log_debug("request for unknown resource '%*.*s', return 4.04\n",
diff --git a/src/coap_resource.c b/src/coap_resource.c
index 093cc0bc..f154b1cc 100644
--- a/src/coap_resource.c
+++ b/src/coap_resource.c
@@ -1572,4 +1572,35 @@ void
 coap_resource_reference_lkd(coap_resource_t *resource) {
   resource->ref++;
 }
-#endif /* ! COAP_SERVER_SUPPORT */
+
+coap_resource_t *
+coap_add_dynamic_resource(coap_session_t *session, coap_pdu_t *pdu) {
+  coap_context_t *context = session->context;
+  coap_resource_t *resource;
+
+  if ((context->dyn_create_handler != NULL) &&
+      (pdu->code == COAP_REQUEST_CODE_PUT || pdu->code == COAP_REQUEST_CODE_POST)) {
+    /* Above test must be the same as in coap_op_dyn_resource_load_disk() */
+    if (context->dynamic_cur < context->dynamic_max || context->dynamic_max == 0) {
+#if COAP_WITH_OBSERVE_PERSIST
+      /* If we are maintaining Observe persist */
+      context->unknown_pdu = pdu;
+      context->unknown_session = session;
+#endif /* COAP_WITH_OBSERVE_PERSIST */
+      coap_lock_callback_ret(resource, context->dyn_create_handler(session, pdu));
+#if COAP_WITH_OBSERVE_PERSIST
+      /* If we are maintaining Observe persist */
+      context->unknown_pdu = NULL;
+      context->unknown_session = NULL;
+#endif /* COAP_WITH_OBSERVE_PERSIST */
+      if (resource) {
+        context->dynamic_cur++;
+        resource->is_dynamic = 1;
+      }
+      return resource;
+    }
+  }
+  return NULL;
+}
+
+#endif /* COAP_SERVER_SUPPORT */
diff --git a/src/coap_subscribe.c b/src/coap_subscribe.c
index b5b7774e..33483dc7 100644
--- a/src/coap_subscribe.c
+++ b/src/coap_subscribe.c
@@ -979,17 +979,12 @@ coap_op_dyn_resource_load_disk(coap_context_t *ctx) {
                           raw_packet->length, request)) {
         goto fail;
       }
-      r = ctx->unknown_resource;
-      if ((ctx->dyn_create_handler != NULL) &&
-          (request->code == COAP_REQUEST_CODE_PUT || request->code == COAP_REQUEST_CODE_POST)) {
-        /* Above test must be the same as in handle_request() */
-        if (ctx->dynamic_cur < ctx->dynamic_max || ctx->dynamic_max == 0) {
-          ctx->unknown_pdu = request;
-          ctx->unknown_session = session;
-          coap_lock_callback_ret(r, ctx->dyn_create_handler(session, request));
-          ctx->unknown_pdu = NULL;
-          ctx->unknown_session = NULL;
-        }
+      if (!COAP_PDU_IS_REQUEST(request)) {
+        goto next;
+      }
+      r = coap_add_dynamic_resource(session, request);
+      if (!r) {
+        r = ctx->unknown_resource;
       }
       if (!r || !r->handler[request->code-1])
         goto next;