From df95d5bcc3ce5a016d107d6f97aad22ba3d140f2 Mon Sep 17 00:00:00 2001
From: Jon Shallow <supjps-libcoap@jpshallow.com>
Date: Mon, 24 Mar 2025 16:04:12 +0000
Subject: [PATCH] Proxy: Ignore idle timeout if observe subscription on session

Ignore the idle_timeout_secs parameter for a server if there is one
or more active observe subscriptions for the server session.
---
 include/coap3/coap_proxy.h          |  4 +++-
 include/coap3/coap_proxy_internal.h |  6 +++++-
 man/coap_proxy.txt.in               |  4 +++-
 src/coap_proxy.c                    | 32 ++++++++++++++++++++++-------
 4 files changed, 36 insertions(+), 10 deletions(-)

diff --git a/include/coap3/coap_proxy.h b/include/coap3/coap_proxy.h
index 8946000a..83341003 100644
--- a/include/coap3/coap_proxy.h
+++ b/include/coap3/coap_proxy.h
@@ -60,7 +60,9 @@ typedef struct coap_proxy_server_list_t {
                                    server, else 0 for all clients to share the same
                                    ongoing session */
   unsigned int idle_timeout_secs; /**< Proxy upstream session idle timeout
-                                       (0 is no timeout) */
+                                       (0 is no timeout). Timeout is ignored
+                                       if there are any active upstream Observe
+                                       requests */
 } coap_proxy_server_list_t;
 
 /**
diff --git a/include/coap3/coap_proxy_internal.h b/include/coap3/coap_proxy_internal.h
index cfc585c1..b24ccc12 100644
--- a/include/coap3/coap_proxy_internal.h
+++ b/include/coap3/coap_proxy_internal.h
@@ -41,8 +41,12 @@ struct coap_proxy_list_t {
   size_t req_count;          /**< Count of incoming request info */
   coap_uri_t uri;            /**< URI info for connection */
   uint8_t *uri_host_keep;     /**< memory for uri.host */
-  coap_tick_t idle_timeout_ticks; /**< Idle timeout (0 == no timeout) */
+  coap_tick_t idle_timeout_ticks; /**< Idle timeout (0 == no timeout). Timeout
+                                       is ignored if there are any active
+                                       upstream Observe requests */
   coap_tick_t last_used;     /**< Last time entry was used */
+  uint64_t res_tx_token;     /**< Copy of ongoing session tx_token for restart */
+  coap_lg_crcv_t *res_lg_crcv; /**< Copy of ongoing session lg_crcv for restart */
 };
 
 /**
diff --git a/man/coap_proxy.txt.in b/man/coap_proxy.txt.in
index 9c6bbcea..b5f06750 100644
--- a/man/coap_proxy.txt.in
+++ b/man/coap_proxy.txt.in
@@ -137,7 +137,9 @@ typedef struct coap_proxy_server_list_t {
                                  server, else 0 for all clients to share the
                                  same ongoing session */
   unsigned int idle_timeout_secs; /* Proxy upstream session idle timeout
-                                     (0 is no timeout) */
+                                     (0 is no timeout). Timeout is ignored
+                                     if there are any active upstream Observe
+                                     requests */
 } coap_proxy_server_list_t;
 ----
 
diff --git a/src/coap_proxy.c b/src/coap_proxy.c
index 4a61e551..f031029d 100644
--- a/src/coap_proxy.c
+++ b/src/coap_proxy.c
@@ -51,6 +51,21 @@ coap_proxy_cleanup(coap_context_t *context) {
   coap_free_type(COAP_STRING, context->proxy_list);
 }
 
+static int
+coap_proxy_check_observe(coap_proxy_list_t *proxy_entry) {
+  if (proxy_entry && proxy_entry->ongoing) {
+    /* Need to see if there are any Observes active */
+    coap_lg_crcv_t *lg_crcv;
+
+    LL_FOREACH(proxy_entry->ongoing->lg_crcv, lg_crcv) {
+      if (lg_crcv->observe_set) {
+        return 1;
+      }
+    }
+  }
+  return 0;
+}
+
 /*
  * return 1 if there is a future expire time, else 0.
  * update tim_rem with remaining value if return is 1.
@@ -63,16 +78,19 @@ coap_proxy_check_timeouts(coap_context_t *context, coap_tick_t now,
 
   *tim_rem = -1;
   for (i = 0; i < context->proxy_list_count; i++) {
-    coap_proxy_list_t *proxy_list = &context->proxy_list[i];
+    coap_proxy_list_t *proxy_entry = &context->proxy_list[i];
 
-    if (proxy_list->ongoing && proxy_list->idle_timeout_ticks) {
-      if (proxy_list->last_used + proxy_list->idle_timeout_ticks <= now) {
+    if (coap_proxy_check_observe(proxy_entry))
+      continue;
+
+    if (proxy_entry->ongoing && proxy_entry->idle_timeout_ticks) {
+      if (proxy_entry->last_used + proxy_entry->idle_timeout_ticks <= now) {
         /* Drop session to upstream server */
-        coap_session_release_lkd(proxy_list->ongoing);
-        proxy_list->ongoing = NULL;
+        coap_session_release_lkd(proxy_entry->ongoing);
+        proxy_entry->ongoing = NULL;
       } else {
-        if (*tim_rem > proxy_list->last_used + proxy_list->idle_timeout_ticks - now) {
-          *tim_rem = proxy_list->last_used + proxy_list->idle_timeout_ticks - now;
+        if (*tim_rem > proxy_entry->last_used + proxy_entry->idle_timeout_ticks - now) {
+          *tim_rem = proxy_entry->last_used + proxy_entry->idle_timeout_ticks - now;
         }
         ret = 1;
       }