session server UPDATE nc_server_destroy return value

Change return type from void to int to allow callers to handle
cleanup failures. Also update nc_server_notif_cert_expiration_thread_stop
to return error code so that nc_server_destroy can properly propagate
errors.

Author: Roytak

src/session_server.c

@@ -1296,9 +1296,10 @@ nc_server_init(void)
     return -1;
 }
 
-API void
+API int
 nc_server_destroy(void)
 {
+    int rc = 0;
     int config_update_locked = 0;
     enum nc_rwlock_mode config_lock_mode = NC_RWLOCK_NONE;
     uint32_t i;
@@ -1312,10 +1313,15 @@ nc_server_destroy(void)
     if (server_opts.content_id_data && server_opts.content_id_data_free) {
         server_opts.content_id_data_free(server_opts.content_id_data);
     }
+    server_opts.content_id_data = NULL;
+    server_opts.content_id_data_free = NULL;
 
 #ifdef NC_ENABLED_SSH_TLS
     /* destroy the certificate expiration notification thread */
-    nc_server_notif_cert_expiration_thread_stop(1);
+    if ((rc = nc_server_notif_cert_expiration_thread_stop(1))) {
+        ERR(NULL, "%s: failed to stop certificate expiration notification thread.", __func__);
+        goto cleanup;
+    }
 #endif /* NC_ENABLED_SSH_TLS */
 
     /* CONFIG UPDATE LOCK, continue on error */
@@ -1380,8 +1386,12 @@ nc_server_destroy(void)
     /* close the TLS keylog file */
     if (server_opts.tls_keylog_file) {
         fclose(server_opts.tls_keylog_file);
+        server_opts.tls_keylog_file = NULL;
     }
 #endif /* NC_ENABLED_SSH_TLS */
+
+cleanup:
+    return rc;
 }
 
 API int
@@ -4753,15 +4763,15 @@ nc_server_notif_cert_expiration_thread_start(nc_cert_exp_notif_clb cert_exp_noti
     return ret;
 }
 
-API void
+API int
 nc_server_notif_cert_expiration_thread_stop(int wait)
 {
     int r;
     pthread_t tid;
 
     /* LOCK */
     if (nc_mutex_lock(&server_opts.cert_exp_notif.lock, NC_CERT_EXP_LOCK_TIMEOUT, __func__) != 1) {
-        return;
+        return 1;
     }
     tid = server_opts.cert_exp_notif.tid;
 
@@ -4780,12 +4790,14 @@ nc_server_notif_cert_expiration_thread_stop(int wait)
         }
         if (r) {
             ERR(NULL, "Stopping the certificate expiration notification thread failed (%s).", strerror(r));
+            return 1;
         }
     } else {
         /* thread is not running */
         /* UNLOCK */
         nc_mutex_unlock(&server_opts.cert_exp_notif.lock, __func__);
     }
+    return 0;
 }
 
 #endif /* NC_ENABLED_SSH_TLS */

src/session_server.h

@@ -144,8 +144,12 @@ int nc_server_init(void);
 /**
  * @brief Destroy any dynamically allocated libssh and/or libssl/libcrypto and
  *        server resources.
+ *
+ * Can be called multiple times, even if a previous call failed.
+ *
+ * @return 0 on success, 1 on error - all resources could not be freed safely.
  */
-void nc_server_destroy(void);
+int nc_server_destroy(void);
 
 /**
  * @brief Initialize a context which can serve as a default server context.
@@ -668,9 +672,12 @@ int nc_server_notif_cert_expiration_thread_start(nc_cert_exp_notif_clb cert_exp_
 /**
  * @brief Stop the certificate expiration notification thread.
  *
+ * Can be called multiple times. If the thread is not running, does nothing and returns 0.
+ *
  * @param[in] wait Boolean representing whether to block and wait for the thread to finish.
+ * @return 0 on success, 1 on error.
  */
-void nc_server_notif_cert_expiration_thread_stop(int wait);
+int nc_server_notif_cert_expiration_thread_stop(int wait);
 
 #endif /* NC_ENABLED_SSH_TLS */