Prevent forwarding threads from sending on closed tunnels

- Add tunnel validity check in forwarding threads before sending data
- Threads check if tunnel is still active in the global list before proceeding
- Prevents SSL write errors and connection corruption when tunnels are closed

wssshtools/tunnel.c

@@ -345,6 +345,13 @@ void *forward_tcp_to_ws(void *arg) {
             continue;
         }
 
+        // Check if tunnel is still active after copying values
+        tunnel_t *check_tunnel = find_tunnel_by_request_id(request_id);
+        if (!check_tunnel || !check_tunnel->active) {
+            pthread_mutex_unlock(&tunnel_mutex);
+            break;
+        }
+
         // For wsscp: The connection should already be established
         int client_sock = sock;
         if (tunnel->sock < 0 && tunnel->outgoing_buffer) {
@@ -522,6 +529,15 @@ void *forward_ws_to_ssh_server(void *arg) {
         strcpy(request_id, tunnel->request_id);
         pthread_mutex_unlock(&tunnel_mutex);
 
+        // Check if tunnel is still active after copying values
+        pthread_mutex_lock(&tunnel_mutex);
+        tunnel_t *check_tunnel = find_tunnel_by_request_id(request_id);
+        if (!check_tunnel || !check_tunnel->active) {
+            pthread_mutex_unlock(&tunnel_mutex);
+            break;
+        }
+        pthread_mutex_unlock(&tunnel_mutex);
+
         // Use select to wait for data on target TCP connection
         FD_ZERO(&readfds);
         FD_SET(target_sock, &readfds);