Fix segmentation fault when closing concurrent tunnels

- Add forward_thread field to tunnel_t structure for thread synchronization
- Remove pthread_detach() to allow proper thread joining during cleanup
- Add pthread_join() in cleanup to wait for forwarding thread completion
- Prevent race conditions between cleanup and forwarding threads
- Ensure tunnel resources are not freed while threads are still using them
- Fix concurrent connection cleanup issues in wsssht daemon mode

wssshtools/libwsssht/modes.c

@@ -652,6 +652,7 @@ void *handle_connection(void *arg) {
     new_tunnel->outgoing_buffer = NULL;
     new_tunnel->incoming_buffer = frame_buffer_init();
     new_tunnel->server_version_sent = 0;
+    new_tunnel->forward_thread = 0;
 
     if (!new_tunnel->incoming_buffer) {
         perror("Failed to initialize incoming buffer");
@@ -858,8 +859,16 @@ void *handle_connection(void *arg) {
     thread_args->debug = config->debug;
 
     pthread_t forward_thread;
-    pthread_create(&forward_thread, NULL, forward_tcp_to_ws, thread_args);
-    pthread_detach(forward_thread);
+    if (pthread_create(&forward_thread, NULL, forward_tcp_to_ws, thread_args) != 0) {
+        perror("Failed to create forwarding thread");
+        free(thread_args);
+        close(new_tunnel->local_sock);
+        frame_buffer_free(new_tunnel->incoming_buffer);
+        free(new_tunnel);
+        return NULL;
+    }
+    // Store the thread ID for cleanup
+    new_tunnel->forward_thread = forward_thread;
 
     // Main tunnel loop - handle WebSocket messages
     char ws_buffer[BUFFER_SIZE];
@@ -1245,6 +1254,19 @@ cleanup_and_exit:
         fflush(stdout);
     }
 
+    // Wait for forwarding thread to finish
+    if (new_tunnel && new_tunnel->forward_thread) {
+        if (config->debug) {
+            printf("[DEBUG - Tunnel] [Thread %ld] Waiting for forwarding thread to finish\n", pthread_self());
+            fflush(stdout);
+        }
+        pthread_join(new_tunnel->forward_thread, NULL);
+        if (config->debug) {
+            printf("[DEBUG - Tunnel] [Thread %ld] Forwarding thread finished\n", pthread_self());
+            fflush(stdout);
+        }
+    }
+
     // Cleanup
     if (new_tunnel) {
         if (new_tunnel->local_sock >= 0) {

wssshtools/tunnel.h

@@ -41,6 +41,7 @@ typedef struct {
     frame_buffer_t *outgoing_buffer;  // Buffer for data to send to local socket (wsscp only)
     frame_buffer_t *incoming_buffer;  // Buffer for incoming data before connection is established
     int server_version_sent;  // Flag to indicate if server version was sent early
+    pthread_t forward_thread;  // Thread ID for the forwarding thread
 } tunnel_t;
 
 // Thread arguments