Capture: Fix second and future stats open (sparklines) on Windows

We create the dummy signal pipe only allowing one instance, so close
the handle when we're done with it (and set it to NULL, so we'll
create another one.)

If creating the dummy signal pipe fails, return failure and set the
error message.

Log error messages on failure of capture_stat_start()

Fix #15470

capture/capture_sync.c

@@ -94,7 +94,7 @@
 #include <wsutil/ws_pipe.h>
 
 #ifdef _WIN32
-static void create_dummy_signal_pipe(void);
+static int create_dummy_signal_pipe(char **msg);
 static HANDLE dummy_signal_pipe; /* Dummy named pipe which lets the child check for a dropped connection */
 static char *dummy_control_id;
 #else
@@ -1389,7 +1389,10 @@ sync_interface_stats_open(int *data_read_fd, ws_process_id *fork_child, char **m
 #ifndef DEBUG_CHILD
     argv = sync_pipe_add_arg(argv, &argc, "-Z");
 #ifdef _WIN32
-    create_dummy_signal_pipe();
+    ret = create_dummy_signal_pipe(msg);
+    if (ret == -1) {
+        return -1;
+    }
     argv = sync_pipe_add_arg(argv, &argc, dummy_control_id);
 #else
     argv = sync_pipe_add_arg(argv, &argc, SIGNAL_PIPE_CTRL_ID_NONE);
@@ -1534,7 +1537,10 @@ sync_interface_stats_open(int *data_read_fd, ws_process_id *fork_child, char **m
 int
 sync_interface_stats_close(int *read_fd, ws_process_id *fork_child, char **msg)
 {
-#ifndef _WIN32
+#ifdef _WIN32
+    CloseHandle(dummy_signal_pipe);
+    dummy_signal_pipe = NULL;
+#else
     /*
      * Don't bother waiting for the child. sync_pipe_close_command
      * does this for us on Windows.
@@ -2083,10 +2089,10 @@ sync_pipe_signame(int sig)
 
 #ifdef _WIN32
 
-static void create_dummy_signal_pipe(void) {
+static int create_dummy_signal_pipe(char **msg) {
     char *dummy_signal_pipe_name;
 
-    if (dummy_signal_pipe != NULL) return;
+    if (dummy_signal_pipe != NULL) return 0;
 
     if (!dummy_control_id) {
         dummy_control_id = ws_strdup_printf("%ld.dummy", GetCurrentProcessId());
@@ -2097,6 +2103,12 @@ static void create_dummy_signal_pipe(void) {
     dummy_signal_pipe = CreateNamedPipe(utf_8to16(dummy_signal_pipe_name),
                                   PIPE_ACCESS_OUTBOUND, PIPE_TYPE_BYTE, 1, 65535, 65535, 0, NULL);
     g_free(dummy_signal_pipe_name);
+    if (dummy_signal_pipe == INVALID_HANDLE_VALUE) {
+        *msg = ws_strdup_printf("Couldn't create signal pipe: %s",
+            win32strerror(GetLastError()));
+        return -1;
+    }
+    return 0;
 }
 
 /* tell the child through the signal pipe that we want to quit the capture */

ui/capture.c

@@ -892,7 +892,8 @@ capture_stat_start(capture_options *capture_opts)
             }
         }
     } else {
-        g_free(msg); /* XXX: should we display this to the user ? */
+        ws_warning("%s", msg);
+        g_free(msg); /* XXX: should we display this to the user via the GUI? */
     }
     return sc;
 }