extcap: Read stdout and stderr during capture

Read extcap stdout/stderr data when available to prevent extcap hang on
stdout/stderr write. Discard stdout data as it was not used earlier.
Store up to 1024 bytes of stderr and display it to user after capture
stops.

Fixes #17827

1 files changed, 3 insertions, 1 deletions

diff --git a/capture_opts.h b/capture_opts.h
index 8a29b8299b..2508b850b7 100644
--- a/capture_opts.h
+++ b/capture_opts.h
@@ -210,8 +210,10 @@ typedef struct interface_options_tag {
     GHashTable       *extcap_args;
     GPid              extcap_pid;           /* pid of running process or WS_INVALID_PID */
     gpointer          extcap_pipedata;
-    gchar            *extcap_stderr;
+    GString          *extcap_stderr;
     guint             extcap_child_watch;
+    guint             extcap_stdout_watch;
+    guint             extcap_stderr_watch;
 #ifdef _WIN32
     HANDLE            extcap_pipe_h;
     HANDLE            extcap_control_in_h;