From 28b917a72e59583119ad09664a1de5d042aa7e9a Mon Sep 17 00:00:00 2001
From: Roland Knall <rknall@gmail.com>
Date: Mon, 16 May 2022 14:48:37 +0200
Subject: [PATCH] extcap: Close pipe on windows properly

Windows implements so called CRT handlers, which will catch any
assertions happening inside so called crt routines and either
displays a debug dialog (Cancel, Retry, Ignore) or outright crashes
the application.

See
https://docs.microsoft.com/en-us/cpp/c-runtime-library/parameter-validation?view=msvc-170
for an explanation of the behaviour.

Now, in the current situation here, close will detect (correctly)
that the pipe it is supposed to be closing is already closed. This
happens (again correctly) because it had been closed by the extcap
application.

The change added, checks for a closed pipe first, and if so just
returns -1 (as it should) silently without calling the CRT routine,
therefore not crashing
---
 ui/qt/interface_toolbar.cpp |  3 ++-
 wsutil/file_util.c          | 16 ++++++++++++++++
 wsutil/file_util.h          |  7 +++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/ui/qt/interface_toolbar.cpp b/ui/qt/interface_toolbar.cpp
index 911b0bb56d..b0580b2fa3 100644
--- a/ui/qt/interface_toolbar.cpp
+++ b/ui/qt/interface_toolbar.cpp
@@ -803,7 +803,8 @@ void InterfaceToolbar::stopCapture()
 
         if (interface_[ifname].out_fd != -1)
         {
-            ws_close (interface_[ifname].out_fd);
+            ws_close_if_possible (interface_[ifname].out_fd);
+
             interface_[ifname].out_fd = -1;
         }
 
diff --git a/wsutil/file_util.c b/wsutil/file_util.c
index a7bbaa081e..c747d3e0a2 100644
--- a/wsutil/file_util.c
+++ b/wsutil/file_util.c
@@ -51,6 +51,7 @@
 #include <glib.h>
 
 #include <windows.h>
+#include <winsock2.h>
 #include <errno.h>
 #include <wchar.h>
 #include <tchar.h>
@@ -668,6 +669,21 @@ void close_app_running_mutex() {
     }
 }
 
+int ws_close_if_possible(int fd) {
+    fd_set rfds;
+    struct timeval tv = { 0, 1 };
+    int retval;
+
+    FD_ZERO(&rfds);
+    FD_SET(fd, &rfds);
+
+    retval = select(1, &rfds, NULL, NULL, &tv);
+    if (retval > -1)
+        return _close(fd);
+
+    return -1;
+}
+
 /*
  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
  *
diff --git a/wsutil/file_util.h b/wsutil/file_util.h
index 7aa150e9ce..ab4c650f0b 100644
--- a/wsutil/file_util.h
+++ b/wsutil/file_util.h
@@ -165,6 +165,10 @@ WS_DLL_PUBLIC void create_app_running_mutex(void);
  */
 WS_DLL_PUBLIC void close_app_running_mutex(void);
 
+/** Close a file descriptor if it is not open
+ */
+WS_DLL_PUBLIC int ws_close_if_possible(int fd);
+
 #else	/* _WIN32 */
 
 /*
@@ -195,6 +199,9 @@ typedef ssize_t ws_file_ssize_t;
 #else
 #define ws_close   close
 #endif
+
+#define ws_close_if_possible ws_close
+
 #define ws_dup     dup
 #ifdef HAVE_FSEEKO
 #define ws_fseek64 fseeko	/* AC_SYS_LARGEFILE should make off_t 64-bit */