openvpnserv: Cache last error before it is overridden

FormatMessage() sets the last error according to its own success. This
looses the original error code leading to mismatched error message and
error number when sprintfted together resulting in confusing event log
message.

Signed-off-by: Simon Rozman <simon@rozman.si>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20210322103957.1234-1-simon@rozman.si>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg21789.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

diff --git a/src/openvpnserv/common.c b/src/openvpnserv/common.c
index 48769be488f6746b79c9b58dc1479224a014c73c..ebd0867703ae4b8bc9fa25d1f18aa3b0ad694674 100644 (file)
--- a/src/openvpnserv/common.c
+++ b/src/openvpnserv/common.c
@@ -228,12 +228,14 @@ out:
 LPCTSTR
 GetLastErrorText()
 {
+    DWORD error;
     static TCHAR buf[256];
     DWORD len;
     LPTSTR tmp = NULL;
 
+    error = GetLastError();
     len = FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ARGUMENT_ARRAY,
-                        NULL, GetLastError(), LANG_NEUTRAL, (LPTSTR)&tmp, 0, NULL);
+                        NULL, error, LANG_NEUTRAL, (LPTSTR)&tmp, 0, NULL);
 
     if (len == 0 || (long) _countof(buf) < (long) len + 14)
     {
@@ -242,7 +244,7 @@ GetLastErrorText()
     else
     {
         tmp[_tcslen(tmp) - 2] = TEXT('\0'); /* remove CR/LF characters */
-        openvpn_sntprintf(buf, _countof(buf), TEXT("%s (0x%x)"), tmp, GetLastError());
+        openvpn_sntprintf(buf, _countof(buf), TEXT("%s (0x%x)"), tmp, error);
     }
 
     if (tmp)