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>
(cherry picked from commit 1e938c50930f29124909e120a29fb116d4c46576)

diff --git a/src/openvpnserv/common.c b/src/openvpnserv/common.c
index 958643dfd0e8a065702a8a3a7498665a10ceab08..6e6deae63539eac3a004f585f35b9992024ba5c9 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)