Those lines are not needed since "netdissect-stdinc.h" has:
#include <winsock2.h>
#include <ws2tcpip.h>
This will ensure <winsock.h> is not included in a later <windows.h>.
SIZE_BUF is not used anywhere AFAICS.
#include <netdissect-stdinc.h>
#ifdef _WIN32
#include <netdissect-stdinc.h>
#ifdef _WIN32
-#ifndef _WINSOCKAPI_
-#define _WINSOCKAPI_ /* Prevent inclusion of winsock.h in windows.h */
-#endif /* _WINSOCKAPI_ */
-#include <windows.h>
-#include <winsock2.h>
-extern int SIZE_BUF;
#define off_t long
#define uint UINT
#endif /* _WIN32 */
#define off_t long
#define uint UINT
#endif /* _WIN32 */