Cygwin: tcp: fix IPPROTO_TCP option handling

- Drop definitions from <cygwin/sockets.h>
- Drop options only available on BSD
- Fix value of TCP_MAXSEG.  It was still defined as the BSD value
  while WinSock uses another value
- Handle the fact that TCP_MAXSEG is a R/O value in WinSock

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/fhandler_socket_inet.cc

@@ -23,6 +23,7 @@
 #endif
 #include <w32api/ws2tcpip.h>
 #include <w32api/mswsock.h>
+#include <netinet/tcp.h>
 #include <unistd.h>
 #include <asm/byteorder.h>
 #include <sys/socket.h>
@@ -1682,6 +1683,20 @@ fhandler_socket_inet::setsockopt (int level, int optname, const void *optval,
       }
     default:
       break;
+
+    case IPPROTO_TCP:
+      switch (optname)
+	{
+	case TCP_MAXSEG:
+	  /* Winsock doesn't support setting TCP_MAXSEG, only requesting it
+	     via getsockopt.  Make this a no-op. */
+	  ignore = true;
+	  break;
+
+	default:
+	  break;
+	}
+      break;
     }
 
   /* Call Winsock setsockopt (or not) */

winsup/cygwin/include/cygwin/socket.h

@@ -300,12 +300,6 @@ struct OLD_msghdr
 /* IPX options */
 #define IPX_TYPE	1
 
-/* TCP options - this way around because someone left a set in the c library includes */
-#ifndef TCP_NODELAY
-#define TCP_NODELAY     0x0001
-#define TCP_MAXSEG	2
-#endif
-
 /* SUS symbolic values for the second parm to shutdown(2) */
 #define SHUT_RD   0		/* == Win32 SD_RECEIVE */
 #define SHUT_WR   1		/* == Win32 SD_SEND    */

winsup/cygwin/include/netinet/tcp.h

@@ -123,11 +123,7 @@ struct tcphdr {
 /*
  * User-settable options (used with setsockopt).
  */
-#ifndef TCP_NODELAY
 #define TCP_NODELAY     0x01    /* don't delay send to coalesce packets */
-#define TCP_MAXSEG      0x02    /* set maximum segment size */
-#endif
-#define TCP_NOPUSH      0x04    /* don't push last block of write */
-#define TCP_NOOPT       0x08    /* don't use TCP options */
+#define TCP_MAXSEG      0x04    /* get maximum segment size (r/o on windows) */
 
 #endif