Improve IPv6 portability and consistency

After  discussions with  Greg  N1DAM  I have  changed  the dual  stack
support to  explicitly allow IPv4  connections mapped to IPv6  for any
AF_INET6 address  since BSD  as well as  Windows defaults  this socket
option to on (disallowed).

IPv4 mapped to IPv6 makes sense  for Hamlib servers since starting two
servers  one  for each  protocol  family  (the  other option)  is  not
possible  since there  is only  a single  rig/rotator which  cannot be
shared between two servers.

tests/rigctld.c

@@ -169,6 +169,7 @@ int main (int argc, char *argv[])
 
 	struct addrinfo hints, *result, *saved_result;
 	int sock_listen;
+	int sockopt;
 	int reuseaddr = 1;
 	char host[NI_MAXHOST];
 	char serv[NI_MAXSERV];
@@ -402,7 +403,7 @@ int main (int argc, char *argv[])
 		exit(1);
 	}
 
-	int sockopt = SO_SYNCHRONOUS_NONALERT;
+	sockopt = SO_SYNCHRONOUS_NONALERT;
 	setsockopt(INVALID_SOCKET, SOL_SOCKET, SO_OPENTYPE, (char *)&sockopt, sizeof(sockopt));
 #endif
 
@@ -439,14 +440,17 @@ int main (int argc, char *argv[])
 				exit (1);
 			}
 
-#if defined(__MINGW32__) && HAVE_WS2TCPIP_H
-			/* allow IPv4 mapped to IPv6 clients, MS default this to 1! */
-			sockopt = 0;
-      if (setsockopt(sock_listen, IPPROTO_IPV6, IPV6_V6ONLY,
-										 (char *)&sockopt, sizeof(sockopt)) < 0) {
-				handle_error (RIG_DEBUG_ERR, "setsockopt");
-				freeaddrinfo(saved_result);		/* No longer needed */
-				exit (1);
+#ifdef IPV6_V6ONLY
+			if (AF_INET6 == result->ai_family) {
+				/* allow IPv4 mapped to IPv6 clients Windows and BSD default
+					 this to 1 (i.e. disallowed) and we prefer it off */
+				sockopt = 0;
+				if (setsockopt(sock_listen, IPPROTO_IPV6, IPV6_V6ONLY,
+											 (char *)&sockopt, sizeof(sockopt)) < 0) {
+					handle_error (RIG_DEBUG_ERR, "setsockopt");
+					freeaddrinfo(saved_result);		/* No longer needed */
+					exit (1);
+				}
 			}
 #endif
 
@@ -588,7 +592,9 @@ void * handle_socket(void *arg)
 						host, serv);
 
 	fclose(fsockin);
+#ifndef __MINGW32__
 	fclose(fsockout);
+#endif
 
 handle_exit:
 #ifdef __MINGW32__

tests/rotctld.c

@@ -158,6 +158,7 @@ int main (int argc, char *argv[])
 	struct addrinfo hints, *result, *saved_result;
 	int sock_listen;
 	int reuseaddr = 1;
+	int sockopt;
 	char host[NI_MAXHOST];
 	char serv[NI_MAXSERV];
 
@@ -314,7 +315,7 @@ int main (int argc, char *argv[])
 		exit(1);
 	}
 
-	int sockopt = SO_SYNCHRONOUS_NONALERT;
+	sockopt = SO_SYNCHRONOUS_NONALERT;
 	setsockopt(INVALID_SOCKET, SOL_SOCKET, SO_OPENTYPE, (char *)&sockopt, sizeof(sockopt));
 #endif
 
@@ -352,14 +353,17 @@ int main (int argc, char *argv[])
 				exit (1);
 			}
 
-#if defined(__MINGW32__) && HAVE_WS2TCPIP_H
-			/* allow IPv4 mapped to IPv6 clients, MS default this to 1! */
-			sockopt = 0;
-      if (setsockopt(sock_listen, IPPROTO_IPV6, IPV6_V6ONLY,
-										 (char *)&sockopt, sizeof(sockopt)) < 0) {
-				handle_error (RIG_DEBUG_ERR, "setsockopt");
-				freeaddrinfo(saved_result);		/* No longer needed */
-				exit (1);
+#ifdef IPV6_V6ONLY
+			if (AF_INET6 == result->ai_family) {
+				/* allow IPv4 mapped to IPv6 clients, MS & BSD default this
+					 to 1 i.e. disallowed */
+				sockopt = 0;
+				if (setsockopt(sock_listen, IPPROTO_IPV6, IPV6_V6ONLY,
+											 (char *)&sockopt, sizeof(sockopt)) < 0) {
+					handle_error (RIG_DEBUG_ERR, "setsockopt");
+					freeaddrinfo(saved_result);		/* No longer needed */
+					exit (1);
+				}
 			}
 #endif
 
@@ -501,7 +505,10 @@ void * handle_socket(void *arg)
 						host, serv);
 
 	fclose(fsockin);
+#ifndef __MINGW32__
 	fclose(fsockout);
+#endif
+
 handle_exit:
 #ifdef __MINGW32__
 	closesocket(handle_data_arg->sock);