Fix disabling IPV6_V6ONLY on sockets, issue #511

src/listensocket.cpp

@@ -33,11 +33,6 @@ ListenSocket::ListenSocket(ConfigTag* tag, const irc::sockets::sockaddrs& bind_t
 	if (this->fd == -1)
 		return;
 
-	ServerInstance->SE->SetReuse(fd);
-	int rv = ServerInstance->SE->Bind(this->fd, bind_to);
-	if (rv >= 0)
-		rv = ServerInstance->SE->Listen(this->fd, ServerInstance->Config->MaxConn);
-
 #ifdef IPV6_V6ONLY
 	/* This OS supports IPv6 sockets that can also listen for IPv4
 	 * connections. If our address is "*" or empty, enable both v4 and v6 to
@@ -48,12 +43,19 @@ ListenSocket::ListenSocket(ConfigTag* tag, const irc::sockets::sockaddrs& bind_t
 	if (bind_to.sa.sa_family == AF_INET6)
 	{
 		std::string addr = tag->getString("address");
-		const char enable = (addr.empty() || addr == "*") ? 0 : 1;
-		setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &enable, sizeof(enable));
+		/* This must be >= sizeof(DWORD) on Windows */
+		const int enable = (addr.empty() || addr == "*") ? 0 : 1;
+		/* This must be before bind() */
+		setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, reinterpret_cast<const char *>(&enable), sizeof(enable));
 		// errors ignored intentionally
 	}
 #endif
 
+	ServerInstance->SE->SetReuse(fd);
+	int rv = ServerInstance->SE->Bind(this->fd, bind_to);
+	if (rv >= 0)
+		rv = ServerInstance->SE->Listen(this->fd, ServerInstance->Config->MaxConn);
+
 	if (rv < 0)
 	{
 		int errstore = errno;