[core,tcp] Improve IPv4 or IPv6 connect

* Fix +ipv6 option, now fall back to IPv4 if no IPv6 entry found
* Add new option ForceIPvX to fail connect if no such entry is found

client/common/cmdline.c

@@ -4554,10 +4554,31 @@ static int freerdp_client_settings_parse_command_line_arguments_int(
 			if (!freerdp_settings_set_bool(settings, FreeRDP_RedirectHomeDrive, enable))
 				return COMMAND_LINE_ERROR;
 		}
+		CommandLineSwitchCase(arg, "ipv4")
+		{
+			if (strncmp(arg->Value, "force", 6) == 0)
+			{
+				if (!freerdp_settings_set_uint32(settings, FreeRDP_ForceIPvX, 4))
+					return COMMAND_LINE_ERROR;
+			}
+			else
+			{
+				if (!freerdp_settings_set_bool(settings, FreeRDP_PreferIPv6OverIPv4, FALSE))
+					return COMMAND_LINE_ERROR;
+			}
+		}
 		CommandLineSwitchCase(arg, "ipv6")
 		{
-			if (!freerdp_settings_set_bool(settings, FreeRDP_PreferIPv6OverIPv4, enable))
+			if (strncmp(arg->Value, "force", 6) == 0)
-				return COMMAND_LINE_ERROR;
+			{
+				if (!freerdp_settings_set_uint32(settings, FreeRDP_ForceIPvX, 6))
+					return COMMAND_LINE_ERROR;
+			}
+			else
+			{
+				if (!freerdp_settings_set_bool(settings, FreeRDP_PreferIPv6OverIPv4, TRUE))
+					return COMMAND_LINE_ERROR;
+			}
 		}
 		CommandLineSwitchCase(arg, "clipboard")
 		{

client/common/cmdline.h

@@ -247,7 +247,9 @@ static const COMMAND_LINE_ARGUMENT_A global_cmd_args[] = {
 	  "Print help" },
 	{ "home-drive", COMMAND_LINE_VALUE_BOOL, NULL, BoolValueFalse, NULL, -1, NULL,
 	  "Redirect user home as share" },
-	{ "ipv6", COMMAND_LINE_VALUE_FLAG, NULL, NULL, NULL, -1, "6",
+	{ "ipv4", COMMAND_LINE_VALUE_OPTIONAL, "[:force]", NULL, NULL, -1, "4",
+	  "Prefer IPv4 AAA record over IPv6 A record" },
+	{ "ipv6", COMMAND_LINE_VALUE_OPTIONAL, "[:force]", NULL, NULL, -1, "6",
 	  "Prefer IPv6 AAA record over IPv4 A record" },
 #if defined(WITH_JPEG)
 	{ "jpeg", COMMAND_LINE_VALUE_FLAG, NULL, NULL, NULL, -1, NULL, "JPEG codec support" },

include/freerdp/settings_types_private.h

@@ -746,7 +746,8 @@ struct rdp_settings
 	SETTINGS_DEPRECATED(ALIGN64 BOOL RedirectSerialPorts);   /* 4672 */
 	SETTINGS_DEPRECATED(ALIGN64 BOOL RedirectParallelPorts); /* 4673 */
 	SETTINGS_DEPRECATED(ALIGN64 BOOL PreferIPv6OverIPv4);    /* 4674 */
-	UINT64 padding4800[4800 - 4675];                         /* 4675 */
+	SETTINGS_DEPRECATED(ALIGN64 UINT32 ForceIPvX);           /* 4675 */
+	UINT64 padding4800[4800 - 4676];                         /* 4676 */
 
 	/**
 	 * Other Redirection

libfreerdp/common/settings_getters.c

@@ -1736,6 +1736,9 @@ UINT32 freerdp_settings_get_uint32(const rdpSettings* settings, FreeRDP_Settings
 		case FreeRDP_Floatbar:
 			return settings->Floatbar;
 
+		case FreeRDP_ForceIPvX:
+			return settings->ForceIPvX;
+
 		case FreeRDP_FrameAcknowledge:
 			return settings->FrameAcknowledge;
 
@@ -2169,6 +2172,10 @@ BOOL freerdp_settings_set_uint32(rdpSettings* settings, FreeRDP_Settings_Keys_UI
 			settings->Floatbar = cnv.c;
 			break;
 
+		case FreeRDP_ForceIPvX:
+			settings->ForceIPvX = cnv.c;
+			break;
+
 		case FreeRDP_FrameAcknowledge:
 			settings->FrameAcknowledge = cnv.c;
 			break;

libfreerdp/common/settings_str.h

@@ -334,6 +334,7 @@ static const struct settings_str_entry settings_map[] = {
 	{ FreeRDP_FakeMouseMotionInterval, FREERDP_SETTINGS_TYPE_UINT32,
 	  "FreeRDP_FakeMouseMotionInterval" },
 	{ FreeRDP_Floatbar, FREERDP_SETTINGS_TYPE_UINT32, "FreeRDP_Floatbar" },
+	{ FreeRDP_ForceIPvX, FREERDP_SETTINGS_TYPE_UINT32, "FreeRDP_ForceIPvX" },
 	{ FreeRDP_FrameAcknowledge, FREERDP_SETTINGS_TYPE_UINT32, "FreeRDP_FrameAcknowledge" },
 	{ FreeRDP_GatewayAcceptedCertLength, FREERDP_SETTINGS_TYPE_UINT32,
 	  "FreeRDP_GatewayAcceptedCertLength" },

libfreerdp/core/tcp.c

@@ -1176,21 +1176,46 @@ int freerdp_tcp_default_connect(rdpContext* context, rdpSettings* settings, cons
 			}
 			freerdp_set_last_error_log(context, 0);
 
+			/* By default we take the first returned entry.
+			 *
+			 * If PreferIPv6OverIPv4 = TRUE we force to IPv6 if there
+			 * is such an address available, but fall back to first if not found
+			 */
 			addr = result;
-
+			if (freerdp_settings_get_bool(settings, FreeRDP_PreferIPv6OverIPv4))
-			if ((addr->ai_family == AF_INET6) && (addr->ai_next != 0) &&
-			    !settings->PreferIPv6OverIPv4)
 			{
-				while ((addr = addr->ai_next))
+				while (addr && (addr->ai_family != AF_INET6))
-				{
+					addr = addr->ai_next;
-					if (addr->ai_family == AF_INET)
-						break;
-				}
-
 				if (!addr)
 					addr = result;
 			}
 
+			/* We want to force IPvX, abort if not detected */
+			const UINT32 IPvX = freerdp_settings_get_uint32(settings, FreeRDP_ForceIPvX);
+			switch (IPvX)
+			{
+				case 4:
+				case 6:
+				{
+					const int family = (IPvX == 4) ? AF_INET : AF_INET6;
+					while (addr && (addr->ai_family != family))
+						addr = addr->ai_next;
+					if (!addr)
+					{
+						freerdp_set_last_error_if_not(context, FREERDP_ERROR_DNS_NAME_NOT_FOUND);
+						return -1;
+					}
+				}
+				break;
+				default:
+					break;
+			}
+
+			if (!addr)
+			{
+				freerdp_set_last_error_if_not(context, FREERDP_ERROR_DNS_NAME_NOT_FOUND);
+				return -1;
+			}
 			sockfd = socket(addr->ai_family, addr->ai_socktype, addr->ai_protocol);
 
 			if (sockfd < 0)

libfreerdp/core/test/settings_property_lists.h

@@ -257,6 +257,7 @@ static const size_t uint32_list_indices[] = {
 	FreeRDP_ExtEncryptionMethods,
 	FreeRDP_FakeMouseMotionInterval,
 	FreeRDP_Floatbar,
+	FreeRDP_ForceIPvX,
 	FreeRDP_FrameAcknowledge,
 	FreeRDP_GatewayAcceptedCertLength,
 	FreeRDP_GatewayCredentialsSource,