统一 domainStrategy 行为. (#2720)

* 统一 `domainStrategy` 行为.

* Update proto

---------

Co-authored-by: rui0572 <125641819+rui0572@users.noreply.github.com>

transport/internet/config.go

@@ -12,6 +12,21 @@ var (
 	globalTransportSettings           []*TransportConfig
 )
 
+var strategy = [][]byte{
+	//              name        strategy,   prefer, fallback
+	{0, 0, 0}, //   AsIs        none,       /,      /
+	{1, 0, 0}, //   UseIP       use,        both,   none
+	{1, 4, 0}, //   UseIPv4     use,        4,      none
+	{1, 6, 0}, //   UseIPv6     use,        6,      none
+	{1, 4, 6}, //   UseIPv4v6   use,        4,      6
+	{1, 6, 4}, //   UseIPv6v4   use,        6,      4
+	{2, 0, 0}, //   ForceIP     force,      both,   none
+	{2, 4, 0}, //   ForceIPv4   force,      4,      none
+	{2, 6, 0}, //   ForceIPv6   force,      6,      none
+	{2, 4, 6}, //   ForceIPv4v6 force,      4,      6
+	{2, 6, 4}, //   ForceIPv6v4 force,      6,      4
+}
+
 const unknownProtocol = "unknown"
 
 func transportProtocolToString(protocol TransportProtocol) string {
@@ -122,3 +137,31 @@ func (c *ProxyConfig) HasTag() bool {
 func (m SocketConfig_TProxyMode) IsEnabled() bool {
 	return m != SocketConfig_Off
 }
+
+func (s DomainStrategy) hasStrategy() bool {
+	return strategy[s][0] != 0
+}
+
+func (s DomainStrategy) forceIP() bool {
+	return strategy[s][0] == 2
+}
+
+func (s DomainStrategy) preferIP4() bool {
+	return strategy[s][1] == 4 || strategy[s][1] == 0
+}
+
+func (s DomainStrategy) preferIP6() bool {
+	return strategy[s][1] == 6 || strategy[s][1] == 0
+}
+
+func (s DomainStrategy) hasFallback() bool {
+	return strategy[s][2] != 0
+}
+
+func (s DomainStrategy) fallbackIP4() bool {
+	return strategy[s][2] == 4
+}
+
+func (s DomainStrategy) fallbackIP6() bool {
+	return strategy[s][2] == 6
+}