Chore: split enhanced mode instance (#936)

Co-authored-by: Dreamacro <305009791@qq.com>

component/fakeip/pool.go

@@ -89,6 +89,11 @@ func (p *Pool) Gateway() net.IP {
 	return uintToIP(p.gateway)
 }
 
+// PatchFrom clone cache from old pool
+func (p *Pool) PatchFrom(o *Pool) {
+	o.cache.CloneTo(p.cache)
+}
+
 func (p *Pool) get(host string) net.IP {
 	current := p.offset
 	for {

component/resolver/enhancer.go

@@ -0,0 +1,46 @@
+package resolver
+
+import (
+	"net"
+)
+
+var DefaultHostMapper Enhancer
+
+type Enhancer interface {
+	FakeIPEnabled() bool
+	MappingEnabled() bool
+	IsFakeIP(net.IP) bool
+	FindHostByIP(net.IP) (string, bool)
+}
+
+func FakeIPEnabled() bool {
+	if mapper := DefaultHostMapper; mapper != nil {
+		return mapper.FakeIPEnabled()
+	}
+
+	return false
+}
+
+func MappingEnabled() bool {
+	if mapper := DefaultHostMapper; mapper != nil {
+		return mapper.MappingEnabled()
+	}
+
+	return false
+}
+
+func IsFakeIP(ip net.IP) bool {
+	if mapper := DefaultHostMapper; mapper != nil {
+		return mapper.IsFakeIP(ip)
+	}
+
+	return false
+}
+
+func FindHostByIP(ip net.IP) (string, bool) {
+	if mapper := DefaultHostMapper; mapper != nil {
+		return mapper.FindHostByIP(ip)
+	}
+
+	return "", false
+}