Feature: add default-nameserver and outbound interface

component/resolver/resolver.go

@@ -0,0 +1,119 @@
+package resolver
+
+import (
+	"errors"
+	"net"
+	"strings"
+
+	trie "github.com/Dreamacro/clash/component/domain-trie"
+)
+
+var (
+	// DefaultResolver aim to resolve ip
+	DefaultResolver Resolver
+
+	// DefaultHosts aim to resolve hosts
+	DefaultHosts = trie.New()
+)
+
+var (
+	ErrIPNotFound = errors.New("couldn't find ip")
+	ErrIPVersion  = errors.New("ip version error")
+)
+
+type Resolver interface {
+	ResolveIP(host string) (ip net.IP, err error)
+	ResolveIPv4(host string) (ip net.IP, err error)
+	ResolveIPv6(host string) (ip net.IP, err error)
+}
+
+// ResolveIPv4 with a host, return ipv4
+func ResolveIPv4(host string) (net.IP, error) {
+	if node := DefaultHosts.Search(host); node != nil {
+		if ip := node.Data.(net.IP).To4(); ip != nil {
+			return ip, nil
+		}
+	}
+
+	ip := net.ParseIP(host)
+	if ip != nil {
+		if !strings.Contains(host, ":") {
+			return ip, nil
+		}
+		return nil, ErrIPVersion
+	}
+
+	if DefaultResolver != nil {
+		return DefaultResolver.ResolveIPv4(host)
+	}
+
+	ipAddrs, err := net.LookupIP(host)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, ip := range ipAddrs {
+		if ip4 := ip.To4(); ip4 != nil {
+			return ip4, nil
+		}
+	}
+
+	return nil, ErrIPNotFound
+}
+
+// ResolveIPv6 with a host, return ipv6
+func ResolveIPv6(host string) (net.IP, error) {
+	if node := DefaultHosts.Search(host); node != nil {
+		if ip := node.Data.(net.IP).To16(); ip != nil {
+			return ip, nil
+		}
+	}
+
+	ip := net.ParseIP(host)
+	if ip != nil {
+		if strings.Contains(host, ":") {
+			return ip, nil
+		}
+		return nil, ErrIPVersion
+	}
+
+	if DefaultResolver != nil {
+		return DefaultResolver.ResolveIPv6(host)
+	}
+
+	ipAddrs, err := net.LookupIP(host)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, ip := range ipAddrs {
+		if ip.To4() == nil {
+			return ip, nil
+		}
+	}
+
+	return nil, ErrIPNotFound
+}
+
+// ResolveIP with a host, return ip
+func ResolveIP(host string) (net.IP, error) {
+	if node := DefaultHosts.Search(host); node != nil {
+		return node.Data.(net.IP), nil
+	}
+
+	if DefaultResolver != nil {
+		return DefaultResolver.ResolveIP(host)
+	}
+
+	ip := net.ParseIP(host)
+	if ip != nil {
+		return ip, nil
+	}
+
+	ipAddr, err := net.ResolveIPAddr("ip", host)
+	if err != nil {
+		return nil, err
+	}
+
+	return ipAddr.IP, nil
+}