Feature: add dhcp type dns client (#1509)

component/iface/iface.go

@@ -0,0 +1,113 @@
+package iface
+
+import (
+	"errors"
+	"net"
+	"time"
+
+	"github.com/Dreamacro/clash/common/singledo"
+)
+
+type Interface struct {
+	Index        int
+	Name         string
+	Addrs        []*net.IPNet
+	HardwareAddr net.HardwareAddr
+}
+
+var ErrIfaceNotFound = errors.New("interface not found")
+var ErrAddrNotFound = errors.New("addr not found")
+
+var interfaces = singledo.NewSingle(time.Second * 20)
+
+func ResolveInterface(name string) (*Interface, error) {
+	value, err, _ := interfaces.Do(func() (interface{}, error) {
+		ifaces, err := net.Interfaces()
+		if err != nil {
+			return nil, err
+		}
+
+		r := map[string]*Interface{}
+
+		for _, iface := range ifaces {
+			addrs, err := iface.Addrs()
+			if err != nil {
+				continue
+			}
+
+			ipNets := make([]*net.IPNet, 0, len(addrs))
+			for _, addr := range addrs {
+				ipNet := addr.(*net.IPNet)
+				if v4 := ipNet.IP.To4(); v4 != nil {
+					ipNet.IP = v4
+				}
+
+				ipNets = append(ipNets, ipNet)
+			}
+
+			r[iface.Name] = &Interface{
+				Index:        iface.Index,
+				Name:         iface.Name,
+				Addrs:        ipNets,
+				HardwareAddr: iface.HardwareAddr,
+			}
+		}
+
+		return r, nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	ifaces := value.(map[string]*Interface)
+	iface, ok := ifaces[name]
+	if !ok {
+		return nil, ErrIfaceNotFound
+	}
+
+	return iface, nil
+}
+
+func FlushCache() {
+	interfaces.Reset()
+}
+
+func (iface *Interface) PickIPv4Addr(destination net.IP) (*net.IPNet, error) {
+	return iface.pickIPAddr(destination, func(addr *net.IPNet) bool {
+		return addr.IP.To4() != nil
+	})
+}
+
+func (iface *Interface) PickIPv6Addr(destination net.IP) (*net.IPNet, error) {
+	return iface.pickIPAddr(destination, func(addr *net.IPNet) bool {
+		return addr.IP.To4() == nil
+	})
+}
+
+func (iface *Interface) pickIPAddr(destination net.IP, accept func(addr *net.IPNet) bool) (*net.IPNet, error) {
+	var fallback *net.IPNet
+
+	for _, addr := range iface.Addrs {
+		if !accept(addr) {
+			continue
+		}
+
+		if fallback == nil && !addr.IP.IsLinkLocalUnicast() {
+			fallback = addr
+
+			if destination == nil {
+				break
+			}
+		}
+
+		if destination != nil && addr.Contains(destination) {
+			return addr, nil
+		}
+	}
+
+	if fallback == nil {
+		return nil, ErrAddrNotFound
+	}
+
+	return fallback, nil
+}