feat: add ip-version param

adapter/outbound/util.go

@@ -5,6 +5,7 @@ import (
 	"crypto/tls"
 	xtls "github.com/xtls/go"
 	"net"
+	"net/netip"
 	"strconv"
 	"sync"
 	"time"
@@ -74,6 +75,59 @@ func resolveUDPAddr(network, address string) (*net.UDPAddr, error) {
 	return net.ResolveUDPAddr(network, net.JoinHostPort(ip.String(), port))
 }
 
+func resolveUDPAddrWithPrefer(network, address string, prefer C.DNSPrefer) (*net.UDPAddr, error) {
+	host, port, err := net.SplitHostPort(address)
+	if err != nil {
+		return nil, err
+	}
+	var ip netip.Addr
+	switch prefer {
+	case C.IPv4Only:
+		ip, err = resolver.ResolveIPv4ProxyServerHost(host)
+	case C.IPv6Only:
+		ip, err = resolver.ResolveIPv6ProxyServerHost(host)
+	case C.IPv6Prefer:
+		var ips []netip.Addr
+		ips, err = resolver.ResolveAllIPProxyServerHost(host)
+		var fallback netip.Addr
+		if err == nil {
+			for _, addr := range ips {
+				if addr.Is6() {
+					ip = addr
+					break
+				} else {
+					if !fallback.IsValid() {
+						fallback = addr
+					}
+				}
+			}
+			ip = fallback
+		}
+	case C.IPv4Prefer | C.DualStack:
+		var ips []netip.Addr
+		ips, err = resolver.ResolveAllIPProxyServerHost(host)
+		var fallback netip.Addr
+		if err == nil {
+			for _, addr := range ips {
+				if addr.Is4() {
+					ip = addr
+					break
+				} else {
+					if !fallback.IsValid() {
+						fallback = addr
+					}
+				}
+			}
+			ip = fallback
+		}
+	}
+
+	if err != nil {
+		return nil, err
+	}
+	return net.ResolveUDPAddr(network, net.JoinHostPort(ip.String(), port))
+}
+
 func safeConnClose(c net.Conn, err error) {
 	if err != nil {
 		_ = c.Close()