Allow specifying hostname addresses in options.

main.go

@@ -130,12 +130,12 @@ func main() {
 	}
 
 	var err error
-	if Opts.ListenAddr, err = netip.ParseAddrPort(Opts.ListenAddrStr); err != nil {
+	if Opts.ListenAddr, err = ParseHostPort(Opts.ListenAddrStr); err != nil {
 		Opts.Logger.Error("listen address is malformed", "error", err)
 		os.Exit(1)
 	}
 
-	if Opts.TargetAddr4, err = netip.ParseAddrPort(Opts.TargetAddr4Str); err != nil {
+	if Opts.TargetAddr4, err = ParseHostPort(Opts.TargetAddr4Str); err != nil {
 		Opts.Logger.Error("ipv4 target address is malformed", "error", err)
 		os.Exit(1)
 	}
@@ -144,7 +144,7 @@ func main() {
 		os.Exit(1)
 	}
 
-	if Opts.TargetAddr6, err = netip.ParseAddrPort(Opts.TargetAddr6Str); err != nil {
+	if Opts.TargetAddr6, err = ParseHostPort(Opts.TargetAddr6Str); err != nil {
 		Opts.Logger.Error("ipv6 target address is malformed", "error", err)
 		os.Exit(1)
 	}

utils.go

@@ -7,6 +7,8 @@ package main
 import (
 	"fmt"
 	"net"
+	"net/netip"
+	"strconv"
 	"syscall"
 )
 
@@ -30,6 +32,29 @@ func CheckOriginAllowed(remoteIP net.IP) bool {
 	return false
 }
 
+func ParseHostPort(hostport string) (netip.AddrPort, error) {
+	host, portStr, err := net.SplitHostPort(hostport)
+	if err != nil {
+		return netip.AddrPort{}, fmt.Errorf("failed to parse host and port: %w", err)
+	}
+
+	ips, err := net.LookupIP(host)
+	if err != nil {
+		return netip.AddrPort{}, fmt.Errorf("failed to lookup IP addresses: %w", err)
+	}
+	if len(ips) == 0 {
+		return netip.AddrPort{}, fmt.Errorf("no IP addresses found")
+	}
+
+	port, err := strconv.ParseUint(portStr, 10, 16)
+	if err != nil {
+		return netip.AddrPort{}, fmt.Errorf("failed to parse port: %w", err)
+	}
+
+	ip, _ := netip.AddrFromSlice(ips[0])
+	return netip.AddrPortFrom(ip, uint16(port)), nil
+}
+
 func DialUpstreamControl(sport int) func(string, string, syscall.RawConn) error {
 	return func(network, address string, c syscall.RawConn) error {
 		var syscallErr error