Add resolver for outbound dialer

dns/dialer.go

@@ -0,0 +1,68 @@
+package dns
+
+import (
+	"context"
+	"net"
+
+	E "github.com/sagernet/sing/common/exceptions"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+
+	"github.com/sagernet/sing-box/adapter"
+	C "github.com/sagernet/sing-box/constant"
+)
+
+type DialerWrapper struct {
+	dialer    N.Dialer
+	strategy  C.DomainStrategy
+	client    adapter.DNSClient
+	transport adapter.DNSTransport
+}
+
+func NewDialerWrapper(dialer N.Dialer, strategy C.DomainStrategy, client adapter.DNSClient, transport adapter.DNSTransport) N.Dialer {
+	return &DialerWrapper{dialer, strategy, client, transport}
+}
+
+func (d *DialerWrapper) DialContext(ctx context.Context, network string, destination M.Socksaddr) (net.Conn, error) {
+	if destination.IsIP() {
+		return d.dialer.DialContext(ctx, network, destination)
+	}
+	addresses, err := d.client.Lookup(ctx, d.transport, destination.Fqdn, d.strategy)
+	if err != nil {
+		return nil, err
+	}
+	var conn net.Conn
+	var connErrors []error
+	for _, address := range addresses {
+		conn, err = d.dialer.DialContext(ctx, network, M.SocksaddrFromAddrPort(address, destination.Port))
+		if err != nil {
+			connErrors = append(connErrors, err)
+		}
+		return conn, nil
+	}
+	return nil, E.Errors(connErrors...)
+}
+
+func (d *DialerWrapper) ListenPacket(ctx context.Context, destination M.Socksaddr) (net.PacketConn, error) {
+	if destination.IsIP() {
+		return d.dialer.ListenPacket(ctx, destination)
+	}
+	addresses, err := d.client.Lookup(ctx, d.transport, destination.Fqdn, d.strategy)
+	if err != nil {
+		return nil, err
+	}
+	var conn net.PacketConn
+	var connErrors []error
+	for _, address := range addresses {
+		conn, err = d.dialer.ListenPacket(ctx, M.SocksaddrFromAddrPort(address, destination.Port))
+		if err != nil {
+			connErrors = append(connErrors, err)
+		}
+		return conn, nil
+	}
+	return nil, E.Errors(connErrors...)
+}
+
+func (d *DialerWrapper) Upstream() any {
+	return d.dialer
+}