Add resolved service and DNS server

option/resolved.go

@@ -0,0 +1,49 @@
+package option
+
+import (
+	"context"
+	"net/netip"
+
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/json"
+	"github.com/sagernet/sing/common/json/badoption"
+)
+
+type _ResolvedServiceOptions struct {
+	ListenOptions
+}
+
+type ResolvedServiceOptions _ResolvedServiceOptions
+
+func (r ResolvedServiceOptions) MarshalJSONContext(ctx context.Context) ([]byte, error) {
+	if r.Listen != nil && netip.Addr(*r.Listen) == (netip.AddrFrom4([4]byte{127, 0, 0, 53})) {
+		r.Listen = nil
+	}
+	if r.ListenPort == 53 {
+		r.ListenPort = 0
+	}
+	return json.MarshalContext(ctx, (*_ResolvedServiceOptions)(&r))
+}
+
+func (r *ResolvedServiceOptions) UnmarshalJSONContext(ctx context.Context, bytes []byte) error {
+	err := json.UnmarshalContextDisallowUnknownFields(ctx, bytes, (*_ResolvedServiceOptions)(r))
+	if err != nil {
+		return err
+	}
+	if r.Listen == nil {
+		r.Listen = (*badoption.Addr)(common.Ptr(netip.AddrFrom4([4]byte{127, 0, 0, 53})))
+	}
+	if r.ListenPort == 0 {
+		r.ListenPort = 53
+	}
+	return nil
+}
+
+type ResolvedDNSServerOptions struct {
+	Service                string `json:"service"`
+	AcceptDefaultResolvers bool   `json:"accept_default_resolvers,omitempty"`
+	// NDots                  int                `json:"ndots,omitempty"`
+	// Timeout                badoption.Duration `json:"timeout,omitempty"`
+	// Attempts               int                `json:"attempts,omitempty"`
+	// Rotate                 bool               `json:"rotate,omitempty"`
+}