feat(netxlite): implements NS queries (#734)

This diff has been extracted from https://github.com/bassosimone/websteps-illustrated/commit/eb0bf38957e79fbad198fcdc9f9c7b36f61a8e2c.

See https://github.com/ooni/probe/issues/2096.

While there, skip the broken tests caused by issue
https://github.com/ooni/probe/issues/2098.

internal/model/mocks/dnsdecoder.go

@@ -1,6 +1,8 @@
 package mocks
 
 import (
+	"net"
+
 	"github.com/miekg/dns"
 	"github.com/ooni/probe-cli/v3/internal/model"
 )
@@ -8,10 +10,9 @@ import (
 // DNSDecoder allows mocking dnsx.DNSDecoder.
 type DNSDecoder struct {
 	MockDecodeLookupHost func(qtype uint16, reply []byte, queryID uint16) ([]string, error)
-
-	MockDecodeHTTPS func(reply []byte, queryID uint16) (*model.HTTPSSvc, error)
-
-	MockDecodeReply func(reply []byte) (*dns.Msg, error)
+	MockDecodeHTTPS      func(reply []byte, queryID uint16) (*model.HTTPSSvc, error)
+	MockDecodeNS         func(reply []byte, queryID uint16) ([]*net.NS, error)
+	MockDecodeReply      func(reply []byte) (*dns.Msg, error)
 }
 
 // DecodeLookupHost calls MockDecodeLookupHost.
@@ -24,6 +25,11 @@ func (e *DNSDecoder) DecodeHTTPS(reply []byte, queryID uint16) (*model.HTTPSSvc,
 	return e.MockDecodeHTTPS(reply, queryID)
 }
 
+// DecodeNS calls MockDecodeNS.
+func (e *DNSDecoder) DecodeNS(reply []byte, queryID uint16) ([]*net.NS, error) {
+	return e.MockDecodeNS(reply, queryID)
+}
+
 // DecodeReply calls MockDecodeReply.
 func (e *DNSDecoder) DecodeReply(reply []byte) (*dns.Msg, error) {
 	return e.MockDecodeReply(reply)

internal/model/mocks/dnsdecoder_test.go

@@ -2,6 +2,7 @@ package mocks
 
 import (
 	"errors"
+	"net"
 	"testing"
 
 	"github.com/miekg/dns"
@@ -41,6 +42,22 @@ func TestDNSDecoder(t *testing.T) {
 		}
 	})
 
+	t.Run("DecodeNS", func(t *testing.T) {
+		expected := errors.New("mocked error")
+		e := &DNSDecoder{
+			MockDecodeNS: func(reply []byte, queryID uint16) ([]*net.NS, error) {
+				return nil, expected
+			},
+		}
+		out, err := e.DecodeNS(make([]byte, 17), dns.Id())
+		if !errors.Is(err, expected) {
+			t.Fatal("unexpected err", err)
+		}
+		if out != nil {
+			t.Fatal("unexpected out")
+		}
+	})
+
 	t.Run("DecodeReply", func(t *testing.T) {
 		expected := errors.New("mocked error")
 		e := &DNSDecoder{

internal/model/mocks/resolver.go

@@ -2,6 +2,7 @@ package mocks
 
 import (
 	"context"
+	"net"
 
 	"github.com/ooni/probe-cli/v3/internal/model"
 )
@@ -13,6 +14,7 @@ type Resolver struct {
 	MockAddress              func() string
 	MockCloseIdleConnections func()
 	MockLookupHTTPS          func(ctx context.Context, domain string) (*model.HTTPSSvc, error)
+	MockLookupNS             func(ctx context.Context, domain string) ([]*net.NS, error)
 }
 
 // LookupHost calls MockLookupHost.
@@ -39,3 +41,8 @@ func (r *Resolver) CloseIdleConnections() {
 func (r *Resolver) LookupHTTPS(ctx context.Context, domain string) (*model.HTTPSSvc, error) {
 	return r.MockLookupHTTPS(ctx, domain)
 }
+
+// LookupNS calls MockLookupNS.
+func (r *Resolver) LookupNS(ctx context.Context, domain string) ([]*net.NS, error) {
+	return r.MockLookupNS(ctx, domain)
+}

internal/model/mocks/resolver_test.go

@@ -3,6 +3,7 @@ package mocks
 import (
 	"context"
 	"errors"
+	"net"
 	"testing"
 
 	"github.com/ooni/probe-cli/v3/internal/model"
@@ -77,4 +78,21 @@ func TestResolver(t *testing.T) {
 			t.Fatal("expected nil addr")
 		}
 	})
+
+	t.Run("LookupNS", func(t *testing.T) {
+		expected := errors.New("mocked error")
+		r := &Resolver{
+			MockLookupNS: func(ctx context.Context, domain string) ([]*net.NS, error) {
+				return nil, expected
+			},
+		}
+		ctx := context.Background()
+		ns, err := r.LookupNS(ctx, "dns.google")
+		if !errors.Is(err, expected) {
+			t.Fatal("unexpected error", err)
+		}
+		if ns != nil {
+			t.Fatal("expected nil addr")
+		}
+	})
 }

internal/model/netx.go

@@ -51,6 +51,9 @@ type DNSDecoder interface {
 	// an error, though, when there are no IPv4/IPv6 hints in the reply.
 	DecodeHTTPS(data []byte, queryID uint16) (*HTTPSSvc, error)
 
+	// DecodeNS is like DecodeHTTPS but for NS queries.
+	DecodeNS(data []byte, queryID uint16) ([]*net.NS, error)
+
 	// DecodeReply decodes a DNS reply message.
 	//
 	// Arguments:
@@ -194,6 +197,9 @@ type Resolver interface {
 	// LookupHTTPS issues an HTTPS query for a domain.
 	LookupHTTPS(
 		ctx context.Context, domain string) (*HTTPSSvc, error)
+
+	// LookupNS issues a NS query for a domain.
+	LookupNS(ctx context.Context, domain string) ([]*net.NS, error)
 }
 
 // TLSDialer is a Dialer dialing TLS connections.