feat: add a simple dnsping experiment (#674)

See https://github.com/ooni/probe/issues/1987 (issue).

See https://github.com/ooni/spec/pull/238 (impl).

While there, fix the build for go1.18 by adding go1.18 specific tests. I was
increasingly bothered by the build being red.

internal/archival/quic_test.go

@@ -1,3 +1,5 @@
+//go:build !go1.18
+
 package archival
 
 import (

internal/archival/quic_test_go118.go

@@ -0,0 +1,465 @@
+//go:build go1.18
+
+package archival
+
+import (
+	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"errors"
+	"io"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/lucas-clemente/quic-go"
+	"github.com/marten-seemann/qtls-go1-18" // it's annoying to depend on that
+	"github.com/ooni/probe-cli/v3/internal/fakefill"
+	"github.com/ooni/probe-cli/v3/internal/model"
+	"github.com/ooni/probe-cli/v3/internal/model/mocks"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
+)
+
+func TestSaverWriteTo(t *testing.T) {
+	// newAddr creates an new net.Addr for testing.
+	newAddr := func(endpoint string) net.Addr {
+		return &mocks.Addr{
+			MockString: func() string {
+				return endpoint
+			},
+			MockNetwork: func() string {
+				return "udp"
+			},
+		}
+	}
+
+	// newConn is a helper function for creating a new connection.
+	newConn := func(numBytes int, err error) model.UDPLikeConn {
+		return &mocks.UDPLikeConn{
+			MockWriteTo: func(p []byte, addr net.Addr) (int, error) {
+				time.Sleep(time.Microsecond)
+				return numBytes, err
+			},
+		}
+	}
+
+	t.Run("on success", func(t *testing.T) {
+		const mockedEndpoint = "8.8.4.4:443"
+		const mockedNumBytes = 128
+		addr := newAddr(mockedEndpoint)
+		conn := newConn(mockedNumBytes, nil)
+		saver := NewSaver()
+		v := &SingleNetworkEventValidator{
+			ExpectedCount:   mockedNumBytes,
+			ExpectedErr:     nil,
+			ExpectedNetwork: "udp",
+			ExpectedOp:      netxlite.WriteToOperation,
+			ExpectedEpnt:    mockedEndpoint,
+			Saver:           saver,
+		}
+		buf := make([]byte, 1024)
+		count, err := saver.WriteTo(conn, buf, addr)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if count != mockedNumBytes {
+			t.Fatal("invalid count")
+		}
+		if err := v.Validate(); err != nil {
+			t.Fatal(err)
+		}
+	})
+
+	t.Run("on failure", func(t *testing.T) {
+		const mockedEndpoint = "8.8.4.4:443"
+		mockedError := netxlite.NewTopLevelGenericErrWrapper(io.EOF)
+		addr := newAddr(mockedEndpoint)
+		conn := newConn(0, mockedError)
+		saver := NewSaver()
+		v := &SingleNetworkEventValidator{
+			ExpectedCount:   0,
+			ExpectedErr:     mockedError,
+			ExpectedNetwork: "udp",
+			ExpectedOp:      netxlite.WriteToOperation,
+			ExpectedEpnt:    mockedEndpoint,
+			Saver:           saver,
+		}
+		buf := make([]byte, 1024)
+		count, err := saver.WriteTo(conn, buf, addr)
+		if !errors.Is(err, mockedError) {
+			t.Fatal("unexpected err", err)
+		}
+		if count != 0 {
+			t.Fatal("invalid count")
+		}
+		if err := v.Validate(); err != nil {
+			t.Fatal(err)
+		}
+	})
+}
+
+func TestSaverReadFrom(t *testing.T) {
+	// newAddr creates an new net.Addr for testing.
+	newAddr := func(endpoint string) net.Addr {
+		return &mocks.Addr{
+			MockString: func() string {
+				return endpoint
+			},
+			MockNetwork: func() string {
+				return "udp"
+			},
+		}
+	}
+
+	// newConn is a helper function for creating a new connection.
+	newConn := func(numBytes int, addr net.Addr, err error) model.UDPLikeConn {
+		return &mocks.UDPLikeConn{
+			MockReadFrom: func(p []byte) (int, net.Addr, error) {
+				time.Sleep(time.Microsecond)
+				return numBytes, addr, err
+			},
+		}
+	}
+
+	t.Run("on success", func(t *testing.T) {
+		const mockedEndpoint = "8.8.4.4:443"
+		const mockedNumBytes = 128
+		expectedAddr := newAddr(mockedEndpoint)
+		conn := newConn(mockedNumBytes, expectedAddr, nil)
+		saver := NewSaver()
+		v := &SingleNetworkEventValidator{
+			ExpectedCount:   mockedNumBytes,
+			ExpectedErr:     nil,
+			ExpectedNetwork: "udp",
+			ExpectedOp:      netxlite.ReadFromOperation,
+			ExpectedEpnt:    mockedEndpoint,
+			Saver:           saver,
+		}
+		buf := make([]byte, 1024)
+		count, addr, err := saver.ReadFrom(conn, buf)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if expectedAddr.Network() != addr.Network() {
+			t.Fatal("invalid addr.Network")
+		}
+		if expectedAddr.String() != addr.String() {
+			t.Fatal("invalid addr.String")
+		}
+		if count != mockedNumBytes {
+			t.Fatal("invalid count")
+		}
+		if err := v.Validate(); err != nil {
+			t.Fatal(err)
+		}
+	})
+
+	t.Run("on failure", func(t *testing.T) {
+		mockedError := netxlite.NewTopLevelGenericErrWrapper(io.EOF)
+		conn := newConn(0, nil, mockedError)
+		saver := NewSaver()
+		v := &SingleNetworkEventValidator{
+			ExpectedCount:   0,
+			ExpectedErr:     mockedError,
+			ExpectedNetwork: "udp",
+			ExpectedOp:      netxlite.ReadFromOperation,
+			ExpectedEpnt:    "",
+			Saver:           saver,
+		}
+		buf := make([]byte, 1024)
+		count, addr, err := saver.ReadFrom(conn, buf)
+		if !errors.Is(err, mockedError) {
+			t.Fatal(err)
+		}
+		if addr != nil {
+			t.Fatal("invalid addr")
+		}
+		if count != 0 {
+			t.Fatal("invalid count")
+		}
+		if err := v.Validate(); err != nil {
+			t.Fatal(err)
+		}
+	})
+}
+
+func TestSaverQUICDialContext(t *testing.T) {
+	// newQUICDialer creates a new QUICDialer for testing.
+	newQUICDialer := func(qconn quic.EarlyConnection, err error) model.QUICDialer {
+		return &mocks.QUICDialer{
+			MockDialContext: func(
+				ctx context.Context, network, address string, tlsConfig *tls.Config,
+				quicConfig *quic.Config) (quic.EarlyConnection, error) {
+				time.Sleep(time.Microsecond)
+				return qconn, err
+			},
+		}
+	}
+
+	// newQUICConnection creates a new quic.EarlyConnection for testing.
+	newQUICConnection := func(handshakeComplete context.Context, state tls.ConnectionState) quic.EarlyConnection {
+		return &mocks.QUICEarlyConnection{
+			MockHandshakeComplete: func() context.Context {
+				return handshakeComplete
+			},
+			MockConnectionState: func() quic.ConnectionState {
+				return quic.ConnectionState{
+					TLS: qtls.ConnectionStateWith0RTT{
+						ConnectionState: state,
+					},
+				}
+			},
+			MockCloseWithError: func(code quic.ApplicationErrorCode, reason string) error {
+				return nil
+			},
+		}
+	}
+
+	t.Run("on success", func(t *testing.T) {
+		handshakeCtx := context.Background()
+		handshakeCtx, handshakeCancel := context.WithCancel(handshakeCtx)
+		handshakeCancel() // simulate a completed handshake
+		const expectedNetwork = "udp"
+		const mockedEndpoint = "8.8.4.4:443"
+		saver := NewSaver()
+		var peerCerts [][]byte
+		ff := &fakefill.Filler{}
+		ff.Fill(&peerCerts)
+		if len(peerCerts) < 1 {
+			t.Fatal("did not fill peerCerts")
+		}
+		v := &SingleQUICTLSHandshakeValidator{
+			ExpectedALPN:       []string{"h3"},
+			ExpectedSNI:        "dns.google",
+			ExpectedSkipVerify: true,
+			//
+			ExpectedCipherSuite:        tls.TLS_AES_128_GCM_SHA256,
+			ExpectedNegotiatedProtocol: "h3",
+			ExpectedPeerCerts:          peerCerts,
+			ExpectedVersion:            tls.VersionTLS13,
+			//
+			ExpectedNetwork:    "quic",
+			ExpectedRemoteAddr: mockedEndpoint,
+			//
+			QUICConfig: &quic.Config{},
+			//
+			ExpectedFailure: nil,
+			Saver:           saver,
+		}
+		qconn := newQUICConnection(handshakeCtx, v.NewTLSConnectionState())
+		dialer := newQUICDialer(qconn, nil)
+		ctx := context.Background()
+		qconn, err := saver.QUICDialContext(ctx, dialer, expectedNetwork,
+			mockedEndpoint, v.NewTLSConfig(), v.QUICConfig)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if qconn == nil {
+			t.Fatal("expected nil qconn")
+		}
+		qconn.CloseWithError(0, "")
+		if err := v.Validate(); err != nil {
+			t.Fatal(err)
+		}
+	})
+
+	t.Run("on handshake timeout", func(t *testing.T) {
+		handshakeCtx := context.Background()
+		handshakeCtx, handshakeCancel := context.WithCancel(handshakeCtx)
+		defer handshakeCancel()
+		const expectedNetwork = "udp"
+		const mockedEndpoint = "8.8.4.4:443"
+		saver := NewSaver()
+		v := &SingleQUICTLSHandshakeValidator{
+			ExpectedALPN:       []string{"h3"},
+			ExpectedSNI:        "dns.google",
+			ExpectedSkipVerify: true,
+			//
+			ExpectedCipherSuite:        0,
+			ExpectedNegotiatedProtocol: "",
+			ExpectedPeerCerts:          nil,
+			ExpectedVersion:            0,
+			//
+			ExpectedNetwork:    "quic",
+			ExpectedRemoteAddr: mockedEndpoint,
+			//
+			QUICConfig: &quic.Config{},
+			//
+			ExpectedFailure: context.DeadlineExceeded,
+			Saver:           saver,
+		}
+		qconn := newQUICConnection(handshakeCtx, tls.ConnectionState{})
+		dialer := newQUICDialer(qconn, nil)
+		ctx := context.Background()
+		ctx, cancel := context.WithTimeout(ctx, time.Microsecond)
+		defer cancel()
+		qconn, err := saver.QUICDialContext(ctx, dialer, expectedNetwork,
+			mockedEndpoint, v.NewTLSConfig(), v.QUICConfig)
+		if !errors.Is(err, context.DeadlineExceeded) {
+			t.Fatal("unexpected error")
+		}
+		if qconn != nil {
+			t.Fatal("expected nil connection")
+		}
+		if err := v.Validate(); err != nil {
+			t.Fatal(err)
+		}
+	})
+
+	t.Run("on other error", func(t *testing.T) {
+		mockedError := netxlite.NewTopLevelGenericErrWrapper(io.EOF)
+		const expectedNetwork = "udp"
+		const mockedEndpoint = "8.8.4.4:443"
+		saver := NewSaver()
+		v := &SingleQUICTLSHandshakeValidator{
+			ExpectedALPN:       []string{"h3"},
+			ExpectedSNI:        "dns.google",
+			ExpectedSkipVerify: true,
+			//
+			ExpectedCipherSuite:        0,
+			ExpectedNegotiatedProtocol: "",
+			ExpectedPeerCerts:          nil,
+			ExpectedVersion:            0,
+			//
+			ExpectedNetwork:    "quic",
+			ExpectedRemoteAddr: mockedEndpoint,
+			//
+			QUICConfig: &quic.Config{},
+			//
+			ExpectedFailure: mockedError,
+			Saver:           saver,
+		}
+		dialer := newQUICDialer(nil, mockedError)
+		ctx := context.Background()
+		qconn, err := saver.QUICDialContext(ctx, dialer, expectedNetwork,
+			mockedEndpoint, v.NewTLSConfig(), v.QUICConfig)
+		if !errors.Is(err, mockedError) {
+			t.Fatal("unexpected error")
+		}
+		if qconn != nil {
+			t.Fatal("expected nil connection")
+		}
+		if err := v.Validate(); err != nil {
+			t.Fatal(err)
+		}
+	})
+
+	// TODO(bassosimone): here we're not testing the case in which
+	// the certificate is invalid for the required SNI.
+	//
+	// We need first to figure out whether this is what happens
+	// when we validate for QUIC in such cases. If that's the case
+	// indeed, then we can write the tests.
+
+	t.Run("on x509.HostnameError", func(t *testing.T) {
+		t.Skip("test not implemented")
+	})
+
+	t.Run("on x509.UnknownAuthorityError", func(t *testing.T) {
+		t.Skip("test not implemented")
+	})
+
+	t.Run("on x509.CertificateInvalidError", func(t *testing.T) {
+		t.Skip("test not implemented")
+	})
+}
+
+type SingleQUICTLSHandshakeValidator struct {
+	// related to the tls.Config
+	ExpectedALPN       []string
+	ExpectedSNI        string
+	ExpectedSkipVerify bool
+
+	// related to the tls.ConnectionState
+	ExpectedCipherSuite        uint16
+	ExpectedNegotiatedProtocol string
+	ExpectedPeerCerts          [][]byte
+	ExpectedVersion            uint16
+
+	// related to the mocked conn (TLS) / dial params (QUIC)
+	ExpectedNetwork    string
+	ExpectedRemoteAddr string
+
+	// tells us whether we're using QUIC
+	QUICConfig *quic.Config
+
+	// other fields
+	ExpectedFailure error
+	Saver           *Saver
+}
+
+func (v *SingleQUICTLSHandshakeValidator) NewTLSConfig() *tls.Config {
+	return &tls.Config{
+		NextProtos:         v.ExpectedALPN,
+		ServerName:         v.ExpectedSNI,
+		InsecureSkipVerify: v.ExpectedSkipVerify,
+	}
+}
+
+func (v *SingleQUICTLSHandshakeValidator) NewTLSConnectionState() tls.ConnectionState {
+	var state tls.ConnectionState
+	if v.ExpectedCipherSuite != 0 {
+		state.CipherSuite = v.ExpectedCipherSuite
+	}
+	if v.ExpectedNegotiatedProtocol != "" {
+		state.NegotiatedProtocol = v.ExpectedNegotiatedProtocol
+	}
+	for _, cert := range v.ExpectedPeerCerts {
+		state.PeerCertificates = append(state.PeerCertificates, &x509.Certificate{
+			Raw: cert,
+		})
+	}
+	if v.ExpectedVersion != 0 {
+		state.Version = v.ExpectedVersion
+	}
+	return state
+}
+
+func (v *SingleQUICTLSHandshakeValidator) Validate() error {
+	trace := v.Saver.MoveOutTrace()
+	var entries []*QUICTLSHandshakeEvent
+	if v.QUICConfig != nil {
+		entries = trace.QUICHandshake
+	} else {
+		entries = trace.TLSHandshake
+	}
+	if len(entries) != 1 {
+		return errors.New("expected to see a single entry")
+	}
+	entry := entries[0]
+	if diff := cmp.Diff(entry.ALPN, v.ExpectedALPN); diff != "" {
+		return errors.New(diff)
+	}
+	if entry.CipherSuite != netxlite.TLSCipherSuiteString(v.ExpectedCipherSuite) {
+		return errors.New("unexpected .CipherSuite")
+	}
+	if !errors.Is(entry.Failure, v.ExpectedFailure) {
+		return errors.New("unexpected .Failure")
+	}
+	if !entry.Finished.After(entry.Started) {
+		return errors.New(".Finished is not after .Started")
+	}
+	if entry.NegotiatedProto != v.ExpectedNegotiatedProtocol {
+		return errors.New("unexpected .NegotiatedProto")
+	}
+	if entry.Network != v.ExpectedNetwork {
+		return errors.New("unexpected .Network")
+	}
+	if diff := cmp.Diff(entry.PeerCerts, v.ExpectedPeerCerts); diff != "" {
+		return errors.New("unexpected .PeerCerts")
+	}
+	if entry.RemoteAddr != v.ExpectedRemoteAddr {
+		return errors.New("unexpected .RemoteAddr")
+	}
+	if entry.SNI != v.ExpectedSNI {
+		return errors.New("unexpected .ServerName")
+	}
+	if entry.SkipVerify != v.ExpectedSkipVerify {
+		return errors.New("unexpected .SkipVerify")
+	}
+	if entry.TLSVersion != netxlite.TLSVersionString(v.ExpectedVersion) {
+		return errors.New("unexpected .Version")
+	}
+	return nil
+}

internal/engine/allexperiments.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/ooni/probe-cli/v3/internal/engine/experiment/dash"
 	"github.com/ooni/probe-cli/v3/internal/engine/experiment/dnscheck"
+	"github.com/ooni/probe-cli/v3/internal/engine/experiment/dnsping"
 	"github.com/ooni/probe-cli/v3/internal/engine/experiment/example"
 	"github.com/ooni/probe-cli/v3/internal/engine/experiment/fbmessenger"
 	"github.com/ooni/probe-cli/v3/internal/engine/experiment/hhfm"
@@ -57,6 +58,18 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 		}
 	},
 
+	"dnsping": func(session *Session) *ExperimentBuilder {
+		return &ExperimentBuilder{
+			build: func(config interface{}) *Experiment {
+				return NewExperiment(session, dnsping.NewExperimentMeasurer(
+					*config.(*dnsping.Config),
+				))
+			},
+			config:      &dnsping.Config{},
+			inputPolicy: InputOrStaticDefault,
+		}
+	},
+
 	"example": func(session *Session) *ExperimentBuilder {
 		return &ExperimentBuilder{
 			build: func(config interface{}) *Experiment {

internal/engine/experiment/dnsping/dnsping.go

@@ -0,0 +1,201 @@
+// Package dnsping is the experimental dnsping experiment.
+//
+// See https://github.com/ooni/spec/blob/master/nettests/ts-035-dnsping.md.
+package dnsping
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/url"
+	"strings"
+	"time"
+
+	"github.com/ooni/probe-cli/v3/internal/measurex"
+	"github.com/ooni/probe-cli/v3/internal/model"
+)
+
+const (
+	testName    = "dnsping"
+	testVersion = "0.1.0"
+)
+
+// Config contains the experiment configuration.
+type Config struct {
+	// Delay is the delay between each repetition (in milliseconds).
+	Delay int64 `ooni:"number of milliseconds to wait before sending each ping"`
+
+	// Domains is the space-separated list of domains to measure.
+	Domains string `ooni:"space-separated list of domains to measure"`
+
+	// Repetitions is the number of repetitions for each ping.
+	Repetitions int64 `ooni:"number of times to repeat the measurement"`
+}
+
+func (c *Config) delay() time.Duration {
+	if c.Delay > 0 {
+		return time.Duration(c.Delay) * time.Millisecond
+	}
+	return time.Second
+}
+
+func (c Config) repetitions() int64 {
+	if c.Repetitions > 0 {
+		return c.Repetitions
+	}
+	return 10
+}
+
+func (c Config) domains() string {
+	if c.Domains != "" {
+		return c.Domains
+	}
+	return "edge-chat.instagram.com example.com"
+}
+
+// TestKeys contains the experiment results.
+type TestKeys struct {
+	Pings []*SinglePing `json:"pings"`
+}
+
+// TODO(bassosimone): save more data once the dnsping improvements at
+// github.com/bassosimone/websteps-illustrated contains have been merged
+// into this repository. When this happens, we'll able to save raw
+// queries and network events of each individual query.
+
+// SinglePing contains the results of a single ping.
+type SinglePing struct {
+	Queries []*measurex.ArchivalDNSLookupEvent `json:"queries"`
+}
+
+// Measurer performs the measurement.
+type Measurer struct {
+	config Config
+}
+
+// ExperimentName implements ExperimentMeasurer.ExperiExperimentName.
+func (m *Measurer) ExperimentName() string {
+	return testName
+}
+
+// ExperimentVersion implements ExperimentMeasurer.ExperimentVersion.
+func (m *Measurer) ExperimentVersion() string {
+	return testVersion
+}
+
+var (
+	// errNoInputProvided indicates you didn't provide any input
+	errNoInputProvided = errors.New("not input provided")
+
+	// errInputIsNotAnURL indicates that input is not an URL
+	errInputIsNotAnURL = errors.New("input is not an URL")
+
+	// errInvalidScheme indicates that the scheme is invalid
+	errInvalidScheme = errors.New("scheme must be udp")
+
+	// errMissingPort indicates that there is no port.
+	errMissingPort = errors.New("the URL must include a port")
+)
+
+// Run implements ExperimentMeasurer.Run.
+func (m *Measurer) Run(
+	ctx context.Context,
+	sess model.ExperimentSession,
+	measurement *model.Measurement,
+	callbacks model.ExperimentCallbacks,
+) error {
+	if measurement.Input == "" {
+		return errNoInputProvided
+	}
+	parsed, err := url.Parse(string(measurement.Input))
+	if err != nil {
+		return fmt.Errorf("%w: %s", errInputIsNotAnURL, err.Error())
+	}
+	if parsed.Scheme != "udp" {
+		return errInvalidScheme
+	}
+	if parsed.Port() == "" {
+		return errMissingPort
+	}
+	tk := new(TestKeys)
+	measurement.TestKeys = tk
+	mxmx := measurex.NewMeasurerWithDefaultSettings()
+	out := make(chan *measurex.DNSMeasurement)
+	domains := strings.Split(m.config.domains(), " ")
+	for _, domain := range domains {
+		go m.dnsPingLoop(ctx, mxmx, parsed.Host, domain, out)
+	}
+	// The following multiplication could overflow but we're always using small
+	// numbers so it's fine for us not to bother with checking for that.
+	//
+	// We emit two results (A and AAAA) for each domain and repetition.
+	numResults := int(m.config.repetitions()) * len(domains) * 2
+	for len(tk.Pings) < numResults {
+		meas := <-out
+		// TODO(bassosimone): when we merge the improvements at
+		// https://github.com/bassosimone/websteps-illustrated it
+		// will become unnecessary to split with query type
+		// as we're doing below.
+		queries := measurex.NewArchivalDNSLookupEventList(meas.LookupHost)
+		tk.Pings = append(tk.Pings, m.onlyQueryWithType(queries, "A")...)
+		tk.Pings = append(tk.Pings, m.onlyQueryWithType(queries, "AAAA")...)
+	}
+	return nil // return nil so we always submit the measurement
+}
+
+// onlyQueryWithType returns only the queries with the given type.
+func (m *Measurer) onlyQueryWithType(
+	in []*measurex.ArchivalDNSLookupEvent, kind string) (out []*SinglePing) {
+	for _, query := range in {
+		if query.QueryType == kind {
+			out = append(out, &SinglePing{
+				Queries: []*measurex.ArchivalDNSLookupEvent{query},
+			})
+		}
+	}
+	return
+}
+
+// dnsPingLoop sends all the ping requests and emits the results onto the out channel.
+func (m *Measurer) dnsPingLoop(ctx context.Context, mxmx *measurex.Measurer,
+	address string, domain string, out chan<- *measurex.DNSMeasurement) {
+	ticker := time.NewTicker(m.config.delay())
+	defer ticker.Stop()
+	for i := int64(0); i < m.config.repetitions(); i++ {
+		go m.dnsPingAsync(ctx, mxmx, address, domain, out)
+		<-ticker.C
+	}
+}
+
+// dnsPingAsync performs a DNS ping and emits the result onto the out channel.
+func (m *Measurer) dnsPingAsync(ctx context.Context, mxmx *measurex.Measurer,
+	address string, domain string, out chan<- *measurex.DNSMeasurement) {
+	out <- m.dnsRoundTrip(ctx, mxmx, address, domain)
+}
+
+// dnsRoundTrip performs a round trip and returns the results to the caller.
+func (m *Measurer) dnsRoundTrip(ctx context.Context, mxmx *measurex.Measurer,
+	address string, domain string) *measurex.DNSMeasurement {
+	// TODO(bassosimone): make the timeout user-configurable
+	ctx, cancel := context.WithTimeout(ctx, 3*time.Second)
+	defer cancel()
+	return mxmx.LookupHostUDP(ctx, domain, address)
+}
+
+// NewExperimentMeasurer creates a new ExperimentMeasurer.
+func NewExperimentMeasurer(config Config) model.ExperimentMeasurer {
+	return &Measurer{config: config}
+}
+
+// SummaryKeys contains summary keys for this experiment.
+//
+// Note that this structure is part of the ABI contract with ooniprobe
+// therefore we should be careful when changing it.
+type SummaryKeys struct {
+	IsAnomaly bool `json:"-"`
+}
+
+// GetSummaryKeys implements model.ExperimentMeasurer.GetSummaryKeys.
+func (m Measurer) GetSummaryKeys(measurement *model.Measurement) (interface{}, error) {
+	return SummaryKeys{IsAnomaly: false}, nil
+}

internal/engine/experiment/dnsping/dnsping_test.go

@@ -0,0 +1,159 @@
+package dnsping
+
+import (
+	"context"
+	"errors"
+	"log"
+	"net"
+	"net/url"
+	"testing"
+	"time"
+
+	"github.com/miekg/dns"
+	"github.com/ooni/probe-cli/v3/internal/engine/mockable"
+	"github.com/ooni/probe-cli/v3/internal/model"
+	"github.com/ooni/probe-cli/v3/internal/runtimex"
+)
+
+func TestConfig_domains(t *testing.T) {
+	c := Config{}
+	if c.domains() != "edge-chat.instagram.com example.com" {
+		t.Fatal("invalid default domains list")
+	}
+}
+
+func TestConfig_repetitions(t *testing.T) {
+	c := Config{}
+	if c.repetitions() != 10 {
+		t.Fatal("invalid default number of repetitions")
+	}
+}
+
+func TestConfig_delay(t *testing.T) {
+	c := Config{}
+	if c.delay() != time.Second {
+		t.Fatal("invalid default delay")
+	}
+}
+
+func TestMeasurer_run(t *testing.T) {
+	// expectedPings is the expected number of pings
+	const expectedPings = 4
+
+	// runHelper is an helper function to run this set of tests.
+	runHelper := func(input string) (*model.Measurement, model.ExperimentMeasurer, error) {
+		m := NewExperimentMeasurer(Config{
+			Domains:     "example.com",
+			Delay:       1, // millisecond
+			Repetitions: expectedPings,
+		})
+		if m.ExperimentName() != "dnsping" {
+			t.Fatal("invalid experiment name")
+		}
+		if m.ExperimentVersion() != "0.1.0" {
+			t.Fatal("invalid experiment version")
+		}
+		ctx := context.Background()
+		meas := &model.Measurement{
+			Input: model.MeasurementTarget(input),
+		}
+		sess := &mockable.Session{
+			MockableLogger: model.DiscardLogger,
+		}
+		callbacks := model.NewPrinterCallbacks(model.DiscardLogger)
+		err := m.Run(ctx, sess, meas, callbacks)
+		return meas, m, err
+	}
+
+	t.Run("with empty input", func(t *testing.T) {
+		_, _, err := runHelper("")
+		if !errors.Is(err, errNoInputProvided) {
+			t.Fatal("unexpected error", err)
+		}
+	})
+
+	t.Run("with invalid URL", func(t *testing.T) {
+		_, _, err := runHelper("\t")
+		if !errors.Is(err, errInputIsNotAnURL) {
+			t.Fatal("unexpected error", err)
+		}
+	})
+
+	t.Run("with invalid scheme", func(t *testing.T) {
+		_, _, err := runHelper("https://8.8.8.8:443/")
+		if !errors.Is(err, errInvalidScheme) {
+			t.Fatal("unexpected error", err)
+		}
+	})
+
+	t.Run("with missing port", func(t *testing.T) {
+		_, _, err := runHelper("udp://8.8.8.8")
+		if !errors.Is(err, errMissingPort) {
+			t.Fatal("unexpected error", err)
+		}
+	})
+
+	t.Run("with local listener", func(t *testing.T) {
+		srvrURL, dnsListener, err := startDNSServer()
+		if err != nil {
+			log.Fatal(err)
+		}
+		defer dnsListener.Close()
+		meas, m, err := runHelper(srvrURL)
+		if err != nil {
+			t.Fatal(err)
+		}
+		tk := meas.TestKeys.(*TestKeys)
+		if len(tk.Pings) != expectedPings*2 { // account for A & AAAA pings
+			t.Fatal("unexpected number of pings")
+		}
+		ask, err := m.GetSummaryKeys(meas)
+		if err != nil {
+			t.Fatal("cannot obtain summary")
+		}
+		summary := ask.(SummaryKeys)
+		if summary.IsAnomaly {
+			t.Fatal("expected no anomaly")
+		}
+	})
+}
+
+// startDNSServer starts a local DNS server.
+func startDNSServer() (string, net.PacketConn, error) {
+	dnsListener, err := net.ListenPacket("udp", "127.0.0.1:0")
+	if err != nil {
+		return "", nil, err
+	}
+	go runDNSServer(dnsListener)
+	URL := &url.URL{
+		Scheme: "udp",
+		Host:   dnsListener.LocalAddr().String(),
+		Path:   "/",
+	}
+	return URL.String(), dnsListener, nil
+}
+
+// runDNSServer runs the DNS server.
+func runDNSServer(dnsListener net.PacketConn) {
+	ds := &dns.Server{
+		Handler:    &dnsHandler{},
+		Net:        "udp",
+		PacketConn: dnsListener,
+	}
+	err := ds.ActivateAndServe()
+	if !errors.Is(err, net.ErrClosed) {
+		runtimex.PanicOnError(err, "ActivateAndServe failed")
+	}
+}
+
+// dnsHandler handles DNS requests.
+type dnsHandler struct{}
+
+// ServeDNS serves a DNS request
+func (h *dnsHandler) ServeDNS(rw dns.ResponseWriter, req *dns.Msg) {
+	m := new(dns.Msg)
+	m.Compress = true
+	m.MsgHdr.RecursionAvailable = true
+	m.SetRcode(req, dns.RcodeServerFailure)
+	rw.WriteMsg(m)
+}

internal/engine/experiment/simplequicping/simplequicping_test.go

@@ -98,11 +98,11 @@ func TestMeasurer_run(t *testing.T) {
 	})
 
 	t.Run("with local listener", func(t *testing.T) {
-		srvrURL, err := startEchoServer()
+		srvrURL, listener, err := startEchoServer()
 		if err != nil {
 			log.Fatal(err)
 		}
-		t.Log(srvrURL)
+		defer listener.Close()
 		meas, m, err := runHelper(srvrURL)
 		if err != nil {
 			t.Fatal(err)
@@ -127,10 +127,10 @@ func TestMeasurer_run(t *testing.T) {
 // SPDX-License-Identifier: MIT
 //
 // See https://github.com/lucas-clemente/quic-go/blob/v0.27.0/example/echo/echo.go#L34
-func startEchoServer() (string, error) {
+func startEchoServer() (string, quic.Listener, error) {
 	listener, err := quic.ListenAddr("127.0.0.1:0", generateTLSConfig(), nil)
 	if err != nil {
-		return "", err
+		return "", nil, err
 	}
 	go echoWorkerMain(listener)
 	URL := &url.URL{
@@ -138,7 +138,7 @@ func startEchoServer() (string, error) {
 		Host:   listener.Addr().String(),
 		Path:   "/",
 	}
-	return URL.String(), nil
+	return URL.String(), listener, nil
 }
 
 // Worker used by startEchoServer to accept a quic connection.
@@ -147,16 +147,17 @@ func startEchoServer() (string, error) {
 //
 // See https://github.com/lucas-clemente/quic-go/blob/v0.27.0/example/echo/echo.go#L34
 func echoWorkerMain(listener quic.Listener) {
-	defer listener.Close()
-	conn, err := listener.Accept(context.Background())
-	if err != nil {
-		panic(err)
+	for {
+		conn, err := listener.Accept(context.Background())
+		if err != nil {
+			return
+		}
+		stream, err := conn.AcceptStream(context.Background())
+		if err != nil {
+			continue
+		}
+		stream.Close()
 	}
-	stream, err := conn.AcceptStream(context.Background())
-	if err != nil {
-		panic(err)
-	}
-	stream.Close()
 }
 
 // Setup a bare-bones TLS config for the server.