refactor(oohelperd): use netxlite rather than netx

The oohelperd implementation did not actually need using netx because
it was just constructing default types with logging, which is what
netxlite already does. Hence, let's avoid using netx here.

See ooni/probe#2121

internal/cmd/oohelperd/internal/webconnectivity/http.go

@@ -8,6 +8,7 @@ import (
 	"sync"
 
 	"github.com/ooni/probe-cli/v3/internal/engine/experiment/webconnectivity"
+	"github.com/ooni/probe-cli/v3/internal/model"
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
 	"github.com/ooni/probe-cli/v3/internal/tracex"
 )
@@ -18,7 +19,7 @@ type CtrlHTTPResponse = webconnectivity.ControlHTTPRequestResult
 
 // HTTPConfig configures the HTTP check.
 type HTTPConfig struct {
-	Client            *http.Client
+	Client            model.HTTPClient
 	Headers           map[string][]string
 	MaxAcceptableBody int64
 	Out               chan CtrlHTTPResponse

internal/cmd/oohelperd/internal/webconnectivity/measure.go

@@ -3,7 +3,6 @@ package webconnectivity
 import (
 	"context"
 	"net"
-	"net/http"
 	"net/url"
 	"sync"
 
@@ -21,7 +20,7 @@ type (
 
 // MeasureConfig contains configuration for Measure.
 type MeasureConfig struct {
-	Client            *http.Client
+	Client            model.HTTPClient
 	Dialer            model.Dialer
 	MaxAcceptableBody int64
 	Resolver          model.Resolver

internal/cmd/oohelperd/internal/webconnectivity/webconnectivity.go

@@ -14,7 +14,7 @@ import (
 
 // Handler implements the Web Connectivity test helper HTTP API.
 type Handler struct {
-	Client            *http.Client
+	Client            model.HTTPClient
 	Dialer            model.Dialer
 	MaxAcceptableBody int64
 	Resolver          model.Resolver

internal/cmd/oohelperd/oohelperd.go

@@ -10,32 +10,33 @@ import (
 
 	"github.com/apex/log"
 	"github.com/ooni/probe-cli/v3/internal/cmd/oohelperd/internal/webconnectivity"
-	"github.com/ooni/probe-cli/v3/internal/engine/netx"
 	"github.com/ooni/probe-cli/v3/internal/model"
-	"github.com/ooni/probe-cli/v3/internal/runtimex"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 const maxAcceptableBody = 1 << 24
 
 var (
-	dialer    model.Dialer
-	endpoint  = flag.String("endpoint", ":8080", "Endpoint where to listen")
-	httpx     *http.Client
-	resolver  model.Resolver
-	srvcancel context.CancelFunc
-	srvctx    context.Context
-	srvwg     = new(sync.WaitGroup)
+	dialer     model.Dialer
+	endpoint   = flag.String("endpoint", ":8080", "Endpoint where to listen")
+	httpClient model.HTTPClient
+	resolver   model.Resolver
+	srvcancel  context.CancelFunc
+	srvctx     context.Context
+	srvwg      = new(sync.WaitGroup)
 )
 
 func init() {
 	srvctx, srvcancel = context.WithCancel(context.Background())
-	dialer = netx.NewDialer(netx.Config{Logger: log.Log})
-	txp := netx.NewHTTPTransport(netx.Config{Logger: log.Log})
-	httpx = &http.Client{Transport: txp}
-	// fix: use 8.8.8.8:53/udp so we pin to a specific resolver.
-	var err error
-	resolver, err = netx.NewDNSClient(netx.Config{Logger: log.Log}, "udp://8.8.8.8:53")
-	runtimex.PanicOnError(err, "NewDNSClient failed")
+	// Implementation note: pin to a specific resolver so we don't depend upon the
+	// default resolver configured by the box. Also, use an encrypted transport thus
+	// we're less vulnerable to any policy implemented by the box's provider.
+	resolver = netxlite.NewParallelDNSOverHTTPSResolver(log.Log, "https://8.8.8.8/dns-query")
+	thx := netxlite.NewTLSHandshakerStdlib(log.Log)
+	dialer = netxlite.NewDialerWithResolver(log.Log, resolver)
+	tlsDialer := netxlite.NewTLSDialer(dialer, thx)
+	txp := netxlite.NewHTTPTransport(log.Log, dialer, tlsDialer)
+	httpClient = netxlite.NewHTTPClient(txp)
 }
 
 func shutdown(srv *http.Server) {
@@ -58,7 +59,7 @@ func main() {
 func testableMain() {
 	mux := http.NewServeMux()
 	mux.Handle("/", webconnectivity.Handler{
-		Client:            httpx,
+		Client:            httpClient,
 		Dialer:            dialer,
 		MaxAcceptableBody: maxAcceptableBody,
 		Resolver:          resolver,