refactor: merge dnsx and errorsx into netxlite (#517)

When preparing a tutorial for netxlite, I figured it is easier
to tell people "hey, this is the package you should use for all
low-level networking stuff" rather than introducing people to
a set of packages working together where some piece of functionality
is here and some other piece is there.

Part of https://github.com/ooni/probe/issues/1591

internal/engine/experiment/webconnectivity/control.go

@@ -7,7 +7,7 @@ import (
 	"github.com/ooni/probe-cli/v3/internal/engine/httpx"
 	legacyerrorsx "github.com/ooni/probe-cli/v3/internal/engine/legacy/errorsx"
 	"github.com/ooni/probe-cli/v3/internal/engine/model"
-	"github.com/ooni/probe-cli/v3/internal/netxlite/errorsx"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 // ControlRequest is the request that we send to the control
@@ -62,7 +62,7 @@ func Control(
 	// make sure error is wrapped
 	err = legacyerrorsx.SafeErrWrapperBuilder{
 		Error:     clnt.PostJSON(ctx, "/", creq, &out),
-		Operation: errorsx.TopLevelOperation,
+		Operation: netxlite.TopLevelOperation,
 	}.MaybeBuild()
 	sess.Logger().Infof("control for %s... %+v", creq.HTTPRequest, err)
 	(&out.DNS).FillASNs(sess)

internal/engine/experiment/webconnectivity/dnsanalysis.go

@@ -4,7 +4,7 @@ import (
 	"net"
 	"net/url"
 
-	"github.com/ooni/probe-cli/v3/internal/netxlite/errorsx"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 // DNSAnalysisResult contains the results of analysing comparing
@@ -44,7 +44,7 @@ func DNSAnalysis(URL *url.URL, measurement DNSLookupResult,
 		switch *control.DNS.Failure {
 		case DNSNameError: // the control returns this on NXDOMAIN error
 			switch *measurement.Failure {
-			case errorsx.FailureDNSNXDOMAINError:
+			case netxlite.FailureDNSNXDOMAINError:
 				out.DNSConsistency = &DNSConsistent
 			}
 		}

internal/engine/experiment/webconnectivity/dnsanalysis_test.go

@@ -7,11 +7,11 @@ import (
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/ooni/probe-cli/v3/internal/engine/experiment/webconnectivity"
-	"github.com/ooni/probe-cli/v3/internal/netxlite/errorsx"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 func TestDNSAnalysis(t *testing.T) {
-	measurementFailure := errorsx.FailureDNSNXDOMAINError
+	measurementFailure := netxlite.FailureDNSNXDOMAINError
 	controlFailure := webconnectivity.DNSNameError
 	eofFailure := io.EOF.Error()
 	type args struct {

internal/engine/experiment/webconnectivity/summary.go

@@ -5,7 +5,7 @@ import (
 
 	"github.com/ooni/probe-cli/v3/internal/engine/experiment/webconnectivity/internal"
 	"github.com/ooni/probe-cli/v3/internal/engine/model"
-	"github.com/ooni/probe-cli/v3/internal/netxlite/errorsx"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 // The following set of status flags identifies in a more nuanced way the
@@ -127,7 +127,7 @@ func Summarize(tk *TestKeys) (out Summary) {
 	// If DNS failed with NXDOMAIN and the control DNS is consistent, then it
 	// means this website does not exist anymore.
 	if tk.DNSExperimentFailure != nil &&
-		*tk.DNSExperimentFailure == errorsx.FailureDNSNXDOMAINError &&
+		*tk.DNSExperimentFailure == netxlite.FailureDNSNXDOMAINError &&
 		tk.DNSConsistency != nil && *tk.DNSConsistency == DNSConsistent {
 		// TODO(bassosimone): MK flags this as accessible. This result is debatable. We
 		// are doing what MK does. But we most likely want to make it better later.
@@ -140,7 +140,7 @@ func Summarize(tk *TestKeys) (out Summary) {
 	// Otherwise, if DNS failed with NXDOMAIN, it's DNS based blocking.
 	// TODO(bassosimone): do we wanna include other errors here? Like timeout?
 	if tk.DNSExperimentFailure != nil &&
-		*tk.DNSExperimentFailure == errorsx.FailureDNSNXDOMAINError {
+		*tk.DNSExperimentFailure == netxlite.FailureDNSNXDOMAINError {
 		out.Accessible = &inaccessible
 		out.BlockingReason = &dns
 		out.Status |= StatusAnomalyDNS | StatusExperimentDNS
@@ -184,41 +184,41 @@ func Summarize(tk *TestKeys) (out Summary) {
 	if tk.Requests[0].Failure != nil {
 		out.Status |= StatusExperimentHTTP
 		switch *tk.Requests[0].Failure {
-		case errorsx.FailureConnectionRefused:
+		case netxlite.FailureConnectionRefused:
 			// This is possibly because a subsequent connection to some
 			// other endpoint has been blocked. We call this http-failure
 			// because this is what MK would actually do.
 			out.BlockingReason = &httpFailure
 			out.Accessible = &inaccessible
 			out.Status |= StatusAnomalyConnect
-		case errorsx.FailureConnectionReset:
+		case netxlite.FailureConnectionReset:
 			// We don't currently support TLS failures and we don't have a
 			// way to know if it was during TLS or later. So, for now we are
 			// going to call this error condition an http-failure.
 			out.BlockingReason = &httpFailure
 			out.Accessible = &inaccessible
 			out.Status |= StatusAnomalyReadWrite
-		case errorsx.FailureDNSNXDOMAINError:
+		case netxlite.FailureDNSNXDOMAINError:
 			// This is possibly because a subsequent resolution to
 			// some other domain name has been blocked.
 			out.BlockingReason = &dns
 			out.Accessible = &inaccessible
 			out.Status |= StatusAnomalyDNS
-		case errorsx.FailureEOFError:
+		case netxlite.FailureEOFError:
 			// We have seen this happening with TLS handshakes as well as
 			// sometimes with HTTP blocking. So http-failure.
 			out.BlockingReason = &httpFailure
 			out.Accessible = &inaccessible
 			out.Status |= StatusAnomalyReadWrite
-		case errorsx.FailureGenericTimeoutError:
+		case netxlite.FailureGenericTimeoutError:
 			// Alas, here we don't know whether it's connect or whether it's
 			// perhaps the TLS handshake. So use the same classification used by MK.
 			out.BlockingReason = &httpFailure
 			out.Accessible = &inaccessible
 			out.Status |= StatusAnomalyUnknown
-		case errorsx.FailureSSLInvalidHostname,
-			errorsx.FailureSSLInvalidCertificate,
-			errorsx.FailureSSLUnknownAuthority:
+		case netxlite.FailureSSLInvalidHostname,
+			netxlite.FailureSSLInvalidCertificate,
+			netxlite.FailureSSLUnknownAuthority:
 			// We treat these three cases equally. Misconfiguration is a bit
 			// less likely since we also checked with the control. Since there
 			// is no TLS, for now we're going to call this http-failure.

internal/engine/experiment/webconnectivity/summary_test.go

@@ -7,7 +7,7 @@ import (
 	"github.com/google/go-cmp/cmp"
 	"github.com/ooni/probe-cli/v3/internal/engine/experiment/webconnectivity"
 	"github.com/ooni/probe-cli/v3/internal/engine/netx/archival"
-	"github.com/ooni/probe-cli/v3/internal/netxlite/errorsx"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 func TestSummarize(t *testing.T) {
@@ -18,14 +18,14 @@ func TestSummarize(t *testing.T) {
 		httpDiff               = "http-diff"
 		httpFailure            = "http-failure"
 		nilstring              *string
-		probeConnectionRefused = errorsx.FailureConnectionRefused
-		probeConnectionReset   = errorsx.FailureConnectionReset
-		probeEOFError          = errorsx.FailureEOFError
-		probeNXDOMAIN          = errorsx.FailureDNSNXDOMAINError
-		probeTimeout           = errorsx.FailureGenericTimeoutError
-		probeSSLInvalidHost    = errorsx.FailureSSLInvalidHostname
-		probeSSLInvalidCert    = errorsx.FailureSSLInvalidCertificate
-		probeSSLUnknownAuth    = errorsx.FailureSSLUnknownAuthority
+		probeConnectionRefused = netxlite.FailureConnectionRefused
+		probeConnectionReset   = netxlite.FailureConnectionReset
+		probeEOFError          = netxlite.FailureEOFError
+		probeNXDOMAIN          = netxlite.FailureDNSNXDOMAINError
+		probeTimeout           = netxlite.FailureGenericTimeoutError
+		probeSSLInvalidHost    = netxlite.FailureSSLInvalidHostname
+		probeSSLInvalidCert    = netxlite.FailureSSLInvalidCertificate
+		probeSSLUnknownAuth    = netxlite.FailureSSLUnknownAuthority
 		tcpIP                  = "tcp_ip"
 		trueValue              = true
 	)

internal/engine/experiment/webconnectivity/webconnectivity_test.go

@@ -13,7 +13,7 @@ import (
 	"github.com/ooni/probe-cli/v3/internal/engine/experiment/webconnectivity"
 	"github.com/ooni/probe-cli/v3/internal/engine/model"
 	"github.com/ooni/probe-cli/v3/internal/engine/netx/archival"
-	"github.com/ooni/probe-cli/v3/internal/netxlite/errorsx"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 func TestNewExperimentMeasurer(t *testing.T) {
@@ -69,10 +69,10 @@ func TestMeasureWithCancelledContext(t *testing.T) {
 		t.Fatal(err)
 	}
 	tk := measurement.TestKeys.(*webconnectivity.TestKeys)
-	if *tk.ControlFailure != errorsx.FailureInterrupted {
+	if *tk.ControlFailure != netxlite.FailureInterrupted {
 		t.Fatal("unexpected control_failure")
 	}
-	if *tk.DNSExperimentFailure != errorsx.FailureInterrupted {
+	if *tk.DNSExperimentFailure != netxlite.FailureInterrupted {
 		t.Fatal("unexpected dns_experiment_failure")
 	}
 	if tk.HTTPExperimentFailure != nil {