From d4013c95dcd439f32a86487e9c532ea683ace030 Mon Sep 17 00:00:00 2001
From: Simone Basso <bassosimone@gmail.com>
Date: Fri, 21 Jul 2023 10:11:24 +0200
Subject: [PATCH] refactor(oohelperd): move code out of package main (#1189)

This diff refactors the oohelperd implementation to move code out of
package main. Specifically, we move most of the code from
`./internal/cmd/oohelperd` to `./internal/oohelperd`. Thanks to this
refactoring, we can reuse the implementation of the oohelperd for
writing netem based integration tests.

Part of https://github.com/ooni/probe/issues/2461

---------

Co-authored-by: kelmenhorst <k.elmenhorst@mailbox.org>
---
 internal/cmd/oohelperd/handler.go            | 118 ----------
 internal/cmd/oohelperd/main.go               | 106 +--------
 internal/cmd/oohelperd/main_test.go          |   5 +
 internal/{cmd => }/oohelperd/dns.go          |   2 +-
 internal/{cmd => }/oohelperd/dns_test.go     |   2 +-
 internal/oohelperd/handler.go                | 219 +++++++++++++++++++
 internal/{cmd => }/oohelperd/handler_test.go |   8 +-
 internal/{cmd => }/oohelperd/http.go         |   2 +-
 internal/{cmd => }/oohelperd/http_test.go    |   2 +-
 internal/{cmd => }/oohelperd/ipinfo.go       |   2 +-
 internal/{cmd => }/oohelperd/ipinfo_test.go  |   2 +-
 internal/{cmd => }/oohelperd/logging.go      |   2 +-
 internal/{cmd => }/oohelperd/logging_test.go |   2 +-
 internal/{cmd => }/oohelperd/measure.go      |   4 +-
 internal/{cmd => }/oohelperd/metrics.go      |   2 +-
 internal/{cmd => }/oohelperd/quic.go         |   2 +-
 internal/{cmd => }/oohelperd/tcptls.go       |   2 +-
 internal/{cmd => }/oohelperd/tcptls_test.go  |   2 +-
 18 files changed, 244 insertions(+), 240 deletions(-)
 delete mode 100644 internal/cmd/oohelperd/handler.go
 rename internal/{cmd => }/oohelperd/dns.go (99%)
 rename internal/{cmd => }/oohelperd/dns_test.go (99%)
 create mode 100644 internal/oohelperd/handler.go
 rename internal/{cmd => }/oohelperd/handler_test.go (96%)
 rename internal/{cmd => }/oohelperd/http.go (99%)
 rename internal/{cmd => }/oohelperd/http_test.go (99%)
 rename internal/{cmd => }/oohelperd/ipinfo.go (99%)
 rename internal/{cmd => }/oohelperd/ipinfo_test.go (99%)
 rename internal/{cmd => }/oohelperd/logging.go (98%)
 rename internal/{cmd => }/oohelperd/logging_test.go (99%)
 rename internal/{cmd => }/oohelperd/measure.go (98%)
 rename internal/{cmd => }/oohelperd/metrics.go (98%)
 rename internal/{cmd => }/oohelperd/quic.go (99%)
 rename internal/{cmd => }/oohelperd/tcptls.go (99%)
 rename internal/{cmd => }/oohelperd/tcptls_test.go (98%)

diff --git a/internal/cmd/oohelperd/handler.go b/internal/cmd/oohelperd/handler.go
deleted file mode 100644
index 4e6f52aa5b..0000000000
--- a/internal/cmd/oohelperd/handler.go
+++ /dev/null
@@ -1,118 +0,0 @@
-package main
-
-//
-// HTTP handler
-//
-
-import (
-	"context"
-	"encoding/json"
-	"fmt"
-	"io"
-	"net/http"
-	"sync/atomic"
-	"time"
-
-	"github.com/ooni/probe-cli/v3/internal/model"
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
-	"github.com/ooni/probe-cli/v3/internal/runtimex"
-	"github.com/ooni/probe-cli/v3/internal/version"
-)
-
-// handler is an [http.Handler] implementing the Web
-// Connectivity test helper HTTP API.
-type handler struct {
-	// BaseLogger is the MANDATORY logger to use.
-	BaseLogger model.Logger
-
-	// Indexer is the MANDATORY atomic integer used to assign an index to requests.
-	Indexer *atomic.Int64
-
-	// MaxAcceptableBody is the MANDATORY maximum acceptable response body.
-	MaxAcceptableBody int64
-
-	// Measure is the MANDATORY function that the handler should call
-	// for producing a response for a valid incoming request.
-	Measure func(ctx context.Context, config *handler, creq *model.THRequest) (*model.THResponse, error)
-
-	// NewDialer is the MANDATORY factory to create a new Dialer.
-	NewDialer func(model.Logger) model.Dialer
-
-	// NewHTTPClient is the MANDATORY factory to create a new HTTPClient.
-	NewHTTPClient func(model.Logger) model.HTTPClient
-
-	// NewHTTP3Client is the MANDATORY factory to create a new HTTP3Client.
-	NewHTTP3Client func(model.Logger) model.HTTPClient
-
-	// NewQUICDialer is the MANDATORY factory to create a new QUICDialer.
-	NewQUICDialer func(model.Logger) model.QUICDialer
-
-	// NewResolver is the MANDATORY factory for creating a new resolver.
-	NewResolver func(model.Logger) model.Resolver
-
-	// NewTLSHandshaker is the MANDATORY factory for creating a new TLS handshaker.
-	NewTLSHandshaker func(model.Logger) model.TLSHandshaker
-}
-
-var _ http.Handler = &handler{}
-
-// ServeHTTP implements http.Handler.
-func (h *handler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
-	// track the number of in-flight requests
-	metricRequestsInflight.Inc()
-	defer metricRequestsInflight.Dec()
-
-	// create and add the Server header
-	w.Header().Add("Server", fmt.Sprintf(
-		"oohelperd/%s ooniprobe-engine/%s",
-		version.Version,
-		version.Version,
-	))
-
-	// we only handle the POST method
-	if req.Method != "POST" {
-		metricRequestsCount.WithLabelValues("400", "bad_request_method").Inc()
-		w.WriteHeader(400)
-		return
-	}
-
-	// read and parse request body
-	reader := io.LimitReader(req.Body, h.MaxAcceptableBody)
-	data, err := netxlite.ReadAllContext(req.Context(), reader)
-	if err != nil {
-		metricRequestsCount.WithLabelValues("400", "request_body_too_large").Inc()
-		w.WriteHeader(400)
-		return
-	}
-	var creq ctrlRequest
-	if err := json.Unmarshal(data, &creq); err != nil {
-		metricRequestsCount.WithLabelValues("400", "cannot_unmarshal_request_body").Inc()
-		w.WriteHeader(400)
-		return
-	}
-
-	// measure the given input
-	started := time.Now()
-	cresp, err := h.Measure(req.Context(), h, &creq)
-	elapsed := time.Since(started)
-
-	// track the time required to produce a response
-	metricWCTaskDurationSeconds.Observe(float64(elapsed.Seconds()))
-
-	// handle the case of fundamental failure
-	if err != nil {
-		metricRequestsCount.WithLabelValues("400", "wctask_failed").Inc()
-		w.WriteHeader(400)
-		return
-	}
-
-	// produce successful response.
-	//
-	// Note: we assume that json.Marshal cannot fail because it's a
-	// clearly-serializable data structure.
-	metricRequestsCount.WithLabelValues("200", "ok").Inc()
-	data, err = json.Marshal(cresp)
-	runtimex.PanicOnError(err, "json.Marshal failed")
-	w.Header().Add("Content-Type", "application/json")
-	w.Write(data)
-}
diff --git a/internal/cmd/oohelperd/main.go b/internal/cmd/oohelperd/main.go
index 3d48afa401..f777157a15 100644
--- a/internal/cmd/oohelperd/main.go
+++ b/internal/cmd/oohelperd/main.go
@@ -7,28 +7,20 @@ import (
 	"fmt"
 	"net"
 	"net/http"
-	"net/http/cookiejar"
 	"net/http/pprof"
 	"os"
 	"os/signal"
 	"sync"
-	"sync/atomic"
 	"syscall"
 	"time"
 
 	"github.com/apex/log"
-	"github.com/ooni/probe-cli/v3/internal/model"
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
+	"github.com/ooni/probe-cli/v3/internal/oohelperd"
 	"github.com/ooni/probe-cli/v3/internal/runtimex"
 	"github.com/ooni/probe-cli/v3/internal/version"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
-	"golang.org/x/net/publicsuffix"
 )
 
-// maxAcceptableBodySize is the maximum acceptable body size for incoming
-// API requests as well as when we're measuring webpages.
-const maxAcceptableBodySize = 1 << 24
-
 var (
 	// apiEndpoint is the endpoint where we serve ooniprobe requests
 	apiEndpoint = flag.String("api-endpoint", "127.0.0.1:8080", "API endpoint")
@@ -58,16 +50,6 @@ var (
 	versionFlag = flag.Bool("version", false, "Prints version information on the stdout")
 )
 
-// newResolver creates a new [model.Resolver] suitable for serving
-// requests coming from ooniprobe clients.
-func newResolver(logger model.Logger) model.Resolver {
-	// 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(logger, "https://dns.google/dns-query")
-	return resolver
-}
-
 // shutdown calls srv.Shutdown with a reasonably long timeout. The srv.Shutdown
 // function will immediately close any open listener and then will wait until
 // all pending connections are closed or the context has expired. By giving pending
@@ -81,90 +63,6 @@ func shutdown(srv *http.Server, wg *sync.WaitGroup) {
 	srv.Shutdown(ctx)
 }
 
-// newCookieJar is the factory for constructing a new cookier jar.
-func newCookieJar() *cookiejar.Jar {
-	// Implementation note: the [cookiejar.New] function always returns a
-	// nil error; hence, it's safe here to use [runtimex.Try1].
-	return runtimex.Try1(cookiejar.New(&cookiejar.Options{
-		PublicSuffixList: publicsuffix.List,
-	}))
-}
-
-// newHTTPClientWithTransportFactory creates a new HTTP client.
-func newHTTPClientWithTransportFactory(
-	logger model.Logger,
-	txpFactory func(model.DebugLogger, model.Resolver) model.HTTPTransport,
-) model.HTTPClient {
-	// If the DoH resolver we're using insists that a given domain maps to
-	// bogons, make sure we're going to fail the HTTP measurement.
-	//
-	// The TCP measurements scheduler in ipinfo.go will also refuse to
-	// schedule TCP measurements for bogons.
-	//
-	// While this seems theoretical, as of 2022-08-28, I see:
-	//
-	//     % host polito.it
-	//     polito.it has address 192.168.59.6
-	//     polito.it has address 192.168.40.1
-	//     polito.it mail is handled by 10 mx.polito.it.
-	//
-	// So, it's better to consider this as a possible corner case.
-	reso := netxlite.MaybeWrapWithBogonResolver(
-		true, // enabled
-		newResolver(logger),
-	)
-
-	// fix: We MUST set a cookie jar for measuring HTTP. See
-	// https://github.com/ooni/probe/issues/2488 for additional
-	// context and pointers to the relevant measurements.
-	client := &http.Client{
-		Transport:     txpFactory(logger, reso),
-		CheckRedirect: nil,
-		Jar:           newCookieJar(),
-		Timeout:       0,
-	}
-
-	return netxlite.WrapHTTPClient(client)
-}
-
-// newHandler constructs the [handler] used by [main].
-func newHandler() *handler {
-	return &handler{
-		BaseLogger:        log.Log,
-		Indexer:           &atomic.Int64{},
-		MaxAcceptableBody: maxAcceptableBodySize,
-		Measure:           measure,
-
-		NewHTTPClient: func(logger model.Logger) model.HTTPClient {
-			return newHTTPClientWithTransportFactory(
-				logger,
-				netxlite.NewHTTPTransportWithResolver,
-			)
-		},
-
-		NewHTTP3Client: func(logger model.Logger) model.HTTPClient {
-			return newHTTPClientWithTransportFactory(
-				logger,
-				netxlite.NewHTTP3TransportWithResolver,
-			)
-		},
-
-		NewDialer: func(logger model.Logger) model.Dialer {
-			return netxlite.NewDialerWithoutResolver(logger)
-		},
-		NewQUICDialer: func(logger model.Logger) model.QUICDialer {
-			return netxlite.NewQUICDialerWithoutResolver(
-				netxlite.NewQUICListener(),
-				logger,
-			)
-		},
-		NewResolver: newResolver,
-		NewTLSHandshaker: func(logger model.Logger) model.TLSHandshaker {
-			return netxlite.NewTLSHandshakerStdlib(logger)
-		},
-	}
-}
-
 func main() {
 	// parse command line options
 	flag.Parse()
@@ -194,7 +92,7 @@ func main() {
 	mux := http.NewServeMux()
 
 	// add the main oohelperd handler to the mux
-	mux.Handle("/", newHandler())
+	mux.Handle("/", oohelperd.NewHandler())
 
 	// create a listening server for serving ooniprobe requests
 	srv := &http.Server{Addr: *apiEndpoint, Handler: mux}
diff --git a/internal/cmd/oohelperd/main_test.go b/internal/cmd/oohelperd/main_test.go
index 8aefe4da8b..335e07bb3b 100644
--- a/internal/cmd/oohelperd/main_test.go
+++ b/internal/cmd/oohelperd/main_test.go
@@ -15,6 +15,11 @@ import (
 	"github.com/ooni/probe-cli/v3/internal/runtimex"
 )
 
+type (
+	ctrlRequest  = model.THRequest
+	ctrlResponse = model.THResponse
+)
+
 func TestMainRunServerWorkingAsIntended(t *testing.T) {
 	// let the kernel pick a random free port
 	*apiEndpoint = "127.0.0.1:0"
diff --git a/internal/cmd/oohelperd/dns.go b/internal/oohelperd/dns.go
similarity index 99%
rename from internal/cmd/oohelperd/dns.go
rename to internal/oohelperd/dns.go
index c7a1f2c83a..b56b9e20ee 100644
--- a/internal/cmd/oohelperd/dns.go
+++ b/internal/oohelperd/dns.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 //
 // DNS measurements
diff --git a/internal/cmd/oohelperd/dns_test.go b/internal/oohelperd/dns_test.go
similarity index 99%
rename from internal/cmd/oohelperd/dns_test.go
rename to internal/oohelperd/dns_test.go
index 5a6b3e354b..fc5efacc4a 100644
--- a/internal/cmd/oohelperd/dns_test.go
+++ b/internal/oohelperd/dns_test.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 import (
 	"context"
diff --git a/internal/oohelperd/handler.go b/internal/oohelperd/handler.go
new file mode 100644
index 0000000000..15eda5435f
--- /dev/null
+++ b/internal/oohelperd/handler.go
@@ -0,0 +1,219 @@
+package oohelperd
+
+//
+// HTTP handler
+//
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/cookiejar"
+	"sync/atomic"
+	"time"
+
+	"github.com/apex/log"
+	"github.com/ooni/probe-cli/v3/internal/model"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
+	"github.com/ooni/probe-cli/v3/internal/runtimex"
+	"github.com/ooni/probe-cli/v3/internal/version"
+	"golang.org/x/net/publicsuffix"
+)
+
+// maxAcceptableBodySize is the maximum acceptable body size for incoming
+// API requests as well as when we're measuring webpages.
+const maxAcceptableBodySize = 1 << 24
+
+// Handler is an [http.Handler] implementing the Web
+// Connectivity test helper HTTP API.
+type Handler struct {
+	// BaseLogger is the MANDATORY logger to use.
+	BaseLogger model.Logger
+
+	// Indexer is the MANDATORY atomic integer used to assign an index to requests.
+	Indexer *atomic.Int64
+
+	// MaxAcceptableBody is the MANDATORY maximum acceptable response body.
+	MaxAcceptableBody int64
+
+	// Measure is the MANDATORY function that the handler should call
+	// for producing a response for a valid incoming request.
+	Measure func(ctx context.Context, config *Handler, creq *model.THRequest) (*model.THResponse, error)
+
+	// NewDialer is the MANDATORY factory to create a new Dialer.
+	NewDialer func(model.Logger) model.Dialer
+
+	// NewHTTPClient is the MANDATORY factory to create a new HTTPClient.
+	NewHTTPClient func(model.Logger) model.HTTPClient
+
+	// NewHTTP3Client is the MANDATORY factory to create a new HTTP3Client.
+	NewHTTP3Client func(model.Logger) model.HTTPClient
+
+	// NewQUICDialer is the MANDATORY factory to create a new QUICDialer.
+	NewQUICDialer func(model.Logger) model.QUICDialer
+
+	// NewResolver is the MANDATORY factory for creating a new resolver.
+	NewResolver func(model.Logger) model.Resolver
+
+	// NewTLSHandshaker is the MANDATORY factory for creating a new TLS handshaker.
+	NewTLSHandshaker func(model.Logger) model.TLSHandshaker
+}
+
+var _ http.Handler = &Handler{}
+
+// NewHandler constructs the [handler].
+func NewHandler() *Handler {
+	return &Handler{
+		BaseLogger:        log.Log,
+		Indexer:           &atomic.Int64{},
+		MaxAcceptableBody: maxAcceptableBodySize,
+		Measure:           measure,
+
+		NewHTTPClient: func(logger model.Logger) model.HTTPClient {
+			return newHTTPClientWithTransportFactory(
+				logger,
+				netxlite.NewHTTPTransportWithResolver,
+			)
+		},
+
+		NewHTTP3Client: func(logger model.Logger) model.HTTPClient {
+			return newHTTPClientWithTransportFactory(
+				logger,
+				netxlite.NewHTTP3TransportWithResolver,
+			)
+		},
+
+		NewDialer: func(logger model.Logger) model.Dialer {
+			return netxlite.NewDialerWithoutResolver(logger)
+		},
+		NewQUICDialer: func(logger model.Logger) model.QUICDialer {
+			return netxlite.NewQUICDialerWithoutResolver(
+				netxlite.NewQUICListener(),
+				logger,
+			)
+		},
+		NewResolver: newResolver,
+		NewTLSHandshaker: func(logger model.Logger) model.TLSHandshaker {
+			return netxlite.NewTLSHandshakerStdlib(logger)
+		},
+	}
+}
+
+// ServeHTTP implements http.Handler.
+func (h *Handler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	// track the number of in-flight requests
+	metricRequestsInflight.Inc()
+	defer metricRequestsInflight.Dec()
+
+	// create and add the Server header
+	w.Header().Add("Server", fmt.Sprintf(
+		"oohelperd/%s ooniprobe-engine/%s",
+		version.Version,
+		version.Version,
+	))
+
+	// we only handle the POST method
+	if req.Method != "POST" {
+		metricRequestsCount.WithLabelValues("400", "bad_request_method").Inc()
+		w.WriteHeader(400)
+		return
+	}
+
+	// read and parse request body
+	reader := io.LimitReader(req.Body, h.MaxAcceptableBody)
+	data, err := netxlite.ReadAllContext(req.Context(), reader)
+	if err != nil {
+		metricRequestsCount.WithLabelValues("400", "request_body_too_large").Inc()
+		w.WriteHeader(400)
+		return
+	}
+	var creq ctrlRequest
+	if err := json.Unmarshal(data, &creq); err != nil {
+		metricRequestsCount.WithLabelValues("400", "cannot_unmarshal_request_body").Inc()
+		w.WriteHeader(400)
+		return
+	}
+
+	// measure the given input
+	started := time.Now()
+	cresp, err := h.Measure(req.Context(), h, &creq)
+	elapsed := time.Since(started)
+
+	// track the time required to produce a response
+	metricWCTaskDurationSeconds.Observe(float64(elapsed.Seconds()))
+
+	// handle the case of fundamental failure
+	if err != nil {
+		metricRequestsCount.WithLabelValues("400", "wctask_failed").Inc()
+		w.WriteHeader(400)
+		return
+	}
+
+	// produce successful response.
+	//
+	// Note: we assume that json.Marshal cannot fail because it's a
+	// clearly-serializable data structure.
+	metricRequestsCount.WithLabelValues("200", "ok").Inc()
+	data, err = json.Marshal(cresp)
+	runtimex.PanicOnError(err, "json.Marshal failed")
+	w.Header().Add("Content-Type", "application/json")
+	w.Write(data)
+}
+
+// newResolver creates a new [model.Resolver] suitable for serving
+// requests coming from ooniprobe clients.
+func newResolver(logger model.Logger) model.Resolver {
+	// 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(logger, "https://dns.google/dns-query")
+	return resolver
+}
+
+// newCookieJar is the factory for constructing a new cookier jar.
+func newCookieJar() *cookiejar.Jar {
+	// Implementation note: the [cookiejar.New] function always returns a
+	// nil error; hence, it's safe here to use [runtimex.Try1].
+	return runtimex.Try1(cookiejar.New(&cookiejar.Options{
+		PublicSuffixList: publicsuffix.List,
+	}))
+}
+
+// newHTTPClientWithTransportFactory creates a new HTTP client.
+func newHTTPClientWithTransportFactory(
+	logger model.Logger,
+	txpFactory func(model.DebugLogger, model.Resolver) model.HTTPTransport,
+) model.HTTPClient {
+	// If the DoH resolver we're using insists that a given domain maps to
+	// bogons, make sure we're going to fail the HTTP measurement.
+	//
+	// The TCP measurements scheduler in ipinfo.go will also refuse to
+	// schedule TCP measurements for bogons.
+	//
+	// While this seems theoretical, as of 2022-08-28, I see:
+	//
+	//     % host polito.it
+	//     polito.it has address 192.168.59.6
+	//     polito.it has address 192.168.40.1
+	//     polito.it mail is handled by 10 mx.polito.it.
+	//
+	// So, it's better to consider this as a possible corner case.
+	reso := netxlite.MaybeWrapWithBogonResolver(
+		true, // enabled
+		newResolver(logger),
+	)
+
+	// fix: We MUST set a cookie jar for measuring HTTP. See
+	// https://github.com/ooni/probe/issues/2488 for additional
+	// context and pointers to the relevant measurements.
+	client := &http.Client{
+		Transport:     txpFactory(logger, reso),
+		CheckRedirect: nil,
+		Jar:           newCookieJar(),
+		Timeout:       0,
+	}
+
+	return netxlite.WrapHTTPClient(client)
+}
diff --git a/internal/cmd/oohelperd/handler_test.go b/internal/oohelperd/handler_test.go
similarity index 96%
rename from internal/cmd/oohelperd/handler_test.go
rename to internal/oohelperd/handler_test.go
index fbe1405765..48a284e237 100644
--- a/internal/cmd/oohelperd/handler_test.go
+++ b/internal/oohelperd/handler_test.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 import (
 	"context"
@@ -70,7 +70,7 @@ func TestHandlerWorkingAsIntended(t *testing.T) {
 		// measureFn optionally allows overriding the default
 		// value of the handler.Measure function
 		measureFn func(
-			ctx context.Context, config *handler, creq *model.THRequest) (*model.THResponse, error)
+			ctx context.Context, config *Handler, creq *model.THRequest) (*model.THResponse, error)
 
 		// reqBody is the request body to use
 		reqBody io.Reader
@@ -124,7 +124,7 @@ func TestHandlerWorkingAsIntended(t *testing.T) {
 		parseBody:       false,
 	}, {
 		name: "with reasonably good request",
-		measureFn: func(ctx context.Context, config *handler, creq *model.THRequest) (*model.THResponse, error) {
+		measureFn: func(ctx context.Context, config *Handler, creq *model.THRequest) (*model.THResponse, error) {
 			cresp := &model.THResponse{}
 			return cresp, nil
 		},
@@ -151,7 +151,7 @@ func TestHandlerWorkingAsIntended(t *testing.T) {
 	for _, expect := range expectations {
 		t.Run(expect.name, func(t *testing.T) {
 			// create handler and possibly override .Measure
-			handler := newHandler()
+			handler := NewHandler()
 			if expect.measureFn != nil {
 				handler.Measure = expect.measureFn
 			}
diff --git a/internal/cmd/oohelperd/http.go b/internal/oohelperd/http.go
similarity index 99%
rename from internal/cmd/oohelperd/http.go
rename to internal/oohelperd/http.go
index da7fae089a..a7331d985c 100644
--- a/internal/cmd/oohelperd/http.go
+++ b/internal/oohelperd/http.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 //
 // HTTP measurements
diff --git a/internal/cmd/oohelperd/http_test.go b/internal/oohelperd/http_test.go
similarity index 99%
rename from internal/cmd/oohelperd/http_test.go
rename to internal/oohelperd/http_test.go
index 41c967c1e0..66a36b40f4 100644
--- a/internal/cmd/oohelperd/http_test.go
+++ b/internal/oohelperd/http_test.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 import (
 	"context"
diff --git a/internal/cmd/oohelperd/ipinfo.go b/internal/oohelperd/ipinfo.go
similarity index 99%
rename from internal/cmd/oohelperd/ipinfo.go
rename to internal/oohelperd/ipinfo.go
index 24e5aaf6cc..23669f0afe 100644
--- a/internal/cmd/oohelperd/ipinfo.go
+++ b/internal/oohelperd/ipinfo.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 //
 // Generates IP and endpoint information.
diff --git a/internal/cmd/oohelperd/ipinfo_test.go b/internal/oohelperd/ipinfo_test.go
similarity index 99%
rename from internal/cmd/oohelperd/ipinfo_test.go
rename to internal/oohelperd/ipinfo_test.go
index 5515c73b07..99aa4a6dba 100644
--- a/internal/cmd/oohelperd/ipinfo_test.go
+++ b/internal/oohelperd/ipinfo_test.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 import (
 	"net/url"
diff --git a/internal/cmd/oohelperd/logging.go b/internal/oohelperd/logging.go
similarity index 98%
rename from internal/cmd/oohelperd/logging.go
rename to internal/oohelperd/logging.go
index cc140cafb3..dbb73bb3f6 100644
--- a/internal/cmd/oohelperd/logging.go
+++ b/internal/oohelperd/logging.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 //
 // Logging code
diff --git a/internal/cmd/oohelperd/logging_test.go b/internal/oohelperd/logging_test.go
similarity index 99%
rename from internal/cmd/oohelperd/logging_test.go
rename to internal/oohelperd/logging_test.go
index 2008659995..bfaf93a2f3 100644
--- a/internal/cmd/oohelperd/logging_test.go
+++ b/internal/oohelperd/logging_test.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 import (
 	"testing"
diff --git a/internal/cmd/oohelperd/measure.go b/internal/oohelperd/measure.go
similarity index 98%
rename from internal/cmd/oohelperd/measure.go
rename to internal/oohelperd/measure.go
index 8a1766b454..d47930aaf5 100644
--- a/internal/cmd/oohelperd/measure.go
+++ b/internal/oohelperd/measure.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 //
 // Top-level measurement algorithm
@@ -24,7 +24,7 @@ type (
 
 // measure performs the measurement described by the request and
 // returns the corresponding response or an error.
-func measure(ctx context.Context, config *handler, creq *ctrlRequest) (*ctrlResponse, error) {
+func measure(ctx context.Context, config *Handler, creq *ctrlRequest) (*ctrlResponse, error) {
 	// create indexed logger
 	logger := &prefixLogger{
 		indexstr: fmt.Sprintf("<#%d> ", config.Indexer.Add(1)),
diff --git a/internal/cmd/oohelperd/metrics.go b/internal/oohelperd/metrics.go
similarity index 98%
rename from internal/cmd/oohelperd/metrics.go
rename to internal/oohelperd/metrics.go
index f8468b25ce..37e99b6e01 100644
--- a/internal/cmd/oohelperd/metrics.go
+++ b/internal/oohelperd/metrics.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 //
 // Metrics definitions
diff --git a/internal/cmd/oohelperd/quic.go b/internal/oohelperd/quic.go
similarity index 99%
rename from internal/cmd/oohelperd/quic.go
rename to internal/oohelperd/quic.go
index 842ffc5064..471d1b423b 100644
--- a/internal/cmd/oohelperd/quic.go
+++ b/internal/oohelperd/quic.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 //
 // QUIC handshake measurements
diff --git a/internal/cmd/oohelperd/tcptls.go b/internal/oohelperd/tcptls.go
similarity index 99%
rename from internal/cmd/oohelperd/tcptls.go
rename to internal/oohelperd/tcptls.go
index ec62d14382..3a76130709 100644
--- a/internal/cmd/oohelperd/tcptls.go
+++ b/internal/oohelperd/tcptls.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 //
 // TCP connect (and optionally TLS handshake) measurements
diff --git a/internal/cmd/oohelperd/tcptls_test.go b/internal/oohelperd/tcptls_test.go
similarity index 98%
rename from internal/cmd/oohelperd/tcptls_test.go
rename to internal/oohelperd/tcptls_test.go
index a7f596a96c..6dac56cc19 100644
--- a/internal/cmd/oohelperd/tcptls_test.go
+++ b/internal/oohelperd/tcptls_test.go
@@ -1,4 +1,4 @@
-package main
+package oohelperd
 
 import (
 	"testing"