fix(all): introduce and use iox.ReadAllContext (#379)

* fix(all): introduce and use iox.ReadAllContext

This improvement over the ioutil.ReadAll utility returns early
if the context expires. This enables us to unblock stuck code in
case there's censorship confounding the TCP stack.

See https://github.com/ooni/probe/issues/1417.

Compared to the functionality postulated in the above mentioned
issue, I choose to be more generic and separate limiting the
maximum body size (not implemented here) from using the context
to return early when reading a body (or any other reader).

After implementing iox.ReadAllContext, I made sure we always
use it everywhere in the tree instead of ioutil.ReadAll.

This includes many parts of the codebase where in theory we don't
need iox.ReadAllContext. Though, changing all the places makes
checking whether we're not using ioutil.ReadAll where we should
not be using it easy: `git grep` should return no lines.

* Update internal/iox/iox_test.go

* fix(ndt7): treat context errors as non-errors

The rationale is explained by the comment documenting reduceErr.

* Update internal/engine/experiment/ndt7/download.go

internal/engine/experiment/dash/collect.go

@@ -16,7 +16,7 @@ type collectDeps interface {
 	JSONMarshal(v interface{}) ([]byte, error)
 	Logger() model.Logger
 	NewHTTPRequest(method string, url string, body io.Reader) (*http.Request, error)
-	ReadAll(r io.Reader) ([]byte, error)
+	ReadAllContext(ctx context.Context, r io.Reader) ([]byte, error)
 	Scheme() string
 	UserAgent() string
 }
@@ -47,7 +47,7 @@ func collect(ctx context.Context, fqdn, authorization string,
 		return errHTTPRequestFailed
 	}
 	defer resp.Body.Close()
-	data, err = deps.ReadAll(resp.Body)
+	data, err = deps.ReadAllContext(ctx, resp.Body)
 	if err != nil {
 		return err
 	}

internal/engine/experiment/dash/dash.go

@@ -9,7 +9,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"runtime"
 	"time"
@@ -20,6 +19,7 @@ import (
 	"github.com/ooni/probe-cli/v3/internal/engine/netx/errorx"
 	"github.com/ooni/probe-cli/v3/internal/engine/netx/trace"
 	"github.com/ooni/probe-cli/v3/internal/humanize"
+	"github.com/ooni/probe-cli/v3/internal/iox"
 )
 
 const (
@@ -86,8 +86,8 @@ func (r runner) NewHTTPRequest(meth, url string, body io.Reader) (*http.Request,
 	return http.NewRequest(meth, url, body)
 }
 
-func (r runner) ReadAll(reader io.Reader) ([]byte, error) {
-	return ioutil.ReadAll(reader)
+func (r runner) ReadAllContext(ctx context.Context, reader io.Reader) ([]byte, error) {
+	return iox.ReadAllContext(ctx, reader)
 }
 
 func (r runner) Scheme() string {
@@ -179,7 +179,7 @@ func (r runner) measure(
 		current.ConnectTime = connectTime
 		r.tk.ReceiverData = append(r.tk.ReceiverData, current)
 		total += current.Received
-		avgspeed := 8 * float64(total) / time.Now().Sub(begin).Seconds()
+		avgspeed := 8 * float64(total) / time.Since(begin).Seconds()
 		percentage := float64(current.Iteration) / float64(numIterations)
 		message := fmt.Sprintf("streaming: speed: %s", humanize.SI(avgspeed, "bit/s"))
 		r.callbacks.OnProgress(percentage, message)

internal/engine/experiment/dash/download.go

@@ -12,7 +12,7 @@ import (
 type downloadDeps interface {
 	HTTPClient() *http.Client
 	NewHTTPRequest(method string, url string, body io.Reader) (*http.Request, error)
-	ReadAll(r io.Reader) ([]byte, error)
+	ReadAllContext(ctx context.Context, r io.Reader) ([]byte, error)
 	Scheme() string
 	UserAgent() string
 }
@@ -57,7 +57,7 @@ func download(ctx context.Context, config downloadConfig) (downloadResult, error
 		return result, errHTTPRequestFailed
 	}
 	defer resp.Body.Close()
-	data, err := config.deps.ReadAll(resp.Body)
+	data, err := config.deps.ReadAllContext(ctx, resp.Body)
 	if err != nil {
 		return result, err
 	}
@@ -66,7 +66,7 @@ func download(ctx context.Context, config downloadConfig) (downloadResult, error
 	// turns out that Neubot and MK do the same. So, we do what they do. At
 	// the same time, we are currently not able to include the overhead that
 	// is caused by HTTP headers etc. So, we're a bit less precise.
-	result.elapsed = time.Now().Sub(savedTicks).Seconds()
+	result.elapsed = time.Since(savedTicks).Seconds()
 	result.received = int64(len(data))
 	result.requestTicks = savedTicks.Sub(config.begin).Seconds()
 	result.timestamp = time.Now().Unix()

internal/engine/experiment/dash/fake_test.go

@@ -1,6 +1,7 @@
 package dash
 
 import (
+	"context"
 	"io"
 	"net/http"
 	"time"
@@ -36,7 +37,7 @@ func (d FakeDeps) NewHTTPRequest(
 	return d.newHTTPRequestResult, d.newHTTPRequestErr
 }
 
-func (d FakeDeps) ReadAll(r io.Reader) ([]byte, error) {
+func (d FakeDeps) ReadAllContext(ctx context.Context, r io.Reader) ([]byte, error) {
 	return d.readAllResult, d.readAllErr
 }
 

internal/engine/experiment/dash/negotiate.go

@@ -16,7 +16,7 @@ type negotiateDeps interface {
 	JSONMarshal(v interface{}) ([]byte, error)
 	Logger() model.Logger
 	NewHTTPRequest(method string, url string, body io.Reader) (*http.Request, error)
-	ReadAll(r io.Reader) ([]byte, error)
+	ReadAllContext(ctx context.Context, r io.Reader) ([]byte, error)
 	Scheme() string
 	UserAgent() string
 }
@@ -48,7 +48,7 @@ func negotiate(
 		return negotiateResp, errHTTPRequestFailed
 	}
 	defer resp.Body.Close()
-	data, err = deps.ReadAll(resp.Body)
+	data, err = deps.ReadAllContext(ctx, resp.Body)
 	if err != nil {
 		return negotiateResp, err
 	}

internal/engine/experiment/dash/spec.go

@@ -1,12 +1,6 @@
 package dash
 
 const (
-	// currentServerSchemaVersion is the version of the server schema that
-	// will be adopted by this implementation. Version 3 is the one that is
-	// Neubot uses. We needed to bump the version because Web100 is not on
-	// M-Lab anymore and hence we need to make a breaking change.
-	currentServerSchemaVersion = 4
-
 	// negotiatePath is the URL path used to negotiate
 	negotiatePath = "/negotiate/dash"