fix(webconnectivity@v0.5): fetch HTTP only using system-resolver addrs (#935)

While there, change the emoji logger to emit whitespace on info logs. This makes warnings stand out even more.

Closes https://github.com/ooni/probe/issues/2258

internal/experiment/webconnectivity/control.go

@@ -23,11 +23,11 @@ type EndpointMeasurementsStarter interface {
 	// nonblocking read fails. Hence, you must create a [sema] channel with buffer equal
 	// to N and N elements inside it to allow N flows to perform HTTP measurements. Passing
 	// a nil [sema] causes no flow to attempt HTTP measurements.
-	startCleartextFlowsWithSema(ctx context.Context, sema <-chan any, addresses []string)
+	startCleartextFlowsWithSema(ctx context.Context, sema <-chan any, addresses []DNSEntry)
 
 	// startSecureFlowsWithSema starts a TCP+TLS measurement flow for each IP addr. See
 	// the docs of startCleartextFlowsWithSema for more info on the [sema] arg.
-	startSecureFlowsWithSema(ctx context.Context, sema <-chan any, addresses []string)
+	startSecureFlowsWithSema(ctx context.Context, sema <-chan any, addresses []DNSEntry)
 }
 
 // Control issues a Control request and saves the results
@@ -157,12 +157,22 @@ func (c *Control) maybeStartExtraMeasurements(ctx context.Context, thAddrs []str
 	}
 
 	// obtain the TH-only addresses
-	var thOnly []string
+	var thOnlyAddrs []string
 	for addr, flags := range mapping {
 		if (flags & inProbe) != 0 {
 			continue // discovered by the probe => already tested
 		}
-		thOnly = append(thOnly, addr)
+		thOnlyAddrs = append(thOnlyAddrs, addr)
+	}
+
+	c.Logger.Infof("measuring additional addrs from TH: %+v", thOnlyAddrs)
+
+	var thOnly []DNSEntry
+	for _, addr := range thOnlyAddrs {
+		thOnly = append(thOnly, DNSEntry{
+			Addr:  addr,
+			Flags: 0, // neither system, nor udp, nor doh
+		})
 	}
 
 	// Start extra measurements for TH-only addresses. Because we already

internal/experiment/webconnectivity/dnscache.go

@@ -2,6 +2,26 @@ package webconnectivity
 
 import "sync"
 
+// DNSEntry is an entry in the DNS cache.
+type DNSEntry struct {
+	// Addr is the cached address
+	Addr string
+
+	// Flags contains flags
+	Flags int64
+}
+
+const (
+	// DNSAddrFlagSystemResolver means we discovered this addr using the system resolver.
+	DNSAddrFlagSystemResolver = 1 << iota
+
+	// DNSAddrFlagUDP means we discovered this addr using the UDP resolver.
+	DNSAddrFlagUDP
+
+	// DNSAddrFlagHTTPS means we discovered this addr using the DNS-over-HTTPS resolver.
+	DNSAddrFlagHTTPS
+)
+
 // DNSCache wraps a model.Resolver to provide DNS caching.
 //
 // The zero value is invalid; please, use NewDNSCache to construct.
@@ -10,11 +30,11 @@ type DNSCache struct {
 	mu *sync.Mutex
 
 	// values contains already resolved values.
-	values map[string][]string
+	values map[string][]DNSEntry
 }
 
 // Get gets values from the cache
-func (c *DNSCache) Get(domain string) ([]string, bool) {
+func (c *DNSCache) Get(domain string) ([]DNSEntry, bool) {
 	c.mu.Lock()
 	values, found := c.values[domain]
 	c.mu.Unlock()
@@ -22,7 +42,7 @@ func (c *DNSCache) Get(domain string) ([]string, bool) {
 }
 
 // Set inserts into the cache
-func (c *DNSCache) Set(domain string, values []string) {
+func (c *DNSCache) Set(domain string, values []DNSEntry) {
 	c.mu.Lock()
 	c.values[domain] = values
 	c.mu.Unlock()
@@ -32,6 +52,6 @@ func (c *DNSCache) Set(domain string, values []string) {
 func NewDNSCache() *DNSCache {
 	return &DNSCache{
 		mu:     &sync.Mutex{},
-		values: map[string][]string{},
+		values: map[string][]DNSEntry{},
 	}
 }

internal/experiment/webconnectivity/dnsresolvers.go

@@ -82,7 +82,7 @@ func (t *DNSResolvers) Start(ctx context.Context) {
 }
 
 // run performs a DNS lookup and returns the looked up addrs
-func (t *DNSResolvers) run(parentCtx context.Context) []string {
+func (t *DNSResolvers) run(parentCtx context.Context) []DNSEntry {
 	// create output channels for the lookup
 	systemOut := make(chan []string)
 	udpOut := make(chan []string)
@@ -117,39 +117,42 @@ func (t *DNSResolvers) run(parentCtx context.Context) []string {
 	})
 
 	// merge the resolved IP addresses
-	merged := map[string]bool{}
+	merged := map[string]*DNSEntry{}
 	for _, addr := range systemAddrs {
-		merged[addr] = true
+		if _, found := merged[addr]; !found {
+			merged[addr] = &DNSEntry{}
+		}
+		merged[addr].Addr = addr
+		merged[addr].Flags |= DNSAddrFlagSystemResolver
 	}
 	for _, addr := range udpAddrs {
-		merged[addr] = true
+		if _, found := merged[addr]; !found {
+			merged[addr] = &DNSEntry{}
+		}
+		merged[addr].Addr = addr
+		merged[addr].Flags |= DNSAddrFlagUDP
 	}
 	for _, addr := range httpsAddrs {
-		merged[addr] = true
-	}
-
-	// rearrange addresses to have IPv4 first
-	sorted := []string{}
-	for addr := range merged {
-		if v6, err := netxlite.IsIPv6(addr); err == nil && !v6 {
-			sorted = append(sorted, addr)
+		if _, found := merged[addr]; !found {
+			merged[addr] = &DNSEntry{}
 		}
+		merged[addr].Addr = addr
+		merged[addr].Flags |= DNSAddrFlagHTTPS
 	}
-	for addr := range merged {
-		if v6, err := netxlite.IsIPv6(addr); err == nil && v6 {
-			sorted = append(sorted, addr)
-		}
+	// implementation note: we don't remove bogons because accessing
+	// them can lead us to discover block pages
+	var entries []DNSEntry
+	for _, entry := range merged {
+		entries = append(entries, *entry)
 	}
 
-	// TODO(bassosimone): remove bogons
-
-	return sorted
+	return entries
 }
 
 // Run runs this task in the current goroutine.
 func (t *DNSResolvers) Run(parentCtx context.Context) {
 	var (
-		addresses []string
+		addresses []DNSEntry
 		found     bool
 	)
 
@@ -162,9 +165,11 @@ func (t *DNSResolvers) Run(parentCtx context.Context) {
 
 		// insert the addresses we just looked us into the cache
 		t.DNSCache.Set(t.Domain, addresses)
-	}
 
-	log.Infof("using resolved addrs: %+v", addresses)
+		log.Infof("using resolved addrs: %+v", addresses)
+	} else {
+		log.Infof("using previously-cached addrs: %+v", addresses)
+	}
 
 	// fan out a number of child async tasks to use the IP addrs
 	t.startCleartextFlows(parentCtx, addresses)
@@ -409,14 +414,14 @@ func (t *DNSResolvers) dohSplitQueries(
 }
 
 // startCleartextFlows starts a TCP measurement flow for each IP addr.
-func (t *DNSResolvers) startCleartextFlows(ctx context.Context, addresses []string) {
+func (t *DNSResolvers) startCleartextFlows(ctx context.Context, addresses []DNSEntry) {
 	sema := make(chan any, 1)
 	sema <- true // allow a single flow to fetch the HTTP body
 	t.startCleartextFlowsWithSema(ctx, sema, addresses)
 }
 
 // startCleartextFlowsWithSema implements EndpointMeasurementsStarter.
-func (t *DNSResolvers) startCleartextFlowsWithSema(ctx context.Context, sema <-chan any, addresses []string) {
+func (t *DNSResolvers) startCleartextFlowsWithSema(ctx context.Context, sema <-chan any, addresses []DNSEntry) {
 	if t.URL.Scheme != "http" {
 		// Do not bother with measuring HTTP when the user
 		// has asked us to measure an HTTPS URL.
@@ -427,12 +432,16 @@ func (t *DNSResolvers) startCleartextFlowsWithSema(ctx context.Context, sema <-c
 		port = urlPort
 	}
 	for _, addr := range addresses {
+		maybeNilSema := sema
+		if (addr.Flags & DNSAddrFlagSystemResolver) == 0 {
+			maybeNilSema = nil // see https://github.com/ooni/probe/issues/2258
+		}
 		task := &CleartextFlow{
-			Address:         net.JoinHostPort(addr, port),
+			Address:         net.JoinHostPort(addr.Addr, port),
 			DNSCache:        t.DNSCache,
 			IDGenerator:     t.IDGenerator,
 			Logger:          t.Logger,
-			Sema:            sema,
+			Sema:            maybeNilSema,
 			TestKeys:        t.TestKeys,
 			ZeroTime:        t.ZeroTime,
 			WaitGroup:       t.WaitGroup,
@@ -449,7 +458,7 @@ func (t *DNSResolvers) startCleartextFlowsWithSema(ctx context.Context, sema <-c
 }
 
 // startSecureFlows starts a TCP+TLS measurement flow for each IP addr.
-func (t *DNSResolvers) startSecureFlows(ctx context.Context, addresses []string) {
+func (t *DNSResolvers) startSecureFlows(ctx context.Context, addresses []DNSEntry) {
 	sema := make(chan any, 1)
 	if t.URL.Scheme == "https" {
 		// Allows just a single worker to fetch the response body but do that
@@ -461,7 +470,7 @@ func (t *DNSResolvers) startSecureFlows(ctx context.Context, addresses []string)
 }
 
 // startSecureFlowsWithSema implements EndpointMeasurementsStarter.
-func (t *DNSResolvers) startSecureFlowsWithSema(ctx context.Context, sema <-chan any, addresses []string) {
+func (t *DNSResolvers) startSecureFlowsWithSema(ctx context.Context, sema <-chan any, addresses []DNSEntry) {
 	port := "443"
 	if urlPort := t.URL.Port(); urlPort != "" {
 		if t.URL.Scheme != "https" {
@@ -472,12 +481,16 @@ func (t *DNSResolvers) startSecureFlowsWithSema(ctx context.Context, sema <-chan
 		port = urlPort
 	}
 	for _, addr := range addresses {
+		maybeNilSema := sema
+		if (addr.Flags & DNSAddrFlagSystemResolver) == 0 {
+			maybeNilSema = nil // see https://github.com/ooni/probe/issues/2258
+		}
 		task := &SecureFlow{
-			Address:         net.JoinHostPort(addr, port),
+			Address:         net.JoinHostPort(addr.Addr, port),
 			DNSCache:        t.DNSCache,
 			IDGenerator:     t.IDGenerator,
 			Logger:          t.Logger,
-			Sema:            sema,
+			Sema:            maybeNilSema,
 			TestKeys:        t.TestKeys,
 			ZeroTime:        t.ZeroTime,
 			WaitGroup:       t.WaitGroup,
@@ -496,10 +509,16 @@ func (t *DNSResolvers) startSecureFlowsWithSema(ctx context.Context, sema <-chan
 }
 
 // maybeStartControlFlow starts the control flow iff .Session and .THAddr are set.
-func (t *DNSResolvers) maybeStartControlFlow(ctx context.Context, addresses []string) {
+func (t *DNSResolvers) maybeStartControlFlow(ctx context.Context, addresses []DNSEntry) {
+	// note: for subsequent requests we don't set .Session and .THAddr hence
+	// we are not going to query the test helper more than once
 	if t.Session != nil && t.THAddr != "" {
+		var addrs []string
+		for _, addr := range addresses {
+			addrs = append(addrs, addr.Addr)
+		}
 		ctrl := &Control{
-			Addresses:                addresses,
+			Addresses:                addrs,
 			ExtraMeasurementsStarter: t, // allows starting follow-up measurement flows
 			Logger:                   t.Logger,
 			TestKeys:                 t.TestKeys,

internal/experiment/webconnectivity/measurer.go

@@ -36,7 +36,7 @@ func (m *Measurer) ExperimentName() string {
 
 // ExperimentVersion implements model.ExperimentMeasurer.
 func (m *Measurer) ExperimentVersion() string {
-	return "0.5.3"
+	return "0.5.4"
 }
 
 // Run implements model.ExperimentMeasurer.

internal/logx/logx.go

@@ -45,7 +45,7 @@ func (h *Handler) HandleLog(e *log.Entry) (err error) {
 		case log.DebugLevel:
 			level = "🧐"
 		case log.InfoLevel:
-			level = "🗒️"
+			level = "  "
 		case log.WarnLevel:
 			level = "🔥"
 		default:

internal/logx/logx_test.go

@@ -74,7 +74,7 @@ func TestLogHandlerHandleLog(t *testing.T) {
 		Name:           "info level with emoji",
 		Emoji:          true,
 		Level:          log.InfoLevel,
-		ExpectSeverity: "🗒️",
+		ExpectSeverity: "  ",
 	}, {
 		Name:           "warn level with emoji",
 		Emoji:          true,