feat: Do not send metrics if the client used DNT or GPC

cmd/rio/main.go

@@ -71,6 +71,8 @@ func handleSubdomain(ctx *context.GlobalContext, domain, cname, path string, req
 		Path:      path,
 		Referrer:  req.Header.Get("Referer"),
 		UserAgent: req.Header.Get("User-Agent"),
+		DNT:       req.Header.Get("DNT"),
+		GPC:       req.Header.Get("Sec-GPC"),
 		Writer:    w,
 		Global:    ctx,
 	}

internal/context/context.go

@@ -36,6 +36,8 @@ type Context struct {
 	// HTTP Stuff
 	Referrer  string
 	UserAgent string
+	DNT       string
+	GPC       string
 	Writer    http.ResponseWriter
 
 	// Pointer to the global context

internal/metrics/metrics.go

@@ -16,12 +16,18 @@ type MetricConfig struct {
 	Enabled       bool
 }
 
-// Checks if we should send a metric ping to Loki based on the served path.
+// Checks if we should send a metric ping to page-metrics based on the served path.
-func (c *MetricConfig) ShouldSendMetrics(path, userAgent string) bool {
+func (c *MetricConfig) ShouldSendMetrics(path, userAgent, dnt, gpc string) bool {
 	if !strings.HasSuffix(path, ".html") || !c.Enabled {
 		return false
 	}
 
+	// Ignore requests where the user have set "Do-Not-Track" or "Do-Not-Sell-My-Data", even though
+	// there is no user data and we're not selling it.
+	if dnt == "1" || gpc == "1" {
+		return false
+	}
+
 	// Filter out bots
 	for _, pattern := range *c.BotUserAgents {
 		if pattern.MatchString(userAgent) {

internal/metrics/metrics_test.go

@@ -14,11 +14,19 @@ func TestShouldPing(t *testing.T) {
 		},
 	}
 
-	if cfg.ShouldSendMetrics("/index.html", "random-bot/v23.5") {
+	if cfg.ShouldSendMetrics("/index.html", "random-bot/v23.5", "", "") {
 		t.Fatalf("Accepted bot user-agent")
 	}
 
-	if !cfg.ShouldSendMetrics("/index.html", "Firefox/...") {
+	if !cfg.ShouldSendMetrics("/index.html", "Firefox/...", "", "") {
 		t.Fatalf("Rejected real user-agent")
 	}
+
+	if cfg.ShouldSendMetrics("/index.html", "Firefox/...", "1", "") {
+		t.Fatalf("Ignored DNT")
+	}
+
+	if cfg.ShouldSendMetrics("/index.html", "Firefox/...", "", "1") {
+		t.Fatalf("Ignored GPC")
+	}
 }

internal/pages/pages.go

@@ -124,7 +124,7 @@ func ServeFile(context *context.Context) {
 	context.Writer.Write(content)
 
 	// Tell Loki about if, if desired
-	if context.Global.MetricConfig.ShouldSendMetrics(path, context.UserAgent) {
+	if context.Global.MetricConfig.ShouldSendMetrics(path, context.UserAgent, context.DNT, context.GPC) {
 		context.Global.MetricConfig.SendMetricPing(context.Domain, path, context.Referrer)
 	}
 }