chore(gateway): idiomatic loop logic

core/corehttp/hostname.go

@@ -211,19 +211,24 @@ func knownSubdomainDetails(hostname string, knownGateways map[string]config.Gate
 	// Example: given "dist.ipfs.io.ipns.dweb.link":
 	// 1. Lookup "link" TLD in knownGateways: negative
 	// 2. Lookup "dweb.link" in knownGateways: positive
-	for i := range labels {
-		start := len(labels) - 1 - i
-		fqdn := strings.Join(labels[start:], ".")
+	//
+	// Stops when we have 2 or fewer labels left as we need at least a
+	// rootId and a namespace.
+	for i := len(labels) - 1; i >= 2; i-- {
+		fqdn := strings.Join(labels[i:], ".")
 		gw, ok := isKnownHostname(fqdn, knownGateways)
-		// Are there at least two labels left? (ns, rootID)
-		if ok && start > 1 {
-			ns := labels[start-1]
-			if isSubdomainNamespace(ns) {
-				// Merge remaining labels (could be a FQDN with DNSLink)
-				rootID := strings.Join(labels[:start-1], ".")
-				return gw, fqdn, ns, rootID, true
-			}
+		if !ok {
+			continue
+		}
+
+		ns := labels[i-1]
+		if !isSubdomainNamespace(ns) {
+			break
 		}
+
+		// Merge remaining labels (could be a FQDN with DNSLink)
+		rootID := strings.Join(labels[:i-1], ".")
+		return gw, fqdn, ns, rootID, true
 	}
 	// not a known subdomain gateway
 	return gw, "", "", "", false