libnetwork: use strings.Cut() and minor refactor

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

libnetwork/etchosts/etchosts.go

@@ -75,20 +75,19 @@ func Build(path, IP, hostname, domainname string, extraContent []Record) error {
 
 	content := bytes.NewBuffer(nil)
 	if IP != "" {
-		//set main record
+		// set main record
 		var mainRec Record
 		mainRec.IP = IP
 		// User might have provided a FQDN in hostname or split it across hostname
 		// and domainname.  We want the FQDN and the bare hostname.
 		fqdn := hostname
 		if domainname != "" {
-			fqdn = fmt.Sprintf("%s.%s", fqdn, domainname)
+			fqdn += "." + domainname
 		}
-		parts := strings.SplitN(fqdn, ".", 2)
-		if len(parts) == 2 {
-			mainRec.Hosts = fmt.Sprintf("%s %s", fqdn, parts[0])
-		} else {
-			mainRec.Hosts = fqdn
+		mainRec.Hosts = fqdn
+
+		if hostName, _, ok := strings.Cut(fqdn, "."); ok {
+			mainRec.Hosts += " " + hostName
 		}
 		if _, err := mainRec.WriteTo(content); err != nil {
 			return err

libnetwork/netlabel/labels.go

@@ -30,7 +30,7 @@ const (
 	// DNSServers A list of DNS servers associated with the endpoint
 	DNSServers = Prefix + ".endpoint.dnsservers"
 
-	//EnableIPv6 constant represents enabling IPV6 at network level
+	// EnableIPv6 constant represents enabling IPV6 at network level
 	EnableIPv6 = Prefix + ".enable_ipv6"
 
 	// DriverMTU constant represents the MTU size for the network driver
@@ -106,27 +106,18 @@ func MakeKVClient(scope string) string {
 
 // Key extracts the key portion of the label
 func Key(label string) (key string) {
-	if kv := strings.SplitN(label, "=", 2); len(kv) > 0 {
-		key = kv[0]
-	}
-	return
+	key, _, _ = strings.Cut(label, "=")
+	return key
 }
 
 // Value extracts the value portion of the label
 func Value(label string) (value string) {
-	if kv := strings.SplitN(label, "=", 2); len(kv) > 1 {
-		value = kv[1]
-	}
-	return
+	_, value, _ = strings.Cut(label, "=")
+	return value
 }
 
 // KeyValue decomposes the label in the (key,value) pair
 func KeyValue(label string) (key string, value string) {
-	if kv := strings.SplitN(label, "=", 2); len(kv) > 0 {
-		key = kv[0]
-		if len(kv) > 1 {
-			value = kv[1]
-		}
-	}
-	return
+	key, value, _ = strings.Cut(label, "=")
+	return key, value
 }

libnetwork/sandbox_dns_unix.go

@@ -110,19 +110,18 @@ func (sb *sandbox) updateHostsFile(ifaceIPs []string) error {
 	// User might have provided a FQDN in hostname or split it across hostname
 	// and domainname.  We want the FQDN and the bare hostname.
 	fqdn := sb.config.hostName
-	mhost := sb.config.hostName
 	if sb.config.domainName != "" {
-		fqdn = fmt.Sprintf("%s.%s", fqdn, sb.config.domainName)
+		fqdn += "." + sb.config.domainName
 	}
+	hosts := fqdn
 
-	parts := strings.SplitN(fqdn, ".", 2)
-	if len(parts) == 2 {
-		mhost = fmt.Sprintf("%s %s", fqdn, parts[0])
+	if hostName, _, ok := strings.Cut(fqdn, "."); ok {
+		hosts += " " + hostName
 	}
 
 	var extraContent []etchosts.Record
 	for _, ip := range ifaceIPs {
-		extraContent = append(extraContent, etchosts.Record{Hosts: mhost, IP: ip})
+		extraContent = append(extraContent, etchosts.Record{Hosts: hosts, IP: ip})
 	}
 
 	sb.addHostsEntries(extraContent)