Address feedback and linting errors

Author: jsumners

.golangci.toml

@@ -125,7 +125,7 @@
     text = "(tlsFeatureExtensionOID|ocspMustStapleFeature) is a global variable"
   [[issues.exclude-rules]]
     path = "challenge/dns01/nameserver.go"
-    text = "(defaultNameservers|recursiveNameservers|fqdnSoaCache|muFqdnSoaCache) is a global variable"
+    text = "(defaultNameservers|recursiveNameservers|currentNetworkStack|fqdnSoaCache|muFqdnSoaCache) is a global variable"
   [[issues.exclude-rules]]
     path = "challenge/dns01/nameserver_.+.go"
     text = "dnsTimeout is a global variable"

challenge/dns01/nameserver.go

@@ -26,9 +26,17 @@ var defaultNameservers = []string{
 // recursiveNameservers are used to pre-check DNS propagation.
 var recursiveNameservers = getNameservers(defaultResolvConf, defaultNameservers)
 
-// networkStack is used to define which IP stack will be used. The default is
-// both IPv4 and IPv6. Set to "ipv4" for IPv4 only, and "ipv6" for IPv6 only.
-var networkStack = "both"
+type networkStack int
+
+const (
+	defaultNetworkStack networkStack = iota
+	ipv4Only
+	ipv6Only
+)
+
+// currentNetworkStack is used to define which IP stack will be used. The default is
+// both IPv4 and IPv6. Set to ipv4Only or ipv6Only to select either version.
+var currentNetworkStack = defaultNetworkStack
 
 // soaCacheEntry holds a cached SOA record (only selected fields).
 type soaCacheEntry struct {
@@ -74,10 +82,15 @@ func AddRecursiveNameservers(nameservers []string) ChallengeOption {
 // SetNetworkStack defines the IP stack that will be used for DNS queries.
 // Accepts "both", "ipv4", or "ipv6".
 func SetNetworkStack(network string) {
-	if network == "ipv4" || network == "ipv6" {
-		networkStack = network
-	} else {
-		networkStack = "both"
+	switch network {
+	case "ipv4":
+		currentNetworkStack = ipv4Only
+
+	case "ipv6":
+		currentNetworkStack = ipv6Only
+
+	default:
+		currentNetworkStack = defaultNetworkStack
 	}
 }
 
@@ -270,10 +283,10 @@ func getNetwork(proto string) string {
 	// the [net.Dialer] (https://github.com/miekg/dns/blob/fe20d5d/client.go#L119-L141).
 	// And the [net.Dialer] accepts strings such as "udp4" or "tcp6"
 	// (https://cs.opensource.google/go/go/+/refs/tags/go1.18.9:src/net/dial.go;l=167-182).
-	if networkStack == "ipv4" {
+	if currentNetworkStack == ipv4Only {
 		return proto + "4"
 	}
-	if networkStack == "ipv6" {
+	if currentNetworkStack == ipv6Only {
 		return proto + "6"
 	}
 	return proto

cmd/flags.go

@@ -9,14 +9,14 @@ import (
 func CreateFlags(defaultPath string) []cli.Flag {
 	return []cli.Flag{
 		&cli.BoolFlag{
-			Name: "ipv4only",
+			Name:    "ipv4only",
 			Aliases: []string{"4"},
-			Usage: "Use IPv4 only. This flag is ignored if ipv6only is also specified.",
+			Usage:   "Use IPv4 only. This flag is ignored if ipv6only is also specified.",
 		},
 		&cli.BoolFlag{
-			Name: "ipv6only",
+			Name:    "ipv6only",
 			Aliases: []string{"6"},
-			Usage: "Use IPv6 only. This flag is ignored if ipv4only is also specified.",
+			Usage:   "Use IPv6 only. This flag is ignored if ipv4only is also specified.",
 		},
 		&cli.StringSliceFlag{
 			Name:    "domains",

cmd/setup_challenges.go

@@ -111,13 +111,16 @@ func setupDNS(ctx *cli.Context, client *lego.Client) {
 		log.Fatal(err)
 	}
 
-	if ctx.IsSet("ipv4only") && ctx.IsSet("ipv6only") {
+	switch {
+	case ctx.IsSet("ipv4only") && ctx.IsSet("ipv6only"):
 		// If both flags are set then it's as good as not providing either flag,
 		// so we default to the OS choice.
 		dns01.SetNetworkStack("both")
-	} else if ctx.IsSet("ipv4only") {
+
+	case ctx.IsSet("ipv4only"):
 		dns01.SetNetworkStack("ipv4")
-	} else if ctx.IsSet("ipv6only") {
+
+	case ctx.IsSet("ipv6only"):
 		dns01.SetNetworkStack("ipv6")
 	}