Overhaul config, strip out other subcommands, tidy up, add pre-commit with golangci-lint

.gitignore

@@ -1,4 +1,5 @@
-/.ztdns.toml
+ztdns.yml
+ztdns.toml
 
 .vscode/
 

.golangci.yml

@@ -0,0 +1,4 @@
+linters-settings:
+  errcheck:
+    # fmt is default
+    ignore: fmt:.*,github.com/spf13/viper:BindPFlag

.pre-commit-config.yaml

@@ -0,0 +1,16 @@
+repos:
+  - repo: https://github.com/golangci/golangci-lint
+    rev: v1.19.1
+    hooks:
+      - id: golangci-lint
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v2.2.3
+    hooks:
+      - id: check-byte-order-marker
+      - id: check-case-conflict
+      - id: check-executables-have-shebangs
+      - id: check-merge-conflict
+      - id: check-symlinks
+      - id: check-yaml
+      - id: end-of-file-fixer
+      - id: trailing-whitespace

.ztdns.toml.example

@@ -1,29 +0,0 @@
-# Configuration file for ztDNS
-
-suffix = "zt"
-port = 53
-interface = "zt0"
-
-# Number of minutes to wait before updating the DNS database again (Default: 30)
-DBRefresh = 30
-
-# This section contains information related to your ZeroTier config
-[ZT]
-# API is used to contact the ZeroTier controller API service.
-API = ""
-# URL is the url of the ZeroTier controller API
-URL = "https://my.zerotier.com/api"
-
-# This section contains one or more ZeroTier networks
-# Format is: domain = "NetworkID"
-# Domain does not have to match the configured network name
-[Networks]
-
-# Match section contains zero or more match pairs to create Round robin dns
-# Format is: "regexp to match hosts" = "hostname"
-# Example 1:
-#   "k8s-node-\w" = "k8s-nodes"
-#   From nodes with names k8s-node-23refw, k8s-node-09sf8g
-#   will create round robin record k8s-nodes
-[RoundRobin]
-

cmd/listinterfaces.go

@@ -1,42 +0,0 @@
-// Copyright © 2017 uxbh
-
-package cmd
-
-import (
-	"fmt"
-	"net"
-
-	"github.com/spf13/cobra"
-)
-
-// listinterfacesCmd represents the listinterfaces command
-var listinterfacesCmd = &cobra.Command{
-	Use:   "listinterfaces",
-	Short: "List network interfaces",
-	Long: `List Interfaces (ztdns listinterfaces) lists the available network interfaces
-to start the server on.`,
-	Run: func(cmd *cobra.Command, args []string) {
-		// Get a list of interfaces from net
-		ints, err := net.Interfaces()
-		if err != nil {
-			fmt.Printf("error getting interfaces: %s", err)
-		}
-		for i, n := range ints {
-			fmt.Printf("%d: %v\n", i, n.Name)
-			// Get a list of ip address on the interface
-			addrs, _ := n.Addrs()
-			for i, a := range addrs {
-				ip, _, err := net.ParseCIDR(a.String())
-				if err != nil {
-					continue
-				}
-				fmt.Printf("\t%d: %s\n", i, ip)
-			}
-		}
-
-	},
-}
-
-func init() {
-	RootCmd.AddCommand(listinterfacesCmd)
-}

cmd/mkconfig.go

@@ -1,68 +0,0 @@
-// Copyright © 2017 uxbh
-
-package cmd
-
-import (
-	"os"
-
-	log "github.com/sirupsen/logrus"
-	"github.com/spf13/cobra"
-)
-
-// mkconfigCmd represents the mkconfig command
-var mkconfigCmd = &cobra.Command{
-	Use:   "mkconfig",
-	Short: "Make a new config file",
-	Long: `mkconfig (ztdns mkconfig) creates a new configuation file.
-If you do not specify a filename the default is ./.ztdns.toml
-
-Example: ztdns mkconfig [.filename.toml]`,
-	Run: func(cmd *cobra.Command, args []string) {
-		filename := "./.ztdns.toml"
-		if len(args) > 0 {
-			filename = args[0]
-		}
-		if _, err := os.Stat(filename); os.IsNotExist(err) {
-			log.Printf("Creating new config file in %s", filename)
-			file, err := os.Create(filename)
-			if err != nil {
-				log.Fatalf("Could not create file: %s", err.Error())
-			}
-			defer file.Close()
-			file.WriteString(`# Configuration file for ztDNS
-
-suffix = "zt"
-port = 53
-interface = "zt0"
-
-# Number of minutes to wait before updating the DNS database again (Default: 30)
-DBRefresh = 30
-
-# This section contains information related to your ZeroTier config
-[ZT]
-# API is used to contact the ZeroTier controller API service.
-API = ""
-# URL is the url of the ZeroTier controller API
-URL = "https://my.zerotier.com/api"
-
-# This section contains one or more ZeroTier networks
-# Format is: domain = "NetworkID"
-# Domain does not have to match the configured network name
-[Networks]
-
-# Match section contains zero or more match pairs to create Round robin dns
-# Format is: "regexp to match hosts" = "hostname"
-# Example 1:
-#   "k8s-node-\w" = "k8s-nodes"
-#   From nodes with names k8s-node-23refw, k8s-node-09sf8g
-#   will create round robin record k8s-nodes
-[RoundRobin]
-
-`)
-		}
-	},
-}
-
-func init() {
-	RootCmd.AddCommand(mkconfigCmd)
-}

cmd/root.go

@@ -1,10 +1,12 @@
 // Copyright © 2017 uxbh
 
+// Package cmd implments the ztdns command-line interface.
 package cmd
 
 import (
 	"fmt"
 	"os"
+	"strings"
 
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
@@ -12,7 +14,6 @@ import (
 
 var cfgFile string
 
-// RootCmd represents the base command when called without any subcommands
 var RootCmd = &cobra.Command{
 	Use:   "ztdns",
 	Short: "Zerotier DNS Server",
@@ -21,8 +22,6 @@ This application will serve DNS requests for the members of a ZeroTier
 network for both A (IPv4) and AAAA (IPv6) requests`,
 }
 
-// Execute adds all child commands to the root command sets flags appropriately.
-// This is called by main.main(). It only needs to happen once to the rootCmd.
 func Execute() {
 	if err := RootCmd.Execute(); err != nil {
 		fmt.Println(err)
@@ -32,28 +31,28 @@ func Execute() {
 
 func init() {
 	cobra.OnInitialize(initConfig)
-
 	RootCmd.PersistentFlags().Bool("debug", false, "enable debug messages")
+	RootCmd.PersistentFlags().StringVar(&cfgFile, "config", "", "config file (default is ztdns.yml)")
 	viper.BindPFlag("debug", RootCmd.PersistentFlags().Lookup("debug"))
 
-	RootCmd.PersistentFlags().StringVar(&cfgFile, "config", "", "config file (default is $HOME/.ztdns.toml)")
-
 }
 
-// initConfig reads in config file and ENV variables if set.
 func initConfig() {
-	if cfgFile != "" { // enable ability to specify config file via flag
+	if cfgFile != "" {
+		// Use specified config file
 		viper.SetConfigFile(cfgFile)
 	} else {
-		viper.SetConfigName(".ztdns") // name of config file (without extension)
-		viper.AddConfigPath(".")      // adding current directory as first search path
-		viper.AddConfigPath("$HOME")  // adding home directory as second search path
+		// Find config file in current directory or $HOME
+		viper.SetConfigName("ztdns")
+		viper.AddConfigPath(".")
+		viper.AddConfigPath("$HOME")
 	}
 
+	// Enable setting config values with ZTDNS_KEY environment variables
 	viper.SetEnvPrefix("ztdns")
-	viper.AutomaticEnv() // read in environment variables that match
+	viper.AutomaticEnv()
+	viper.SetEnvKeyReplacer(strings.NewReplacer("-", "_"))
 
-	// If a config file is found, read it in.
 	if err := viper.ReadInConfig(); err != nil {
 		fmt.Println("Can't read config:", err)
 		os.Exit(1)

cmd/server.go

@@ -20,27 +20,36 @@ import (
 var serverCmd = &cobra.Command{
 	Use:   "server",
 	Short: "Run ztDNS server",
-	Long: `Server (ztdns server) will start the DNS server.append
+	Long: `Server (ztdns server) will start the DNS server.
 
 	Example: ztdns server`,
 	PreRunE: func(cmd *cobra.Command, args []string) error {
 		// Check config and bail if anything important is missing.
 		if viper.GetBool("debug") {
 			log.SetLevel(log.DebugLevel)
-			log.Debug("Setting Debug Mode")
 		}
-		if viper.GetString("ZT.API") == "" {
-			return fmt.Errorf("no API key provided")
+		log.Debug("debug: ", viper.GetBool("debug"))
+		log.Debugf("interface: %s", viper.GetString("interface"))
+		log.Debug("port: ", viper.GetInt("port"))
+		log.Debugf("domain: %q", viper.GetString("domain"))
+		log.Debug("refresh: ", viper.GetInt("refresh"))
+		log.Debugf("api-key: %q", viper.GetString("api-key"))
+		log.Debugf("api-url: %q", viper.GetString("api-url"))
+		log.Debugf("network: %q", viper.GetString("network"))
+		log.Debugf("networks: %#v", viper.GetStringMapString("networks"))
+		log.Debugf("round-robin: %#v", viper.GetStringMapString("round-robin"))
+
+		if viper.GetString("api-key") == "" {
+			return fmt.Errorf("No API key provided")
 		}
-		if len(viper.GetStringMapString("Networks")) == 0 {
-			return fmt.Errorf("no Domain / Network ID pairs Provided")
+
+		if viper.GetString("network") == "" && !viper.IsSet("networks") {
+			return fmt.Errorf("No networks configured (specify network or networks)")
 		}
-		if viper.GetString("ZT.URL") == "" {
-			return fmt.Errorf("no URL provided. Run ztdns mkconfig first")
-		}
-		if viper.GetString("suffix") == "" {
-			return fmt.Errorf("no DNS Suffix provided. Run ztdns mkconfig first")
+		if viper.GetString("network") != "" && viper.IsSet("networks") {
+			return fmt.Errorf("Conflicting network configuration (specify one of network or networks)")
 		}
+
 		return nil
 	},
 	Run: func(cmd *cobra.Command, args []string) {
@@ -48,12 +57,9 @@ var serverCmd = &cobra.Command{
 		lastUpdate := updateDNS()
 		req := make(chan string)
 		// Start the DNS server
-		go dnssrv.Start(viper.GetString("interface"), viper.GetInt("port"), viper.GetString("suffix"), req)
+		go dnssrv.Start(viper.GetString("interface"), viper.GetInt("port"), viper.GetString("domain"), req)
 
-		refresh := viper.GetInt("DbRefresh")
-		if refresh == 0 {
-			refresh = 30
-		}
+		refresh := viper.GetInt("refresh")
 		for {
 			// Block until a new request comes in
 			n := <-req
@@ -69,49 +75,64 @@ var serverCmd = &cobra.Command{
 
 func init() {
 	RootCmd.AddCommand(serverCmd)
-	serverCmd.PersistentFlags().String("interface", "", "interface to listen on")
-	viper.BindPFlag("interface", serverCmd.PersistentFlags().Lookup("interface"))
+	serverCmd.Flags().String("interface", "zt0", "network interface to bind to")
+	serverCmd.Flags().Int("port", 53, "port to listen on")
+	serverCmd.Flags().String("domain", "zt", "domain to serve names under")
+	serverCmd.Flags().Int("refresh", 30, "how often to poll the ZeroTier controller in minutes")
+	serverCmd.Flags().String("api-key", "", "ZeroTier API key")
+	serverCmd.Flags().String("api-url", "https://my.zerotier.com/api", "ZeroTier API URL")
+	serverCmd.Flags().String("network", "", "ZeroTier Network ID")
+	viper.BindPFlags(serverCmd.Flags())
 }
 
+// TODO: refactor
 func updateDNS() time.Time {
 	// Get config info
-	API := viper.GetString("ZT.API")
-	URL := viper.GetString("ZT.URL")
-	suffix := viper.GetString("suffix")
+	apiKey := viper.GetString("api-key")
+	apiUrl := viper.GetString("api-url")
+	rootDomain := viper.GetString("domain")
 
 	rrDNSPatterns := make(map[string]*regexp.Regexp)
 	rrDNSRecords := make(map[string][]dnssrv.Records)
 
-	for re, host := range viper.GetStringMapString("RoundRobin") {
+	for re, host := range viper.GetStringMapString("round-robin") {
 		rrDNSPatterns[host] = regexp.MustCompile(re)
 		log.Debugf("Creating match '%s' for %s host", re, host)
 	}
 
-	// Get all configured networks:
-	for domain, id := range viper.GetStringMapString("Networks") {
-		// Get ZeroTier Network info
-		ztnetwork, err := ztapi.GetNetworkInfo(API, URL, id)
-		if err != nil {
-			log.Fatalf("Unable to update DNS entries: %s", err.Error())
+	networks := viper.GetStringMapString("networks")
+	if len(networks) == 0 {
+		networks = map[string]string{"": viper.GetString("network")}
 	}
 
-		// Get list of members in network
-		log.Infof("Getting Members of Network: %s (%s)", ztnetwork.Config.Name, domain)
-		lst, err := ztapi.GetMemberList(API, URL, ztnetwork.ID)
-		if err != nil {
-			log.Fatalf("Unable to update DNS entries: %s", err.Error())
+	// Get all configured networks:
+	for domain, networkID := range networks {
+		suffix := "." + rootDomain + "."
+		if domain != "" {
+			suffix = "." + domain + suffix
 		}
-		log.Infof("Got %d members", len(*lst))
+
+		ztnetwork, err := ztapi.GetNetworkInfo(apiKey, apiUrl, networkID)
+		if err != nil {
+			log.Fatalf("Unable to get network info: %s", err.Error())
+		}
+
+		log.Infof("Getting members of network: %s (%s)", ztnetwork.Config.Name, suffix)
+		lst, err := ztapi.GetMemberList(apiKey, apiUrl, ztnetwork.ID)
+		if err != nil {
+			log.Fatalf("Unable to get member list: %s", err.Error())
+		}
+		log.Debugf("Got %d members", len(*lst))
 
 		for _, n := range *lst {
 			// For all online members
 			if n.Online {
-				// Sanitize name
+				// Sanitize member name
 				name := strings.ToLower(n.Name)
 				name = strings.ReplaceAll(name, " ", "-")
 				re := regexp.MustCompile("[^a-zA-Z0-9-]+")
 				name = re.ReplaceAllString(name, "")
-				record := name + "." + domain + "." + suffix + "."
+				record := name + suffix
 
 				// Clear current DNS records
 				dnssrv.DNSDatabase[record] = dnssrv.Records{}
@@ -144,7 +165,6 @@ func updateDNS() time.Time {
 				for host, re := range rrDNSPatterns {
 					log.Debugf("Checking matches for %s host", host)
 					if match := re.FindStringSubmatch(n.Name); match != nil {
-						// prefix := fmt.Sprintf(host, iface(match[1:]))
 						rrRecord := host + "." + domain + "." + suffix + "."
 
 						log.Infof("Adding ips to RR record %-15s IPv4: %-15s IPv6: %s, from host %s", rrRecord, ip4, ip6, n.Name)
@@ -169,12 +189,3 @@ func updateDNS() time.Time {
 	// Return the current update time
 	return time.Now()
 }
-
-// Convert slice of string to interface for fmt
-func iface(list []string) []interface{} {
-	vals := make([]interface{}, len(list))
-	for i, v := range list {
-		vals[i] = v
-	}
-	return vals
-}

dnssrv/dnssrv.go

@@ -29,7 +29,7 @@ var DNSDatabase = map[string]Records{}
 var queryChan chan string
 
 // Start brings up a DNS server for the specified suffix on a given port.
-func Start(iface string, port int, suffix string, req chan string) error {
+func Start(iface string, port int, suffix string, req chan string) {
 	queryChan = req
 
 	if port == 0 {
@@ -58,12 +58,16 @@ func Start(iface string, port int, suffix string, req chan string) error {
 			log.Printf("Starting server for %s on %s", suffix, server.Addr)
 			err := server.ListenAndServe()
 			if err != nil {
-				log.Fatalf("failed to start DNS server: %s", err.Error())
+				log.Fatalf("Failed to start DNS server: %s", err.Error())
 			}
-			defer server.Shutdown()
+			defer func () {
+				err := server.Shutdown()
+				if err != nil {
+					log.Fatalf("Failed to stop DNS server: %s", err.Error())
+				}
+			}()
 		}(suffix, addr, port)
 	}
-	return nil
 }
 
 func getIfaceAddrs(iface string) []net.IP {
@@ -103,7 +107,9 @@ func handleDNSRequest(w dns.ResponseWriter, r *dns.Msg) {
 		parseQuery(m)
 	}
 
-	w.WriteMsg(m)
+	if err := w.WriteMsg(m); err != nil {
+		log.Errorf("Failed to send response: %s", err.Error())
+	}
 }
 
 // parseQuery reads and creates an answer to a DNS query.
@@ -133,15 +139,15 @@ func parseQuery(m *dns.Msg) {
 
 // shuffle ip addresses for Round Robin dns
 func shuffle(ips []net.IP) []net.IP {
-	ipsLenght := len(ips)
+	ipsLength := len(ips)
 
-	if ipsLenght < 2 {
+	if ipsLength < 2 {
 		return ips
 	}
 
 	r := rand.New(rand.NewSource(time.Now().UnixNano()))
-	ret := make([]net.IP, ipsLenght)
-	perm := r.Perm(ipsLenght)
+	ret := make([]net.IP, ipsLength)
+	perm := r.Perm(ipsLength)
 
 	for i, randIndex := range perm {
 		ret[i] = ips[randIndex]

go.mod

@@ -7,4 +7,5 @@ require (
 	github.com/sirupsen/logrus v1.4.2
 	github.com/spf13/cobra v0.0.5
 	github.com/spf13/viper v1.4.0
+	golang.org/x/tools v0.0.0-20190930201159-7c411dea38b0 // indirect
 )

go.sum

@@ -116,10 +116,13 @@ golang.org/x/net v0.0.0-20181220203305-927f97764cc3/go.mod h1:mL1N/T3taQHkDXs73r
 golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190522155817-f3200d17e092 h1:4QSRKanuywn15aTZvI/mIDEgPQpswuFndXpOj3rKEco=
 golang.org/x/net v0.0.0-20190522155817-f3200d17e092/go.mod h1:HSz+uSET+XFnRR8LxR5pz3Of3rY3CfYBVs4xY44aLks=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859 h1:R/3boaszxrf1GEUWTVDzSKVwLmSJpwZ1yqXm8j0v2QI=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20181107165924-66b7b1311ac8/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -133,7 +136,11 @@ golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/time v0.0.0-20190308202827-9d24e82272b4/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/tools v0.0.0-20180221164845-07fd8470d635/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20190114222345-bf090417da8b/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/tools v0.0.0-20190311212946-11955173bddd h1:/e+gpKk9r3dJobndpTytxS2gOy6m5uvpg+ISQoEcusQ=
 golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
+golang.org/x/tools v0.0.0-20190930201159-7c411dea38b0 h1:7+F62GGWUowoiJOUDivedlBECd/fTeUDJnCu0JetQO0=
+golang.org/x/tools v0.0.0-20190930201159-7c411dea38b0/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
 google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
 google.golang.org/grpc v1.19.0/go.mod h1:mqu4LbDTu4XGKhr4mRzUsmM4RtVoemTSY81AxZiDr8c=

ztapi/ztapi.go

@@ -17,10 +17,6 @@ type apiTime struct {
 
 func (t *apiTime) UnmarshalJSON(b []byte) error {
 	l := len(b)
-	// if string(b) == "0" {
-	// 	t.time = time.Time{}
-	// 	return nil
-	// }
 	if l < 3 {
 		n, err := strconv.ParseInt(string(b), 10, 32)
 		if err != nil {
@@ -52,8 +48,7 @@ func getJSON(url, APIToken string, target interface{}) error {
 	req.Header.Set("Authorization", "bearer "+APIToken)
 	r, err := c.Do(req)
 	if err != nil {
-		fmt.Errorf("API Error: %q", err)
-		return err
+		return fmt.Errorf("API Error: %s", err.Error())
 	}
 	if r.StatusCode != 200 {
 		return fmt.Errorf("API returned error: %s", r.Status)

ztdns.example.yml

@@ -0,0 +1,48 @@
+# This file contains all available configuration options
+# with their default values.
+
+# Network interface to bind to (or "" to bind to).  By default, only respond on
+# the ZeroTier network.
+interface: "zt0"
+
+# Port to listen on.
+port: 53
+
+# Domain to serve names under.  By default, serve members as
+# "<member name>.<network name>.zt".
+domain: "zt"
+
+# How often to poll the ZeroTier controller in minutes.
+refresh: 30
+
+# Enable debug messages.
+debug: false
+
+# An API key for your ZeroTier account (required).
+api-key: ""
+
+# The base API URL for the ZeroTier controller.
+api-url: "https://my.zerotier.com/api"
+
+# ID of the ZeroTier network to serve.  Only one of "network" and "networks" can
+# be specified.
+# E.g., if there is a network with ID "123abc" this would serve its members as
+# "<member name>.zt".
+# network: "123abc"
+network:
+
+# Mappings between ZeroTier network IDs and domain names.  Only one of "network"
+# and "networks" can be specified.
+networks:
+  # E.g., if there is a network with ID "123abc" this would serve its members as
+  # "<member name>.home.zt".
+  # home: "123abc"
+
+# Mappings between round-robin names and regexps to match members.  Names are
+# matched within each network (i.e., if there are members matching a mapping in
+# multiple networks then the name will be defined separately in each).
+round-robin:
+  # E.g., if the "home" network defined above had members "k8s-node-23refw" and
+  # "k8s-node-09sf8g" this would create a name "k8s-nodes" returning one of them
+  # at random.
+  # k8s-nodes: "k8s-node-\w"