Add roundrobin record via mtaches (#4)

.dockerignore

@@ -17,3 +17,5 @@ Dockerfile
 
 # Output of the go coverage tool, specifically when used with LiteIDE
 *.out
+
+.DS_Store

.gitignore

@@ -15,3 +15,5 @@
 
 # Output of the go coverage tool, specifically when used with LiteIDE
 *.out
+
+.DS_Store

.ztdns.toml.example

@@ -19,3 +19,11 @@ URL = "https://my.zerotier.com/api"
 # 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/mkconfig.go

@@ -51,6 +51,13 @@ URL = "https://my.zerotier.com/api"
 # 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/root.go

@@ -43,17 +43,20 @@ func init() {
 
 // initConfig reads in config file and ENV variables if set.
 func initConfig() {
-	viper.SetConfigName(".ztdns") // name of config file (without extension)
-	viper.AddConfigPath(".")      // adding current directory as first search path
-	viper.AddConfigPath("$HOME")  // adding home directory as second search path
-
 	if cfgFile != "" { // enable ability to specify config file via flag
 		viper.SetConfigFile(cfgFile)
+	} else {
+		viper.SetConfigName(".ztdns") // name of config file (without extension)
+		viper.AddConfigPath(".")      // adding current directory as first search path
+		viper.AddConfigPath("$HOME")  // adding home directory as second search path
 	}
 
 	viper.SetEnvPrefix("ztdns")
 	viper.AutomaticEnv() // read in environment variables that match
 
 	// If a config file is found, read it in.
-	viper.ReadInConfig()
+	if err := viper.ReadInConfig(); err != nil {
+		fmt.Println("Can't read config:", err)
+		os.Exit(1)
+	}
 }

cmd/server.go

@@ -6,6 +6,7 @@ package cmd
 import (
 	"fmt"
 	"net"
+	"regexp"
 	"time"
 
 	log "github.com/sirupsen/logrus"
@@ -78,6 +79,14 @@ func updateDNS() time.Time {
 	URL := viper.GetString("ZT.URL")
 	suffix := viper.GetString("suffix")
 
+	rrDNSPatterns := make(map[string]*regexp.Regexp)
+	rrDNSRecords := make(map[string][]dnssrv.Records)
+
+	for re, host := range viper.GetStringMapString("RoundRobin") {
+		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
@@ -115,16 +124,51 @@ func updateDNS() time.Time {
 				for _, a := range n.Config.IPAssignments {
 					ip4 = append(ip4, net.ParseIP(a))
 				}
-				// Add the record to the database
-				log.Infof("Updating %-15s IPv4: %-15s IPv6: %s", record, ip4, ip6)
-				dnssrv.DNSDatabase[record] = dnssrv.Records{
+
+				dnsRecord := dnssrv.Records{
 					A:    ip4,
 					AAAA: ip6,
 				}
+
+				// Add the record to the database
+				log.Infof("Updating %-15s IPv4: %-15s IPv6: %s", record, ip4, ip6)
+				dnssrv.DNSDatabase[record] = dnsRecord
+
+				// Finding matches for RoundRobin dns
+				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)
+						rrDNSRecords[rrRecord] = append(rrDNSRecords[rrRecord], dnsRecord)
+					}
+				}
 			}
 		}
+
+		for rrRecord, dnsRecords := range rrDNSRecords {
+			rrRecordIps := dnssrv.Records{}
+			for _, ips := range dnsRecords {
+				rrRecordIps.A = append(rrRecordIps.A, ips.A...)
+				rrRecordIps.AAAA = append(rrRecordIps.AAAA, ips.AAAA...)
+			}
+
+			log.Infof("Updating %-15s IPv4: %-15s IPv6: %s", rrRecord, rrRecordIps.A, rrRecordIps.AAAA)
+			dnssrv.DNSDatabase[rrRecord] = rrRecordIps
+		}
 	}
 
 	// 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

@@ -6,6 +6,7 @@ package dnssrv
 
 import (
 	"fmt"
+	"math/rand"
 	"net"
 	"time"
 
@@ -112,14 +113,14 @@ func parseQuery(m *dns.Msg) {
 		if rec, ok := DNSDatabase[q.Name]; ok {
 			switch q.Qtype {
 			case dns.TypeA:
-				for _, ip := range rec.A {
+				for _, ip := range shuffle(rec.A) {
 					rr, err := dns.NewRR(fmt.Sprintf("%s A %s", q.Name, ip.String()))
 					if err == nil {
 						m.Answer = append(m.Answer, rr)
 					}
 				}
 			case dns.TypeAAAA:
-				for _, ip := range rec.AAAA {
+				for _, ip := range shuffle(rec.AAAA) {
 					rr, err := dns.NewRR(fmt.Sprintf("%s AAAA %s", q.Name, ip.String()))
 					if err == nil {
 						m.Answer = append(m.Answer, rr)
@@ -129,3 +130,16 @@ func parseQuery(m *dns.Msg) {
 		}
 	}
 }
+
+// shuffle ip addresses for Round Robin dns
+func shuffle(ips []net.IP) []net.IP {
+	r := rand.New(rand.NewSource(time.Now().UnixNano()))
+	ret := make([]net.IP, len(ips))
+	perm := r.Perm(len(ips))
+
+	for i, randIndex := range perm {
+		ret[i] = ips[randIndex]
+	}
+
+	return ret
+}