test: run mock dns recursors on random ports

command/agent/dns_test.go

@@ -32,8 +32,9 @@ const (
 // the provided reply. This is useful for mocking a DNS recursor with
 // an expected result.
 func makeRecursor(t *testing.T, answer []dns.RR) *dns.Server {
+	randomPort := TenPorts()
 	cfg := TestConfig()
-	dnsAddr := fmt.Sprintf("%s:%d", cfg.Addresses.DNS, cfg.Ports.DNS)
+	dnsAddr := fmt.Sprintf("%s:%d", cfg.Addresses.DNS, randomPort)
 	mux := dns.NewServeMux()
 	mux.HandleFunc(".", func(resp dns.ResponseWriter, msg *dns.Msg) {
 		ans := &dns.Msg{Answer: answer[:]}

command/agent/testagent.go

@@ -242,6 +242,12 @@ func UniqueID() string {
 	return id
 }
 
+// TenPorts returns the first port number of a block of
+// ten random ports.
+func TenPorts() int {
+	return 1030 + int(rand.Int31n(6440))*10
+}
+
 // pickRandomPorts selects random ports from fixed size random blocks of
 // ports. This does not eliminate the chance for port conflict but
 // reduces it significanltly with little overhead. Furthermore, asking
@@ -251,7 +257,7 @@ func UniqueID() string {
 // Instead of relying on one set of ports to be sufficient we retry
 // starting the agent with different ports on port conflict.
 func pickRandomPorts(c *Config) {
-	port := 1030 + int(rand.Int31n(6440))*10
+	port := TenPorts()
 	c.Ports.DNS = port + 1
 	c.Ports.HTTP = port + 2
 	// when we enable HTTPS then we need to fix finding the
@@ -260,7 +266,6 @@ func pickRandomPorts(c *Config) {
 	c.Ports.SerfLan = port + 4
 	c.Ports.SerfWan = port + 5
 	c.Ports.Server = port + 6
-	//c.ConsulConfig.Memberlist.
 }
 
 // BoolTrue and BoolFalse exist to create a *bool value.