Add support for session tickets

Closes #533

Signed-off-by: Tomás Senart <tsenart@gmail.com>

README.md

@@ -128,6 +128,8 @@ attack command:
     	List of addresses (ip:port) to use for DNS resolution. Disables use of local system DNS. (comma separated list)
   -root-certs value
     	TLS root certificate files (comma separated list)
+  -session-tickets
+    	Enable TLS session resumption support using session tickets (default false)
   -targets string
     	Targets file (default "stdin")
   -timeout duration
@@ -384,6 +386,10 @@ the ones configured by the operating system. Works only on non Windows systems.
 Specifies the trusted TLS root CAs certificate files as a comma separated
 list. If unspecified, the default system CAs certificates will be used.
 
+#### `-session-tickets`
+
+Specifies whether to support TLS session resumption using session tickets.
+
 #### `-targets`
 
 Specifies the file from which to read targets, defaulting to stdin.

attack.go

@@ -57,6 +57,7 @@ func attackCmd() command {
 	fs.BoolVar(&opts.keepalive, "keepalive", true, "Use persistent connections")
 	fs.StringVar(&opts.unixSocket, "unix-socket", "", "Connect over a unix socket. This overrides the host address in target URLs")
 	fs.Var(&dnsTTLFlag{&opts.dnsTTL}, "dns-ttl", "Cache DNS lookups for the given duration [-1 = disabled, 0 = forever]")
+	fs.BoolVar(&opts.sessionTickets, "session-tickets", false, "Support TLS session resumption using session tickets")
 	systemSpecificFlags(fs, opts)
 
 	return command{fs, func(args []string) error {
@@ -101,6 +102,7 @@ type attackOpts struct {
 	resolvers      csl
 	unixSocket     string
 	dnsTTL         time.Duration
+	sessionTickets bool
 }
 
 // attack validates the attack arguments, sets up the
@@ -193,6 +195,7 @@ func attack(opts *attackOpts) (err error) {
 		vegeta.ProxyHeader(proxyHdr),
 		vegeta.ChunkedBody(opts.chunked),
 		vegeta.DNSCaching(opts.dnsTTL),
+		vegeta.SessionTickets(opts.sessionTickets),
 	)
 
 	res := atk.Attack(tr, opts.rate, opts.duration, opts.name)

lib/attack.go

@@ -246,6 +246,18 @@ func UnixSocket(socket string) func(*Attacker) {
 	}
 }
 
+// SessionTickets returns a functional option which configures usage of session
+// tickets for TLS session resumption.
+func SessionTickets(enabled bool) func(*Attacker) {
+	return func(a *Attacker) {
+		if enabled {
+			cf := a.client.Transport.(*http.Transport).TLSClientConfig
+			cf.SessionTicketsDisabled = false
+			cf.ClientSessionCache = tls.NewLRUClientSessionCache(0)
+		}
+	}
+}
+
 // Client returns a functional option that allows you to bring your own http.Client
 func Client(c *http.Client) func(*Attacker) {
 	return func(a *Attacker) { a.client = *c }

lib/attack_test.go

@@ -63,7 +63,6 @@ func TestAttackDuration(t *testing.T) {
 }
 
 func TestTLSConfig(t *testing.T) {
-	t.Parallel()
 	atk := NewAttacker()
 	got := atk.client.Transport.(*http.Transport).TLSClientConfig
 	if want := (&tls.Config{InsecureSkipVerify: true}); !reflect.DeepEqual(got, want) {
@@ -164,6 +163,20 @@ func TestKeepAlive(t *testing.T) {
 	}
 }
 
+// This test cannot be run in parallel with TestTLSConfig() because ClientSessionCache
+// is designed to be called concurrently from different goroutines.
+func TestSessionTickets(t *testing.T) {
+	atk := NewAttacker(SessionTickets(true))
+	cf := atk.client.Transport.(*http.Transport).TLSClientConfig
+	got, want := cf.SessionTicketsDisabled, false
+	if got != want {
+		t.Fatalf("got: %v, want: %v", got, want)
+	}
+	if cf.ClientSessionCache == nil {
+		t.Fatalf("ClientSessionCache is nil")
+	}
+}
+
 func TestConnections(t *testing.T) {
 	t.Parallel()
 	atk := NewAttacker(Connections(23))