agnhost/connect: send and recv data from SCTP server

If the client immediately closes connection after SCTP handshake,
the server will die with EOF, adding send and recv calls in the
client to make sure server client handling loop exits gracefully.

Signed-off-by: Daman Arora <aroradaman@gmail.com>

test/images/agnhost/connect/connect.go

@@ -47,12 +47,14 @@ var (
 	timeout  time.Duration
 	protocol string
 	udpData  string
+	sctpData string
 )
 
 func init() {
 	CmdConnect.Flags().DurationVar(&timeout, "timeout", time.Duration(0), "Maximum time before returning an error")
 	CmdConnect.Flags().StringVar(&protocol, "protocol", "tcp", "The protocol to use to perform the connection, can be tcp, udp or sctp")
 	CmdConnect.Flags().StringVar(&udpData, "udp-data", "hostname", "The UDP payload send to the server")
+	CmdConnect.Flags().StringVar(&sctpData, "sctp-data", "hostname", "The SCTP payload send to the server")
 }
 
 func main(cmd *cobra.Command, args []string) {
@@ -63,7 +65,7 @@ func main(cmd *cobra.Command, args []string) {
 	case "udp":
 		connectUDP(dest, timeout, udpData)
 	case "sctp":
-		connectSCTP(dest, timeout)
+		connectSCTP(dest, timeout, sctpData)
 	default:
 		fmt.Fprint(os.Stderr, "Unsupported protocol\n", protocol)
 		os.Exit(1)
@@ -103,7 +105,11 @@ func connectTCP(dest string, timeout time.Duration) {
 	os.Exit(1)
 }
 
-func connectSCTP(dest string, timeout time.Duration) {
+func connectSCTP(dest string, timeout time.Duration, data string) {
+	var (
+		buf  = make([]byte, 1024)
+		conn *sctp.SCTPConn
+	)
 	addr, err := sctp.ResolveSCTPAddr("sctp", dest)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "DNS: %v\n", err)
@@ -114,11 +120,24 @@ func connectSCTP(dest string, timeout time.Duration) {
 	errCh := make(chan error)
 
 	go func() {
-		conn, err := sctp.DialSCTP("sctp", nil, addr)
+		conn, err = sctp.DialSCTP("sctp", nil, addr)
-		if err == nil {
+		if err != nil {
-			conn.Close()
+			errCh <- err
+			return
+		}
+		defer func() {
+			errCh <- conn.Close()
+		}()
+
+		if _, err = conn.Write([]byte(fmt.Sprintf("%s\n", data))); err != nil {
+			errCh <- err
+			return
+		}
+
+		if _, err = conn.Read(buf); err != nil {
+			errCh <- err
+			return
 		}
-		errCh <- err
 	}()
 
 	select {