Add handshake timeout

internal/vpn/client.go

@@ -638,14 +638,16 @@ func (c *Client) shakeHands(conn net.Conn) (TUNIP, TUNGateway net.IP, err error)
 		Passcode:              c.cfg.Passcode,
 	}
 
+	const handshakeTimeout = 5 * time.Second
+
 	fmt.Printf("Sending client hello: %v\n", cHello)
 
-	if err := WriteJSON(conn, &cHello); err != nil {
+	if err := WriteJSONWithTimeout(conn, &cHello, handshakeTimeout); err != nil {
 		return nil, nil, fmt.Errorf("error sending client hello: %w", err)
 	}
 
 	var sHello ServerHello
-	if err := ReadJSON(conn, &sHello); err != nil {
+	if err := ReadJSONWithTimeout(conn, &sHello, handshakeTimeout); err != nil {
 		return nil, nil, fmt.Errorf("error reading server hello: %w", err)
 	}
 

internal/vpn/net.go

@@ -5,13 +5,31 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"time"
 
 	"github.com/skycoin/dmsg/cipher"
 	"github.com/skycoin/dmsg/noise"
 
 	"github.com/skycoin/skywire/pkg/app/appnet"
 )
 
+// WriteJSONWithTimeout marshals `data` and sends it over the `conn` with the specified write `timeout`.
+func WriteJSONWithTimeout(conn net.Conn, data interface{}, timeout time.Duration) error {
+	if err := conn.SetWriteDeadline(time.Now().Add(timeout)); err != nil {
+		return fmt.Errorf("failed to set write deadline: %w", err)
+	}
+
+	if err := WriteJSON(conn, data); err != nil {
+		return err
+	}
+
+	if err := conn.SetWriteDeadline(time.Time{}); err != nil {
+		return fmt.Errorf("failed to remove write deadline: %w", err)
+	}
+
+	return nil
+}
+
 // WriteJSON marshals `data` and sends it over the `conn`.
 func WriteJSON(conn net.Conn, data interface{}) error {
 	dataBytes, err := json.Marshal(data)
@@ -31,6 +49,24 @@ func WriteJSON(conn net.Conn, data interface{}) error {
 	return nil
 }
 
+// ReadJSONWithTimeout reads portion of data from the `conn` and unmarshals it into `data` with the
+// specified read `timeout`.
+func ReadJSONWithTimeout(conn net.Conn, data interface{}, timeout time.Duration) error {
+	if err := conn.SetReadDeadline(time.Now().Add(timeout)); err != nil {
+		return fmt.Errorf("failed to set read deadline: %w", err)
+	}
+
+	if err := ReadJSON(conn, data); err != nil {
+		return err
+	}
+
+	if err := conn.SetReadDeadline(time.Time{}); err != nil {
+		return fmt.Errorf("failed to remove read deadline: %w", err)
+	}
+
+	return nil
+}
+
 // ReadJSON reads portion of data from the `conn` and unmarshals it into `data`.
 func ReadJSON(conn net.Conn, data interface{}) error {
 	const bufSize = 1024