Fix stuck call to Dial when calling Stop on the initiator

This commit fixes an issue when calling Start() and then
Stop() on the initiator while the connection is likely
to fail and timeout. Calling initiator.Stop() will block since
Dial will attempt to connect until it times out and returns
on the 'waitForReconnectInterval' call.

We mitigate this problem by using a proxy.ContextDialer and
allowing to pass a context with cancellation method to the
dialer.DialContext method on 'handleConnection'.

We need to start a routine listening for the stopChan in
order to call cancel() explicitly and thus exit the DialContext
method.

Note: there are scenarios where cancel() will be called twice,
this choice was made in order to avoid a larger refactor of the
reconnect logic, but since the call to cancel() is idempotent,
this doesn't lead to any adverse effect.

fixes #653

Signed-off-by: Alexandre Beslic <ab21c8b9f7@abronan.com>

dialer.go

@@ -25,7 +25,7 @@ import (
 	"github.com/quickfixgo/quickfix/config"
 )
 
-func loadDialerConfig(settings *SessionSettings) (dialer proxy.Dialer, err error) {
+func loadDialerConfig(settings *SessionSettings) (dialer proxy.ContextDialer, err error) {
 	stdDialer := &net.Dialer{}
 	if settings.HasSetting(config.SocketTimeout) {
 		timeout, err := settings.DurationSetting(config.SocketTimeout)
@@ -73,9 +73,23 @@ func loadDialerConfig(settings *SessionSettings) (dialer proxy.Dialer, err error
 			}
 		}
 
-		dialer, err = proxy.SOCKS5("tcp", fmt.Sprintf("%s:%d", proxyHost, proxyPort), proxyAuth, dialer)
+		var proxyDialer proxy.Dialer
+
+		proxyDialer, err = proxy.SOCKS5("tcp", fmt.Sprintf("%s:%d", proxyHost, proxyPort), proxyAuth, stdDialer)
+		if err != nil {
+			return
+		}
+
+		if contextDialer, ok := proxyDialer.(proxy.ContextDialer); ok {
+			dialer = contextDialer
+		} else {
+			err = fmt.Errorf("proxy does not support context dialer")
+			return
+		}
+
 	default:
 		err = fmt.Errorf("unsupported proxy type %s", proxyType)
 	}
+
 	return
 }

initiator.go

@@ -17,6 +17,7 @@ package quickfix
 
 import (
 	"bufio"
+	"context"
 	"crypto/tls"
 	"strings"
 	"sync"
@@ -50,7 +51,7 @@ func (i *Initiator) Start() (err error) {
 			return
 		}
 
-		var dialer proxy.Dialer
+		var dialer proxy.ContextDialer
 		if dialer, err = loadDialerConfig(settings); err != nil {
 			return
 		}
@@ -142,7 +143,7 @@ func (i *Initiator) waitForReconnectInterval(reconnectInterval time.Duration) bo
 	return true
 }
 
-func (i *Initiator) handleConnection(session *session, tlsConfig *tls.Config, dialer proxy.Dialer) {
+func (i *Initiator) handleConnection(session *session, tlsConfig *tls.Config, dialer proxy.ContextDialer) {
 	var wg sync.WaitGroup
 	wg.Add(1)
 	go func() {
@@ -162,14 +163,27 @@ func (i *Initiator) handleConnection(session *session, tlsConfig *tls.Config, di
 			return
 		}
 
+		ctx, cancel := context.WithCancel(context.Background())
+
+		// We start a goroutine in order to be able to cancel the dialer mid-connection
+		// on receiving a stop signal to stop the initiator.
+		go func() {
+			select {
+			case <-i.stopChan:
+				cancel()
+			case <-ctx.Done():
+				return
+			}
+		}()
+
 		var disconnected chan interface{}
 		var msgIn chan fixIn
 		var msgOut chan []byte
 
 		address := session.SocketConnectAddress[connectionAttempt%len(session.SocketConnectAddress)]
 		session.log.OnEventf("Connecting to: %v", address)
 
-		netConn, err := dialer.Dial("tcp", address)
+		netConn, err := dialer.DialContext(ctx, "tcp", address)
 		if err != nil {
 			session.log.OnEventf("Failed to connect: %v", err)
 			goto reconnect
@@ -208,13 +222,19 @@ func (i *Initiator) handleConnection(session *session, tlsConfig *tls.Config, di
 			close(disconnected)
 		}()
 
+		// This ensures we properly cleanup the goroutine and context used for
+		// dial cancelation after successful connection.
+		cancel()
+
 		select {
 		case <-disconnected:
 		case <-i.stopChan:
 			return
 		}
 
 	reconnect:
+		cancel()
+
 		connectionAttempt++
 		session.log.OnEventf("Reconnecting in %v", session.ReconnectInterval)
 		if !i.waitForReconnectInterval(session.ReconnectInterval) {