ssh: Add retries when to setupProxy

When using podman-machine with applehv, sometimes gvproxy would die
shortly after being started.
The following happens:
- podman starts gvproxy with --listen-vfkit
- gvproxy starts and waits for vfkit to create a network connection
- podman starts vfkit
- vfkit creates the VM and connects to gvproxy
- gvproxy resumes its execution, and tries to create the ssh forwards
  podman asked for on the command line
- gvproxy fails to create the ssh forward and exits

This happens because setupProxy fails in (*Bastion).reconnect with
"ssh: handshake failed: EOF". This is related to
https://www.man7.org/linux/man-pages/man8/systemd-user-sessions.8.html
even if it's possible to create a TCP connection to the ssh port,
sshd/pam won't necessarily allow you to connect at the ssh level.

This commit fixes this bug by adding a retry to the calls to
CreateBastion() to complement the retries already present in
initialConnection().

pkg/sshclient/bastion.go

@@ -84,13 +84,13 @@ func HostKey(host string) ssh.PublicKey {
 	return nil
 }
 
-func CreateBastion(_url *url.URL, passPhrase string, identity string, initial net.Conn, connect ConnectCallback) (Bastion, error) {
+func CreateBastion(_url *url.URL, passPhrase string, identity string, initial net.Conn, connect ConnectCallback) (*Bastion, error) {
 	var authMethods []ssh.AuthMethod
 
 	if len(identity) > 0 {
 		s, err := PublicKey(identity, []byte(passPhrase))
 		if err != nil {
-			return Bastion{}, errors.Wrapf(err, "failed to parse identity %q", identity)
+			return nil, errors.Wrapf(err, "failed to parse identity %q", identity)
 		}
 		authMethods = append(authMethods, ssh.PublicKeys(s))
 	}
@@ -100,7 +100,7 @@ func CreateBastion(_url *url.URL, passPhrase string, identity string, initial ne
 	}
 
 	if len(authMethods) == 0 {
-		return Bastion{}, errors.New("No available auth methods")
+		return nil, errors.New("No available auth methods")
 	}
 
 	port := _url.Port()
@@ -149,7 +149,7 @@ func CreateBastion(_url *url.URL, passPhrase string, identity string, initial ne
 	}
 
 	bastion := Bastion{nil, config, _url.Hostname(), port, _url.Path, connect}
-	return bastion, bastion.reconnect(context.Background(), initial)
+	return &bastion, bastion.reconnect(context.Background(), initial)
 }
 
 func (bastion *Bastion) Reconnect(ctx context.Context) error {

pkg/sshclient/ssh_forwarder.go

@@ -171,14 +171,17 @@ func setupProxy(ctx context.Context, socketURI *url.URL, dest *url.URL, identity
 		return &SSHForward{}, err
 	}
 
-	bastion, err := CreateBastion(dest, passphrase, identity, conn, connectFunc)
+	createBastion := func() (*Bastion, error) {
+		return CreateBastion(dest, passphrase, identity, conn, connectFunc)
+	}
+	bastion, err := retry(ctx, createBastion, "Waiting for sshd")
 	if err != nil {
-		return &SSHForward{}, err
+		return &SSHForward{}, fmt.Errorf("setupProxy failed: %w", err)
 	}
 
 	logrus.Debugf("Socket forward established: %s -> %s\n", socketURI.Path, dest.Path)
 
-	return &SSHForward{listener, &bastion, socketURI}, nil
+	return &SSHForward{listener, bastion, socketURI}, nil
 }
 
 const maxRetries = 60