ssh: add (*Client).DialContext method

This change adds DialContext to ssh.Client, which opens a TCP-IP
connection tunneled over the SSH connection. This is useful for
proxying network connections, e.g. setting
(net/http.Transport).DialContext.

Fixes golang/go#20288.

Change-Id: I110494c00962424ea803065535ebe2209364ac27
GitHub-Last-Rev: 3176984a71a9a1422702e3a071340ecfff71ff62
GitHub-Pull-Request: golang/crypto#260
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/504735
Run-TryBot: Nicola Murino <nicola.murino@gmail.com>
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
Auto-Submit: Nicola Murino <nicola.murino@gmail.com>
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Nicola Murino <nicola.murino@gmail.com>
Commit-Queue: Nicola Murino <nicola.murino@gmail.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/ssh/tcpip_test.go b/ssh/tcpip_test.go
index f1265cb..4d85114 100644
--- a/ssh/tcpip_test.go
+++ b/ssh/tcpip_test.go
@@ -5,7 +5,10 @@
 package ssh
 
 import (
+	"context"
+	"net"
 	"testing"
+	"time"
 )
 
 func TestAutoPortListenBroken(t *testing.T) {
@@ -18,3 +21,33 @@ func TestAutoPortListenBroken(t *testing.T) {
 		t.Errorf("version %q marked as broken", works)
 	}
 }
+
+func TestClientImplementsDialContext(t *testing.T) {
+	type ContextDialer interface {
+		DialContext(context.Context, string, string) (net.Conn, error)
+	}
+	// Belt and suspenders assertion, since package net does not
+	// declare a ContextDialer type.
+	var _ ContextDialer = &net.Dialer{}
+	var _ ContextDialer = &Client{}
+}
+
+func TestClientDialContextWithCancel(t *testing.T) {
+	c := &Client{}
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	_, err := c.DialContext(ctx, "tcp", "localhost:1000")
+	if err != context.Canceled {
+		t.Errorf("DialContext: got nil error, expected %v", context.Canceled)
+	}
+}
+
+func TestClientDialContextWithDeadline(t *testing.T) {
+	c := &Client{}
+	ctx, cancel := context.WithDeadline(context.Background(), time.Now())
+	defer cancel()
+	_, err := c.DialContext(ctx, "tcp", "localhost:1000")
+	if err != context.DeadlineExceeded {
+		t.Errorf("DialContext: got nil error, expected %v", context.DeadlineExceeded)
+	}
+}