net/smtp: use EHLO then HELO

Before we were using "ESMTP" in the banner as a clue,
but that is not required by the RFC and breaks mailing
to smtp.yandex.ru.

Fixes #3045.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5687066

src/pkg/net/smtp/smtp.go

@@ -50,15 +50,14 @@ func Dial(addr string) (*Client, error) {
 // server name to be used when authenticating.
 func NewClient(conn net.Conn, host string) (*Client, error) {
 	text := textproto.NewConn(conn)
-	_, msg, err := text.ReadResponse(220)
+	_, _, err := text.ReadResponse(220)
 	if err != nil {
 		text.Close()
 		return nil, err
 	}
 	c := &Client{Text: text, conn: conn, serverName: host}
-	if strings.Contains(msg, "ESMTP") {
-		err = c.ehlo()
-	} else {
+	err = c.ehlo()
+	if err != nil {
 		err = c.helo()
 	}
 	return c, err

src/pkg/net/smtp/smtp_test.go

@@ -8,9 +8,11 @@ import (
 	"bufio"
 	"bytes"
 	"io"
+	"net"
 	"net/textproto"
 	"strings"
 	"testing"
+	"time"
 )
 
 type authTest struct {
@@ -59,9 +61,12 @@ type faker struct {
 	io.ReadWriter
 }
 
-func (f faker) Close() error {
-	return nil
-}
+func (f faker) Close() error                     { return nil }
+func (f faker) LocalAddr() net.Addr              { return nil }
+func (f faker) RemoteAddr() net.Addr             { return nil }
+func (f faker) SetDeadline(time.Time) error      { return nil }
+func (f faker) SetReadDeadline(time.Time) error  { return nil }
+func (f faker) SetWriteDeadline(time.Time) error { return nil }
 
 func TestBasic(t *testing.T) {
 	basicServer = strings.Join(strings.Split(basicServer, "\n"), "\r\n")
@@ -180,3 +185,87 @@ Goodbye.
 .
 QUIT
 `
+
+func TestNewClient(t *testing.T) {
+	newClientServer = strings.Join(strings.Split(newClientServer, "\n"), "\r\n")
+	newClientClient = strings.Join(strings.Split(newClientClient, "\n"), "\r\n")
+
+	var cmdbuf bytes.Buffer
+	bcmdbuf := bufio.NewWriter(&cmdbuf)
+	out := func() string {
+		bcmdbuf.Flush()
+		return cmdbuf.String()
+	}
+	var fake faker
+	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(newClientServer)), bcmdbuf)
+	c, err := NewClient(fake, "fake.host")
+	if err != nil {
+		t.Fatalf("NewClient: %v\n(after %v)", err, out())
+	}
+	if ok, args := c.Extension("aUtH"); !ok || args != "LOGIN PLAIN" {
+		t.Fatalf("Expected AUTH supported")
+	}
+	if ok, _ := c.Extension("DSN"); ok {
+		t.Fatalf("Shouldn't support DSN")
+	}
+	if err := c.Quit(); err != nil {
+		t.Fatalf("QUIT failed: %s", err)
+	}
+
+	actualcmds := out()
+	if newClientClient != actualcmds {
+		t.Fatalf("Got:\n%s\nExpected:\n%s", actualcmds, newClientClient)
+	}
+}
+
+var newClientServer = `220 hello world
+250-mx.google.com at your service
+250-SIZE 35651584
+250-AUTH LOGIN PLAIN
+250 8BITMIME
+221 OK
+`
+
+var newClientClient = `EHLO localhost
+QUIT
+`
+
+func TestNewClient2(t *testing.T) {
+	newClient2Server = strings.Join(strings.Split(newClient2Server, "\n"), "\r\n")
+	newClient2Client = strings.Join(strings.Split(newClient2Client, "\n"), "\r\n")
+
+	var cmdbuf bytes.Buffer
+	bcmdbuf := bufio.NewWriter(&cmdbuf)
+	var fake faker
+	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(newClient2Server)), bcmdbuf)
+	c, err := NewClient(fake, "fake.host")
+	if err != nil {
+		t.Fatalf("NewClient: %v", err)
+	}
+	if ok, _ := c.Extension("DSN"); ok {
+		t.Fatalf("Shouldn't support DSN")
+	}
+	if err := c.Quit(); err != nil {
+		t.Fatalf("QUIT failed: %s", err)
+	}
+
+	bcmdbuf.Flush()
+	actualcmds := cmdbuf.String()
+	if newClient2Client != actualcmds {
+		t.Fatalf("Got:\n%s\nExpected:\n%s", actualcmds, newClient2Client)
+	}
+}
+
+var newClient2Server = `220 hello world
+502 EH?
+250-mx.google.com at your service
+250-SIZE 35651584
+250-AUTH LOGIN PLAIN
+250 8BITMIME
+221 OK
+`
+
+var newClient2Client = `EHLO localhost
+HELO localhost
+QUIT
+`