net/http: Transport: be paranoid about any non-100 1xx response

Since we can't properly handle anything except 100, treat all
1xx informational responses as sketchy and don't reuse the
connection for future requests.

The only other 1xx response code currently in use in the wild
is WebSockets' use of "101 Switching Protocols", but our
code.google.com/p/go.net/websockets doesn't use Client or
Transport: it uses ReadResponse directly, so is unaffected by
this CL.  (and its tests still pass)

So this CL is entirely just future-proofing paranoia.
Also: the Internet is weird.

Update #2184
Update #3665

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/8208043

src/pkg/net/http/serve_test.go

@@ -77,10 +77,15 @@ type rwTestConn struct {
 	io.Reader
 	io.Writer
 	noopConn
-	closec chan bool // if non-nil, send value to it on close
+
+	closeFunc func() error // called if non-nil
+	closec    chan bool    // else, if non-nil, send value to it on close
 }
 
 func (c *rwTestConn) Close() error {
+	if c.closeFunc != nil {
+		return c.closeFunc()
+	}
 	select {
 	case c.closec <- true:
 	default:

src/pkg/net/http/transport.go

@@ -715,7 +715,10 @@ func (pc *persistConn) readLoop() {
 			resp.Body = &bodyEOFSignal{body: resp.Body}
 		}
 
-		if err != nil || resp.Close || rc.req.Close {
+		if err != nil || resp.Close || rc.req.Close || resp.StatusCode <= 199 {
+			// Don't do keep-alive on error if either party requested a close
+			// or we get an unexpected informational (1xx) response.
+			// StatusCode 100 is already handled above.
 			alive = false
 		}
 

src/pkg/net/http/transport_test.go

@@ -1416,18 +1416,28 @@ func TestTransportReading100Continue(t *testing.T) {
 		for {
 			n++
 			req, err := ReadRequest(br)
+			if err == io.EOF {
+				return
+			}
 			if err != nil {
 				t.Error(err)
 				return
 			}
 			slurp, err := ioutil.ReadAll(req.Body)
-			if err != nil || string(slurp) != reqBody(n) {
-				t.Errorf("Server got %q, %v; want 'body'", slurp, err)
+			if err != nil {
+				t.Errorf("Server request body slurp: %v", err)
 				return
 			}
 			id := req.Header.Get("Request-Id")
+			resCode := req.Header.Get("X-Want-Response-Code")
+			if resCode == "" {
+				resCode = "100 Continue"
+				if string(slurp) != reqBody(n) {
+					t.Errorf("Server got %q, %v; want %q", slurp, err, reqBody(n))
+				}
+			}
 			body := fmt.Sprintf("Response number %d", n)
-			v := []byte(strings.Replace(fmt.Sprintf(`HTTP/1.1 100 Continue
+			v := []byte(strings.Replace(fmt.Sprintf(`HTTP/1.1 %s
 Date: Thu, 28 Feb 2013 17:55:41 GMT
 
 HTTP/1.1 200 OK
@@ -1435,7 +1445,7 @@ Content-Type: text/html
 Echo-Request-Id: %s
 Content-Length: %d
 
-%s`, id, len(body), body), "\n", "\r\n", -1))
+%s`, resCode, id, len(body), body), "\n", "\r\n", -1))
 			w.Write(v)
 			if id == reqID(numReqs) {
 				return
@@ -1451,6 +1461,11 @@ Content-Length: %d
 			conn := &rwTestConn{
 				Reader: cr,
 				Writer: sw,
+				closeFunc: func() error {
+					sw.Close()
+					cw.Close()
+					return nil
+				},
 			}
 			go send100Response(cw, sr)
 			return conn, nil
@@ -1459,21 +1474,38 @@ Content-Length: %d
 	}
 	defer tr.CloseIdleConnections()
 	c := &Client{Transport: tr}
-	for i := 1; i <= numReqs; i++ {
-		req, _ := NewRequest("POST", "http://dummy.tld/", strings.NewReader(reqBody(i)))
-		req.Header.Set("Request-Id", reqID(i))
+
+	testResponse := func(req *Request, name string, wantCode int) {
 		res, err := c.Do(req)
 		if err != nil {
-			t.Fatalf("Do (i=%d): %v", i, err)
+			t.Fatalf("%s: Do: %v", name, err)
 		}
-		if res.StatusCode != 200 {
-			t.Fatalf("Response Statuscode=%d; want 200 (i=%d): %v", res.StatusCode, i, err)
+		if res.StatusCode != wantCode {
+			t.Fatalf("%s: Response Statuscode=%d; want %d", name, res.StatusCode, wantCode)
+		}
+		if id, idBack := req.Header.Get("Request-Id"), res.Header.Get("Echo-Request-Id"); id != "" && id != idBack {
+			t.Errorf("%s: response id %q != request id %q", name, idBack, id)
 		}
 		_, err = ioutil.ReadAll(res.Body)
 		if err != nil {
-			t.Fatalf("Slurp error (i=%d): %v", i, err)
+			t.Fatalf("%s: Slurp error: %v", name, err)
 		}
 	}
+
+	// Few 100 responses, making sure we're not off-by-one.
+	for i := 1; i <= numReqs; i++ {
+		req, _ := NewRequest("POST", "http://dummy.tld/", strings.NewReader(reqBody(i)))
+		req.Header.Set("Request-Id", reqID(i))
+		testResponse(req, fmt.Sprintf("100, %d/%d", i, numReqs), 200)
+	}
+
+	// And some other informational 1xx but non-100 responses, to test
+	// we return them but don't re-use the connection.
+	for i := 1; i <= numReqs; i++ {
+		req, _ := NewRequest("POST", "http://other.tld/", strings.NewReader(reqBody(i)))
+		req.Header.Set("X-Want-Response-Code", "123 Sesame Street")
+		testResponse(req, fmt.Sprintf("123, %d/%d", i, numReqs), 123)
+	}
 }
 
 type proxyFromEnvTest struct {