net/http: refactor body logic in test

This just eliminates some duplication.
Also add a pointer to RFC 1122, in case
this comes up again.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6229044

src/pkg/net/http/serve_test.go

@@ -618,13 +618,6 @@ type serverExpectTest struct {
 	expectedResponse string // expected substring in first line of http response
 }
 
-// forcedBadBody returns whether this test sends an unsolicited body
-// without asking the server's permission and which we know the server
-// will deny (possibly before we finish writing the body).
-func (t serverExpectTest) forcedBadBody() bool {
-	return t.contentLength > 0 && !t.readBody && strings.ToLower(t.expectation) != "100-continue"
-}
-
 var serverExpectTests = []serverExpectTest{
 	// Normal 100-continues, case-insensitive.
 	{100, "100-continue", true, "100 Continue"},
@@ -668,6 +661,11 @@ func TestServerExpect(t *testing.T) {
 			t.Fatalf("Dial: %v", err)
 		}
 		defer conn.Close()
+
+		// Only send the body immediately if we're acting like an HTTP client
+		// that doesn't send 100-continue expectations.
+		writeBody := test.contentLength > 0 && strings.ToLower(test.expectation) != "100-continue"
+
 		go func() {
 			_, err := fmt.Fprintf(conn, "POST /?readbody=%v HTTP/1.1\r\n"+
 				"Connection: close\r\n"+
@@ -678,13 +676,11 @@ func TestServerExpect(t *testing.T) {
 				t.Errorf("On test %#v, error writing request headers: %v", test, err)
 				return
 			}
-			// Only send the body immediately if we're acting like an HTTP client
-			// that doesn't send 100-continue expectations.
-			if test.contentLength > 0 && strings.ToLower(test.expectation) != "100-continue" {
+			if writeBody {
 				body := strings.Repeat("A", test.contentLength)
 				_, err = fmt.Fprint(conn, body)
 				if err != nil {
-					if test.forcedBadBody() {
+					if !test.readBody {
 						// Server likely already hung up on us.
 						// See larger comment below.
 						t.Logf("On test %#v, acceptable error writing request body: %v", test, err)
@@ -697,11 +693,12 @@ func TestServerExpect(t *testing.T) {
 		bufr := bufio.NewReader(conn)
 		line, err := bufr.ReadString('\n')
 		if err != nil {
-			if test.forcedBadBody() {
+			if writeBody && !test.readBody {
 				// This is an acceptable failure due to a possible TCP race:
 				// We were still writing data and the server hung up on us. A TCP
 				// implementation may send a RST if our request body data was known
 				// to be lost, which may trigger our reads to fail.
+				// See RFC 1122 page 88.
 				t.Logf("On test %#v, acceptable error from ReadString: %v", test, err)
 				return
 			}