net/http: return appropriate errors from ReadRequest

Fixes #3298

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5783080

src/pkg/net/http/request.go

@@ -455,11 +455,13 @@ func ReadRequest(b *bufio.Reader) (req *Request, err error) {
 	// First line: GET /index.html HTTP/1.0
 	var s string
 	if s, err = tp.ReadLine(); err != nil {
+		return nil, err
+	}
+	defer func() {
 		if err == io.EOF {
 			err = io.ErrUnexpectedEOF
 		}
-		return nil, err
-	}
+	}()
 
 	var f []string
 	if f = strings.SplitN(s, " ", 3); len(f) < 3 {

src/pkg/net/http/request_test.go

@@ -5,6 +5,7 @@
 package http_test
 
 import (
+	"bufio"
 	"bytes"
 	"fmt"
 	"io"
@@ -177,6 +178,24 @@ func TestRequestMultipartCallOrder(t *testing.T) {
 	}
 }
 
+var readRequestErrorTests = []struct {
+	in  string
+	err error
+}{
+	{"GET / HTTP/1.1\r\nheader:foo\r\n\r\n", nil},
+	{"GET / HTTP/1.1\r\nheader:foo\r\n", io.ErrUnexpectedEOF},
+	{"", io.EOF},
+}
+
+func TestReadRequestErrors(t *testing.T) {
+	for i, tt := range readRequestErrorTests {
+		_, err := ReadRequest(bufio.NewReader(strings.NewReader(tt.in)))
+		if err != tt.err {
+			t.Errorf("%d. got error = %v; want %v", i, err, tt.err)
+		}
+	}
+}
+
 func testMissingFile(t *testing.T, req *Request) {
 	f, fh, err := req.FormFile("missing")
 	if f != nil {

src/pkg/net/http/server.go

@@ -601,7 +601,7 @@ func (c *conn) serve() {
 				// while they're still writing their
 				// request.  Undefined behavior.
 				msg = "413 Request Entity Too Large"
-			} else if err == io.ErrUnexpectedEOF {
+			} else if err == io.EOF {
 				break // Don't reply
 			} else if neterr, ok := err.(net.Error); ok && neterr.Timeout() {
 				break // Don't reply