http2: avoid Transport hang with Connection: close and AllowHTTP

neild · neild · commit 9617c6335bca · 2024-06-12T20:39:16.000Z
CL 111835 changed Transport stream ID numbering to start at stream 3 when AllowHTTP is set. This was based on a misunderstanding: When a connection upgrades an HTTP/1.1 request to HTTP/2, the initial HTTP/1.1 request occupies stream 1. However, Transport does not perform HTTP protocol upgrades. When using a Transport to send unencrypted HTTP/2 requests, the entire connection uses HTTP/2, the first request is sent as HTTP/2, and there is no reason not to use stream 1 for this request. Starting from stream 3 is mostly harmless, but ClientConn.idleStateLocked assumes that client streams start from 1. This causes it to misidentify new single-use connections as having already sent a request (when AllowHTTP is set), and therefore not suitable for use. Revert to always starting stream IDs at 1. Fixes golang/go#67671 Change-Id: I97c89de4ae49623d916f9dbd200f8252d2fd4247 Reviewed-on: https://go-review.googlesource.com/c/net/+/591275 LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Jonathan Amsterdam <jba@google.com>
diff --git a/http2/transport.go b/http2/transport.go
@@ -827,10 +827,6 @@ func (t *Transport) newClientConn(c net.Conn, singleUse bool) (*ClientConn, erro
 	cc.henc.SetMaxDynamicTableSizeLimit(t.maxEncoderHeaderTableSize())
 	cc.peerMaxHeaderTableSize = initialHeaderTableSize
 
-	if t.AllowHTTP {
-		cc.nextStreamID = 3
-	}
-
 	if cs, ok := c.(connectionStater); ok {
 		state := cs.ConnectionState()
 		cc.tlsState = &state
diff --git a/http2/transport_test.go b/http2/transport_test.go
@@ -5401,3 +5401,23 @@ func TestIssue66763Race(t *testing.T) {
 
 	<-donec
 }
+
+// Issue 67671: Sending a Connection: close request on a Transport with AllowHTTP
+// set caused a the transport to wedge.
+func TestIssue67671(t *testing.T) {
+	ts := newTestServer(t, func(w http.ResponseWriter, r *http.Request) {})
+	tr := &Transport{
+		TLSClientConfig: tlsConfigInsecure,
+		AllowHTTP:       true,
+	}
+	defer tr.CloseIdleConnections()
+	req, _ := http.NewRequest("GET", ts.URL, nil)
+	req.Close = true
+	for i := 0; i < 2; i++ {
+		res, err := tr.RoundTrip(req)
+		if err != nil {
+			t.Fatal(err)
+		}
+		res.Body.Close()
+	}
+}
