net/http: allow upgrading non keepalive connections

If one was using http.Transport with DisableKeepAlives and trying
to upgrade a connection against net/http's Server, the Server
would not allow a "Connection: Upgrade" header to be written
and instead override it to "Connection: Close" which would
break the handshake.

This change ensures net/http's Server does not override the
connection header for successful protocol switch responses.

Fixes #36381.

Change-Id: I882aad8539e6c87ff5f37c20e20b3a7fa1a30357
GitHub-Last-Rev: dc0de83201dc26236527b68bd49dffc53dd0389b
GitHub-Pull-Request: golang/go#36382
Reviewed-on: https://go-review.googlesource.com/c/go/+/213277
Trust: Emmanuel Odeke <emmanuel@orijtech.com>
Trust: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 53 insertions, 0 deletions

diff --git a/src/net/http/serve_test.go b/src/net/http/serve_test.go
index ba54b31a29..b1bf8e6c5e 100644
--- a/src/net/http/serve_test.go
+++ b/src/net/http/serve_test.go
@@ -6448,3 +6448,56 @@ func BenchmarkResponseStatusLine(b *testing.B) {
 		}
 	})
 }
+func TestDisableKeepAliveUpgrade(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping in short mode")
+	}
+
+	setParallel(t)
+	defer afterTest(t)
+
+	s := httptest.NewUnstartedServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Connection", "Upgrade")
+		w.Header().Set("Upgrade", "someProto")
+		w.WriteHeader(StatusSwitchingProtocols)
+		c, _, err := w.(Hijacker).Hijack()
+		if err != nil {
+			return
+		}
+		defer c.Close()
+
+		io.Copy(c, c)
+	}))
+	s.Config.SetKeepAlivesEnabled(false)
+	s.Start()
+	defer s.Close()
+
+	cl := s.Client()
+	cl.Transport.(*Transport).DisableKeepAlives = true
+
+	resp, err := cl.Get(s.URL)
+	if err != nil {
+		t.Fatalf("failed to perform request: %v", err)
+	}
+	defer resp.Body.Close()
+
+	rwc, ok := resp.Body.(io.ReadWriteCloser)
+	if !ok {
+		t.Fatalf("Response.Body is not a io.ReadWriteCloser: %T", resp.Body)
+	}
+
+	_, err = rwc.Write([]byte("hello"))
+	if err != nil {
+		t.Fatalf("failed to write to body: %v", err)
+	}
+
+	b := make([]byte, 5)
+	_, err = io.ReadFull(rwc, b)
+	if err != nil {
+		t.Fatalf("failed to read from body: %v", err)
+	}
+
+	if string(b) != "hello" {
+		t.Fatalf("unexpected value read from body:\ngot: %q\nwant: %q", b, "hello")
+	}
+}