commit 8381408048018aa2b6eec874f3161b4641191522
author Michael Fraenkel <michael.fraenkel@gmail.com> Thu Jul 16 21:30:12 2020 -0600
committer Emmanuel Odeke <emm.odeke@gmail.com> Tue Aug 25 20:04:27 2020 +0000
tree 3e70ff2b3e3eac4cee4ab3c26b726c1f1472dbce
parent 3d774611feee49aa44b4f5ed65d40497a47ad4c8

net/http: fix detection of Roundtrippers that always error

CL 220905 added code to identify alternate transports that always error
by using http2erringRoundTripper. This does not work when the transport
is from another package, e.g., http2.erringRoundTripper.
Expose a new method that allow detection of such a RoundTripper.
Switch to an interface that is both a RoundTripper and can return the
underlying error.

Fixes #40213

Change-Id: I170739857ab9e99dffb5fa55c99b24b23c2f9c54
Reviewed-on: https://go-review.googlesource.com/c/go/+/243258
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/net/http/omithttp2.go

diff --git a/src/net/http/omithttp2.go b/src/net/http/omithttp2.go
index 7e2f492..c8f5c28 100644
--- a/src/net/http/omithttp2.go
+++ b/src/net/http/omithttp2.go
@@ -32,10 +32,6 @@
 func (*http2Transport) RoundTrip(*Request) (*Response, error) { panic(noHTTP2) }
 func (*http2Transport) CloseIdleConnections()                 {}
 
-type http2erringRoundTripper struct{ err error }
-
-func (http2erringRoundTripper) RoundTrip(*Request) (*Response, error) { panic(noHTTP2) }
-
 type http2noDialH2RoundTripper struct{}
 
 func (http2noDialH2RoundTripper) RoundTrip(*Request) (*Response, error) { panic(noHTTP2) }

src/net/http/transport.go

diff --git a/src/net/http/transport.go b/src/net/http/transport.go
index d37b52b..c23042b 100644
--- a/src/net/http/transport.go
+++ b/src/net/http/transport.go
@@ -1528,6 +1528,10 @@
 	return nil
 }
 
+type erringRoundTripper interface {
+	RoundTripErr() error
+}
+
 func (t *Transport) dialConn(ctx context.Context, cm connectMethod) (pconn *persistConn, err error) {
 	pconn = &persistConn{
 		t:             t,
@@ -1694,9 +1698,9 @@
 	if s := pconn.tlsState; s != nil && s.NegotiatedProtocolIsMutual && s.NegotiatedProtocol != "" {
 		if next, ok := t.TLSNextProto[s.NegotiatedProtocol]; ok {
 			alt := next(cm.targetAddr, pconn.conn.(*tls.Conn))
-			if e, ok := alt.(http2erringRoundTripper); ok {
+			if e, ok := alt.(erringRoundTripper); ok {
 				// pconn.conn was closed by next (http2configureTransport.upgradeFn).
-				return nil, e.err
+				return nil, e.RoundTripErr()
 			}
 			return &persistConn{t: t, cacheKey: pconn.cacheKey, alt: alt}, nil
 		}