[release-branch.go1.15] 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 #45076.
Updates #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>
Reviewed-on: https://go-review.googlesource.com/c/go/+/304210
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Trust: Emmanuel Odeke <emmanuel@orijtech.com>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>

diff --git a/src/net/http/omithttp2.go b/src/net/http/omithttp2.go
index 7e2f4925798f81a1bf37847f36eb992dce600e59..c8f5c28a59135d935c2a339c7c38a5684fc2950b 100644 (file)
--- a/src/net/http/omithttp2.go
+++ b/src/net/http/omithttp2.go
@@ -32,10 +32,6 @@ type http2Transport struct {
 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) }

diff --git a/src/net/http/transport.go b/src/net/http/transport.go
index 6e430b9885fcb9c20e0ec1cdf6bba20052d82d6c..88d15a59194916f6c4433072f3cb907187345b8a 100644 (file)
--- a/src/net/http/transport.go
+++ b/src/net/http/transport.go
@@ -1531,6 +1531,10 @@ func (pconn *persistConn) addTLS(name string, trace *httptrace.ClientTrace) erro
        return nil
 }
 
+type erringRoundTripper interface {
+       RoundTripErr() error
+}
+
 func (t *Transport) dialConn(ctx context.Context, cm connectMethod) (pconn *persistConn, err error) {
        pconn = &persistConn{
                t:             t,
@@ -1697,9 +1701,9 @@ func (t *Transport) dialConn(ctx context.Context, cm connectMethod) (pconn *pers
        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
                }