Update HTTPFallback to handle tls handshake timeout

Signed-off-by: Derek McGowan <derek@mcg.dev>

core/remotes/docker/resolver_test.go

@@ -24,6 +24,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -406,7 +407,7 @@ func TestHTTPFallbackResolver(t *testing.T) {
 		}
 
 		client := &http.Client{
-			Transport: HTTPFallback{http.DefaultTransport},
+			Transport: NewHTTPFallback(http.DefaultTransport),
 		}
 		options := ResolverOptions{
 			Hosts: func(host string) ([]RegistryHost, error) {
@@ -427,6 +428,59 @@ func TestHTTPFallbackResolver(t *testing.T) {
 	runBasicTest(t, "testname", sf)
 }
 
+func TestHTTPFallbackTimeoutResolver(t *testing.T) {
+	sf := func(h http.Handler) (string, ResolverOptions, func()) {
+
+		l, err := net.Listen("tcp", "127.0.0.1:0")
+		if err != nil {
+			t.Fatal(err)
+		}
+		server := &http.Server{
+			Handler:           h,
+			ReadHeaderTimeout: time.Second,
+		}
+		go func() {
+			// Accept first connection but do not do anything with it
+			// to force TLS handshake to timeout. Subsequent connection
+			// will be HTTP and should work.
+			c, err := l.Accept()
+			if err != nil {
+				return
+			}
+			go func() {
+				time.Sleep(time.Second)
+				c.Close()
+			}()
+			server.Serve(l)
+		}()
+		host := l.Addr().String()
+
+		defaultTransport := &http.Transport{
+			TLSHandshakeTimeout: time.Millisecond,
+		}
+		client := &http.Client{
+			Transport: NewHTTPFallback(defaultTransport),
+		}
+
+		options := ResolverOptions{
+			Hosts: func(host string) ([]RegistryHost, error) {
+				return []RegistryHost{
+					{
+						Client:       client,
+						Host:         host,
+						Scheme:       "https",
+						Path:         "/v2",
+						Capabilities: HostCapabilityPull | HostCapabilityResolve | HostCapabilityPush,
+					},
+				}, nil
+			},
+		}
+		return host, options, func() { l.Close() }
+	}
+
+	runBasicTest(t, "testname", sf)
+}
+
 func TestResolveProxy(t *testing.T) {
 	var (
 		ctx  = context.Background()