util: check for localhost for plainhttp

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

cmd/buildkitd/config/config.go

@@ -43,7 +43,7 @@ type GRPCConfig struct {
 
 type RegistryConfig struct {
 	Mirrors   []string `toml:"mirrors"`
-	PlainHTTP bool     `toml:"http"`
+	PlainHTTP *bool    `toml:"http"`
 }
 
 type TLSConfig struct {

cmd/buildkitd/config/config_test.go

@@ -101,7 +101,7 @@ searchDomains=["example.com"]
 	require.Equal(t, 1, len(cfg.Workers.Containerd.GCPolicy[0].Filters))
 	require.Equal(t, 0, len(cfg.Workers.Containerd.GCPolicy[1].Filters))
 
-	require.Equal(t, cfg.Registries["docker.io"].PlainHTTP, true)
+	require.Equal(t, *cfg.Registries["docker.io"].PlainHTTP, true)
 	require.Equal(t, cfg.Registries["docker.io"].Mirrors[0], "hub.docker.io")
 
 	require.NotNil(t, cfg.DNS)

util/resolver/resolver.go

@@ -2,6 +2,7 @@ package resolver
 
 import (
 	"math/rand"
+	"strings"
 
 	"github.com/containerd/containerd/remotes/docker"
 	"github.com/docker/distribution/reference"
@@ -10,7 +11,7 @@ import (
 
 type RegistryConf struct {
 	Mirrors   []string
-	PlainHTTP bool
+	PlainHTTP *bool
 }
 
 type ResolveOptionsFunc func(string) docker.ResolverOptions
@@ -32,13 +33,21 @@ func NewResolveOptionsFunc(m map[string]RegistryConf) ResolveOptionsFunc {
 			return def
 		}
 
+		var mirrorHost string
 		if len(c.Mirrors) > 0 {
+			mirrorHost = c.Mirrors[rand.Intn(len(c.Mirrors))]
 			def.Host = func(string) (string, error) {
-				return c.Mirrors[rand.Intn(len(c.Mirrors))], nil
+				return mirrorHost, nil
 			}
 		}
 
-		def.PlainHTTP = c.PlainHTTP
+		if c.PlainHTTP != nil {
+			def.PlainHTTP = *c.PlainHTTP
+		} else {
+			if mirrorHost == "localhost" || strings.HasPrefix(mirrorHost, "localhost:") {
+				def.PlainHTTP = true
+			}
+		}
 
 		return def
 	}