Add tool to configure runtime settings in docker

This will be used with the upcoming e2e image tests.

PiperOrigin-RevId: 201400832
Change-Id: I49509314e16ea54655ea8060dbf511a04a7a8f79

runsc/tools/dockercfg/BUILD

@@ -0,0 +1,12 @@
+package(licenses = ["notice"])  # Apache 2.0
+
+load("@io_bazel_rules_go//go:def.bzl", "go_binary")
+
+go_binary(
+    name = "dockercfg",
+    srcs = ["dockercfg.go"],
+    visibility = [
+        "//runsc/test:__subpackages__",
+    ],
+    deps = ["@com_github_google_subcommands//:go_default_library"],
+)

runsc/tools/dockercfg/dockercfg.go

@@ -0,0 +1,189 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Helper tool to configure Docker daemon.
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+
+	"context"
+	"flag"
+	"github.com/google/subcommands"
+)
+
+var (
+	configFile = flag.String("config_file", "/etc/docker/daemon.json", "path to Docker daemon config file")
+)
+
+func main() {
+	subcommands.Register(subcommands.HelpCommand(), "")
+	subcommands.Register(subcommands.FlagsCommand(), "")
+	subcommands.Register(&runtimeAdd{}, "")
+	subcommands.Register(&runtimeRemove{}, "")
+
+	// All subcommands must be registered before flag parsing.
+	flag.Parse()
+
+	exitCode := subcommands.Execute(context.Background())
+	os.Exit(int(exitCode))
+}
+
+type runtime struct {
+	Path        string   `json:"path,omitempty"`
+	RuntimeArgs []string `json:"runtimeArgs,omitempty"`
+}
+
+// runtimeAdd implements subcommands.Command.
+type runtimeAdd struct {
+}
+
+// Name implements subcommands.Command.Name.
+func (*runtimeAdd) Name() string {
+	return "runtime-add"
+}
+
+// Synopsis implements subcommands.Command.Synopsis.
+func (*runtimeAdd) Synopsis() string {
+	return "adds a runtime to docker daemon configuration"
+}
+
+// Usage implements subcommands.Command.Usage.
+func (*runtimeAdd) Usage() string {
+	return `runtime-add [flags] <name> <path> [args...]  -- if provided, args are passed as arguments to the runtime
+`
+}
+
+// SetFlags implements subcommands.Command.SetFlags.
+func (*runtimeAdd) SetFlags(*flag.FlagSet) {
+}
+
+// Execute implements subcommands.Command.Execute.
+func (r *runtimeAdd) Execute(_ context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
+	if f.NArg() < 2 {
+		f.Usage()
+		return subcommands.ExitUsageError
+	}
+	name := f.Arg(0)
+	path := f.Arg(1)
+	runtimeArgs := f.Args()[2:]
+
+	fmt.Printf("Adding runtime %q to file %q\n", name, *configFile)
+	c, err := readConfig(*configFile)
+	if err != nil {
+		log.Fatalf("Error reading config file %q: %v", *configFile, err)
+	}
+
+	var rts map[string]interface{}
+	if i, ok := c["runtimes"]; ok {
+		rts = i.(map[string]interface{})
+	} else {
+		rts = make(map[string]interface{})
+		c["runtimes"] = rts
+	}
+	rts[name] = runtime{Path: path, RuntimeArgs: runtimeArgs}
+
+	if err := writeConfig(c, *configFile); err != nil {
+		log.Fatalf("Error writing config file %q: %v", *configFile, err)
+	}
+	return subcommands.ExitSuccess
+}
+
+// runtimeRemove implements subcommands.Command.
+type runtimeRemove struct {
+}
+
+// Name implements subcommands.Command.Name.
+func (*runtimeRemove) Name() string {
+	return "runtime-rm"
+}
+
+// Synopsis implements subcommands.Command.Synopsis.
+func (*runtimeRemove) Synopsis() string {
+	return "removes a runtime from docker daemon configuration"
+}
+
+// Usage implements subcommands.Command.Usage.
+func (*runtimeRemove) Usage() string {
+	return `runtime-rm [flags] <name>
+`
+}
+
+// SetFlags implements subcommands.Command.SetFlags.
+func (*runtimeRemove) SetFlags(*flag.FlagSet) {
+}
+
+// Execute implements subcommands.Command.Execute.
+func (r *runtimeRemove) Execute(_ context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
+	if f.NArg() != 1 {
+		f.Usage()
+		return subcommands.ExitUsageError
+	}
+	name := f.Arg(0)
+
+	fmt.Printf("Removing runtime %q from file %q\n", name, *configFile)
+	c, err := readConfig(*configFile)
+	if err != nil {
+		log.Fatalf("Error reading config file %q: %v", *configFile, err)
+	}
+
+	var rts map[string]interface{}
+	if i, ok := c["runtimes"]; ok {
+		rts = i.(map[string]interface{})
+	} else {
+		log.Fatalf("runtime %q not found", name)
+	}
+	if _, ok := rts[name]; !ok {
+		log.Fatalf("runtime %q not found", name)
+	}
+	delete(rts, name)
+
+	if err := writeConfig(c, *configFile); err != nil {
+		log.Fatalf("Error writing config file %q: %v", *configFile, err)
+	}
+	return subcommands.ExitSuccess
+}
+
+func readConfig(path string) (map[string]interface{}, error) {
+	configBytes, err := ioutil.ReadFile(path)
+	if err != nil && !os.IsNotExist(err) {
+		return nil, err
+	}
+	c := make(map[string]interface{})
+	if len(configBytes) > 0 {
+		if err := json.Unmarshal(configBytes, &c); err != nil {
+			return nil, err
+		}
+	}
+	return c, nil
+}
+
+func writeConfig(c map[string]interface{}, path string) error {
+	b, err := json.MarshalIndent(c, "", "    ")
+	if err != nil {
+		return err
+	}
+
+	if err := os.Rename(path, path+"~"); err != nil && !os.IsNotExist(err) {
+		return fmt.Errorf("error renaming config file %q: %v", path, err)
+	}
+	if err := ioutil.WriteFile(path, b, 0644); err != nil {
+		return fmt.Errorf("error writing config file %q: %v", path, err)
+	}
+	return nil
+}