feat: resolve special ip host-gateway

Signed-off-by: Ziwen Ning <ningziwe@amazon.com>

cmd/nerdctl/container_run.go

@@ -57,7 +57,8 @@ import (
 	"github.com/containerd/nerdctl/pkg/referenceutil"
 	"github.com/containerd/nerdctl/pkg/strutil"
 	"github.com/containerd/nerdctl/pkg/taskutil"
-	dopts "github.com/docker/cli/opts"
+	dockercliopts "github.com/docker/cli/opts"
+	dockerops "github.com/docker/docker/opts"
 	"github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
@@ -707,10 +708,25 @@ func createContainer(ctx context.Context, cmd *cobra.Command, client *containerd
 		return nil, nil, err
 	}
 	extraHosts = strutil.DedupeStrSlice(extraHosts)
-	for _, host := range extraHosts {
-		if _, err := dopts.ValidateExtraHost(host); err != nil {
+	for i, host := range extraHosts {
+		if _, err := dockercliopts.ValidateExtraHost(host); err != nil {
 			return nil, nil, err
 		}
+		parts := strings.SplitN(host, ":", 2)
+		// If the IP Address is a string called "host-gateway", replace this value with the IP address stored
+		// in the daemon level HostGateway IP config variable.
+		if parts[1] == dockerops.HostGatewayName {
+			gateway, err := cmd.Flags().GetString("host-gateway-ip")
+			logrus.Info("gateway: " + gateway) // TODO: remove in final PR
+			if err != nil {
+				return nil, nil, err
+			}
+			if gateway == "" {
+				return nil, nil, fmt.Errorf("unable to derive the IP value for host-gateway")
+			}
+			parts[1] = gateway
+			extraHosts[i] = fmt.Sprintf(`%s:%s`, parts[0], parts[1])
+		}
 	}
 	internalLabels.extraHosts = extraHosts
 
@@ -995,7 +1011,7 @@ func readKVStringsMapfFromLabel(cmd *cobra.Command) (map[string]string, error) {
 		return nil, err
 	}
 	labelsFilePath = strutil.DedupeStrSlice(labelsFilePath)
-	labels, err := dopts.ReadKVStrings(labelsFilePath, labelsMap)
+	labels, err := dockercliopts.ReadKVStrings(labelsFilePath, labelsMap)
 	if err != nil {
 		return nil, err
 	}

cmd/nerdctl/flagutil.go

@@ -70,6 +70,10 @@ func processRootCmdFlags(cmd *cobra.Command) (types.GlobalCommandOptions, error)
 	if err != nil {
 		return types.GlobalCommandOptions{}, err
 	}
+	hostGatewayIP, err := cmd.Flags().GetString("host-gateway-ip")
+	if err != nil {
+		return types.GlobalCommandOptions{}, err
+	}
 	return types.GlobalCommandOptions{
 		Debug:            debug,
 		DebugFull:        debugFull,
@@ -83,5 +87,6 @@ func processRootCmdFlags(cmd *cobra.Command) (types.GlobalCommandOptions, error)
 		InsecureRegistry: insecureRegistry,
 		HostsDir:         hostsDir,
 		Experimental:     experimental,
+		HostGatewayIP:    hostGatewayIP,
 	}, nil
 }

cmd/nerdctl/main.go

@@ -171,6 +171,7 @@ func initRootCmdFlags(rootCmd *cobra.Command, tomlPath string) (*pflag.FlagSet,
 	rootCmd.PersistentFlags().StringSlice("hosts-dir", cfg.HostsDir, "A directory that contains <HOST:PORT>/hosts.toml (containerd style) or <HOST:PORT>/{ca.cert, cert.pem, key.pem} (docker style)")
 	// Experimental enable experimental feature, see in https://github.com/containerd/nerdctl/blob/main/docs/experimental.md
 	AddPersistentBoolFlag(rootCmd, "experimental", nil, nil, cfg.Experimental, "NERDCTL_EXPERIMENTAL", "Control experimental: https://github.com/containerd/nerdctl/blob/main/docs/experimental.md")
+	rootCmd.PersistentFlags().String("host-gateway-ip", cfg.HostGatewayIP, "IP address that the special 'host-gateway' string in --add-host resolves to. Defaults to the IP address of the default bridge")
 	return aliasToBeInherited, nil
 }
 

pkg/config/config.go

@@ -38,6 +38,7 @@ type Config struct {
 	InsecureRegistry bool     `toml:"insecure_registry"`
 	HostsDir         []string `toml:"hosts_dir"`
 	Experimental     bool     `toml:"experimental"`
+	HostGatewayIP    string   `toml:"host_gateway_ip"`
 }
 
 // New creates a default Config object statically,
@@ -56,5 +57,6 @@ func New() *Config {
 		InsecureRegistry: false,
 		HostsDir:         ncdefaults.HostsDirs(),
 		Experimental:     true,
+		HostGatewayIP:    "",
 	}
 }