Add a no-op GRPC responder service to the podman system service

Add a bare minimum GRPC service to the podman system service socket.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

Makefile

@@ -239,11 +239,11 @@ all: binaries docs
 
 .PHONY: binaries
 ifeq ($(GOOS),freebsd)
-binaries: podman podman-remote ## (FreeBSD) Build podman and podman-remote binaries
+binaries: podman podman-remote podman-testing ## (FreeBSD) Build podman, podman-remote, and podman-testing binaries
 else ifneq (, $(findstring $(GOOS),darwin windows))
 binaries: podman-remote ## (macOS/Windows) Build podman-remote (client) only binaries
 else
-binaries: podman podman-remote podman-testing podmansh rootlessport quadlet ## (Linux) Build podman, podman-remote and rootlessport binaries quadlet
+binaries: podman podman-remote podman-testing podmansh rootlessport quadlet ## (Linux) Build podman, podman-remote, podmansh, rootlessport, and quadlet binaries
 endif
 
 # Extract text following double-# for targets, as their description for
@@ -478,7 +478,7 @@ $(SRCBINDIR)/podman-testing: $(SOURCES) go.mod go.sum
 		-o $@ ./cmd/podman-testing
 
 .PHONY: podman-testing
-podman-testing: bin/podman-testing
+podman-testing: $(SRCBINDIR)/podman-testing
 
 ###
 ### Secondary binary-build targets

cmd/podman-testing/call.go

@@ -0,0 +1,152 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"strings"
+
+	"github.com/containers/podman/v6/pkg/api/grpcpb"
+	"github.com/containers/podman/v6/pkg/bindings"
+	"github.com/containers/podman/v6/pkg/domain/entities"
+	"github.com/spf13/cobra"
+	"go.podman.io/common/pkg/completion"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+	reflectionv1 "google.golang.org/grpc/reflection/grpc_reflection_v1"
+)
+
+var (
+	noopDescription = `Call the no-op GRPC endpoint.`
+	noopCmd         = &cobra.Command{
+		Use:               "noop [arg]",
+		Args:              cobra.MaximumNArgs(1),
+		Short:             "Call the no-op GRPC endpoint",
+		Long:              noopDescription,
+		RunE:              noop,
+		ValidArgsFunction: completion.AutocompleteNone,
+		Example:           `podman-testing noop`,
+	}
+	lsDescription = `List GRPC endpoints.`
+	lsCmd         = &cobra.Command{
+		Use:               "ls [arg]",
+		Args:              cobra.MaximumNArgs(1),
+		Short:             "Call an RPC endpoint",
+		Long:              lsDescription,
+		RunE:              ls,
+		ValidArgsFunction: completion.AutocompleteNone,
+		Example:           `podman-testing ls`,
+	}
+)
+
+func init() {
+	mainCmd.AddCommand(noopCmd)
+	mainCmd.AddCommand(lsCmd)
+}
+
+func ls(_ *cobra.Command, args []string) error {
+	if podmanConfig.EngineMode != entities.TunnelMode {
+		return errors.New("only available in remote mode")
+	}
+	ctx, grpcClient, err := getGrpcClient()
+	if err != nil {
+		return fmt.Errorf("setting up grpc client for podman service: %w", err)
+	}
+	if err != nil {
+		return fmt.Errorf("setting up grpc client for podman service: %w", err)
+	}
+	reflectionClient := reflectionv1.NewServerReflectionClient(grpcClient)
+	if reflectionClient == nil {
+		return fmt.Errorf("setting up client for reflection grpc service: %w", err)
+	}
+	info, err := reflectionClient.ServerReflectionInfo(ctx)
+	if err != nil {
+		return fmt.Errorf("reflection grpc service: %w", err)
+	}
+	ls := ""
+	if len(args) > 1 {
+		ls = args[1]
+	}
+	err = info.Send(&reflectionv1.ServerReflectionRequest{
+		MessageRequest: &reflectionv1.ServerReflectionRequest_ListServices{
+			ListServices: ls,
+		},
+	})
+	if err != nil {
+		return fmt.Errorf("reflection grpc service: %w", err)
+	}
+	err = info.CloseSend()
+	if err != nil {
+		return fmt.Errorf("reflection grpc service: %w", err)
+	}
+	var response reflectionv1.ServerReflectionResponse
+	err = info.RecvMsg(&response)
+	for err == nil {
+		var out []byte
+		out, err = json.Marshal(response.GetListServicesResponse())
+		if err != nil {
+			return fmt.Errorf("encoding response from grpc service: %w", err)
+		}
+		fmt.Println(string(out))
+		response.Reset()
+		err = info.RecvMsg(&response)
+	}
+	if !errors.Is(err, io.EOF) {
+		return fmt.Errorf("unexpected grpc protocol error: %w", err)
+	}
+	return nil
+}
+
+func noop(_ *cobra.Command, args []string) error {
+	var out []byte
+	switch podmanConfig.EngineMode {
+	case entities.TunnelMode:
+		ctx, grpcClient, err := getGrpcClient()
+		if err != nil {
+			return fmt.Errorf("setting up grpc client for podman service: %w", err)
+		}
+		noopClient := grpcpb.NewNoopClient(grpcClient)
+		if noopClient == nil {
+			return fmt.Errorf("setting up client for noop grpc service: %w", err)
+		}
+		var request grpcpb.NoopRequest
+		if encoded := strings.Join(args, ""); len(encoded) > 0 {
+			if err := json.Unmarshal([]byte(encoded), &request); err != nil {
+				return fmt.Errorf("parsing client request contents for noop grpc service: %w", err)
+			}
+		}
+		response, err := noopClient.Noop(ctx, &request)
+		if err != nil {
+			return fmt.Errorf("noop grpc service: %w", err)
+		}
+		out, err = json.Marshal(response)
+		if err != nil {
+			return fmt.Errorf("encoding response from grpc service: %w", err)
+		}
+	default:
+		return errors.New("only available in remote mode")
+	}
+	fmt.Println(string(out))
+	return nil
+}
+
+func getGrpcClient() (context.Context, *grpc.ClientConn, error) {
+	ctx, err := bindings.NewConnection(mainContext, podmanConfig.URI)
+	if err != nil {
+		return nil, nil, fmt.Errorf("connecting to podman service: %w", err)
+	}
+	client, err := bindings.GetClient(ctx)
+	if err != nil {
+		return nil, nil, fmt.Errorf("obtaining client handle for podman service: %w", err)
+	}
+	onlyPodmanSystemServiceDialer := grpc.WithContextDialer(func(ctx context.Context, _ string) (net.Conn, error) { return client.GetDialer(ctx) })
+	withoutEncryption := grpc.WithTransportCredentials(insecure.NewCredentials())
+	grpcClient, err := grpc.NewClient(podmanConfig.URI, onlyPodmanSystemServiceDialer, withoutEncryption)
+	if err != nil {
+		return nil, nil, fmt.Errorf("setting up grpc client for podman service: %w", err)
+	}
+	return ctx, grpcClient, err
+}

cmd/podman-testing/create.go

@@ -1,4 +1,4 @@
-//go:build !remote
+//go:build (linux || freebsd) && !remote
 
 package main
 
@@ -20,7 +20,7 @@ var (
 		Long:              createStorageLayerDescription,
 		RunE:              createStorageLayer,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing create-storage-layer`,
+		Example:           `podman-testing create-storage-layer`,
 	}
 
 	createStorageLayerOpts entities.CreateStorageLayerOptions
@@ -33,7 +33,7 @@ var (
 		Long:              createLayerDescription,
 		RunE:              createLayer,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing create-layer`,
+		Example:           `podman-testing create-layer`,
 	}
 
 	createLayerOpts entities.CreateLayerOptions
@@ -46,7 +46,7 @@ var (
 		Long:              createImageDescription,
 		RunE:              createImage,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing create-image`,
+		Example:           `podman-testing create-image`,
 	}
 
 	createImageOpts entities.CreateImageOptions
@@ -59,7 +59,7 @@ var (
 		Long:              createContainerDescription,
 		RunE:              createContainer,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing create-container`,
+		Example:           `podman-testing create-container`,
 	}
 
 	createContainerOpts entities.CreateContainerOptions

cmd/podman-testing/data.go

@@ -1,4 +1,4 @@
-//go:build !remote
+//go:build (linux || freebsd) && !remote
 
 package main
 
@@ -21,7 +21,7 @@ var (
 		Long:              createLayerDataDescription,
 		RunE:              createLayerData,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing create-layer-data`,
+		Example:           `podman-testing create-layer-data`,
 	}
 
 	createLayerDataOpts  entities.CreateLayerDataOptions
@@ -37,7 +37,7 @@ var (
 		Long:              createImageDataDescription,
 		RunE:              createImageData,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing create-image-data`,
+		Example:           `podman-testing create-image-data`,
 	}
 
 	createImageDataOpts  entities.CreateImageDataOptions
@@ -53,7 +53,7 @@ var (
 		Long:              createContainerDataDescription,
 		RunE:              createContainerData,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing create-container-data`,
+		Example:           `podman-testing create-container-data`,
 	}
 
 	createContainerDataOpts  entities.CreateContainerDataOptions
@@ -69,7 +69,7 @@ var (
 		Long:              modifyLayerDataDescription,
 		RunE:              modifyLayerData,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing modify-layer-data`,
+		Example:           `podman-testing modify-layer-data`,
 	}
 
 	modifyLayerDataOpts  entities.ModifyLayerDataOptions
@@ -84,7 +84,7 @@ var (
 		Long:              modifyImageDataDescription,
 		RunE:              modifyImageData,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing modify-image-data`,
+		Example:           `podman-testing modify-image-data`,
 	}
 
 	modifyImageDataOpts  entities.ModifyImageDataOptions
@@ -99,7 +99,7 @@ var (
 		Long:              modifyContainerDataDescription,
 		RunE:              modifyContainerData,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing modify-container-data`,
+		Example:           `podman-testing modify-container-data`,
 	}
 
 	modifyContainerDataOpts  entities.ModifyContainerDataOptions
@@ -114,7 +114,7 @@ var (
 		Long:              removeLayerDataDescription,
 		RunE:              removeLayerData,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing remove-layer-data`,
+		Example:           `podman-testing remove-layer-data`,
 	}
 
 	removeLayerDataOpts entities.RemoveLayerDataOptions
@@ -127,7 +127,7 @@ var (
 		Long:              removeImageDataDescription,
 		RunE:              removeImageData,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing remove-image-data`,
+		Example:           `podman-testing remove-image-data`,
 	}
 
 	removeImageDataOpts entities.RemoveImageDataOptions
@@ -140,7 +140,7 @@ var (
 		Long:              removeContainerDataDescription,
 		RunE:              removeContainerData,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing remove-container-data`,
+		Example:           `podman-testing remove-container-data`,
 	}
 
 	removeContainerDataOpts entities.RemoveContainerDataOptions

cmd/podman-testing/layer.go

@@ -1,4 +1,4 @@
-//go:build !remote
+//go:build (linux || freebsd) && !remote
 
 package main
 
@@ -21,7 +21,7 @@ var (
 		Long:              populateLayerDescription,
 		RunE:              populateLayer,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing populate-layer`,
+		Example:           `podman-testing populate-layer`,
 	}
 
 	populateLayerOpts entities.PopulateLayerOptions
@@ -35,7 +35,7 @@ var (
 		Long:              modifyLayerDescription,
 		RunE:              modifyLayer,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing modify-layer`,
+		Example:           `podman-testing modify-layer`,
 	}
 
 	modifyLayerOpts entities.ModifyLayerOptions

cmd/podman-testing/main.go

@@ -1,5 +1,3 @@
-//go:build !remote
-
 package main
 
 import (
@@ -11,13 +9,10 @@ import (
 	"syscall"
 
 	_ "github.com/containers/podman/v6/cmd/podman/completion"
-	ientities "github.com/containers/podman/v6/internal/domain/entities"
-	"github.com/containers/podman/v6/internal/domain/infra"
 	"github.com/containers/podman/v6/pkg/domain/entities"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 	"go.podman.io/common/pkg/config"
-	"go.podman.io/storage"
 	"go.podman.io/storage/pkg/reexec"
 	"go.podman.io/storage/pkg/unshare"
 )
@@ -40,9 +35,7 @@ var (
 	}
 	mainContext    = context.Background()
 	podmanConfig   entities.PodmanConfig
-	globalStorageOptions storage.StoreOptions
 	globalLogLevel string
-	testingEngine        ientities.TestingEngine
 )
 
 func init() {
@@ -80,18 +73,9 @@ func before() error {
 	}
 	podmanConfig.ContainersConf = containersConf
 
-	podmanConfig.StorageDriver = globalStorageOptions.GraphDriverName
-	podmanConfig.GraphRoot = globalStorageOptions.GraphRoot
-	podmanConfig.Runroot = globalStorageOptions.RunRoot
-	podmanConfig.ImageStore = globalStorageOptions.ImageStore
-	podmanConfig.StorageOpts = globalStorageOptions.GraphDriverOptions
-	podmanConfig.TransientStore = globalStorageOptions.TransientStore
-
-	te, err := infra.NewTestingEngine(&podmanConfig)
-	if err != nil {
-		return fmt.Errorf("initializing libpod: %w", err)
+	if err := testingEngineBefore(&podmanConfig); err != nil {
+		return fmt.Errorf("setting up testing engine: %w", err)
 	}
-	testingEngine = te
 	return nil
 }
 

cmd/podman-testing/remove.go

@@ -1,4 +1,4 @@
-//go:build !remote
+//go:build (linux || freebsd) && !remote
 
 package main
 
@@ -20,7 +20,7 @@ var (
 		Long:              removeStorageLayerDescription,
 		RunE:              removeStorageLayer,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing remove-storage-layer`,
+		Example:           `podman-testing remove-storage-layer`,
 	}
 
 	removeStorageLayerOpts entities.RemoveStorageLayerOptions
@@ -33,7 +33,7 @@ var (
 		Long:              removeLayerDescription,
 		RunE:              removeLayer,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing remove-layer`,
+		Example:           `podman-testing remove-layer`,
 	}
 
 	removeLayerOpts entities.RemoveLayerOptions
@@ -46,7 +46,7 @@ var (
 		Long:              removeImageDescription,
 		RunE:              removeImage,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing remove-image`,
+		Example:           `podman-testing remove-image`,
 	}
 
 	removeImageOpts entities.RemoveImageOptions
@@ -59,7 +59,7 @@ var (
 		Long:              removeContainerDescription,
 		RunE:              removeContainer,
 		ValidArgsFunction: completion.AutocompleteNone,
-		Example:           `podman testing remove-container`,
+		Example:           `podman-testing remove-container`,
 	}
 
 	removeContainerOpts entities.RemoveContainerOptions

cmd/podman-testing/store_supported.go

@@ -6,14 +6,18 @@ import (
 	"fmt"
 	"os"
 
+	ientities "github.com/containers/podman/v6/internal/domain/entities"
+	"github.com/containers/podman/v6/internal/domain/infra"
 	"github.com/containers/podman/v6/pkg/domain/entities"
 	"go.podman.io/storage"
 	"go.podman.io/storage/types"
 )
 
 var (
+	globalStorageOptions storage.StoreOptions
 	globalStore          storage.Store
 	engineMode           = entities.ABIMode
+	testingEngine        ientities.TestingEngine
 )
 
 func init() {
@@ -52,6 +56,7 @@ func storeBefore() error {
 	} else {
 		engineMode = entities.ABIMode
 	}
+	podmanConfig.EngineMode = engineMode
 	return nil
 }
 
@@ -62,3 +67,14 @@ func storeAfter() error {
 	}
 	return nil
 }
+
+func testingEngineBefore(podmanConfig *entities.PodmanConfig) (err error) {
+	podmanConfig.StorageDriver = globalStorageOptions.GraphDriverName
+	podmanConfig.GraphRoot = globalStorageOptions.GraphRoot
+	podmanConfig.Runroot = globalStorageOptions.RunRoot
+	podmanConfig.ImageStore = globalStorageOptions.ImageStore
+	podmanConfig.StorageOpts = globalStorageOptions.GraphDriverOptions
+	podmanConfig.TransientStore = globalStorageOptions.TransientStore
+	testingEngine, err = infra.NewTestingEngine(podmanConfig)
+	return err
+}

cmd/podman-testing/store_unsupported.go

@@ -0,0 +1,23 @@
+//go:build !(linux || freebsd) || remote
+
+package main
+
+import (
+	"github.com/containers/podman/v6/pkg/domain/entities"
+)
+
+var (
+	engineMode = entities.TunnelMode
+)
+
+func storeBefore() error {
+	return nil
+}
+
+func storeAfter() error {
+	return nil
+}
+
+func testingEngineBefore(_ *entities.PodmanConfig) (err error) {
+	return nil
+}

pkg/api/grpcpb/build.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+set -e
+cd $(dirname ${BASH_SOURCE[0]})
+TOP=../../..
+PATH=${TOP}/test/tools/build:${PATH}
+set -x
+for proto in *.proto ; do
+	protoc \
+		--go_opt=paths=source_relative --go_out . \
+		--go-grpc_opt=paths=source_relative --go-grpc_out . \
+	${proto}
+done

pkg/api/grpcpb/noop.pb.go

@@ -0,0 +1,174 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// versions:
+// 	protoc-gen-go v1.36.10
+// 	protoc        v3.19.6
+// source: noop.proto
+
+package grpcpb
+
+import (
+	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
+	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
+	reflect "reflect"
+	sync "sync"
+	unsafe "unsafe"
+)
+
+const (
+	// Verify that this generated code is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
+	// Verify that runtime/protoimpl is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
+)
+
+type NoopRequest struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	Ignored       string                 `protobuf:"bytes,1,opt,name=ignored,proto3" json:"ignored,omitempty"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *NoopRequest) Reset() {
+	*x = NoopRequest{}
+	mi := &file_noop_proto_msgTypes[0]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *NoopRequest) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*NoopRequest) ProtoMessage() {}
+
+func (x *NoopRequest) ProtoReflect() protoreflect.Message {
+	mi := &file_noop_proto_msgTypes[0]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use NoopRequest.ProtoReflect.Descriptor instead.
+func (*NoopRequest) Descriptor() ([]byte, []int) {
+	return file_noop_proto_rawDescGZIP(), []int{0}
+}
+
+func (x *NoopRequest) GetIgnored() string {
+	if x != nil {
+		return x.Ignored
+	}
+	return ""
+}
+
+type NoopResponse struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	Ignored       string                 `protobuf:"bytes,1,opt,name=ignored,proto3" json:"ignored,omitempty"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *NoopResponse) Reset() {
+	*x = NoopResponse{}
+	mi := &file_noop_proto_msgTypes[1]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *NoopResponse) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*NoopResponse) ProtoMessage() {}
+
+func (x *NoopResponse) ProtoReflect() protoreflect.Message {
+	mi := &file_noop_proto_msgTypes[1]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use NoopResponse.ProtoReflect.Descriptor instead.
+func (*NoopResponse) Descriptor() ([]byte, []int) {
+	return file_noop_proto_rawDescGZIP(), []int{1}
+}
+
+func (x *NoopResponse) GetIgnored() string {
+	if x != nil {
+		return x.Ignored
+	}
+	return ""
+}
+
+var File_noop_proto protoreflect.FileDescriptor
+
+const file_noop_proto_rawDesc = "" +
+	"\n" +
+	"\n" +
+	"noop.proto\x12\fio.podman.v1\"'\n" +
+	"\vNoopRequest\x12\x18\n" +
+	"\aignored\x18\x01 \x01(\tR\aignored\"(\n" +
+	"\fNoopResponse\x12\x18\n" +
+	"\aignored\x18\x01 \x01(\tR\aignored2E\n" +
+	"\x04Noop\x12=\n" +
+	"\x04Noop\x12\x19.io.podman.v1.NoopRequest\x1a\x1a.io.podman.v1.NoopResponseB0Z.github.com/containers/podman/v6/pkg/api/grpcpbb\x06proto3"
+
+var (
+	file_noop_proto_rawDescOnce sync.Once
+	file_noop_proto_rawDescData []byte
+)
+
+func file_noop_proto_rawDescGZIP() []byte {
+	file_noop_proto_rawDescOnce.Do(func() {
+		file_noop_proto_rawDescData = protoimpl.X.CompressGZIP(unsafe.Slice(unsafe.StringData(file_noop_proto_rawDesc), len(file_noop_proto_rawDesc)))
+	})
+	return file_noop_proto_rawDescData
+}
+
+var file_noop_proto_msgTypes = make([]protoimpl.MessageInfo, 2)
+var file_noop_proto_goTypes = []any{
+	(*NoopRequest)(nil),  // 0: io.podman.v1.NoopRequest
+	(*NoopResponse)(nil), // 1: io.podman.v1.NoopResponse
+}
+var file_noop_proto_depIdxs = []int32{
+	0, // 0: io.podman.v1.Noop.Noop:input_type -> io.podman.v1.NoopRequest
+	1, // 1: io.podman.v1.Noop.Noop:output_type -> io.podman.v1.NoopResponse
+	1, // [1:2] is the sub-list for method output_type
+	0, // [0:1] is the sub-list for method input_type
+	0, // [0:0] is the sub-list for extension type_name
+	0, // [0:0] is the sub-list for extension extendee
+	0, // [0:0] is the sub-list for field type_name
+}
+
+func init() { file_noop_proto_init() }
+func file_noop_proto_init() {
+	if File_noop_proto != nil {
+		return
+	}
+	type x struct{}
+	out := protoimpl.TypeBuilder{
+		File: protoimpl.DescBuilder{
+			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
+			RawDescriptor: unsafe.Slice(unsafe.StringData(file_noop_proto_rawDesc), len(file_noop_proto_rawDesc)),
+			NumEnums:      0,
+			NumMessages:   2,
+			NumExtensions: 0,
+			NumServices:   1,
+		},
+		GoTypes:           file_noop_proto_goTypes,
+		DependencyIndexes: file_noop_proto_depIdxs,
+		MessageInfos:      file_noop_proto_msgTypes,
+	}.Build()
+	File_noop_proto = out.File
+	file_noop_proto_goTypes = nil
+	file_noop_proto_depIdxs = nil
+}

pkg/api/grpcpb/noop.proto

@@ -0,0 +1,17 @@
+syntax = "proto3";
+
+package io.podman.v1;
+
+option go_package = "github.com/containers/podman/v6/pkg/api/grpcpb";
+
+service Noop {
+  rpc Noop(NoopRequest) returns (NoopResponse);
+}
+
+message NoopRequest {
+  string ignored = 1;
+}
+
+message NoopResponse {
+  string ignored = 1;
+}

pkg/api/grpcpb/noop_grpc.pb.go

@@ -0,0 +1,121 @@
+// Code generated by protoc-gen-go-grpc. DO NOT EDIT.
+// versions:
+// - protoc-gen-go-grpc v1.5.1
+// - protoc             v3.19.6
+// source: noop.proto
+
+package grpcpb
+
+import (
+	context "context"
+	grpc "google.golang.org/grpc"
+	codes "google.golang.org/grpc/codes"
+	status "google.golang.org/grpc/status"
+)
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the grpc package it is being compiled against.
+// Requires gRPC-Go v1.64.0 or later.
+const _ = grpc.SupportPackageIsVersion9
+
+const (
+	Noop_Noop_FullMethodName = "/io.podman.v1.Noop/Noop"
+)
+
+// NoopClient is the client API for Noop service.
+//
+// For semantics around ctx use and closing/ending streaming RPCs, please refer to https://pkg.go.dev/google.golang.org/grpc/?tab=doc#ClientConn.NewStream.
+type NoopClient interface {
+	Noop(ctx context.Context, in *NoopRequest, opts ...grpc.CallOption) (*NoopResponse, error)
+}
+
+type noopClient struct {
+	cc grpc.ClientConnInterface
+}
+
+func NewNoopClient(cc grpc.ClientConnInterface) NoopClient {
+	return &noopClient{cc}
+}
+
+func (c *noopClient) Noop(ctx context.Context, in *NoopRequest, opts ...grpc.CallOption) (*NoopResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(NoopResponse)
+	err := c.cc.Invoke(ctx, Noop_Noop_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+// NoopServer is the server API for Noop service.
+// All implementations must embed UnimplementedNoopServer
+// for forward compatibility.
+type NoopServer interface {
+	Noop(context.Context, *NoopRequest) (*NoopResponse, error)
+	mustEmbedUnimplementedNoopServer()
+}
+
+// UnimplementedNoopServer must be embedded to have
+// forward compatible implementations.
+//
+// NOTE: this should be embedded by value instead of pointer to avoid a nil
+// pointer dereference when methods are called.
+type UnimplementedNoopServer struct{}
+
+func (UnimplementedNoopServer) Noop(context.Context, *NoopRequest) (*NoopResponse, error) {
+	return nil, status.Errorf(codes.Unimplemented, "method Noop not implemented")
+}
+func (UnimplementedNoopServer) mustEmbedUnimplementedNoopServer() {}
+func (UnimplementedNoopServer) testEmbeddedByValue()              {}
+
+// UnsafeNoopServer may be embedded to opt out of forward compatibility for this service.
+// Use of this interface is not recommended, as added methods to NoopServer will
+// result in compilation errors.
+type UnsafeNoopServer interface {
+	mustEmbedUnimplementedNoopServer()
+}
+
+func RegisterNoopServer(s grpc.ServiceRegistrar, srv NoopServer) {
+	// If the following call pancis, it indicates UnimplementedNoopServer was
+	// embedded by pointer and is nil.  This will cause panics if an
+	// unimplemented method is ever invoked, so we test this at initialization
+	// time to prevent it from happening at runtime later due to I/O.
+	if t, ok := srv.(interface{ testEmbeddedByValue() }); ok {
+		t.testEmbeddedByValue()
+	}
+	s.RegisterService(&Noop_ServiceDesc, srv)
+}
+
+func _Noop_Noop_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(NoopRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(NoopServer).Noop(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: Noop_Noop_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(NoopServer).Noop(ctx, req.(*NoopRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+// Noop_ServiceDesc is the grpc.ServiceDesc for Noop service.
+// It's only intended for direct use with grpc.RegisterService,
+// and not to be introspected or modified (even as a copy)
+var Noop_ServiceDesc = grpc.ServiceDesc{
+	ServiceName: "io.podman.v1.Noop",
+	HandlerType: (*NoopServer)(nil),
+	Methods: []grpc.MethodDesc{
+		{
+			MethodName: "Noop",
+			Handler:    _Noop_Noop_Handler,
+		},
+	},
+	Streams:  []grpc.StreamDesc{},
+	Metadata: "noop.proto",
+}

pkg/api/handlers/grpc/noop.go

@@ -0,0 +1,26 @@
+//go:build !remote
+
+package grpc
+
+import (
+	"context"
+
+	"github.com/containers/podman/v6/libpod"
+	"github.com/containers/podman/v6/pkg/api/grpcpb"
+)
+
+type noopServer struct {
+	grpcpb.UnimplementedNoopServer
+	runtime *libpod.Runtime
+}
+
+func (noopServer) Noop(_ context.Context, req *grpcpb.NoopRequest) (*grpcpb.NoopResponse, error) {
+	resp := &grpcpb.NoopResponse{
+		Ignored: req.GetIgnored(),
+	}
+	return resp, nil
+}
+
+func NewNoopServer(runtime *libpod.Runtime) grpcpb.NoopServer {
+	return &noopServer{runtime: runtime}
+}

pkg/api/server/server.go

@@ -19,7 +19,9 @@ import (
 
 	"github.com/containers/podman/v6/libpod"
 	"github.com/containers/podman/v6/libpod/shutdown"
+	"github.com/containers/podman/v6/pkg/api/grpcpb"
 	"github.com/containers/podman/v6/pkg/api/handlers"
+	grpchandlers "github.com/containers/podman/v6/pkg/api/handlers/grpc"
 	"github.com/containers/podman/v6/pkg/api/server/idle"
 	"github.com/containers/podman/v6/pkg/api/types"
 	"github.com/containers/podman/v6/pkg/domain/entities"
@@ -28,12 +30,13 @@ import (
 	"github.com/gorilla/mux"
 	"github.com/gorilla/schema"
 	"github.com/sirupsen/logrus"
-	_ "google.golang.org/grpc"
-	_ "google.golang.org/grpc/reflection"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/reflection"
 )
 
 type APIServer struct {
 	http.Server                      // The HTTP work happens here
+	grpc               *grpc.Server  // GRPC stuff happens here
 	net.Listener                     // mux for routing HTTP API calls to libpod routines
 	*libpod.Runtime                  // Where the real work happens
 	*schema.Decoder                  // Decoder for Query parameters to structs
@@ -73,6 +76,10 @@ func newServer(runtime *libpod.Runtime, listener net.Listener, opts entities.Ser
 	router := mux.NewRouter().UseEncodedPath()
 	tracker := idle.NewTracker(opts.Timeout)
 
+	serverProtocols := &http.Protocols{}
+	serverProtocols.SetHTTP1(true)
+	serverProtocols.SetHTTP2(true)
+
 	server := APIServer{
 		Server: http.Server{
 			ConnContext: func(ctx context.Context, c net.Conn) context.Context {
@@ -82,7 +89,9 @@ func newServer(runtime *libpod.Runtime, listener net.Listener, opts entities.Ser
 			ErrorLog:    log.New(logrus.StandardLogger().Out, "", 0),
 			Handler:     router,
 			IdleTimeout: opts.Timeout * 2,
+			Protocols:   serverProtocols,
 		},
+		grpc:            grpc.NewServer(),
 		CorsHeaders:     opts.CorsHeaders,
 		Listener:        listener,
 		PProfAddr:       opts.PProfAddr,
@@ -92,6 +101,9 @@ func newServer(runtime *libpod.Runtime, listener net.Listener, opts entities.Ser
 		tlsClientCAFile: opts.TLSClientCAFile,
 	}
 
+	router.NewRoute().HeadersRegexp("Content-Type", "application/grpc(\\+.*)?").Handler(server.grpc)
+	reflection.Register(server.grpc)
+
 	server.BaseContext = func(_ net.Listener) context.Context {
 		ctx := context.WithValue(context.Background(), types.DecoderKey, handlers.NewAPIDecoder())
 		ctx = context.WithValue(ctx, types.CompatDecoderKey, handlers.NewCompatAPIDecoder())
@@ -163,6 +175,8 @@ func newServer(runtime *libpod.Runtime, listener net.Listener, opts entities.Ser
 		}
 	}
 
+	grpcpb.RegisterNoopServer(server.grpc, grpchandlers.NewNoopServer(runtime)) // TODO: make this table-driven instead of a one-off?
+
 	if logrus.IsLevelEnabled(logrus.TraceLevel) {
 		// If in trace mode log request and response bodies
 		router.Use(loggingHandler())
@@ -213,6 +227,7 @@ func (s *APIServer) Serve() error {
 	s.setupPprof()
 
 	if err := shutdown.Register("service", func(_ os.Signal) error {
+		s.grpc.GracefulStop()
 		err := s.Shutdown(true)
 		if err == nil {
 			// For `systemctl stop podman.service` support, exit code should be 0
@@ -247,6 +262,7 @@ func (s *APIServer) Serve() error {
 			}
 			err = s.Server.ServeTLS(s.Listener, s.tlsCertFile, s.tlsKeyFile)
 		} else {
+			s.Server.Protocols.SetUnencryptedHTTP2(true)
 			err = s.Server.Serve(s.Listener)
 		}
 		if err != nil && err != http.ErrServerClosed {

test/system/251-system-service.bats

@@ -46,6 +46,24 @@ function _podman_system_service {
     rm -f $PODMAN_TMPDIR/myunix.sock
 }
 
+@test "podman system service: grpc listener" {
+    unset REMOTESYSTEM_TRANSPORT
+
+    skip_if_remote "podman system service unavailable over remote"
+    URL=unix://$PODMAN_TMPDIR/myunix.sock
+
+    _podman_system_service $URL --time=0
+    wait_for_file $PODMAN_TMPDIR/myunix.sock
+
+    nonce=$RANDOM
+    run_podman_testing --url "$URL" noop '{"ignored":"'$nonce'"}'
+    assert $status -eq 0
+    is $(jq -c <<< "$output") '{"ignored":"'$nonce'"}' "noop responder"
+
+    systemctl stop $SERVICE_NAME
+    rm -f $PODMAN_TMPDIR/myunix.sock
+}
+
 @test "podman-system-service containers survive service stop" {
     unset REMOTESYSTEM_TRANSPORT