cmd/podman/system: add API server support on FreeBSD

This adds the 'system service' command to the build on FreeBSD and
suppresses the call to servicereaper.Start which is only needed to
support slirp4netns on Linux. A stub for compat.StatsContainer is also
added - stats are still supported via the libpod.StatsContainer API
call.

[NO NEW TESTS NEEDED]

Signed-off-by: Doug Rabson <dfr@rabson.org>

cmd/podman/system/service.go

@@ -1,5 +1,6 @@
-//go:build linux && !remote
-// +build linux,!remote
+//go:build (linux || freebsd) && !remote
+// +build linux freebsd
+// +build !remote
 
 package system
 

cmd/podman/system/service_abi.go

@@ -1,5 +1,6 @@
-//go:build linux && !remote
-// +build linux,!remote
+//go:build (linux || freebsd) && !remote
+// +build linux freebsd
+// +build !remote
 
 package system
 
@@ -12,7 +13,6 @@ import (
 	"path/filepath"
 
 	"github.com/containers/common/pkg/cgroups"
-	"github.com/containers/common/pkg/servicereaper"
 	"github.com/containers/podman/v4/cmd/podman/registry"
 	api "github.com/containers/podman/v4/pkg/api/server"
 	"github.com/containers/podman/v4/pkg/domain/entities"
@@ -119,7 +119,7 @@ func restService(flags *pflag.FlagSet, cfg *entities.PodmanConfig, opts entities
 		logrus.Debugf("Could not move to subcgroup: %v", err)
 	}
 
-	servicereaper.Start()
+	maybeStartServiceReaper()
 	infra.StartWatcher(libpodRuntime)
 	server, err := api.NewServerWithSettings(libpodRuntime, listener, opts)
 	if err != nil {

cmd/podman/system/service_abi_common.go

@@ -0,0 +1,7 @@
+//go:build !linux && !remote
+
+package system
+
+// Currently, we only need servicereaper on Linux to support slirp4netns.
+func maybeStartServiceReaper() {
+}

cmd/podman/system/service_abi_linux.go

@@ -0,0 +1,12 @@
+//go:build linux && !remote
+
+package system
+
+import (
+	"github.com/containers/common/pkg/servicereaper"
+)
+
+// Currently, we only need servicereaper on Linux to support slirp4netns.
+func maybeStartServiceReaper() {
+	servicereaper.Start()
+}

pkg/api/handlers/compat/containers_stats_freebsd.go

@@ -0,0 +1,15 @@
+package compat
+
+import (
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/containers/podman/v4/pkg/api/handlers/utils"
+)
+
+const DefaultStatsPeriod = 5 * time.Second
+
+func StatsContainer(w http.ResponseWriter, r *http.Request) {
+	utils.Error(w, http.StatusBadRequest, fmt.Errorf("compat.StatsContainer not supported on FreeBSD"))
+}