Implement --sdnotify cmdline option to control sd-notify behavior

--sdnotify container|conmon|ignore
With "conmon", we send the MAINPID, and clear the NOTIFY_SOCKET so the OCI
runtime doesn't pass it into the container. We also advertise "ready" when the
OCI runtime finishes to advertise the service as ready.

With "container", we send the MAINPID, and leave the NOTIFY_SOCKET so the OCI
runtime passes it into the container for initialization, and let the container advertise further metadata.
This is the default, which is closest to the behavior podman has done in the past.

The "ignore" option removes NOTIFY_SOCKET from the environment, so neither podman nor
any child processes will talk to systemd.

This removes the need for hardcoded CID and PID files in the command line, and
the PIDFile directive, as the pid is advertised directly through sd-notify.

Signed-off-by: Joseph Gooch <mrwizard@dok.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/pkg/specgen/container_validate.go b/pkg/specgen/container_validate.go
index 8063bee38..bf03ff0e7 100644
--- a/pkg/specgen/container_validate.go
+++ b/pkg/specgen/container_validate.go
@@ -3,6 +3,7 @@ package specgen
 import (
 	"strings"
 
+	"github.com/containers/libpod/v2/libpod/define"
 	"github.com/containers/libpod/v2/pkg/rootless"
 	"github.com/containers/libpod/v2/pkg/util"
 	"github.com/pkg/errors"
@@ -13,6 +14,8 @@ var (
 	ErrInvalidSpecConfig = errors.New("invalid configuration")
 	// SystemDValues describes the only values that SystemD can be
 	SystemDValues = []string{"true", "false", "always"}
+	// SdNotifyModeValues describes the only values that SdNotifyMode can be
+	SdNotifyModeValues = []string{define.SdNotifyModeContainer, define.SdNotifyModeConmon, define.SdNotifyModeIgnore}
 	// ImageVolumeModeValues describes the only values that ImageVolumeMode can be
 	ImageVolumeModeValues = []string{"ignore", "tmpfs", "anonymous"}
 )
@@ -40,6 +43,10 @@ func (s *SpecGenerator) Validate() error {
 	if len(s.ContainerBasicConfig.Systemd) > 0 && !util.StringInSlice(strings.ToLower(s.ContainerBasicConfig.Systemd), SystemDValues) {
 		return errors.Wrapf(ErrInvalidSpecConfig, "--systemd values must be one of %q", strings.Join(SystemDValues, ", "))
 	}
+	// sdnotify values must be container, conmon, or ignore
+	if len(s.ContainerBasicConfig.SdNotifyMode) > 0 && !util.StringInSlice(strings.ToLower(s.ContainerBasicConfig.SdNotifyMode), SdNotifyModeValues) {
+		return errors.Wrapf(ErrInvalidSpecConfig, "--sdnotify values must be one of %q", strings.Join(SdNotifyModeValues, ", "))
+	}
 
 	//
 	// ContainerStorageConfig