Add support for PidsLimit in quadlet

QM needs to be able to specify the maximum number of PIDs within the QM
environment to ensure FFI.
Picking a total of 10,000 Pids might be a rasonable constraint on the
QM.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

docs/source/markdown/podman-systemd.unit.5.md

@@ -157,6 +157,7 @@ Valid options for `[Container]` are listed below:
 | NoNewPrivileges=true           | --security-opt no-new-privileges                     |
 | Rootfs=/var/lib/rootfs         | --rootfs /var/lib/rootfs                             |
 | Notify=true                    | --sdnotify container                                 |
+| PidsLimit=10000                | --pids-limit 10000                                   |
 | PodmanArgs=--add-host foobar   | --add-host foobar                                    |
 | PublishPort=50-59              | --publish 50-59                                      |
 | Pull=never                     | --pull=never                                         |
@@ -410,6 +411,11 @@ starts the child in the container. However, if the container application support
 `Notify` to true passes the notification details to the container allowing it to notify
 of startup on its own.
 
+### `PidsLimit=`
+
+Tune the container's pids limit.
+This is equivalent to the Podman `--pids-limit` option.
+
 ### `PodmanArgs=`
 
 This key contains a list of arguments passed directly to the end of the `podman run` command

pkg/systemd/quadlet/quadlet.go

@@ -91,6 +91,7 @@ const (
 	KeyNoNewPrivileges       = "NoNewPrivileges"
 	KeyNotify                = "Notify"
 	KeyOptions               = "Options"
+	KeyPidsLimit             = "PidsLimit"
 	KeyPodmanArgs            = "PodmanArgs"
 	KeyPublishPort           = "PublishPort"
 	KeyPull                  = "Pull"
@@ -163,6 +164,7 @@ var (
 		KeyNetwork:               true,
 		KeyNoNewPrivileges:       true,
 		KeyNotify:                true,
+		KeyPidsLimit:             true,
 		KeyPodmanArgs:            true,
 		KeyPublishPort:           true,
 		KeyPull:                  true,
@@ -449,18 +451,23 @@ func ConvertContainer(container *parser.UnitFile, names map[string]string, isUse
 		podman.add("--security-opt", "label:nested")
 	}
 
-	securityLabelType, _ := container.Lookup(ContainerGroup, KeySecurityLabelType)
-	if len(securityLabelType) > 0 {
+	pidsLimit, ok := container.Lookup(ContainerGroup, KeyPidsLimit)
+	if ok && len(pidsLimit) > 0 {
+		podman.add("--pids-limit", pidsLimit)
+	}
+
+	securityLabelType, ok := container.Lookup(ContainerGroup, KeySecurityLabelType)
+	if ok && len(securityLabelType) > 0 {
 		podman.add("--security-opt", fmt.Sprintf("label=type:%s", securityLabelType))
 	}
 
-	securityLabelFileType, _ := container.Lookup(ContainerGroup, KeySecurityLabelFileType)
-	if len(securityLabelFileType) > 0 {
+	securityLabelFileType, ok := container.Lookup(ContainerGroup, KeySecurityLabelFileType)
+	if ok && len(securityLabelFileType) > 0 {
 		podman.add("--security-opt", fmt.Sprintf("label=filetype:%s", securityLabelFileType))
 	}
 
-	securityLabelLevel, _ := container.Lookup(ContainerGroup, KeySecurityLabelLevel)
-	if len(securityLabelLevel) > 0 {
+	securityLabelLevel, ok := container.Lookup(ContainerGroup, KeySecurityLabelLevel)
+	if ok && len(securityLabelLevel) > 0 {
 		podman.add("--security-opt", fmt.Sprintf("label=level:%s", securityLabelLevel))
 	}
 

test/e2e/quadlet/pids-limit.container

@@ -0,0 +1,6 @@
+## assert-podman-final-args localhost/imagename
+## assert-podman-args "--pids-limit" "8765432"
+
+[Container]
+Image=localhost/imagename
+PidsLimit=8765432