Ensure pod infra containers have an exit command

Most Libpod containers are made via `pkg/specgen/generate` which
includes code to generate an appropriate exit command which will
handle unmounting the container's storage, cleaning up the
container's network, etc. There is one notable exception: pod
infra containers, which are made entirely within Libpod and do
not touch pkg/specgen. As such, no cleanup process, network never
cleaned up, bad things can happen.

There is good news, though - it's not that difficult to add this,
and it's done in this PR. Generally speaking, we don't allow
passing options directly to the infra container at create time,
but we do (optionally) proxy a pre-approved set of options into
it when we create it. Add ExitCommand to these options, and set
it at time of pod creation using the same code we use to generate
exit commands for normal containers.

Fixes #7103

Signed-off-by: Matthew Heon <mheon@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/libpod/container_config.go b/libpod/container_config.go
index 5f89395c1..3fc058d52 100644
--- a/libpod/container_config.go
+++ b/libpod/container_config.go
@@ -310,7 +310,11 @@ type ContainerMiscConfig struct {
 	// OCIRuntime used to create the container
 	OCIRuntime string `json:"runtime,omitempty"`
 	// ExitCommand is the container's exit command.
-	// This Command will be executed when the container exits
+	// This Command will be executed when the container exits by Conmon.
+	// It is usually used to invoke post-run cleanup - for example, in
+	// Podman, it invokes `podman container cleanup`, which in turn calls
+	// Libpod's Cleanup() API to unmount the container and clean up its
+	// network.
 	ExitCommand []string `json:"exitCommand,omitempty"`
 	// IsInfra is a bool indicating whether this container is an infra container used for
 	// sharing kernel namespaces in a pod