Add a function for overwriting container config

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

4 files changed, 127 insertions, 12 deletions

diff --git a/libpod/boltdb_state.go b/libpod/boltdb_state.go
index 5bc15dd7f..104ec78e9 100644
--- a/libpod/boltdb_state.go
+++ b/libpod/boltdb_state.go
@@ -783,6 +783,50 @@ func (s *BoltState) AllContainers() ([]*Container, error) {
 	return ctrs, nil
 }
 
+// RewriteContainerConfig rewrites a container's configuration.
+// WARNING: This function is DANGEROUS. Do not use without reading the full
+// comment on this function in state.go.
+func (s *BoltState) RewriteContainerConfig(ctr *Container, newCfg *ContainerConfig) error {
+	if !s.valid {
+		return ErrDBClosed
+	}
+
+	if !ctr.valid {
+		return ErrCtrRemoved
+	}
+
+	newCfgJSON, err := json.Marshal(newCfg)
+	if err != nil {
+		return errors.Wrapf(err, "error marshalling new configuration JSON for container %s", ctr.ID())
+	}
+
+	db, err := s.getDBCon()
+	if err != nil {
+		return err
+	}
+	defer s.closeDBCon(db)
+
+	err = db.Update(func(tx *bolt.Tx) error {
+		ctrBkt, err := getCtrBucket(tx)
+		if err != nil {
+			return err
+		}
+
+		ctrDB := ctrBkt.Bucket([]byte(ctr.ID()))
+		if ctrDB == nil {
+			ctr.valid = false
+			return errors.Wrapf(ErrNoSuchCtr, "no container with ID %s found in DB", ctr.ID())
+		}
+
+		if err := ctrDB.Put(configKey, newCfgJSON); err != nil {
+			return errors.Wrapf(err, "error updating container %s config JSON", ctr.ID())
+		}
+
+		return nil
+	})
+	return err
+}
+
 // Pod retrieves a pod given its full ID
 func (s *BoltState) Pod(id string) (*Pod, error) {
 	if id == "" {
diff --git a/libpod/in_memory_state.go b/libpod/in_memory_state.go
index 314799309..2f8fafa39 100644
--- a/libpod/in_memory_state.go
+++ b/libpod/in_memory_state.go
@@ -378,6 +378,38 @@ func (s *InMemoryState) ContainerInUse(ctr *Container) ([]string, error) {
 	return arr, nil
 }
 
+// AllContainers retrieves all containers from the state
+func (s *InMemoryState) AllContainers() ([]*Container, error) {
+	ctrs := make([]*Container, 0, len(s.containers))
+	for _, ctr := range s.containers {
+		if s.namespace == "" || ctr.config.Namespace == s.namespace {
+			ctrs = append(ctrs, ctr)
+		}
+	}
+
+	return ctrs, nil
+}
+
+// RewriteContainerConfig rewrites a container's configuration.
+// This function is DANGEROUS, even with an in-memory state.
+// Please read the full comment on it in state.go before using it.
+func (s *InMemoryState) RewriteContainerConfig(ctr *Container, newCfg *ContainerConfig) error {
+	if !ctr.valid {
+		return ErrCtrRemoved
+	}
+
+	// If the container does not exist, return error
+	stateCtr, ok := s.containers[ctr.ID()]
+	if !ok {
+		ctr.valid = false
+		return errors.Wrapf(ErrNoSuchCtr, "container with ID %s not found in state", ctr.ID())
+	}
+
+	stateCtr.config = newCfg
+
+	return nil
+}
+
 // Volume retrieves a volume from its full name
 func (s *InMemoryState) Volume(name string) (*Volume, error) {
 	if name == "" {
@@ -486,18 +518,6 @@ func (s *InMemoryState) AllVolumes() ([]*Volume, error) {
 	return allVols, nil
 }
 
-// AllContainers retrieves all containers from the state
-func (s *InMemoryState) AllContainers() ([]*Container, error) {
-	ctrs := make([]*Container, 0, len(s.containers))
-	for _, ctr := range s.containers {
-		if s.namespace == "" || ctr.config.Namespace == s.namespace {
-			ctrs = append(ctrs, ctr)
-		}
-	}
-
-	return ctrs, nil
-}
-
 // Pod retrieves a pod from the state from its full ID
 func (s *InMemoryState) Pod(id string) (*Pod, error) {
 	if id == "" {
diff --git a/libpod/state.go b/libpod/state.go
index 88d89f673..42dbe9cc1 100644
--- a/libpod/state.go
+++ b/libpod/state.go
@@ -97,6 +97,21 @@ type State interface {
 	// returned.
 	AllContainers() ([]*Container, error)
 
+	// PLEASE READ FULL DESCRIPTION BEFORE USING.
+	// Rewrite a container's configuration.
+	// This function breaks libpod's normal prohibition on a read-only
+	// configuration, and as such should be used EXTREMELY SPARINGLY and
+	// only in very specific circumstances.
+	// Specifically, it is ONLY safe to use thing function to make changes
+	// that result in a functionally identical configuration (migrating to
+	// newer, but identical, configuration fields), or during libpod init
+	// WHILE HOLDING THE ALIVE LOCK (to prevent other libpod instances from
+	// being initialized).
+	// There are a lot of capital letters and conditions here, but the short
+	// answer is this: use this only very sparingly, and only if you really
+	// know what you're doing.
+	RewriteContainerConfig(ctr *Container, newCfg *ContainerConfig) error
+
 	// Accepts full ID of pod.
 	// If the pod given is not in the set namespace, an error will be
 	// returned.
diff --git a/libpod/state_test.go b/libpod/state_test.go
index 4bd00ab55..dd03903ac 100644
--- a/libpod/state_test.go
+++ b/libpod/state_test.go
@@ -1298,6 +1298,42 @@ func TestCannotUseBadIDAsGenericDependency(t *testing.T) {
 	})
 }
 
+func TestRewriteContainerConfigDoesNotExist(t *testing.T) {
+	runForAllStates(t, func(t *testing.T, state State, manager lock.Manager) {
+		err := state.RewriteContainerConfig(&Container{}, &ContainerConfig{})
+		assert.Error(t, err)
+	})
+}
+
+func TestRewriteContainerConfigNotInState(t *testing.T) {
+	runForAllStates(t, func(t *testing.T, state State, manager lock.Manager) {
+		testCtr, err := getTestCtr1(manager)
+		assert.NoError(t, err)
+		err = state.RewriteContainerConfig(testCtr, &ContainerConfig{})
+		assert.Error(t, err)
+	})
+}
+
+func TestRewriteContainerConfigRewritesConfig(t *testing.T) {
+	runForAllStates(t, func(t *testing.T, state State, manager lock.Manager) {
+		testCtr, err := getTestCtr1(manager)
+		assert.NoError(t, err)
+
+		err = state.AddContainer(testCtr)
+		assert.NoError(t, err)
+
+		testCtr.config.LogPath = "/another/path/"
+
+		err = state.RewriteContainerConfig(testCtr, testCtr.config)
+		assert.NoError(t, err)
+
+		testCtrFromState, err := state.Container(testCtr.ID())
+		assert.NoError(t, err)
+
+		testContainersEqual(t, testCtrFromState, testCtr, true)
+	})
+}
+
 func TestGetPodDoesNotExist(t *testing.T) {
 	runForAllStates(t, func(t *testing.T, state State, manager lock.Manager) {
 		_, err := state.Pod("doesnotexist")