Add network aliases for containers to DB

This adds the database backend for network aliases. Aliases are
additional names for a container that are used with the CNI
dnsname plugin - the container will be accessible by these names
in addition to its name. Aliases are allowed to change over time
as the container connects to and disconnects from networks.

Aliases are implemented as another bucket in the database to
register all aliases, plus two buckets for each container (one to
hold connected CNI networks, a second to hold its aliases). The
aliases are only unique per-network, to the global and
per-container aliases buckets have a sub-bucket for each CNI
network that has aliases, and the aliases are stored within that
sub-bucket. Aliases are formatted as alias (key) to container ID
(value) in both cases.

Three DB functions are defined for aliases: retrieving current
aliases for a given network, setting aliases for a given network,
and removing all aliases for a given network.

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

1 files changed, 266 insertions, 4 deletions

diff --git a/libpod/boltdb_state.go b/libpod/boltdb_state.go
index 9dd5ca465..e0db92082 100644
--- a/libpod/boltdb_state.go
+++ b/libpod/boltdb_state.go
@@ -50,10 +50,12 @@ type BoltState struct {
 //   containers in the pod.
 // - allPodsBkt: Map of ID to name containing only pods. Used for pod lookup
 //   operations.
-// - execBkt: Map of exec session ID to exec session - contains a sub-bucket for
-//   each exec session in the DB.
-// - execRegistryBkt: Map of exec session ID to nothing. Contains one entry for
-//   each exec session. Used for iterating through all exec sessions.
+// - execBkt: Map of exec session ID to container ID - used for resolving
+//   exec session IDs to the containers that hold the exec session.
+// - aliasesBkt - Contains a bucket for each CNI network, which contain a map of
+//   network alias (an extra name for containers in DNS) to the ID of the
+//   container holding the alias. Aliases must be unique per-network, and cannot
+//   conflict with names registered in nameRegistryBkt.
 // - runtimeConfigBkt: Contains configuration of the libpod instance that
 //   initially created the database. This must match for any further instances
 //   that access the database, to ensure that state mismatches with
@@ -92,6 +94,7 @@ func NewBoltState(path string, runtime *Runtime) (State, error) {
 		volBkt,
 		allVolsBkt,
 		execBkt,
+		aliasesBkt,
 		runtimeConfigBkt,
 	}
 
@@ -969,6 +972,265 @@ func (s *BoltState) AllContainers() ([]*Container, error) {
 	return ctrs, nil
 }
 
+// GetNetworkAliases retrieves the network aliases for the given container in
+// the given CNI network.
+func (s *BoltState) GetNetworkAliases(ctr *Container, network string) ([]string, error) {
+	if !s.valid {
+		return nil, define.ErrDBClosed
+	}
+
+	if !ctr.valid {
+		return nil, define.ErrCtrRemoved
+	}
+
+	if network == "" {
+		return nil, errors.Wrapf(define.ErrInvalidArg, "network names must not be empty")
+	}
+
+	if s.namespace != "" && s.namespace != ctr.config.Namespace {
+		return nil, errors.Wrapf(define.ErrNSMismatch, "container %s is in namespace %q, does not match our namespace %q", ctr.ID(), ctr.config.Namespace, s.namespace)
+	}
+
+	ctrID := []byte(ctr.ID())
+
+	db, err := s.getDBCon()
+	if err != nil {
+		return nil, err
+	}
+	defer s.deferredCloseDBCon(db)
+
+	aliases := []string{}
+
+	err = db.View(func(tx *bolt.Tx) error {
+		ctrBucket, err := getCtrBucket(tx)
+		if err != nil {
+			return err
+		}
+
+		dbCtr := ctrBucket.Bucket(ctrID)
+		if dbCtr == nil {
+			ctr.valid = false
+			return errors.Wrapf(define.ErrNoSuchCtr, "container %s does not exist in database", ctr.ID())
+		}
+
+		ctrAliasesBkt := dbCtr.Bucket(aliasesBkt)
+		if ctrAliasesBkt == nil {
+			return errors.Wrapf(define.ErrNoAliases, "container %s has no network aliases", ctr.ID())
+		}
+
+		netAliasesBkt := ctrAliasesBkt.Bucket([]byte(network))
+		if netAliasesBkt == nil {
+			return errors.Wrapf(define.ErrNoAliasesForNetwork, "container %s has no aliases for network %q", ctr.ID(), network)
+		}
+
+		return netAliasesBkt.ForEach(func(alias, v []byte) error {
+			aliases = append(aliases, string(alias))
+			return nil
+		})
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return aliases, nil
+}
+
+// SetNetworkAliases sets network aliases for the given container in the given
+// network. All existing aliases for that network (if any exist) will be removed,
+// to be replaced by the new aliases given.
+func (s *BoltState) SetNetworkAliases(ctr *Container, network string, aliases []string) error {
+	if !s.valid {
+		return define.ErrDBClosed
+	}
+
+	if !ctr.valid {
+		return define.ErrCtrRemoved
+	}
+
+	if network == "" {
+		return errors.Wrapf(define.ErrInvalidArg, "network names must not be empty")
+	}
+
+	if s.namespace != "" && s.namespace != ctr.config.Namespace {
+		return errors.Wrapf(define.ErrNSMismatch, "container %s is in namespace %q, does not match our namespace %q", ctr.ID(), ctr.config.Namespace, s.namespace)
+	}
+
+	ctrID := []byte(ctr.ID())
+
+	db, err := s.getDBCon()
+	if err != nil {
+		return err
+	}
+	defer s.deferredCloseDBCon(db)
+
+	return db.Update(func(tx *bolt.Tx) error {
+		ctrBucket, err := getCtrBucket(tx)
+		if err != nil {
+			return err
+		}
+
+		allAliasesBucket, err := getAliasesBucket(tx)
+		if err != nil {
+			return err
+		}
+
+		netAllAliasesBucket, err := allAliasesBucket.CreateBucketIfNotExists([]byte(network))
+		if err != nil {
+			return errors.Wrapf(err, "error creating network aliases bucket for network %s", network)
+		}
+
+		dbCtr := ctrBucket.Bucket(ctrID)
+		if dbCtr == nil {
+			ctr.valid = false
+			return errors.Wrapf(define.ErrNoSuchCtr, "container %s does not exist in database", ctr.ID())
+		}
+
+		ctrAliasesBkt := dbCtr.Bucket(aliasesBkt)
+		if ctrAliasesBkt == nil {
+			return errors.Wrapf(define.ErrNoAliases, "container %s has no network aliases", ctr.ID())
+		}
+
+		ctrNetworksBkt := dbCtr.Bucket(networksBkt)
+		if ctrNetworksBkt == nil {
+			return errors.Wrapf(define.ErrInvalidArg, "container %s is not connected to any CNI networks, so cannot add aliases", ctr.ID())
+		}
+		netConnected := ctrNetworksBkt.Get([]byte(network))
+		if netConnected == nil {
+			return errors.Wrapf(define.ErrInvalidArg, "container %s is not connected to CNI network %q, so cannot add aliases for this network", ctr.ID(), network)
+		}
+
+		namesBucket, err := getNamesBucket(tx)
+		if err != nil {
+			return err
+		}
+
+		// Check if the container already has network aliases for this network.
+		netAliasesBkt := ctrAliasesBkt.Bucket([]byte(network))
+		if netAliasesBkt != nil {
+			// We have aliases. Have to remove them.
+			forEachErr := netAliasesBkt.ForEach(func(alias, v []byte) error {
+				// Relies on errors.Wrapf(nil, ...) returning
+				// nil.
+				return errors.Wrapf(netAllAliasesBucket.Delete(alias), "error removing alias %q from network %q when changing aliases for container %s", string(alias), network, ctr.ID())
+			})
+			if forEachErr != nil {
+				return forEachErr
+			}
+		}
+
+		if netAliasesBkt == nil {
+			newBkt, err := ctrAliasesBkt.CreateBucket([]byte(network))
+			if err != nil {
+				return errors.Wrapf(err, "could not create bucket for network aliases for network %q", network)
+			}
+			netAliasesBkt = newBkt
+		}
+
+		for _, alias := range aliases {
+			// Check if safe to use
+			aliasExists := netAllAliasesBucket.Get([]byte(alias))
+			if aliasExists != nil {
+				return errors.Wrapf(define.ErrAliasExists, "network alias %q already exists in network %q (used by container %s)", alias, network, string(aliasExists))
+			}
+			nameExists := namesBucket.Get([]byte(alias))
+			if nameExists != nil {
+				return errors.Wrapf(define.ErrCtrExists, "a container or pod already uses the name %q, cannot add network alias for container %s", alias, ctr.ID())
+			}
+
+			// Add alias
+			if err := netAliasesBkt.Put([]byte(alias), ctrID); err != nil {
+				return errors.Wrapf(err, "error adding container %s network %q alias %q to DB", ctr.ID(), network, alias)
+			}
+			if err := netAllAliasesBucket.Put([]byte(alias), ctrID); err != nil {
+				return errors.Wrapf(err, "error adding container %s network %q alias %q to all aliases in DB", ctr.ID(), network, alias)
+			}
+		}
+
+		return nil
+	})
+}
+
+// RemoveNetworkAliases removes network aliases of the given container in the
+// given network.
+func (s *BoltState) RemoveNetworkAliases(ctr *Container, network string) error {
+	if !s.valid {
+		return define.ErrDBClosed
+	}
+
+	if !ctr.valid {
+		return define.ErrCtrRemoved
+	}
+
+	if network == "" {
+		return errors.Wrapf(define.ErrInvalidArg, "network names must not be empty")
+	}
+
+	if s.namespace != "" && s.namespace != ctr.config.Namespace {
+		return errors.Wrapf(define.ErrNSMismatch, "container %s is in namespace %q, does not match our namespace %q", ctr.ID(), ctr.config.Namespace, s.namespace)
+	}
+
+	ctrID := []byte(ctr.ID())
+
+	db, err := s.getDBCon()
+	if err != nil {
+		return err
+	}
+	defer s.deferredCloseDBCon(db)
+
+	return db.Update(func(tx *bolt.Tx) error {
+		ctrBucket, err := getCtrBucket(tx)
+		if err != nil {
+			return err
+		}
+
+		allAliasesBucket, err := getAliasesBucket(tx)
+		if err != nil {
+			return err
+		}
+
+		netAllAliasesBucket, err := allAliasesBucket.CreateBucketIfNotExists([]byte(network))
+		if err != nil {
+			return errors.Wrapf(err, "error creating network aliases bucket for network %s", network)
+		}
+
+		dbCtr := ctrBucket.Bucket(ctrID)
+		if dbCtr == nil {
+			ctr.valid = false
+			return errors.Wrapf(define.ErrNoSuchCtr, "container %s does not exist in database", ctr.ID())
+		}
+
+		ctrAliasesBkt := dbCtr.Bucket(aliasesBkt)
+		if ctrAliasesBkt == nil {
+			return errors.Wrapf(define.ErrNoAliases, "container %s has no network aliases", ctr.ID())
+		}
+
+		ctrNetworksBkt := dbCtr.Bucket(networksBkt)
+		if ctrNetworksBkt == nil {
+			return errors.Wrapf(define.ErrInvalidArg, "container %s is not connected to any CNI networks, so cannot add aliases", ctr.ID())
+		}
+		netConnected := ctrNetworksBkt.Get([]byte(network))
+		if netConnected == nil {
+			return errors.Wrapf(define.ErrInvalidArg, "container %s is not connected to CNI network %q, so cannot add aliases for this network", ctr.ID(), network)
+		}
+
+		// Check if the container already has network aliases for this network.
+		netAliasesBkt := ctrAliasesBkt.Bucket([]byte(network))
+		if netAliasesBkt != nil {
+			// We have aliases. Remove them.
+			forEachErr := netAliasesBkt.ForEach(func(alias, v []byte) error {
+				// Relies on errors.Wrapf(nil, ...) returning
+				// nil.
+				return errors.Wrapf(netAllAliasesBucket.Delete(alias), "error removing alias %q from network %q when changing aliases for container %s", string(alias), network, ctr.ID())
+			})
+			if forEachErr != nil {
+				return forEachErr
+			}
+		}
+
+		return nil
+	})
+}
+
 // GetContainerConfig returns a container config from the database by full ID
 func (s *BoltState) GetContainerConfig(id string) (*ContainerConfig, error) {
 	if len(id) == 0 {