relations

Documentation

Overview

Package relations gives access to properties of and relationships between Linux-kernel namespaces, such as type and ID of a namespace, its owning user namespace, parent namespace in case of hierarchical namespaces, et cetera.

While the Relation interface strongly relates to the ops package, it is separate in order to avoid import cycles, because:

• the github.com/thediveo/lxkns/ops/Opener interface needs to reference the Relation interface
• and we want to keep the Opener interface internal (due to the knowledge required to correctly handle the object and file descriptor lifecycles correctly).

Index

• type Relation

Types

type Relation

type Relation interface {
	// Type of the referenced namespace, such as CLONE_NEWNET, et cetera.
	// Returns an error in case of an invalid namespace reference (closed file
	// descriptor, invalid path, et cetera).
	//
	// ℹ️ A Linux kernel version 4.11 or later is required.
	Type() (species.NamespaceType, error)

	// ID (inode number) of the referenced namespace. Returns an error in case
	// of an invalid namespace reference.
	ID() (species.NamespaceID, error)

	// User namespace owning the referenced namespace. The owning user namespace
	// is returned in form of a NamespaceFile reference when there was no error
	// in retrieving the information.
	//
	// ℹ️ A Linux kernel version 4.9 or later is required.
	User() (Relation, error)

	// Parent namespace of the referenced PID or user namespace. Returns an
	// error if the parent doesn't exist, if the caller hasn't capabilities in
	// the parent namespace, or if the referenced namespace is neither a PID nor
	// a user namespace.
	//
	// ℹ️ A Linux kernel version 4.9 or later is required.
	Parent() (Relation, error)

	// User ID of the process originally creating the referenced user namespace.
	// Returns an error, if the referenced namespace is not a user namespace.
	//
	// ℹ️ A Linux kernel version 4.11 or later is required.
	OwnerUID() (int, error)
}

Relation defines query operations on Linux-kernel namespaces for discovering relationships between namespaces as well as some properties, when only a namespace reference is given. Such references can be in form of a filesystem path, an open file descriptor, or an open file.