Struct ContainerMountTable 

pub struct ContainerMountTable {
    pub mounts: Vec<ContainerMount>,
    pub hidden_ancestors: Vec<(u64, u64)>,
}

The guest’s container mount table (see the module documentation).

Fields

mounts: Vec<ContainerMount>

The rows the guest sees, in the kernel’s row order.

hidden_ancestors: Vec<(u64, u64)>

For each mount of the namespace the table hides, the nearest mount above it that the table shows, as raw mount IDs: a file on a hidden mount reports that mount’s ID in fdinfo mnt_id and STATX_MNT_ID.

Implementations

impl ContainerMountTable

pub fn select( namespace: &[ContainerMount], installed: &BTreeSet<u64>, base: &[(Vec<u8>, u64)], never: &BTreeSet<u64>, ) -> Self

The table of the namespace whose rows are namespace (in the kernel’s order). A row is shown exactly when it is:

1. a mount Hermit’s mount plan installed: hermit-cli records the mount IDs each installation creates as it installs it (owned_mounts), and passes those of every installation but a backend’s own (installed);
2. a mount at one of BASE_MOUNTPOINTS, proven the same way: base holds each base mountpoint, as the kernel escapes it, with the mount ID of a descriptor held on it, and the row counts only if it is mounted at that very path (not merely the mount containing it);
3. an ancestor of a row of (1), so that every mount Hermit installed hangs from rows the table shows.

A row in never (a backend’s own mount, an ephemeral host FUSE seed) is not shown by rule 2 or 3, and a chain of parents passes through it. No other host mount is shown, whatever it is. A shown row’s parent is its nearest shown ancestor; the namespace’s root keeps its parent, which no row shows, as Linux shows it. Each hidden row is mapped to its nearest shown ancestor (Self::shown_mount_id).

This is a chosen fidelity trade, generalizing the one made for host FUSE seed mounts (crate::procfs::is_ephemeral_host_seed_mount): a hidden mount is real and traversable, and Linux omits no real mount from these files. Hermit hides it because whether it exists is decided by unrelated host activity between runs, and a row added or removed renumbers every later row. Where Hermit is given an image root (--image), every mount below that root is Hermit’s own, so nothing is hidden there. hermit-cli also leaves the uid= and gid= superblock options out of the rows of the filesystems its plan mounts afresh, which only the container’s root can own: Linux prints a tmpfs’s owner as the initial user namespace sees it, so they would name the host user who ran Hermit where the same mount by root names no one.

pub fn shown_mount_id(&self, raw_mount_id: u64) -> u64

The raw mount ID the guest is shown for a file on mount raw_mount_id: the mount itself where the table shows it or it is no row of the namespace (pipefs, sockfs and the like, which no mountinfo lists), else its nearest shown ancestor.

pub fn shown_mount_ids(&self) -> BTreeSet<u64>

The raw mount IDs of the rows the table shows.

pub fn mountinfo(&self) -> Vec<u8>

The table as the kernel would write /proc/<pid>/mountinfo with only these rows: raw IDs, devices and peer groups, which Detcore’s mountinfo sanitizer then numbers for the guest.

pub fn mounts(&self, rewrites: &[MountInfoRootRewrite]) -> Vec<u8>

The table as Linux writes /proc/<pid>/mounts (show_vfsmnt): source, mountpoint, type, options and two zeros per row, in the table’s order, with the mountpoints rewrites translate (Hermit’s internal staging prefixes) written as the guest sees them, as its mountinfo shows them.

Trait Implementations

impl Clone for ContainerMountTable

fn clone(&self) -> ContainerMountTable

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ContainerMountTable

Only the table’s size: Detcore logs its whole configuration, this table included, on one line at each run’s start, and verbose verification compares that line between two runs character by character. The rows’ raw mount IDs differ from run to run, and their bytes print as decimal lists, so in a container with long mount options (an overlay root’s layer list) the line, and that comparison, grew without bound: the validate node running hermit_modes hit its 4 GiB memory cap on it.

fn fmt(&self, formatter: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ContainerMountTable

fn default() -> ContainerMountTable

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for ContainerMountTable

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for ContainerMountTable

impl PartialEq for ContainerMountTable

fn eq(&self, other: &ContainerMountTable) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serialize for ContainerMountTable

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for ContainerMountTable