Struct MachIPCSource 

pub struct MachIPCSource {
    pub config: MachIPCConfig,
}

Harvests timing jitter from Mach IPC using complex OOL messages.

What it measures

Nanosecond timing of mach_msg() sends with out-of-line memory descriptors, round-robined across a pool of Mach ports.

Why it’s entropic

Complex Mach messages with OOL descriptors traverse deep kernel paths:

• OOL VM remapping — vm_map_copyin/vm_map_copyout exercises page tables, physical page allocation, and TLB updates
• Port namespace contention — round-robin across ports exercises the splay tree with timing dependent on tree depth and rebalancing
• Per-port lock contention — ipc_mqueue_send acquires per-port locks
• Receiver thread wakeup — cross-thread scheduling decisions affected by ALL runnable threads

What makes it unique

Mach IPC is unique to XNU/macOS. Unlike higher-level IPC (pipes, sockets), Mach messages go through XNU’s ipc_mqueue subsystem with entirely different locking and scheduling paths. OOL descriptors add VM operations that no other entropy source exercises.

Configuration

See MachIPCConfig for tunable parameters. Key options:

• use_complex_messages: OOL messages vs simple port ops (recommended: true)
• num_ports: controls namespace contention level
• ool_size: controls VM remapping workload per message

Fields

config: MachIPCConfig

Source configuration. Use Default::default() for recommended settings.

Trait Implementations

impl Default for MachIPCSource

fn default() -> MachIPCSource

Returns the “default value” for a type.

impl EntropySource for MachIPCSource

fn info(&self) -> &SourceInfo

Source metadata.

fn is_available(&self) -> bool

Check if this source can operate on the current machine.

fn collect(&self, n_samples: usize) -> Vec<u8>

Collect raw entropy samples. Returns a Vec<u8> of up to n_samples bytes.

fn name(&self) -> &'static str

Convenience: name from info.