Struct ReplayCache 

pub struct ReplayCache { /* private fields */ }

Bounded FIFO cache of (link_id, signature, nonce) SHA-256 fingerprints. Cheap to clone (it’s behind an Arc in the daemon’s AppState); the inner mutex serialises every insert/lookup so the cache is safe to share across handler invocations.

Implementations

impl ReplayCache

pub fn new() -> Self

Fresh empty cache at the documented capacity.

pub fn record_and_check( &self, link_id: &str, signature: &[u8], nonce: &str, ) -> ReplayDecision

Fingerprint (link_id, signature, nonce) and check membership. Returns true if the fingerprint has been seen before — the caller should reject the request as a replay. Returns false on the first seen value AND inserts it as a side effect.

The caller is responsible for producing the nonce (random UUID expected) and for choosing whether to bypass this check when the request omits the nonce field (back-compat mode).

pub fn len(&self) -> usize

Number of currently-cached fingerprints. Useful for tests and for a future metrics exporter.

pub fn is_empty(&self) -> bool

Whether the cache is empty. Trivial helper to satisfy clippy (len_zero) on the few call sites that care.

pub fn evictions_since_boot(&self) -> u64

v0.7.0 #1033 — cumulative number of FIFO evictions since process boot. Non-zero values mean the cache hit its ceiling and dropped older fingerprints to make room. Operators should surface this via a metrics exporter and page on sustained growth: either legitimate verify-flow load is exceeding the documented ceiling (escalate to a true distributed cache) OR an attacker is flooding unique nonces to evict legitimate fingerprints (the issue’s flush-attack vector — investigate rate-limit at /api/v1/links/verify).

Trait Implementations

impl Debug for ReplayCache

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

Formats the value using the given formatter.

impl Default for ReplayCache

fn default() -> ReplayCache

Returns the “default value” for a type.