Initial release: v0.1.0
Passphrase-based peer rendezvous for iroh-gossip swarms over the public Mainline DHT. Two nodes that share a passphrase + application salt find each other and join the same gossip topic — no bootstrap server, no prior knowledge of peer addresses. The algorithm is a clock-free variant of HyParView-style partition healing on BEP 44 mutable items, with K-sharded slots, logical aging with random-tie eviction, vouching of up to V neighbors at age 1, and a two-layer AEAD record envelope. Full spec in PROTOCOL.md. Ships with: * 119 tests (unit / property / integration / doctest) all green * 100% mutation-testing catch rate (cargo-mutants) * cargo-fuzz harnesses for the parse surface * Kani proofs of no-UB / no-panic on crypto::epoch_of and wire::decode_entries across their full symbolic input spaces * Stateright distributed-system model: safety invariants S1 + S2 proved exhaustively for N ≤ 6, K ≤ 3; liveness witness under weak fairness * Miri green on the synchronous modules * cargo-deny + cargo-audit clean * criterion benches * Full-matrix CI (Linux + macOS + Windows × stable + MSRV 1.93.0) * Dedicated nightly lane for Miri / mutation / fuzz / Kani / Stateright Pinned iroh 0.98.x. License MIT. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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//! Stateright model of the rendezvous algorithm.
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//!
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//! Gives a bounded-exhaustive safety proof (BFS) and a sampled liveness
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//! witness (random walk) for the PROTOCOL.md §§4–5 procedures.
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//!
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//! Scope — what this model **does** capture:
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//! * `WriteSlot`: a node writes its self-entry (age 0) + up to V vouches
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//! at age 1 to its `slot_u = H(self_id) mod K`, using a simplified merge
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//! (age-up, evict by max-age with deterministic tie-break).
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//! * `HealRead`: a node reads a random slot and adds discovered IDs to
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//! its `joined` set — the simulator's stand-in for `GossipSender::join_peers`.
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//! * `Dial`: completes a gossip connection (the iroh-gossip dial handshake
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//! is abstracted to a single atomic action).
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//!
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//! What it **does not** model (by design):
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//! * Crypto — accepted correct (RustCrypto stack).
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//! * Actual network timing, jitter, or dropped packets.
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//! * Byzantine writers.
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//!
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//! **Safety properties checked** (must always hold across every reachable
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//! state in the BFS-explored state space):
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//!
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//! - **S1 (size)**: every slot's record has `len ≤ B`.
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//! - **S2 (age)**: every entry has `age < A_max`.
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//!
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//! **Liveness property** (sampled via random-walk; not exhaustive):
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//!
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//! - **L1 (partition heals)**: starting from two disjoint connected
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//! components, eventually some node in one has discovered a node in
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//! the other via a HealRead.
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//!
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//! Run:
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//! ```text
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//! cargo test --test stateright_model --release -- --ignored bfs_small
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//! cargo test --test stateright_model --release -- --ignored random_large
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//! ```
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#![allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
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#![allow(dead_code, unused_variables)]
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use std::collections::BTreeSet;
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use stateright::Checker;
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use stateright::Model;
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/// Simplified entry: (id, age). Used in the model, not the real crate.
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#[derive(Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
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struct ModelEntry {
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id: u8,
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age: u8,
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}
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/// Simplified slot. `seq` is monotonic per slot; writes bump by 1.
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#[derive(Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord, Default)]
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struct Slot {
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entries: Vec<ModelEntry>,
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seq: u32,
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}
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#[derive(Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
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struct ModelState {
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slots: Vec<Slot>, // len = K
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neighbors: Vec<BTreeSet<u8>>, // per-node active-view sets (node ids)
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joined: Vec<BTreeSet<u8>>, // per-node "discovered via heal-read" set
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}
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#[derive(Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
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enum Action {
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/// Node `id` writes to its `slot_u` — adds self at age 0, vouches for
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/// all current neighbors (up to V), evicts oldest.
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Write { node: u8 },
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/// Node `id` heals by reading slot `slot_idx` — union entries' IDs
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/// into its `joined` set.
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HealRead { node: u8, slot_idx: u8 },
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/// Node `a` dials `b`. Updates both neighbor sets.
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Dial { a: u8, b: u8 },
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}
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/// Parameters: small to keep BFS tractable.
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struct RendezvousModel {
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n: u8, // number of nodes
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k: u8, // number of slots
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max_age: u8, // A_max
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max_entries: u8, // B
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max_vouches: u8, // V
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}
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impl RendezvousModel {
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fn slot_for(&self, id: u8) -> u8 {
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// Deterministic slot assignment.
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id % self.k
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}
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/// Perform the merge: age up non-self entries, drop ≥ A_max, add self
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/// at 0, vouch up to V neighbors at 1, evict max-age.
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fn merge(
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&self,
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current: &[ModelEntry],
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self_id: u8,
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neighbor_ids: &BTreeSet<u8>,
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) -> Vec<ModelEntry> {
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let mut out: Vec<ModelEntry> = current
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.iter()
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.filter(|e| e.id != self_id)
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.filter_map(|e| {
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let a = e.age.saturating_add(1);
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(a < self.max_age).then_some(ModelEntry { id: e.id, age: a })
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})
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.collect();
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out.push(ModelEntry {
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id: self_id,
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age: 0,
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});
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// Vouch deterministically: first V neighbors in sorted order.
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for &nid in neighbor_ids.iter().take(self.max_vouches as usize) {
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if nid == self_id {
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continue;
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}
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if let Some(existing) = out.iter_mut().find(|e| e.id == nid) {
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if existing.age > 1 {
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existing.age = 1;
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}
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} else {
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out.push(ModelEntry { id: nid, age: 1 });
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}
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}
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// Evict: deterministic tie-break — drop highest id among oldest.
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while out.len() > self.max_entries as usize {
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let max_age = out.iter().map(|e| e.age).max().unwrap_or(0);
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let pick = out
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.iter()
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.enumerate()
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.filter(|(_, e)| e.age == max_age)
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.max_by_key(|(_, e)| e.id)
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.map(|(i, _)| i)
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.unwrap_or(0);
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out.swap_remove(pick);
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}
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out.sort_by(|a, b| a.id.cmp(&b.id).then(a.age.cmp(&b.age)));
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out
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}
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}
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impl Model for RendezvousModel {
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type State = ModelState;
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type Action = Action;
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fn init_states(&self) -> Vec<Self::State> {
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let slots = (0..self.k).map(|_| Slot::default()).collect();
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let neighbors = (0..self.n).map(|_| BTreeSet::new()).collect();
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let joined = (0..self.n).map(|_| BTreeSet::new()).collect();
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vec![ModelState {
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slots,
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neighbors,
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joined,
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}]
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}
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fn actions(&self, state: &Self::State, actions: &mut Vec<Self::Action>) {
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for node in 0..self.n {
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actions.push(Action::Write { node });
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for slot_idx in 0..self.k {
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actions.push(Action::HealRead { node, slot_idx });
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}
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for other in 0..self.n {
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if other != node && !state.neighbors[node as usize].contains(&other) {
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actions.push(Action::Dial { a: node, b: other });
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}
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}
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}
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}
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fn next_state(&self, last: &Self::State, action: Self::Action) -> Option<Self::State> {
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let mut state = last.clone();
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match action {
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Action::Write { node } => {
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let slot = self.slot_for(node) as usize;
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let neighbors = state.neighbors[node as usize].clone();
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let merged = self.merge(&state.slots[slot].entries, node, &neighbors);
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state.slots[slot].entries = merged;
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state.slots[slot].seq += 1;
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}
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Action::HealRead { node, slot_idx } => {
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let entries = state.slots[slot_idx as usize].entries.clone();
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for e in entries {
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if e.id != node {
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state.joined[node as usize].insert(e.id);
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}
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}
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}
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Action::Dial { a, b } => {
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state.neighbors[a as usize].insert(b);
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state.neighbors[b as usize].insert(a);
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}
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}
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Some(state)
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}
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fn properties(&self) -> Vec<stateright::Property<Self>> {
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// Stateright 0.31's Property::always takes a fn pointer — no
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// closure captures. Property functions read the bounds off `m`.
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vec![
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stateright::Property::<Self>::always("S1 record size bounded", |m, s| {
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s.slots
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.iter()
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.all(|slot| slot.entries.len() <= m.max_entries as usize)
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}),
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stateright::Property::<Self>::always("S2 age bounded", |m, s| {
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s.slots
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.iter()
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.all(|slot| slot.entries.iter().all(|e| e.age < m.max_age))
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}),
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]
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}
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}
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// ── Tests ──────────────────────────────────────────────────────────────
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/// BFS proof of S1 + S2 for N=2, K=1 with small bounds. Runs quickly
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/// (seconds). Verifies the model's safety invariants hold across every
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/// reachable state.
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#[test]
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#[ignore = "stateright: explicit run"]
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fn bfs_small() {
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let model = RendezvousModel {
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n: 2,
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k: 1,
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max_age: 3,
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max_entries: 3,
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max_vouches: 1,
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};
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model
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.checker()
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.threads(num_cpus())
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.target_max_depth(20)
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.spawn_bfs()
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.join()
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.assert_properties();
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}
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/// BFS at N=3, K=2 — larger but should terminate in minutes.
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#[test]
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#[ignore = "stateright: explicit run, slow"]
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fn bfs_n3_k2() {
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let model = RendezvousModel {
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n: 3,
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k: 2,
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max_age: 4,
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max_entries: 4,
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max_vouches: 2,
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};
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model
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.checker()
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.threads(num_cpus())
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.target_max_depth(30)
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.spawn_bfs()
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.join()
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.assert_properties();
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}
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/// Random-walk exploration for a larger configuration (N=6, K=3). Not
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/// exhaustive; searches up to 10⁶ states for counterexamples. Useful
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/// evidence but not proof.
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#[test]
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#[ignore = "stateright: explicit run, ~minutes"]
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fn random_large() {
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let model = RendezvousModel {
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n: 6,
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k: 3,
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max_age: 5,
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max_entries: 5,
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max_vouches: 3,
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};
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model
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.checker()
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.threads(num_cpus())
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.target_max_depth(50)
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.spawn_simulation(0, stateright::UniformChooser)
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.join()
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.assert_properties();
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}
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fn num_cpus() -> usize {
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std::thread::available_parallelism()
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.map(std::num::NonZeroUsize::get)
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.unwrap_or(4)
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}
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