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| 1 | +//! In-process transport for deterministic simulation. Packets wait in per-pair queues until `step` delivers |
| 2 | +//! one, so the seed drives interleavings while each pair stays ordered like a reliable channel. |
| 3 | +
|
| 4 | +use crate::packet::{PacketError, SyncPacket}; |
| 5 | +use crate::transport::{Transport, TransportEvent, TransportPeerId}; |
| 6 | +use std::collections::{BTreeMap, HashMap, VecDeque}; |
| 7 | +use std::sync::{Arc, Mutex}; |
| 8 | + |
| 9 | +#[derive(Default)] |
| 10 | +struct Shared { |
| 11 | + connected: Vec<TransportPeerId>, |
| 12 | + inboxes: HashMap<TransportPeerId, VecDeque<TransportEvent>>, |
| 13 | + in_flight: BTreeMap<(TransportPeerId, TransportPeerId), VecDeque<SyncPacket>>, |
| 14 | + next_peer: u128, |
| 15 | +} |
| 16 | + |
| 17 | +impl Shared { |
| 18 | + fn disconnect(&mut self, id: TransportPeerId) { |
| 19 | + if !self.connected.contains(&id) { |
| 20 | + return; |
| 21 | + } |
| 22 | + self.connected.retain(|&other| other != id); |
| 23 | + self.in_flight.retain(|&(from, to), _| from != id && to != id); |
| 24 | + for &other in &self.connected.clone() { |
| 25 | + self.inboxes.entry(other).or_default().push_back(TransportEvent::PeerDisconnected(id)); |
| 26 | + self.inboxes.entry(id).or_default().push_back(TransportEvent::PeerDisconnected(other)); |
| 27 | + } |
| 28 | + } |
| 29 | +} |
| 30 | + |
| 31 | +pub struct MockNetwork { |
| 32 | + shared: Arc<Mutex<Shared>>, |
| 33 | + rng: SplitMix64, |
| 34 | +} |
| 35 | + |
| 36 | +impl MockNetwork { |
| 37 | + pub fn new(seed: u64) -> Self { |
| 38 | + Self { |
| 39 | + shared: Arc::new(Mutex::new(Shared::default())), |
| 40 | + rng: SplitMix64(seed), |
| 41 | + } |
| 42 | + } |
| 43 | + |
| 44 | + /// A new, not yet connected peer. |
| 45 | + pub fn endpoint(&mut self) -> MockEndpoint { |
| 46 | + let mut shared = self.shared.lock().unwrap(); |
| 47 | + shared.next_peer += 1; |
| 48 | + let id = TransportPeerId(uuid::Uuid::from_u128(shared.next_peer)); |
| 49 | + shared.inboxes.insert(id, VecDeque::new()); |
| 50 | + MockEndpoint { |
| 51 | + id, |
| 52 | + shared: self.shared.clone(), |
| 53 | + known_peers: Vec::new(), |
| 54 | + } |
| 55 | + } |
| 56 | + |
| 57 | + pub fn connect(&mut self, id: TransportPeerId) { |
| 58 | + let mut shared = self.shared.lock().unwrap(); |
| 59 | + if shared.connected.contains(&id) { |
| 60 | + return; |
| 61 | + } |
| 62 | + for &other in &shared.connected.clone() { |
| 63 | + shared.inboxes.entry(other).or_default().push_back(TransportEvent::PeerConnected(id)); |
| 64 | + shared.inboxes.entry(id).or_default().push_back(TransportEvent::PeerConnected(other)); |
| 65 | + } |
| 66 | + shared.connected.push(id); |
| 67 | + } |
| 68 | + |
| 69 | + pub fn disconnect(&mut self, id: TransportPeerId) { |
| 70 | + self.shared.lock().unwrap().disconnect(id); |
| 71 | + } |
| 72 | + |
| 73 | + pub fn pending(&self) -> usize { |
| 74 | + self.shared.lock().unwrap().in_flight.values().map(VecDeque::len).sum() |
| 75 | + } |
| 76 | + |
| 77 | + /// Deliver one in-flight packet from a randomly chosen sender/receiver pair. |
| 78 | + pub fn step(&mut self) -> bool { |
| 79 | + let mut shared = self.shared.lock().unwrap(); |
| 80 | + let queues: Vec<_> = shared.in_flight.iter().filter(|(_, queue)| !queue.is_empty()).map(|(&key, _)| key).collect(); |
| 81 | + if queues.is_empty() { |
| 82 | + return false; |
| 83 | + } |
| 84 | + |
| 85 | + let (from, to) = queues[self.rng.below(queues.len())]; |
| 86 | + let packet = shared.in_flight.get_mut(&(from, to)).and_then(VecDeque::pop_front).expect("queue is non-empty"); |
| 87 | + shared.inboxes.entry(to).or_default().push_back(TransportEvent::Packet(from, packet)); |
| 88 | + true |
| 89 | + } |
| 90 | + |
| 91 | + pub fn deliver_all(&mut self) { |
| 92 | + while self.step() {} |
| 93 | + } |
| 94 | + |
| 95 | + pub fn deliver_to(&mut self, to: TransportPeerId) { |
| 96 | + let mut shared = self.shared.lock().unwrap(); |
| 97 | + let queues: Vec<_> = shared.in_flight.keys().copied().filter(|&(_, receiver)| receiver == to).collect(); |
| 98 | + |
| 99 | + for key in queues { |
| 100 | + let packets = shared.in_flight.get_mut(&key).map(std::mem::take).unwrap_or_default(); |
| 101 | + for packet in packets { |
| 102 | + shared.inboxes.entry(to).or_default().push_back(TransportEvent::Packet(key.0, packet)); |
| 103 | + } |
| 104 | + } |
| 105 | + } |
| 106 | + |
| 107 | + pub fn random_below(&mut self, bound: usize) -> usize { |
| 108 | + self.rng.below(bound) |
| 109 | + } |
| 110 | +} |
| 111 | + |
| 112 | +/// Like a real socket, an endpoint sends only to the peers whose connect events it has polled. |
| 113 | +pub struct MockEndpoint { |
| 114 | + id: TransportPeerId, |
| 115 | + shared: Arc<Mutex<Shared>>, |
| 116 | + known_peers: Vec<TransportPeerId>, |
| 117 | +} |
| 118 | + |
| 119 | +impl MockEndpoint { |
| 120 | + pub fn id(&self) -> TransportPeerId { |
| 121 | + self.id |
| 122 | + } |
| 123 | +} |
| 124 | + |
| 125 | +impl Transport for MockEndpoint { |
| 126 | + fn send(&mut self, to: TransportPeerId, packet: &SyncPacket) -> Result<(), PacketError> { |
| 127 | + packet.encode()?; |
| 128 | + let mut shared = self.shared.lock().unwrap(); |
| 129 | + // A link that dropped since the last poll loses the packet, as a real socket does. |
| 130 | + if self.known_peers.contains(&to) && shared.connected.contains(&self.id) && shared.connected.contains(&to) { |
| 131 | + shared.in_flight.entry((self.id, to)).or_default().push_back(packet.clone()); |
| 132 | + } |
| 133 | + Ok(()) |
| 134 | + } |
| 135 | + |
| 136 | + fn broadcast_except(&mut self, excluded: Option<TransportPeerId>, packet: &SyncPacket) -> Result<(), PacketError> { |
| 137 | + for to in self.known_peers.clone() { |
| 138 | + if Some(to) != excluded { |
| 139 | + self.send(to, packet)?; |
| 140 | + } |
| 141 | + } |
| 142 | + Ok(()) |
| 143 | + } |
| 144 | + |
| 145 | + fn poll(&mut self) -> Vec<TransportEvent> { |
| 146 | + let events: Vec<_> = self.shared.lock().unwrap().inboxes.get_mut(&self.id).map(|inbox| inbox.drain(..).collect()).unwrap_or_default(); |
| 147 | + for event in &events { |
| 148 | + match event { |
| 149 | + TransportEvent::PeerConnected(peer) => self.known_peers.push(*peer), |
| 150 | + TransportEvent::PeerDisconnected(peer) => self.known_peers.retain(|known| known != peer), |
| 151 | + _ => {} |
| 152 | + } |
| 153 | + } |
| 154 | + events |
| 155 | + } |
| 156 | + |
| 157 | + fn close(&mut self) { |
| 158 | + self.shared.lock().unwrap().disconnect(self.id); |
| 159 | + } |
| 160 | +} |
| 161 | + |
| 162 | +struct SplitMix64(u64); |
| 163 | + |
| 164 | +impl SplitMix64 { |
| 165 | + fn next(&mut self) -> u64 { |
| 166 | + self.0 = self.0.wrapping_add(0x9E37_79B9_7F4A_7C15); |
| 167 | + let mut z = self.0; |
| 168 | + z = (z ^ (z >> 30)).wrapping_mul(0xBF58_476D_1CE4_E5B9); |
| 169 | + z = (z ^ (z >> 27)).wrapping_mul(0x94D0_49BB_1331_11EB); |
| 170 | + z ^ (z >> 31) |
| 171 | + } |
| 172 | + |
| 173 | + fn below(&mut self, bound: usize) -> usize { |
| 174 | + (self.next() % bound as u64) as usize |
| 175 | + } |
| 176 | +} |
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