Files
fips/testing/chaos/sim/topology.py
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Johnathan Corgan bf173d8d98 Pin the chaos mesh root to n01 so scenario diagrams describe the real tree
Every chaos scenario draws n01 at the top of its topology, and until now that
held in three of thirteen. The mesh roots itself at the numerically smallest
NodeAddr, which is a hash of the node's public key and bears no relation to the
node numbering, so which node ended up as root was effectively arbitrary.

The consequences were not cosmetic. cost-reeval rooted at n04, its own
designated test subject, so that node had no parent and the periodic parent
switch the scenario exists to observe could not occur at all. mixed-technology
rooted at n09, which put its two documented parent criteria out of reach and
made correct cost-based selection look like a defect.

Identities are still derived from the mesh name exactly as before and are still
deterministic. What changes is which node id holds which one: they are now
assigned in NodeAddr order, so n01 holds the smallest and is the root. Verified
against a model of the daemon's own derivation that reproduces the previously
observed root for every scenario and n01's address byte for byte; all twelve
pinned scenarios now root at n01.

smoke-10 deliberately opts out via pin_root: false so that root election from an
arbitrary key distribution stays exercised somewhere. Its assertion is a
convergence floor and is root-agnostic, which is why it is the cheapest home for
that. The new key is rejected when non-boolean, and a near-miss spelling is
rejected as unknown; both checked.

Not yet established: the trees themselves change, so the parent-dependent
assertions in bottleneck-parent, cost-avoidance and cost-stability need
re-deriving against live runs. Those are held until the in-flight CI finishes,
because a chaos run rebuilds the shared fips-test image that run is using.
2026-07-23 15:43:10 +00:00

417 lines
15 KiB
Python

"""Topology generation: random graphs with connectivity guarantees."""
from __future__ import annotations
import math
import random
from collections import deque
from dataclasses import dataclass, field
from .keys import derive_full
from .naming import name_suffix, veth_token
from .scenario import TopologyConfig
@dataclass
class SimNode:
node_id: str # "n01", "n02", ...
docker_ip: str # "172.20.0.10", ...
nsec: str # 64-char hex
npub: str # bech32 npub1...
peers: list[str] = field(default_factory=list)
# MAC addresses for Ethernet veth interfaces, keyed by peer_id
ethernet_macs: dict[str, str] = field(default_factory=dict)
@dataclass
class SimTopology:
nodes: dict[str, SimNode] = field(default_factory=dict)
edges: set[tuple[str, str]] = field(default_factory=set)
# Per-edge transport type; edges not in this dict default to "udp"
edge_transport: dict[tuple[str, str], str] = field(default_factory=dict)
# Suffix scoping globally-visible names to this run and scenario; empty
# outside the CI harness, which keeps a bare run's names unchanged.
name_suffix: str = ""
@property
def veth_token(self) -> str:
"""Short stand-in for the suffix, for names bound by IFNAMSIZ.
Derived rather than stored so no caller can build a topology whose
host names are scoped differently from its container names.
"""
return veth_token(self.name_suffix)
def transport_for_edge(self, a: str, b: str) -> str:
"""Get the transport type for an edge (defaults to 'udp')."""
edge = _make_edge(a, b)
return self.edge_transport.get(edge, "udp")
def ethernet_edges(self) -> list[tuple[str, str]]:
"""Return all edges using Ethernet transport."""
return [e for e, t in self.edge_transport.items() if t == "ethernet"]
def has_ethernet(self) -> bool:
"""Check if any edges use Ethernet transport."""
return any(t == "ethernet" for t in self.edge_transport.values())
def tcp_edges(self) -> list[tuple[str, str]]:
"""Return all edges using TCP transport."""
return [e for e, t in self.edge_transport.items() if t == "tcp"]
def has_tcp(self) -> bool:
"""Check if any edges use TCP transport."""
return any(t == "tcp" for t in self.edge_transport.values())
def tcp_peers(self, node_id: str) -> list[str]:
"""Return peer IDs connected to this node via TCP."""
peers = []
for (a, b), transport in self.edge_transport.items():
if transport != "tcp":
continue
if a == node_id:
peers.append(b)
elif b == node_id:
peers.append(a)
return sorted(peers)
def ethernet_interfaces(self, node_id: str) -> list[str]:
"""Return the veth interface names for a node's Ethernet edges."""
ifaces = []
for (a, b), transport in self.edge_transport.items():
if transport != "ethernet":
continue
if a == node_id:
ifaces.append(veth_interface_name(a, b))
elif b == node_id:
ifaces.append(veth_interface_name(b, a))
return sorted(ifaces)
def is_connected(self) -> bool:
"""BFS connectivity check."""
if len(self.nodes) <= 1:
return True
start = next(iter(self.nodes))
visited = set()
queue = deque([start])
while queue:
node = queue.popleft()
if node in visited:
continue
visited.add(node)
for peer in self.nodes[node].peers:
if peer not in visited:
queue.append(peer)
return len(visited) == len(self.nodes)
def neighbors(self, node_id: str) -> list[str]:
return self.nodes[node_id].peers
def would_disconnect(self, edge: tuple[str, str]) -> bool:
"""Check if removing this edge would disconnect the graph."""
a, b = edge
# Temporarily remove edge
self.nodes[a].peers.remove(b)
self.nodes[b].peers.remove(a)
connected = self.is_connected()
# Restore
self.nodes[a].peers.append(b)
self.nodes[b].peers.append(a)
return not connected
def container_name(self, node_id: str) -> str:
return f"fips-node-{node_id}{self.name_suffix}"
def veth_host_name(self, node_a: str, node_b: str, end: str) -> str:
"""Generate the host-namespace veth name for one end of an edge.
Format: ``vh{token}{NN}{MM}{end}`` (max 15 chars for IFNAMSIZ).
Host interfaces are global, so the token keeps a scenario from
deleting a concurrent scenario's pair; it is empty outside the CI
harness, yielding the same "vh0104a" this has always produced.
``node_a`` and ``node_b`` must be in canonical edge order. Unlike
``veth_interface_name()`` this is not symmetric: the far end is
``end="b"`` on the same ordering, so swapping the arguments names
an interface that does not exist.
"""
nn_local = node_a.replace("n", "")
nn_peer = node_b.replace("n", "")
name = f"vh{self.veth_token}{nn_local}{nn_peer}{end}"
if len(name) > 15:
raise ValueError(f"veth host name too long: {name!r} ({len(name)} > 15)")
return name
def directed_outbound(self) -> dict[str, list[str]]:
"""Assign each static-config edge to exactly one node for outbound connection.
Returns a mapping from node_id to the list of peers that node
should connect to (outbound only). Every edge appears in exactly
one direction, ensuring auto-reconnect is testable — if B goes
down, only A (the outbound owner) will attempt to reconnect.
Ethernet edges are excluded — they use beacon discovery instead
of static peer configuration. UDP and TCP edges use static config.
Strategy: BFS spanning tree edges go parent→child. Non-tree
edges go from the lower node ID to the higher. This guarantees
every node is reachable via at least one inbound connection.
"""
# Consider all edges that use static peer config (not Ethernet/discovery)
static_edges = {
e for e in self.edges
if self.edge_transport.get(e, "udp") != "ethernet"
}
outbound: dict[str, list[str]] = {nid: [] for nid in self.nodes}
# Build static-config adjacency for BFS
static_adj: dict[str, list[str]] = {nid: [] for nid in self.nodes}
for a, b in static_edges:
static_adj[a].append(b)
static_adj[b].append(a)
# BFS spanning tree from first node (over static-config edges only)
root = min(self.nodes)
visited: set[str] = set()
tree_edges: set[tuple[str, str]] = set()
queue = deque([root])
visited.add(root)
while queue:
node = queue.popleft()
for peer in static_adj[node]:
if peer not in visited:
visited.add(peer)
queue.append(peer)
tree_edges.add((node, peer)) # parent → child
outbound[node].append(peer)
# Non-tree static-config edges: lower ID → higher ID
for a, b in static_edges:
if (a, b) not in tree_edges and (b, a) not in tree_edges:
outbound[a].append(b) # a < b by _make_edge convention
return outbound
def generate_topology(
config: TopologyConfig,
rng: random.Random,
mesh_name: str,
) -> SimTopology:
"""Generate a topology according to the config."""
n = config.num_nodes
subnet_base = config.subnet.rsplit(".", 1)[0] # "172.20.0"
# Create nodes with IPs and keys.
#
# The mesh roots itself at the numerically smallest NodeAddr
# (`src/tree/state.rs:363-390`), which is a hash of the node's public key
# and so bears no relation to the node numbering. Every scenario diagram in
# this tree draws n01 at the top, and before this ordering was applied that
# held in only three of thirteen: `cost-reeval` rooted at n04 — its own
# designated test subject, which therefore had no parent to switch and could
# not exercise what the scenario exists to test — and `mixed-technology` at
# n09, which made its two documented parent criteria unreachable.
#
# So derive the identities from the mesh name as before, then *assign* them
# in NodeAddr order: n01 receives the smallest and is the root, n02 the next,
# and so on. The keys are unchanged and still deterministic; only which node
# id holds which one changes. Scenarios that want an arbitrary root set
# `pin_root: false` and keep exercising election.
node_ids_ordered = [f"n{i + 1:02d}" for i in range(n)]
identities = [derive_full(mesh_name, nid) for nid in node_ids_ordered]
if config.pin_root:
identities.sort(key=lambda t: t[2])
nodes: dict[str, SimNode] = {}
for i, node_id in enumerate(node_ids_ordered):
docker_ip = f"{subnet_base}.{config.ip_start + i}"
nsec, npub, _ = identities[i]
nodes[node_id] = SimNode(
node_id=node_id,
docker_ip=docker_ip,
nsec=nsec,
npub=npub,
)
node_ids = sorted(nodes.keys())
# Generate edges
if config.algorithm == "chain":
edges = _generate_chain(node_ids)
elif config.algorithm == "random_geometric":
radius = config.params.get("radius", 0.5)
edges = _generate_random_geometric(node_ids, radius, rng)
elif config.algorithm == "erdos_renyi":
p = config.params.get("p", 0.3)
edges = _generate_erdos_renyi(node_ids, p, rng)
elif config.algorithm == "explicit":
adjacency = config.params.get("adjacency")
if not adjacency:
raise ValueError("explicit topology requires params.adjacency")
edges, edge_transport = _generate_explicit(
adjacency, config.default_transport
)
# Validate all referenced nodes exist
for a, b in edges:
if a not in nodes:
raise ValueError(f"explicit adjacency references unknown node {a}")
if b not in nodes:
raise ValueError(f"explicit adjacency references unknown node {b}")
else:
raise ValueError(f"Unknown algorithm: {config.algorithm}")
# Assign transport types to edges
if config.algorithm != "explicit":
edge_transport = _assign_edge_transports(edges, config, rng)
# Build peer lists from edges
for a, b in edges:
nodes[a].peers.append(b)
nodes[b].peers.append(a)
# Read the environment once, here, so every name a run produces comes
# from the same value.
topo = SimTopology(
nodes=nodes,
edges=edges,
edge_transport=edge_transport,
name_suffix=name_suffix(),
)
# Connectivity check with retry
if config.ensure_connected:
max_retries = 50
attempt = 0
while not topo.is_connected() and attempt < max_retries:
attempt += 1
# Clear and regenerate
for node in nodes.values():
node.peers.clear()
if config.algorithm == "random_geometric":
edges = _generate_random_geometric(node_ids, radius, rng)
elif config.algorithm == "erdos_renyi":
edges = _generate_erdos_renyi(node_ids, p, rng)
else:
break # chain is always connected
for a, b in edges:
nodes[a].peers.append(b)
nodes[b].peers.append(a)
topo.edges = edges
topo.edge_transport = _assign_edge_transports(edges, config, rng)
if not topo.is_connected():
raise RuntimeError(
f"Failed to generate connected topology after {max_retries} attempts"
)
return topo
def _generate_chain(node_ids: list[str]) -> set[tuple[str, str]]:
"""Linear topology: n01-n02-n03-..."""
edges = set()
for i in range(len(node_ids) - 1):
edge = _make_edge(node_ids[i], node_ids[i + 1])
edges.add(edge)
return edges
def _generate_random_geometric(
node_ids: list[str],
radius: float,
rng: random.Random,
) -> set[tuple[str, str]]:
"""Place nodes randomly in [0,1]^2, connect if distance < radius."""
positions = {nid: (rng.random(), rng.random()) for nid in node_ids}
edges = set()
for i, a in enumerate(node_ids):
for b in node_ids[i + 1 :]:
ax, ay = positions[a]
bx, by = positions[b]
dist = math.sqrt((ax - bx) ** 2 + (ay - by) ** 2)
if dist < radius:
edges.add(_make_edge(a, b))
return edges
def _generate_erdos_renyi(
node_ids: list[str],
p: float,
rng: random.Random,
) -> set[tuple[str, str]]:
"""Include each edge with probability p."""
edges = set()
for i, a in enumerate(node_ids):
for b in node_ids[i + 1 :]:
if rng.random() < p:
edges.add(_make_edge(a, b))
return edges
def _generate_explicit(
adjacency: list, default_transport: str = "udp"
) -> tuple[set[tuple[str, str]], dict[tuple[str, str], str]]:
"""Build edges from an explicit adjacency list.
Each entry is a 2-element list ``[nodeA, nodeB]`` (uses default
transport) or a 3-element list ``[nodeA, nodeB, transport]``.
Returns ``(edges, edge_transport)`` where ``edge_transport`` maps
each edge to its transport type.
"""
edges = set()
edge_transport: dict[tuple[str, str], str] = {}
for i, entry in enumerate(adjacency):
if not isinstance(entry, (list, tuple)) or len(entry) not in (2, 3):
raise ValueError(
f"explicit adjacency[{i}]: expected [nodeA, nodeB] or "
f"[nodeA, nodeB, transport], got {entry}"
)
edge = _make_edge(str(entry[0]), str(entry[1]))
edges.add(edge)
transport = str(entry[2]) if len(entry) == 3 else default_transport
edge_transport[edge] = transport
return edges, edge_transport
def _assign_edge_transports(
edges: set[tuple[str, str]],
config: TopologyConfig,
rng: random.Random,
) -> dict[tuple[str, str], str]:
"""Assign transport types to edges.
If ``config.transport_mix`` is set, each edge is randomly assigned
a transport based on the mix weights. Otherwise all edges use
``config.default_transport``.
"""
if config.transport_mix is None:
return {e: config.default_transport for e in edges}
transports = list(config.transport_mix.keys())
weights = [config.transport_mix[t] for t in transports]
assignments = rng.choices(transports, weights=weights, k=len(edges))
return dict(zip(sorted(edges), assignments))
def veth_interface_name(local: str, peer: str) -> str:
"""Generate the veth interface name inside a container.
Format: ``ve-{local}-{peer}`` (max 15 chars for IFNAMSIZ).
For typical node IDs like "n01", this yields "ve-n01-n02" (10 chars).
"""
name = f"ve-{local}-{peer}"
if len(name) > 15:
raise ValueError(f"veth interface name too long: {name!r} ({len(name)} > 15)")
return name
def _make_edge(a: str, b: str) -> tuple[str, str]:
"""Canonical edge representation (sorted)."""
return (min(a, b), max(a, b))