Forward-merge the STP sans-IO migration. The classify / proto-stp structure,
clock injection, crypto field-partition, and BTree collections come from the
master line; next's non-full/leaf parent-candidacy skip is preserved by passing
self.non_full_peers() at the four shell call sites (handle_tree_announce,
check_periodic_parent_reeval, the MMP first-RTT re-eval, and the greedy-tree
find_next_hop fallback) instead of an empty set, with non_full_peers returning a
BTreeSet. next's four non_full_peers skip tests fold into proto/stp/tests.
Migrate the full non-async spanning-tree surface into proto/stp/, mirroring the
discovery/routing/fmp/mmp conversions. The classification ladder (parent-switch /
self-root / loop-drop / ancestry-update / periodic-rebroadcast / parent-lost) moves
out of the async node handlers into a pure Stp classify layer returning a
TreeDecision the shell drives, with effect ordering and per-arm invalidation
preserved verbatim. src/tree/ relocates wholesale: TreeState + ParentDeclaration data
+ coordinates into proto/stp/{state,coordinate}, the flap-dampening / hold-down
cluster into a FlapDampener in limits.rs, and the wire codec into wire.rs. The clock
is injected as u64 (wall-clock secs for the escaping declaration timestamp, monotonic
ms for the dampening timers via mmp::mono_ms); declaration crypto is field-partitioned
so sign/verify/hash run in the shell while the in-core modules carry data +
signing_bytes only. Peer maps/sets move to BTree; core/state/coordinate/limits are
core+alloc clean, with wire.rs the one std-tethered file. Behavior-neutral:
characterization tests added for the handler decision arms; convergence suite and
ci-local (36/36) green.
- Delete PROTOCOL_NAME_IK, PROTOCOL_NAME_XK and all IK/XK methods
- Remove Ik/Xk variants from NoisePattern enum
- Rename XX methods to drop xx_ prefix (sole pattern)
- Rename HandshakeMessageType variants from NoiseIKMsg1/NoiseIKMsg2
to Msg1/Msg2, add Msg3 variant (0x03) for XX 3-message flow
- Fix doc comments with correct XX message sizes and descriptions
- Fix stale SessionSetup/SessionAck handshake payload size comments
Breaking wire format change: DataPacket payloads inside the AEAD envelope
now carry a 4-byte port header [src_port:2 LE][dst_port:2 LE] before the
service payload. The receiver dispatches by destination port.
Port multiplexing:
- send_session_data() takes src_port/dst_port params, prepends port header
- New send_ipv6_packet() compresses IPv6 header and sends on port 256
- Receive path dispatches DataPackets by port: port 256 decompresses IPv6
header from session context and delivers to TUN, unknown ports dropped
- Port constants: FSP_PORT_HEADER_SIZE (4 bytes), FSP_PORT_IPV6_SHIM (256)
IPv6 header compression:
- New ipv6_shim module with compress_ipv6()/decompress_ipv6() pure functions
- Strips src/dst addresses (32 bytes) and payload length (2 bytes) from each
packet, preserving traffic class, flow label, next header, and hop limit
as 6-byte residual fields
- Addresses reconstructed from session context on receive side
- Net savings: 29 bytes per packet (overhead 106 → 77 bytes)
- FIPS_IPV6_OVERHEAD constant (77 bytes), effective_ipv6_mtu() updated
- 16 unit tests for round-trip fidelity, field preservation, error cases
Documentation:
- fips-wire-formats: DataPacket port header, port registry, IPv6 shim
format tables, updated encapsulation walkthrough and overhead budget
- fips-ipv6-adapter: FIPS_IPV6_OVERHEAD (77 bytes), updated MTU numbers,
TUN reader/writer flow with compression steps, impl status
- fips-session-layer: port-based service dispatch section, data transfer
description, impl status
- fips-intro: IPv6 adapter as port 256 service, node architecture updated
- fips-mesh-operation: packet size summary with compressed overhead
- DataPacket doc updated with port header and dispatch model
- session_wire.rs module doc: DataPacket Port Multiplexing section
The session-layer handshake now uses the 3-message XK pattern instead
of the 2-message IK pattern, providing stronger initiator identity
hiding. The initiator static key is deferred to msg3 and encrypted
under the es+ee DH chain, so eavesdroppers cannot identify the
initiator from the handshake.
XK pattern: -> e, es (msg1) / <- e, ee + epoch (msg2) / -> s, se + epoch (msg3)
Key changes:
- Add XK handshake methods alongside existing IK methods in noise module
- Add SessionMsg3 wire format and FSP_PHASE_MSG3 (0x03) prefix
- Replace Responding state with AwaitingMsg3 in session state machine
- Rewrite session handlers: handle_session_setup defers identity to msg3,
handle_session_ack processes msg2 and sends msg3, new handle_session_msg3
completes the responder handshake and registers identity
- Link-layer (FMP) continues to use Noise IK unchanged
- Add comprehensive XK unit tests and update all integration tests
Rename FIPS Link Protocol (FLP) to FIPS Mesh Protocol (FMP)
The "Link Protocol" name understated the layer's scope — spanning tree
construction, bloom filter routing, greedy forwarding, and mesh-wide
coordination go well beyond link-level concerns. Rename fips-link-layer.md
to fips-mesh-layer.md, update FLP→FMP throughout docs and source code
(FLP_VERSION→FMP_VERSION, wire.rs, rx_loop.rs, spanning_tree.rs).
New SVG illustrations
- Protocol stack: color-coded layer diagram replacing ASCII art
- OSI mapping: side-by-side comparison with traditional networking layers
- Bloom filter propagation: 6-node tree with sender-colored filter boxes
showing split-horizon computation per link
- Routing decision flowchart: 5-step priority chain with candidate ranking
by tree distance and link performance
- Coordinate discovery: sequence diagram showing LookupRequest propagation,
response caching, and SessionSetup cache warming
Redesigned existing SVGs
- Architecture overview: uniform node layout, U-shaped encrypted link
connectors, separate end-to-end session line
- Node architecture: split Router Core into FSP and FMP layers, reorganize
transports into Overlay/Shared Medium/Point-to-Point categories
- Identity derivation: wider boxes, visible encode arrow, dashed npub line
fips-intro.md revisions
- Add inline references to prior work: Yggdrasil/Ironwood for coordinate
routing, Noise Protocol Framework for IK handshakes, WireGuard for
index-based session dispatch, Wikipedia for bloom filters, split-horizon,
and greedy embedding
- Add explanatory paragraphs after bloom filter diagram describing
split-horizon filter computation and candidate selection behavior
- Simplify transport abstraction language, remove I2P/LoRa references
- Fix LookupRequest wording ("propagates" not "floods"), note intermediate
node coordinate caching on lookup responses
- Rewrite architecture overview prose to match redesigned diagrams
Johnathan Corgan