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Johnathan Corgan
d41009b778
Add src_addr to SessionDatagram envelope (34-byte header: msg_type + src_addr + dest_addr + hop_limit) so transit routers can route error signals back to the packet's originator. Reclassify CoordsRequired/PathBroken as link-layer error signals (plaintext inside SessionDatagram) rather than e2e encrypted session messages. Transit routers generate these when forwarding fails and route them to src_addr; if source is also unreachable, drop silently. Remove redundant src_addr/dest_addr/hop_limit from SessionSetup, SessionAck, and DataPacket (now in envelope). DataPacket header reduced from 36 to 4 bytes. Remove PathBroken.original_src. Fix routing loop vulnerability: gate bloom filter path on having cached dest_coords to prevent blind forwarding between peers. Simplify select_best_candidate() to require coordinates. Fix gossip protocol type codes (0x11->0x20, 0x12->0x30, 0x13->0x31) for consistency across all design docs. All 5 design docs updated and cross-checked for consistency. 335 tests pass, zero warnings.
FIPS Design Documents
Protocol design specifications and analysis for the Federated Interoperable Peering System.
Suggested Reading Order
Start with the high-level architecture, then work through session flow, routing concepts, and finally the wire-level protocol details.
1. Introduction and Overview
| Document | Description |
|---|---|
| fips-intro.md | Protocol introduction: goals, concepts, architecture |
2. Protocol Flow (How Traffic Works)
| Document | Description |
|---|---|
| fips-session-protocol.md | End-to-end session flow, Noise IK encryption, terminology |
3. Routing (How Packets Find Their Way)
| Document | Description |
|---|---|
| fips-routing.md | Routing concepts: bloom filters, discovery, greedy routing |
| spanning-tree-dynamics.md | Tree protocol behavior: convergence, partitions, recovery |
| fips-gossip-protocol.md | Wire formats: TreeAnnounce, FilterAnnounce, Lookup messages |
4. Link Layer (How Peer Connections Work)
| Document | Description |
|---|---|
| fips-wire-protocol.md | Transport layer: Noise IK, session indices, roaming, security |
| fips-transports.md | Transport-specific: UDP, Ethernet, Tor, radio characteristics |
Implementation
| Document | Description |
|---|---|
| fips-architecture.md | Software architecture: entities, state machines, configuration |
| fips-tun-driver.md | TUN interface driver: reader/writer threads, ICMPv6, packet flow |
| fips-state-machines.md | Phase-based state machine pattern: peer lifecycle, transitions |
Document Cross-References
fips-intro.md
│
┌────────────┴────────────┐
▼ ▼
fips-session-protocol.md fips-architecture.md
│ │
┌─────────┴─────────┐ ▼
▼ ▼ fips-transports.md
fips-routing.md fips-wire-protocol.md
│ │
▼ ▼
spanning-tree-dynamics.md ←→ fips-gossip-protocol.md