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session: drop dead SessionSetup/SessionAck variants
Both variants of SessionMessageType were never emitted anywhere in src/, and the production from_byte dispatch sites lacked Some-arms for them — any 0x00/0x01 byte that reached either dispatcher would log "Unknown..." and drop. The matching rustdoc tables described an Offset 0 msg_type byte that the encode() path has never written; the actual wire format is the FSP common prefix [ver_phase][flags][payload_len:2 LE] with body keyed by phase nibble, as documented in docs/reference/wire-formats.md. Drop the variants, drop their from_byte/to_byte/Display arms, fix the two stale rustdoc tables to describe the real wire shape, and trim the variant-iteration unit test that enumerated them. Zero on-wire behaviour change.
This commit is contained in:
Johnathan Corgan
+44
-34
@@ -16,15 +16,14 @@ use std::fmt;
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/// encrypted with session keys via the FSP pipeline. Error signals
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/// (CoordsRequired, PathBroken) are plaintext messages generated by transit
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/// routers that cannot establish e2e sessions with the source.
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///
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/// Handshake messages (SessionSetup, SessionAck, SessionMsg3) are **not**
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/// identified by a message-type byte; they are dispatched by the FSP phase
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/// nibble in the common prefix (0x1, 0x2, 0x3 respectively). The 0x00-0x0F
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/// range is therefore unallocated in this enum.
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#[derive(Clone, Copy, Debug, PartialEq, Eq)]
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#[repr(u8)]
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pub enum SessionMessageType {
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// Session establishment (0x00-0x0F)
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/// Session setup with coordinates (warms router caches).
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SessionSetup = 0x00,
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/// Session acknowledgement.
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SessionAck = 0x01,
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// Data and metrics (0x10-0x1F) — encrypted, inner header msg_type
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/// Port-multiplexed service payload: `[src_port:2 LE][dst_port:2 LE][service data...]`.
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/// Port 256 = IPv6 shim (compressed header). Receiver dispatches by dst_port.
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@@ -51,8 +50,6 @@ impl SessionMessageType {
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/// Try to convert from a byte.
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pub fn from_byte(b: u8) -> Option<Self> {
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match b {
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0x00 => Some(SessionMessageType::SessionSetup),
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0x01 => Some(SessionMessageType::SessionAck),
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0x10 => Some(SessionMessageType::DataPacket),
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0x11 => Some(SessionMessageType::SenderReport),
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0x12 => Some(SessionMessageType::ReceiverReport),
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@@ -74,8 +71,6 @@ impl SessionMessageType {
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impl fmt::Display for SessionMessageType {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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let name = match self {
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SessionMessageType::SessionSetup => "SessionSetup",
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SessionMessageType::SessionAck => "SessionAck",
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SessionMessageType::DataPacket => "DataPacket",
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SessionMessageType::SenderReport => "SenderReport",
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SessionMessageType::ReceiverReport => "ReceiverReport",
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@@ -330,20 +325,29 @@ impl FspInnerFlags {
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///
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/// Carried inside a SessionDatagram envelope which provides src_addr and
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/// dest_addr. The SessionSetup payload contains coordinates, session flags,
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/// and the Noise IK handshake message for session establishment.
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/// and the Noise XK handshake message for session establishment.
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///
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/// SessionSetup, SessionAck, and SessionMsg3 are identified by the **phase**
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/// field in the FSP common prefix (0x1, 0x2, 0x3), not by a message-type byte.
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/// The `msg_type` field in the encrypted inner header applies only to
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/// established-phase (0x0) messages.
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///
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/// ## Wire Format
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///
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/// | Offset | Field | Size | Description |
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/// |--------|------------------|---------|-------------------------------------|
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/// | 0 | msg_type | 1 byte | 0x00 |
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/// | 1 | flags | 1 byte | Bit 0: REQUEST_ACK, Bit 1: BIDIR |
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/// | 2 | src_coords_count | 2 bytes | u16 LE, number of src coord entries |
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/// | 4 | src_coords | 16 × n | NodeAddr array (self → root) |
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/// | ... | dest_coords_count| 2 bytes | u16 LE, number of dest coord entries|
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/// | ... | dest_coords | 16 × m | NodeAddr array (dest → root) |
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/// | ... | handshake_len | 2 bytes | u16 LE, Noise payload length |
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/// | ... | handshake_payload| variable| Noise IK msg1 (82 bytes typical) |
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/// Encoded with FSP common prefix: `[ver_phase:1][flags:1][payload_len:2 LE][body]`,
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/// where `ver_phase = 0x01` (version 0, phase MSG1) and `flags = 0` for handshake.
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///
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/// **Body** (after 4-byte FSP prefix):
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///
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/// | Offset | Field | Size | Description |
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/// |--------|-------------------|------------|-----------------------------------------------------|
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/// | 0 | flags | 1 byte | Bit 0: REQUEST_ACK, Bit 1: BIDIRECTIONAL |
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/// | 1 | src_coords_count | 2 bytes LE | Number of source coordinate entries |
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/// | 3 | src_coords | 16 × n | Source's ancestry (NodeAddr, self → root) |
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/// | ... | dest_coords_count | 2 bytes LE | Number of dest coordinate entries |
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/// | ... | dest_coords | 16 × m | Destination's ancestry |
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/// | ... | handshake_len | 2 bytes LE | Noise payload length |
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/// | ... | handshake_payload | variable | Noise XK msg1 (33 bytes — ephemeral key only) |
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#[derive(Clone, Debug)]
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pub struct SessionSetup {
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/// Source coordinates (for return path caching).
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@@ -456,20 +460,27 @@ impl SessionSetup {
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/// dest_addr. The SessionAck payload contains both the acknowledger's and
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/// initiator's coordinates for route cache warming (ensuring return-path
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/// transit nodes can route independently of the forward path) and the Noise
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/// IK handshake response.
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/// XK handshake response.
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///
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/// SessionSetup, SessionAck, and SessionMsg3 are identified by the **phase**
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/// field in the FSP common prefix (0x1, 0x2, 0x3), not by a message-type byte.
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///
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/// ## Wire Format
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///
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/// | Offset | Field | Size | Description |
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/// |--------|------------------|---------|-------------------------------------|
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/// | 0 | msg_type | 1 byte | 0x01 |
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/// | 1 | flags | 1 byte | Reserved |
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/// | 2 | src_coords_count | 2 bytes | u16 LE |
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/// | 4 | src_coords | 16 × n | Acknowledger's coords (for caching) |
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/// | ... | dest_coords_count| 2 bytes | u16 LE |
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/// | ... | dest_coords | 16 × m | Initiator's coords (for return path)|
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/// | ... | handshake_len | 2 bytes | u16 LE, Noise payload length |
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/// | ... | handshake_payload| variable| Noise IK msg2 (33 bytes typical) |
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/// Encoded with FSP common prefix: `[ver_phase:1][flags:1][payload_len:2 LE][body]`,
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/// where `ver_phase = 0x02` (version 0, phase MSG2) and `flags = 0` for handshake.
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///
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/// **Body** (after 4-byte FSP prefix):
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///
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/// | Offset | Field | Size | Description |
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/// |--------|-------------------|------------|--------------------------------------------------------------|
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/// | 0 | flags | 1 byte | Reserved |
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/// | 1 | src_coords_count | 2 bytes LE | Number of acknowledger coordinate entries |
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/// | 3 | src_coords | 16 × n | Acknowledger's ancestry (for cache warming) |
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/// | ... | dest_coords_count | 2 bytes LE | Number of initiator coordinate entries |
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/// | ... | dest_coords | 16 × m | Initiator's ancestry (for return-path cache warming) |
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/// | ... | handshake_len | 2 bytes LE | Noise payload length |
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/// | ... | handshake_payload | variable | Noise XK msg2 (57 bytes — ephemeral key + encrypted epoch) |
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#[derive(Clone, Debug)]
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pub struct SessionAck {
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/// Acknowledger's coordinates.
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@@ -1156,12 +1167,11 @@ mod tests {
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#[test]
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fn test_session_message_type_roundtrip() {
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let types = [
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SessionMessageType::SessionSetup,
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SessionMessageType::SessionAck,
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SessionMessageType::DataPacket,
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SessionMessageType::SenderReport,
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SessionMessageType::ReceiverReport,
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SessionMessageType::PathMtuNotification,
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SessionMessageType::CoordsWarmup,
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SessionMessageType::CoordsRequired,
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SessionMessageType::PathBroken,
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SessionMessageType::MtuExceeded,
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