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The Flow and Retransmission Control Protocol (FRCP) runs end-to-end
between two peers over a flow. It provides reliability, in-order
delivery, flow control, and liveness. Note that congestion avoidance
is orthogonal to FRCP and handled in the IPCP.
A fixed 16-octet header, network byte order, is prefixed to every FRCP
packet:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| flags | hcs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| window |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| seqno |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ackno |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| payload (variable) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
hcs is a CRC-16-CCITT-FALSE checksum over the PCI (and the stream
extension when present), verified before any flag-driven dispatch. A
single packet can simultaneously carry DATA + ACK + FC + RXM by OR-ing
flag bits. An optional CRC trailer covers the body on DATA when qs.ber
== 0, and on every SACK packet; an optional AEAD wrap (per-flow keys)
sits outermost.
Flag bits (MSB-first; bits 13..15 reserved, MUST be zero):
+------+--------+--------+----------------------------------------+
| Bit | Mask | Name | Meaning |
+------+--------+--------+----------------------------------------+
| 0 | 0x8000 | DATA | Carries caller payload |
| 1 | 0x4000 | DRF | Start of a fresh data run |
| 2 | 0x2000 | ACK | ackno field valid |
| 3 | 0x1000 | NACK | Pre-DRF nudge (seqno informational) |
| 4 | 0x0800 | FC | window field valid (rwe advertisement) |
| 5 | 0x0400 | RDVS | Rendezvous probe (window-closed) |
| 6 | 0x0200 | FFGM | First Fragment of a multi-fragment SDU |
| 7 | 0x0100 | LFGM | Last Fragment of a multi-fragment SDU |
| 8 | 0x0080 | RXM | Retransmission |
| 9 | 0x0040 | SACK | Block list follows in payload |
| 10 | 0x0020 | RTTP | RTT probe / echo (payload follows) |
| 11 | 0x0010 | KA | Keepalive |
| 12 | 0x0008 | FIN | End of stream marker |
| 13-15| -- | -- | Reserved (MUST be zero) |
+------+--------+--------+----------------------------------------+
(FFGM, LFGM) encodes the fragment role of a DATA packet (SCTP-style
B/E): 11=SOLE, 10=FIRST, 00=MID, 01=LAST. Each fragment carries its
own seqno; Retransmission recovers fragments individually, reassembly
runs at consume time. In stream mode FFGM/LFGM are unused; per-byte
position is carried by the stream extension below and end-of-stream is
signalled by FIN on a 0-byte DATA packet.
SACK payload (FRCT_ACK | FRCT_FC | FRCT_SACK):
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| n_blocks | padding (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| start[0] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| end[0] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... n_blocks pairs total ...
Each block describes a *present* (received) range strictly above the
cumulative ACK in the PCI ackno. D-SACK (RFC 2883) is signalled
in-band as block[0] - no flag bit, no extra framing - and consumed by
the RACK reo_wnd_mult scaler (RFC 8985 sec. 7.2).
RTTP payload (FRCT_RTTP only; 24 octets):
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| probe_id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| echo_id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ nonce (16 octets, echoed verbatim) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Stream PCI extension (in_order == STREAM only; 8 octets after the base
PCI on every DATA packet):
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| start |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| end |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
start, end are monotonic 32-bit byte offsets; end - start equals the
on-wire payload length. Stream mode is negotiated at flow allocation;
the extension is present iff stream mode is in use, never on a
per-packet basis.
Service modes are an orthogonal (in_order, loss, ber) vector selected
at flow_alloc; the cubes above map to the axes:
+----------------+---------+------+-----+-----------------------+
| Cube | in_order| loss | ber | Engaged |
+----------------+---------+------+-----+-----------------------+
| qos_raw | 0 | 1 | 1 | Raw passthrough |
| qos_raw_safe | 0 | 1 | 0 | Raw + CRC trailer |
| qos_rt | 1 | 1 | 1 | FRCP, no FRTX, no CRC |
| qos_rt_safe | 1 | 1 | 0 | FRCP, no FRTX, CRC |
| qos_msg | 1 | 0 | 0 | FRCP + FRTX |
| qos_stream | 2 | 0 | 0 | FRCP + FRTX, stream |
+----------------+---------+------+-----+-----------------------+
in_order=0 sends raw datagrams with no PCI (UDP-equivalent);
in_order=1 engages FRCP with SDU framing; in_order=2 (stream) requires
loss=0 and is rejected otherwise. loss=0 engages the FRTX retransmit
machinery. ber=0 appends the CRC-32 trailer; QOS_DISABLE_CRC at build
time forces ber=1 for development. Encryption is a separate per-flow
attribute layered as an AEAD wrap outside the FRCP packet.
Heritage: delta-t (Watson 1981) supplies timer-based connection
management - no SYN/FIN handshake, the DRF marker, the t_mpl / t_a /
t_r timers. RINA (Day 2008) supplies the unified flow_alloc(name, qos,
...) primitive and the orthogonal QoS-cube axes. Loss detection
follows TCP/QUIC practice (RFCs 2018, 2883, 6582, 6298, 8985); RTT
probing is nonce-authenticated like QUIC PATH_CHALLENGE.
Adds oftp, a minimal file-transfer tool over an FRCP stream flow. The
client reads from stdin or --in FILE and writes through a
flow_alloc(qos_stream); the server (--listen) calls flow_accept and
writes to stdout or --out FILE. Both sides compute a CRC-64/NVMe over
the bytes they handle and print the result. The server rejects flows
whose negotiated qs.in_order != STREAM.
Two FRCP knobs are exposed via env vars on either side:
OFTP_FRCT_RTO_MIN fccntl FRCTSRTOMIN (ns)
OFTP_FRCT_STREAM_RING_SZ fccntl FRCTSRRINGSZ (octets)
The ocbr_client gains an OCBR_QOS env var to pick the cube the client
uses for flow_alloc; recognised values are raw, safe, rt, rt_safe,
msg, stream. Unknown values fall back to raw with a warning on
stderr. Without the env set behaviour is unchanged.
Removes the deprecated lib/timerwheel.c
Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>
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This moves the build definitions back to src/ subdirectories
(CMakeLists.txt per component). Configuration and dependencies are
kept out of tree. Configuration options are bundled into cmake/config/
modules. Dependencies are grouped by component (system/, crypt/, eth/,
coverage/, etc.). It now consistently uses target-based commands
(target_include_directories, target_link_libraries) instead of global
include_directories(). Proper PRIVATE/PUBLIC visibility for executable
link libraries. CONFIG_OUROBOROS_DEBUG now properly set based on being
a valid debug config (not just checking the string name).
It also adds OuroborosTargets export for find_package() support and
CMake package config files (OuroborosConfig.cmake) for easier
integration with CMake projects.
The build logic now follows more idiomatic CMake practices with
configuration separated from target definitions.
Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>
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