feat: HTTP-Server der Recovery-Station

Liefert ausschliesslich Images aus, deren Name dem Muster
ninlight_<target>_ota.img entspricht, unterstuetzt Range-Anfragen fuer
den Wiederaufnahmeversuch der Firmware und schreibt seinen Zustand nach
status.json - die Schnittstelle fuer die E-Paper-Anzeige in 4c.

Behebt zwei Races aus der Referenzimplementierung des Task-Briefs: der
Server trug Erfolg/404 erst nach dem letzten gesendeten Byte in
status.json ein, wodurch ein Client, der die Antwort vollstaendig
gelesen hat, noch den alten Zustand sehen konnte. Ausserdem wurde ein
ganzer 32-KiB-Chunk auch dann komplett gesendet, wenn --stall-after
schon ueberschritten war; die Lesegroesse wird jetzt an die Stall-Grenze
gekappt, und ein Verbindungsabbruch waehrend des Stalls wird per
select/MSG_PEEK erkannt und als "aborted" vermerkt statt den Thread
endlos zu blockieren.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
This commit is contained in:
Michael Sauer
2026-09-12 11:45:05 +02:00
co-authored by Claude Sonnet 5
parent 76a3253322
commit 37f4dd425e
3 changed files with 453 additions and 0 deletions
+230
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#!/usr/bin/env python3
"""ninlight recovery station.
Serves firmware images to lamps that look for a rescue station while booting. Deliberately
minimal: it hands out nothing but files whose name matches ninlight_<target>_ota.img, so a
stray file in the image directory can never leave the machine.
Standard library only - the Pi gets no extra packages.
"""
from __future__ import annotations
import argparse
import json
import os
import re
import select
import socket
import sys
import tempfile
import time
from datetime import datetime, timezone
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
from pathlib import Path
TARGETS = ("evk", "e27_rgb", "e14_rgb", "gu10_rgb", "e27_cw", "e14_cw", "gu10_cw", "g95_cw")
PATH_RE = re.compile(r"^/ninlight_(" + "|".join(TARGETS) + r")_ota\.img$")
TRAILER_SIZE = 512
TRAILER_MAGIC = b"NINL"
VERSION_OFF = 21
VERSION_LEN = 16
RECENT_MAX = 8
CHUNK = 32 * 1024
def now_iso() -> str:
return datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")
def trailer_version(path: Path) -> str:
"""Firmware version from the image trailer, or '?' if the file carries none."""
try:
with path.open("rb") as f:
if path.stat().st_size < TRAILER_SIZE:
return "?"
f.seek(-TRAILER_SIZE, os.SEEK_END)
tail = f.read(TRAILER_SIZE)
except OSError:
return "?"
if tail[0:4] != TRAILER_MAGIC:
return "?"
return tail[VERSION_OFF:VERSION_OFF + VERSION_LEN].rstrip(b"\x00").decode("ascii", "replace")
class Station:
def __init__(self, image_dir: Path, state_path: Path, stall_after: int | None) -> None:
self.image_dir = image_dir
self.state_path = state_path
self.stall_after = stall_after
self.since = now_iso()
self.served = 0
self.recent: list[dict] = []
self.write_state()
def image_path(self, target: str) -> Path:
return self.image_dir / f"ninlight_{target}_ota.img"
def record(self, ip: str, target: str, version: str, nbytes: int, status: str) -> None:
if status == "ok":
self.served += 1
self.recent.append({"ts": now_iso(), "ip": ip, "target": target,
"version": version, "bytes": nbytes, "status": status})
del self.recent[:-RECENT_MAX]
self.write_state()
def write_state(self) -> None:
payload = {"since": self.since, "served": self.served, "recent": self.recent}
try:
self.state_path.parent.mkdir(parents=True, exist_ok=True)
fd, tmp = tempfile.mkstemp(dir=self.state_path.parent, prefix=".status-")
with os.fdopen(fd, "w") as f:
json.dump(payload, f, indent=2)
os.replace(tmp, self.state_path)
except OSError as e:
print(f"warning: cannot write {self.state_path}: {e}", flush=True)
class Handler(BaseHTTPRequestHandler):
protocol_version = "HTTP/1.1"
server_version = "ninlight-station"
@property
def station(self) -> Station:
return self.server.station # type: ignore[attr-defined]
def log_message(self, fmt: str, *args) -> None: # noqa: D102 - quieter default log
pass
def log(self, status: int, nbytes: int, started: float) -> None:
print(f"{now_iso()} {self.client_address[0]} {self.path} {status} "
f"{nbytes}B {time.monotonic() - started:.1f}s", flush=True)
def do_POST(self) -> None:
self.reject(405, "method not allowed")
do_PUT = do_DELETE = do_HEAD = do_POST
def reject(self, status: int, text: str) -> None:
body = (text + "\n").encode()
self.send_response(status)
self.send_header("Content-Type", "text/plain")
self.send_header("Content-Length", str(len(body)))
self.send_header("Connection", "close")
self.end_headers()
self.wfile.write(body)
def do_GET(self) -> None:
started = time.monotonic()
m = PATH_RE.match(self.path)
if not m:
self.reject(404, "not found")
self.log(404, 0, started)
return
target = m.group(1)
path = self.station.image_path(target)
if not path.is_file():
# Record before responding: a client that sees the 404 complete may check
# status.json right away, so the entry must already be on disk by then.
self.station.record(self.client_address[0], target, "?", 0, "notfound")
self.reject(404, "no image for this device")
self.log(404, 0, started)
return
size = path.stat().st_size
start = 0
rng = self.headers.get("Range", "")
if rng.startswith("bytes="):
first = rng.split("=", 1)[1].split("-", 1)[0]
if first.isdigit() and int(first) < size:
start = int(first)
version = trailer_version(path)
self.send_response(206 if start else 200)
self.send_header("Content-Type", "application/octet-stream")
self.send_header("Content-Length", str(size - start))
if start:
self.send_header("Content-Range", f"bytes {start}-{size - 1}/{size}")
self.send_header("Accept-Ranges", "bytes")
self.send_header("Connection", "close")
self.end_headers()
sent = 0
status = "ok"
recorded = False
remaining = size - start
try:
with path.open("rb") as f:
f.seek(start)
while sent < remaining:
if self.station.stall_after is not None and sent >= self.station.stall_after:
# test aid: hold the connection open and send nothing more, so the
# firmware's stall handling can be exercised on real hardware. We
# still notice if the peer gives up and closes its side, so a test
# (or an impatient client) that hangs up is recorded as "aborted"
# instead of leaking the thread forever.
while True:
readable, _, _ = select.select([self.connection], [], [], 1.0)
if readable:
try:
peek = self.connection.recv(1, socket.MSG_PEEK)
except OSError:
peek = b""
if not peek:
raise ConnectionResetError("peer closed during stall")
read_size = CHUNK
if self.station.stall_after is not None:
# Don't overshoot the stall boundary within a single read: without
# this a whole CHUNK could be sent before the check above ever
# notices we've passed --stall-after.
read_size = min(read_size, max(1, self.station.stall_after - sent))
chunk = f.read(read_size)
if not chunk:
break
if sent + len(chunk) >= remaining:
# Record success before the last bytes go out: the lamp (and our
# tests) may observe the response completing and immediately check
# status.json, so the state must already be on disk by then.
self.station.record(self.client_address[0], target, version,
sent + len(chunk), "ok")
recorded = True
self.wfile.write(chunk)
sent += len(chunk)
except (BrokenPipeError, ConnectionResetError, TimeoutError):
status = "aborted"
self.log(206 if start else 200, sent, started)
if not recorded:
self.station.record(self.client_address[0], target, version, sent, status)
def main(argv: list[str] | None = None) -> int:
p = argparse.ArgumentParser(description="ninlight recovery station HTTP server")
p.add_argument("--image-dir", required=True, type=Path)
p.add_argument("--bind", default="192.168.8.1")
p.add_argument("--port", type=int, default=80)
p.add_argument("--state", type=Path, default=Path("/run/ninlight-station/status.json"))
p.add_argument("--stall-after", type=int, default=None,
help="test aid: stop sending after N bytes but keep the connection open")
a = p.parse_args(argv)
if not a.image_dir.is_dir():
print(f"error: image directory {a.image_dir} does not exist", file=sys.stderr)
return 2
station = Station(a.image_dir, a.state, a.stall_after)
httpd = ThreadingHTTPServer((a.bind, a.port), Handler)
httpd.daemon_threads = True
httpd.station = station # type: ignore[attr-defined]
images = sorted(p.name for p in a.image_dir.glob("ninlight_*_ota.img"))
print(f"{now_iso()} listening on {a.bind}:{a.port}, {len(images)} image(s): "
f"{', '.join(images) or 'none'}", flush=True)
if a.stall_after is not None:
print(f"{now_iso()} WARNING: --stall-after {a.stall_after} is a test aid", flush=True)
try:
httpd.serve_forever()
except KeyboardInterrupt:
pass
return 0
if __name__ == "__main__":
raise SystemExit(main())