The hostapd backend never populated IPs: NewDHCPCorrelator was defined
but never instantiated, and even when it was, the parser only handled
ISC dhcpd's text format. On a BusyBox-based router using udhcpd, every
device showed up with an empty IP.
Two fixes:
- Add a udhcpd binary lease parser. The format is documented in
busybox/networking/udhcp/dhcpd.{h,c}: an 8-byte big-endian unix-time
header followed by 36-byte dyn_lease records (expires, IP, MAC,
20-byte hostname, 2-byte pad). ParseLeases auto-detects the format
by inspecting the header so the same code path handles both udhcpd
and ISC text leases.
- Wire the DHCPCorrelator into Backend.Initialize and have it merge
two sources: ARP first (universal IP fallback for any station that
has been talked to) and DHCP leases on top (authoritative, carries
the hostname). ARP fills the gap when leases are missing or the
station uses a static IP; DHCP wins on conflict.
Default DHCPLeasesPath updated to /var/lib/udhcpd/udhcpd.leases — the
common BusyBox path. Configurable as before.
Bind to localhost by default and stop echoing backend errors (which can
embed credentials or low-level details) back over the API and log
broadcast. Validate hotspot SSID/passphrase/channel before writing
hostapd.conf and tighten its mode to 0600 since it stores the WPA PSK.
Restrict WebSocket upgrades to same-origin so a LAN browser can't be
turned into a proxy for the API.
Guard shared state: status reads/writes go through StatusMutex (the
periodic updater races with the toggle and status handlers otherwise),
broadcastToWebSockets no longer mutates the client map under RLock, and
station-event callbacks now run under SafeGo so a panic in app code can't
take down the daemon. Stop channels in hostapd, dhcp, and iwd signal
monitors are now closed under sync.Once to survive concurrent Stop calls.
App.Shutdown is idempotent and waits for the periodic loops before
closing backends, so signal-driven and deferred shutdowns no longer race.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
