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.
Embed the IEEE OUI registry (~1MB pre-processed text file) and resolve
the vendor for every station MAC. Locally administered MACs (U/L bit
set, used by iOS/Android private addresses and virtual interfaces) are
skipped so we don't return spurious matches against randomized prefixes.
The vendor name shows up in the device card as a secondary line, and
falls back to the title position when no DHCP hostname is available —
"Apple" with the IP and MAC is far more useful than "Sans nom".
The lookup table loads lazily (sync.Once) on the first call so the
~40k-entry parse only runs when the station discovery code is exercised.
