Pierre-Olivier Mercier
5a3942f351
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.
75 lines
2.4 KiB
Go
75 lines
2.4 KiB
Go
package dhcp
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import (
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"encoding/binary"
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"testing"
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)
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func TestParseUdhcpdLeases(t *testing.T) {
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// Build a synthetic udhcpd lease file: 8-byte big-endian timestamp
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// header, then two 36-byte records.
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buf := make([]byte, 0, 8+36*3)
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header := make([]byte, 8)
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binary.BigEndian.PutUint64(header, 1714560000) // 2024-05-01
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buf = append(buf, header...)
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// Record 1: 192.168.1.42, aa:bb:cc:dd:ee:ff, "iPhone"
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r1 := make([]byte, 36)
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binary.BigEndian.PutUint32(r1[0:4], 3600) // expires
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r1[4], r1[5], r1[6], r1[7] = 192, 168, 1, 42 // IP
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r1[8], r1[9], r1[10] = 0xaa, 0xbb, 0xcc // MAC
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r1[11], r1[12], r1[13] = 0xdd, 0xee, 0xff //
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copy(r1[14:34], "iPhone\x00") // hostname (NUL-padded)
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buf = append(buf, r1...)
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// Record 2: empty slot (all zero MAC/IP) — should be skipped
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r2 := make([]byte, 36)
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buf = append(buf, r2...)
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// Record 3: 10.0.0.1, b8:27:eb:11:22:33, no hostname
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r3 := make([]byte, 36)
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binary.BigEndian.PutUint32(r3[0:4], 7200)
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r3[4], r3[5], r3[6], r3[7] = 10, 0, 0, 1
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r3[8], r3[9], r3[10] = 0xb8, 0x27, 0xeb
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r3[11], r3[12], r3[13] = 0x11, 0x22, 0x33
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buf = append(buf, r3...)
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if !looksLikeUdhcpd(buf) {
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t.Fatalf("synthetic file not detected as udhcpd")
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}
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leases, err := parseUdhcpdLeases(buf)
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if err != nil {
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t.Fatalf("parseUdhcpdLeases: %v", err)
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}
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if len(leases) != 2 {
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t.Fatalf("expected 2 leases, got %d: %+v", len(leases), leases)
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}
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if leases[0].IP != "192.168.1.42" {
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t.Errorf("lease[0].IP = %q, want %q", leases[0].IP, "192.168.1.42")
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}
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if leases[0].MAC != "aa:bb:cc:dd:ee:ff" {
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t.Errorf("lease[0].MAC = %q, want %q", leases[0].MAC, "aa:bb:cc:dd:ee:ff")
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}
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if leases[0].Hostname != "iPhone" {
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t.Errorf("lease[0].Hostname = %q, want %q", leases[0].Hostname, "iPhone")
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}
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if leases[1].IP != "10.0.0.1" {
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t.Errorf("lease[1].IP = %q, want %q", leases[1].IP, "10.0.0.1")
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}
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if leases[1].MAC != "b8:27:eb:11:22:33" {
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t.Errorf("lease[1].MAC = %q, want %q", leases[1].MAC, "b8:27:eb:11:22:33")
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}
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if leases[1].Hostname != "" {
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t.Errorf("lease[1].Hostname = %q, want empty", leases[1].Hostname)
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}
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}
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func TestLooksLikeUdhcpdRejectsText(t *testing.T) {
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text := []byte("# The format of this file is documented in dhcpd.leases(5).\nlease 192.168.1.42 {\n starts 0 2024/05/01 00:00:00;\n hardware ethernet aa:bb:cc:dd:ee:ff;\n client-hostname \"iPhone\";\n}\n")
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if looksLikeUdhcpd(text) {
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t.Errorf("ISC text file misdetected as udhcpd")
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}
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}
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