| 1 | // SPDX-License-Identifier: GPL-3.0-or-later |
| 2 | |
| 3 | //go:build linux || freebsd || openbsd || netbsd || dragonfly |
| 4 | |
| 5 | package isc_dhcpd |
| 6 | |
| 7 | import ( |
| 8 | "bufio" |
| 9 | "bytes" |
| 10 | "net/netip" |
| 11 | "os" |
| 12 | ) |
| 13 | |
| 14 | /* |
| 15 | Documentation (v4.4): https://kb.isc.org/docs/en/isc-dhcp-44-manual-pages-dhcpdleases |
| 16 | |
| 17 | DHCPv4 prepare declaration: |
| 18 | prepare ip-address { |
| 19 | statements... |
| 20 | } |
| 21 | |
| 22 | DHCPv6 prepare declaration: |
| 23 | ia_ta IAID_DUID { |
| 24 | cltt date; |
| 25 | iaaddr ipv6-address { |
| 26 | statements... |
| 27 | } |
| 28 | } |
| 29 | ia_na IAID_DUID { |
| 30 | cltt date; |
| 31 | iaaddr ipv6-address { |
| 32 | statements... |
| 33 | } |
| 34 | } |
| 35 | ia_pd IAID_DUID { |
| 36 | cltt date; |
| 37 | iaprefix ipv6-address/prefix-length { |
| 38 | statements... |
| 39 | } |
| 40 | } |
| 41 | */ |
| 42 | |
| 43 | type leaseEntry struct { |
| 44 | addr netip.Addr |
| 45 | bindingState string |
| 46 | } |
| 47 | |
| 48 | func (l leaseEntry) isAddrValid() bool { return l.addr.IsValid() } |
| 49 | func (l leaseEntry) hasBindingState() bool { return l.bindingState != "" } |
| 50 | |
| 51 | func parseDHCPdLeasesFile(filepath string) ([]leaseEntry, error) { |
| 52 | f, err := os.Open(filepath) |
| 53 | if err != nil { |
| 54 | return nil, err |
| 55 | } |
| 56 | defer func() { _ = f.Close() }() |
| 57 | |
| 58 | leasesSet := make(map[string]leaseEntry) |
| 59 | l := leaseEntry{} |
| 60 | sc := bufio.NewScanner(f) |
| 61 | |
| 62 | for sc.Scan() { |
| 63 | bs := bytes.TrimSpace(sc.Bytes()) |
| 64 | switch { |
| 65 | case !l.isAddrValid() && bytes.HasPrefix(bs, []byte("lease")): |
| 66 | // "lease 192.168.0.1 {" => "192.168.0.1" |
| 67 | s := string(bs) |
| 68 | if addr, err := netip.ParseAddr(s[6 : len(s)-2]); err == nil && addr.IsValid() { |
| 69 | l.addr = addr |
| 70 | } |
| 71 | case !l.isAddrValid() && bytes.HasPrefix(bs, []byte("iaaddr")): |
| 72 | // "iaaddr 1985:470:1f0b:c9a::001 {" => "1985:470:1f0b:c9a::001" |
| 73 | s := string(bs) |
| 74 | if addr, err := netip.ParseAddr(s[7 : len(s)-2]); err == nil && addr.IsValid() { |
| 75 | l.addr = addr |
| 76 | } |
| 77 | case l.isAddrValid() && !l.hasBindingState() && bytes.HasPrefix(bs, []byte("binding state")): |
| 78 | // "binding state active;" => "active" |
| 79 | s := string(bs) |
| 80 | l.bindingState = s[14 : len(s)-1] |
| 81 | case bytes.HasPrefix(bs, []byte("}")): |
| 82 | if l.isAddrValid() && l.hasBindingState() { |
| 83 | leasesSet[l.addr.String()] = l |
| 84 | } |
| 85 | l = leaseEntry{} |
| 86 | } |
| 87 | } |
| 88 | |
| 89 | if len(leasesSet) == 0 { |
| 90 | return nil, nil |
| 91 | } |
| 92 | |
| 93 | leases := make([]leaseEntry, 0, len(leasesSet)) |
| 94 | for _, l := range leasesSet { |
| 95 | leases = append(leases, l) |
| 96 | } |
| 97 | return leases, nil |
| 98 | } |