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// SPDX-License-Identifier: GPL-3.0-or-later
package isc_dhcpd
import (
"bufio"
"bytes"
"net"
"os"
)
/*
Documentation (v4.4): https://kb.isc.org/docs/en/isc-dhcp-44-manual-pages-dhcpdleases
DHCPv4 prepare declaration:
prepare ip-address {
statements...
}
DHCPv6 prepare declaration:
ia_ta IAID_DUID {
cltt date;
iaaddr ipv6-address {
statements...
}
}
ia_na IAID_DUID {
cltt date;
iaaddr ipv6-address {
statements...
}
}
ia_pd IAID_DUID {
cltt date;
iaprefix ipv6-address/prefix-length {
statements...
}
}
*/
type leaseEntry struct {
ip net.IP
bindingState string
}
func (l leaseEntry) hasIP() bool { return l.ip != nil }
func (l leaseEntry) hasBindingState() bool { return l.bindingState != "" }
func parseDHCPdLeasesFile(filepath string) ([]leaseEntry, error) {
f, err := os.Open(filepath)
if err != nil {
return nil, err
}
defer func() { _ = f.Close() }()
leasesSet := make(map[string]leaseEntry)
l := leaseEntry{}
sc := bufio.NewScanner(f)
for sc.Scan() {
bs := bytes.TrimSpace(sc.Bytes())
switch {
case !l.hasIP() && bytes.HasPrefix(bs, []byte("lease")):
// "lease 192.168.0.1 {" => "192.168.0.1"
s := string(bs)
l.ip = net.ParseIP(s[6 : len(s)-2])
case !l.hasIP() && bytes.HasPrefix(bs, []byte("iaaddr")):
// "iaaddr 1985:470:1f0b:c9a::001 {" => "1985:470:1f0b:c9a::001"
s := string(bs)
l.ip = net.ParseIP(s[7 : len(s)-2])
case l.hasIP() && !l.hasBindingState() && bytes.HasPrefix(bs, []byte("binding state")):
// "binding state active;" => "active"
s := string(bs)
l.bindingState = s[14 : len(s)-1]
case bytes.HasPrefix(bs, []byte("}")):
if l.hasIP() && l.hasBindingState() {
leasesSet[l.ip.String()] = l
}
l = leaseEntry{}
}
}
if len(leasesSet) == 0 {
return nil, nil
}
leases := make([]leaseEntry, 0, len(leasesSet))
for _, l := range leasesSet {
leases = append(leases, l)
}
return leases, nil
}
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