AdGuardHome/internal/dhcpd/db.go

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// On-disk database for lease table
package dhcpd
import (
"encoding/json"
"fmt"
"net"
"os"
"time"
"github.com/AdguardTeam/golibs/errors"
"github.com/AdguardTeam/golibs/log"
"github.com/google/renameio/maybe"
)
const dbFilename = "leases.db"
type leaseJSON struct {
HWAddr []byte `json:"mac"`
IP []byte `json:"ip"`
Hostname string `json:"host"`
Expiry int64 `json:"exp"`
}
func normalizeIP(ip net.IP) net.IP {
ip4 := ip.To4()
if ip4 != nil {
return ip4
}
return ip
}
// Load lease table from DB
func (s *Server) dbLoad() (err error) {
dynLeases := []*Lease{}
staticLeases := []*Lease{}
v6StaticLeases := []*Lease{}
v6DynLeases := []*Lease{}
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data, err := os.ReadFile(s.conf.DBFilePath)
if err != nil {
if !errors.Is(err, os.ErrNotExist) {
return fmt.Errorf("reading db: %w", err)
}
return nil
}
obj := []leaseJSON{}
err = json.Unmarshal(data, &obj)
if err != nil {
return fmt.Errorf("decoding db: %w", err)
}
numLeases := len(obj)
for i := range obj {
obj[i].IP = normalizeIP(obj[i].IP)
if !(len(obj[i].IP) == 4 || len(obj[i].IP) == 16) {
log.Info("dhcp: invalid IP: %s", obj[i].IP)
continue
}
lease := Lease{
HWAddr: obj[i].HWAddr,
IP: obj[i].IP,
Hostname: obj[i].Hostname,
Expiry: time.Unix(obj[i].Expiry, 0),
}
if len(obj[i].IP) == 16 {
if obj[i].Expiry == leaseExpireStatic {
v6StaticLeases = append(v6StaticLeases, &lease)
} else {
v6DynLeases = append(v6DynLeases, &lease)
}
} else {
if obj[i].Expiry == leaseExpireStatic {
staticLeases = append(staticLeases, &lease)
} else {
dynLeases = append(dynLeases, &lease)
}
}
}
leases4 := normalizeLeases(staticLeases, dynLeases)
err = s.srv4.ResetLeases(leases4)
if err != nil {
return fmt.Errorf("resetting dhcpv4 leases: %w", err)
}
leases6 := normalizeLeases(v6StaticLeases, v6DynLeases)
if s.srv6 != nil {
err = s.srv6.ResetLeases(leases6)
if err != nil {
return fmt.Errorf("resetting dhcpv6 leases: %w", err)
}
}
log.Info("dhcp: loaded leases v4:%d v6:%d total-read:%d from DB",
len(leases4), len(leases6), numLeases)
return nil
}
// Skip duplicate leases
// Static leases have a priority over dynamic leases
func normalizeLeases(staticLeases, dynLeases []*Lease) []*Lease {
leases := []*Lease{}
index := map[string]int{}
for i, lease := range staticLeases {
_, ok := index[lease.HWAddr.String()]
if ok {
continue // skip the lease with the same HW address
}
index[lease.HWAddr.String()] = i
leases = append(leases, lease)
}
for i, lease := range dynLeases {
_, ok := index[lease.HWAddr.String()]
if ok {
continue // skip the lease with the same HW address
}
index[lease.HWAddr.String()] = i
leases = append(leases, lease)
}
return leases
}
// Store lease table in DB
func (s *Server) dbStore() (err error) {
// Use an empty slice here as opposed to nil so that it doesn't write
// "null" into the database file if leases are empty.
leases := []leaseJSON{}
leases4 := s.srv4.getLeasesRef()
for _, l := range leases4 {
if l.Expiry.Unix() == 0 {
continue
}
lease := leaseJSON{
HWAddr: l.HWAddr,
IP: l.IP,
Hostname: l.Hostname,
Expiry: l.Expiry.Unix(),
}
leases = append(leases, lease)
}
if s.srv6 != nil {
leases6 := s.srv6.getLeasesRef()
for _, l := range leases6 {
if l.Expiry.Unix() == 0 {
continue
}
lease := leaseJSON{
HWAddr: l.HWAddr,
IP: l.IP,
Hostname: l.Hostname,
Expiry: l.Expiry.Unix(),
}
leases = append(leases, lease)
}
}
var data []byte
data, err = json.Marshal(leases)
if err != nil {
return fmt.Errorf("encoding db: %w", err)
}
err = maybe.WriteFile(s.conf.DBFilePath, data, 0o644)
if err != nil {
return fmt.Errorf("writing db: %w", err)
}
log.Info("dhcp: stored %d leases in db", len(leases))
return nil
}