Pull request: * all: move internal Go packages to internal/

Merge in DNS/adguard-home from 2234-move-to-internal to master

Squashed commit of the following:

commit d26a288cabeac86f9483fab307677b1027c78524
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Fri Oct 30 12:44:18 2020 +0300

    * all: move internal Go packages to internal/

    Closes #2234.

internal/dhcpd/db.go

@@ -0,0 +1,173 @@
+// On-disk database for lease table
+
+package dhcpd
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"net"
+	"os"
+	"time"
+
+	"github.com/AdguardTeam/golibs/file"
+	"github.com/AdguardTeam/golibs/log"
+)
+
+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() {
+	dynLeases := []*Lease{}
+	staticLeases := []*Lease{}
+	v6StaticLeases := []*Lease{}
+	v6DynLeases := []*Lease{}
+
+	data, err := ioutil.ReadFile(s.conf.DBFilePath)
+	if err != nil {
+		if !os.IsNotExist(err) {
+			log.Error("DHCP: can't read file %s: %v", s.conf.DBFilePath, err)
+		}
+		return
+	}
+
+	obj := []leaseJSON{}
+	err = json.Unmarshal(data, &obj)
+	if err != nil {
+		log.Error("DHCP: invalid DB: %v", err)
+		return
+	}
+
+	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)
+	s.srv4.ResetLeases(leases4)
+
+	leases6 := normalizeLeases(v6StaticLeases, v6DynLeases)
+	if s.srv6 != nil {
+		s.srv6.ResetLeases(leases6)
+	}
+
+	log.Info("DHCP: loaded leases v4:%d  v6:%d  total-read:%d from DB",
+		len(leases4), len(leases6), numLeases)
+}
+
+// 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() {
+	var 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)
+		}
+	}
+
+	data, err := json.Marshal(leases)
+	if err != nil {
+		log.Error("json.Marshal: %v", err)
+		return
+	}
+
+	err = file.SafeWrite(s.conf.DBFilePath, data)
+	if err != nil {
+		log.Error("DHCP: can't store lease table on disk: %v  filename: %s",
+			err, s.conf.DBFilePath)
+		return
+	}
+	log.Info("DHCP: stored %d leases in DB", len(leases))
+}