- DHCP: normalize leases on startup (prioritize static leases over dynamic)

dhcpd/db.go

@@ -36,6 +36,8 @@ func ipInRange(start, stop, ip net.IP) bool {
 func (s *Server) dbLoad() {
 	s.leases = nil
 	s.IPpool = make(map[[4]byte]net.HardwareAddr)
+	dynLeases := []*Lease{}
+	staticLeases := []*Lease{}
 
 	data, err := ioutil.ReadFile(s.conf.DBFilePath)
 	if err != nil {
@@ -69,11 +71,47 @@ func (s *Server) dbLoad() {
 			Expiry:   time.Unix(obj[i].Expiry, 0),
 		}
 
-		s.leases = append(s.leases, &lease)
+		if obj[i].Expiry == leaseExpireStatic {
+			staticLeases = append(staticLeases, &lease)
+		} else {
+			dynLeases = append(dynLeases, &lease)
+		}
+	}
 
+	s.leases = normalizeLeases(staticLeases, dynLeases)
+
+	for _, lease := range s.leases {
 		s.reserveIP(lease.IP, lease.HWAddr)
 	}
-	log.Info("DHCP: loaded %d leases from DB", numLeases)
+
+	log.Info("DHCP: loaded %d (%d) leases from DB", len(s.leases), 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

dhcpd/dhcpd_test.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/krolaw/dhcp4"
+	"github.com/stretchr/testify/assert"
 )
 
 func check(t *testing.T, result bool, msg string) {
@@ -211,3 +212,32 @@ func TestIsValidSubnetMask(t *testing.T) {
 		t.Fatalf("isValidSubnetMask([]byte{255,255,253,0})")
 	}
 }
+
+func TestNormalizeLeases(t *testing.T) {
+	dynLeases := []*Lease{}
+	staticLeases := []*Lease{}
+	leases := []*Lease{}
+
+	lease := &Lease{}
+	lease.HWAddr = []byte{1, 2, 3, 4}
+	dynLeases = append(dynLeases, lease)
+	lease = new(Lease)
+	lease.HWAddr = []byte{1, 2, 3, 5}
+	dynLeases = append(dynLeases, lease)
+
+	lease = new(Lease)
+	lease.HWAddr = []byte{1, 2, 3, 4}
+	lease.IP = []byte{0, 2, 3, 4}
+	staticLeases = append(staticLeases, lease)
+	lease = new(Lease)
+	lease.HWAddr = []byte{2, 2, 3, 4}
+	staticLeases = append(staticLeases, lease)
+
+	leases = normalizeLeases(staticLeases, dynLeases)
+
+	assert.True(t, len(leases) == 3)
+	assert.True(t, bytes.Equal(leases[0].HWAddr, []byte{1, 2, 3, 4}))
+	assert.True(t, bytes.Equal(leases[0].IP, []byte{0, 2, 3, 4}))
+	assert.True(t, bytes.Equal(leases[1].HWAddr, []byte{2, 2, 3, 4}))
+	assert.True(t, bytes.Equal(leases[2].HWAddr, []byte{1, 2, 3, 5}))
+}