dnsd: don’t serve expired leases

fixes #6

internal/dns/dns.go

@@ -129,7 +129,11 @@ func (s *Server) SetLeases(leases []dhcp4d.Lease) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	s.initHostsLocked()
+	now := time.Now()
 	for _, l := range leases {
+		if l.Expired(now) {
+			continue
+		}
 		s.hostsByName[l.Hostname] = l.Addr.String()
 		if rev, err := dns.ReverseAddr(l.Addr.String()); err == nil {
 			s.hostsByIP[rev] = l.Hostname

internal/dns/dns_test.go

@@ -19,6 +19,7 @@ import (
 	"net"
 	"os"
 	"testing"
+	"time"
 
 	"github.com/rtr7/router7/internal/dhcp4d"
 
@@ -76,7 +77,7 @@ func TestDHCP(t *testing.T) {
 		},
 	})
 
-	t.Run("xps.lan.", func(t *testing.T) {
+	resolveXps := func(t *testing.T) {
 		m := new(dns.Msg)
 		m.SetQuestion("xps.lan.", dns.TypeA)
 		s.Mux.ServeDNS(r, m)
@@ -90,8 +91,25 @@ func TestDHCP(t *testing.T) {
 		if got, want := a.(*dns.A).A, net.ParseIP("192.168.42.23"); !got.Equal(want) {
 			t.Fatalf("unexpected response IP: got %v, want %v", got, want)
 		}
+	}
+	t.Run("xps.lan.", resolveXps)
+
+	expired := time.Now().Add(-1 * time.Second)
+	s.SetLeases([]dhcp4d.Lease{
+		{
+			Hostname: "xps",
+			Addr:     net.IP{192, 168, 42, 23},
+			Expiry:   time.Now().Add(1 * time.Minute),
+		},
+		{
+			Hostname: "xps",
+			Addr:     net.IP{192, 168, 42, 150},
+			Expiry:   expired,
+		},
 	})
 
+	t.Run("xps.lan. (expired)", resolveXps)
+
 	t.Run("notfound.lan.", func(t *testing.T) {
 		m := new(dns.Msg)
 		m.SetQuestion("notfound.lan.", dns.TypeA)