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dhcp4d: don’t incorrectly hand out reused addresses

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fixes #18
This commit is contained in:
Michael Stapelberg 2018-12-15 12:44:09 +01:00
parent badee1eef8
commit a5d9e03dd3
2 changed files with 73 additions and 23 deletions
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25
internal/dhcp4d/dhcp4d.go
View File

@ -49,7 +49,7 @@ type Handler struct {
leaseRange int // number of IP addresses to hand out
leasePeriod time.Duration
options dhcp4.Options
leasesHW map[string]*Lease
leasesHW map[string]int // points into leasesIP
leasesIP map[int]*Lease
rawConn net.PacketConn
iface *net.Interface
@ -84,7 +84,7 @@ func NewHandler(dir string, iface *net.Interface, conn net.PacketConn) (*Handler
return &Handler{
rawConn: conn,
iface: iface,
leasesHW: make(map[string]*Lease),
leasesHW: make(map[string]int),
leasesIP: make(map[int]*Lease),
serverIP: serverIP,
start: start,
@ -105,10 +105,10 @@ func NewHandler(dir string, iface *net.Interface, conn net.PacketConn) (*Handler
// loaded from persistent storage. There is no locking, so SetLeases must be
// called before Serve.
func (h *Handler) SetLeases(leases []*Lease) {
h.leasesHW = make(map[string]*Lease)
h.leasesHW = make(map[string]int)
h.leasesIP = make(map[int]*Lease)
for _, l := range leases {
h.leasesHW[l.HardwareAddr] = l
h.leasesHW[l.HardwareAddr] = l.Num
h.leasesIP[l.Num] = l
}
}
@ -204,6 +204,15 @@ func (h *Handler) ServeDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options d
return nil
}
func (h *Handler) leaseHW(hwAddr string) (*Lease, bool) {
num, ok := h.leasesHW[hwAddr]
if !ok {
return nil, false
}
l, ok := h.leasesIP[num]
return l, ok
}
// TODO: is ServeDHCP always run from the same goroutine, or do we need locking?
func (h *Handler) serveDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options dhcp4.Options) dhcp4.Packet {
reqIP := net.IP(options[dhcp4.OptionRequestedIPAddress])
@ -223,7 +232,7 @@ func (h *Handler) serveDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options d
}
// offer previous lease for this HardwareAddr, if any
if lease, ok := h.leasesHW[hwAddr]; ok && !lease.Expired(h.timeNow()) {
if lease, ok := h.leaseHW(hwAddr); ok && !lease.Expired(h.timeNow()) {
free = lease.Num
//log.Printf("h.leasesHW[%s] = %d", hwAddr, free)
}
@ -258,12 +267,12 @@ func (h *Handler) serveDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options d
Num: leaseNum,
Addr: make([]byte, 4),
HardwareAddr: p.CHAddr().String(),
Expiry: time.Now().Add(h.leasePeriod),
Expiry: h.timeNow().Add(h.leasePeriod),
Hostname: string(options[dhcp4.OptionHostName]),
}
copy(lease.Addr, reqIP.To4())
if l, ok := h.leasesHW[lease.HardwareAddr]; ok {
if l, ok := h.leaseHW(lease.HardwareAddr); ok {
if l.Expiry.IsZero() {
// Retain permanent lease properties
lease.Expiry = time.Time{}
@ -275,7 +284,7 @@ func (h *Handler) serveDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options d
}
h.leasesIP[leaseNum] = lease
h.leasesHW[lease.HardwareAddr] = lease
h.leasesHW[lease.HardwareAddr] = leaseNum
if h.Leases != nil {
var leases []*Lease
for _, l := range h.leasesIP {

57
internal/dhcp4d/dhcp4d_test.go
View File

@ -26,6 +26,11 @@ import (
"github.com/krolaw/dhcp4"
)
func messageType(p dhcp4.Packet) dhcp4.MessageType {
opts := p.ParseOptions()
return dhcp4.MessageType(opts[dhcp4.OptionDHCPMessageType][0])
}
func packet(mt dhcp4.MessageType, addr net.IP, hwaddr net.HardwareAddr, opts []dhcp4.Option) dhcp4.Packet {
return dhcp4.RequestPacket(
mt,
@ -201,8 +206,7 @@ func TestPoolBoundaries(t *testing.T) {
addr[len(addr)-1] = last
p := request(addr, hardwareAddr)
resp := handler.serveDHCP(p, dhcp4.Request, p.ParseOptions())
opts := resp.ParseOptions()
if got, want := dhcp4.MessageType(opts[dhcp4.OptionDHCPMessageType][0]), dhcp4.NAK; got != want {
if got, want := messageType(resp), dhcp4.NAK; got != want {
t.Errorf("DHCPREQUEST resulted in unexpected message type: got %v, want %v", got, want)
}
}
@ -228,8 +232,7 @@ func TestPreviousLease(t *testing.T) {
p = request(addr1, hardwareAddr2)
resp = handler.serveDHCP(p, dhcp4.Request, p.ParseOptions())
opts := resp.ParseOptions()
if got, want := dhcp4.MessageType(opts[dhcp4.OptionDHCPMessageType][0]), dhcp4.NAK; got != want {
if got, want := messageType(resp), dhcp4.NAK; got != want {
t.Errorf("DHCPREQUEST resulted in unexpected message type: got %v, want %v", got, want)
}
@ -285,8 +288,7 @@ func TestPermanentLease(t *testing.T) {
p = request(addr, hardwareAddr)
resp = handler.serveDHCP(p, dhcp4.Request, p.ParseOptions())
opts := resp.ParseOptions()
if got, want := dhcp4.MessageType(opts[dhcp4.OptionDHCPMessageType][0]), dhcp4.NAK; got != want {
if got, want := messageType(resp), dhcp4.NAK; got != want {
t.Errorf("DHCPREQUEST resulted in unexpected message type: got %v, want %v", got, want)
}
}
@ -335,8 +337,7 @@ func TestExpiration(t *testing.T) {
hardwareAddr[len(hardwareAddr)-1] = addr[len(addr)-1] - 1
p := request(addr, hardwareAddr)
resp := handler.serveDHCP(p, dhcp4.Request, p.ParseOptions())
opts := resp.ParseOptions()
if got, want := dhcp4.MessageType(opts[dhcp4.OptionDHCPMessageType][0]), dhcp4.NAK; got != want {
if got, want := messageType(resp), dhcp4.NAK; got != want {
t.Errorf("DHCPREQUEST resulted in unexpected message type: got %v, want %v", got, want)
}
}
@ -364,6 +365,46 @@ func TestExpiration(t *testing.T) {
})
}
func TestRequestExpired(t *testing.T) {
handler, cleanup := testHandler(t)
defer cleanup()
now := time.Now()
handler.timeNow = func() time.Time { return now }
addr := net.IP{192, 168, 42, 23}
hardwareAddr := map[string]net.HardwareAddr{
"xps": net.HardwareAddr{0x11, 0x22, 0x33, 0x44, 0x55, 0x66},
"mbp": net.HardwareAddr{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff},
}
t.Run("mbp grabs an address", func(t *testing.T) {
p := request(addr, hardwareAddr["mbp"])
resp := handler.serveDHCP(p, dhcp4.Request, p.ParseOptions())
if got, want := messageType(resp), dhcp4.ACK; got != want {
t.Errorf("DHCPREQUEST resulted in unexpected message type: got %v, want %v", got, want)
}
})
now = now.Add(3 * time.Hour)
t.Run("xps grabs the same address", func(t *testing.T) {
p := request(addr, hardwareAddr["xps"])
resp := handler.serveDHCP(p, dhcp4.Request, p.ParseOptions())
if got, want := messageType(resp), dhcp4.ACK; got != want {
t.Errorf("DHCPREQUEST resulted in unexpected message type: got %v, want %v", got, want)
}
})
t.Run("mbp requests its old address", func(t *testing.T) {
p := request(addr, hardwareAddr["mbp"])
resp := handler.serveDHCP(p, dhcp4.Request, p.ParseOptions())
if got, want := messageType(resp), dhcp4.NAK; got != want {
t.Errorf("DHCPREQUEST resulted in unexpected message type: got %v, want %v", got, want)
}
})
}
func TestServerID(t *testing.T) {
handler, cleanup := testHandler(t)
defer cleanup()