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tstest/natlab/vnet: add DHCP tests, ignore DHCPv4 on v6-only networks

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And clean up some of the test helpers in the process.

Updates #13038

Change-Id: I3e2b5f7028a32d97af7f91941e59399a8e222b25
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2024-08-29 07:02:49 -07:00 committed by Brad Fitzpatrick
parent ffa1c93f59
commit b1a5b40318
2 changed files with 110 additions and 23 deletions
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5
tstest/natlab/vnet/vnet.go
View File

@ -1286,6 +1286,10 @@ func (n *network) handleUDPPacketForRouter(ep EthernetPacket, udp *layers.UDP, t
srcIP, dstIP := flow.src, flow.dst
if isDHCPRequest(packet) {
if !n.v4 {
n.logf("dropping DHCPv4 packet on v6-only network")
return
}
res, err := n.s.createDHCPResponse(packet)
if err != nil {
n.logf("createDHCPResponse: %v", err)
@ -1587,6 +1591,7 @@ func (s *Server) createDHCPResponse(request gopacket.Packet) ([]byte, error) {
return mkPacketErr(eth, ip, udp, response)
}
// isDHCPRequest reports whether pkt is a DHCPv4 request.
func isDHCPRequest(pkt gopacket.Packet) bool {
v4, ok := pkt.Layer(layers.LayerTypeIPv4).(*layers.IPv4)
if !ok || v4.Protocol != layers.IPProtocolUDP {

128
tstest/natlab/vnet/vnet_test.go
View File

@ -98,7 +98,25 @@ type netTest struct {
logSubstr("dropping IPv6 packet on v4-only network"),
),
},
// TODO(bradfitz): DHCP request + response
{
name: "dhcp-discover",
pkt: mkDHCP(nodeMac(1), layers.DHCPMsgTypeDiscover),
check: all(
numPkts(2), // DHCP discover broadcast to node2 also, and the DHCP reply from router
pktSubstr("SrcMAC=52:cc:cc:cc:cc:01 DstMAC=ff:ff:ff:ff:ff:ff"),
pktSubstr("Options=[Option(ServerID:192.168.0.1), Option(MessageType:Offer)]}"),
),
},
{
name: "dhcp-request",
pkt: mkDHCP(nodeMac(1), layers.DHCPMsgTypeRequest),
check: all(
numPkts(2), // DHCP discover broadcast to node2 also, and the DHCP reply from router
pktSubstr("SrcMAC=52:cc:cc:cc:cc:01 DstMAC=ff:ff:ff:ff:ff:ff"),
pktSubstr("YourClientIP=192.168.0.101"),
pktSubstr("Options=[Option(ServerID:192.168.0.1), Option(MessageType:Ack), Option(LeaseTime:3600), Option(Router:[192 168 0 1]), Option(DNS:[4 11 4 11]), Option(SubnetMask:255.255.255.0)]}"),
),
},
},
},
{
@ -132,6 +150,24 @@ type netTest struct {
pktSubstr("TypeCode=EchoRequest"),
),
},
{
name: "no-dhcp-on-v6-disco",
pkt: mkDHCP(nodeMac(1), layers.DHCPMsgTypeDiscover),
check: all(
numPkts(1), // DHCP discover broadcast to node2 only
logSubstr("dropping DHCPv4 packet on v6-only network"),
pktSubstr("SrcMAC=52:cc:cc:cc:cc:01 DstMAC=ff:ff:ff:ff:ff:ff"),
),
},
{
name: "no-dhcp-on-v6-request",
pkt: mkDHCP(nodeMac(1), layers.DHCPMsgTypeRequest),
check: all(
numPkts(1), // DHCP request broadcast to node2 only
pktSubstr("SrcMAC=52:cc:cc:cc:cc:01 DstMAC=ff:ff:ff:ff:ff:ff"),
logSubstr("dropping DHCPv4 packet on v6-only network"),
),
},
},
},
}
@ -145,20 +181,22 @@ type netTest struct {
for _, tt := range tt.tests {
t.Run(tt.name, func(t *testing.T) {
se := &sideEffects{}
s.SetLoggerForTest(se.logf)
for mac := range s.MACs() {
s.RegisterSinkForTest(mac, func(eth []byte) {
se.got = append(se.got, eth)
})
}
se := newSideEffects(s)
if err := s.handleEthernetFrameFromVM(tt.pkt); err != nil {
t.Fatal(err)
}
if tt.check != nil {
if err := tt.check(se); err != nil {
t.Fatal(err)
t.Error(err)
}
}
if t.Failed() {
t.Logf("logs were:\n%s", strings.Join(se.logs, "\n"))
for i, rp := range se.got {
p := gopacket.NewPacket(rp.eth, layers.LayerTypeEthernet, gopacket.Lazy)
got := p.String()
t.Logf("[pkt%d, port %v]:\n%s\n", i, rp.port, got)
}
}
})
@ -285,11 +323,63 @@ func mkDNSReq(ipVer int) []byte {
return mkPacket(eth, ip, udp, dns)
}
func mkDHCP(srcMAC MAC, typ layers.DHCPMsgType) []byte {
eth := &layers.Ethernet{
SrcMAC: srcMAC.HWAddr(),
DstMAC: macBroadcast.HWAddr(),
EthernetType: layers.EthernetTypeIPv4,
}
ip := &layers.IPv4{
Version: 4,
Protocol: layers.IPProtocolUDP,
SrcIP: net.ParseIP("0.0.0.0"),
DstIP: net.ParseIP("255.255.255.255"),
}
udp := &layers.UDP{
SrcPort: 68,
DstPort: 67,
}
dhcp := &layers.DHCPv4{
Operation: layers.DHCPOpRequest,
HardwareType: layers.LinkTypeEthernet,
HardwareLen: 6,
Xid: 0,
Secs: 0,
Flags: 0,
ClientHWAddr: srcMAC[:],
Options: []layers.DHCPOption{
{Type: layers.DHCPOptMessageType, Length: 1, Data: []byte{byte(typ)}},
},
}
return mkPacket(eth, ip, udp, dhcp)
}
// receivedPacket is an ethernet frame that was received during a test.
type receivedPacket struct {
port MAC // MAC address of client that received the packet
eth []byte // ethernet frame; dst MAC might be ff:ff:ff:ff:ff:ff, etc
}
// sideEffects gathers side effects as a result of sending a packet and tests
// whether those effects were as desired.
type sideEffects struct {
logs []string
got [][]byte // ethernet packets received
got []receivedPacket // ethernet packets received
}
// newSideEffects creates a new sideEffects recorder, registering itself with s.
func newSideEffects(s *Server) *sideEffects {
se := &sideEffects{}
s.SetLoggerForTest(se.logf)
for mac := range s.MACs() {
s.RegisterSinkForTest(mac, func(eth []byte) {
se.got = append(se.got, receivedPacket{
port: mac,
eth: eth,
})
})
}
return se
}
func (se *sideEffects) logf(format string, args ...any) {
@ -318,7 +408,7 @@ func logSubstr(sub string) func(*sideEffects) error {
return nil
}
}
return fmt.Errorf("expected log substring %q not found; log statements were:\n%s", sub, strings.Join(se.logs, "\n"))
return fmt.Errorf("expected log substring %q not found", sub)
}
}
@ -327,16 +417,14 @@ func logSubstr(sub string) func(*sideEffects) error {
// substring sub.
func pktSubstr(sub string) func(*sideEffects) error {
return func(se *sideEffects) error {
var pkts bytes.Buffer
for i, pkt := range se.got {
pkt := gopacket.NewPacket(pkt, layers.LayerTypeEthernet, gopacket.Lazy)
for _, pkt := range se.got {
pkt := gopacket.NewPacket(pkt.eth, layers.LayerTypeEthernet, gopacket.Lazy)
got := pkt.String()
fmt.Fprintf(&pkts, "[pkt%d]:\n%s\n", i, got)
if strings.Contains(got, sub) {
return nil
}
}
return fmt.Errorf("packet summary with substring %q not found; packets were:\n%s", sub, pkts.Bytes())
return fmt.Errorf("packet summary with substring %q not found", sub)
}
}
@ -347,13 +435,7 @@ func numPkts(want int) func(*sideEffects) error {
if len(se.got) == want {
return nil
}
var pkts bytes.Buffer
for i, pkt := range se.got {
pkt := gopacket.NewPacket(pkt, layers.LayerTypeEthernet, gopacket.Lazy)
got := pkt.String()
fmt.Fprintf(&pkts, "[pkt%d]:\n%s\n", i, got)
}
return fmt.Errorf("got %d packets, want %d. packets were:\n%s", len(se.got), want, pkts.Bytes())
return fmt.Errorf("got %d packets, want %d", len(se.got), want)
}
}