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tstest/natlab/vnet: start adding tests 

And refactor some of vnet.go for testability.

The only behavioral change (with a new test) is that ethernet
broadcasts no longer get sent back to the sender.

Updates #13038

Change-Id: Ic2e7e7d6d8805b7b7f2b5c52c2c5ba97101cef14
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2024-08-26 22:21:14 -07:00 committed by Brad Fitzpatrick
parent 31cdbd68b1
commit ff1d0aa027
3 changed files with 403 additions and 100 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
tstest/natlab/vnet/conf.go
View File

@ -6,7 +6,6 @@ package vnet
import (
"cmp"
"fmt"
"log"
"net/netip"
"os"
"slices"
@ -61,6 +60,11 @@ func (c *Config) FirstNetwork() *Network {
return c.networks[0]
}
func nodeMac(n int) MAC {
// 52=TS then 0xcc for cccclient
return MAC{0x52, 0xcc, 0xcc, 0xcc, 0xcc, byte(n)}
}
// AddNode creates a new node in the world.
//
// The opts may be of the following types:
@ -70,10 +74,10 @@ func (c *Config) FirstNetwork() *Network {
// On an error or unknown opt type, AddNode returns a
// node with a carried error that gets returned later.
func (c *Config) AddNode(opts ...any) *Node {
num := len(c.nodes)
num := len(c.nodes) + 1
n := &Node{
num: num + 1,
mac: MAC{0x52, 0xcc, 0xcc, 0xcc, 0xcc, byte(num) + 1}, // 52=TS then 0xcc for ccclient
num: num,
mac: nodeMac(num),
}
c.nodes = append(c.nodes, n)
for _, o := range opts {
@ -130,10 +134,10 @@ type TailscaledEnv struct {
// On an error or unknown opt type, AddNetwork returns a
// network with a carried error that gets returned later.
func (c *Config) AddNetwork(opts ...any) *Network {
num := len(c.networks)
num := len(c.networks) + 1
n := &Network{
num: num + 1,
mac: MAC{0x52, 0xee, 0xee, 0xee, 0xee, byte(num) + 1}, // 52=TS then 0xee for 'etwork
num: num,
mac: MAC{0x52, 0xee, 0xee, 0xee, 0xee, byte(num)}, // 52=TS then 0xee for 'etwork
}
c.networks = append(c.networks, n)
for _, o := range opts {
@ -330,7 +334,7 @@ func (s *Server) initFromConfig(c *Config) error {
lanIP4: conf.lanIP4,
nodesByIP4: map[netip.Addr]*node{},
nodesByMAC: map[MAC]*node{},
logf: logger.WithPrefix(log.Printf, fmt.Sprintf("[net-%v] ", conf.mac)),
logf: logger.WithPrefix(s.logf, fmt.Sprintf("[net-%v] ", conf.mac)),
}
netOfConf[conf] = n
s.networks.Add(n)

225
tstest/natlab/vnet/vnet.go
View File

@ -9,12 +9,9 @@
package vnet
// TODO:
// - [ ] port mapping actually working
// - [ ] conf to let you firewall things
// - [ ] tests for NAT tables
import (
"bufio"
"bytes"
"context"
"crypto/tls"
@ -23,7 +20,9 @@ import (
"errors"
"fmt"
"io"
"iter"
"log"
"maps"
"math/rand/v2"
"net"
"net/http"
@ -493,18 +492,22 @@ type portMapping struct {
expiry time.Time
}
type writerFunc func([]byte, *net.UnixAddr, int)
// writerFunc is a function that writes an Ethernet frame to a connected client.
//
// ethFrame is the Ethernet frame to write.
//
// interfaceIndexID is the interface ID for the pcap file.
type writerFunc func(dst vmClient, ethFrame []byte, interfaceIndexID int)
// Encapsulates both a write function, an optional outbound socket address
// for dgram mode and an interfaceID for packet captures.
// networkWriter are the arguments to a writerFunc and the writerFunc.
type networkWriter struct {
writer writerFunc // Function to write packets to the network
addr *net.UnixAddr // Outbound socket address for dgram mode
c vmClient
interfaceID int // The interface ID of the src node (for writing pcaps)
}
func (nw *networkWriter) write(b []byte) {
nw.writer(b, nw.addr, nw.interfaceID)
func (nw networkWriter) write(b []byte) {
nw.writer(nw.c, b, nw.interfaceID)
}
type network struct {
@ -540,19 +543,20 @@ type network struct {
writers syncs.Map[MAC, networkWriter] // MAC -> to networkWriter for that MAC
}
// Regsiters a writerFunc for a MAC address.
// raddr is and optional outbound socket address of the client interface for dgram mode.
// Pass nil for the writerFunc to deregister the writer.
func (n *network) registerWriter(mac MAC, raddr *net.UnixAddr, interfaceID int, wf writerFunc) {
if wf != nil {
n.writers.Store(mac, networkWriter{
writer: wf,
addr: raddr,
interfaceID: interfaceID,
})
} else {
n.writers.Delete(mac)
// registerWriter registers a client address with a MAC address.
func (n *network) registerWriter(mac MAC, c vmClient) {
nw := networkWriter{
writer: n.s.writeEthernetFrameToVM,
c: c,
}
if node, ok := n.s.nodeByMAC[mac]; ok {
nw.interfaceID = node.interfaceID
}
n.writers.Store(mac, nw)
}
func (n *network) unregisterWriter(mac MAC) {
n.writers.Delete(mac)
}
func (n *network) MACOfIP(ip netip.Addr) (_ MAC, ok bool) {
@ -616,6 +620,8 @@ type Server struct {
wg sync.WaitGroup
blendReality bool
optLogf func(format string, args ...any) // or nil to use log.Printf
derpIPs set.Set[netip.Addr]
nodes []*node
@ -627,12 +633,28 @@ type Server struct {
derps []*derpServer
pcapWriter *pcapWriter
// writeMu serializes all writes to VM clients.
writeMu sync.Mutex
scratch []byte
mu sync.Mutex
agentConnWaiter map[*node]chan<- struct{} // signaled after added to set
agentConns set.Set[*agentConn] // not keyed by node; should be small/cheap enough to scan all
agentDialer map[*node]DialFunc
}
func (s *Server) logf(format string, args ...any) {
if s.optLogf != nil {
s.optLogf(format, args...)
} else {
log.Printf(format, args...)
}
}
func (s *Server) SetLoggerForTest(logf func(format string, args ...any)) {
s.optLogf = logf
}
type DialFunc func(ctx context.Context, network, address string) (net.Conn, error)
var derpMap = &tailcfg.DERPMap{
@ -713,6 +735,23 @@ func (s *Server) Close() {
s.wg.Wait()
}
// MACs returns the MAC addresses of the configured nodes.
func (s *Server) MACs() iter.Seq[MAC] {
return maps.Keys(s.nodeByMAC)
}
func (s *Server) RegisterSinkForTest(mac MAC, fn func(eth []byte)) {
n, ok := s.nodeByMAC[mac]
if !ok {
log.Fatalf("RegisterSinkForTest: unknown MAC %v", mac)
}
n.net.writers.Store(mac, networkWriter{
writer: func(_ vmClient, eth []byte, _ int) {
fn(eth)
},
})
}
func (s *Server) HWAddr(mac MAC) net.HardwareAddr {
// TODO: cache
return net.HardwareAddr(mac[:])
@ -725,6 +764,53 @@ const (
ProtocolUnixDGRAM // for macOS Virtualization.Framework and VZFileHandleNetworkDeviceAttachment
)
func (s *Server) writeEthernetFrameToVM(c vmClient, ethPkt []byte, interfaceID int) {
s.writeMu.Lock()
defer s.writeMu.Unlock()
if ethPkt == nil {
return
}
switch c.proto() {
case ProtocolQEMU:
s.scratch = binary.BigEndian.AppendUint32(s.scratch[:0], uint32(len(ethPkt)))
s.scratch = append(s.scratch, ethPkt...)
if _, err := c.uc.Write(s.scratch); err != nil {
log.Printf("Write pkt: %v", err)
}
case ProtocolUnixDGRAM:
if _, err := c.uc.WriteToUnix(ethPkt, c.raddr); err != nil {
log.Printf("Write pkt : %v", err)
return
}
}
must.Do(s.pcapWriter.WritePacket(gopacket.CaptureInfo{
Timestamp: time.Now(),
CaptureLength: len(ethPkt),
Length: len(ethPkt),
InterfaceIndex: interfaceID,
}, ethPkt))
}
// vmClient is a comparable value representing a connection from a VM, either a
// QEMU-style client (with streams over a Unix socket) or a datagram based
// client (such as macOS Virtualization.framework clients).
type vmClient struct {
uc *net.UnixConn
raddr *net.UnixAddr // nil for QEMU-style clients using streams; else datagram source
}
func (c vmClient) proto() Protocol {
if c.raddr == nil {
return ProtocolQEMU
}
return ProtocolUnixDGRAM
}
const ethernetHeaderLen = 14
// Handles a single connection from a QEMU-style client or muxd connections for dgram mode
func (s *Server) ServeUnixConn(uc *net.UnixConn, proto Protocol) {
if s.shuttingDown.Load() {
@ -738,51 +824,8 @@ func (s *Server) ServeUnixConn(uc *net.UnixConn, proto Protocol) {
log.Printf("Got conn %T %p", uc, uc)
defer uc.Close()
bw := bufio.NewWriterSize(uc, 2<<10)
var writeMu sync.Mutex
writePkt := func(pkt []byte, raddr *net.UnixAddr, interfaceID int) {
if pkt == nil {
return
}
writeMu.Lock()
defer writeMu.Unlock()
switch proto {
case ProtocolQEMU:
hdr := binary.BigEndian.AppendUint32(bw.AvailableBuffer()[:0], uint32(len(pkt)))
if _, err := bw.Write(hdr); err != nil {
log.Printf("Write hdr: %v", err)
return
}
if _, err := bw.Write(pkt); err != nil {
log.Printf("Write pkt: %v", err)
return
}
case ProtocolUnixDGRAM:
if raddr == nil {
log.Printf("Write pkt: dgram mode write failure, no outbound socket address")
return
}
if _, err := uc.WriteToUnix(pkt, raddr); err != nil {
log.Printf("Write pkt : %v", err)
return
}
}
if err := bw.Flush(); err != nil {
log.Printf("Flush: %v", err)
}
must.Do(s.pcapWriter.WritePacket(gopacket.CaptureInfo{
Timestamp: time.Now(),
CaptureLength: len(pkt),
Length: len(pkt),
InterfaceIndex: interfaceID,
}, pkt))
}
buf := make([]byte, 16<<10)
didReg := map[MAC]bool{}
for {
var packetRaw []byte
var raddr *net.UnixAddr
@ -817,28 +860,43 @@ func (s *Server) ServeUnixConn(uc *net.UnixConn, proto Protocol) {
}
packetRaw = buf[4 : 4+n] // raw ethernet frame
}
c := vmClient{uc, raddr}
// For the first packet from a MAC, register a writerFunc to write to the VM.
if len(packetRaw) < ethernetHeaderLen {
continue
}
srcMAC := MAC(packetRaw[6:12])
srcNode, ok := s.nodeByMAC[srcMAC]
if !ok {
log.Printf("[conn %p] got frame from unknown MAC %v", c.uc, srcMAC)
continue
}
if !didReg[srcMAC] {
didReg[srcMAC] = true
log.Printf("[conn %p] Registering writer for MAC %v, node %v", c.uc, srcMAC, srcNode.lanIP)
srcNode.net.registerWriter(srcMAC, c)
defer srcNode.net.unregisterWriter(srcMAC)
}
if err := s.handleEthernetFrameFromVM(packetRaw); err != nil {
srcNode.net.logf("handleEthernetFrameFromVM: [conn %p], %v", c.uc, err)
}
}
}
func (s *Server) handleEthernetFrameFromVM(packetRaw []byte) error {
packet := gopacket.NewPacket(packetRaw, layers.LayerTypeEthernet, gopacket.Lazy)
le, ok := packet.LinkLayer().(*layers.Ethernet)
if !ok || len(le.SrcMAC) != 6 || len(le.DstMAC) != 6 {
log.Printf("ignoring non-Ethernet packet: % 02x", packetRaw)
continue
return fmt.Errorf("ignoring non-Ethernet packet: % 02x", packetRaw)
}
ep := EthernetPacket{le, packet}
srcMAC := ep.SrcMAC()
srcNode, ok := s.nodeByMAC[srcMAC]
if !ok {
log.Printf("[conn %p] got frame from unknown MAC %v", uc, srcMAC)
continue
}
// Register a writer for the source MAC address if one doesn't exist.
if _, ok := srcNode.net.writers.Load(srcMAC); !ok {
log.Printf("[conn %p] Registering writer for MAC %v is node %v", uc, srcMAC, srcNode.lanIP)
srcNode.net.registerWriter(srcMAC, raddr, srcNode.interfaceID, writePkt)
defer srcNode.net.registerWriter(srcMAC, nil, 0, nil)
continue
return fmt.Errorf("got frame from unknown MAC %v", srcMAC)
}
must.Do(s.pcapWriter.WritePacket(gopacket.CaptureInfo{
@ -848,7 +906,7 @@ func (s *Server) ServeUnixConn(uc *net.UnixConn, proto Protocol) {
InterfaceIndex: srcNode.interfaceID,
}, packetRaw))
srcNode.net.HandleEthernetPacket(ep)
}
return nil
}
func (s *Server) routeUDPPacket(up UDPPacket) {
@ -896,8 +954,10 @@ func (n *network) writeEth(res []byte) bool {
if dstMAC.IsBroadcast() {
num := 0
n.writers.Range(func(mac MAC, nw networkWriter) bool {
if mac != srcMAC {
num++
nw.write(res)
}
return true
})
return num > 0
@ -922,6 +982,11 @@ func (n *network) writeEth(res []byte) bool {
var (
macAllRouters = MAC{0: 0x33, 1: 0x33, 5: 0x02}
macBroadcast = MAC{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}
)
const (
testingEthertype layers.EthernetType = 0x1234
)
func (n *network) HandleEthernetPacket(ep EthernetPacket) {
@ -943,6 +1008,8 @@ func (n *network) HandleEthernetPacket(ep EthernetPacket) {
default:
n.logf("Dropping non-IP packet: %v", ep.le.EthernetType)
return
case 0x1234:
// Permitted for testing. Not a real ethertype.
case layers.EthernetTypeARP:
res, err := n.createARPResponse(packet)
if err != nil {
@ -1309,7 +1376,7 @@ func (n *network) handleIPv6RouterSolicitation(ep EthernetPacket, rs *layers.ICM
DstMAC: ep.SrcMAC().HWAddr(),
EthernetType: layers.EthernetTypeIPv6,
}
n.logf("sending IPv6 router advertisement to %v from %v", eth.SrcMAC, eth.DstMAC)
n.logf("sending IPv6 router advertisement to %v from %v", eth.DstMAC, eth.SrcMAC)
ip := &layers.IPv6{
Version: 6,
HopLimit: 255,

232
tstest/natlab/vnet/vnet_test.go Normal file
View File

@ -0,0 +1,232 @@
// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package vnet
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"net"
"net/netip"
"strings"
"testing"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
)
// TestPacketSideEffects tests that upon receiving certain
// packets, other packets and/or log statements are generated.
func TestPacketSideEffects(t *testing.T) {
type netTest struct {
name string
pkt []byte // to send
check func(*sideEffects) error
}
tests := []struct {
netName string // name of the Server returned by setup
setup func() (*Server, error)
tests []netTest // to run against setup's Server
}{
{
netName: "basic",
setup: func() (*Server, error) {
var c Config
nw := c.AddNetwork("192.168.0.1/24")
c.AddNode(nw)
c.AddNode(nw)
return New(&c)
},
tests: []netTest{
{
name: "drop-rando-ethertype",
pkt: mkEth(nodeMac(2), nodeMac(1), 0x4321, []byte("hello")),
check: all(
logSubstr("Dropping non-IP packet"),
),
},
{
name: "dst-mac-between-nodes",
pkt: mkEth(nodeMac(2), nodeMac(1), testingEthertype, []byte("hello")),
check: all(
numPkts(1),
pktSubstr("SrcMAC=52:cc:cc:cc:cc:01 DstMAC=52:cc:cc:cc:cc:02 EthernetType=UnknownEthernetType"),
pktSubstr("Unable to decode EthernetType 4660"),
),
},
{
name: "broadcast-mac",
pkt: mkEth(macBroadcast, nodeMac(1), testingEthertype, []byte("hello")),
check: all(
numPkts(1),
pktSubstr("SrcMAC=52:cc:cc:cc:cc:01 DstMAC=ff:ff:ff:ff:ff:ff EthernetType=UnknownEthernetType"),
pktSubstr("Unable to decode EthernetType 4660"),
),
},
},
},
{
netName: "v6",
setup: func() (*Server, error) {
var c Config
c.AddNode(c.AddNetwork("2000:52::1/64"))
return New(&c)
},
tests: []netTest{
{
name: "router-solicit",
pkt: mkIPv6RouterSolicit(nodeMac(1), netip.MustParseAddr("fe80::50cc:ccff:fecc:cc01")),
check: all(
logSubstr("sending IPv6 router advertisement to 52:cc:cc:cc:cc:01 from 52:ee:ee:ee:ee:01"),
numPkts(1),
pktSubstr("TypeCode=RouterAdvertisement"),
pktSubstr("= ICMPv6RouterAdvertisement"),
pktSubstr("SrcMAC=52:ee:ee:ee:ee:01 DstMAC=52:cc:cc:cc:cc:01 EthernetType=IPv6"),
),
},
},
},
}
for _, tt := range tests {
t.Run(tt.netName, func(t *testing.T) {
s, err := tt.setup()
if err != nil {
t.Fatal(err)
}
defer s.Close()
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)
})
}
s.handleEthernetFrameFromVM(tt.pkt)
if tt.check != nil {
if err := tt.check(se); err != nil {
t.Fatal(err)
}
}
})
}
})
}
}
// mkEth encodes an ethernet frame with the given payload.
func mkEth(dst, src MAC, ethType layers.EthernetType, payload []byte) []byte {
ret := make([]byte, 0, 14+len(payload))
ret = append(ret, dst.HWAddr()...)
ret = append(ret, src.HWAddr()...)
ret = binary.BigEndian.AppendUint16(ret, uint16(ethType))
return append(ret, payload...)
}
// mkIPv6RouterSolicit makes a IPv6 router solicitation packet
// ethernet frame.
func mkIPv6RouterSolicit(srcMAC MAC, srcIP netip.Addr) []byte {
ip := &layers.IPv6{
Version: 6,
HopLimit: 255,
NextHeader: layers.IPProtocolICMPv6,
SrcIP: srcIP.AsSlice(),
DstIP: net.ParseIP("ff02::2"), // all routers
}
icmp := &layers.ICMPv6{
TypeCode: layers.CreateICMPv6TypeCode(layers.ICMPv6TypeRouterSolicitation, 0),
}
ra := &layers.ICMPv6RouterSolicitation{
Options: []layers.ICMPv6Option{{
Type: layers.ICMPv6OptSourceAddress,
Data: srcMAC.HWAddr(),
}},
}
icmp.SetNetworkLayerForChecksum(ip)
buf := gopacket.NewSerializeBuffer()
options := gopacket.SerializeOptions{FixLengths: true, ComputeChecksums: true}
if err := gopacket.SerializeLayers(buf, options, ip, icmp, ra); err != nil {
panic(fmt.Sprintf("serializing ICMPv6 RA: %v", err))
}
return mkEth(macAllRouters, srcMAC, layers.EthernetTypeIPv6, buf.Bytes())
}
// 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
}
func (se *sideEffects) logf(format string, args ...any) {
se.logs = append(se.logs, fmt.Sprintf(format, args...))
}
// all aggregates several side effects checkers into one.
func all(checks ...func(*sideEffects) error) func(*sideEffects) error {
return func(se *sideEffects) error {
var errs []error
for _, check := range checks {
if err := check(se); err != nil {
errs = append(errs, err)
}
}
return errors.Join(errs...)
}
}
// logSubstr returns a side effect checker func that checks
// whether a log statement was output containing substring sub.
func logSubstr(sub string) func(*sideEffects) error {
return func(se *sideEffects) error {
for _, log := range se.logs {
if strings.Contains(log, sub) {
return nil
}
}
return fmt.Errorf("expected log substring %q not found; log statements were %q", sub, se.logs)
}
}
// pkgSubstr returns a side effect checker func that checks whether an ethernet
// packet was received that, once decoded and stringified by gopacket, contains
// 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)
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())
}
}
// numPkts returns a side effect checker func that checks whether
// the received number of ethernet packets was the given number.
func numPkts(want int) func(*sideEffects) error {
return func(se *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())
}
}