// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package dnscache
import (
"bytes"
"context"
"errors"
"fmt"
"net"
"runtime"
"testing"
"time"
"golang.org/x/net/dns/dnsmessage"
"tailscale.com/tstest"
)
func TestMessageCache(t *testing.T) {
clock := &tstest.Clock{
Start: time.Date(1987, 11, 1, 0, 0, 0, 0, time.UTC),
}
mc := &MessageCache{Clock: clock.Now}
mc.SetMaxCacheSize(2)
clock.Advance(time.Second)
var out bytes.Buffer
if err := mc.ReplyFromCache(&out, makeQ(1, "foo.com.")); err != ErrCacheMiss {
t.Fatalf("unexpected error: %v", err)
}
if err := mc.AddCacheEntry(
makeQ(2, "foo.com."),
makeRes(2, "FOO.COM.", ttlOpt(10),
&dnsmessage.AResource{A: [4]byte{127, 0, 0, 1}},
&dnsmessage.AResource{A: [4]byte{127, 0, 0, 2}})); err != nil {
t.Fatal(err)
}
// Expect cache hit, with 10 seconds remaining.
out.Reset()
if err := mc.ReplyFromCache(&out, makeQ(3, "foo.com.")); err != nil {
t.Fatalf("expected cache hit; got: %v", err)
}
if p := mustParseResponse(t, out.Bytes()); p.TxID != 3 {
t.Errorf("TxID = %v; want %v", p.TxID, 3)
} else if p.TTL != 10 {
t.Errorf("TTL = %v; want 10", p.TTL)
}
// One second elapses, expect a cache hit, with 9 seconds
// remaining.
clock.Advance(time.Second)
out.Reset()
if err := mc.ReplyFromCache(&out, makeQ(4, "foo.com.")); err != nil {
t.Fatalf("expected cache hit; got: %v", err)
}
if p := mustParseResponse(t, out.Bytes()); p.TxID != 4 {
t.Errorf("TxID = %v; want %v", p.TxID, 4)
} else if p.TTL != 9 {
t.Errorf("TTL = %v; want 9", p.TTL)
}
// Expect cache miss on MX record.
if err := mc.ReplyFromCache(&out, makeQ(4, "foo.com.", dnsmessage.TypeMX)); err != ErrCacheMiss {
t.Fatalf("expected cache miss on MX; got: %v", err)
}
// Expect cache miss on CHAOS class.
if err := mc.ReplyFromCache(&out, makeQ(4, "foo.com.", dnsmessage.ClassCHAOS)); err != ErrCacheMiss {
t.Fatalf("expected cache miss on CHAOS; got: %v", err)
}
// Ten seconds elapses; expect a cache miss.
clock.Advance(10 * time.Second)
if err := mc.ReplyFromCache(&out, makeQ(5, "foo.com.")); err != ErrCacheMiss {
t.Fatalf("expected cache miss, got: %v", err)
}
}
type parsedMeta struct {
TxID uint16
TTL uint32
}
func mustParseResponse(t testing.TB, r []byte) (ret parsedMeta) {
t.Helper()
var p dnsmessage.Parser
h, err := p.Start(r)
if err != nil {
t.Fatal(err)
}
ret.TxID = h.ID
qq, err := p.AllQuestions()
if err != nil {
t.Fatalf("AllQuestions: %v", err)
}
if len(qq) != 1 {
t.Fatalf("num questions = %v; want 1", len(qq))
}
aa, err := p.AllAnswers()
if err != nil {
t.Fatalf("AllAnswers: %v", err)
}
for _, r := range aa {
if ret.TTL == 0 {
ret.TTL = r.Header.TTL
}
if ret.TTL != r.Header.TTL {
t.Fatal("mixed TTLs")
}
}
return ret
}
type responseOpt bool
type ttlOpt uint32
func makeQ(txID uint16, name string, opt ...any) []byte {
opt = append(opt, responseOpt(false))
return makeDNSPkt(txID, name, opt...)
}
func makeRes(txID uint16, name string, opt ...any) []byte {
opt = append(opt, responseOpt(true))
return makeDNSPkt(txID, name, opt...)
}
func makeDNSPkt(txID uint16, name string, opt ...any) []byte {
typ := dnsmessage.TypeA
class := dnsmessage.ClassINET
var response bool
var answers []dnsmessage.ResourceBody
var ttl uint32 = 1 // one second by default
for _, o := range opt {
switch o := o.(type) {
case dnsmessage.Type:
typ = o
case dnsmessage.Class:
class = o
case responseOpt:
response = bool(o)
case dnsmessage.ResourceBody:
answers = append(answers, o)
case ttlOpt:
ttl = uint32(o)
default:
panic(fmt.Sprintf("unknown opt type %T", o))
}
}
qname := dnsmessage.MustNewName(name)
msg := dnsmessage.Message{
Header: dnsmessage.Header{ID: txID, Response: response},
Questions: []dnsmessage.Question{
{
Name: qname,
Type: typ,
Class: class,
},
},
}
for _, rb := range answers {
msg.Answers = append(msg.Answers, dnsmessage.Resource{
Header: dnsmessage.ResourceHeader{
Name: qname,
Type: typ,
Class: class,
TTL: ttl,
},
Body: rb,
})
}
buf, err := msg.Pack()
if err != nil {
panic(err)
}
return buf
}
func TestASCIILowerName(t *testing.T) {
n := asciiLowerName(dnsmessage.MustNewName("Foo.COM."))
if got, want := n.String(), "foo.com."; got != want {
t.Errorf("got = %q; want %q", got, want)
}
}
func TestGetDNSQueryCacheKey(t *testing.T) {
tests := []struct {
name string
pkt []byte
want msgQ
txID uint16
anyTX bool
}{
{
name: "empty",
},
{
name: "a",
pkt: makeQ(123, "foo.com."),
want: msgQ{"foo.com.", dnsmessage.TypeA},
txID: 123,
},
{
name: "aaaa",
pkt: makeQ(6, "foo.com.", dnsmessage.TypeAAAA),
want: msgQ{"foo.com.", dnsmessage.TypeAAAA},
txID: 6,
},
{
name: "normalize_case",
pkt: makeQ(123, "FoO.CoM."),
want: msgQ{"foo.com.", dnsmessage.TypeA},
txID: 123,
},
{
name: "ignore_response",
pkt: makeRes(123, "foo.com."),
},
{
name: "ignore_question_with_answers",
pkt: makeQ(2, "foo.com.", &dnsmessage.AResource{A: [4]byte{127, 0, 0, 1}}),
},
{
name: "whatever_go_generates", // in case Go's net package grows functionality we don't handle
pkt: getGoNetPacketDNSQuery("from-go.foo."),
want: msgQ{"from-go.foo.", dnsmessage.TypeA},
anyTX: true,
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
got, gotTX, ok := getDNSQueryCacheKey(tt.pkt)
if !ok {
if tt.txID == 0 && got == (msgQ{}) {
return
}
t.Fatal("failed")
}
if got != tt.want {
t.Errorf("got %+v, want %+v", got, tt.want)
}
if gotTX != tt.txID && !tt.anyTX {
t.Errorf("got tx %v, want %v", gotTX, tt.txID)
}
})
}
}
func getGoNetPacketDNSQuery(name string) []byte {
if runtime.GOOS == "windows" {
// On Windows, Go's net.Resolver doesn't use the DNS client.
// See https://github.com/golang/go/issues/33097 which
// was approved but not yet implemented.
// For now just pretend it's implemented to make this test
// pass on Windows with complicated the caller.
return makeQ(123, name)
}
res := make(chan []byte, 1)
r := &net.Resolver{
PreferGo: true,
Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
return goResolverConn(res), nil
},
}
r.LookupIP(context.Background(), "ip4", name)
return <-res
}
type goResolverConn chan<- []byte
func (goResolverConn) Close() error { return nil }
func (goResolverConn) LocalAddr() net.Addr { return todoAddr{} }
func (goResolverConn) RemoteAddr() net.Addr { return todoAddr{} }
func (goResolverConn) SetDeadline(t time.Time) error { return nil }
func (goResolverConn) SetReadDeadline(t time.Time) error { return nil }
func (goResolverConn) SetWriteDeadline(t time.Time) error { return nil }
func (goResolverConn) Read([]byte) (int, error) { return 0, errors.New("boom") }
func (c goResolverConn) Write(p []byte) (int, error) {
select {
case c <- p[2:]: // skip 2 byte length for TCP mode DNS query
default:
}
return 0, errors.New("boom")
}
type todoAddr struct{}
func (todoAddr) Network() string { return "unused" }
func (todoAddr) String() string { return "unused-todoAddr" }