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Move wgengine/tsdns to net/dns.

Browse Source 
Straight move+fixup, no other changes. In prep for merging with
wgengine/router/dns.

Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson
2021-03-25 14:50:21 -07:00
committed by Dave Anderson
parent 81143b6d9a
commit 8432999835
15 changed files with 32 additions and 32 deletions
Download Patch File Download Diff File Expand all files Collapse all files

474
net/dns/forwarder.go Normal file
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// Copyright (c) 2020 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 dns
import (
"bytes"
"context"
"encoding/binary"
"errors"
"fmt"
"hash/crc32"
"math/rand"
"net"
"os"
"sync"
"time"
"inet.af/netaddr"
"tailscale.com/logtail/backoff"
"tailscale.com/net/netns"
"tailscale.com/types/logger"
)
// headerBytes is the number of bytes in a DNS message header.
const headerBytes = 12
// connCount is the number of UDP connections to use for forwarding.
const connCount = 32
const (
// cleanupInterval is the interval between purged of timed-out entries from txMap.
cleanupInterval = 30 * time.Second
// responseTimeout is the maximal amount of time to wait for a DNS response.
responseTimeout = 5 * time.Second
)
var errNoUpstreams = errors.New("upstream nameservers not set")
var aLongTimeAgo = time.Unix(0, 1)
type forwardingRecord struct {
src netaddr.IPPort
createdAt time.Time
}
// txid identifies a DNS transaction.
//
// As the standard DNS Request ID is only 16 bits, we extend it:
// the lower 32 bits are the zero-extended bits of the DNS Request ID;
// the upper 32 bits are the CRC32 checksum of the first question in the request.
// This makes probability of txid collision negligible.
type txid uint64
// getTxID computes the txid of the given DNS packet.
func getTxID(packet []byte) txid {
if len(packet) < headerBytes {
return 0
}
dnsid := binary.BigEndian.Uint16(packet[0:2])
qcount := binary.BigEndian.Uint16(packet[4:6])
if qcount == 0 {
return txid(dnsid)
}
offset := headerBytes
for i := uint16(0); i < qcount; i++ {
// Note: this relies on the fact that names are not compressed in questions,
// so they are guaranteed to end with a NUL byte.
//
// Justification:
// RFC 1035 doesn't seem to explicitly prohibit compressing names in questions,
// but this is exceedingly unlikely to be done in practice. A DNS request
// with multiple questions is ill-defined (which questions do the header flags apply to?)
// and a single question would have to contain a pointer to an *answer*,
// which would be excessively smart, pointless (an answer can just as well refer to the question)
// and perhaps even prohibited: a draft RFC (draft-ietf-dnsind-local-compression-05) states:
//
// > It is important that these pointers always point backwards.
//
// This is said in summarizing RFC 1035, although that phrase does not appear in the original RFC.
// Additionally, (https://cr.yp.to/djbdns/notes.html) states:
//
// > The precise rule is that a name can be compressed if it is a response owner name,
// > the name in NS data, the name in CNAME data, the name in PTR data, the name in MX data,
// > or one of the names in SOA data.
namebytes := bytes.IndexByte(packet[offset:], 0)
// ... | name | NUL | type | class
// ?? 1 2 2
offset = offset + namebytes + 5
if len(packet) < offset {
// Corrupt packet; don't crash.
return txid(dnsid)
}
}
hash := crc32.ChecksumIEEE(packet[headerBytes:offset])
return (txid(hash) << 32) | txid(dnsid)
}
// forwarder forwards DNS packets to a number of upstream nameservers.
type forwarder struct {
logf logger.Logf
// responses is a channel by which responses are returned.
responses chan Packet
// closed signals all goroutines to stop.
closed chan struct{}
// wg signals when all goroutines have stopped.
wg sync.WaitGroup
// conns are the UDP connections used for forwarding.
// A random one is selected for each request, regardless of the target upstream.
conns []*fwdConn
mu sync.Mutex
// upstreams are the nameserver addresses that should be used for forwarding.
upstreams []net.Addr
// txMap maps DNS txids to active forwarding records.
txMap map[txid]forwardingRecord
}
func init() {
rand.Seed(time.Now().UnixNano())
}
func newForwarder(logf logger.Logf, responses chan Packet) *forwarder {
return &forwarder{
logf: logger.WithPrefix(logf, "forward: "),
responses: responses,
closed: make(chan struct{}),
conns: make([]*fwdConn, connCount),
txMap: make(map[txid]forwardingRecord),
}
}
func (f *forwarder) Start() error {
f.wg.Add(connCount + 1)
for idx := range f.conns {
f.conns[idx] = newFwdConn(f.logf, idx)
go f.recv(f.conns[idx])
}
go f.cleanMap()
return nil
}
func (f *forwarder) Close() {
select {
case <-f.closed:
return
default:
// continue
}
close(f.closed)
for _, conn := range f.conns {
conn.close()
}
f.wg.Wait()
}
func (f *forwarder) rebindFromNetworkChange() {
for _, c := range f.conns {
c.mu.Lock()
c.reconnectLocked()
c.mu.Unlock()
}
}
func (f *forwarder) setUpstreams(upstreams []net.Addr) {
f.mu.Lock()
f.upstreams = upstreams
f.mu.Unlock()
}
// send sends packet to dst. It is best effort.
func (f *forwarder) send(packet []byte, dst net.Addr) {
connIdx := rand.Intn(connCount)
conn := f.conns[connIdx]
conn.send(packet, dst)
}
func (f *forwarder) recv(conn *fwdConn) {
defer f.wg.Done()
for {
select {
case <-f.closed:
return
default:
}
out := make([]byte, maxResponseBytes)
n := conn.read(out)
if n == 0 {
continue
}
if n < headerBytes {
f.logf("recv: packet too small (%d bytes)", n)
}
out = out[:n]
txid := getTxID(out)
f.mu.Lock()
record, found := f.txMap[txid]
// At most one nameserver will return a response:
// the first one to do so will delete txid from the map.
if !found {
f.mu.Unlock()
continue
}
delete(f.txMap, txid)
f.mu.Unlock()
packet := Packet{
Payload: out,
Addr: record.src,
}
select {
case <-f.closed:
return
case f.responses <- packet:
// continue
}
}
}
// cleanMap periodically deletes timed-out forwarding records from f.txMap to bound growth.
func (f *forwarder) cleanMap() {
defer f.wg.Done()
t := time.NewTicker(cleanupInterval)
defer t.Stop()
var now time.Time
for {
select {
case <-f.closed:
return
case now = <-t.C:
// continue
}
f.mu.Lock()
for k, v := range f.txMap {
if now.Sub(v.createdAt) > responseTimeout {
delete(f.txMap, k)
}
}
f.mu.Unlock()
}
}
// forward forwards the query to all upstream nameservers and returns the first response.
func (f *forwarder) forward(query Packet) error {
txid := getTxID(query.Payload)
f.mu.Lock()
upstreams := f.upstreams
if len(upstreams) == 0 {
f.mu.Unlock()
return errNoUpstreams
}
f.txMap[txid] = forwardingRecord{
src: query.Addr,
createdAt: time.Now(),
}
f.mu.Unlock()
for _, upstream := range upstreams {
f.send(query.Payload, upstream)
}
return nil
}
// A fwdConn manages a single connection used to forward DNS requests.
// Net link changes can cause a *net.UDPConn to become permanently unusable, particularly on macOS.
// fwdConn detects such situations and transparently creates new connections.
type fwdConn struct {
// logf allows a fwdConn to log.
logf logger.Logf
// wg tracks the number of outstanding conn.Read and conn.Write calls.
wg sync.WaitGroup
// change allows calls to read to block until a the network connection has been replaced.
change *sync.Cond
// mu protects fields that follow it; it is also change's Locker.
mu sync.Mutex
// closed tracks whether fwdConn has been permanently closed.
closed bool
// conn is the current active connection.
conn net.PacketConn
}
func newFwdConn(logf logger.Logf, idx int) *fwdConn {
c := new(fwdConn)
c.logf = logger.WithPrefix(logf, fmt.Sprintf("fwdConn %d: ", idx))
c.change = sync.NewCond(&c.mu)
// c.conn is created lazily in send
return c
}
// send sends packet to dst using c's connection.
// It is best effort. It is UDP, after all. Failures are logged.
func (c *fwdConn) send(packet []byte, dst net.Addr) {
var b *backoff.Backoff // lazily initialized, since it is not needed in the common case
backOff := func(err error) {
if b == nil {
b = backoff.NewBackoff("dns-fwdConn-send", c.logf, 30*time.Second)
}
b.BackOff(context.Background(), err)
}
for {
// Gather the current connection.
// We can't hold the lock while we call WriteTo.
c.mu.Lock()
conn := c.conn
closed := c.closed
if closed {
c.mu.Unlock()
return
}
if conn == nil {
c.reconnectLocked()
c.mu.Unlock()
continue
}
c.mu.Unlock()
c.wg.Add(1)
_, err := conn.WriteTo(packet, dst)
c.wg.Done()
if err == nil {
// Success
return
}
if errors.Is(err, os.ErrDeadlineExceeded) {
// We intentionally closed this connection.
// It has been replaced by a new connection. Try again.
continue
}
// Something else went wrong.
// We have three choices here: try again, give up, or create a new connection.
var opErr *net.OpError
if !errors.As(err, &opErr) {
// Weird. All errors from the net package should be *net.OpError. Bail.
c.logf("send: non-*net.OpErr %v (%T)", err, err)
return
}
if opErr.Temporary() || opErr.Timeout() {
// I doubt that either of these can happen (this is UDP),
// but go ahead and try again.
backOff(err)
continue
}
if networkIsDown(err) {
// Fail.
c.logf("send: network is down")
return
}
if networkIsUnreachable(err) {
// This can be caused by a link change.
// Replace the existing connection with a new one.
c.mu.Lock()
// It's possible that multiple senders discovered simultaneously
// that the network is unreachable. Avoid reconnecting multiple times:
// Only reconnect if the current connection is the one that we
// discovered to be problematic.
if c.conn == conn {
backOff(err)
c.reconnectLocked()
}
c.mu.Unlock()
// Try again with our new network connection.
continue
}
// Unrecognized error. Fail.
c.logf("send: unrecognized error: %v", err)
return
}
}
// read waits for a response from c's connection.
// It returns the number of bytes read, which may be 0
// in case of an error or a closed connection.
func (c *fwdConn) read(out []byte) int {
for {
// Gather the current connection.
// We can't hold the lock while we call ReadFrom.
c.mu.Lock()
conn := c.conn
closed := c.closed
if closed {
c.mu.Unlock()
return 0
}
if conn == nil {
// There is no current connection.
// Wait for the connection to change, then try again.
c.change.Wait()
c.mu.Unlock()
continue
}
c.mu.Unlock()
c.wg.Add(1)
n, _, err := conn.ReadFrom(out)
c.wg.Done()
if err == nil {
// Success.
return n
}
if errors.Is(err, os.ErrDeadlineExceeded) {
// We intentionally closed this connection.
// It has been replaced by a new connection. Try again.
continue
}
c.logf("read: unrecognized error: %v", err)
return 0
}
}
// reconnectLocked replaces the current connection with a new one.
// c.mu must be locked.
func (c *fwdConn) reconnectLocked() {
c.closeConnLocked()
// Make a new connection.
conn, err := netns.Listener().ListenPacket(context.Background(), "udp", "")
if err != nil {
c.logf("ListenPacket failed: %v", err)
} else {
c.conn = conn
}
// Broadcast that a new connection is available.
c.change.Broadcast()
}
// closeCurrentConn closes the current connection.
// c.mu must be locked.
func (c *fwdConn) closeConnLocked() {
if c.conn == nil {
return
}
// Unblock all readers/writers, wait for them, close the connection.
c.conn.SetDeadline(aLongTimeAgo)
c.wg.Wait()
c.conn.Close()
c.conn = nil
}
// close permanently closes c.
func (c *fwdConn) close() {
c.mu.Lock()
defer c.mu.Unlock()
if c.closed {
return
}
c.closed = true
c.closeConnLocked()
// Unblock any remaining readers.
c.change.Broadcast()
}

160
net/dns/map.go Normal file
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// Copyright (c) 2020 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 dns
import (
"sort"
"strings"
"inet.af/netaddr"
)
// Map is all the data Resolver needs to resolve DNS queries within the Tailscale network.
type Map struct {
// nameToIP is a mapping of Tailscale domain names to their IP addresses.
// For example, monitoring.tailscale.us -> 100.64.0.1.
nameToIP map[string]netaddr.IP
// ipToName is the inverse of nameToIP.
ipToName map[netaddr.IP]string
// names are the keys of nameToIP in sorted order.
names []string
// rootDomains are the domains whose subdomains should always
// be resolved locally to prevent leakage of sensitive names.
rootDomains []string // e.g. "user.provider.beta.tailscale.net."
}
// NewMap returns a new Map with name to address mapping given by nameToIP.
//
// rootDomains are the domains whose subdomains should always be
// resolved locally to prevent leakage of sensitive names. They should
// end in a period ("user-foo.tailscale.net.").
func NewMap(initNameToIP map[string]netaddr.IP, rootDomains []string) *Map {
// TODO(dmytro): we have to allocate names and ipToName, but nameToIP can be avoided.
// It is here because control sends us names not in canonical form. Change this.
names := make([]string, 0, len(initNameToIP))
nameToIP := make(map[string]netaddr.IP, len(initNameToIP))
ipToName := make(map[netaddr.IP]string, len(initNameToIP))
for name, ip := range initNameToIP {
if len(name) == 0 {
// Nothing useful can be done with empty names.
continue
}
if name[len(name)-1] != '.' {
name += "."
}
names = append(names, name)
nameToIP[name] = ip
ipToName[ip] = name
}
sort.Strings(names)
return &Map{
nameToIP: nameToIP,
ipToName: ipToName,
names: names,
rootDomains: rootDomains,
}
}
func printSingleNameIP(buf *strings.Builder, name string, ip netaddr.IP) {
buf.WriteString(name)
buf.WriteByte('\t')
buf.WriteString(ip.String())
buf.WriteByte('\n')
}
func (m *Map) Pretty() string {
buf := new(strings.Builder)
for _, name := range m.names {
printSingleNameIP(buf, name, m.nameToIP[name])
}
return buf.String()
}
func (m *Map) PrettyDiffFrom(old *Map) string {
var (
oldNameToIP map[string]netaddr.IP
newNameToIP map[string]netaddr.IP
oldNames []string
newNames []string
)
if old != nil {
oldNameToIP = old.nameToIP
oldNames = old.names
}
if m != nil {
newNameToIP = m.nameToIP
newNames = m.names
}
buf := new(strings.Builder)
space := func() bool {
return buf.Len() < (1 << 10)
}
for len(oldNames) > 0 && len(newNames) > 0 {
var name string
newName, oldName := newNames[0], oldNames[0]
switch {
case oldName < newName:
name = oldName
oldNames = oldNames[1:]
case oldName > newName:
name = newName
newNames = newNames[1:]
case oldNames[0] == newNames[0]:
name = oldNames[0]
oldNames = oldNames[1:]
newNames = newNames[1:]
}
if !space() {
continue
}
ipOld, inOld := oldNameToIP[name]
ipNew, inNew := newNameToIP[name]
switch {
case !inOld:
buf.WriteByte('+')
printSingleNameIP(buf, name, ipNew)
case !inNew:
buf.WriteByte('-')
printSingleNameIP(buf, name, ipOld)
case ipOld != ipNew:
buf.WriteByte('-')
printSingleNameIP(buf, name, ipOld)
buf.WriteByte('+')
printSingleNameIP(buf, name, ipNew)
}
}
for _, name := range oldNames {
if !space() {
break
}
if _, ok := newNameToIP[name]; !ok {
buf.WriteByte('-')
printSingleNameIP(buf, name, oldNameToIP[name])
}
}
for _, name := range newNames {
if !space() {
break
}
if _, ok := oldNameToIP[name]; !ok {
buf.WriteByte('+')
printSingleNameIP(buf, name, newNameToIP[name])
}
}
if !space() {
buf.WriteString("... [truncated]\n")
}
return buf.String()
}

156
net/dns/map_test.go Normal file
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// Copyright (c) 2020 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 dns
import (
"fmt"
"strings"
"testing"
"inet.af/netaddr"
)
func TestPretty(t *testing.T) {
tests := []struct {
name string
dmap *Map
want string
}{
{"empty", NewMap(nil, nil), ""},
{
"single",
NewMap(map[string]netaddr.IP{
"hello.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
}, nil),
"hello.ipn.dev.\t100.101.102.103\n",
},
{
"multiple",
NewMap(map[string]netaddr.IP{
"test1.domain.": netaddr.IPv4(100, 101, 102, 103),
"test2.sub.domain.": netaddr.IPv4(100, 99, 9, 1),
}, nil),
"test1.domain.\t100.101.102.103\ntest2.sub.domain.\t100.99.9.1\n",
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
got := tt.dmap.Pretty()
if tt.want != got {
t.Errorf("want %v; got %v", tt.want, got)
}
})
}
}
func TestPrettyDiffFrom(t *testing.T) {
tests := []struct {
name string
map1 *Map
map2 *Map
want string
}{
{
"from_empty",
nil,
NewMap(map[string]netaddr.IP{
"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
}, nil),
"+test1.ipn.dev.\t100.101.102.103\n+test2.ipn.dev.\t100.103.102.101\n",
},
{
"equal",
NewMap(map[string]netaddr.IP{
"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
}, nil),
NewMap(map[string]netaddr.IP{
"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
}, nil),
"",
},
{
"changed_ip",
NewMap(map[string]netaddr.IP{
"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
}, nil),
NewMap(map[string]netaddr.IP{
"test2.ipn.dev.": netaddr.IPv4(100, 104, 102, 101),
"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
}, nil),
"-test2.ipn.dev.\t100.103.102.101\n+test2.ipn.dev.\t100.104.102.101\n",
},
{
"new_domain",
NewMap(map[string]netaddr.IP{
"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
}, nil),
NewMap(map[string]netaddr.IP{
"test3.ipn.dev.": netaddr.IPv4(100, 105, 106, 107),
"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
}, nil),
"+test3.ipn.dev.\t100.105.106.107\n",
},
{
"gone_domain",
NewMap(map[string]netaddr.IP{
"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
}, nil),
NewMap(map[string]netaddr.IP{
"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
}, nil),
"-test2.ipn.dev.\t100.103.102.101\n",
},
{
"mixed",
NewMap(map[string]netaddr.IP{
"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
"test4.ipn.dev.": netaddr.IPv4(100, 107, 106, 105),
"test5.ipn.dev.": netaddr.IPv4(100, 64, 1, 1),
"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
}, nil),
NewMap(map[string]netaddr.IP{
"test2.ipn.dev.": netaddr.IPv4(100, 104, 102, 101),
"test1.ipn.dev.": netaddr.IPv4(100, 100, 101, 102),
"test3.ipn.dev.": netaddr.IPv4(100, 64, 1, 1),
}, nil),
"-test1.ipn.dev.\t100.101.102.103\n+test1.ipn.dev.\t100.100.101.102\n" +
"-test2.ipn.dev.\t100.103.102.101\n+test2.ipn.dev.\t100.104.102.101\n" +
"+test3.ipn.dev.\t100.64.1.1\n-test4.ipn.dev.\t100.107.106.105\n-test5.ipn.dev.\t100.64.1.1\n",
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
got := tt.map2.PrettyDiffFrom(tt.map1)
if tt.want != got {
t.Errorf("want %v; got %v", tt.want, got)
}
})
}
t.Run("truncated", func(t *testing.T) {
small := NewMap(nil, nil)
m := map[string]netaddr.IP{}
for i := 0; i < 5000; i++ {
m[fmt.Sprintf("host%d.ipn.dev.", i)] = netaddr.IPv4(100, 64, 1, 1)
}
veryBig := NewMap(m, nil)
diff := veryBig.PrettyDiffFrom(small)
if len(diff) > 3<<10 {
t.Errorf("pretty diff too large: %d bytes", len(diff))
}
if !strings.Contains(diff, "truncated") {
t.Errorf("big diff not truncated")
}
})
}

25
net/dns/neterr_darwin.go Normal file
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// Copyright (c) 2020 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 dns
import (
"errors"
"syscall"
)
// Avoid allocation when calling errors.Is below
// by converting syscall.Errno to error here.
var (
networkDown error = syscall.ENETDOWN
networkUnreachable error = syscall.ENETUNREACH
)
func networkIsDown(err error) bool {
return errors.Is(err, networkDown)
}
func networkIsUnreachable(err error) bool {
return errors.Is(err, networkUnreachable)
}

10
net/dns/neterr_other.go Normal file
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// Copyright (c) 2020 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.
// +build !darwin,!windows
package dns
func networkIsDown(err error) bool { return false }
func networkIsUnreachable(err error) bool { return false }

29
net/dns/neterr_windows.go Normal file
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// Copyright (c) 2020 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 dns
import (
"net"
"os"
"golang.org/x/sys/windows"
)
func networkIsDown(err error) bool {
if oe, ok := err.(*net.OpError); ok && oe.Op == "write" {
if se, ok := oe.Err.(*os.SyscallError); ok {
if se.Syscall == "wsasendto" && se.Err == windows.WSAENETUNREACH {
return true
}
}
}
return false
}
func networkIsUnreachable(err error) bool {
// TODO(bradfitz,josharian): something here? what is the
// difference between down and unreachable? Add comments.
return false
}

662
net/dns/tsdns.go Normal file
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// Copyright (c) 2020 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 dns provides a Resolver capable of resolving
// domains on a Tailscale network.
package dns
import (
"encoding/hex"
"errors"
"net"
"strings"
"sync"
"time"
dns "golang.org/x/net/dns/dnsmessage"
"inet.af/netaddr"
"tailscale.com/net/interfaces"
"tailscale.com/types/logger"
"tailscale.com/util/dnsname"
"tailscale.com/wgengine/monitor"
)
// maxResponseBytes is the maximum size of a response from a Resolver.
const maxResponseBytes = 512
// queueSize is the maximal number of DNS requests that can await polling.
// If EnqueueRequest is called when this many requests are already pending,
// the request will be dropped to avoid blocking the caller.
const queueSize = 64
// defaultTTL is the TTL of all responses from Resolver.
const defaultTTL = 600 * time.Second
// ErrClosed indicates that the resolver has been closed and readers should exit.
var ErrClosed = errors.New("closed")
var (
errFullQueue = errors.New("request queue full")
errMapNotSet = errors.New("domain map not set")
errNotForwarding = errors.New("forwarding disabled")
errNotImplemented = errors.New("query type not implemented")
errNotQuery = errors.New("not a DNS query")
errNotOurName = errors.New("not a Tailscale DNS name")
)
// Packet represents a DNS payload together with the address of its origin.
type Packet struct {
// Payload is the application layer DNS payload.
// Resolver assumes ownership of the request payload when it is enqueued
// and cedes ownership of the response payload when it is returned from NextResponse.
Payload []byte
// Addr is the source address for a request and the destination address for a response.
Addr netaddr.IPPort
}
// Resolver is a DNS resolver for nodes on the Tailscale network,
// associating them with domain names of the form <mynode>.<mydomain>.<root>.
// If it is asked to resolve a domain that is not of that form,
// it delegates to upstream nameservers if any are set.
type Resolver struct {
logf logger.Logf
linkMon *monitor.Mon // or nil
unregLinkMon func() // or nil
// forwarder forwards requests to upstream nameservers.
forwarder *forwarder
// queue is a buffered channel holding DNS requests queued for resolution.
queue chan Packet
// responses is an unbuffered channel to which responses are returned.
responses chan Packet
// errors is an unbuffered channel to which errors are returned.
errors chan error
// closed signals all goroutines to stop.
closed chan struct{}
// wg signals when all goroutines have stopped.
wg sync.WaitGroup
// mu guards the following fields from being updated while used.
mu sync.Mutex
// dnsMap is the map most recently received from the control server.
dnsMap *Map
}
// ResolverConfig is the set of configuration options for a Resolver.
type ResolverConfig struct {
// Logf is the logger to use throughout the Resolver.
Logf logger.Logf
// Forward determines whether the resolver will forward packets to
// nameservers set with SetUpstreams if the domain name is not of a Tailscale node.
Forward bool
// LinkMonitor optionally provides a link monitor to use to rebind
// connections on link changes.
// If nil, rebinds are not performend.
LinkMonitor *monitor.Mon
}
// NewResolver constructs a resolver associated with the given root domain.
// The root domain must be in canonical form (with a trailing period).
func NewResolver(config ResolverConfig) *Resolver {
r := &Resolver{
logf: logger.WithPrefix(config.Logf, "dns: "),
linkMon: config.LinkMonitor,
queue: make(chan Packet, queueSize),
responses: make(chan Packet),
errors: make(chan error),
closed: make(chan struct{}),
}
if config.Forward {
r.forwarder = newForwarder(r.logf, r.responses)
}
if r.linkMon != nil {
r.unregLinkMon = r.linkMon.RegisterChangeCallback(r.onLinkMonitorChange)
}
return r
}
func (r *Resolver) Start() error {
if r.forwarder != nil {
if err := r.forwarder.Start(); err != nil {
return err
}
}
r.wg.Add(1)
go r.poll()
return nil
}
// Close shuts down the resolver and ensures poll goroutines have exited.
// The Resolver cannot be used again after Close is called.
func (r *Resolver) Close() {
select {
case <-r.closed:
return
default:
// continue
}
close(r.closed)
if r.unregLinkMon != nil {
r.unregLinkMon()
}
if r.forwarder != nil {
r.forwarder.Close()
}
r.wg.Wait()
}
func (r *Resolver) onLinkMonitorChange(changed bool, state *interfaces.State) {
if !changed {
return
}
if r.forwarder != nil {
r.forwarder.rebindFromNetworkChange()
}
}
// SetMap sets the resolver's DNS map, taking ownership of it.
func (r *Resolver) SetMap(m *Map) {
r.mu.Lock()
oldMap := r.dnsMap
r.dnsMap = m
r.mu.Unlock()
r.logf("map diff:\n%s", m.PrettyDiffFrom(oldMap))
}
// SetUpstreams sets the addresses of the resolver's
// upstream nameservers, taking ownership of the argument.
func (r *Resolver) SetUpstreams(upstreams []net.Addr) {
if r.forwarder != nil {
r.forwarder.setUpstreams(upstreams)
}
r.logf("set upstreams: %v", upstreams)
}
// EnqueueRequest places the given DNS request in the resolver's queue.
// It takes ownership of the payload and does not block.
// If the queue is full, the request will be dropped and an error will be returned.
func (r *Resolver) EnqueueRequest(request Packet) error {
select {
case <-r.closed:
return ErrClosed
case r.queue <- request:
return nil
default:
return errFullQueue
}
}
// NextResponse returns a DNS response to a previously enqueued request.
// It blocks until a response is available and gives up ownership of the response payload.
func (r *Resolver) NextResponse() (Packet, error) {
select {
case <-r.closed:
return Packet{}, ErrClosed
case resp := <-r.responses:
return resp, nil
case err := <-r.errors:
return Packet{}, err
}
}
// Resolve maps a given domain name to the IP address of the host that owns it,
// if the IP address conforms to the DNS resource type given by tp (one of A, AAAA, ALL).
// The domain name must be in canonical form (with a trailing period).
func (r *Resolver) Resolve(domain string, tp dns.Type) (netaddr.IP, dns.RCode, error) {
r.mu.Lock()
dnsMap := r.dnsMap
r.mu.Unlock()
if dnsMap == nil {
return netaddr.IP{}, dns.RCodeServerFailure, errMapNotSet
}
// Reject .onion domains per RFC 7686.
if dnsname.HasSuffix(domain, ".onion") {
return netaddr.IP{}, dns.RCodeNameError, nil
}
anyHasSuffix := false
for _, suffix := range dnsMap.rootDomains {
if dnsname.HasSuffix(domain, suffix) {
anyHasSuffix = true
break
}
}
addr, found := dnsMap.nameToIP[domain]
if !found {
if !anyHasSuffix {
return netaddr.IP{}, dns.RCodeRefused, nil
}
return netaddr.IP{}, dns.RCodeNameError, nil
}
// Refactoring note: this must happen after we check suffixes,
// otherwise we will respond with NOTIMP to requests that should be forwarded.
switch tp {
case dns.TypeA:
if !addr.Is4() {
return netaddr.IP{}, dns.RCodeSuccess, nil
}
return addr, dns.RCodeSuccess, nil
case dns.TypeAAAA:
if !addr.Is6() {
return netaddr.IP{}, dns.RCodeSuccess, nil
}
return addr, dns.RCodeSuccess, nil
case dns.TypeALL:
// Answer with whatever we've got.
// It could be IPv4, IPv6, or a zero addr.
// TODO: Return all available resolutions (A and AAAA, if we have them).
return addr, dns.RCodeSuccess, nil
// Leave some some record types explicitly unimplemented.
// These types relate to recursive resolution or special
// DNS sematics and might be implemented in the future.
case dns.TypeNS, dns.TypeSOA, dns.TypeAXFR, dns.TypeHINFO:
return netaddr.IP{}, dns.RCodeNotImplemented, errNotImplemented
// For everything except for the few types above that are explictly not implemented, return no records.
// This is what other DNS systems do: always return NOERROR
// without any records whenever the requested record type is unknown.
// You can try this with:
// dig -t TYPE9824 example.com
// and note that NOERROR is returned, despite that record type being made up.
default:
// no records exist of this type
return netaddr.IP{}, dns.RCodeSuccess, nil
}
}
// ResolveReverse returns the unique domain name that maps to the given address.
// The returned domain name is in canonical form (with a trailing period).
func (r *Resolver) ResolveReverse(ip netaddr.IP) (string, dns.RCode, error) {
r.mu.Lock()
dnsMap := r.dnsMap
r.mu.Unlock()
if dnsMap == nil {
return "", dns.RCodeServerFailure, errMapNotSet
}
name, found := dnsMap.ipToName[ip]
if !found {
return "", dns.RCodeNameError, nil
}
return name, dns.RCodeSuccess, nil
}
func (r *Resolver) poll() {
defer r.wg.Done()
var packet Packet
for {
select {
case <-r.closed:
return
case packet = <-r.queue:
// continue
}
out, err := r.respond(packet.Payload)
if err == errNotOurName {
if r.forwarder != nil {
err = r.forwarder.forward(packet)
if err == nil {
// forward will send response into r.responses, nothing to do.
continue
}
} else {
err = errNotForwarding
}
}
if err != nil {
select {
case <-r.closed:
return
case r.errors <- err:
// continue
}
} else {
packet.Payload = out
select {
case <-r.closed:
return
case r.responses <- packet:
// continue
}
}
}
}
type response struct {
Header dns.Header
Question dns.Question
// Name is the response to a PTR query.
Name string
// IP is the response to an A, AAAA, or ALL query.
IP netaddr.IP
}
// parseQuery parses the query in given packet into a response struct.
func parseQuery(query []byte, resp *response) error {
var parser dns.Parser
var err error
resp.Header, err = parser.Start(query)
if err != nil {
return err
}
if resp.Header.Response {
return errNotQuery
}
resp.Question, err = parser.Question()
if err != nil {
return err
}
return nil
}
// marshalARecord serializes an A record into an active builder.
// The caller may continue using the builder following the call.
func marshalARecord(name dns.Name, ip netaddr.IP, builder *dns.Builder) error {
var answer dns.AResource
answerHeader := dns.ResourceHeader{
Name: name,
Type: dns.TypeA,
Class: dns.ClassINET,
TTL: uint32(defaultTTL / time.Second),
}
ipbytes := ip.As4()
copy(answer.A[:], ipbytes[:])
return builder.AResource(answerHeader, answer)
}
// marshalAAAARecord serializes an AAAA record into an active builder.
// The caller may continue using the builder following the call.
func marshalAAAARecord(name dns.Name, ip netaddr.IP, builder *dns.Builder) error {
var answer dns.AAAAResource
answerHeader := dns.ResourceHeader{
Name: name,
Type: dns.TypeAAAA,
Class: dns.ClassINET,
TTL: uint32(defaultTTL / time.Second),
}
ipbytes := ip.As16()
copy(answer.AAAA[:], ipbytes[:])
return builder.AAAAResource(answerHeader, answer)
}
// marshalPTRRecord serializes a PTR record into an active builder.
// The caller may continue using the builder following the call.
func marshalPTRRecord(queryName dns.Name, name string, builder *dns.Builder) error {
var answer dns.PTRResource
var err error
answerHeader := dns.ResourceHeader{
Name: queryName,
Type: dns.TypePTR,
Class: dns.ClassINET,
TTL: uint32(defaultTTL / time.Second),
}
answer.PTR, err = dns.NewName(name)
if err != nil {
return err
}
return builder.PTRResource(answerHeader, answer)
}
// marshalResponse serializes the DNS response into a new buffer.
func marshalResponse(resp *response) ([]byte, error) {
resp.Header.Response = true
resp.Header.Authoritative = true
if resp.Header.RecursionDesired {
resp.Header.RecursionAvailable = true
}
builder := dns.NewBuilder(nil, resp.Header)
isSuccess := resp.Header.RCode == dns.RCodeSuccess
if resp.Question.Type != 0 || isSuccess {
err := builder.StartQuestions()
if err != nil {
return nil, err
}
err = builder.Question(resp.Question)
if err != nil {
return nil, err
}
}
// Only successful responses contain answers.
if !isSuccess {
return builder.Finish()
}
err := builder.StartAnswers()
if err != nil {
return nil, err
}
switch resp.Question.Type {
case dns.TypeA, dns.TypeAAAA, dns.TypeALL:
if resp.IP.Is4() {
err = marshalARecord(resp.Question.Name, resp.IP, &builder)
} else if resp.IP.Is6() {
err = marshalAAAARecord(resp.Question.Name, resp.IP, &builder)
}
case dns.TypePTR:
err = marshalPTRRecord(resp.Question.Name, resp.Name, &builder)
}
if err != nil {
return nil, err
}
return builder.Finish()
}
const (
rdnsv4Suffix = ".in-addr.arpa."
rdnsv6Suffix = ".ip6.arpa."
)
// hasRDNSBonjourPrefix reports whether name has a Bonjour Service Prefix..
//
// https://tools.ietf.org/html/rfc6763 lists
// "five special RR names" for Bonjour service discovery:
//
// b._dns-sd._udp.<domain>.
// db._dns-sd._udp.<domain>.
// r._dns-sd._udp.<domain>.
// dr._dns-sd._udp.<domain>.
// lb._dns-sd._udp.<domain>.
func hasRDNSBonjourPrefix(s string) bool {
// Even the shortest name containing a Bonjour prefix is long,
// so check length (cheap) and bail early if possible.
if len(s) < len("*._dns-sd._udp.0.0.0.0.in-addr.arpa.") {
return false
}
dot := strings.IndexByte(s, '.')
if dot == -1 {
return false // shouldn't happen
}
switch s[:dot] {
case "b", "db", "r", "dr", "lb":
default:
return false
}
return strings.HasPrefix(s[dot:], "._dns-sd._udp.")
}
// rawNameToLower converts a raw DNS name to a string, lowercasing it.
func rawNameToLower(name []byte) string {
var sb strings.Builder
sb.Grow(len(name))
for _, b := range name {
if 'A' <= b && b <= 'Z' {
b = b - 'A' + 'a'
}
sb.WriteByte(b)
}
return sb.String()
}
// ptrNameToIPv4 transforms a PTR name representing an IPv4 address to said address.
// Such names are IPv4 labels in reverse order followed by .in-addr.arpa.
// For example,
// 4.3.2.1.in-addr.arpa
// is transformed to
// 1.2.3.4
func rdnsNameToIPv4(name string) (ip netaddr.IP, ok bool) {
name = strings.TrimSuffix(name, rdnsv4Suffix)
ip, err := netaddr.ParseIP(string(name))
if err != nil {
return netaddr.IP{}, false
}
if !ip.Is4() {
return netaddr.IP{}, false
}
b := ip.As4()
return netaddr.IPv4(b[3], b[2], b[1], b[0]), true
}
// ptrNameToIPv6 transforms a PTR name representing an IPv6 address to said address.
// Such names are dot-separated nibbles in reverse order followed by .ip6.arpa.
// For example,
// b.a.9.8.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.
// is transformed to
// 2001:db8::567:89ab
func rdnsNameToIPv6(name string) (ip netaddr.IP, ok bool) {
var b [32]byte
var ipb [16]byte
name = strings.TrimSuffix(name, rdnsv6Suffix)
// 32 nibbles and 31 dots between them.
if len(name) != 63 {
return netaddr.IP{}, false
}
// Dots and hex digits alternate.
prevDot := true
// i ranges over name backward; j ranges over b forward.
for i, j := len(name)-1, 0; i >= 0; i-- {
thisDot := (name[i] == '.')
if prevDot == thisDot {
return netaddr.IP{}, false
}
prevDot = thisDot
if !thisDot {
// This is safe assuming alternation.
// We do not check that non-dots are hex digits: hex.Decode below will do that.
b[j] = name[i]
j++
}
}
_, err := hex.Decode(ipb[:], b[:])
if err != nil {
return netaddr.IP{}, false
}
return netaddr.IPFrom16(ipb), true
}
// respondReverse returns a DNS response to a PTR query.
// It is assumed that resp.Question is populated by respond before this is called.
func (r *Resolver) respondReverse(query []byte, name string, resp *response) ([]byte, error) {
if hasRDNSBonjourPrefix(name) {
return nil, errNotOurName
}
var ip netaddr.IP
var ok bool
switch {
case strings.HasSuffix(name, rdnsv4Suffix):
ip, ok = rdnsNameToIPv4(name)
case strings.HasSuffix(name, rdnsv6Suffix):
ip, ok = rdnsNameToIPv6(name)
default:
return nil, errNotOurName
}
// It is more likely that we failed in parsing the name than that it is actually malformed.
// To avoid frustrating users, just log and delegate.
if !ok {
r.logf("parsing rdns: malformed name: %s", name)
return nil, errNotOurName
}
var err error
resp.Name, resp.Header.RCode, err = r.ResolveReverse(ip)
if err != nil {
r.logf("resolving rdns: %v", ip, err)
}
if resp.Header.RCode == dns.RCodeNameError {
return nil, errNotOurName
}
return marshalResponse(resp)
}
// respond returns a DNS response to query if it can be resolved locally.
// Otherwise, it returns errNotOurName.
func (r *Resolver) respond(query []byte) ([]byte, error) {
resp := new(response)
// ParseQuery is sufficiently fast to run on every DNS packet.
// This is considerably simpler than extracting the name by hand
// to shave off microseconds in case of delegation.
err := parseQuery(query, resp)
// We will not return this error: it is the sender's fault.
if err != nil {
if errors.Is(err, dns.ErrSectionDone) {
r.logf("parseQuery(%02x): no DNS questions", query)
} else {
r.logf("parseQuery(%02x): %v", query, err)
}
resp.Header.RCode = dns.RCodeFormatError
return marshalResponse(resp)
}
rawName := resp.Question.Name.Data[:resp.Question.Name.Length]
name := rawNameToLower(rawName)
// Always try to handle reverse lookups; delegate inside when not found.
// This way, queries for existent nodes do not leak,
// but we behave gracefully if non-Tailscale nodes exist in CGNATRange.
if resp.Question.Type == dns.TypePTR {
return r.respondReverse(query, name, resp)
}
resp.IP, resp.Header.RCode, err = r.Resolve(name, resp.Question.Type)
// This return code is special: it requests forwarding.
if resp.Header.RCode == dns.RCodeRefused {
return nil, errNotOurName
}
// We will not return this error: it is the sender's fault.
if err != nil {
r.logf("resolving: %v", err)
}
return marshalResponse(resp)
}

95
net/dns/tsdns_server_test.go Normal file
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// Copyright (c) 2020 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 dns
import (
"log"
"testing"
"github.com/miekg/dns"
"inet.af/netaddr"
)
// This file exists to isolate the test infrastructure
// that depends on github.com/miekg/dns
// from the rest, which only depends on dnsmessage.
var dnsHandleFunc = dns.HandleFunc
// resolveToIP returns a handler function which responds
// to queries of type A it receives with an A record containing ipv4,
// to queries of type AAAA with an AAAA record containing ipv6,
// to queries of type NS with an NS record containg name.
func resolveToIP(ipv4, ipv6 netaddr.IP, ns string) dns.HandlerFunc {
return func(w dns.ResponseWriter, req *dns.Msg) {
m := new(dns.Msg)
m.SetReply(req)
if len(req.Question) != 1 {
panic("not a single-question request")
}
question := req.Question[0]
var ans dns.RR
switch question.Qtype {
case dns.TypeA:
ans = &dns.A{
Hdr: dns.RR_Header{
Name: question.Name,
Rrtype: dns.TypeA,
Class: dns.ClassINET,
},
A: ipv4.IPAddr().IP,
}
case dns.TypeAAAA:
ans = &dns.AAAA{
Hdr: dns.RR_Header{
Name: question.Name,
Rrtype: dns.TypeAAAA,
Class: dns.ClassINET,
},
AAAA: ipv6.IPAddr().IP,
}
case dns.TypeNS:
ans = &dns.NS{
Hdr: dns.RR_Header{
Name: question.Name,
Rrtype: dns.TypeNS,
Class: dns.ClassINET,
},
Ns: ns,
}
}
m.Answer = append(m.Answer, ans)
w.WriteMsg(m)
}
}
func resolveToNXDOMAIN(w dns.ResponseWriter, req *dns.Msg) {
m := new(dns.Msg)
m.SetRcode(req, dns.RcodeNameError)
w.WriteMsg(m)
}
func serveDNS(tb testing.TB, addr string) (*dns.Server, chan error) {
server := &dns.Server{Addr: addr, Net: "udp"}
waitch := make(chan struct{})
server.NotifyStartedFunc = func() { close(waitch) }
errch := make(chan error, 1)
go func() {
err := server.ListenAndServe()
if err != nil {
log.Printf("ListenAndServe(%q): %v", addr, err)
}
errch <- err
close(errch)
}()
<-waitch
return server, errch
}

816
net/dns/tsdns_test.go Normal file
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// Copyright (c) 2020 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 dns
import (
"bytes"
"errors"
"net"
"sync"
"testing"
dns "golang.org/x/net/dns/dnsmessage"
"inet.af/netaddr"
"tailscale.com/tstest"
)
var testipv4 = netaddr.IPv4(1, 2, 3, 4)
var testipv6 = netaddr.IPv6Raw([16]byte{
0x00, 0x01, 0x02, 0x03,
0x04, 0x05, 0x06, 0x07,
0x08, 0x09, 0x0a, 0x0b,
0x0c, 0x0d, 0x0e, 0x0f,
})
var dnsMap = NewMap(
map[string]netaddr.IP{
"test1.ipn.dev.": testipv4,
"test2.ipn.dev.": testipv6,
},
[]string{"ipn.dev."},
)
func dnspacket(domain string, tp dns.Type) []byte {
var dnsHeader dns.Header
question := dns.Question{
Name: dns.MustNewName(domain),
Type: tp,
Class: dns.ClassINET,
}
builder := dns.NewBuilder(nil, dnsHeader)
builder.StartQuestions()
builder.Question(question)
payload, _ := builder.Finish()
return payload
}
type dnsResponse struct {
ip netaddr.IP
name string
rcode dns.RCode
}
func unpackResponse(payload []byte) (dnsResponse, error) {
var response dnsResponse
var parser dns.Parser
h, err := parser.Start(payload)
if err != nil {
return response, err
}
if !h.Response {
return response, errors.New("not a response")
}
response.rcode = h.RCode
if response.rcode != dns.RCodeSuccess {
return response, nil
}
err = parser.SkipAllQuestions()
if err != nil {
return response, err
}
ah, err := parser.AnswerHeader()
if err != nil {
return response, err
}
switch ah.Type {
case dns.TypeA:
res, err := parser.AResource()
if err != nil {
return response, err
}
response.ip = netaddr.IPv4(res.A[0], res.A[1], res.A[2], res.A[3])
case dns.TypeAAAA:
res, err := parser.AAAAResource()
if err != nil {
return response, err
}
response.ip = netaddr.IPv6Raw(res.AAAA)
case dns.TypeNS:
res, err := parser.NSResource()
if err != nil {
return response, err
}
response.name = res.NS.String()
default:
return response, errors.New("type not in {A, AAAA, NS}")
}
return response, nil
}
func syncRespond(r *Resolver, query []byte) ([]byte, error) {
request := Packet{Payload: query}
r.EnqueueRequest(request)
resp, err := r.NextResponse()
return resp.Payload, err
}
func mustIP(str string) netaddr.IP {
ip, err := netaddr.ParseIP(str)
if err != nil {
panic(err)
}
return ip
}
func TestRDNSNameToIPv4(t *testing.T) {
tests := []struct {
name string
input string
wantIP netaddr.IP
wantOK bool
}{
{"valid", "4.123.24.1.in-addr.arpa.", netaddr.IPv4(1, 24, 123, 4), true},
{"double_dot", "1..2.3.in-addr.arpa.", netaddr.IP{}, false},
{"overflow", "1.256.3.4.in-addr.arpa.", netaddr.IP{}, false},
{"not_ip", "sub.do.ma.in.in-addr.arpa.", netaddr.IP{}, false},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
ip, ok := rdnsNameToIPv4(tt.input)
if ok != tt.wantOK {
t.Errorf("ok = %v; want %v", ok, tt.wantOK)
} else if ok && ip != tt.wantIP {
t.Errorf("ip = %v; want %v", ip, tt.wantIP)
}
})
}
}
func TestRDNSNameToIPv6(t *testing.T) {
tests := []struct {
name string
input string
wantIP netaddr.IP
wantOK bool
}{
{
"valid",
"b.a.9.8.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.",
mustIP("2001:db8::567:89ab"),
true,
},
{
"double_dot",
"b..9.8.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.",
netaddr.IP{},
false,
},
{
"double_hex",
"b.a.98.0.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.",
netaddr.IP{},
false,
},
{
"not_hex",
"b.a.g.0.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.",
netaddr.IP{},
false,
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
ip, ok := rdnsNameToIPv6(tt.input)
if ok != tt.wantOK {
t.Errorf("ok = %v; want %v", ok, tt.wantOK)
} else if ok && ip != tt.wantIP {
t.Errorf("ip = %v; want %v", ip, tt.wantIP)
}
})
}
}
func TestResolve(t *testing.T) {
r := NewResolver(ResolverConfig{Logf: t.Logf, Forward: false})
r.SetMap(dnsMap)
if err := r.Start(); err != nil {
t.Fatalf("start: %v", err)
}
defer r.Close()
tests := []struct {
name string
qname string
qtype dns.Type
ip netaddr.IP
code dns.RCode
}{
{"ipv4", "test1.ipn.dev.", dns.TypeA, testipv4, dns.RCodeSuccess},
{"ipv6", "test2.ipn.dev.", dns.TypeAAAA, testipv6, dns.RCodeSuccess},
{"no-ipv6", "test1.ipn.dev.", dns.TypeAAAA, netaddr.IP{}, dns.RCodeSuccess},
{"nxdomain", "test3.ipn.dev.", dns.TypeA, netaddr.IP{}, dns.RCodeNameError},
{"foreign domain", "google.com.", dns.TypeA, netaddr.IP{}, dns.RCodeRefused},
{"all", "test1.ipn.dev.", dns.TypeA, testipv4, dns.RCodeSuccess},
{"mx-ipv4", "test1.ipn.dev.", dns.TypeMX, netaddr.IP{}, dns.RCodeSuccess},
{"mx-ipv6", "test2.ipn.dev.", dns.TypeMX, netaddr.IP{}, dns.RCodeSuccess},
{"mx-nxdomain", "test3.ipn.dev.", dns.TypeMX, netaddr.IP{}, dns.RCodeNameError},
{"ns-nxdomain", "test3.ipn.dev.", dns.TypeNS, netaddr.IP{}, dns.RCodeNameError},
{"onion-domain", "footest.onion.", dns.TypeA, netaddr.IP{}, dns.RCodeNameError},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
ip, code, err := r.Resolve(tt.qname, tt.qtype)
if err != nil {
t.Errorf("err = %v; want nil", err)
}
if code != tt.code {
t.Errorf("code = %v; want %v", code, tt.code)
}
// Only check ip for non-err
if ip != tt.ip {
t.Errorf("ip = %v; want %v", ip, tt.ip)
}
})
}
}
func TestResolveReverse(t *testing.T) {
r := NewResolver(ResolverConfig{Logf: t.Logf, Forward: false})
r.SetMap(dnsMap)
if err := r.Start(); err != nil {
t.Fatalf("start: %v", err)
}
defer r.Close()
tests := []struct {
name string
ip netaddr.IP
want string
code dns.RCode
}{
{"ipv4", testipv4, "test1.ipn.dev.", dns.RCodeSuccess},
{"ipv6", testipv6, "test2.ipn.dev.", dns.RCodeSuccess},
{"nxdomain", netaddr.IPv4(4, 3, 2, 1), "", dns.RCodeNameError},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
name, code, err := r.ResolveReverse(tt.ip)
if err != nil {
t.Errorf("err = %v; want nil", err)
}
if code != tt.code {
t.Errorf("code = %v; want %v", code, tt.code)
}
if name != tt.want {
t.Errorf("ip = %v; want %v", name, tt.want)
}
})
}
}
func ipv6Works() bool {
c, err := net.Listen("tcp", "[::1]:0")
if err != nil {
return false
}
c.Close()
return true
}
func TestDelegate(t *testing.T) {
tstest.ResourceCheck(t)
if !ipv6Works() {
t.Skip("skipping test that requires localhost IPv6")
}
dnsHandleFunc("test.site.", resolveToIP(testipv4, testipv6, "dns.test.site."))
dnsHandleFunc("nxdomain.site.", resolveToNXDOMAIN)
v4server, v4errch := serveDNS(t, "127.0.0.1:0")
v6server, v6errch := serveDNS(t, "[::1]:0")
defer func() {
if err := <-v4errch; err != nil {
t.Errorf("v4 server error: %v", err)
}
if err := <-v6errch; err != nil {
t.Errorf("v6 server error: %v", err)
}
}()
if v4server != nil {
defer v4server.Shutdown()
}
if v6server != nil {
defer v6server.Shutdown()
}
if v4server == nil || v6server == nil {
// There is an error in at least one of the channels
// and we cannot proceed; return to see it.
return
}
r := NewResolver(ResolverConfig{Logf: t.Logf, Forward: true})
r.SetMap(dnsMap)
r.SetUpstreams([]net.Addr{
v4server.PacketConn.LocalAddr(),
v6server.PacketConn.LocalAddr(),
})
if err := r.Start(); err != nil {
t.Fatalf("start: %v", err)
}
defer r.Close()
tests := []struct {
title string
query []byte
response dnsResponse
}{
{
"ipv4",
dnspacket("test.site.", dns.TypeA),
dnsResponse{ip: testipv4, rcode: dns.RCodeSuccess},
},
{
"ipv6",
dnspacket("test.site.", dns.TypeAAAA),
dnsResponse{ip: testipv6, rcode: dns.RCodeSuccess},
},
{
"ns",
dnspacket("test.site.", dns.TypeNS),
dnsResponse{name: "dns.test.site.", rcode: dns.RCodeSuccess},
},
{
"nxdomain",
dnspacket("nxdomain.site.", dns.TypeA),
dnsResponse{rcode: dns.RCodeNameError},
},
}
for _, tt := range tests {
t.Run(tt.title, func(t *testing.T) {
payload, err := syncRespond(r, tt.query)
if err != nil {
t.Errorf("err = %v; want nil", err)
return
}
response, err := unpackResponse(payload)
if err != nil {
t.Errorf("extract: err = %v; want nil (in %x)", err, payload)
return
}
if response.rcode != tt.response.rcode {
t.Errorf("rcode = %v; want %v", response.rcode, tt.response.rcode)
}
if response.ip != tt.response.ip {
t.Errorf("ip = %v; want %v", response.ip, tt.response.ip)
}
if response.name != tt.response.name {
t.Errorf("name = %v; want %v", response.name, tt.response.name)
}
})
}
}
func TestDelegateCollision(t *testing.T) {
dnsHandleFunc("test.site.", resolveToIP(testipv4, testipv6, "dns.test.site."))
server, errch := serveDNS(t, "127.0.0.1:0")
defer func() {
if err := <-errch; err != nil {
t.Errorf("server error: %v", err)
}
}()
if server == nil {
return
}
defer server.Shutdown()
r := NewResolver(ResolverConfig{Logf: t.Logf, Forward: true})
r.SetMap(dnsMap)
r.SetUpstreams([]net.Addr{server.PacketConn.LocalAddr()})
if err := r.Start(); err != nil {
t.Fatalf("start: %v", err)
}
defer r.Close()
packets := []struct {
qname string
qtype dns.Type
addr netaddr.IPPort
}{
{"test.site.", dns.TypeA, netaddr.IPPort{IP: netaddr.IPv4(1, 1, 1, 1), Port: 1001}},
{"test.site.", dns.TypeAAAA, netaddr.IPPort{IP: netaddr.IPv4(1, 1, 1, 1), Port: 1002}},
}
// packets will have the same dns txid.
for _, p := range packets {
payload := dnspacket(p.qname, p.qtype)
req := Packet{Payload: payload, Addr: p.addr}
err := r.EnqueueRequest(req)
if err != nil {
t.Error(err)
}
}
// Despite the txid collision, the answer(s) should still match the query.
resp, err := r.NextResponse()
if err != nil {
t.Error(err)
}
var p dns.Parser
_, err = p.Start(resp.Payload)
if err != nil {
t.Error(err)
}
err = p.SkipAllQuestions()
if err != nil {
t.Error(err)
}
ans, err := p.AllAnswers()
if err != nil {
t.Error(err)
}
var wantType dns.Type
switch ans[0].Body.(type) {
case *dns.AResource:
wantType = dns.TypeA
case *dns.AAAAResource:
wantType = dns.TypeAAAA
default:
t.Errorf("unexpected answer type: %T", ans[0].Body)
}
for _, p := range packets {
if p.qtype == wantType && p.addr != resp.Addr {
t.Errorf("addr = %v; want %v", resp.Addr, p.addr)
}
}
}
func TestConcurrentSetMap(t *testing.T) {
r := NewResolver(ResolverConfig{Logf: t.Logf, Forward: false})
if err := r.Start(); err != nil {
t.Fatalf("start: %v", err)
}
defer r.Close()
// This is purely to ensure that Resolve does not race with SetMap.
var wg sync.WaitGroup
wg.Add(2)
go func() {
defer wg.Done()
r.SetMap(dnsMap)
}()
go func() {
defer wg.Done()
r.Resolve("test1.ipn.dev", dns.TypeA)
}()
wg.Wait()
}
func TestConcurrentSetUpstreams(t *testing.T) {
dnsHandleFunc("test.site.", resolveToIP(testipv4, testipv6, "dns.test.site."))
server, errch := serveDNS(t, "127.0.0.1:0")
defer func() {
if err := <-errch; err != nil {
t.Errorf("server error: %v", err)
}
}()
if server == nil {
return
}
defer server.Shutdown()
r := NewResolver(ResolverConfig{Logf: t.Logf, Forward: true})
r.SetMap(dnsMap)
if err := r.Start(); err != nil {
t.Fatalf("start: %v", err)
}
defer r.Close()
packet := dnspacket("test.site.", dns.TypeA)
// This is purely to ensure that delegation does not race with SetUpstreams.
var wg sync.WaitGroup
wg.Add(2)
go func() {
defer wg.Done()
r.SetUpstreams([]net.Addr{server.PacketConn.LocalAddr()})
}()
go func() {
defer wg.Done()
syncRespond(r, packet)
}()
wg.Wait()
}
var allResponse = []byte{
0x00, 0x00, // transaction id: 0
0x84, 0x00, // flags: response, authoritative, no error
0x00, 0x01, // one question
0x00, 0x01, // one answer
0x00, 0x00, 0x00, 0x00, // no authority or additional RRs
// Question:
0x05, 0x74, 0x65, 0x73, 0x74, 0x31, 0x03, 0x69, 0x70, 0x6e, 0x03, 0x64, 0x65, 0x76, 0x00, // name
0x00, 0xff, 0x00, 0x01, // type ALL, class IN
// Answer:
0x05, 0x74, 0x65, 0x73, 0x74, 0x31, 0x03, 0x69, 0x70, 0x6e, 0x03, 0x64, 0x65, 0x76, 0x00, // name
0x00, 0x01, 0x00, 0x01, // type A, class IN
0x00, 0x00, 0x02, 0x58, // TTL: 600
0x00, 0x04, // length: 4 bytes
0x01, 0x02, 0x03, 0x04, // A: 1.2.3.4
}
var ipv4Response = []byte{
0x00, 0x00, // transaction id: 0
0x84, 0x00, // flags: response, authoritative, no error
0x00, 0x01, // one question
0x00, 0x01, // one answer
0x00, 0x00, 0x00, 0x00, // no authority or additional RRs
// Question:
0x05, 0x74, 0x65, 0x73, 0x74, 0x31, 0x03, 0x69, 0x70, 0x6e, 0x03, 0x64, 0x65, 0x76, 0x00, // name
0x00, 0x01, 0x00, 0x01, // type A, class IN
// Answer:
0x05, 0x74, 0x65, 0x73, 0x74, 0x31, 0x03, 0x69, 0x70, 0x6e, 0x03, 0x64, 0x65, 0x76, 0x00, // name
0x00, 0x01, 0x00, 0x01, // type A, class IN
0x00, 0x00, 0x02, 0x58, // TTL: 600
0x00, 0x04, // length: 4 bytes
0x01, 0x02, 0x03, 0x04, // A: 1.2.3.4
}
var ipv6Response = []byte{
0x00, 0x00, // transaction id: 0
0x84, 0x00, // flags: response, authoritative, no error
0x00, 0x01, // one question
0x00, 0x01, // one answer
0x00, 0x00, 0x00, 0x00, // no authority or additional RRs
// Question:
0x05, 0x74, 0x65, 0x73, 0x74, 0x32, 0x03, 0x69, 0x70, 0x6e, 0x03, 0x64, 0x65, 0x76, 0x00, // name
0x00, 0x1c, 0x00, 0x01, // type AAAA, class IN
// Answer:
0x05, 0x74, 0x65, 0x73, 0x74, 0x32, 0x03, 0x69, 0x70, 0x6e, 0x03, 0x64, 0x65, 0x76, 0x00, // name
0x00, 0x1c, 0x00, 0x01, // type AAAA, class IN
0x00, 0x00, 0x02, 0x58, // TTL: 600
0x00, 0x10, // length: 16 bytes
// AAAA: 0001:0203:0405:0607:0809:0A0B:0C0D:0E0F
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0xb, 0xc, 0xd, 0xe, 0xf,
}
var ipv4UppercaseResponse = []byte{
0x00, 0x00, // transaction id: 0
0x84, 0x00, // flags: response, authoritative, no error
0x00, 0x01, // one question
0x00, 0x01, // one answer
0x00, 0x00, 0x00, 0x00, // no authority or additional RRs
// Question:
0x05, 0x54, 0x45, 0x53, 0x54, 0x31, 0x03, 0x49, 0x50, 0x4e, 0x03, 0x44, 0x45, 0x56, 0x00, // name
0x00, 0x01, 0x00, 0x01, // type A, class IN
// Answer:
0x05, 0x54, 0x45, 0x53, 0x54, 0x31, 0x03, 0x49, 0x50, 0x4e, 0x03, 0x44, 0x45, 0x56, 0x00, // name
0x00, 0x01, 0x00, 0x01, // type A, class IN
0x00, 0x00, 0x02, 0x58, // TTL: 600
0x00, 0x04, // length: 4 bytes
0x01, 0x02, 0x03, 0x04, // A: 1.2.3.4
}
var ptrResponse = []byte{
0x00, 0x00, // transaction id: 0
0x84, 0x00, // flags: response, authoritative, no error
0x00, 0x01, // one question
0x00, 0x01, // one answer
0x00, 0x00, 0x00, 0x00, // no authority or additional RRs
// Question: 4.3.2.1.in-addr.arpa
0x01, 0x34, 0x01, 0x33, 0x01, 0x32, 0x01, 0x31, 0x07,
0x69, 0x6e, 0x2d, 0x61, 0x64, 0x64, 0x72, 0x04, 0x61, 0x72, 0x70, 0x61, 0x00,
0x00, 0x0c, 0x00, 0x01, // type PTR, class IN
// Answer: 4.3.2.1.in-addr.arpa
0x01, 0x34, 0x01, 0x33, 0x01, 0x32, 0x01, 0x31, 0x07,
0x69, 0x6e, 0x2d, 0x61, 0x64, 0x64, 0x72, 0x04, 0x61, 0x72, 0x70, 0x61, 0x00,
0x00, 0x0c, 0x00, 0x01, // type PTR, class IN
0x00, 0x00, 0x02, 0x58, // TTL: 600
0x00, 0x0f, // length: 15 bytes
// PTR: test1.ipn.dev
0x05, 0x74, 0x65, 0x73, 0x74, 0x31, 0x03, 0x69, 0x70, 0x6e, 0x03, 0x64, 0x65, 0x76, 0x00,
}
var ptrResponse6 = []byte{
0x00, 0x00, // transaction id: 0
0x84, 0x00, // flags: response, authoritative, no error
0x00, 0x01, // one question
0x00, 0x01, // one answer
0x00, 0x00, 0x00, 0x00, // no authority or additional RRs
// Question: f.0.e.0.d.0.c.0.b.0.a.0.9.0.8.0.7.0.6.0.5.0.4.0.3.0.2.0.1.0.0.0.ip6.arpa
0x01, 0x66, 0x01, 0x30, 0x01, 0x65, 0x01, 0x30,
0x01, 0x64, 0x01, 0x30, 0x01, 0x63, 0x01, 0x30,
0x01, 0x62, 0x01, 0x30, 0x01, 0x61, 0x01, 0x30,
0x01, 0x39, 0x01, 0x30, 0x01, 0x38, 0x01, 0x30,
0x01, 0x37, 0x01, 0x30, 0x01, 0x36, 0x01, 0x30,
0x01, 0x35, 0x01, 0x30, 0x01, 0x34, 0x01, 0x30,
0x01, 0x33, 0x01, 0x30, 0x01, 0x32, 0x01, 0x30,
0x01, 0x31, 0x01, 0x30, 0x01, 0x30, 0x01, 0x30,
0x03, 0x69, 0x70, 0x36,
0x04, 0x61, 0x72, 0x70, 0x61, 0x00,
0x00, 0x0c, 0x00, 0x01, // type PTR, class IN6
// Answer: f.0.e.0.d.0.c.0.b.0.a.0.9.0.8.0.7.0.6.0.5.0.4.0.3.0.2.0.1.0.0.0.ip6.arpa
0x01, 0x66, 0x01, 0x30, 0x01, 0x65, 0x01, 0x30,
0x01, 0x64, 0x01, 0x30, 0x01, 0x63, 0x01, 0x30,
0x01, 0x62, 0x01, 0x30, 0x01, 0x61, 0x01, 0x30,
0x01, 0x39, 0x01, 0x30, 0x01, 0x38, 0x01, 0x30,
0x01, 0x37, 0x01, 0x30, 0x01, 0x36, 0x01, 0x30,
0x01, 0x35, 0x01, 0x30, 0x01, 0x34, 0x01, 0x30,
0x01, 0x33, 0x01, 0x30, 0x01, 0x32, 0x01, 0x30,
0x01, 0x31, 0x01, 0x30, 0x01, 0x30, 0x01, 0x30,
0x03, 0x69, 0x70, 0x36,
0x04, 0x61, 0x72, 0x70, 0x61, 0x00,
0x00, 0x0c, 0x00, 0x01, // type PTR, class IN
0x00, 0x00, 0x02, 0x58, // TTL: 600
0x00, 0x0f, // length: 15 bytes
// PTR: test2.ipn.dev
0x05, 0x74, 0x65, 0x73, 0x74, 0x32, 0x03, 0x69, 0x70, 0x6e, 0x03, 0x64, 0x65, 0x76, 0x00,
}
var nxdomainResponse = []byte{
0x00, 0x00, // transaction id: 0
0x84, 0x03, // flags: response, authoritative, error: nxdomain
0x00, 0x01, // one question
0x00, 0x00, // no answers
0x00, 0x00, 0x00, 0x00, // no authority or additional RRs
// Question:
0x05, 0x74, 0x65, 0x73, 0x74, 0x33, 0x03, 0x69, 0x70, 0x6e, 0x03, 0x64, 0x65, 0x76, 0x00, // name
0x00, 0x01, 0x00, 0x01, // type A, class IN
}
var emptyResponse = []byte{
0x00, 0x00, // transaction id: 0
0x84, 0x00, // flags: response, authoritative, no error
0x00, 0x01, // one question
0x00, 0x00, // no answers
0x00, 0x00, 0x00, 0x00, // no authority or additional RRs
// Question:
0x05, 0x74, 0x65, 0x73, 0x74, 0x31, 0x03, 0x69, 0x70, 0x6e, 0x03, 0x64, 0x65, 0x76, 0x00, // name
0x00, 0x1c, 0x00, 0x01, // type AAAA, class IN
}
func TestFull(t *testing.T) {
r := NewResolver(ResolverConfig{Logf: t.Logf, Forward: false})
r.SetMap(dnsMap)
if err := r.Start(); err != nil {
t.Fatalf("start: %v", err)
}
defer r.Close()
// One full packet and one error packet
tests := []struct {
name string
request []byte
response []byte
}{
{"all", dnspacket("test1.ipn.dev.", dns.TypeALL), allResponse},
{"ipv4", dnspacket("test1.ipn.dev.", dns.TypeA), ipv4Response},
{"ipv6", dnspacket("test2.ipn.dev.", dns.TypeAAAA), ipv6Response},
{"no-ipv6", dnspacket("test1.ipn.dev.", dns.TypeAAAA), emptyResponse},
{"upper", dnspacket("TEST1.IPN.DEV.", dns.TypeA), ipv4UppercaseResponse},
{"ptr", dnspacket("4.3.2.1.in-addr.arpa.", dns.TypePTR), ptrResponse},
{"ptr", dnspacket("f.0.e.0.d.0.c.0.b.0.a.0.9.0.8.0.7.0.6.0.5.0.4.0.3.0.2.0.1.0.0.0.ip6.arpa.",
dns.TypePTR), ptrResponse6},
{"nxdomain", dnspacket("test3.ipn.dev.", dns.TypeA), nxdomainResponse},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
response, err := syncRespond(r, tt.request)
if err != nil {
t.Errorf("err = %v; want nil", err)
}
if !bytes.Equal(response, tt.response) {
t.Errorf("response = %x; want %x", response, tt.response)
}
})
}
}
func TestAllocs(t *testing.T) {
r := NewResolver(ResolverConfig{Logf: t.Logf, Forward: false})
r.SetMap(dnsMap)
if err := r.Start(); err != nil {
t.Fatalf("start: %v", err)
}
defer r.Close()
// It is seemingly pointless to test allocs in the delegate path,
// as dialer.Dial -> Read -> Write alone comprise 12 allocs.
tests := []struct {
name string
query []byte
want int
}{
// Name lowercasing and response slice created by dns.NewBuilder.
{"forward", dnspacket("test1.ipn.dev.", dns.TypeA), 2},
// 3 extra allocs in rdnsNameToIPv4 and one in marshalPTRRecord (dns.NewName).
{"reverse", dnspacket("4.3.2.1.in-addr.arpa.", dns.TypePTR), 5},
}
for _, tt := range tests {
allocs := testing.AllocsPerRun(100, func() {
syncRespond(r, tt.query)
})
if int(allocs) > tt.want {
t.Errorf("%s: allocs = %v; want %v", tt.name, allocs, tt.want)
}
}
}
func TestTrimRDNSBonjourPrefix(t *testing.T) {
tests := []struct {
in string
want bool
}{
{"b._dns-sd._udp.0.10.20.172.in-addr.arpa.", true},
{"db._dns-sd._udp.0.10.20.172.in-addr.arpa.", true},
{"r._dns-sd._udp.0.10.20.172.in-addr.arpa.", true},
{"dr._dns-sd._udp.0.10.20.172.in-addr.arpa.", true},
{"lb._dns-sd._udp.0.10.20.172.in-addr.arpa.", true},
{"qq._dns-sd._udp.0.10.20.172.in-addr.arpa.", false},
{"0.10.20.172.in-addr.arpa.", false},
{"i-have-no-dot", false},
}
for _, test := range tests {
got := hasRDNSBonjourPrefix(test.in)
if got != test.want {
t.Errorf("trimRDNSBonjourPrefix(%q) = %v, want %v", test.in, got, test.want)
}
}
}
func BenchmarkFull(b *testing.B) {
dnsHandleFunc("test.site.", resolveToIP(testipv4, testipv6, "dns.test.site."))
server, errch := serveDNS(b, "127.0.0.1:0")
defer func() {
if err := <-errch; err != nil {
b.Errorf("server error: %v", err)
}
}()
if server == nil {
return
}
defer server.Shutdown()
r := NewResolver(ResolverConfig{Logf: b.Logf, Forward: true})
r.SetMap(dnsMap)
r.SetUpstreams([]net.Addr{server.PacketConn.LocalAddr()})
if err := r.Start(); err != nil {
b.Fatalf("start: %v", err)
}
defer r.Close()
tests := []struct {
name string
request []byte
}{
{"forward", dnspacket("test1.ipn.dev.", dns.TypeA)},
{"reverse", dnspacket("4.3.2.1.in-addr.arpa.", dns.TypePTR)},
{"delegated", dnspacket("test.site.", dns.TypeA)},
}
for _, tt := range tests {
b.Run(tt.name, func(b *testing.B) {
for i := 0; i < b.N; i++ {
syncRespond(r, tt.request)
}
})
}
}
func TestMarshalResponseFormatError(t *testing.T) {
resp := new(response)
resp.Header.RCode = dns.RCodeFormatError
v, err := marshalResponse(resp)
if err != nil {
t.Errorf("marshal error: %v", err)
}
t.Logf("response: %q", v)
}