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net/dns,userspace: remove unused DNS paths, normalize query limit on iOS

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With a42a594bb3, iOS uses netstack and
hence there are no longer any platforms which use the legacy MagicDNS path. As such, we remove it.

We also normalize the limit for max in-flight DNS queries on iOS (it was 64, now its 256 as per other platforms).
It was 64 for the sake of being cautious about memory, but now we have 50Mb (iOS-15 and greater) instead of 15Mb
so we have the spare headroom.

Signed-off-by: Tom DNetto <tom@tailscale.com>
pull/6938/head
Tom DNetto 2 years ago committed by Tom
parent 10eec37cd9
commit 673b3d8dbd
3 changed files with 8 additions and 163 deletions
Show Stats Download Patch File Download Diff File

2
cmd/tailscaled/depaware.txt
Unescape Escape View File

@ -247,7 +247,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
tailscale.com/net/tsaddr from tailscale.com/ipn+
tailscale.com/net/tsdial from tailscale.com/control/controlclient+
💣 tailscale.com/net/tshttpproxy from tailscale.com/control/controlclient+
tailscale.com/net/tstun from tailscale.com/net/dns+
tailscale.com/net/tstun from tailscale.com/cmd/tailscaled+
tailscale.com/net/wsconn from tailscale.com/control/controlhttp+
tailscale.com/paths from tailscale.com/ipn/ipnlocal+
💣 tailscale.com/portlist from tailscale.com/ipn/ipnlocal

119
net/dns/manager.go
Unescape Escape View File

@ -19,41 +19,21 @@ import (
"golang.org/x/exp/slices"
"tailscale.com/health"
"tailscale.com/net/dns/resolver"
"tailscale.com/net/packet"
"tailscale.com/net/tsaddr"
"tailscale.com/net/tsdial"
"tailscale.com/net/tstun"
"tailscale.com/types/dnstype"
"tailscale.com/types/ipproto"
"tailscale.com/types/logger"
"tailscale.com/util/clientmetric"
"tailscale.com/util/dnsname"
"tailscale.com/wgengine/monitor"
)
var (
magicDNSIP = tsaddr.TailscaleServiceIP()
magicDNSIPv6 = tsaddr.TailscaleServiceIPv6()
)
var (
errFullQueue = errors.New("request queue full")
)
// maxActiveQueries returns the maximal number of DNS requests that be
// can running.
// If EnqueueRequest is called when this many requests are already pending,
// the request will be dropped to avoid blocking the caller.
func maxActiveQueries() int32 {
if runtime.GOOS == "ios" {
// For memory paranoia reasons on iOS, match the
// historical Tailscale 1.x..1.8 behavior for now
// (just before the 1.10 release).
return 64
}
// But for other platforms, allow more burstiness:
return 256
}
// maxActiveQueries returns the maximal number of DNS requests that can
// be running.
const maxActiveQueries = 256
// We use file-ignore below instead of ignore because on some platforms,
// the lint exception is necessary and on others it is not,
@ -75,13 +55,6 @@ type response struct {
type Manager struct {
logf logger.Logf
// When netstack is not used, Manager implements magic DNS.
// In this case, responses tracks completed DNS requests
// which need a response, and NextPacket() synthesizes a
// fake IP+UDP header to finish assembling the response.
//
// TODO(tom): Rip out once all platforms use netstack.
responses chan response
activeQueriesAtomic int32
ctx context.Context // good until Down
@ -101,7 +74,6 @@ func NewManager(logf logger.Logf, oscfg OSConfigurator, linkMon *monitor.Mon, di
logf: logf,
resolver: resolver.New(logf, linkMon, linkSel, dialer),
os: oscfg,
responses: make(chan response),
}
m.ctx, m.ctxCancel = context.WithCancel(context.Background())
m.logf("using %T", m.os)
@ -316,89 +288,6 @@ func toIPsOnly(resolvers []*dnstype.Resolver) (ret []netip.Addr) {
return ret
}
// EnqueuePacket is the legacy path for handling magic DNS traffic, and is
// called with a DNS request payload.
//
// TODO(tom): Rip out once all platforms use netstack.
func (m *Manager) EnqueuePacket(bs []byte, proto ipproto.Proto, from, to netip.AddrPort) error {
if to.Port() != 53 || proto != ipproto.UDP {
return nil
}
if n := atomic.AddInt32(&m.activeQueriesAtomic, 1); n > maxActiveQueries() {
atomic.AddInt32(&m.activeQueriesAtomic, -1)
metricDNSQueryErrorQueue.Add(1)
return errFullQueue
}
go func() {
resp, err := m.resolver.Query(m.ctx, bs, from)
if err != nil {
atomic.AddInt32(&m.activeQueriesAtomic, -1)
m.logf("dns query: %v", err)
return
}
select {
case <-m.ctx.Done():
return
case m.responses <- response{resp, from}:
}
}()
return nil
}
// NextPacket is the legacy path for obtaining DNS results in response to
// magic DNS queries. It blocks until a response is available.
//
// TODO(tom): Rip out once all platforms use netstack.
func (m *Manager) NextPacket() ([]byte, error) {
var resp response
select {
case <-m.ctx.Done():
return nil, net.ErrClosed
case resp = <-m.responses:
// continue
}
// Unused space is needed further down the stack. To avoid extra
// allocations/copying later on, we allocate such space here.
const offset = tstun.PacketStartOffset
var buf []byte
switch {
case resp.to.Addr().Is4():
h := packet.UDP4Header{
IP4Header: packet.IP4Header{
Src: magicDNSIP,
Dst: resp.to.Addr(),
},
SrcPort: 53,
DstPort: resp.to.Port(),
}
hlen := h.Len()
buf = make([]byte, offset+hlen+len(resp.pkt))
copy(buf[offset+hlen:], resp.pkt)
h.Marshal(buf[offset:])
case resp.to.Addr().Is6():
h := packet.UDP6Header{
IP6Header: packet.IP6Header{
Src: magicDNSIPv6,
Dst: resp.to.Addr(),
},
SrcPort: 53,
DstPort: resp.to.Port(),
}
hlen := h.Len()
buf = make([]byte, offset+hlen+len(resp.pkt))
copy(buf[offset+hlen:], resp.pkt)
h.Marshal(buf[offset:])
}
atomic.AddInt32(&m.activeQueriesAtomic, -1)
return buf, nil
}
// Query executes a DNS query received from the given address. The query is
// provided in bs as a wire-encoded DNS query without any transport header.
// This method is called for requests arriving over UDP and TCP.
@ -410,7 +299,7 @@ func (m *Manager) Query(ctx context.Context, bs []byte, from netip.AddrPort) ([]
// continue
}
if n := atomic.AddInt32(&m.activeQueriesAtomic, 1); n > maxActiveQueries() {
if n := atomic.AddInt32(&m.activeQueriesAtomic, 1); n > maxActiveQueries {
atomic.AddInt32(&m.activeQueriesAtomic, -1)
metricDNSQueryErrorQueue.Add(1)
return nil, errFullQueue

44
wgengine/userspace.go
Unescape Escape View File

@ -11,7 +11,6 @@ import (
"errors"
"fmt"
"io"
"net"
"net/netip"
"reflect"
"runtime"
@ -56,13 +55,6 @@ import (
"tailscale.com/wgengine/wglog"
)
const magicDNSPort = 53
var (
magicDNSIP = tsaddr.TailscaleServiceIP()
magicDNSIPv6 = tsaddr.TailscaleServiceIPv6()
)
// Lazy wireguard-go configuration parameters.
const (
// lazyPeerIdleThreshold is the idle duration after
@ -462,8 +454,6 @@ func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error)
e.logf("Starting link monitor...")
e.linkMon.Start()
go e.pollResolver()
e.logf("Engine created.")
return e, nil
}
@ -491,19 +481,6 @@ func echoRespondToAll(p *packet.Parsed, t *tstun.Wrapper) filter.Response {
// tailscaled directly. Other packets are allowed to proceed into the
// main ACL filter.
func (e *userspaceEngine) handleLocalPackets(p *packet.Parsed, t *tstun.Wrapper) filter.Response {
// Handle traffic to the service IP.
// TODO(tom): Netstack handles this when it is installed. Rip all
// this out once netstack is used on all platforms.
switch p.Dst.Addr() {
case magicDNSIP, magicDNSIPv6:
err := e.dns.EnqueuePacket(append([]byte(nil), p.Payload()...), p.IPProto, p.Src, p.Dst)
if err != nil {
e.logf("dns: enqueue: %v", err)
}
metricMagicDNSPacketIn.Add(1)
return filter.Drop
}
if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
isLocalAddr, ok := e.isLocalAddr.LoadOk()
if !ok {
@ -523,27 +500,6 @@ func (e *userspaceEngine) handleLocalPackets(p *packet.Parsed, t *tstun.Wrapper)
return filter.Accept
}
// pollResolver reads packets from the DNS resolver and injects them inbound.
//
// TODO(tom): Remove this fallback path (via NextPacket()) once all
// platforms use netstack.
func (e *userspaceEngine) pollResolver() {
for {
bs, err := e.dns.NextPacket()
if errors.Is(err, net.ErrClosed) {
return
}
if err != nil {
e.logf("dns: error: %v", err)
continue
}
// The leading empty space required by the semantics of
// InjectInboundDirect is allocated in NextPacket().
e.tundev.InjectInboundDirect(bs, tstun.PacketStartOffset)
}
}
var debugTrimWireguard = envknob.RegisterOptBool("TS_DEBUG_TRIM_WIREGUARD")
// forceFullWireguardConfig reports whether we should give wireguard our full

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