-
Notifications
You must be signed in to change notification settings - Fork 1.4k
/
derphttp_client.go
815 lines (742 loc) · 21.6 KB
/
derphttp_client.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
// 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 derphttp implements DERP-over-HTTP.
//
// This makes DERP look exactly like WebSockets.
// A server can implement DERP over HTTPS and even if the TLS connection
// intercepted using a fake root CA, unless the interceptor knows how to
// detect DERP packets, it will look like a web socket.
package derphttp
import (
"bufio"
"context"
"crypto/tls"
"crypto/x509"
"errors"
"fmt"
"io"
"io/ioutil"
"log"
"net"
"net/http"
"net/url"
"os"
"strings"
"sync"
"time"
"go4.org/mem"
"inet.af/netaddr"
"tailscale.com/derp"
"tailscale.com/net/dnscache"
"tailscale.com/net/netns"
"tailscale.com/net/tlsdial"
"tailscale.com/net/tshttpproxy"
"tailscale.com/tailcfg"
"tailscale.com/types/key"
"tailscale.com/types/logger"
)
// Client is a DERP-over-HTTP client.
//
// It automatically reconnects on error retry. That is, a failed Send or
// Recv will report the error and not retry, but subsequent calls to
// Send/Recv will completely re-establish the connection (unless Close
// has been called).
type Client struct {
TLSConfig *tls.Config // optional; nil means default
DNSCache *dnscache.Resolver // optional; nil means no caching
MeshKey string // optional; for trusted clients
privateKey key.Private
logf logger.Logf
// Either url or getRegion is non-nil:
url *url.URL
getRegion func() *tailcfg.DERPRegion
ctx context.Context // closed via cancelCtx in Client.Close
cancelCtx context.CancelFunc
mu sync.Mutex
preferred bool
canAckPings bool
closed bool
netConn io.Closer
client *derp.Client
connGen int // incremented once per new connection; valid values are >0
serverPubKey key.Public
}
// NewRegionClient returns a new DERP-over-HTTP client. It connects lazily.
// To trigger a connection, use Connect.
func NewRegionClient(privateKey key.Private, logf logger.Logf, getRegion func() *tailcfg.DERPRegion) *Client {
ctx, cancel := context.WithCancel(context.Background())
c := &Client{
privateKey: privateKey,
logf: logf,
getRegion: getRegion,
ctx: ctx,
cancelCtx: cancel,
}
return c
}
// NewNetcheckClient returns a Client that's only able to have its DialRegion method called.
// It's used by the netcheck package.
func NewNetcheckClient(logf logger.Logf) *Client {
return &Client{logf: logf}
}
// NewClient returns a new DERP-over-HTTP client. It connects lazily.
// To trigger a connection, use Connect.
func NewClient(privateKey key.Private, serverURL string, logf logger.Logf) (*Client, error) {
u, err := url.Parse(serverURL)
if err != nil {
return nil, fmt.Errorf("derphttp.NewClient: %v", err)
}
if urlPort(u) == "" {
return nil, fmt.Errorf("derphttp.NewClient: invalid URL scheme %q", u.Scheme)
}
ctx, cancel := context.WithCancel(context.Background())
c := &Client{
privateKey: privateKey,
logf: logf,
url: u,
ctx: ctx,
cancelCtx: cancel,
}
return c, nil
}
// Connect connects or reconnects to the server, unless already connected.
// It returns nil if there was already a good connection, or if one was made.
func (c *Client) Connect(ctx context.Context) error {
_, _, err := c.connect(ctx, "derphttp.Client.Connect")
return err
}
// ServerPublicKey returns the server's public key.
//
// It only returns a non-zero value once a connection has succeeded
// from an earlier call.
func (c *Client) ServerPublicKey() key.Public {
c.mu.Lock()
defer c.mu.Unlock()
return c.serverPubKey
}
func urlPort(u *url.URL) string {
if p := u.Port(); p != "" {
return p
}
switch u.Scheme {
case "https":
return "443"
case "http":
return "80"
}
return ""
}
func (c *Client) targetString(reg *tailcfg.DERPRegion) string {
if c.url != nil {
return c.url.String()
}
return fmt.Sprintf("region %d (%v)", reg.RegionID, reg.RegionCode)
}
func (c *Client) useHTTPS() bool {
if c.url != nil && c.url.Scheme == "http" {
return false
}
return true
}
// tlsServerName returns the tls.Config.ServerName value (for the TLS ClientHello).
func (c *Client) tlsServerName(node *tailcfg.DERPNode) string {
if c.url != nil {
return c.url.Host
}
return node.HostName
}
func (c *Client) urlString(node *tailcfg.DERPNode) string {
if c.url != nil {
return c.url.String()
}
return fmt.Sprintf("https://%s/derp", node.HostName)
}
func (c *Client) connect(ctx context.Context, caller string) (client *derp.Client, connGen int, err error) {
c.mu.Lock()
defer c.mu.Unlock()
if c.closed {
return nil, 0, ErrClientClosed
}
if c.client != nil {
return c.client, c.connGen, nil
}
// timeout is the fallback maximum time (if ctx doesn't limit
// it further) to do all of: DNS + TCP + TLS + HTTP Upgrade +
// DERP upgrade.
const timeout = 10 * time.Second
ctx, cancel := context.WithTimeout(ctx, timeout)
go func() {
select {
case <-ctx.Done():
// Either timeout fired (handled below), or
// we're returning via the defer cancel()
// below.
case <-c.ctx.Done():
// Propagate a Client.Close call into
// cancelling this context.
cancel()
}
}()
defer cancel()
var reg *tailcfg.DERPRegion // nil when using c.url to dial
if c.getRegion != nil {
reg = c.getRegion()
if reg == nil {
return nil, 0, errors.New("DERP region not available")
}
}
var tcpConn net.Conn
defer func() {
if err != nil {
if ctx.Err() != nil {
err = fmt.Errorf("%v: %v", ctx.Err(), err)
}
err = fmt.Errorf("%s connect to %v: %v", caller, c.targetString(reg), err)
if tcpConn != nil {
go tcpConn.Close()
}
}
}()
var node *tailcfg.DERPNode // nil when using c.url to dial
if c.url != nil {
c.logf("%s: connecting to %v", caller, c.url)
tcpConn, err = c.dialURL(ctx)
} else {
c.logf("%s: connecting to derp-%d (%v)", caller, reg.RegionID, reg.RegionCode)
tcpConn, node, err = c.dialRegion(ctx, reg)
}
if err != nil {
return nil, 0, err
}
// Now that we have a TCP connection, force close it if the
// TLS handshake + DERP setup takes too long.
done := make(chan struct{})
defer close(done)
go func() {
select {
case <-done:
// Normal path. Upgrade occurred in time.
case <-ctx.Done():
select {
case <-done:
// Normal path. Upgrade occurred in time.
// But the ctx.Done() is also done because
// the "defer cancel()" above scheduled
// before this goroutine.
default:
// The TLS or HTTP or DERP exchanges didn't complete
// in time. Force close the TCP connection to force
// them to fail quickly.
tcpConn.Close()
}
}
}()
var httpConn net.Conn // a TCP conn or a TLS conn; what we speak HTTP to
var serverPub key.Public // or zero if unknown (if not using TLS or TLS middlebox eats it)
var serverProtoVersion int
if c.useHTTPS() {
tlsConn := c.tlsClient(tcpConn, node)
httpConn = tlsConn
// Force a handshake now (instead of waiting for it to
// be done implicitly on read/write) so we can check
// the ConnectionState.
if err := tlsConn.Handshake(); err != nil {
return nil, 0, err
}
// We expect to be using TLS 1.3 to our own servers, and only
// starting at TLS 1.3 are the server's returned certificates
// encrypted, so only look for and use our "meta cert" if we're
// using TLS 1.3. If we're not using TLS 1.3, it might be a user
// running cmd/derper themselves with a different configuration,
// in which case we can avoid this fast-start optimization.
// (If a corporate proxy is MITM'ing TLS 1.3 connections with
// corp-mandated TLS root certs than all bets are off anyway.)
// Note that we're not specifically concerned about TLS downgrade
// attacks. TLS handles that fine:
// https://blog.gypsyengineer.com/en/security/how-does-tls-1-3-protect-against-downgrade-attacks.html
connState := tlsConn.ConnectionState()
if connState.Version >= tls.VersionTLS13 {
serverPub, serverProtoVersion = parseMetaCert(connState.PeerCertificates)
}
} else {
httpConn = tcpConn
}
brw := bufio.NewReadWriter(bufio.NewReader(httpConn), bufio.NewWriter(httpConn))
var derpClient *derp.Client
req, err := http.NewRequest("GET", c.urlString(node), nil)
if err != nil {
return nil, 0, err
}
req.Header.Set("Upgrade", "DERP")
req.Header.Set("Connection", "Upgrade")
if !serverPub.IsZero() && serverProtoVersion != 0 {
// parseMetaCert found the server's public key (no TLS
// middlebox was in the way), so skip the HTTP upgrade
// exchange. See https://github.com/tailscale/tailscale/issues/693
// for an overview. We still send the HTTP request
// just to get routed into the server's HTTP Handler so it
// can Hijack the request, but we signal with a special header
// that we don't want to deal with its HTTP response.
req.Header.Set(fastStartHeader, "1") // suppresses the server's HTTP response
if err := req.Write(brw); err != nil {
return nil, 0, err
}
// No need to flush the HTTP request. the derp.Client's initial
// client auth frame will flush it.
} else {
if err := req.Write(brw); err != nil {
return nil, 0, err
}
if err := brw.Flush(); err != nil {
return nil, 0, err
}
resp, err := http.ReadResponse(brw.Reader, req)
if err != nil {
return nil, 0, err
}
if resp.StatusCode != http.StatusSwitchingProtocols {
b, _ := ioutil.ReadAll(resp.Body)
resp.Body.Close()
return nil, 0, fmt.Errorf("GET failed: %v: %s", err, b)
}
}
derpClient, err = derp.NewClient(c.privateKey, httpConn, brw, c.logf,
derp.MeshKey(c.MeshKey),
derp.ServerPublicKey(serverPub),
derp.CanAckPings(c.canAckPings),
)
if err != nil {
return nil, 0, err
}
if c.preferred {
if err := derpClient.NotePreferred(true); err != nil {
go httpConn.Close()
return nil, 0, err
}
}
c.serverPubKey = derpClient.ServerPublicKey()
c.client = derpClient
c.netConn = tcpConn
c.connGen++
return c.client, c.connGen, nil
}
func (c *Client) dialURL(ctx context.Context) (net.Conn, error) {
host := c.url.Hostname()
hostOrIP := host
dialer := netns.NewDialer()
if c.DNSCache != nil {
ip, _, err := c.DNSCache.LookupIP(ctx, host)
if err == nil {
hostOrIP = ip.String()
}
if err != nil && netns.IsSOCKSDialer(dialer) {
// Return an error if we're not using a dial
// proxy that can do DNS lookups for us.
return nil, err
}
}
tcpConn, err := dialer.DialContext(ctx, "tcp", net.JoinHostPort(hostOrIP, urlPort(c.url)))
if err != nil {
return nil, fmt.Errorf("dial of %v: %v", host, err)
}
return tcpConn, nil
}
// dialRegion returns a TCP connection to the provided region, trying
// each node in order (with dialNode) until one connects or ctx is
// done.
func (c *Client) dialRegion(ctx context.Context, reg *tailcfg.DERPRegion) (net.Conn, *tailcfg.DERPNode, error) {
if len(reg.Nodes) == 0 {
return nil, nil, fmt.Errorf("no nodes for %s", c.targetString(reg))
}
var firstErr error
for _, n := range reg.Nodes {
if n.STUNOnly {
if firstErr == nil {
firstErr = fmt.Errorf("no non-STUNOnly nodes for %s", c.targetString(reg))
}
continue
}
c, err := c.dialNode(ctx, n)
if err == nil {
return c, n, nil
}
if firstErr == nil {
firstErr = err
}
}
return nil, nil, firstErr
}
func (c *Client) tlsClient(nc net.Conn, node *tailcfg.DERPNode) *tls.Conn {
tlsConf := tlsdial.Config(c.tlsServerName(node), c.TLSConfig)
if node != nil {
if node.DERPTestPort != 0 {
tlsConf.InsecureSkipVerify = true
}
if node.CertName != "" {
tlsdial.SetConfigExpectedCert(tlsConf, node.CertName)
}
}
if n := os.Getenv("SSLKEYLOGFILE"); n != "" {
f, err := os.OpenFile(n, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0600)
if err != nil {
log.Fatal(err)
}
log.Printf("WARNING: writing to SSLKEYLOGFILE %v", n)
tlsConf.KeyLogWriter = f
}
return tls.Client(nc, tlsConf)
}
func (c *Client) DialRegionTLS(ctx context.Context, reg *tailcfg.DERPRegion) (tlsConn *tls.Conn, connClose io.Closer, err error) {
tcpConn, node, err := c.dialRegion(ctx, reg)
if err != nil {
return nil, nil, err
}
done := make(chan bool) // unbufferd
defer close(done)
tlsConn = c.tlsClient(tcpConn, node)
go func() {
select {
case <-done:
case <-ctx.Done():
tcpConn.Close()
}
}()
err = tlsConn.Handshake()
if err != nil {
return nil, nil, err
}
select {
case done <- true:
return tlsConn, tcpConn, nil
case <-ctx.Done():
return nil, nil, ctx.Err()
}
}
func (c *Client) dialContext(ctx context.Context, proto, addr string) (net.Conn, error) {
return netns.NewDialer().DialContext(ctx, proto, addr)
}
// shouldDialProto reports whether an explicitly provided IPv4 or IPv6
// address (given in s) is valid. An empty value means to dial, but to
// use DNS. The predicate function reports whether the non-empty
// string s contained a valid IP address of the right family.
func shouldDialProto(s string, pred func(netaddr.IP) bool) bool {
if s == "" {
return true
}
ip, _ := netaddr.ParseIP(s)
return pred(ip)
}
const dialNodeTimeout = 1500 * time.Millisecond
// dialNode returns a TCP connection to node n, racing IPv4 and IPv6
// (both as applicable) against each other.
// A node is only given dialNodeTimeout to connect.
//
// TODO(bradfitz): longer if no options remain perhaps? ... Or longer
// overall but have dialRegion start overlapping races?
func (c *Client) dialNode(ctx context.Context, n *tailcfg.DERPNode) (net.Conn, error) {
// First see if we need to use an HTTP proxy.
proxyReq := &http.Request{
Method: "GET", // doesn't really matter
URL: &url.URL{
Scheme: "https",
Host: c.tlsServerName(n),
Path: "/", // unused
},
}
if proxyURL, err := tshttpproxy.ProxyFromEnvironment(proxyReq); err == nil && proxyURL != nil {
return c.dialNodeUsingProxy(ctx, n, proxyURL)
}
type res struct {
c net.Conn
err error
}
resc := make(chan res) // must be unbuffered
ctx, cancel := context.WithTimeout(ctx, dialNodeTimeout)
defer cancel()
nwait := 0
startDial := func(dstPrimary, proto string) {
nwait++
go func() {
dst := dstPrimary
if dst == "" {
dst = n.HostName
}
port := "443"
if n.DERPTestPort != 0 {
port = fmt.Sprint(n.DERPTestPort)
}
c, err := c.dialContext(ctx, proto, net.JoinHostPort(dst, port))
select {
case resc <- res{c, err}:
case <-ctx.Done():
if c != nil {
c.Close()
}
}
}()
}
if shouldDialProto(n.IPv4, netaddr.IP.Is4) {
startDial(n.IPv4, "tcp4")
}
if shouldDialProto(n.IPv6, netaddr.IP.Is6) {
startDial(n.IPv6, "tcp6")
}
if nwait == 0 {
return nil, errors.New("both IPv4 and IPv6 are explicitly disabled for node")
}
var firstErr error
for {
select {
case res := <-resc:
nwait--
if res.err == nil {
return res.c, nil
}
if firstErr == nil {
firstErr = res.err
}
if nwait == 0 {
return nil, firstErr
}
case <-ctx.Done():
return nil, ctx.Err()
}
}
}
func firstStr(a, b string) string {
if a != "" {
return a
}
return b
}
// dialNodeUsingProxy connects to n using a CONNECT to the HTTP(s) proxy in proxyURL.
func (c *Client) dialNodeUsingProxy(ctx context.Context, n *tailcfg.DERPNode, proxyURL *url.URL) (proxyConn net.Conn, err error) {
pu := proxyURL
if pu.Scheme == "https" {
var d tls.Dialer
proxyConn, err = d.DialContext(ctx, "tcp", net.JoinHostPort(pu.Hostname(), firstStr(pu.Port(), "443")))
} else {
var d net.Dialer
proxyConn, err = d.DialContext(ctx, "tcp", net.JoinHostPort(pu.Hostname(), firstStr(pu.Port(), "80")))
}
defer func() {
if err != nil && proxyConn != nil {
// In a goroutine in case it's a *tls.Conn (that can block on Close)
// TODO(bradfitz): track the underlying tcp.Conn and just close that instead.
go proxyConn.Close()
}
}()
if err != nil {
return nil, err
}
done := make(chan struct{})
defer close(done)
go func() {
select {
case <-done:
return
case <-ctx.Done():
proxyConn.Close()
}
}()
target := net.JoinHostPort(n.HostName, "443")
var authHeader string
if v, err := tshttpproxy.GetAuthHeader(pu); err != nil {
c.logf("derphttp: error getting proxy auth header for %v: %v", proxyURL, err)
} else if v != "" {
authHeader = fmt.Sprintf("Proxy-Authorization: %s\r\n", v)
}
if _, err := fmt.Fprintf(proxyConn, "CONNECT %s HTTP/1.1\r\nHost: %s\r\n%s\r\n", target, pu.Hostname(), authHeader); err != nil {
if ctx.Err() != nil {
return nil, ctx.Err()
}
return nil, err
}
br := bufio.NewReader(proxyConn)
res, err := http.ReadResponse(br, nil)
if err != nil {
if ctx.Err() != nil {
return nil, ctx.Err()
}
c.logf("derphttp: CONNECT dial to %s: %v", target, err)
return nil, err
}
c.logf("derphttp: CONNECT dial to %s: %v", target, res.Status)
if res.StatusCode != 200 {
return nil, fmt.Errorf("invalid response status from HTTP proxy %s on CONNECT to %s: %v", pu, target, res.Status)
}
return proxyConn, nil
}
func (c *Client) Send(dstKey key.Public, b []byte) error {
client, _, err := c.connect(context.TODO(), "derphttp.Client.Send")
if err != nil {
return err
}
if err := client.Send(dstKey, b); err != nil {
c.closeForReconnect(client)
}
return err
}
func (c *Client) ForwardPacket(from, to key.Public, b []byte) error {
client, _, err := c.connect(context.TODO(), "derphttp.Client.ForwardPacket")
if err != nil {
return err
}
if err := client.ForwardPacket(from, to, b); err != nil {
c.closeForReconnect(client)
}
return err
}
// SendPong sends a reply to a ping, with the ping's provided
// challenge/identifier data.
//
// Unlike other send methods, SendPong makes no attempt to connect or
// reconnect to the peer. It's best effort. If there's a connection
// problem, the server will choose to hang up on us if we're not
// replying.
func (c *Client) SendPong(data [8]byte) error {
c.mu.Lock()
if c.closed {
c.mu.Unlock()
return ErrClientClosed
}
if c.client == nil {
c.mu.Unlock()
return errors.New("not connected")
}
dc := c.client
c.mu.Unlock()
return dc.SendPong(data)
}
// SetCanAckPings sets whether this client will reply to ping requests from the server.
//
// This only affects future connections.
func (c *Client) SetCanAckPings(v bool) {
c.mu.Lock()
defer c.mu.Unlock()
c.canAckPings = v
}
// NotePreferred notes whether this Client is the caller's preferred
// (home) DERP node. It's only used for stats.
func (c *Client) NotePreferred(v bool) {
c.mu.Lock()
if c.preferred == v {
c.mu.Unlock()
return
}
c.preferred = v
client := c.client
c.mu.Unlock()
if client != nil {
if err := client.NotePreferred(v); err != nil {
c.closeForReconnect(client)
}
}
}
// WatchConnectionChanges sends a request to subscribe to
// notifications about clients connecting & disconnecting.
//
// Only trusted connections (using MeshKey) are allowed to use this.
func (c *Client) WatchConnectionChanges() error {
client, _, err := c.connect(context.TODO(), "derphttp.Client.WatchConnectionChanges")
if err != nil {
return err
}
err = client.WatchConnectionChanges()
if err != nil {
c.closeForReconnect(client)
}
return err
}
// ClosePeer asks the server to close target's TCP connection.
//
// Only trusted connections (using MeshKey) are allowed to use this.
func (c *Client) ClosePeer(target key.Public) error {
client, _, err := c.connect(context.TODO(), "derphttp.Client.ClosePeer")
if err != nil {
return err
}
err = client.ClosePeer(target)
if err != nil {
c.closeForReconnect(client)
}
return err
}
// Recv reads a message from c. The returned message may alias memory from Client.
// The message should only be used until the next Client call.
func (c *Client) Recv() (derp.ReceivedMessage, error) {
m, _, err := c.RecvDetail()
return m, err
}
// RecvDetail is like Recv, but additional returns the connection generation on each message.
// The connGen value is incremented every time the derphttp.Client reconnects to the server.
func (c *Client) RecvDetail() (m derp.ReceivedMessage, connGen int, err error) {
client, connGen, err := c.connect(context.TODO(), "derphttp.Client.Recv")
if err != nil {
return nil, 0, err
}
m, err = client.Recv()
if err != nil {
c.closeForReconnect(client)
if c.isClosed() {
err = ErrClientClosed
}
}
return m, connGen, err
}
func (c *Client) isClosed() bool {
c.mu.Lock()
defer c.mu.Unlock()
return c.closed
}
// Close closes the client. It will not automatically reconnect after
// being closed.
func (c *Client) Close() error {
c.cancelCtx() // not in lock, so it can cancel Connect, which holds mu
c.mu.Lock()
defer c.mu.Unlock()
if c.closed {
return ErrClientClosed
}
c.closed = true
if c.netConn != nil {
c.netConn.Close()
}
return nil
}
// closeForReconnect closes the underlying network connection and
// zeros out the client field so future calls to Connect will
// reconnect.
//
// The provided brokenClient is the client to forget. If current
// client is not brokenClient, closeForReconnect does nothing. (This
// prevents a send and receive goroutine from failing at the ~same
// time and both calling closeForReconnect and the caller goroutines
// forever calling closeForReconnect in lockstep endlessly;
// https://github.com/tailscale/tailscale/pull/264)
func (c *Client) closeForReconnect(brokenClient *derp.Client) {
c.mu.Lock()
defer c.mu.Unlock()
if c.client != brokenClient {
return
}
if c.netConn != nil {
c.netConn.Close()
c.netConn = nil
}
c.client = nil
}
var ErrClientClosed = errors.New("derphttp.Client closed")
func parseMetaCert(certs []*x509.Certificate) (serverPub key.Public, serverProtoVersion int) {
for _, cert := range certs {
if cn := cert.Subject.CommonName; strings.HasPrefix(cn, "derpkey") {
var err error
serverPub, err = key.NewPublicFromHexMem(mem.S(strings.TrimPrefix(cn, "derpkey")))
if err == nil && cert.SerialNumber.BitLen() <= 8 { // supports up to version 255
return serverPub, int(cert.SerialNumber.Int64())
}
}
}
return key.Public{}, 0
}