derp/derphttp: add Client.Ping, SendPing methods

Continuing work in 434af15a04, to make it possible for magicsock to
probe whether a DERP server is still there.

Updates #3619

Change-Id: I366a77c27e93b876734e64f445b85ef01eb590f2
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
pull/3630/head
Brad Fitzpatrick 3 years ago committed by Brad Fitzpatrick
parent 434af15a04
commit 535b925d1b

@ -13,6 +13,7 @@ package derphttp
import (
"bufio"
"context"
"crypto/rand"
"crypto/tls"
"crypto/x509"
"errors"
@ -72,6 +73,7 @@ type Client struct {
client *derp.Client
connGen int // incremented once per new connection; valid values are >0
serverPubKey key.NodePublic
pingOut map[derp.PingMessage]chan<- bool // chan to send to on pong
}
// NewRegionClient returns a new DERP-over-HTTP client. It connects lazily.
@ -698,7 +700,67 @@ func (c *Client) Send(dstKey key.NodePublic, b []byte) error {
return err
}
// SendPing sends a ping message, without any implicit connect or reconnect.
func (c *Client) registerPing(m derp.PingMessage, ch chan<- bool) {
c.mu.Lock()
defer c.mu.Unlock()
if c.pingOut == nil {
c.pingOut = map[derp.PingMessage]chan<- bool{}
}
c.pingOut[m] = ch
}
func (c *Client) unregisterPing(m derp.PingMessage) {
c.mu.Lock()
defer c.mu.Unlock()
delete(c.pingOut, m)
}
func (c *Client) handledPong(m derp.PongMessage) bool {
c.mu.Lock()
defer c.mu.Unlock()
k := derp.PingMessage(m)
if ch, ok := c.pingOut[k]; ok {
ch <- true
delete(c.pingOut, k)
return true
}
return false
}
// Ping sends a ping to the peer and waits for it either to be
// acknowledged (in which case Ping returns nil) or waits for ctx to
// be over and returns an error. It will wait at most 5 seconds
// before returning an error.
//
// Another goroutine must be in a loop calling Recv or
// RecvDetail or ping responses won't be handled.
func (c *Client) Ping(ctx context.Context) error {
maxDL := time.Now().Add(5 * time.Second)
if dl, ok := ctx.Deadline(); !ok || dl.After(maxDL) {
var cancel context.CancelFunc
ctx, cancel = context.WithDeadline(ctx, maxDL)
defer cancel()
}
var data derp.PingMessage
rand.Read(data[:])
gotPing := make(chan bool, 1)
c.registerPing(data, gotPing)
defer c.unregisterPing(data)
if err := c.SendPing(data); err != nil {
return err
}
select {
case <-gotPing:
return nil
case <-ctx.Done():
return ctx.Err()
}
}
// SendPing writes a ping message, without any implicit connect or
// reconnect. This is a lower-level interface that writes a frame
// without any implicit handling of the response pong, if any. For a
// higher-level interface, use Ping.
func (c *Client) SendPing(data [8]byte) error {
c.mu.Lock()
closed, client := c.closed, c.client
@ -819,14 +881,22 @@ func (c *Client) RecvDetail() (m derp.ReceivedMessage, connGen int, err error) {
if err != nil {
return nil, 0, err
}
m, err = client.Recv()
if err != nil {
c.closeForReconnect(client)
if c.isClosed() {
err = ErrClientClosed
for {
m, err = client.Recv()
switch m := m.(type) {
case derp.PongMessage:
if c.handledPong(m) {
continue
}
}
if err != nil {
c.closeForReconnect(client)
if c.isClosed() {
err = ErrClientClosed
}
}
return m, connGen, err
}
return m, connGen, err
}
func (c *Client) isClosed() bool {

@ -154,3 +154,55 @@ func waitConnect(t testing.TB, c *Client) {
t.Fatalf("client first Recv was unexpected type %T", v)
}
}
func TestPing(t *testing.T) {
serverPrivateKey := key.NewNode()
s := derp.NewServer(serverPrivateKey, t.Logf)
defer s.Close()
httpsrv := &http.Server{
TLSNextProto: make(map[string]func(*http.Server, *tls.Conn, http.Handler)),
Handler: Handler(s),
}
ln, err := net.Listen("tcp4", "localhost:0")
if err != nil {
t.Fatal(err)
}
serverURL := "http://" + ln.Addr().String()
t.Logf("server URL: %s", serverURL)
go func() {
if err := httpsrv.Serve(ln); err != nil {
if err == http.ErrServerClosed {
return
}
panic(err)
}
}()
c, err := NewClient(key.NewNode(), serverURL, t.Logf)
if err != nil {
t.Fatalf("NewClient: %v", err)
}
defer c.Close()
if err := c.Connect(context.Background()); err != nil {
t.Fatalf("client Connect: %v", err)
}
errc := make(chan error, 1)
go func() {
for {
m, err := c.Recv()
if err != nil {
errc <- err
return
}
t.Logf("Recv: %T", m)
}
}()
err = c.Ping(context.Background())
if err != nil {
t.Fatalf("Ping: %v", err)
}
}

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