tailscale/derp/derphttp/mesh_client.go

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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 derphttp
import (
"context"
"sync"
"time"
"tailscale.com/derp"
"tailscale.com/types/key"
"tailscale.com/types/logger"
)
// RunWatchConnectionLoop loops until ctx is done, sending WatchConnectionChanges and subscribing to
// connection changes.
//
// If the server's public key is ignoreServerKey, RunWatchConnectionLoop returns.
//
// Otherwise, the add and remove funcs are called as clients come & go.
//
// infoLogf, if non-nil, is the logger to write periodic status
// updates about how many peers are on the server. Error log output is
// set to the c's logger, regardless of infoLogf's value.
//
// To force RunWatchConnectionLoop to return quickly, its ctx needs to
// be closed, and c itself needs to be closed.
func (c *Client) RunWatchConnectionLoop(ctx context.Context, ignoreServerKey key.NodePublic, infoLogf logger.Logf, add, remove func(key.NodePublic)) {
if infoLogf == nil {
infoLogf = logger.Discard
}
logf := c.logf
const retryInterval = 5 * time.Second
const statusInterval = 10 * time.Second
var (
mu sync.Mutex
present = map[key.NodePublic]bool{}
loggedConnected = false
)
clear := func() {
mu.Lock()
defer mu.Unlock()
if len(present) == 0 {
return
}
logf("reconnected; clearing %d forwarding mappings", len(present))
for k := range present {
remove(k)
}
present = map[key.NodePublic]bool{}
}
lastConnGen := 0
lastStatus := time.Now()
logConnectedLocked := func() {
if loggedConnected {
return
}
infoLogf("connected; %d peers", len(present))
loggedConnected = true
}
const logConnectedDelay = 200 * time.Millisecond
timer := time.AfterFunc(2*time.Second, func() {
mu.Lock()
defer mu.Unlock()
logConnectedLocked()
})
defer timer.Stop()
updatePeer := func(k key.NodePublic, isPresent bool) {
if isPresent {
add(k)
} else {
remove(k)
}
mu.Lock()
defer mu.Unlock()
if isPresent {
present[k] = true
if !loggedConnected {
timer.Reset(logConnectedDelay)
}
} else {
// If we got a peerGone message, that means the initial connection's
// flood of peerPresent messages is done, so we can log already:
logConnectedLocked()
delete(present, k)
}
}
sleep := func(d time.Duration) {
t := time.NewTimer(d)
select {
case <-ctx.Done():
t.Stop()
case <-t.C:
}
}
for ctx.Err() == nil {
err := c.WatchConnectionChanges()
if err != nil {
clear()
logf("WatchConnectionChanges: %v", err)
sleep(retryInterval)
continue
}
if c.ServerPublicKey() == ignoreServerKey {
logf("detected self-connect; ignoring host")
return
}
for {
m, connGen, err := c.RecvDetail()
if err != nil {
clear()
logf("Recv: %v", err)
sleep(retryInterval)
break
}
if connGen != lastConnGen {
lastConnGen = connGen
clear()
}
switch m := m.(type) {
case derp.PeerPresentMessage:
updatePeer(key.NodePublic(m), true)
case derp.PeerGoneMessage:
updatePeer(key.NodePublic(m), false)
default:
continue
}
if now := time.Now(); now.Sub(lastStatus) > statusInterval {
lastStatus = now
infoLogf("%d peers", len(present))
}
}
}
}