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derp: add optional debug logging for prober clients

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This allows tracking packet flow via logs for prober clients. Note that
the new sclient.debug() function is called on every received packet, but
will do nothing for most clients.

I have adjusted sclient logging to print public keys in short format
rather than full. This takes effect even for existing non-debug logging
(mostly client disconnect messages).

Example logs for a packet being sent from client [SbsJn] (connected to
derper [dM2E3]) to client [10WOo] (connected to derper [AVxvv]):

```
derper [dM2E3]:
derp client 10.0.0.1:35470[SbsJn]: register single client mesh("10.0.1.1"): 4 peers
derp client 10.0.0.1:35470[SbsJn]: read frame type 4 len 40 err <nil>
derp client 10.0.0.1:35470[SbsJn]: SendPacket for [10WOo], forwarding via <derphttp_client.Client [AVxvv] url=https://10.0.1.1/derp>: <nil>
derp client 10.0.0.1:35470[SbsJn]: read frame type 0 len 0 err EOF
derp client 10.0.0.1:35470[SbsJn]: read EOF
derp client 10.0.0.1:35470[SbsJn]: sender failed: context canceled
derp client 10.0.0.1:35470[SbsJn]: removing connection

derper [AVxvv]:
derp client 10.0.1.1:50650[10WOo]: register single client
derp client 10.0.1.1:50650[10WOo]: received forwarded packet from [SbsJn] via [dM2E3]
derp client 10.0.1.1:50650[10WOo]: sendPkt attempt 0 enqueued
derp client 10.0.1.1:50650[10WOo]: sendPacket from [SbsJn]: <nil>
derp client 10.0.1.1:50650[10WOo]: read frame type 0 len 0 err EOF
derp client 10.0.1.1:50650[10WOo]: read EOF
derp client 10.0.1.1:50650[10WOo]: sender failed: context canceled
derp client 10.0.1.1:50650[10WOo]: removing connection
```

Signed-off-by: Anton Tolchanov <anton@tailscale.com>
pull/7619/head
Anton Tolchanov 2 years ago committed by Anton Tolchanov
parent 50d211d1a4
commit 654b5a0616
3 changed files with 43 additions and 4 deletions
Show Stats Download Patch File Download Diff File

39
derp/derp_server.go
Unescape Escape View File

@ -279,6 +279,7 @@ func (s *dupClientSet) removeClient(c *sclient) bool {
// public key gets more than one PacketForwarder registered for it.
type PacketForwarder interface {
ForwardPacket(src, dst key.NodePublic, payload []byte) error
String() string
}
// Conn is the subset of the underlying net.Conn the DERP Server needs.
@ -495,6 +496,7 @@ func (s *Server) registerClient(c *sclient) {
switch set := set.(type) {
case nil:
s.clients[c.key] = singleClient{c}
c.debug("register single client")
case singleClient:
s.dupClientKeys.Add(1)
s.dupClientConns.Add(2) // both old and new count
@ -510,6 +512,7 @@ func (s *Server) registerClient(c *sclient) {
},
sendHistory: []*sclient{old},
}
c.debug("register duplicate client")
case *dupClientSet:
s.dupClientConns.Add(1) // the gauge
s.dupClientConnTotal.Add(1) // the counter
@ -517,6 +520,7 @@ func (s *Server) registerClient(c *sclient) {
set.set[c] = true
set.last = c
set.sendHistory = append(set.sendHistory, c)
c.debug("register another duplicate client")
}
if _, ok := s.clientsMesh[c.key]; !ok {
@ -549,7 +553,7 @@ func (s *Server) unregisterClient(c *sclient) {
case nil:
c.logf("[unexpected]; clients map is empty")
case singleClient:
c.logf("removing connection")
c.logf("removed connection")
delete(s.clients, c.key)
if v, ok := s.clientsMesh[c.key]; ok && v == nil {
delete(s.clientsMesh, c.key)
@ -557,6 +561,7 @@ func (s *Server) unregisterClient(c *sclient) {
}
s.broadcastPeerStateChangeLocked(c.key, false)
case *dupClientSet:
c.debug("removed duplicate client")
if set.removeClient(c) {
s.dupClientConns.Add(-1)
} else {
@ -673,7 +678,7 @@ func (s *Server) accept(ctx context.Context, nc Conn, brw *bufio.ReadWriter, rem
nc: nc,
br: br,
bw: bw,
logf: logger.WithPrefix(s.logf, fmt.Sprintf("derp client %v/%x: ", remoteAddr, clientKey)),
logf: logger.WithPrefix(s.logf, fmt.Sprintf("derp client %v%s: ", remoteAddr, clientKey.ShortString())),
done: ctx.Done(),
remoteAddr: remoteAddr,
remoteIPPort: remoteIPPort,
@ -690,6 +695,9 @@ func (s *Server) accept(ctx context.Context, nc Conn, brw *bufio.ReadWriter, rem
}
if clientInfo != nil {
c.info = *clientInfo
if envknob.Bool("DERP_PROBER_DEBUG_LOGS") && clientInfo.IsProber {
c.debugLogging = true
}
}
s.registerClient(c)
@ -726,6 +734,7 @@ func (c *sclient) run(ctx context.Context) error {
for {
ft, fl, err := readFrameHeader(c.br)
c.debug("read frame type %d len %d err %v", ft, fl, err)
if err != nil {
if errors.Is(err, io.EOF) {
c.logf("read EOF")
@ -735,7 +744,7 @@ func (c *sclient) run(ctx context.Context) error {
c.logf("closing; server closed")
return nil
}
return fmt.Errorf("client %x: readFrameHeader: %w", c.key, err)
return fmt.Errorf("client %s: readFrameHeader: %w", c.key.ShortString(), err)
}
c.s.noteClientActivity(c)
switch ft {
@ -883,6 +892,8 @@ func (c *sclient) handleFrameForwardPacket(ft frameType, fl uint32) error {
return nil
}
dst.debug("received forwarded packet from %s via %s", srcKey.ShortString(), c.key.ShortString())
return c.sendPkt(dst, pkt{
bs: contents,
enqueuedAt: time.Now(),
@ -930,7 +941,9 @@ func (c *sclient) handleFrameSendPacket(ft frameType, fl uint32) error {
if dst == nil {
if fwd != nil {
s.packetsForwardedOut.Add(1)
if err := fwd.ForwardPacket(c.key, dstKey, contents); err != nil {
err := fwd.ForwardPacket(c.key, dstKey, contents)
c.debug("SendPacket for %s, forwarding via %s: %v", dstKey.ShortString(), fwd, err)
if err != nil {
// TODO:
return nil
}
@ -941,8 +954,10 @@ func (c *sclient) handleFrameSendPacket(ft frameType, fl uint32) error {
reason = dropReasonDupClient
}
s.recordDrop(contents, c.key, dstKey, reason)
c.debug("SendPacket for %s, dropping with reason=%s", dstKey.ShortString(), reason)
return nil
}
c.debug("SendPacket for %s, sending directly", dstKey.ShortString())
p := pkt{
bs: contents,
@ -952,6 +967,12 @@ func (c *sclient) handleFrameSendPacket(ft frameType, fl uint32) error {
return c.sendPkt(dst, p)
}
func (c *sclient) debug(format string, v ...any) {
if c.debugLogging {
c.logf(format, v...)
}
}
// dropReason is why we dropped a DERP frame.
type dropReason int
@ -1003,11 +1024,13 @@ func (c *sclient) sendPkt(dst *sclient, p pkt) error {
select {
case <-dst.done:
s.recordDrop(p.bs, c.key, dstKey, dropReasonGone)
dst.debug("sendPkt attempt %d dropped, dst gone", attempt)
return nil
default:
}
select {
case sendQueue <- p:
dst.debug("sendPkt attempt %d enqueued", attempt)
return nil
default:
}
@ -1023,6 +1046,7 @@ func (c *sclient) sendPkt(dst *sclient, p pkt) error {
// contended queue with racing writers. Give up and tail-drop in
// this case to keep reader unblocked.
s.recordDrop(p.bs, c.key, dstKey, dropReasonQueueTail)
dst.debug("sendPkt attempt %d dropped, queue full")
return nil
}
@ -1258,6 +1282,8 @@ type sclient struct {
isDup atomic.Bool // whether more than 1 sclient for key is connected
isDisabled atomic.Bool // whether sends to this peer are disabled due to active/active dups
debugLogging bool
// replaceLimiter controls how quickly two connections with
// the same client key can kick each other off the server by
// taking over ownership of a key.
@ -1529,6 +1555,7 @@ func (c *sclient) sendPacket(srcKey key.NodePublic, contents []byte) (err error)
c.s.packetsSent.Add(1)
c.s.bytesSent.Add(int64(len(contents)))
}
c.debug("sendPacket from %s: %v", srcKey.ShortString(), err)
}()
c.setWriteDeadline()
@ -1689,6 +1716,10 @@ func (f *multiForwarder) ForwardPacket(src, dst key.NodePublic, payload []byte)
return f.fwd.Load().ForwardPacket(src, dst, payload)
}
func (f *multiForwarder) String() string {
return fmt.Sprintf("<MultiForwarder fwd=%s total=%d>", f.fwd.Load(), len(f.all))
}
func (s *Server) expVarFunc(f func() any) expvar.Func {
return expvar.Func(func() any {
s.mu.Lock()

4
derp/derp_test.go
Unescape Escape View File

@ -660,6 +660,9 @@ type testFwd int
func (testFwd) ForwardPacket(key.NodePublic, key.NodePublic, []byte) error {
panic("not called in tests")
}
func (testFwd) String() string {
panic("not called in tests")
}
func pubAll(b byte) (ret key.NodePublic) {
var bs [32]byte
@ -787,6 +790,7 @@ type channelFwd struct {
c chan []byte
}
func (f channelFwd) String() string { return "" }
func (f channelFwd) ForwardPacket(_ key.NodePublic, _ key.NodePublic, packet []byte) error {
f.c <- packet
return nil

4
derp/derphttp/derphttp_client.go
Unescape Escape View File

@ -82,6 +82,10 @@ type Client struct {
pingOut map[derp.PingMessage]chan<- bool // chan to send to on pong
}
func (c *Client) String() string {
return fmt.Sprintf("<derphttp_client.Client %s url=%s>", c.serverPubKey.ShortString(), c.url)
}
// NewRegionClient returns a new DERP-over-HTTP client. It connects lazily.
// To trigger a connection, use Connect.
func NewRegionClient(privateKey key.NodePrivate, logf logger.Logf, getRegion func() *tailcfg.DERPRegion) *Client {

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