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derp: add counters to track the type of dropped packets.

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Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson 2021-07-12 13:05:55 -07:00 committed by Dave Anderson
parent 1072397375
commit 36492ace9d
3 changed files with 114 additions and 85 deletions
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166
derp/derp_server.go
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@ -97,36 +97,34 @@ type Server struct {
metaCert []byte // the encoded x509 cert to send after LetsEncrypt cert+intermediate
// Counters:
_ [pad32bit]byte
packetsSent, bytesSent expvar.Int
packetsRecv, bytesRecv expvar.Int
packetsRecvByKind metrics.LabelMap
packetsRecvDisco *expvar.Int
packetsRecvOther *expvar.Int
_ [pad32bit]byte
packetsDropped expvar.Int
packetsDroppedReason metrics.LabelMap
packetsDroppedUnknown *expvar.Int // unknown dst pubkey
packetsDroppedFwdUnknown *expvar.Int // unknown dst pubkey on forward
packetsDroppedGone *expvar.Int // dst conn shutting down
packetsDroppedQueueHead *expvar.Int // queue full, drop head packet
packetsDroppedQueueTail *expvar.Int // queue full, drop tail packet
packetsDroppedWrite *expvar.Int // error writing to dst conn
_ [pad32bit]byte
packetsForwardedOut expvar.Int
packetsForwardedIn expvar.Int
peerGoneFrames expvar.Int // number of peer gone frames sent
accepts expvar.Int
curClients expvar.Int
curHomeClients expvar.Int // ones with preferred
clientsReplaced expvar.Int
unknownFrames expvar.Int
homeMovesIn expvar.Int // established clients announce home server moves in
homeMovesOut expvar.Int // established clients announce home server moves out
multiForwarderCreated expvar.Int
multiForwarderDeleted expvar.Int
removePktForwardOther expvar.Int
avgQueueDuration *uint64 // In milliseconds; accessed atomically
_ [pad32bit]byte
packetsSent, bytesSent expvar.Int
packetsRecv, bytesRecv expvar.Int
packetsRecvByKind metrics.LabelMap
packetsRecvDisco *expvar.Int
packetsRecvOther *expvar.Int
_ [pad32bit]byte
packetsDropped expvar.Int
packetsDroppedReason metrics.LabelMap
packetsDroppedReasonCounters []*expvar.Int // indexed by dropReason
packetsDroppedType metrics.LabelMap
packetsDroppedTypeDisco *expvar.Int
packetsDroppedTypeOther *expvar.Int
_ [pad32bit]byte
packetsForwardedOut expvar.Int
packetsForwardedIn expvar.Int
peerGoneFrames expvar.Int // number of peer gone frames sent
accepts expvar.Int
curClients expvar.Int
curHomeClients expvar.Int // ones with preferred
clientsReplaced expvar.Int
unknownFrames expvar.Int
homeMovesIn expvar.Int // established clients announce home server moves in
homeMovesOut expvar.Int // established clients announce home server moves out
multiForwarderCreated expvar.Int
multiForwarderDeleted expvar.Int
removePktForwardOther expvar.Int
avgQueueDuration *uint64 // In milliseconds; accessed atomically
// verifyClients only accepts client connections to the DERP server if the clientKey is a
// known peer in the network, as specified by a running tailscaled's client's local api.
@ -189,6 +187,7 @@ func NewServer(privateKey key.Private, logf logger.Logf) *Server {
limitedLogf: logger.RateLimitedFn(logf, 30*time.Second, 5, 100),
packetsRecvByKind: metrics.LabelMap{Label: "kind"},
packetsDroppedReason: metrics.LabelMap{Label: "reason"},
packetsDroppedType: metrics.LabelMap{Label: "type"},
clients: map[key.Public]*sclient{},
clientsEver: map[key.Public]bool{},
clientsMesh: map[key.Public]PacketForwarder{},
@ -202,12 +201,16 @@ func NewServer(privateKey key.Private, logf logger.Logf) *Server {
s.initMetacert()
s.packetsRecvDisco = s.packetsRecvByKind.Get("disco")
s.packetsRecvOther = s.packetsRecvByKind.Get("other")
s.packetsDroppedUnknown = s.packetsDroppedReason.Get("unknown_dest")
s.packetsDroppedFwdUnknown = s.packetsDroppedReason.Get("unknown_dest_on_fwd")
s.packetsDroppedGone = s.packetsDroppedReason.Get("gone")
s.packetsDroppedQueueHead = s.packetsDroppedReason.Get("queue_head")
s.packetsDroppedQueueTail = s.packetsDroppedReason.Get("queue_tail")
s.packetsDroppedWrite = s.packetsDroppedReason.Get("write_error")
s.packetsDroppedReasonCounters = []*expvar.Int{
s.packetsDroppedReason.Get("unknown_dest"),
s.packetsDroppedReason.Get("unknown_dest_on_fwd"),
s.packetsDroppedReason.Get("gone"),
s.packetsDroppedReason.Get("queue_head"),
s.packetsDroppedReason.Get("queue_tail"),
s.packetsDroppedReason.Get("write_error"),
}
s.packetsDroppedTypeDisco = s.packetsDroppedType.Get("disco")
s.packetsDroppedTypeOther = s.packetsDroppedType.Get("other")
return s
}
@ -631,11 +634,7 @@ func (c *sclient) handleFrameForwardPacket(ft frameType, fl uint32) error {
s.mu.Unlock()
if dst == nil {
s.packetsDropped.Add(1)
s.packetsDroppedFwdUnknown.Add(1)
if debug {
c.logf("dropping forwarded packet for unknown %x", dstKey)
}
s.recordDrop(contents, srcKey, dstKey, dropReasonUnknownDestOnFwd)
return nil
}
@ -686,11 +685,7 @@ func (c *sclient) handleFrameSendPacket(ft frameType, fl uint32) error {
}
return nil
}
s.packetsDropped.Add(1)
s.packetsDroppedUnknown.Add(1)
if debug {
c.logf("dropping packet for unknown %x", dstKey)
}
s.recordDrop(contents, c.key, dstKey, dropReasonUnknownDest)
return nil
}
@ -702,6 +697,41 @@ func (c *sclient) handleFrameSendPacket(ft frameType, fl uint32) error {
return c.sendPkt(dst, p)
}
// dropReason is why we dropped a DERP frame.
type dropReason int
//go:generate stringer -type=dropReason -trimprefix=dropReason
const (
dropReasonUnknownDest dropReason = iota // unknown destination pubkey
dropReasonUnknownDestOnFwd // unknown destination pubkey on a derp-forwarded packet
dropReasonGone // destination tailscaled disconnected before we could send
dropReasonQueueHead // destination queue is full, dropped packet at queue head
dropReasonQueueTail // destination queue is full, dropped packet at queue tail
dropReasonWriteError // OS write() failed
)
func (s *Server) recordDrop(packetBytes []byte, srcKey, dstKey key.Public, reason dropReason) {
s.packetsDropped.Add(1)
s.packetsDroppedReasonCounters[reason].Add(1)
if disco.LooksLikeDiscoWrapper(packetBytes) {
s.packetsDroppedTypeDisco.Add(1)
} else {
s.packetsDroppedTypeOther.Add(1)
}
if verboseDropKeys[dstKey] {
// Preformat the log string prior to calling limitedLogf. The
// limiter acts based on the format string, and we want to
// rate-limit per src/dst keys, not on the generic "dropped
// stuff" message.
msg := fmt.Sprintf("drop (%s) %s -> %s", srcKey.ShortString(), reason, dstKey.ShortString())
s.limitedLogf(msg)
}
if debug {
s.logf("dropping packet reason=%s dst=%s disco=%v", reason, dstKey, disco.LooksLikeDiscoWrapper(packetBytes))
}
}
func (c *sclient) sendPkt(dst *sclient, p pkt) error {
s := c.s
dstKey := dst.key
@ -712,11 +742,7 @@ func (c *sclient) sendPkt(dst *sclient, p pkt) error {
for attempt := 0; attempt < 3; attempt++ {
select {
case <-dst.done:
s.packetsDropped.Add(1)
s.packetsDroppedGone.Add(1)
if debug {
c.logf("dropping packet for shutdown client %x", dstKey)
}
s.recordDrop(p.bs, c.key, dstKey, dropReasonGone)
return nil
default:
}
@ -728,35 +754,15 @@ func (c *sclient) sendPkt(dst *sclient, p pkt) error {
select {
case pkt := <-dst.sendQueue:
s.packetsDropped.Add(1)
s.packetsDroppedQueueHead.Add(1)
if verboseDropKeys[dstKey] {
// Generate a full string including src and dst, so
// the limiter kicks in once per src.
msg := fmt.Sprintf("tail drop %s -> %s", p.src.ShortString(), dstKey.ShortString())
c.s.limitedLogf(msg)
}
s.recordDrop(pkt.bs, c.key, dstKey, dropReasonQueueHead)
c.recordQueueTime(pkt.enqueuedAt)
if debug {
c.logf("dropping packet from client %x queue head", dstKey)
}
default:
}
}
// Failed to make room for packet. This can happen in a heavily
// contended queue with racing writers. Give up and tail-drop in
// this case to keep reader unblocked.
s.packetsDropped.Add(1)
s.packetsDroppedQueueTail.Add(1)
if verboseDropKeys[dstKey] {
// Generate a full string including src and dst, so
// the limiter kicks in once per src.
msg := fmt.Sprintf("head drop %s -> %s", p.src.ShortString(), dstKey.ShortString())
c.s.limitedLogf(msg)
}
if debug {
c.logf("dropping packet from client %x queue tail", dstKey)
}
s.recordDrop(p.bs, c.key, dstKey, dropReasonQueueTail)
return nil
}
@ -1031,12 +1037,8 @@ func (c *sclient) sendLoop(ctx context.Context) error {
// Drain the send queue to count dropped packets
for {
select {
case <-c.sendQueue:
c.s.packetsDropped.Add(1)
c.s.packetsDroppedGone.Add(1)
if debug {
c.logf("dropping packet for shutdown %x", c.key)
}
case pkt := <-c.sendQueue:
c.s.recordDrop(pkt.bs, pkt.src, c.key, dropReasonGone)
default:
return
}
@ -1179,11 +1181,7 @@ func (c *sclient) sendPacket(srcKey key.Public, contents []byte) (err error) {
defer func() {
// Stats update.
if err != nil {
c.s.packetsDropped.Add(1)
c.s.packetsDroppedWrite.Add(1)
if debug {
c.logf("dropping packet to %x: %v", c.key, err)
}
c.s.recordDrop(contents, srcKey, c.key, dropReasonWriteError)
} else {
c.s.packetsSent.Add(1)
c.s.bytesSent.Add(int64(len(contents)))

28
derp/dropreason_string.go Normal file
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@ -0,0 +1,28 @@
// Code generated by "stringer -type=dropReason -trimprefix=dropReason"; DO NOT EDIT.
package derp
import "strconv"
func _() {
// An "invalid array index" compiler error signifies that the constant values have changed.
// Re-run the stringer command to generate them again.
var x [1]struct{}
_ = x[dropReasonUnknownDest-0]
_ = x[dropReasonUnknownDestOnFwd-1]
_ = x[dropReasonGone-2]
_ = x[dropReasonQueueHead-3]
_ = x[dropReasonQueueTail-4]
_ = x[dropReasonWriteError-5]
}
const _dropReason_name = "UnknownDestUnknownDestOnFwdGoneQueueHeadQueueTailWriteError"
var _dropReason_index = [...]uint8{0, 11, 27, 31, 40, 49, 59}
func (i dropReason) String() string {
if i < 0 || i >= dropReason(len(_dropReason_index)-1) {
return "dropReason(" + strconv.FormatInt(int64(i), 10) + ")"
}
return _dropReason_name[_dropReason_index[i]:_dropReason_index[i+1]]
}

5
scripts/check_license_headers.sh
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@ -37,7 +37,10 @@ for file in $(find $1 -name '*.go' -not -path '*/.git/*'); do
;;
$1/wgengine/router/ifconfig_windows.go)
# WireGuard copyright.
;;
;;
*_string.go)
# Generated file from go:generate stringer
;;
*)
header="$(head -3 $file)"
if ! check_file "$header"; then