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derp: add a debug option to verbosely log drops to a destination.

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Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson 2020-08-12 21:51:21 +00:00 committed by Dave Anderson
parent 909c165382
commit 37c19970b3
1 changed files with 40 additions and 6 deletions
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46
derp/derp_server.go
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@ -16,6 +16,7 @@
"fmt"
"io"
"io/ioutil"
"log"
"math/big"
"os"
"runtime"
@ -24,6 +25,7 @@
"sync"
"time"
"go4.org/mem"
"golang.org/x/crypto/nacl/box"
"golang.org/x/sync/errgroup"
"tailscale.com/disco"
@ -35,6 +37,25 @@
var debug, _ = strconv.ParseBool(os.Getenv("DERP_DEBUG_LOGS"))
// verboseDropKeys is the set of destination public keys that should
// verbosely log whenever DERP drops a packet.
var verboseDropKeys = map[key.Public]bool{}
func init() {
keys := os.Getenv("TS_DEBUG_VERBOSE_DROPS")
if keys == "" {
return
}
for _, keyStr := range strings.Split(keys, ",") {
k, err := key.NewPublicFromHexMem(mem.S(keyStr))
if err != nil {
log.Printf("ignoring invalid debug key %q: %v", keyStr, err)
} else {
verboseDropKeys[k] = true
}
}
}
const (
perClientSendQueueDepth = 32 // packets buffered for sending
writeTimeout = 2 * time.Second
@ -53,14 +74,14 @@ type Server struct {
// before failing when writing to a client.
WriteTimeout time.Duration
privateKey key.Private
publicKey key.Public
logf logger.Logf
memSys0 uint64 // runtime.MemStats.Sys at start (or early-ish)
meshKey string
privateKey key.Private
publicKey key.Public
logf logger.Logf
memSys0 uint64 // runtime.MemStats.Sys at start (or early-ish)
meshKey string
limitedLogf logger.Logf
// Counters:
_ [pad32bit]byte
packetsSent, bytesSent expvar.Int
packetsRecv, bytesRecv expvar.Int
packetsRecvByKind metrics.LabelMap
@ -141,6 +162,7 @@ func NewServer(privateKey key.Private, logf logger.Logf) *Server {
privateKey: privateKey,
publicKey: privateKey.Public(),
logf: logf,
limitedLogf: logger.RateLimitedFn(logf, 30*time.Second, 5, 100),
packetsRecvByKind: metrics.LabelMap{Label: "kind"},
packetsDroppedReason: metrics.LabelMap{Label: "reason"},
clients: map[key.Public]*sclient{},
@ -624,6 +646,12 @@ func (c *sclient) sendPkt(dst *sclient, p pkt) error {
case <-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)
}
if debug {
c.logf("dropping packet from client %x queue head", dstKey)
}
@ -635,6 +663,12 @@ func (c *sclient) sendPkt(dst *sclient, p pkt) error {
// 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)
}