diff --git a/cmd/derper/derper.go b/cmd/derper/derper.go
index 02736b6be..373faa8b5 100644
--- a/cmd/derper/derper.go
+++ b/cmd/derper/derper.go
@@ -12,15 +12,19 @@ import (
"expvar"
"flag"
"fmt"
+ "html"
"io"
"log"
"math"
"net"
"net/http"
+ "net/http/pprof"
"net/netip"
"os"
"path/filepath"
"regexp"
+ "runtime"
+ "strconv"
"strings"
"time"
@@ -33,6 +37,7 @@ import (
"tailscale.com/net/stun"
"tailscale.com/tsweb"
"tailscale.com/types/key"
+ "tailscale.com/version"
)
var (
@@ -55,6 +60,8 @@ var (
acceptConnLimit = flag.Float64("accept-connection-limit", math.Inf(+1), "rate limit for accepting new connection")
acceptConnBurst = flag.Int("accept-connection-burst", math.MaxInt, "burst limit for accepting new connection")
+
+ debugAddr = flag.String("debug_addr", "", "listening address for debug server")
)
var (
@@ -136,6 +143,7 @@ func main() {
if *dev {
*addr = ":3340" // above the keys DERP
+ *debugAddr = "localhost:8383"
log.Printf("Running in dev mode.")
tsweb.DevMode = true
}
@@ -222,6 +230,11 @@ func main() {
go serveSTUN(listenHost, *stunPort)
}
+ if *debugAddr != "" {
+ log.Printf("running debug server on %s", *debugAddr)
+ go runDebugServer(*debugAddr, s)
+ }
+
quietLogger := log.New(logFilter{}, "", 0)
httpsrv := &http.Server{
Addr: *addr,
@@ -513,3 +526,79 @@ func (logFilter) Write(p []byte) (int, error) {
log.Printf("%s", p)
return len(p), nil
}
+
+func runDebugServer(addr string, s *derp.Server) {
+ mux := http.NewServeMux()
+ mux.Handle("/debug/vars", http.DefaultServeMux) // serve out expvar
+ mux.HandleFunc("/debug/varz", tsweb.VarzHandler) // expvar but in prometheus format
+ mux.HandleFunc("/debug/pprof/", pprof.Index)
+ mux.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
+ mux.HandleFunc("/debug/pprof/profile", pprof.Profile)
+ mux.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
+ mux.HandleFunc("/debug/pprof/trace", pprof.Trace)
+ mux.Handle("/debug/pprofrate", http.HandlerFunc(handlePprofRate))
+
+ mux.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+ w.Header().Set("Content-Type", "text/html; charset=utf-8")
+ w.WriteHeader(200)
+ fmt.Fprintf(w, `
+DERP
+
+ This is a Tailscale DERP debug server.
+
+
+`, html.EscapeString(version.Long()))
+ }))
+
+ srv := &http.Server{
+ Addr: addr,
+ Handler: mux,
+ }
+ if err := srv.ListenAndServe(); err != nil {
+ if err != http.ErrServerClosed {
+ log.Fatal(err)
+ }
+ }
+}
+
+// handlePprofRate adjusts the pprof rate.
+//
+// $ curl -d block=0 http://localhost:8383/debug/pprofrate
+// $ curl -d mutex=0 http://localhost:8383/debug/pprofrate
+//
+// See:
+//
+// - https://pkg.go.dev/runtime#SetMutexProfileFraction
+// - https://pkg.go.dev/runtime#SetBlockProfileRate
+//
+// And corp#5277.
+func handlePprofRate(w http.ResponseWriter, r *http.Request) {
+ if r.Method != "POST" {
+ http.Error(w, "method not allowed; want POST", http.StatusMethodNotAllowed)
+ return
+ }
+ if s := r.FormValue("block"); s != "" {
+ v, err := strconv.Atoi(s)
+ if err != nil {
+ http.Error(w, "bad block value", http.StatusBadRequest)
+ return
+ }
+ runtime.SetBlockProfileRate(v)
+ fmt.Fprintf(w, "block set to %v\n", v)
+ }
+ if s := r.FormValue("mutex"); s != "" {
+ v, err := strconv.Atoi(s)
+ if err != nil {
+ http.Error(w, "bad mutex value", http.StatusBadRequest)
+ return
+ }
+ old := runtime.SetMutexProfileFraction(v)
+ fmt.Fprintf(w, "mutex changed from %v to %v\n", old, v)
+ }
+}