log: use logtail to log and upload sockstat logs

Switch to using logtail for logging sockstat logs. Always log locally
(on supported platforms), but disable automatic uploading.  Change
existing c2n sockstats request to trigger upload to log server and
return log ID.

Signed-off-by: Will Norris <will@tailscale.com>

ipn/ipnlocal/c2n.go

@@ -84,8 +84,13 @@ func (b *LocalBackend) handleC2N(w http.ResponseWriter, r *http.Request) {
 		}
 		writeJSON(res)
 	case "/sockstats":
+		if r.Method != "POST" {
+			http.Error(w, "bad method", http.StatusMethodNotAllowed)
+			return
+		}
 		w.Header().Set("Content-Type", "text/plain")
-		b.sockstatLogger.WriteLogs(w)
+		b.sockstatLogger.Flush()
+		fmt.Fprintln(w, b.sockstatLogger.LogID())
 	default:
 		http.Error(w, "unknown c2n path", http.StatusBadRequest)
 	}

ipn/ipnlocal/local.go

@@ -310,7 +310,7 @@ func NewLocalBackend(logf logger.Logf, logid string, store ipn.StateStore, diale
 
 	// for now, only log sockstats on unstable builds
 	if version.IsUnstableBuild() {
-		b.sockstatLogger, err = sockstatlog.NewLogger(logpolicy.LogsDir(logf), logf)
+		b.sockstatLogger, err = sockstatlog.NewLogger(logpolicy.LogsDir(logf), logf, logid)
 		if err != nil {
 			log.Printf("error setting up sockstat logger: %v", err)
 		}