all: Send deadlocks as failures, crash only as a last resort (#7785)

cmd/stcrashreceiver/util.go

@@ -0,0 +1,57 @@
+// Copyright (C) 2021 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+package main
+
+import (
+	"bytes"
+	"compress/gzip"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"path/filepath"
+	"time"
+
+	"github.com/syncthing/syncthing/lib/sha256"
+)
+
+// userIDFor returns a string we can use as the user ID for the purpose of
+// counting affected users. It's the truncated hash of a salt, the user
+// remote IP, and the current month.
+func userIDFor(req *http.Request) string {
+	addr := req.RemoteAddr
+	if fwd := req.Header.Get("x-forwarded-for"); fwd != "" {
+		addr = fwd
+	}
+	if host, _, err := net.SplitHostPort(addr); err == nil {
+		addr = host
+	}
+	now := time.Now().Format("200601")
+	salt := "stcrashreporter"
+	hash := sha256.Sum256([]byte(salt + addr + now))
+	return fmt.Sprintf("%x", hash[:8])
+}
+
+// 01234567890abcdef... => 01/23
+func dirFor(base string) string {
+	return filepath.Join(base[0:2], base[2:4])
+}
+
+func fullPathCompressed(root, reportID string) string {
+	return filepath.Join(root, dirFor(reportID), reportID) + ".gz"
+}
+
+func compressAndWrite(bs []byte, fullPath string) error {
+	// Compress the report for storage
+	buf := new(bytes.Buffer)
+	gw := gzip.NewWriter(buf)
+	_, _ = gw.Write(bs) // can't fail
+	gw.Close()
+
+	// Create an output file with the compressed report
+	return ioutil.WriteFile(fullPath, buf.Bytes(), 0644)
+}