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tailscale/log/sockstatlog/logger.go

278 lines
7.9 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
// Package sockstatlog provides a logger for capturing network socket stats for debugging.
// Stats are collected at a frequency of 10 Hz and logged to disk.
// Stats are only uploaded to the log server on demand.
package sockstatlog
import (
"context"
"crypto/sha256"
"encoding/json"
"io"
"net/http"
"os"
"path/filepath"
"sync/atomic"
"time"
"tailscale.com/logpolicy"
"tailscale.com/logtail"
"tailscale.com/logtail/filch"
"tailscale.com/net/netmon"
"tailscale.com/net/sockstats"
"tailscale.com/smallzstd"
"tailscale.com/types/logger"
"tailscale.com/types/logid"
"tailscale.com/util/mak"
)
// pollInterval specifies how often to poll for socket stats.
const pollInterval = time.Second / 10
// logInterval specifies how often to log sockstat events to disk.
// This delay is added to prevent an infinite loop when logs are uploaded,
// which itself creates additional sockstat events.
const logInterval = 10 * time.Second
// maxLogFileSize specifies the maximum size of a log file before it is rotated.
// Our logs are fairly compact, and we are mostly only looking at a few hours of data.
// Combined with the fact that these are often uploaded over cellular connections,
// we keep this relatively small.
const maxLogFileSize = 5 << 20 // 5 MB
// Logger logs statistics about network sockets.
type Logger struct {
// enabled identifies whether the logger is enabled.
enabled atomic.Bool
ctx context.Context
cancelFn context.CancelFunc
// eventCh is used to pass events from the poller to the logger.
eventCh chan event
logf logger.Logf
// logger is the underlying logtail logger than manages log files on disk
// and uploading to the log server.
logger *logtail.Logger
filch *filch.Filch
tr http.RoundTripper
}
// deltaStat represents the bytes transferred during a time period.
// The first element is transmitted bytes, the second element is received bytes.
type deltaStat [2]uint64
// event represents the socket stats on a specific interface during a time period.
type event struct {
// Time is when the event started as a Unix timestamp in milliseconds.
Time int64 `json:"t"`
// Duration is the duration of this event in milliseconds.
Duration int64 `json:"d"`
// IsCellularInterface is set to 1 if the traffic was sent over a cellular interface.
IsCellularInterface int `json:"c,omitempty"`
// Stats records the stats for each Label during the time period.
Stats map[sockstats.Label]deltaStat `json:"s"`
}
// SockstatLogID reproducibly derives a new logid.PrivateID for sockstat logging from a node's public backend log ID.
// The returned PrivateID is the sha256 sum of logID + "sockstat".
// If a node's public log ID becomes known, it is trivial to spoof sockstat logs for that node.
// Given that this is just for debugging, we're not too concerned about that.
func SockstatLogID(logID logid.PublicID) logid.PrivateID {
return logid.PrivateID(sha256.Sum256([]byte(logID.String() + "sockstat")))
}
// NewLogger returns a new Logger that will store stats in logdir.
// On platforms that do not support sockstat logging, a nil Logger will be returned.
// The returned Logger is not yet enabled, and must be shut down with Shutdown when it is no longer needed.
// Logs will be uploaded to the log server using a new log ID derived from the provided backend logID.
// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
func NewLogger(logdir string, logf logger.Logf, logID logid.PublicID, netMon *netmon.Monitor) (*Logger, error) {
if !sockstats.IsAvailable {
return nil, nil
}
if err := os.MkdirAll(logdir, 0755); err != nil && !os.IsExist(err) {
return nil, err
}
filchPrefix := filepath.Join(logdir, "sockstats")
filch, err := filch.New(filchPrefix, filch.Options{
MaxFileSize: maxLogFileSize,
ReplaceStderr: false,
})
if err != nil {
return nil, err
}
logger := &Logger{
logf: logf,
filch: filch,
tr: logpolicy.NewLogtailTransport(logtail.DefaultHost, netMon, logf),
}
logger.logger = logtail.NewLogger(logtail.Config{
BaseURL: logpolicy.LogURL(),
PrivateID: SockstatLogID(logID),
Collection: "sockstats.log.tailscale.io",
Buffer: filch,
NewZstdEncoder: func() logtail.Encoder {
w, err := smallzstd.NewEncoder(nil)
if err != nil {
panic(err)
}
return w
},
FlushDelayFn: func() time.Duration {
// set flush delay to 100 years so it never flushes automatically
return 100 * 365 * 24 * time.Hour
},
Stderr: io.Discard, // don't log to stderr
HTTPC: &http.Client{Transport: logger.tr},
}, logf)
logger.logger.SetSockstatsLabel(sockstats.LabelSockstatlogLogger)
return logger, nil
}
// SetLoggingEnabled enables or disables logging.
// When disabled, socket stats are not polled and no new logs are written to disk.
// Existing logs can still be fetched via the C2N API.
func (l *Logger) SetLoggingEnabled(v bool) {
old := l.enabled.Load()
if old != v && l.enabled.CompareAndSwap(old, v) {
if v {
if l.eventCh == nil {
// eventCh should be large enough for the number of events that will occur within logInterval.
// Add an extra second's worth of events to ensure we don't drop any.
l.eventCh = make(chan event, (logInterval+time.Second)/pollInterval)
}
l.ctx, l.cancelFn = context.WithCancel(context.Background())
go l.poll()
go l.logEvents()
} else {
l.cancelFn()
}
}
}
func (l *Logger) Write(p []byte) (int, error) {
return l.logger.Write(p)
}
// poll fetches the current socket stats at the configured time interval,
// calculates the delta since the last poll,
// and writes any non-zero values to the logger event channel.
// This method does not return.
func (l *Logger) poll() {
// last is the last set of socket stats we saw.
var lastStats *sockstats.SockStats
var lastTime time.Time
ticker := time.NewTicker(pollInterval)
for {
select {
case <-l.ctx.Done():
ticker.Stop()
return
case t := <-ticker.C:
stats := sockstats.Get()
if lastStats != nil {
diffstats := delta(lastStats, stats)
if len(diffstats) > 0 {
e := event{
Time: lastTime.UnixMilli(),
Duration: t.Sub(lastTime).Milliseconds(),
Stats: diffstats,
}
if stats.CurrentInterfaceCellular {
e.IsCellularInterface = 1
}
l.eventCh <- e
}
}
lastTime = t
lastStats = stats
}
}
}
// logEvents reads events from the event channel at logInterval and logs them to disk.
// This method does not return.
func (l *Logger) logEvents() {
enc := json.NewEncoder(l)
flush := func() {
for {
select {
case e := <-l.eventCh:
if err := enc.Encode(e); err != nil {
l.logf("sockstatlog: error encoding log: %v", err)
}
default:
return
}
}
}
ticker := time.NewTicker(logInterval)
for {
select {
case <-l.ctx.Done():
ticker.Stop()
return
case <-ticker.C:
flush()
}
}
}
func (l *Logger) LogID() string {
if l.logger == nil {
return ""
}
return l.logger.PrivateID().Public().String()
}
// Flush sends pending logs to the log server and flushes them from the local buffer.
func (l *Logger) Flush() {
l.logger.StartFlush()
}
func (l *Logger) Shutdown() {
if l.cancelFn != nil {
l.cancelFn()
}
l.filch.Close()
l.logger.Shutdown(context.Background())
type closeIdler interface {
CloseIdleConnections()
}
if tr, ok := l.tr.(closeIdler); ok {
tr.CloseIdleConnections()
}
}
// delta calculates the delta stats between two SockStats snapshots.
// b is assumed to have occurred after a.
// Zero values are omitted from the returned map, and an empty map is returned if no bytes were transferred.
func delta(a, b *sockstats.SockStats) (stats map[sockstats.Label]deltaStat) {
if a == nil || b == nil {
return nil
}
for label, bs := range b.Stats {
as := a.Stats[label]
if as.TxBytes == bs.TxBytes && as.RxBytes == bs.RxBytes {
// fast path for unchanged stats
continue
}
mak.Set(&stats, label, deltaStat{bs.TxBytes - as.TxBytes, bs.RxBytes - as.RxBytes})
}
return stats
}