[Filebeat] Fix reference leak in TCP and Unix socket inputs (#19459)

The tcp and unix input sources were leaking references causing a memory leak.
When an accepted connection ended inputsource/common.Closer was
supposed to delete the pointer that it held to the connection, but due to a code
error `delete` was being called on the wrong map.

Instead of modifying the common.Closer I replaced it with a cancellable context.Context which
is designed to propagate signals from parent to children and requires less code.

CHANGELOG.next.asciidoc

@@ -196,6 +196,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Fix `netflow` module to support 7 bytepad for IPFIX template. {issue}18098[18098]
 - Fix Cisco ASA dissect pattern for 313008 & 313009 messages. {pull}19149[19149]
 - Fix date and timestamp formats for fortigate module {pull}19316[19316]
+- Fix memory leak in tcp and unix input sources. {pull}19459[19459]
 
 *Heartbeat*
 

filebeat/inputsource/common/handler.go

@@ -19,6 +19,7 @@ package common
 
 import (
  "bufio"
+ "context"
  "net"
 
  "github.com/pkg/errors"
@@ -31,15 +32,15 @@ import (
 type HandlerFactory func(config ListenerConfig) ConnectionHandler
 
 // ConnectionHandler interface provides mechanisms for handling of incoming connections
-type ConnectionHandler func(CloseRef, net.Conn) error
+type ConnectionHandler func(context.Context, net.Conn) error
 
 // MetadataFunc defines callback executed when a line is read from the split handler.
 type MetadataFunc func(net.Conn) inputsource.NetworkMetadata
 
 // SplitHandlerFactory allows creation of a handler that has splitting capabilities.
 func SplitHandlerFactory(family Family, logger *logp.Logger, metadataCallback MetadataFunc, callback inputsource.NetworkFunc, splitFunc bufio.SplitFunc) HandlerFactory {
  return func(config ListenerConfig) ConnectionHandler {
- return ConnectionHandler(func(closer CloseRef, conn net.Conn) error {
+ return ConnectionHandler(func(ctx context.Context, conn net.Conn) error {
  metadata := metadataCallback(conn)
  maxMessageSize := uint64(config.MaxMessageSize)
 
@@ -60,16 +61,11 @@ func SplitHandlerFactory(family Family, logger *logp.Logger, metadataCallback Me
  scanner.Buffer(buffer, int(maxMessageSize))
  for {
  select {
- case <-closer.Done():
+ case <-ctx.Done():
  break
  default:
  }
 
- // Ensure that if the Conn is already closed then dont attempt to scan again
- if closer.Err() == ErrClosed {
- break
- }
-
  if !scanner.Scan() {
  break
  }

filebeat/inputsource/common/listener.go

@@ -20,12 +20,14 @@ package common
 import (
  "bufio"
  "bytes"
+ "context"
  "net"
  "strings"
  "sync"
 
  "github.com/elastic/beats/v7/libbeat/common/atomic"
  "github.com/elastic/beats/v7/libbeat/logp"
+ "github.com/elastic/go-concert/ctxtool"
 )
 
 // Family represents the type of connection we're handling
@@ -51,9 +53,9 @@ type Listener struct {
  config *ListenerConfig
  family Family
  wg sync.WaitGroup
- done chan struct{}
  log *logp.Logger
- closer *Closer
+ ctx context.Context
+ cancel context.CancelFunc
  clientsCount atomic.Int
  handlerFactory HandlerFactory
  listenerFactory ListenerFactory
@@ -63,10 +65,8 @@ type Listener struct {
 func NewListener(family Family, location string, handlerFactory HandlerFactory, listenerFactory ListenerFactory, config *ListenerConfig) *Listener {
  return &Listener{
  config: config,
- done: make(chan struct{}),
  family: family,
  log: logp.NewLogger(string(family)).With("address", location),
- closer: NewCloser(nil),
  handlerFactory: handlerFactory,
  listenerFactory: listenerFactory,
  }
@@ -80,7 +80,12 @@ func (l *Listener) Start() error {
  return err
  }
 
- l.closer.SetCallback(func() { l.Listener.Close() })
+ l.ctx, l.cancel = context.WithCancel(context.Background())
+ go func() {
+ <-l.ctx.Done()
+ l.Listener.Close()
+ }()
+
  l.log.Info("Started listening for " + l.family.String() + " connection")
 
  l.wg.Add(1)
@@ -101,22 +106,21 @@ func (l *Listener) run() {
  conn, err := l.Listener.Accept()
  if err != nil {
  select {
- case <-l.closer.Done():
+ case <-l.ctx.Done():
  return
  default:
  l.log.Debugw("Can not accept the connection", "error", err)
  continue
  }
  }
 
- handler := l.handlerFactory(*l.config)
- closer := WithCloser(l.closer, func() { conn.Close() })
-
  l.wg.Add(1)
  go func() {
  defer logp.Recover("recovering from a " + l.family.String() + " client crash")
  defer l.wg.Done()
- defer closer.Close()
+
+ ctx, cancel := ctxtool.WithFunc(l.ctx, func() { conn.Close() })
+ defer cancel()
 
  l.registerHandler()
  defer l.unregisterHandler()
@@ -128,7 +132,8 @@ func (l *Listener) run() {
  l.log.Debugw("New client", "remote_address", conn.RemoteAddr(), "total", l.clientsCount.Load())
  }
 
- err := handler(closer, conn)
+ handler := l.handlerFactory(*l.config)
+ err := handler(ctx, conn)
  if err != nil {
  l.log.Debugw("client error", "error", err)
  }
@@ -148,7 +153,7 @@ func (l *Listener) run() {
 // Stop stops accepting new incoming connections and Close any active clients
 func (l *Listener) Stop() {
  l.log.Info("Stopping" + l.family.String() + "server")
- l.closer.Close()
+ l.cancel()
  l.wg.Wait()
  l.log.Info(l.family.String() + " server stopped")
 }

go.sum

@@ -727,6 +727,7 @@ go.opencensus.io v0.22.2 h1:75k/FF0Q2YM8QYo07VPddOLBslDt1MZOdEslOHvmzAs=
 go.opencensus.io v0.22.2/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.uber.org/atomic v1.5.0 h1:OI5t8sDa1Or+q8AeE+yKeB/SDYioSHAgcVljj9JIETY=
 go.uber.org/atomic v1.5.0/go.mod h1:sABNBOSYdrvTF6hTgEIbc7YasKWGhgEQZyfxyTvoXHQ=
+go.uber.org/goleak v1.0.0 h1:qsup4IcBdlmsnGfqyLl4Ntn3C2XCCuKAE7DwHpScyUo=
 go.uber.org/goleak v1.0.0/go.mod h1:8a7PlsEVH3e/a/GLqe5IIrQx6GzcnRmZEufDUTk4A7A=
 go.uber.org/multierr v1.3.0 h1:sFPn2GLc3poCkfrpIXGhBD2X0CMIo4Q/zSULXrj/+uc=
 go.uber.org/multierr v1.3.0/go.mod h1:VgVr7evmIr6uPjLBxg28wmKNXyqE9akIJ5XnfpiKl+4=