[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=