From 8eba042cd8f6feac8839cc82c24f43453f6bfa7b Mon Sep 17 00:00:00 2001
From: Florian Lehner <dev@der-flo.net>
Date: Sat, 14 Aug 2021 09:31:24 +0200
Subject: [PATCH] avoid checking read timeouts continuously

Signed-off-by: Florian Lehner <dev@der-flo.net>
---
 nflog.go | 32 ++++++++++++++------------------
 types.go |  4 ++++
 2 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/nflog.go b/nflog.go
index f526fc6..6d297a6 100644
--- a/nflog.go
+++ b/nflog.go
@@ -20,14 +20,13 @@ type Nflog struct {
 
 	logger *log.Logger
 
-	flags          []byte //uint16
-	bufsize        []byte //uint32
-	qthresh        []byte //uint32
-	timeout        []byte //uint32
-	group          uint16
-	copyMode       uint8
-	settings       uint16
-	setReadTimeout func() error
+	flags    []byte //uint16
+	bufsize  []byte //uint32
+	qthresh  []byte //uint32
+	timeout  []byte //uint32
+	group    uint16
+	copyMode uint8
+	settings uint16
 }
 
 // devNull satisfies io.Writer, in case *log.Logger is not provided
@@ -94,15 +93,6 @@ func Open(config *Config) (*Nflog, error) {
 	nflog.copyMode = config.Copymode
 	nflog.settings = config.Settings
 
-	if config.ReadTimeout > 0 {
-		nflog.setReadTimeout = func() error {
-			deadline := time.Now().Add(config.ReadTimeout)
-			return nflog.Con.SetReadDeadline(deadline)
-		}
-	} else {
-		nflog.setReadTimeout = func() error { return nil }
-	}
-
 	return &nflog, nil
 }
 
@@ -219,12 +209,18 @@ func (nflog *Nflog) RegisterWithErrorFunc(ctx context.Context, fn HookFunc, errf
 				return
 			}
 		}()
+		go func() {
+			// block until context is done
+			<-ctx.Done()
+			// Set the read deadline to a point in the past to interrupt
+			// possible blocking Receive() calls.
+			nflog.Con.SetReadDeadline(time.Now().Add(-1 * time.Second))
+		}()
 		for {
 			if err := ctx.Err(); err != nil {
 				nflog.logger.Printf("Stop receiving nflog messages: %v", err)
 				return
 			}
-			nflog.setReadTimeout()
 			reply, err := nflog.Con.Receive()
 			if err != nil {
 				if ret := errfn(err); ret != 0 {
diff --git a/types.go b/types.go
index f3fa09e..db3ad75 100644
--- a/types.go
+++ b/types.go
@@ -142,6 +142,10 @@ type Config struct {
 	Settings uint16
 
 	// Time till a read action times out - only available for Go >= 1.12
+	//
+	// Deprecated: Cancel the context passed to RegisterWithErrorFunc() or Register()
+	// to remove the hook from the nfloq gracefully. Setting this value does no longer
+	// have an effect on nflog.
 	ReadTimeout time.Duration
 
 	// Interface to log internals.