From 99c8c801eb1fcacb63ec56c6f03657be0b72587d Mon Sep 17 00:00:00 2001
From: Daniel <dhaavi@users.noreply.github.com>
Date: Mon, 29 Mar 2021 13:45:50 +0200
Subject: [PATCH] Switch to flag based cache validation

---
 netenv/environment_linux.go | 39 ++++++++++++-------------------------
 netenv/network-change.go    | 15 ++++++++++++--
 2 files changed, 25 insertions(+), 29 deletions(-)

diff --git a/netenv/environment_linux.go b/netenv/environment_linux.go
index 31297de1..42f02750 100644
--- a/netenv/environment_linux.go
+++ b/netenv/environment_linux.go
@@ -7,7 +7,6 @@ import (
 	"os"
 	"strings"
 	"sync"
-	"time"
 
 	"github.com/miekg/dns"
 
@@ -15,35 +14,25 @@ import (
 	"github.com/safing/portmaster/network/netutils"
 )
 
-const (
-	gatewaysRecheck    = 2 * time.Second
-	nameserversRecheck = 2 * time.Second
-)
-
 var (
-	gateways        = make([]net.IP, 0)
-	gatewaysLock    sync.Mutex
-	gatewaysExpires = time.Now()
+	gateways                   = make([]net.IP, 0)
+	gatewaysLock               sync.Mutex
+	gatewaysNetworkChangedFlag = GetNetworkChangedFlag()
 
-	nameservers        = make([]Nameserver, 0)
-	nameserversLock    sync.Mutex
-	nameserversExpires = time.Now()
+	nameservers                   = make([]Nameserver, 0)
+	nameserversLock               sync.Mutex
+	nameserversNetworkChangedFlag = GetNetworkChangedFlag()
 )
 
 // Gateways returns the currently active gateways.
 func Gateways() []net.IP {
-	// locking
 	gatewaysLock.Lock()
 	defer gatewaysLock.Unlock()
-	// cache
-	if gatewaysExpires.After(time.Now()) {
+	// Check if the network changed, if not, return cache.
+	if !gatewaysNetworkChangedFlag.IsSet() {
 		return gateways
 	}
-	// update cache expiry when finished
-	defer func() {
-		gatewaysExpires = time.Now().Add(gatewaysRecheck)
-	}()
-	// logic
+	gatewaysNetworkChangedFlag.Refresh()
 
 	gateways = make([]net.IP, 0)
 	var decoded []byte
@@ -119,17 +108,13 @@ func Gateways() []net.IP {
 
 // Nameservers returns the currently active nameservers.
 func Nameservers() []Nameserver {
-	// locking
 	nameserversLock.Lock()
 	defer nameserversLock.Unlock()
-	// cache
-	if nameserversExpires.After(time.Now()) {
+	// Check if the network changed, if not, return cache.
+	if !nameserversNetworkChangedFlag.IsSet() {
 		return nameservers
 	}
-	// update cache expiry when finished
-	defer func() {
-		nameserversExpires = time.Now().Add(nameserversRecheck)
-	}()
+	nameserversNetworkChangedFlag.Refresh()
 
 	// logic
 	// TODO: try:
diff --git a/netenv/network-change.go b/netenv/network-change.go
index 63f9b066..19a56085 100644
--- a/netenv/network-change.go
+++ b/netenv/network-change.go
@@ -9,12 +9,23 @@ import (
 	"time"
 
 	"github.com/safing/portbase/log"
+	"github.com/safing/portbase/utils"
 )
 
 var (
-	networkChangeCheckTrigger = make(chan struct{}, 1)
+	networkChangeCheckTrigger    = make(chan struct{}, 1)
+	networkChangedFlagController = utils.NewFlagController()
 )
 
+func GetNetworkChangedFlag() *utils.Flag {
+	return networkChangedFlagController.NewFlag()
+}
+
+func notifyOfNetworkChange() {
+	networkChangedFlagController.NotifyAndReset()
+	module.TriggerEvent(NetworkChangedEvent, nil)
+}
+
 func triggerNetworkChangeCheck() {
 	select {
 	case networkChangeCheckTrigger <- struct{}{}:
@@ -82,7 +93,7 @@ serviceLoop:
 			if trigger {
 				triggerOnlineStatusInvestigation()
 			}
-			module.TriggerEvent(NetworkChangedEvent, nil)
+			notifyOfNetworkChange()
 		}
 
 	}