From 6f69fb73af7901b52a4717833de8554069c0b43b Mon Sep 17 00:00:00 2001
From: Simon Zolin <s.zolin@adguard.com>
Date: Tue, 5 Mar 2019 18:04:49 +0300
Subject: [PATCH] * control: safely restart DHCP server

* control: use mutex in all POST,PUT,DELETE handlers
---
 control.go |  3 +++
 dhcp.go    | 12 ++++++------
 helpers.go |  6 ++++++
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/control.go b/control.go
index 0cd9d504..0bd7a5d7 100644
--- a/control.go
+++ b/control.go
@@ -12,6 +12,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/AdguardTeam/AdGuardHome/dnsforward"
@@ -36,6 +37,8 @@ var client = &http.Client{
 	Timeout: time.Second * 30,
 }
 
+var controlLock sync.Mutex
+
 // ----------------
 // helper functions
 // ----------------
diff --git a/dhcp.go b/dhcp.go
index fe780305..58a3f161 100644
--- a/dhcp.go
+++ b/dhcp.go
@@ -50,6 +50,11 @@ func handleDHCPSetConfig(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	err = dhcpServer.Stop()
+	if err != nil {
+		log.Error("failed to stop the DHCP server: %s", err)
+	}
+
 	if newconfig.Enabled {
 		err := dhcpServer.Start(&newconfig)
 		if err != nil {
@@ -57,12 +62,7 @@ func handleDHCPSetConfig(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 	}
-	if !newconfig.Enabled {
-		err := dhcpServer.Stop()
-		if err != nil {
-			log.Error("failed to stop the DHCP server: %s", err)
-		}
-	}
+
 	config.DHCP = newconfig
 	httpUpdateConfigReloadDNSReturnOK(w, r)
 }
diff --git a/helpers.go b/helpers.go
index 25e35205..9d02ad3c 100644
--- a/helpers.go
+++ b/helpers.go
@@ -27,6 +27,12 @@ func ensure(method string, handler func(http.ResponseWriter, *http.Request)) fun
 			http.Error(w, "This request must be "+method, http.StatusMethodNotAllowed)
 			return
 		}
+
+		if method == "POST" || method == "PUT" || method == "DELETE" {
+			controlLock.Lock()
+			defer controlLock.Unlock()
+		}
+
 		handler(w, r)
 	}
 }