From f8b3f53fa0c4f03d526a991945f7c6f3c454d43b Mon Sep 17 00:00:00 2001
From: Christopher Young <cyoung@gmail.com>
Date: Fri, 21 Aug 2015 04:24:51 -0400
Subject: [PATCH] merge inotify changes from @haykinson.

---
 network.go | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/network.go b/network.go
index 0b0b83b9..3a805b17 100644
--- a/network.go
+++ b/network.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"golang.org/x/exp/inotify"
 	"io/ioutil"
 	"log"
 	"net"
@@ -30,11 +31,12 @@ var netMutex *sync.Mutex
 const (
 	NETWORK_GDL90 = 1
 	NETWORK_AHRS  = 2
+	dhcp_lease_file = "/var/lib/dhcp/dhcpd.leases"
 )
 
 // Read the "dhcpd.leases" file and parse out IP/hostname.
 func getDHCPLeases() (map[string]string, error) {
-	dat, err := ioutil.ReadFile("/var/lib/dhcp/dhcpd.leases")
+	dat, err := ioutil.ReadFile(dhcp_lease_file)
 	ret := make(map[string]string)
 	if err != nil {
 		return ret, err
@@ -115,15 +117,12 @@ func refreshConnectedClients() {
 
 func messageQueueSender() {
 	secondTimer := time.NewTicker(1 * time.Second)
-	dhcpRefresh := time.NewTicker(30 * time.Second)
 	for {
 		select {
 		case msg := <-messageQueue:
 			sendToAllConnectedClients(msg)
 		case <-secondTimer.C:
 			getNetworkStats()
-		case <-dhcpRefresh.C:
-			refreshConnectedClients()
 		}
 	}
 }
@@ -136,10 +135,31 @@ func sendGDL90(msg []byte) {
 	sendMsg(msg, NETWORK_GDL90)
 }
 
+func monitorDHCPLeases() {
+	watcher, err := inotify.NewWatcher()
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = watcher.AddWatch(dhcp_lease_file, inotify.IN_CLOSE_WRITE)
+	if err != nil {
+		log.Fatal(err)
+	}
+	for {
+		select {
+		case <-watcher.Event:
+			log.Println("file modified, attempting to refresh DHCP")
+			refreshConnectedClients()
+		case err := <-watcher.Error:
+			log.Println("error with DHCP file system watcher:", err)
+		}
+	}
+}
+
 func initNetwork() {
 	messageQueue = make(chan networkMessage, 1024) // Buffered channel, 1024 messages.
 	outSockets = make(map[string]networkConnection)
 	netMutex = &sync.Mutex{}
 	refreshConnectedClients()
+	go monitorDHCPLeases()
 	go messageQueueSender()
 }