From a956e5811fa218044c1e292782283688de305b65 Mon Sep 17 00:00:00 2001
From: nadoo <287492+nadoo@users.noreply.github.com>
Date: Tue, 29 Sep 2020 18:59:57 +0800
Subject: [PATCH] dhcpd: support ip pool larger than a class C

---
 service/dhcpd/dhcpd.go |  1 +
 service/dhcpd/pool.go  | 23 +++++++++++++++--------
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/service/dhcpd/dhcpd.go b/service/dhcpd/dhcpd.go
index 167010c..028c131 100644
--- a/service/dhcpd/dhcpd.go
+++ b/service/dhcpd/dhcpd.go
@@ -21,6 +21,7 @@ func init() {
 
 type dpcpd struct{}
 
+// Run runs the service.
 func (*dpcpd) Run(args ...string) {
 	if len(args) < 3 {
 		log.F("[dhcpd] not enough parameters, exiting")
diff --git a/service/dhcpd/pool.go b/service/dhcpd/pool.go
index b8ef7ac..4b9165d 100644
--- a/service/dhcpd/pool.go
+++ b/service/dhcpd/pool.go
@@ -12,14 +12,12 @@ type Pool struct {
 	items []*item
 }
 
-func NewPool(lease time.Duration, ipStart, ipEnd net.IP) (*Pool, error) {
-	items := make([]*item, 0)
-	curip := ipStart.To4()
-	for bytes.Compare(curip, ipEnd.To4()) <= 0 {
-		ip := make([]byte, 4)
-		copy(ip, curip)
-		items = append(items, &item{lease: lease, ip: ip})
-		curip[3]++
+// NewPool returns a new dhcp ip pool.
+func NewPool(lease time.Duration, start, end net.IP) (*Pool, error) {
+	s, e := ip2num(start.To4()), ip2num(end.To4())
+	items := make([]*item, 0, e-s+1)
+	for n := s; n <= e; n++ {
+		items = append(items, &item{lease: lease, ip: num2ip(n)})
 	}
 	rand.Seed(time.Now().Unix())
 	return &Pool{items: items}, nil
@@ -69,3 +67,12 @@ func (i *item) take(addr net.HardwareAddr) net.IP {
 	}
 	return nil
 }
+
+func ip2num(ip net.IP) uint32 {
+	n := uint32(ip[0])<<24 + uint32(ip[1])<<16
+	return n + uint32(ip[2])<<8 + uint32(ip[3])
+}
+
+func num2ip(n uint32) net.IP {
+	return []byte{byte(n >> 24), byte(n >> 16), byte(n >> 8), byte(n)}
+}