Feature: support fakeip

component/fakeip/pool.go

@@ -0,0 +1,50 @@
+package fakeip
+
+import (
+	"errors"
+	"net"
+)
+
+// Pool is a implementation about fake ip generator without storage
+type Pool struct {
+	max    uint32
+	min    uint32
+	offset uint32
+}
+
+// Get return a new fake ip
+func (p *Pool) Get() net.IP {
+	ip := uintToIP(p.min + p.offset)
+	p.offset = (p.offset + 1) % (p.max - p.min)
+	return ip
+}
+
+func ipToUint(ip net.IP) uint32 {
+	v := uint32(ip[0]) << 24
+	v += uint32(ip[1]) << 16
+	v += uint32(ip[2]) << 8
+	v += uint32(ip[3])
+	return v
+}
+
+func uintToIP(v uint32) net.IP {
+	return net.IPv4(byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
+}
+
+// New return Pool instance
+func New(ipnet *net.IPNet) (*Pool, error) {
+	min := ipToUint(ipnet.IP) + 1
+
+	ones, bits := ipnet.Mask.Size()
+	total := 1<<uint(bits-ones) - 2
+
+	if total <= 0 {
+		return nil, errors.New("ipnet don't have valid ip")
+	}
+
+	max := min + uint32(total)
+	return &Pool{
+		min: min,
+		max: max,
+	}, nil
+}