Fix: fake ip pool offset calculate (#2281)

component/fakeip/pool.go

@@ -21,7 +21,7 @@ type store interface {
 	CloneTo(store)
 }
 
-// Pool is a implementation about fake ip generator without storage
+// Pool is an implementation about fake ip generator without storage
 type Pool struct {
 	max     uint32
 	min     uint32
@@ -99,21 +99,21 @@ func (p *Pool) CloneFrom(o *Pool) {
 func (p *Pool) get(host string) net.IP {
 	current := p.offset
 	for {
+		ip := uintToIP(p.min + p.offset)
+		if !p.store.Exist(ip) {
+			break
+		}
+
 		p.offset = (p.offset + 1) % (p.max - p.min)
 		// Avoid infinite loops
 		if p.offset == current {
 			p.offset = (p.offset + 1) % (p.max - p.min)
-			ip := uintToIP(p.min + p.offset - 1)
+			ip := uintToIP(p.min + p.offset)
 			p.store.DelByIP(ip)
 			break
 		}
-
-		ip := uintToIP(p.min + p.offset - 1)
-		if !p.store.Exist(ip) {
-			break
-		}
 	}
-	ip := uintToIP(p.min + p.offset - 1)
+	ip := uintToIP(p.min + p.offset)
 	p.store.PutByIP(ip, host)
 	return ip
 }

component/fakeip/pool_test.go

@@ -1,7 +1,6 @@
 package fakeip
 
 import (
-	"fmt"
 	"net"
 	"os"
 	"testing"
@@ -106,15 +105,13 @@ func TestPool_CycleUsed(t *testing.T) {
 	defer os.Remove(tempfile)
 
 	for _, pool := range pools {
-		foo := pool.Lookup("foo.com")
-		bar := pool.Lookup("bar.com")
-		for i := 0; i < 3; i++ {
-			pool.Lookup(fmt.Sprintf("%d.com", i))
-		}
-		baz := pool.Lookup("baz.com")
-		next := pool.Lookup("foo.com")
-		assert.True(t, foo.Equal(baz))
-		assert.True(t, next.Equal(bar))
+		assert.Equal(t, net.IP{192, 168, 0, 2}, pool.Lookup("2.com"))
+		assert.Equal(t, net.IP{192, 168, 0, 3}, pool.Lookup("3.com"))
+		assert.Equal(t, net.IP{192, 168, 0, 4}, pool.Lookup("4.com"))
+		assert.Equal(t, net.IP{192, 168, 0, 5}, pool.Lookup("5.com"))
+		assert.Equal(t, net.IP{192, 168, 0, 6}, pool.Lookup("6.com"))
+		assert.Equal(t, net.IP{192, 168, 0, 2}, pool.Lookup("12.com"))
+		assert.Equal(t, net.IP{192, 168, 0, 3}, pool.Lookup("3.com"))
 	}
 }