cidr allocator

pkg/controller/node/cidr_allocator.go

@@ -0,0 +1,123 @@
+/*
+Copyright 2016 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package node
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"math/big"
+	"net"
+	"sync"
+)
+
+var errCIDRRangeNoCIDRsRemaining = errors.New("CIDR allocation failed; there are no remaining CIDRs left to allocate in the accepted range")
+
+// CIDRAllocator is an interface implemented by things that know how to allocate/occupy/recycle CIDR for nodes.
+type CIDRAllocator interface {
+	AllocateNext() (*net.IPNet, error)
+	Occupy(*net.IPNet) error
+	Release(*net.IPNet) error
+}
+
+type rangeAllocator struct {
+	clusterIP       net.IP
+	clusterMaskSize int
+	subNetMaskSize  int
+	maxCIDRs        int
+	used            big.Int
+	lock            sync.Mutex
+}
+
+// NewCIDRRangeAllocator returns a CIDRAllocator to allocate CIDR for node
+// Caller must ensure subNetMaskSize is not less than cluster CIDR mask size.
+func NewCIDRRangeAllocator(clusterCIDR *net.IPNet, subNetMaskSize int) CIDRAllocator {
+	clusterMask := clusterCIDR.Mask
+	clusterMaskSize, _ := clusterMask.Size()
+
+	ra := &rangeAllocator{
+		clusterIP:       clusterCIDR.IP.To4(),
+		clusterMaskSize: clusterMaskSize,
+		subNetMaskSize:  subNetMaskSize,
+		maxCIDRs:        1 << uint32(subNetMaskSize-clusterMaskSize),
+	}
+	return ra
+}
+
+func (r *rangeAllocator) AllocateNext() (*net.IPNet, error) {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+
+	nextUnused := -1
+	for i := 0; i < r.maxCIDRs; i++ {
+		if r.used.Bit(i) == 0 {
+			nextUnused = i
+			break
+		}
+	}
+	if nextUnused == -1 {
+		return nil, errCIDRRangeNoCIDRsRemaining
+	}
+
+	r.used.SetBit(&r.used, nextUnused, 1)
+
+	j := uint32(nextUnused) << uint32(32-r.subNetMaskSize)
+	ipInt := (binary.BigEndian.Uint32(r.clusterIP)) | j
+	ip := make([]byte, 4)
+	binary.BigEndian.PutUint32(ip, ipInt)
+
+	return &net.IPNet{
+		IP:   ip,
+		Mask: net.CIDRMask(r.subNetMaskSize, 32),
+	}, nil
+}
+
+func (r *rangeAllocator) Release(cidr *net.IPNet) error {
+	used, err := r.getBitforCIDR(cidr)
+	if err != nil {
+		return err
+	}
+
+	r.lock.Lock()
+	defer r.lock.Unlock()
+	r.used.SetBit(&r.used, used, 0)
+
+	return nil
+}
+
+func (r *rangeAllocator) Occupy(cidr *net.IPNet) error {
+	used, err := r.getBitforCIDR(cidr)
+	if err != nil {
+		return err
+	}
+
+	r.lock.Lock()
+	defer r.lock.Unlock()
+	r.used.SetBit(&r.used, used, 1)
+
+	return nil
+}
+
+func (r *rangeAllocator) getBitforCIDR(cidr *net.IPNet) (int, error) {
+	used := (binary.BigEndian.Uint32(r.clusterIP) ^ binary.BigEndian.Uint32(cidr.IP.To4())) >> uint32(32-r.subNetMaskSize)
+
+	if used > uint32(r.maxCIDRs) {
+		return 0, fmt.Errorf("CIDR: %v is out of the range of CIDR allocator", cidr)
+	}
+
+	return int(used), nil
+}