262 lines
8.1 KiB
Go
262 lines
8.1 KiB
Go
/*
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Copyright 2021 The Kubernetes Authors All rights reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package network
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import (
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"encoding/binary"
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"fmt"
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"net"
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"sync"
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"time"
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"github.com/pkg/errors"
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"k8s.io/klog/v2"
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)
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const defaultReservationPeriod = 1 * time.Minute
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var (
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reservedSubnets = sync.Map{}
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// valid private network subnets (RFC1918)
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privateSubnets = []net.IPNet{
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// 10.0.0.0/8
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{
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IP: []byte{10, 0, 0, 0},
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Mask: []byte{255, 0, 0, 0},
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},
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// 172.16.0.0/12
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{
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IP: []byte{172, 16, 0, 0},
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Mask: []byte{255, 240, 0, 0},
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},
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// 192.168.0.0/16
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{
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IP: []byte{192, 168, 0, 0},
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Mask: []byte{255, 255, 0, 0},
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},
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}
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)
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// reservation of free private subnet is held for defined reservation period from createdAt time.
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type reservation struct {
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createdAt time.Time
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}
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// Parameters contains main network parameters.
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type Parameters struct {
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IP string // IP address of the network
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Netmask string // form: 4-byte ('a.b.c.d')
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CIDR string // form: CIDR
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Gateway string // first IP address (assumed, not checked !)
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ClientMin string // second IP address
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ClientMax string // last IP address before broadcastS
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Broadcast string // last IP address
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Interface
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}
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// Interface contains main network interface parameters.
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type Interface struct {
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IfaceName string
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IfaceIPv4 string
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IfaceMTU int
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IfaceMAC string
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}
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// inspect initialises IPv4 network parameters struct from given address.
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// address can be single address (like "192.168.17.42"), network address (like "192.168.17.0"), or in cidr form (like "192.168.17.42/24 or "192.168.17.0/24").
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// If addr is valid existsing interface address, network struct will also contain info about the respective interface.
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func inspect(addr string) (*Parameters, error) {
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n := &Parameters{}
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// extract ip from addr
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ip, network, err := net.ParseCIDR(addr)
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if err != nil {
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ip = net.ParseIP(addr)
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if ip == nil {
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return nil, errors.Wrapf(err, "parsing address %q", addr)
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}
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}
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// check local interfaces
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ifaces, _ := net.Interfaces()
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for _, iface := range ifaces {
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ifAddrs, err := iface.Addrs()
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if err != nil {
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return nil, errors.Wrapf(err, "listing addresses of network interface %+v", iface)
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}
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for _, ifAddr := range ifAddrs {
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ifip, lan, err := net.ParseCIDR(ifAddr.String())
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if err != nil {
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return nil, errors.Wrapf(err, "parsing address of network iface %+v", ifAddr)
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}
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if lan.Contains(ip) {
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n.IfaceName = iface.Name
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n.IfaceIPv4 = ifip.To4().String()
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n.IfaceMTU = iface.MTU
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n.IfaceMAC = iface.HardwareAddr.String()
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n.Gateway = n.IfaceIPv4
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network = lan
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break
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}
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}
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}
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if network == nil {
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ipnet := &net.IPNet{
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IP: ip,
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Mask: ip.DefaultMask(), // assume default network mask
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}
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_, network, err = net.ParseCIDR(ipnet.String())
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if err != nil {
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return nil, errors.Wrapf(err, "determining network address from %q", addr)
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}
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}
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n.IP = network.IP.String()
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n.Netmask = net.IP(network.Mask).String() // form: 4-byte ('a.b.c.d')
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n.CIDR = network.String()
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networkIP := binary.BigEndian.Uint32(network.IP) // IP address of the network
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networkMask := binary.BigEndian.Uint32(network.Mask) // network mask
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broadcastIP := (networkIP & networkMask) | (networkMask ^ 0xffffffff) // last network IP address
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broadcast := make(net.IP, 4)
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binary.BigEndian.PutUint32(broadcast, broadcastIP)
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n.Broadcast = broadcast.String()
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gateway := net.ParseIP(n.Gateway).To4() // has to be converted to 4-byte representation!
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if gateway == nil {
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gateway = make(net.IP, 4)
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binary.BigEndian.PutUint32(gateway, networkIP+1) // assume first network IP address
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n.Gateway = gateway.String()
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}
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gatewayIP := binary.BigEndian.Uint32(gateway)
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min := make(net.IP, 4)
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binary.BigEndian.PutUint32(min, gatewayIP+1) // clients-from: first network IP address after gateway
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n.ClientMin = min.String()
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max := make(net.IP, 4)
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binary.BigEndian.PutUint32(max, broadcastIP-1) // clients-from: last network IP address before broadcast
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n.ClientMax = max.String()
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return n, nil
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}
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// isSubnetTaken returns if local network subnet exists and any error occurred.
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// If will return false in case of an error.
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func isSubnetTaken(subnet string) (bool, error) {
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ips, err := net.InterfaceAddrs()
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if err != nil {
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return false, errors.Wrap(err, "listing local networks")
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}
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for _, ip := range ips {
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_, lan, err := net.ParseCIDR(ip.String())
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if err != nil {
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return false, errors.Wrapf(err, "parsing network iface address %q", ip)
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}
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if lan.Contains(net.ParseIP(subnet)) {
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return true, nil
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}
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}
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return false, nil
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}
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// isSubnetPrivate returns if subnet is a private network.
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func isSubnetPrivate(subnet string) bool {
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for _, ipnet := range privateSubnets {
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if ipnet.Contains(net.ParseIP(subnet)) {
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return true
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}
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}
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return false
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}
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// FreeSubnet will try to find free private network beginning with startSubnet, incrementing it in steps up to number of tries.
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func FreeSubnet(startSubnet string, step, tries int) (*Parameters, error) {
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for try := 0; try < tries; try++ {
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n, err := inspect(startSubnet)
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if err != nil {
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return nil, err
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}
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startSubnet = n.IP
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if isSubnetPrivate(startSubnet) {
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taken, err := isSubnetTaken(startSubnet)
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if err != nil {
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return nil, err
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}
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if !taken {
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if ok := reserveSubnet(startSubnet, defaultReservationPeriod); ok {
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klog.Infof("using free private subnet %s: %+v", n.CIDR, n)
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return n, nil
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}
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klog.Infof("skipping subnet %s that is reserved: %+v", n.CIDR, n)
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} else {
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klog.Infof("skipping subnet %s that is taken: %+v", n.CIDR, n)
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}
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} else {
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klog.Infof("skipping subnet %s that is not private", n.CIDR)
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}
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ones, _ := net.ParseIP(n.IP).DefaultMask().Size()
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nextSubnet := net.ParseIP(startSubnet).To4()
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if ones <= 16 {
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nextSubnet[1] += byte(step)
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} else {
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nextSubnet[2] += byte(step)
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}
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startSubnet = nextSubnet.String()
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}
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return nil, fmt.Errorf("no free private network subnets found with given parameters (start: %q, step: %d, tries: %d)", startSubnet, step, tries)
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}
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// reserveSubnet returns if subnet was successfully reserved for given period:
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// - false, if it already has unexpired reservation
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// - true, if new reservation was created or expired one renewed
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// uses sync.Map to manage reservations thread-safe
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func reserveSubnet(subnet string, period time.Duration) bool {
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// put 'zero' reservation{} Map value for subnet Map key
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// to block other processes from concurently changing this subnet
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zero := reservation{}
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r, loaded := reservedSubnets.LoadOrStore(subnet, zero)
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// check if there was previously issued reservation
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if loaded {
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// back off if previous reservation was already set to 'zero'
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// as then other process is already managing this subnet concurently
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if r == zero {
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klog.Infof("backing off reserving subnet %s (other process is managing it!): %+v", subnet, &reservedSubnets)
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return false
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}
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// check if previous reservation expired
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createdAt := r.(reservation).createdAt
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if time.Since(createdAt) < period {
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// unexpired reservation: restore original createdAt value
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reservedSubnets.Store(subnet, reservation{createdAt: createdAt})
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klog.Infof("skipping subnet %s that has unexpired reservation: %+v", subnet, &reservedSubnets)
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return false
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}
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// expired reservation: renew setting createdAt to now
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reservedSubnets.Store(subnet, reservation{createdAt: time.Now()})
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klog.Infof("reusing subnet %s that has expired reservation: %+v", subnet, &reservedSubnets)
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return true
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}
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// new reservation
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klog.Infof("reserving subnet %s for %v: %+v", subnet, period, &reservedSubnets)
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reservedSubnets.Store(subnet, reservation{createdAt: time.Now()})
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return true
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}
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