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package main
import (
"errors"
"fmt"
"os"
"strings"
"github.com/edwarnicke/exechelper"
)
type AddressCounter = int
type Ip4AddressAllocator struct {
networks map[int]AddressCounter
chosenOctet int
assignedIps []string
}
func (a *Ip4AddressAllocator) AddNetwork(networkNumber int) {
a.networks[networkNumber] = 1
}
func (a *Ip4AddressAllocator) NewIp4InterfaceAddress(inputNetworkNumber ...int) (string, error) {
var networkNumber int = 0
if len(inputNetworkNumber) > 0 {
networkNumber = inputNetworkNumber[0]
}
if _, ok := a.networks[networkNumber]; !ok {
a.AddNetwork(networkNumber)
}
numberOfAddresses := a.networks[networkNumber]
if numberOfAddresses == 254 {
return "", fmt.Errorf("no available IPv4 addresses")
}
address, err := a.createIpAddress(networkNumber, numberOfAddresses)
a.networks[networkNumber] = numberOfAddresses + 1
return address + "/24", err
}
// Creates a file every time an IP is assigned: used to keep track of addresses in use.
// If an address is not in use, 'counter' is then copied to 'chosenOctet' and it is used for the remaining tests.
// Also checks host IP addresses.
func (a *Ip4AddressAllocator) createIpAddress(networkNumber int, numberOfAddresses int) (string, error){
hostIps, _ := exechelper.CombinedOutput("ip a")
counter := 10
var address string
for {
if a.chosenOctet != 0 {
address = fmt.Sprintf("10.%v.%v.%v", a.chosenOctet, networkNumber, numberOfAddresses)
file, err := os.Create(address)
if err != nil{
return "", errors.New("unable to create file: " + fmt.Sprint(err))
}
file.Close()
break
} else {
address = fmt.Sprintf("10.%v.%v.%v", counter, networkNumber, numberOfAddresses)
_, err := os.Stat(address)
if err == nil || strings.Contains(string(hostIps), address) {
counter++
} else if os.IsNotExist(err) {
file, err := os.Create(address)
if err != nil{
return "", errors.New("unable to create file: " + fmt.Sprint(err))
}
file.Close()
a.chosenOctet = counter
break
} else {
return "", errors.New("an error occured while checking if a file exists: " + fmt.Sprint(err))
}
}
}
a.assignedIps = append(a.assignedIps, address)
return address, nil
}
func (a *Ip4AddressAllocator) deleteIpAddresses(){
for ip := range a.assignedIps{
os.Remove(a.assignedIps[ip])
}
}
func NewIp4AddressAllocator() *Ip4AddressAllocator {
var ip4AddrAllocator = new(Ip4AddressAllocator)
ip4AddrAllocator.networks = make(map[int]AddressCounter)
ip4AddrAllocator.AddNetwork(0)
return ip4AddrAllocator
}
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