dnsmasq-netbox-connector/internal/dnsmasq/dnsmasq.go

package dnsmasq

import (
	"fmt"
	"net/netip"
	"os"
	"strconv"
	"strings"
	"time"
)

type Lease struct {
	ExpireDate time.Time
	Mac        string
	IP         netip.Addr
	Hostname   string
	ClientID   string
}

func (l Lease) String() string {
	return fmt.Sprintf("[expire on %v]: host %s IP %s (mac %s - clientID %s)", l.ExpireDate, l.Hostname, l.IP, l.Mac, l.ClientID)
}

func parseLeaseLine(rawLine string) (*Lease, error) {
	lineValues := strings.Split(rawLine, " ")
	if len(lineValues) != 5 {
		return nil, fmt.Errorf("unexpected number of values, expected 5, got %d", len(lineValues))
	}

	expireTimeInt, err := strconv.Atoi(lineValues[0])
	if err != nil {
		return nil, fmt.Errorf("unexpected unix timestamp value %s", lineValues[0])
	}

	ip, err := netip.ParseAddr(lineValues[2])
	if err != nil {
		return nil, fmt.Errorf("unexpected IP address: %s: %w", lineValues[2], err)
	}

	return &Lease{
		ExpireDate: time.Unix(int64(expireTimeInt), 0),
		Mac:        lineValues[1],
		IP:         ip,
		Hostname:   lineValues[3],
		ClientID:   lineValues[4],
	}, nil
}

func GetLeases(leasesPath string) ([]*Lease, error) {
	fileContent, err := os.ReadFile(leasesPath)
	if err != nil {
		return nil, fmt.Errorf("failed to read leases file: %w", err)
	}

	leases := []*Lease{}
	for i, l := range strings.Split(string(fileContent), "\n") {
		if l == "" {
			continue
		}
		lease, err := parseLeaseLine(l)
		if err != nil {
			return nil, fmt.Errorf("failed to parse line %d: %w", i, err)
		}
		leases = append(leases, lease)
	}
	return leases, nil
}

func GetDynamicLeases(leasesPath string, dhcpStart, dhcpEnd netip.Addr) ([]*Lease, error) {
	allLeases, err := GetLeases(leasesPath)
	if err != nil {
		return nil, err
	}

	filteredLeases := []*Lease{}
	for _, l := range allLeases {
		if l.IP.Less(dhcpEnd) && dhcpStart.Less(l.IP) {
			filteredLeases = append(filteredLeases, l)
		}
	}

	return filteredLeases, nil
}