AdGuardHome/internal/dhcpd/v4.go

687 lines
15 KiB
Go

// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
package dhcpd
import (
"bytes"
"encoding/binary"
"fmt"
"net"
"sync"
"time"
"github.com/AdguardTeam/golibs/log"
"github.com/go-ping/ping"
"github.com/insomniacslk/dhcp/dhcpv4"
"github.com/insomniacslk/dhcp/dhcpv4/server4"
)
// v4Server is a DHCPv4 server.
//
// TODO(a.garipov): Think about unifying this and v6Server.
type v4Server struct {
srv *server4.Server
leasesLock sync.Mutex
leases []*Lease
ipAddrs [256]byte
conf V4ServerConf
}
// WriteDiskConfig4 - write configuration
func (s *v4Server) WriteDiskConfig4(c *V4ServerConf) {
*c = s.conf
}
// WriteDiskConfig6 - write configuration
func (s *v4Server) WriteDiskConfig6(c *V6ServerConf) {
}
// Return TRUE if IP address is within range [start..stop]
func ip4InRange(start, stop, ip net.IP) bool {
if len(start) != 4 || len(stop) != 4 {
return false
}
from := binary.BigEndian.Uint32(start)
to := binary.BigEndian.Uint32(stop)
check := binary.BigEndian.Uint32(ip)
return from <= check && check <= to
}
// ResetLeases - reset leases
func (s *v4Server) ResetLeases(leases []*Lease) {
s.leases = nil
for _, l := range leases {
if l.Expiry.Unix() != leaseExpireStatic &&
!ip4InRange(s.conf.ipStart, s.conf.ipEnd, l.IP) {
log.Debug("dhcpv4: skipping a lease with IP %v: not within current IP range", l.IP)
continue
}
s.addLease(l)
}
}
// GetLeasesRef - get leases
func (s *v4Server) GetLeasesRef() []*Lease {
return s.leases
}
// Return TRUE if this lease holds a blacklisted IP
func (s *v4Server) blacklisted(l *Lease) bool {
return l.HWAddr.String() == "00:00:00:00:00:00"
}
// GetLeases returns the list of current DHCP leases (thread-safe)
func (s *v4Server) GetLeases(flags int) []Lease {
var result []Lease
now := time.Now().Unix()
s.leasesLock.Lock()
for _, lease := range s.leases {
if ((flags&LeasesDynamic) != 0 && lease.Expiry.Unix() > now && !s.blacklisted(lease)) ||
((flags&LeasesStatic) != 0 && lease.Expiry.Unix() == leaseExpireStatic) {
result = append(result, *lease)
}
}
s.leasesLock.Unlock()
return result
}
// FindMACbyIP - find a MAC address by IP address in the currently active DHCP leases
func (s *v4Server) FindMACbyIP(ip net.IP) net.HardwareAddr {
now := time.Now().Unix()
s.leasesLock.Lock()
defer s.leasesLock.Unlock()
ip4 := ip.To4()
if ip4 == nil {
return nil
}
for _, l := range s.leases {
if l.IP.Equal(ip4) {
unix := l.Expiry.Unix()
if unix > now || unix == leaseExpireStatic {
return l.HWAddr
}
}
}
return nil
}
// Add the specified IP to the black list for a time period
func (s *v4Server) blacklistLease(lease *Lease) {
hw := make(net.HardwareAddr, 6)
lease.HWAddr = hw
lease.Hostname = ""
lease.Expiry = time.Now().Add(s.conf.leaseTime)
}
// Remove (swap) lease by index
func (s *v4Server) leaseRemoveSwapByIndex(i int) {
s.ipAddrs[s.leases[i].IP[3]] = 0
log.Debug("dhcpv4: removed lease %s", s.leases[i].HWAddr)
n := len(s.leases)
if i != n-1 {
s.leases[i] = s.leases[n-1] // swap with the last element
}
s.leases = s.leases[:n-1]
}
// Remove a dynamic lease with the same properties
// Return error if a static lease is found
func (s *v4Server) rmDynamicLease(lease Lease) error {
for i := 0; i < len(s.leases); i++ {
l := s.leases[i]
if bytes.Equal(l.HWAddr, lease.HWAddr) {
if l.Expiry.Unix() == leaseExpireStatic {
return fmt.Errorf("static lease already exists")
}
s.leaseRemoveSwapByIndex(i)
if i == len(s.leases) {
break
}
l = s.leases[i]
}
if net.IP.Equal(l.IP, lease.IP) {
if l.Expiry.Unix() == leaseExpireStatic {
return fmt.Errorf("static lease already exists")
}
s.leaseRemoveSwapByIndex(i)
}
}
return nil
}
// Add a lease
func (s *v4Server) addLease(l *Lease) {
s.leases = append(s.leases, l)
s.ipAddrs[l.IP[3]] = 1
log.Debug("dhcpv4: added lease %s <-> %s", l.IP, l.HWAddr)
}
// Remove a lease with the same properties
func (s *v4Server) rmLease(lease Lease) error {
for i, l := range s.leases {
if net.IP.Equal(l.IP, lease.IP) {
if !bytes.Equal(l.HWAddr, lease.HWAddr) ||
l.Hostname != lease.Hostname {
return fmt.Errorf("lease not found")
}
s.leaseRemoveSwapByIndex(i)
return nil
}
}
return fmt.Errorf("lease not found")
}
// AddStaticLease adds a static lease (thread-safe)
func (s *v4Server) AddStaticLease(lease Lease) error {
if len(lease.IP) != 4 {
return fmt.Errorf("invalid IP")
}
if len(lease.HWAddr) != 6 {
return fmt.Errorf("invalid MAC")
}
lease.Expiry = time.Unix(leaseExpireStatic, 0)
s.leasesLock.Lock()
err := s.rmDynamicLease(lease)
if err != nil {
s.leasesLock.Unlock()
return err
}
s.addLease(&lease)
s.conf.notify(LeaseChangedDBStore)
s.leasesLock.Unlock()
s.conf.notify(LeaseChangedAddedStatic)
return nil
}
// RemoveStaticLease removes a static lease (thread-safe)
func (s *v4Server) RemoveStaticLease(l Lease) error {
if len(l.IP) != 4 {
return fmt.Errorf("invalid IP")
}
if len(l.HWAddr) != 6 {
return fmt.Errorf("invalid MAC")
}
s.leasesLock.Lock()
err := s.rmLease(l)
if err != nil {
s.leasesLock.Unlock()
return err
}
s.conf.notify(LeaseChangedDBStore)
s.leasesLock.Unlock()
s.conf.notify(LeaseChangedRemovedStatic)
return nil
}
// Send ICMP to the specified machine
// Return TRUE if it doesn't reply, which probably means that the IP is available
func (s *v4Server) addrAvailable(target net.IP) bool {
if s.conf.ICMPTimeout == 0 {
return true
}
pinger, err := ping.NewPinger(target.String())
if err != nil {
log.Error("ping.NewPinger(): %v", err)
return true
}
pinger.SetPrivileged(true)
pinger.Timeout = time.Duration(s.conf.ICMPTimeout) * time.Millisecond
pinger.Count = 1
reply := false
pinger.OnRecv = func(pkt *ping.Packet) {
reply = true
}
log.Debug("dhcpv4: Sending ICMP Echo to %v", target)
err = pinger.Run()
if err != nil {
log.Error("pinger.Run(): %v", err)
return true
}
if reply {
log.Info("dhcpv4: IP conflict: %v is already used by another device", target)
return false
}
log.Debug("dhcpv4: ICMP procedure is complete: %v", target)
return true
}
// Find lease by MAC
func (s *v4Server) findLease(mac net.HardwareAddr) *Lease {
for i := range s.leases {
if bytes.Equal(mac, s.leases[i].HWAddr) {
return s.leases[i]
}
}
return nil
}
// Get next free IP
func (s *v4Server) findFreeIP() net.IP {
for i := s.conf.ipStart[3]; ; i++ {
if s.ipAddrs[i] == 0 {
ip := make([]byte, 4)
copy(ip, s.conf.ipStart)
ip[3] = i
return ip
}
if i == s.conf.ipEnd[3] {
break
}
}
return nil
}
// Find an expired lease and return its index or -1
func (s *v4Server) findExpiredLease() int {
now := time.Now().Unix()
for i, lease := range s.leases {
if lease.Expiry.Unix() != leaseExpireStatic &&
lease.Expiry.Unix() <= now {
return i
}
}
return -1
}
// Reserve lease for MAC
func (s *v4Server) reserveLease(mac net.HardwareAddr) *Lease {
l := Lease{}
l.HWAddr = make([]byte, 6)
copy(l.HWAddr, mac)
l.IP = s.findFreeIP()
if l.IP == nil {
i := s.findExpiredLease()
if i < 0 {
return nil
}
copy(s.leases[i].HWAddr, mac)
return s.leases[i]
}
s.addLease(&l)
return &l
}
func (s *v4Server) commitLease(l *Lease) {
l.Expiry = time.Now().Add(s.conf.leaseTime)
s.leasesLock.Lock()
s.conf.notify(LeaseChangedDBStore)
s.leasesLock.Unlock()
s.conf.notify(LeaseChangedAdded)
}
// Process Discover request and return lease
func (s *v4Server) processDiscover(req, resp *dhcpv4.DHCPv4) *Lease {
mac := req.ClientHWAddr
s.leasesLock.Lock()
defer s.leasesLock.Unlock()
lease := s.findLease(mac)
if lease == nil {
toStore := false
for lease == nil {
lease = s.reserveLease(mac)
if lease == nil {
log.Debug("dhcpv4: No more IP addresses")
if toStore {
s.conf.notify(LeaseChangedDBStore)
}
return nil
}
toStore = true
if !s.addrAvailable(lease.IP) {
s.blacklistLease(lease)
lease = nil
continue
}
break
}
s.conf.notify(LeaseChangedDBStore)
} else {
reqIP := req.Options.Get(dhcpv4.OptionRequestedIPAddress)
if len(reqIP) != 0 &&
!bytes.Equal(reqIP, lease.IP) {
log.Debug("dhcpv4: different RequestedIP: %v != %v", reqIP, lease.IP)
}
}
resp.UpdateOption(dhcpv4.OptMessageType(dhcpv4.MessageTypeOffer))
return lease
}
type optFQDN struct {
name string
}
func (o *optFQDN) String() string {
return "optFQDN"
}
// flags[1]
// A-RR[1]
// PTR-RR[1]
// name[]
func (o *optFQDN) ToBytes() []byte {
b := make([]byte, 3+len(o.name))
i := 0
b[i] = 0x03 // f_server_overrides | f_server
i++
b[i] = 255 // A-RR
i++
b[i] = 255 // PTR-RR
i++
copy(b[i:], []byte(o.name))
return b
}
// Process Request request and return lease
// Return false if we don't need to reply
func (s *v4Server) processRequest(req, resp *dhcpv4.DHCPv4) (*Lease, bool) {
var lease *Lease
mac := req.ClientHWAddr
hostname := req.Options.Get(dhcpv4.OptionHostName)
reqIP := req.Options.Get(dhcpv4.OptionRequestedIPAddress)
if reqIP == nil {
reqIP = req.ClientIPAddr
}
sid := req.Options.Get(dhcpv4.OptionServerIdentifier)
if len(sid) != 0 &&
!bytes.Equal(sid, s.conf.dnsIPAddrs[0]) {
log.Debug("dhcpv4: Bad OptionServerIdentifier in Request message for %s", mac)
return nil, false
}
if len(reqIP) != 4 {
log.Debug("dhcpv4: Bad OptionRequestedIPAddress in Request message for %s", mac)
return nil, false
}
s.leasesLock.Lock()
for _, l := range s.leases {
if bytes.Equal(l.HWAddr, mac) {
if !bytes.Equal(l.IP, reqIP) {
s.leasesLock.Unlock()
log.Debug("dhcpv4: Mismatched OptionRequestedIPAddress in Request message for %s", mac)
return nil, true
}
lease = l
break
}
}
s.leasesLock.Unlock()
if lease == nil {
log.Debug("dhcpv4: No lease for %s", mac)
return nil, true
}
if lease.Expiry.Unix() != leaseExpireStatic {
lease.Hostname = string(hostname)
s.commitLease(lease)
} else if len(lease.Hostname) != 0 {
o := &optFQDN{
name: lease.Hostname,
}
fqdn := dhcpv4.Option{
Code: dhcpv4.OptionFQDN,
Value: o,
}
resp.UpdateOption(fqdn)
}
resp.UpdateOption(dhcpv4.OptMessageType(dhcpv4.MessageTypeAck))
return lease, true
}
// Find a lease associated with MAC and prepare response
// Return 1: OK
// Return 0: error; reply with Nak
// Return -1: error; don't reply
func (s *v4Server) process(req, resp *dhcpv4.DHCPv4) int {
var lease *Lease
resp.UpdateOption(dhcpv4.OptServerIdentifier(s.conf.dnsIPAddrs[0]))
switch req.MessageType() {
case dhcpv4.MessageTypeDiscover:
lease = s.processDiscover(req, resp)
if lease == nil {
return 0
}
case dhcpv4.MessageTypeRequest:
var toReply bool
lease, toReply = s.processRequest(req, resp)
if lease == nil {
if toReply {
return 0
}
return -1 // drop packet
}
}
resp.YourIPAddr = make([]byte, 4)
copy(resp.YourIPAddr, lease.IP)
resp.UpdateOption(dhcpv4.OptIPAddressLeaseTime(s.conf.leaseTime))
resp.UpdateOption(dhcpv4.OptRouter(s.conf.routerIP))
resp.UpdateOption(dhcpv4.OptSubnetMask(s.conf.subnetMask))
resp.UpdateOption(dhcpv4.OptDNS(s.conf.dnsIPAddrs...))
for _, opt := range s.conf.options {
resp.Options[opt.code] = opt.val
}
return 1
}
// client(0.0.0.0:68) -> (Request:ClientMAC,Type=Discover,ClientID,ReqIP,HostName) -> server(255.255.255.255:67)
// client(255.255.255.255:68) <- (Reply:YourIP,ClientMAC,Type=Offer,ServerID,SubnetMask,LeaseTime) <- server(<IP>:67)
// client(0.0.0.0:68) -> (Request:ClientMAC,Type=Request,ClientID,ReqIP||ClientIP,HostName,ServerID,ParamReqList) -> server(255.255.255.255:67)
// client(255.255.255.255:68) <- (Reply:YourIP,ClientMAC,Type=ACK,ServerID,SubnetMask,LeaseTime) <- server(<IP>:67)
func (s *v4Server) packetHandler(conn net.PacketConn, peer net.Addr, req *dhcpv4.DHCPv4) {
log.Debug("dhcpv4: received message: %s", req.Summary())
switch req.MessageType() {
case dhcpv4.MessageTypeDiscover,
dhcpv4.MessageTypeRequest:
//
default:
log.Debug("dhcpv4: unsupported message type %d", req.MessageType())
return
}
resp, err := dhcpv4.NewReplyFromRequest(req)
if err != nil {
log.Debug("dhcpv4: dhcpv4.New: %s", err)
return
}
if len(req.ClientHWAddr) != 6 {
log.Debug("dhcpv4: Invalid ClientHWAddr")
return
}
r := s.process(req, resp)
if r < 0 {
return
} else if r == 0 {
resp.Options.Update(dhcpv4.OptMessageType(dhcpv4.MessageTypeNak))
}
log.Debug("dhcpv4: sending: %s", resp.Summary())
_, err = conn.WriteTo(resp.ToBytes(), peer)
if err != nil {
log.Error("dhcpv4: conn.Write to %s failed: %s", peer, err)
return
}
}
// Start starts the IPv4 DHCP server.
func (s *v4Server) Start() error {
if !s.conf.Enabled {
return nil
}
ifaceName := s.conf.InterfaceName
iface, err := net.InterfaceByName(ifaceName)
if err != nil {
return fmt.Errorf("dhcpv4: finding interface %s by name: %w", ifaceName, err)
}
log.Debug("dhcpv4: starting...")
dnsIPAddrs, err := ifaceDNSIPAddrs(iface, ipVersion4, defaultMaxAttempts, defaultBackoff)
if err != nil {
return fmt.Errorf("dhcpv4: interface %s: %w", ifaceName, err)
}
if len(dnsIPAddrs) == 0 {
// No available IP addresses which may appear later.
return nil
}
s.conf.dnsIPAddrs = dnsIPAddrs
laddr := &net.UDPAddr{
IP: net.ParseIP("0.0.0.0"),
Port: dhcpv4.ServerPort,
}
s.srv, err = server4.NewServer(iface.Name, laddr, s.packetHandler, server4.WithDebugLogger())
if err != nil {
return err
}
log.Info("dhcpv4: listening")
go func() {
err = s.srv.Serve()
log.Debug("dhcpv4: srv.Serve: %s", err)
}()
return nil
}
// Stop - stop server
func (s *v4Server) Stop() {
if s.srv == nil {
return
}
log.Debug("dhcpv4: stopping")
err := s.srv.Close()
if err != nil {
log.Error("dhcpv4: srv.Close: %s", err)
}
// now s.srv.Serve() will return
s.srv = nil
}
// Create DHCPv4 server
func v4Create(conf V4ServerConf) (DHCPServer, error) {
s := &v4Server{}
s.conf = conf
if !conf.Enabled {
return s, nil
}
var err error
s.conf.routerIP, err = parseIPv4(s.conf.GatewayIP)
if err != nil {
return s, fmt.Errorf("dhcpv4: %w", err)
}
subnet, err := parseIPv4(s.conf.SubnetMask)
if err != nil || !isValidSubnetMask(subnet) {
return s, fmt.Errorf("dhcpv4: invalid subnet mask: %s", s.conf.SubnetMask)
}
s.conf.subnetMask = make([]byte, 4)
copy(s.conf.subnetMask, subnet)
s.conf.ipStart, err = parseIPv4(conf.RangeStart)
if s.conf.ipStart == nil {
return s, fmt.Errorf("dhcpv4: %w", err)
}
if s.conf.ipStart[0] == 0 {
return s, fmt.Errorf("dhcpv4: invalid range start IP")
}
s.conf.ipEnd, err = parseIPv4(conf.RangeEnd)
if s.conf.ipEnd == nil {
return s, fmt.Errorf("dhcpv4: %w", err)
}
if !net.IP.Equal(s.conf.ipStart[:3], s.conf.ipEnd[:3]) ||
s.conf.ipStart[3] > s.conf.ipEnd[3] {
return s, fmt.Errorf("dhcpv4: range end IP should match range start IP")
}
if conf.LeaseDuration == 0 {
s.conf.leaseTime = time.Hour * 24
s.conf.LeaseDuration = uint32(s.conf.leaseTime.Seconds())
} else {
s.conf.leaseTime = time.Second * time.Duration(conf.LeaseDuration)
}
for _, o := range conf.Options {
code, val := parseOptionString(o)
if code == 0 {
log.Debug("dhcpv4: bad option string: %s", o)
continue
}
opt := dhcpOption{
code: code,
val: val,
}
s.conf.options = append(s.conf.options, opt)
}
return s, nil
}