// Copyright (c) 2017-2021 Tigera, Inc. 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 proxy

import (
	"context"
	"fmt"
	"net"
	"reflect"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/pkg/errors"
	log "github.com/sirupsen/logrus"
	v1 "k8s.io/api/core/v1"
	k8sp "k8s.io/kubernetes/pkg/proxy"

	"github.com/projectcalico/calico/felix/cachingmap"

	"github.com/projectcalico/calico/felix/bpf"
	"github.com/projectcalico/calico/felix/bpf/nat"
	"github.com/projectcalico/calico/felix/bpf/routes"
	"github.com/projectcalico/calico/felix/ip"
)

var podNPIP = net.IPv4(255, 255, 255, 255)

type svcInfo struct {
	id         uint32
	count      int
	localCount int
	svc        k8sp.ServicePort
}

type svcKey struct {
	sname k8sp.ServicePortName
	extra string
}

func (k svcKey) String() string {
	if k.extra == "" {
		return k.sname.String()
	}

	return fmt.Sprintf("%s:%s", k.extra, k.sname)
}

func getSvcKey(sname k8sp.ServicePortName, extra string) svcKey {
	return svcKey{
		sname: sname,
		extra: extra,
	}
}

type svcType int

const (
	svcTypeExternalIP svcType = iota
	svcTypeNodePort
	svcTypeNodePortRemote
	svcTypeLoadBalancer
)

var svcType2String = map[svcType]string{
	svcTypeNodePort:       "NodePort",
	svcTypeExternalIP:     "ExternalIP",
	svcTypeNodePortRemote: "NodePortRemote",
	svcTypeLoadBalancer:   "LoadBalancer",
}

func getSvcKeyExtra(t svcType, ip string) string {
	return svcType2String[t] + ":" + ip
}

func hasSvcKeyExtra(skey svcKey, t svcType) bool {
	return strings.HasPrefix(skey.extra, svcType2String[t]+":")
}

func isSvcKeyDerived(skey svcKey) bool {
	return hasSvcKeyExtra(skey, svcTypeExternalIP) ||
		hasSvcKeyExtra(skey, svcTypeNodePort) ||
		hasSvcKeyExtra(skey, svcTypeLoadBalancer)
}

type stickyFrontend struct {
	id    uint32
	timeo time.Duration
}

// Syncer is an implementation of DPSyncer interface. It is not thread safe and
// should be called only once at a time
type Syncer struct {
	bpfSvcs *cachingmap.CachingMap[nat.FrontendKey, nat.FrontendValue]
	bpfEps  *cachingmap.CachingMap[nat.BackendKey, nat.BackendValue]
	bpfAff  bpf.Map

	nextSvcID uint32

	nodePortIPs []net.IP
	rt          Routes

	// new maps are valid during the Apply()'s runtime to provide easy access
	// to updating them. They become prev at the end of it to be compared
	// against in the next iteration
	newSvcMap  map[svcKey]svcInfo
	newEpsMap  k8sp.EndpointsMap
	prevSvcMap map[svcKey]svcInfo
	prevEpsMap k8sp.EndpointsMap
	// active Maps contain all active svcs endpoints at the end of an iteration
	activeSvcsMap map[ipPortProto]uint32
	activeEpsMap  map[uint32]map[ipPort]struct{}

	// Protects accessing the [prev|new][Svc|Eps]Map,
	mapsLck sync.Mutex

	// synced is true after reconciling the first Apply
	synced bool

	expFixupWg   sync.WaitGroup
	expFixupStop chan struct{}

	stop     chan struct{}
	stopOnce sync.Once

	stickySvcs map[nat.FrontEndAffinityKey]stickyFrontend
	stickyEps  map[uint32]map[nat.BackendValue]struct{}

	// triggerFn is called when one of the syncer's background threads needs to trigger an Apply().
	// The proxy sets this to the runner's Run() method.  We assume that the method doesn't block.
	triggerFn func()
}

type ipPort struct {
	ip   string
	port int
}

type ipPortProto struct {
	ipPort
	proto uint8
}

// servicePortToIPPortProto is a simple way how to turn a k8sp.ServicePort into
// an ipPortProto
func servicePortToIPPortProto(sp k8sp.ServicePort) ipPortProto {
	return ipPortProto{
		ipPort: ipPort{
			ip:   sp.ClusterIP().String(),
			port: sp.Port(),
		},
		proto: ProtoV1ToIntPanic(sp.Protocol()),
	}
}

func uniqueIPs(ips []net.IP) []net.IP {
	m := make(map[string]net.IP)
	unique := true

	for _, ip := range ips {
		s := ip.String()
		if _, ok := m[s]; ok {
			unique = false
		} else {
			m[s] = ip
		}
	}

	if unique {
		return ips
	}

	ret := make([]net.IP, 0, len(m))
	for _, ip := range m {
		ret = append(ret, ip)
	}

	return ret
}

// NewSyncer returns a new Syncer
func NewSyncer(nodePortIPs []net.IP,
	svcsmap *cachingmap.CachingMap[nat.FrontendKey, nat.FrontendValue],
	epsmap *cachingmap.CachingMap[nat.BackendKey, nat.BackendValue],
	affmap bpf.Map, rt Routes) (*Syncer, error) {

	s := &Syncer{
		bpfSvcs:     svcsmap,
		bpfEps:      epsmap,
		bpfAff:      affmap,
		rt:          rt,
		nodePortIPs: uniqueIPs(nodePortIPs),
		prevSvcMap:  make(map[svcKey]svcInfo),
		prevEpsMap:  make(k8sp.EndpointsMap),
		stop:        make(chan struct{}),
	}

	if err := s.loadOrigs(); err != nil {
		return nil, err
	}

	return s, nil
}

func (s *Syncer) loadOrigs() error {
	err := s.bpfEps.LoadCacheFromDataplane()
	if err != nil {
		return err
	}
	err = s.bpfSvcs.LoadCacheFromDataplane()
	if err != nil {
		return err
	}
	return nil
}

type syncRef struct {
	svc  k8sp.ServicePortName
	info k8sp.ServicePort
}

// svcMapToIPPortProtoMap takes the kubernetes service representation and makes an index
// so we can cross reference with the values we learn from the dataplane.
func (s *Syncer) svcMapToIPPortProtoMap(svcs k8sp.ServiceMap) map[nat.FrontendKey]syncRef {
	ref := make(map[nat.FrontendKey]syncRef, len(svcs))

	for key, svc := range svcs {
		clusterIP := svc.ClusterIP()
		proto := uint8(ProtoV1ToIntPanic(svc.Protocol()))
		port := uint16(svc.Port())

		xref := syncRef{key, svc}

		ref[nat.NewNATKey(clusterIP, port, proto)] = xref

		np := uint16(0)

		if svc.NodePort() != 0 {
			np = uint16(svc.NodePort())

			ref[nat.NewNATKey(clusterIP, np, proto)] = xref

			for _, npIP := range s.nodePortIPs {
				ref[nat.NewNATKey(npIP, np, proto)] = xref
			}
		}

		for _, extIP := range svc.ExternalIPStrings() {
			ref[nat.NewNATKey(net.ParseIP(extIP), port, proto)] = xref
		}
	}

	return ref
}

func (s *Syncer) startupBuildPrev(state DPSyncerState) error {
	// Build a map keyed by nat.FrontendKey of services to be generated from the
	// state. The map values contains references to both ServicePortName keys of
	// the state map as well as the ServicePort values.
	svcRef := s.svcMapToIPPortProtoMap(state.SvcMap)

	inconsistent := false

	// Walk the frontend bpf map that was read into memory and match it against the
	// references build from the state
	s.bpfSvcs.IterDataplaneCache(func(svck nat.FrontendKey, svcv nat.FrontendValue) {
		xref, ok := svcRef[svck]
		if !ok {
			return
		}

		// If there is a cross-reference with the current state, try to match
		// what is in the bpf map with what was supposed to be a service that
		// created it - based on the current state.
		svckey := s.matchBpfSvc(svck, xref.svc, xref.info)
		if svckey == nil {
			return
		}

		id := svcv.ID()
		count := int(svcv.Count())
		s.prevSvcMap[*svckey] = svcInfo{
			id:         id,
			count:      count,
			localCount: int(svcv.LocalCount()),
			svc:        state.SvcMap[svckey.sname],
		}

		if id >= s.nextSvcID {
			s.nextSvcID = id + 1
		}

		if svckey.extra != "" {
			return
		}

		if count > 0 {
			s.prevEpsMap[svckey.sname] = make([]k8sp.Endpoint, 0, count)
		}
		for i := 0; i < count; i++ {
			epk := nat.NewNATBackendKey(id, uint32(i))
			ep, ok := s.bpfEps.GetDataplaneCache(epk)
			if !ok {
				log.Warnf("inconsistent backed map, missing ep %s", epk)
				inconsistent = true
				break
			}
			s.prevEpsMap[svckey.sname] = append(s.prevEpsMap[svckey.sname],
				&k8sp.BaseEndpointInfo{
					Endpoint: net.JoinHostPort(ep.Addr().String(), strconv.Itoa(int(ep.Port()))),
					// IsLocal is not important here
				},
			)
		}
	})

	if inconsistent {
		return fmt.Errorf("found inconsistencies in existing BPF maps, will rewrite maps from scratch")
	}

	return nil
}

func (s *Syncer) startupSync(state DPSyncerState) error {
	// Try to build the previous maps based on the current state and what is in bpf maps.
	// Once we have the previous map, we can apply the the current state as if we never
	// restarted and apply only the diff using the regular code path.
	if err := s.startupBuildPrev(state); err != nil {
		log.WithError(err).Error("Failed to load previous state of NAT maps from dataplane, " +
			"maps will get disruptively rewritten")
	}
	return nil
}

func (s *Syncer) applySvc(skey svcKey, sinfo k8sp.ServicePort, eps []k8sp.Endpoint) error {
	var id uint32

	old, exists := s.prevSvcMap[skey]
	if exists && ServicePortEqual(old.svc, sinfo) {
		id = old.id
	} else {
		id = s.newSvcID()
	}
	count, local, err := s.updateService(skey, sinfo, id, eps)
	if err != nil {
		return err
	}

	s.newSvcMap[skey] = svcInfo{
		id:         id,
		count:      count,
		localCount: local,
		svc:        sinfo,
	}

	if log.GetLevel() >= log.DebugLevel {
		log.Debugf("applied a service %s update: sinfo=%+v", skey, s.newSvcMap[skey])
	}

	return nil
}

func (s *Syncer) addActiveEps(id uint32, svc k8sp.ServicePort, eps []k8sp.Endpoint) {
	svcKey := servicePortToIPPortProto(svc)

	s.activeSvcsMap[svcKey] = id

	if len(eps) == 0 {
		return
	}

	epsmap := make(map[ipPort]struct{})
	s.activeEpsMap[id] = epsmap
	for _, ep := range eps {
		port, _ := ep.Port() // it is error free by this point
		epsmap[ipPort{
			ip:   ep.IP(),
			port: port,
		}] = struct{}{}
	}
}

func (s *Syncer) applyExpandedNP(sname k8sp.ServicePortName, sinfo k8sp.ServicePort,
	eps []k8sp.Endpoint, node ip.V4Addr, nport int) error {
	skey := getSvcKey(sname, getSvcKeyExtra(svcTypeNodePortRemote, node.String()))
	si := serviceInfoFromK8sServicePort(sinfo)
	si.clusterIP = node.AsNetIP()
	si.port = nport

	if err := s.applySvc(skey, si, eps); err != nil {
		return errors.Errorf("apply NodePortRemote for %s node %s", sname, node)
	}

	return nil
}

type expandMiss struct {
	sname k8sp.ServicePortName
	sinfo k8sp.ServicePort
	eps   []k8sp.Endpoint
	nport int
}

func (s *Syncer) expandAndApplyNodePorts(sname k8sp.ServicePortName, sinfo k8sp.ServicePort,
	eps []k8sp.Endpoint, nport int, rtLookup func(addr ip.Addr) (routes.Value, bool)) *expandMiss {

	ipToEp, miss := s.expandNodePorts(sname, sinfo, eps, nport, rtLookup)

	for node, neps := range ipToEp {
		if err := s.applyExpandedNP(sname, sinfo, neps, node, nport); err != nil {
			log.WithField("error", err).Errorf("Failed to expand NodePort")
		}
	}

	return miss
}

func (s *Syncer) expandNodePorts(
	sname k8sp.ServicePortName,
	sinfo k8sp.ServicePort,
	eps []k8sp.Endpoint,
	nport int,
	rtLookup func(addr ip.Addr) (routes.Value, bool),
) (map[ip.V4Addr][]k8sp.Endpoint, *expandMiss) {
	ipToEp := make(map[ip.V4Addr][]k8sp.Endpoint)
	var miss *expandMiss
	for _, ep := range eps {
		ipv4 := ip.FromString(ep.IP()).(ip.V4Addr)

		rt, ok := rtLookup(ipv4)
		if !ok {
			log.Errorf("No route for %s", ipv4)
			if miss == nil {
				miss = &expandMiss{
					sname: sname,
					sinfo: sinfo,
					nport: nport,
				}
			}
			miss.eps = append(miss.eps, ep)
			continue
		}

		flags := rt.Flags()
		// Include only remote workloads.
		if flags&routes.FlagWorkload != 0 && flags&routes.FlagLocal == 0 {
			nodeIP := rt.NextHop().(ip.V4Addr)

			ipToEp[nodeIP] = append(ipToEp[nodeIP], ep)
			if log.GetLevel() >= log.DebugLevel {
				log.Debugf("found rt %s for remote dest %s", nodeIP, ipv4)
			}
		}
	}
	return ipToEp, miss
}

func (s *Syncer) applyDerived(
	sname k8sp.ServicePortName,
	t svcType,
	sinfo k8sp.ServicePort,
) error {

	svc, ok := s.newSvcMap[getSvcKey(sname, "")]
	if !ok {
		// this should not happen
		return errors.Errorf("no ClusterIP for derived service type %d", t)
	}

	var skey svcKey
	count := svc.count
	local := svc.localCount

	skey = getSvcKey(sname, getSvcKeyExtra(t, sinfo.ClusterIP().String()))
	flags := uint32(0)

	switch t {
	case svcTypeNodePort, svcTypeLoadBalancer, svcTypeNodePortRemote:
		if sinfo.ExternalPolicyLocal() {
			flags |= nat.NATFlgExternalLocal
		}
		if sinfo.InternalPolicyLocal() {
			flags |= nat.NATFlgInternalLocal
		}
	}

	newInfo := svcInfo{
		id:         svc.id,
		count:      count,
		localCount: local,
		svc:        sinfo,
	}

	if err := s.writeSvc(sinfo, svc.id, count, local, flags); err != nil {
		return err
	}
	if svcTypeLoadBalancer == t || svcTypeExternalIP == t {
		err := s.writeLBSrcRangeSvcNATKeys(sinfo, svc.id, count, local, flags)
		if err != nil {
			log.Debug("Failed to write LB source range NAT keys")
		}
	}

	s.newSvcMap[skey] = newInfo
	if log.GetLevel() >= log.DebugLevel {
		log.Debugf("applied a derived service %s update: sinfo=%+v", skey, s.newSvcMap[skey])
	}

	return nil
}

func (s *Syncer) apply(state DPSyncerState) error {
	log.Infof("Applying new state, %d service", len(state.SvcMap))
	log.Debugf("Applying new state, %v", state)

	// we need to copy the maps from the new state to compute the diff in the
	// next call. We cannot keep the provided maps as the generic k8s proxy code
	// updates them. This function is called with a lock held so we are safe
	// here and now.
	s.newSvcMap = make(map[svcKey]svcInfo, len(state.SvcMap))
	s.newEpsMap = make(k8sp.EndpointsMap, len(state.EpsMap))

	var expNPMisses []*expandMiss

	// Start with a completely empty slate (in memory).  We'll then repopulate both maps from scratch and
	// let CachingMap calculate deltas...
	s.bpfSvcs.DeleteAllDesired()
	s.bpfEps.DeleteAllDesired()

	// insert or update existing services
	for sname, sinfo := range state.SvcMap {
		log.WithField("service", sname).Debug("Applying service")
		skey := getSvcKey(sname, "")

		eps := make([]k8sp.Endpoint, 0, len(state.EpsMap[sname]))
		for _, ep := range state.EpsMap[sname] {
			if ep.IsReady() {
				eps = append(eps, ep)
			}
		}

		err := s.applySvc(skey, sinfo, eps)
		if err != nil {
			return err
		}

		for _, lbIP := range sinfo.LoadBalancerIPStrings() {
			if lbIP != "" {
				extInfo := serviceInfoFromK8sServicePort(sinfo)
				extInfo.clusterIP = net.ParseIP(lbIP)
				err := s.applyDerived(sname, svcTypeLoadBalancer, extInfo)
				if err != nil {
					log.Errorf("failed to apply LoadBalancer IP %s for service %s : %s", lbIP, sname, err)
					continue
				}
				log.Debugf("LB status IP %s", lbIP)
			}
		}
		// N.B. we assume that k8s provide us with no duplicities
		for _, extIP := range sinfo.ExternalIPStrings() {
			extInfo := serviceInfoFromK8sServicePort(sinfo)
			extInfo.clusterIP = net.ParseIP(extIP)
			err := s.applyDerived(sname, svcTypeExternalIP, extInfo)
			if err != nil {
				log.Errorf("failed to apply ExternalIP %s for service %s : %s", extIP, sname, err)
				continue
			}
		}

		if nport := sinfo.NodePort(); nport != 0 {
			for _, npip := range s.nodePortIPs {
				npInfo := serviceInfoFromK8sServicePort(sinfo)
				npInfo.clusterIP = npip
				npInfo.port = nport
				if npip.Equal(podNPIP) && sinfo.InternalPolicyLocal() {
					// do not program the meta entry, program each node
					// separately
					continue
				}
				err := s.applyDerived(sname, svcTypeNodePort, npInfo)
				if err != nil {
					log.Errorf("failed to apply NodePort %s for service %s : %s", npip, sname, err)
					continue
				}
			}
			if sinfo.InternalPolicyLocal() {
				if miss := s.expandAndApplyNodePorts(sname, sinfo, eps, nport, s.rt.Lookup); miss != nil {
					expNPMisses = append(expNPMisses, miss)
				}
			}
		}
	}

	// Delete any front-ends first so the backends become unreachable.
	err := s.bpfSvcs.ApplyDeletionsOnly()
	if err != nil {
		return err
	}
	// Update the backend maps so that any new backends become available before we update the frontends to use them.
	err = s.bpfEps.ApplyUpdatesOnly()
	if err != nil {
		return err
	}
	// Update the frontends, after this is done we should be handling packets correctly.
	err = s.bpfSvcs.ApplyUpdatesOnly()
	if err != nil {
		return err
	}
	// Remove any unused backends.
	err = s.bpfEps.ApplyDeletionsOnly()
	if err != nil {
		return err
	}

	log.Info("new state written")

	s.runExpandNPFixup(expNPMisses)

	return nil
}

// Apply applies the new state
func (s *Syncer) Apply(state DPSyncerState) error {
	if !s.synced {
		log.Infof("Loading BPF map state from dataplane")
		if err := s.startupSync(state); err != nil {
			return errors.WithMessage(err, "startup sync")
		}
		log.Infof("Loaded BPF map state from dataplane")
		s.mapsLck.Lock()
	} else {
		// if we were not synced yet, the fixer cannot run yet
		s.StopExpandNPFixup()

		s.mapsLck.Lock()
		s.prevSvcMap = s.newSvcMap
		s.prevEpsMap = s.newEpsMap
	}

	defer s.mapsLck.Unlock()

	// preallocate maps to track sticky services for cleanup
	s.stickySvcs = make(map[nat.FrontEndAffinityKey]stickyFrontend)
	s.stickyEps = make(map[uint32]map[nat.BackendValue]struct{})

	defer func() {
		// not needed anymore
		s.stickySvcs = nil
		s.stickyEps = nil
	}()

	if err := s.apply(state); err != nil {
		// dont bother to cleanup affinity since we do not know in what state we
		// are anyway. Will get resolved once we get in a good state
		return err
	}

	// we are fully synced now
	if !s.synced {
		s.synced = true
	}

	// We wrote all updates, no one will create new records in affinity table
	// that we would clean up now, so do it!
	return s.cleanupSticky()
}

func (s *Syncer) updateService(skey svcKey, sinfo k8sp.ServicePort, id uint32, eps []k8sp.Endpoint) (int, int, error) {
	cpEps := make([]k8sp.Endpoint, 0, len(eps))

	cnt := 0
	local := 0

	if sinfo.SessionAffinityType() == v1.ServiceAffinityClientIP {
		// since we write the backend before we write the frontend, we need to
		// preallocate the map for it
		s.stickyEps[id] = make(map[nat.BackendValue]struct{})
	}

	for _, ep := range eps {
		if !ep.GetIsLocal() {
			continue
		}
		if err := s.writeSvcBackend(id, uint32(cnt), ep); err != nil {
			return 0, 0, err
		}

		cpEps = append(cpEps, ep)
		cnt++
		local++
	}

	for _, ep := range eps {
		if ep.GetIsLocal() {
			continue
		}
		if err := s.writeSvcBackend(id, uint32(cnt), ep); err != nil {
			return 0, 0, err
		}

		cpEps = append(cpEps, ep)
		cnt++
	}

	if err := s.writeSvc(sinfo, id, cnt, local, 0); err != nil {
		return 0, 0, err
	}

	// svcTypeNodePortRemote is semi-primary service - it has a different set of
	// backends for NAT (hence primary) but is also derived and would overwrite
	// the primary service for connection cleaning.
	//
	// As a result we are a bit more conservative in which connections we break.
	// Even if a backend is technically not reachable through the nodeport due
	// to the Local vs. Cluster traffic policy, there is no harm if include also
	// those backends and possible do not break connections that cannot happen.
	if !hasSvcKeyExtra(skey, svcTypeNodePortRemote) {
		s.newEpsMap[skey.sname] = cpEps
	}

	return cnt, local, nil
}

func (s *Syncer) writeSvcBackend(svcID uint32, idx uint32, ep k8sp.Endpoint) error {
	if log.GetLevel() >= log.DebugLevel {
		log.WithFields(log.Fields{
			"svcID": svcID,
			"idx":   idx,
			"ep":    ep,
		}).Debug("Writing service backend.")
	}
	ip := net.ParseIP(ep.IP())

	key := nat.NewNATBackendKey(svcID, uint32(idx))

	tgtPort, err := ep.Port()
	if err != nil {
		return errors.Errorf("no port for endpoint %q: %s", ep, err)
	}
	val := nat.NewNATBackendValue(ip, uint16(tgtPort))
	s.bpfEps.SetDesired(key, val)

	if s.stickyEps[svcID] != nil {
		s.stickyEps[svcID][val] = struct{}{}
	}

	return nil
}

func getSvcNATKey(svc k8sp.ServicePort) (nat.FrontendKey, error) {
	ip := svc.ClusterIP()
	port := svc.Port()
	proto, err := ProtoV1ToInt(svc.Protocol())
	if err != nil {
		return nat.FrontendKey{}, err
	}

	key := nat.NewNATKey(ip, uint16(port), proto)
	return key, nil
}

func getSvcNATKeyLBSrcRange(svc k8sp.ServicePort) ([]nat.FrontendKey, error) {
	ipaddr := svc.ClusterIP()
	port := svc.Port()
	loadBalancerSourceRanges := svc.LoadBalancerSourceRanges()
	if log.GetLevel() >= log.DebugLevel {
		log.Debugf("loadbalancer %v", loadBalancerSourceRanges)
	}
	proto, err := ProtoV1ToInt(svc.Protocol())
	if err != nil {
		return nil, err
	}

	keys := make([]nat.FrontendKey, 0, len(loadBalancerSourceRanges))

	for _, src := range loadBalancerSourceRanges {
		// Ignore IPv6 addresses
		if strings.Contains(src, ":") {
			continue
		}
		key := nat.NewNATKeySrc(ipaddr, uint16(port), proto, ip.MustParseCIDROrIP(src).(ip.V4CIDR))
		keys = append(keys, key)
	}
	return keys, nil
}

func (s *Syncer) writeLBSrcRangeSvcNATKeys(svc k8sp.ServicePort, svcID uint32, count, local int, flags uint32) error {
	var key nat.FrontendKey
	affinityTimeo := uint32(0)
	if svc.SessionAffinityType() == v1.ServiceAffinityClientIP {
		affinityTimeo = uint32(svc.StickyMaxAgeSeconds())
	}

	if len(svc.LoadBalancerSourceRanges()) == 0 {
		return nil
	}
	keys, err := getSvcNATKeyLBSrcRange(svc)
	if err != nil {
		return err
	}
	val := nat.NewNATValueWithFlags(svcID, uint32(count), uint32(local), affinityTimeo, flags)
	for _, key := range keys {
		if log.GetLevel() >= log.DebugLevel {
			log.Debugf("bpf map writing %s:%s", key, val)
		}
		s.bpfSvcs.SetDesired(key, val)
	}
	key, err = getSvcNATKey(svc)
	if err != nil {
		return err
	}
	val = nat.NewNATValue(svcID, nat.BlackHoleCount, uint32(0), uint32(0))
	s.bpfSvcs.SetDesired(key, val)
	return nil
}

func (s *Syncer) writeSvc(svc k8sp.ServicePort, svcID uint32, count, local int, flags uint32) error {
	key, err := getSvcNATKey(svc)
	if err != nil {
		return err
	}

	affinityTimeo := uint32(0)
	if svc.SessionAffinityType() == v1.ServiceAffinityClientIP {
		affinityTimeo = uint32(svc.StickyMaxAgeSeconds())
	}

	val := nat.NewNATValueWithFlags(svcID, uint32(count), uint32(local), affinityTimeo, flags)

	if log.GetLevel() >= log.DebugLevel {
		log.Debugf("bpf map writing %s:%s", key, val)
	}
	s.bpfSvcs.SetDesired(key, val)

	var affkey nat.FrontEndAffinityKey
	copy(affkey[:], key.Affinitykey())
	// we must have written the backends by now so the map exists
	if s.stickyEps[svcID] != nil {
		s.stickySvcs[affkey] = stickyFrontend{
			id:    svcID,
			timeo: time.Duration(affinityTimeo) * time.Second,
		}
	}

	return nil
}

// ProtoV1ToInt translates k8s v1.Protocol to its IANA number and returns
// error if the proto is not recognized
func ProtoV1ToInt(p v1.Protocol) (uint8, error) {
	switch p {
	case v1.ProtocolTCP:
		return 6, nil
	case v1.ProtocolUDP:
		return 17, nil
	case v1.ProtocolSCTP:
		return 132, nil
	}

	return 0, errors.Errorf("unknown protocol %q", p)
}

// ProtoV1ToIntPanic translates k8s v1.Protocol to its IANA number and panics if
// the protocol is not recognized
func ProtoV1ToIntPanic(p v1.Protocol) uint8 {
	pn, err := ProtoV1ToInt(p)
	if err != nil {
		panic(err)
	}
	return pn
}

func (s *Syncer) newSvcID() uint32 {
	// TODO we may run out of IDs unless we restart to recycle
	id := s.nextSvcID
	s.nextSvcID++
	return id
}

func (s *Syncer) matchBpfSvc(bpfSvc nat.FrontendKey, k8sSvc k8sp.ServicePortName, k8sInfo k8sp.ServicePort) *svcKey {
	matchNP := func() *svcKey {
		if bpfSvc.Port() == uint16(k8sInfo.NodePort()) {
			for _, nip := range s.nodePortIPs {
				if bpfSvc.Addr().Equal(nip) {
					skey := &svcKey{
						sname: k8sSvc,
						extra: getSvcKeyExtra(svcTypeNodePort, nip.String()),
					}
					if log.GetLevel() >= log.DebugLevel {
						log.Debugf("resolved %s as %s", bpfSvc, skey)
					}
					return skey
				}
			}
		}

		return nil
	}

	if bpfSvc.Port() != uint16(k8sInfo.Port()) {
		if sk := matchNP(); sk != nil {
			return sk
		}
		return nil
	}
	matchLBSrcIP := func() bool {
		// External IP with zero Src CIDR is a valid entry and should not be considered
		// as stale
		if bpfSvc.SrcCIDR() == nat.ZeroCIDR {
			return true
		}
		// If the service does not have any source address range, treat all the entries with
		// src cidr as stale.
		if len(k8sInfo.LoadBalancerSourceRanges()) == 0 {
			return false
		}
		// If the service does have source range specified, look for a match
		for _, srcip := range k8sInfo.LoadBalancerSourceRanges() {
			if strings.Contains(srcip, ":") {
				continue
			}
			cidr := ip.MustParseCIDROrIP(srcip).(ip.V4CIDR)
			if cidr == bpfSvc.SrcCIDR() {
				return true
			}
		}
		return false
	}

	if bpfSvc.Addr().String() == k8sInfo.ClusterIP().String() {
		if bpfSvc.SrcCIDR() == nat.ZeroCIDR {
			skey := &svcKey{
				sname: k8sSvc,
			}
			if log.GetLevel() >= log.DebugLevel {
				log.Debugf("resolved %s as %s", bpfSvc, skey)
			}
			return skey
		}
	}

	for _, eip := range k8sInfo.ExternalIPStrings() {
		if bpfSvc.Addr().String() == eip {
			if matchLBSrcIP() {
				skey := &svcKey{
					sname: k8sSvc,
					extra: getSvcKeyExtra(svcTypeExternalIP, eip),
				}
				if log.GetLevel() >= log.DebugLevel {
					log.Debugf("resolved %s as %s", bpfSvc, skey)
				}
				return skey
			}
		}
	}

	for _, lbip := range k8sInfo.LoadBalancerIPStrings() {
		if lbip != "" {
			if bpfSvc.Addr().String() == lbip {
				if matchLBSrcIP() {
					skey := &svcKey{
						sname: k8sSvc,
						extra: getSvcKeyExtra(svcTypeLoadBalancer, lbip),
					}
					log.Debugf("resolved %s as %s", bpfSvc, skey)
					return skey
				}
			}
		}
	}
	// just in case the NodePort port is the same as the Port
	if sk := matchNP(); sk != nil {
		return sk
	}

	return nil
}

func (s *Syncer) runExpandNPFixup(misses []*expandMiss) {
	if len(misses) == 0 {
		return
	}
	expFixupStop := make(chan struct{})
	if s.expFixupStop != nil {
		log.Error("BUG: About to start node port fixup goroutine but one already seems to be running. " +
			"Stopping the old one.")
		close(s.expFixupStop)
	}
	s.expFixupStop = expFixupStop
	s.expFixupWg.Add(1)

	// start the fixer routine and exit
	go func() {
		log.Debug("fixer started")
		defer s.expFixupWg.Done()
		defer log.Debug("fixer exited")
		s.mapsLck.Lock()
		defer s.mapsLck.Unlock()

		ctx, cancel := context.WithCancel(context.Background())
		defer cancel()

		// monitor if we should stop and if so, cancel any work
		go func() {
			select {
			case <-s.stop:
				cancel()
			case <-expFixupStop:
				cancel()
			case <-ctx.Done():
				// do nothing, we exited, work is done, just quit
			}
		}()

		for {
			log.Debugf("%d misses unresolved", len(misses))

			// We do one pass rightaway since we cannot know whether there
			// was an update or not before we got here
			s.rt.WaitAfter(ctx, func(lookup func(addr ip.Addr) (routes.Value, bool)) bool {
				log.Debug("Woke up")
				missesChanged := false
				var again []*expandMiss
				for _, m := range misses {
					if _, miss := s.expandNodePorts(m.sname, m.sinfo, m.eps, m.nport, lookup); miss != nil {
						again = append(again, miss)
						if !reflect.DeepEqual(m.eps, miss.eps) {
							missesChanged = true
						}
					} else {
						missesChanged = true
					}
				}

				if missesChanged && s.triggerFn != nil {
					log.Debug("Triggering a sync...")
					s.triggerFn()
				} else {
					log.Debug("Not triggering sync")
				}
				misses = again

				return len(misses) == 0 // block or not block
			})

			if len(misses) == 0 || ctx.Err() != nil {
				return
			}
		}
	}()
}

func (s *Syncer) SetTriggerFn(f func()) {
	s.triggerFn = f
}

func (s *Syncer) StopExpandNPFixup() {
	// If there was an error before we started ExpandNPFixup, there is nothing to stop
	if s.expFixupStop != nil {
		close(s.expFixupStop)
		s.expFixupWg.Wait()
		s.expFixupStop = nil
	}
}

// Stop stops the syncer
func (s *Syncer) Stop() {
	s.stopOnce.Do(func() {
		log.Info("Syncer stopping")
		close(s.stop)
		s.expFixupWg.Wait()
		log.Info("Syncer stopped")
	})
}

func (s *Syncer) cleanupSticky() error {
	debug := log.GetLevel() >= log.DebugLevel
	_ = debug // Work around linter false-positive.

	var (
		key nat.AffinityKey
		val nat.AffinityValue
	)

	ks := len(nat.AffinityKey{})
	vs := len(nat.AffinityValue{})

	now := time.Duration(bpf.KTimeNanos())

	err := s.bpfAff.Iter(func(k, v []byte) bpf.IteratorAction {
		copy(key[:], k[:ks])
		copy(val[:], v[:vs])

		fend, ok := s.stickySvcs[key.FrontendAffinityKey()]
		if !ok {
			if debug {
				log.Debugf("cleaning affinity %v:%v - no such a service", key, val)
			}
			return bpf.IterDelete
		}

		if _, ok := s.stickyEps[fend.id][val.Backend()]; !ok {
			if debug {
				log.Debugf("cleaning affinity %v:%v - no such a backend", key, val)
			}
			return bpf.IterDelete
		}

		if now-val.Timestamp() > fend.timeo {
			if debug {
				log.Debugf("cleaning affinity %v:%v - expired", key, val)
			}
			return bpf.IterDelete
		}
		if debug {
			log.Debugf("cleaning affinity %v:%v - keeping", key, val)
		}
		return bpf.IterNone
	})
	if err != nil {
		return errors.Errorf("NAT affinity map iterator failed: %s", err)
	}
	return nil
}

// ConntrackFrontendHasBackend returns true if the given front-backend pair exists
func (s *Syncer) ConntrackFrontendHasBackend(ip net.IP, port uint16,
	backendIP net.IP, backendPort uint16, proto uint8) (ret bool) {

	if log.GetLevel() >= log.DebugLevel {
		defer func() {
			log.WithField("ret", ret).Debug("ConntrackFrontendHasBackend")
		}()
	}

	id, ok := s.activeSvcsMap[ipPortProto{ipPort{ip.String(), int(port)}, proto}]
	if !ok {
		// Double check if it is a nodeport as if we are on the node that has
		// the backing pod for a nodeport and the nodeport was forwarded here,
		// the frontend is different.
		id, ok = s.activeSvcsMap[ipPortProto{ipPort{"255.255.255.255", int(port)}, proto}]
		if !ok {
			return false
		}
	}

	backends := s.activeEpsMap[id]
	if backends == nil {
		return false
	}

	_, ok = backends[ipPort{backendIP.String(), int(backendPort)}]

	return ok
}

// ConntrackScanStart excludes Apply from running and builds the active maps from
// ConntrackFrontendHasBackend
func (s *Syncer) ConntrackScanStart() {
	log.Debug("ConntrackScanStart")
	s.mapsLck.Lock()

	s.activeSvcsMap = make(map[ipPortProto]uint32)
	s.activeEpsMap = make(map[uint32]map[ipPort]struct{})

	// build active maps for conntrack cleaning
	for skey, sinfo := range s.newSvcMap {
		if sinfo.count == 0 {
			continue
		}

		if isSvcKeyDerived(skey) {
			s.addActiveEps(sinfo.id, sinfo.svc, nil)
		} else {
			s.addActiveEps(sinfo.id, sinfo.svc, s.newEpsMap[skey.sname])
		}
	}
}

// ConntrackScanEnd enables Apply and frees active maps
func (s *Syncer) ConntrackScanEnd() {
	// free the maps when the iteration is complete
	s.activeSvcsMap = nil
	s.activeEpsMap = nil
	s.mapsLck.Unlock()
	log.Debug("ConntrackScanEnd")
}

func serviceInfoFromK8sServicePort(sport k8sp.ServicePort) *serviceInfo {
	sinfo := new(serviceInfo)

	// create a shallow copy
	sinfo.clusterIP = sport.ClusterIP()
	sinfo.port = sport.Port()
	sinfo.protocol = sport.Protocol()
	sinfo.nodePort = sport.NodePort()
	sinfo.sessionAffinityType = sport.SessionAffinityType()
	sinfo.stickyMaxAgeSeconds = sport.StickyMaxAgeSeconds()
	sinfo.externalIPs = sport.ExternalIPStrings()
	sinfo.loadBalancerIPStrings = sport.LoadBalancerIPStrings()
	sinfo.loadBalancerSourceRanges = sport.LoadBalancerSourceRanges()
	sinfo.healthCheckNodePort = sport.HealthCheckNodePort()
	sinfo.nodeLocalExternal = sport.ExternalPolicyLocal()
	sinfo.nodeLocalInternal = sport.InternalPolicyLocal()
	sinfo.hintsAnnotation = sport.HintsAnnotation()
	sinfo.internalTrafficPolicy = sport.InternalTrafficPolicy()

	return sinfo
}

type serviceInfo struct {
	clusterIP                net.IP
	port                     int
	protocol                 v1.Protocol
	nodePort                 int
	sessionAffinityType      v1.ServiceAffinity
	stickyMaxAgeSeconds      int
	externalIPs              []string
	loadBalancerSourceRanges []string
	loadBalancerIPStrings    []string
	healthCheckNodePort      int
	nodeLocalExternal        bool
	nodeLocalInternal        bool
	hintsAnnotation          string
	internalTrafficPolicy    *v1.ServiceInternalTrafficPolicyType
}

// ExternallyAccessible returns true if the service port is reachable via something
// other than ClusterIP (NodePort/ExternalIP/LoadBalancer)
func (info *serviceInfo) ExternallyAccessible() bool {
	return info.NodePort() != 0 || len(info.LoadBalancerIPStrings()) != 0 || len(info.ExternalIPStrings()) != 0
}

// UsesClusterEndpoints returns true if the service port ever sends traffic to
// endpoints based on "Cluster" traffic policy
func (info *serviceInfo) UsesClusterEndpoints() bool {
	// The service port uses Cluster endpoints if the internal traffic policy is "Cluster",
	// or if it accepts external traffic at all. (Even if the external traffic policy is
	// "Local", we need Cluster endpoints to implement short circuiting.)
	return !info.InternalPolicyLocal() || info.ExternallyAccessible()
}

// UsesLocalEndpoints returns true if the service port ever sends traffic to
// endpoints based on "Local" traffic policy
func (info *serviceInfo) UsesLocalEndpoints() bool {
	return info.InternalPolicyLocal() || (info.ExternalPolicyLocal() && info.ExternallyAccessible())
}

// String is part of ServicePort interface.
func (info *serviceInfo) String() string {
	return fmt.Sprintf("%s:%d/%s", info.clusterIP, info.port, info.protocol)
}

// ClusterIP is part of ServicePort interface.
func (info *serviceInfo) ClusterIP() net.IP {
	return info.clusterIP
}

// Port is part of ServicePort interface.
func (info *serviceInfo) Port() int {
	return info.port
}

// SessionAffinityType is part of the ServicePort interface.
func (info *serviceInfo) SessionAffinityType() v1.ServiceAffinity {
	return info.sessionAffinityType
}

// StickyMaxAgeSeconds is part of the ServicePort interface
func (info *serviceInfo) StickyMaxAgeSeconds() int {
	return info.stickyMaxAgeSeconds
}

// Protocol is part of ServicePort interface.
func (info *serviceInfo) Protocol() v1.Protocol {
	return info.protocol
}

// LoadBalancerSourceRanges is part of ServicePort interface
func (info *serviceInfo) LoadBalancerSourceRanges() []string {
	return info.loadBalancerSourceRanges
}

// HealthCheckNodePort is part of ServicePort interface.
func (info *serviceInfo) HealthCheckNodePort() int {
	return info.healthCheckNodePort
}

// NodePort is part of the ServicePort interface.
func (info *serviceInfo) NodePort() int {
	return info.nodePort
}

// ExternalIPStrings is part of ServicePort interface.
func (info *serviceInfo) ExternalIPStrings() []string {
	return info.externalIPs
}

// LoadBalancerIPStrings is part of ServicePort interface.
func (info *serviceInfo) LoadBalancerIPStrings() []string {
	return info.loadBalancerIPStrings
}

// ExternalPolicyLocal returns if a service has only node local endpoints for external traffic.
func (info *serviceInfo) ExternalPolicyLocal() bool {
	return info.nodeLocalExternal
}

// InternalPolicyLocal returns if a service has only node local endpoints for internal traffic.
func (info *serviceInfo) InternalPolicyLocal() bool {
	return info.nodeLocalInternal
}

// HintsAnnotation is part of ServicePort interface.
func (info *serviceInfo) HintsAnnotation() string {
	return info.hintsAnnotation
}

// InternalTrafficPolicy is part of ServicePort interface
func (info *serviceInfo) InternalTrafficPolicy() *v1.ServiceInternalTrafficPolicyType {
	return info.internalTrafficPolicy
}

// K8sServicePortOption defines options for NewK8sServicePort
type K8sServicePortOption func(interface{})

// NewK8sServicePort creates a new k8s ServicePort
func NewK8sServicePort(clusterIP net.IP, port int, proto v1.Protocol,
	opts ...K8sServicePortOption) k8sp.ServicePort {

	x := &serviceInfo{
		clusterIP: clusterIP,
		port:      port,
		protocol:  proto,
	}

	for _, o := range opts {
		o(x)
	}
	return x
}

// ServicePortEqual compares if two k8sp.ServicePort are equal, that is all of
// their methods return equal values, i.e., they may differ in implementation,
// but present themselves equally. String() is not considered as it may differ
// for debugging reasons.
func ServicePortEqual(a, b k8sp.ServicePort) bool {
	return a.ClusterIP().Equal(b.ClusterIP()) &&
		a.Port() == b.Port() &&
		a.SessionAffinityType() == b.SessionAffinityType() &&
		a.StickyMaxAgeSeconds() == b.StickyMaxAgeSeconds() &&
		a.Protocol() == b.Protocol() &&
		a.HealthCheckNodePort() == b.HealthCheckNodePort() &&
		a.NodePort() == b.NodePort() &&
		a.ExternalPolicyLocal() == b.ExternalPolicyLocal() &&
		a.InternalPolicyLocal() == b.InternalPolicyLocal() &&
		a.HintsAnnotation() == b.HintsAnnotation() &&
		a.InternalTrafficPolicy() == b.InternalTrafficPolicy() &&
		stringsEqual(a.ExternalIPStrings(), b.ExternalIPStrings()) &&
		stringsEqual(a.LoadBalancerIPStrings(), b.LoadBalancerIPStrings()) &&
		stringsEqual(a.LoadBalancerSourceRanges(), b.LoadBalancerSourceRanges())
}

func stringsEqual(a, b []string) bool {
	if len(a) != len(b) {
		return false
	}

	// optimize for a common case to avoid allocating a map
	if len(a) == 1 {
		return a[0] == b[0]
	}

	m := make(map[string]struct{}, len(a))
	for _, s := range a {
		m[s] = struct{}{}
	}

	for _, s := range b {
		if _, ok := m[s]; !ok {
			return false
		}
	}

	return true
}

// K8sSvcWithLoadBalancerIPs set LoadBalancerIPStrings
func K8sSvcWithLoadBalancerIPs(ips []string) K8sServicePortOption {
	return func(s interface{}) {
		s.(*serviceInfo).loadBalancerIPStrings = ips
	}
}

// K8sSvcWithLBSourceRangeIPs sets LBSourcePortRangeIPs
func K8sSvcWithLBSourceRangeIPs(ips []string) K8sServicePortOption {
	return func(s interface{}) {
		s.(*serviceInfo).loadBalancerSourceRanges = ips
	}
}

// K8sSvcWithExternalIPs sets ExternalIPs
func K8sSvcWithExternalIPs(ips []string) K8sServicePortOption {
	return func(s interface{}) {
		s.(*serviceInfo).externalIPs = ips
	}
}

// K8sSvcWithNodePort sets the nodeport
func K8sSvcWithNodePort(np int) K8sServicePortOption {
	return func(s interface{}) {
		s.(*serviceInfo).nodePort = np
	}
}

// K8sSvcWithLocalOnly sets OnlyNodeLocalEndpoints=true
func K8sSvcWithLocalOnly() K8sServicePortOption {
	return func(s interface{}) {
		s.(*serviceInfo).nodeLocalExternal = true
		s.(*serviceInfo).nodeLocalInternal = true
	}
}

// K8sSvcWithStickyClientIP sets ServiceAffinityClientIP to seconds
func K8sSvcWithStickyClientIP(seconds int) K8sServicePortOption {
	return func(s interface{}) {
		s.(*serviceInfo).stickyMaxAgeSeconds = seconds
		s.(*serviceInfo).sessionAffinityType = v1.ServiceAffinityClientIP
	}
}
