ziti/controller/network/network.go

/*
	Copyright NetFoundry Inc.

	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

	https://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 network

import (
	"bytes"
	"compress/gzip"
	"encoding/json"
	"errors"
	"fmt"
	"math"
	"os"
	"runtime/debug"
	"slices"
	"sort"
	"strings"
	"sync"
	"time"

	"github.com/michaelquigley/pfxlog"
	"github.com/openziti/channel/v4/protobufs"
	"github.com/openziti/channel/v4"
	"github.com/openziti/foundation/v2/concurrenz"
	"github.com/openziti/foundation/v2/debugz"
	"github.com/openziti/foundation/v2/goroutines"
	"github.com/openziti/foundation/v2/versions"
	"github.com/openziti/identity"
	"github.com/openziti/metrics"
	"github.com/openziti/metrics/metrics_pb"
	"github.com/openziti/ziti/v2/controller/storage/boltz"
	"github.com/openziti/ziti/v2/controller/storage/objectz"
	"github.com/openziti/ziti/v2/common/ctrl_msg"
	"github.com/openziti/ziti/v2/common/inspect"
	"github.com/openziti/ziti/v2/common/logcontext"
	fabricMetrics "github.com/openziti/ziti/v2/common/metrics"
	"github.com/openziti/ziti/v2/common/pb/cmd_pb"
	"github.com/openziti/ziti/v2/common/pb/ctrl_pb"
	"github.com/openziti/ziti/v2/common/pb/mgmt_pb"
	"github.com/openziti/ziti/v2/common/trace"
	"github.com/openziti/ziti/v2/controller/command"
	"github.com/openziti/ziti/v2/controller/config"
	"github.com/openziti/ziti/v2/controller/db"
	"github.com/openziti/ziti/v2/controller/event"
	"github.com/openziti/ziti/v2/controller/idgen"
	"github.com/openziti/ziti/v2/controller/model"
	"github.com/openziti/ziti/v2/controller/xt"
	"github.com/sirupsen/logrus"
	"github.com/teris-io/shortid"
	"go.etcd.io/bbolt"
	"google.golang.org/protobuf/proto"
)

const SmartRerouteAttempt = 99969996

// Config provides the values needed to create a Network instance
type Config interface {
	GetId() *identity.TokenId
	GetMetricsRegistry() metrics.Registry
	GetOptions() *config.NetworkConfig
	GetCommandDispatcher() command.Dispatcher
	GetDb() boltz.Db
	GetVersionProvider() versions.VersionProvider
	GetEventDispatcher() event.Dispatcher
	GetCloseNotify() <-chan struct{}
}

type InspectTarget func(string) (bool, *string, error)

// CtrlDialerValidator is a function that validates ctrl dialer states and returns per-router details.
type CtrlDialerValidator func() ([]*mgmt_pb.ControllerDialerDetails, error)

type Network struct {
	*model.Managers
	env                    model.Env
	nodeId                 string
	options                *config.NetworkConfig
	routeSenderController  *routeSenderController
	eventDispatcher        event.Dispatcher
	traceController        trace.Controller
	routerPresenceHandlers concurrenz.CopyOnWriteSlice[model.RouterPresenceHandler]
	capabilities           []string
	closeNotify            <-chan struct{}
	watchdogCh             chan struct{}
	lock                   sync.Mutex
	strategyRegistry       xt.Registry
	lastSnapshot           time.Time
	metricsRegistry        metrics.Registry
	VersionProvider        versions.VersionProvider

	serviceEventMetrics          metrics.UsageRegistry
	serviceDialSuccessCounter    metrics.IntervalCounter
	serviceDialFailCounter       metrics.IntervalCounter
	serviceDialTimeoutCounter    metrics.IntervalCounter
	serviceDialOtherErrorCounter metrics.IntervalCounter

	serviceTerminatorTimeoutCounter           metrics.IntervalCounter
	serviceTerminatorConnectionRefusedCounter metrics.IntervalCounter
	serviceInvalidTerminatorCounter           metrics.IntervalCounter
	serviceMisconfiguredTerminatorCounter     metrics.IntervalCounter

	config Config

	Inspections         *InspectionsManager
	RouterMessaging     *RouterMessaging
	inspectionTargets   concurrenz.CopyOnWriteSlice[InspectTarget]
	ctrlDialerValidator CtrlDialerValidator
}

func NewNetwork(config Config, env model.Env) (*Network, error) {
	metricsConfig := metrics.DefaultUsageRegistryConfig(config.GetId().Token, config.GetCloseNotify())
	if config.GetOptions().IntervalAgeThreshold != 0 {
		metricsConfig.IntervalAgeThreshold = config.GetOptions().IntervalAgeThreshold
		logrus.Infof("set interval age threshold to '%v'", config.GetOptions().IntervalAgeThreshold)
	}
	serviceEventMetrics := metrics.NewUsageRegistry(metricsConfig)

	network := &Network{
		env:                   env,
		Managers:              env.GetManagers(),
		nodeId:                config.GetId().Token,
		options:               config.GetOptions(),
		routeSenderController: newRouteSenderController(),
		eventDispatcher:       config.GetEventDispatcher(),
		traceController:       trace.NewController(config.GetCloseNotify()),
		closeNotify:           config.GetCloseNotify(),
		watchdogCh:            make(chan struct{}, 1),
		strategyRegistry:      xt.GlobalRegistry(),
		lastSnapshot:          time.Now().Add(-time.Hour),
		metricsRegistry:       config.GetMetricsRegistry(),
		VersionProvider:       config.GetVersionProvider(),

		serviceEventMetrics:          serviceEventMetrics,
		serviceDialSuccessCounter:    serviceEventMetrics.IntervalCounter("service.dial.success", time.Minute),
		serviceDialFailCounter:       serviceEventMetrics.IntervalCounter("service.dial.fail", time.Minute),
		serviceDialTimeoutCounter:    serviceEventMetrics.IntervalCounter("service.dial.timeout", time.Minute),
		serviceDialOtherErrorCounter: serviceEventMetrics.IntervalCounter("service.dial.error_other", time.Minute),

		serviceTerminatorTimeoutCounter:           serviceEventMetrics.IntervalCounter("service.dial.terminator.timeout", time.Minute),
		serviceTerminatorConnectionRefusedCounter: serviceEventMetrics.IntervalCounter("service.dial.terminator.connection_refused", time.Minute),
		serviceInvalidTerminatorCounter:           serviceEventMetrics.IntervalCounter("service.dial.terminator.invalid", time.Minute),
		serviceMisconfiguredTerminatorCounter:     serviceEventMetrics.IntervalCounter("service.dial.terminator.misconfigured", time.Minute),

		config: config,
	}

	env.GetManagers().Command.Decoders.RegisterF(int32(cmd_pb.CommandType_SyncSnapshot), network.decodeSyncSnapshotCommand)

	routerCommPool, err := network.createRouterCommPool(config)
	if err != nil {
		return nil, err
	}
	network.Inspections = NewInspectionsManager(network)
	network.RouterMessaging = NewRouterMessaging(env, routerCommPool)

	env.GetManagers().Router.Store.AddEntityIdListener(network.HandleRouterDelete, boltz.EntityDeletedAsync)

	network.AddCapability("ziti.fabric")
	network.showOptions()
	network.relayControllerMetrics()
	network.AddRouterPresenceHandler(network.RouterMessaging)
	go network.RouterMessaging.run()

	return network, nil
}

func (self *Network) HandleRouterDelete(id string) {
	self.routerDeleted(id)
	self.RouterMessaging.RouterDeleted(id)
}

func (self *Network) decodeSyncSnapshotCommand(_ int32, data []byte) (command.Command, error) {
	msg := &cmd_pb.SyncSnapshotCommand{}
	if err := proto.Unmarshal(data, msg); err != nil {
		return nil, err
	}

	cmd := &command.SyncSnapshotCommand{
		TimelineId:   msg.SnapshotId,
		Snapshot:     msg.Snapshot,
		ClusterId:    msg.ClusterId,
		SnapshotSink: self.RestoreSnapshot,
	}

	return cmd, nil
}

func routerCommunicationsWorker(_ uint32, f func()) {
	f()
}

func (network *Network) createRouterCommPool(config Config) (goroutines.Pool, error) {
	poolConfig := goroutines.PoolConfig{
		QueueSize:   config.GetOptions().RouterComm.QueueSize,
		MinWorkers:  0,
		MaxWorkers:  config.GetOptions().RouterComm.MaxWorkers,
		IdleTime:    30 * time.Second,
		CloseNotify: config.GetCloseNotify(),
		PanicHandler: func(err interface{}) {
			pfxlog.Logger().WithField(logrus.ErrorKey, err).WithField("backtrace", string(debug.Stack())).Error("panic during message send to router")
		},
		WorkerFunction: routerCommunicationsWorker,
	}

	fabricMetrics.ConfigureGoroutinesPoolMetrics(&poolConfig, config.GetMetricsRegistry(), "pool.router.messaging")

	pool, err := goroutines.NewPool(poolConfig)
	if err != nil {
		return nil, fmt.Errorf("error creating router messaging pool (%w)", err)
	}
	return pool, nil
}

func (network *Network) relayControllerMetrics() {
	go func() {
		timer := time.NewTicker(network.options.MetricsReportInterval)
		defer timer.Stop()

		for {
			select {
			case <-timer.C:
				if msg := network.metricsRegistry.Poll(); msg != nil {
					network.eventDispatcher.AcceptMetricsMsg(msg)
				}
			case <-network.closeNotify:
				return
			}
		}
	}()
}

func (network *Network) InitServiceCounterDispatch(handler metrics.Handler) {
	network.serviceEventMetrics.StartReporting(handler, network.GetOptions().MetricsReportInterval, 10)
}

func (network *Network) GetAppId() string {
	return network.nodeId
}

func (network *Network) GetOptions() *config.NetworkConfig {
	return network.options
}

func (network *Network) GetDb() boltz.Db {
	return network.config.GetDb()
}

func (network *Network) GetStores() *db.Stores {
	return network.env.GetStores()
}

func (network *Network) GetConnectedRouter(routerId string) *model.Router {
	return network.Router.GetConnected(routerId)
}

// NewCtrlChanRouter returns the Router instance representing a new control-channel connection, with the
// channel recorded on it. Each connection gets its own instance, which is what lets the connect and
// disconnect paths tell two racing connections for one router apart.
func (network *Network) NewCtrlChanRouter(ch channel.Channel) (*model.Router, error) {
	return network.Router.NewCtrlChanRouter(ch)
}

func (network *Network) GetRouter(routerId string) (*model.Router, error) {
	return network.Router.Read(routerId)
}

func (network *Network) AllConnectedRouters() []*model.Router {
	return network.Router.AllConnected()
}

func (network *Network) GetLink(linkId string) (*model.Link, bool) {
	return network.Link.Get(linkId)
}

func (network *Network) GetAllLinks() []*model.Link {
	return network.Link.All()
}

func (network *Network) GetAllLinksForRouter(routerId string) []*model.Link {
	r := network.GetConnectedRouter(routerId)
	if r == nil {
		return nil
	}
	return r.GetLinks()
}

func (network *Network) GetCircuit(circuitId string) (*model.Circuit, bool) {
	return network.Circuit.Get(circuitId)
}

func (network *Network) GetAllCircuits() []*model.Circuit {
	return network.Circuit.All()
}

func (network *Network) GetCircuitStore() *objectz.ObjectStore[*model.Circuit] {
	return network.Circuit.GetStore()
}

func (network *Network) GetLinkStore() *objectz.ObjectStore[*model.Link] {
	return network.Link.GetStore()
}

func (network *Network) RouteResult(rs *RouteStatus) bool {
	return network.routeSenderController.forwardRouteResult(rs)
}

func (network *Network) newRouteSender(circuitId string) *routeSender {
	rs := newRouteSender(circuitId, network.options.RouteTimeout, network, network.Terminator)
	network.routeSenderController.addRouteSender(rs)
	return rs
}

func (network *Network) removeRouteSender(rs *routeSender) {
	network.routeSenderController.removeRouteSender(rs)
}

func (network *Network) GetEventDispatcher() event.Dispatcher {
	return network.eventDispatcher
}

func (network *Network) GetTraceController() trace.Controller {
	return network.traceController
}

func (network *Network) GetMetricsRegistry() metrics.Registry {
	return network.metricsRegistry
}

func (network *Network) GetServiceEventsMetricsRegistry() metrics.UsageRegistry {
	return network.serviceEventMetrics
}

func (network *Network) GetCloseNotify() <-chan struct{} {
	return network.closeNotify
}

func (network *Network) ConnectedRouter(id string) bool {
	return network.Router.IsConnected(id)
}

var (
	// ErrConnectRejected indicates a router connect was rejected because another connection for the same
	// router is already current. It is returned by ConnectRouter and propagated out of the bind handler so
	// NewChannel closes the rejected connection's underlay without starting rx or registering it; the
	// router then redials.
	ErrConnectRejected = errors.New("router connect rejected: another connection is already current")

	// ErrConnectChannelClosed indicates a router connect was refused because its control channel was
	// already closed by the time the connect decision was made, so the connection must not be registered.
	ErrConnectChannelClosed = errors.New("router connect rejected: control channel already closed")
)

// IsConnectRejected reports whether err is (or wraps) a connect refusal that the router recovers from by
// redialing, so the accept path can log it at info rather than treating it as a bind failure.
func IsConnectRejected(err error) bool {
	return errors.Is(err, ErrConnectRejected) || errors.Is(err, ErrConnectChannelClosed)
}

// ConnectRouter registers r as the current connection for its router id, serialized per router. If the
// slot is already held by a different connection it rejects this one (returning ErrConnectRejected) and
// displaces the occupant so its teardown runs; the router redials into the freed slot. A connection whose
// channel is already closed is refused outright (ErrConnectChannelClosed) rather than registered. There is
// at most one connection per router in the connected map at a time.
func (network *Network) ConnectRouter(r *model.Router) error {
	unlock := network.Router.LockConnectFor(r.Id)
	defer unlock() // leak-safety net; idempotent, so the explicit unlocks below are the ones that matter

	if cur := network.Router.GetConnected(r.Id); cur != nil && cur != r {
		// Displace the occupant outside the lock: the teardown acquires the stripe itself (we have
		// released it), so there is no reentrant self-deadlock.
		unlock()
		network.displaceConnection(cur)
		return ErrConnectRejected
	}

	// Its close handler has already run and never fires again, so nothing would remove it from the
	// connected map and every redial would bounce off a slot that can never be freed.
	if r.Control == nil || r.Control.IsClosed() {
		return ErrConnectChannelClosed
	}

	network.Link.BuildRouterLinks(r)
	network.Router.MarkConnected(r)

	for _, h := range network.routerPresenceHandlers.Value() {
		if syncCapableHandler, ok := h.(model.SyncRouterPresenceHandler); ok && syncCapableHandler.InvokeRouterConnectedSynchronously() {
			h.RouterConnected(r)
		} else {
			go h.RouterConnected(r)
		}
	}
	unlock()

	go network.ValidateTerminators(r)
	return nil
}

func (network *Network) ValidateTerminators(r *model.Router) {
	logger := pfxlog.Logger().WithField("routerId", r.Id)
	result, err := network.Terminator.Query(fmt.Sprintf(`router.id = "%v" limit none`, r.Id))
	if err != nil {
		logger.WithError(err).Error("failed to get terminators for router")
		return
	}

	logger.Debugf("%v terminators to validate", len(result.Entities))
	if len(result.Entities) == 0 {
		return
	}

	network.RouterMessaging.ValidateRouterTerminators(result.Entities)
}

type LinkValidationCallback func(detail *mgmt_pb.RouterLinkDetails)

func (n *Network) ValidateLinks(filter string, cb LinkValidationCallback) (int64, func(), error) {
	result, err := n.Router.BaseList(filter)
	if err != nil {
		return 0, nil, err
	}

	sem := concurrenz.NewSemaphore(10)

	evalF := func() {
		for _, router := range result.Entities {
			connectedRouter := n.GetConnectedRouter(router.Id)
			if connectedRouter != nil {
				sem.Acquire()
				go func() {
					defer sem.Release()
					n.ValidateRouterLinks(connectedRouter, cb)
				}()
			} else {
				n.reportRouterLinksError(router, errors.New("router not connected"), cb)
			}
		}
	}

	return int64(len(result.Entities)), evalF, nil
}

type SdkTerminatorValidationCallback func(detail *mgmt_pb.RouterSdkTerminatorsDetails)

func (n *Network) ValidateRouterSdkTerminators(filter string, cb SdkTerminatorValidationCallback) (int64, func(), error) {
	result, err := n.Router.BaseList(filter)
	if err != nil {
		return 0, nil, err
	}

	sem := concurrenz.NewSemaphore(10)

	evalF := func() {
		for _, router := range result.Entities {
			connectedRouter := n.GetConnectedRouter(router.Id)
			if connectedRouter != nil {
				sem.Acquire()
				go func() {
					defer sem.Release()
					n.Router.ValidateRouterSdkTerminators(connectedRouter, cb)
				}()
			} else {
				n.Router.ReportRouterSdkTerminatorsError(router, errors.New("router not connected"), cb)
			}
		}
	}

	return int64(len(result.Entities)), evalF, nil
}

type ErtTerminatorValidationCallback func(detail *mgmt_pb.RouterErtTerminatorsDetails)

func (n *Network) ValidateRouterErtTerminators(filter string, cb ErtTerminatorValidationCallback) (int64, func(), error) {
	result, err := n.Router.BaseList(filter)
	if err != nil {
		return 0, nil, err
	}

	sem := concurrenz.NewSemaphore(10)

	evalF := func() {
		for _, router := range result.Entities {
			connectedRouter := n.GetConnectedRouter(router.Id)
			if connectedRouter != nil {
				sem.Acquire()
				go func() {
					defer sem.Release()
					n.Router.ValidateRouterErtTerminators(connectedRouter, cb)
				}()
			} else {
				n.Router.ReportRouterErtTerminatorsError(router, errors.New("router not connected"), cb)
			}
		}
	}

	return int64(len(result.Entities)), evalF, nil
}

// isCurrentConnection reports whether r is still the router's current, connected connection, by pointer
// identity against the connected map (mirrors the check in NotifyExistingLink). A stale or superseded
// connection returns false.
func (network *Network) isCurrentConnection(r *model.Router) bool {
	return network.Router.GetConnected(r.Id) == r && r.Connected.Load()
}

// displaceConnection removes cur, the connection occupying its router's connected slot, so that a redial
// can take the slot. Closing the channel is not sufficient on its own: if it is already closed, its close
// handler has already run and will never run again, so nothing would remove cur and every subsequent
// connect would be rejected against a slot that can never be freed. The teardown is therefore also
// invoked directly; it is gated on connection currency, so it is a no-op once the close handler has
// cleared the slot. Must be called with the router's connect stripe released, since the teardown
// acquires it.
func (network *Network) displaceConnection(cur *model.Router) {
	if ch := cur.Control; ch != nil && !ch.IsClosed() {
		if err := ch.Close(); err != nil {
			pfxlog.Logger().WithError(err).WithField("routerId", cur.Id).
				Error("error closing superseded control channel while rejecting connect")
		}
	}
	network.DisconnectRouter(cur)
}

func (network *Network) DisconnectRouter(r *model.Router) {
	// Lock-free pre-check: a stale/superseded disconnect (e.g. the old connection after a takeover) has
	// nothing to tear down and must not touch the live connection's state; bail without blocking.
	if !network.isCurrentConnection(r) {
		return
	}

	unlock := network.Router.LockConnectFor(r.Id)
	defer unlock()

	// Re-check under the stripe: a newer connection may have taken over between the pre-check and the
	// lock. The teardown is all-or-nothing and must not run against a superseded connection.
	if !network.isCurrentConnection(r) {
		return
	}

	// Snapshot the router's links before marking it disconnected: MarkDisconnected clears the
	// router's link set (routerLinks.Clear()), so a later r.GetLinks() would return nothing and
	// the link-removal/reroute cascade below would be skipped entirely.
	links := r.GetLinks()

	// Mark the router disconnected before the RerouteLink cascade, so reroute and everything it
	// calls (shortestPath, connected-map reads) sees the dying router as gone. Otherwise reroute
	// runs while the router still appears connected and can compute a replacement path through the
	// very router that is being removed.
	network.Router.MarkDisconnected(r)

	// remove Links for Router, rerouting circuits off any that were connected
	for _, l := range links {
		wasConnected := l.CurrentState().Mode == model.Connected
		if l.Src.Id == r.Id {
			network.Link.Remove(l)
		}
		if wasConnected {
			network.RerouteLink(l)
		}
	}

	for _, h := range network.routerPresenceHandlers.Value() {
		h.RouterDisconnected(r)
	}
}

func (network *Network) NotifyExistingLink(srcRouter *model.Router, reportedLink *ctrl_pb.RouterLinks_RouterLink) {
	log := pfxlog.Logger().
		WithField("routerId", srcRouter.Id).
		WithField("linkId", reportedLink.Id).
		WithField("destRouterId", reportedLink.DestRouterId).
		WithField("iteration", reportedLink.Iteration)

	// Publish under the stripe DisconnectRouter holds: checking currency and then publishing without it
	// lets a report recreate a link after the teardown has snapshotted and cleared it. Events go out after
	// the unlock, since a dispatcher may be slow and this stripe is shared with connect and disconnect.
	unlock := network.Router.LockConnectFor(srcRouter.Id)

	src := network.Router.GetConnected(srcRouter.Id)
	if src == nil {
		unlock()
		log.Info("ignoring links message processed after router disconnected")
		return
	}

	if src != srcRouter || !srcRouter.Connected.Load() {
		unlock()
		log.Info("ignoring links message processed from old router connection")
		return
	}

	dst := network.Router.GetConnected(reportedLink.DestRouterId)
	link, created := network.Link.RouterReportedLink(reportedLink, src, dst)

	unlock()

	if dst == nil {
		network.NotifyLinkIdEvent(reportedLink.Id, event.LinkFromRouterDisconnectedDest)
	}

	if created {
		network.NotifyLinkEvent(link, event.LinkFromRouterNew)
		log.Info("router reported link added")
	} else {
		network.NotifyLinkEvent(link, event.LinkFromRouterKnown)
		log.Info("router reported link already known")
	}
}

func (network *Network) LinkFaulted(link *model.Link, dupe bool) {
	wasUsable := link.IsUsable()

	link.SetState(model.Failed)
	if dupe {
		network.NotifyLinkEvent(link, event.LinkDuplicate)
	} else {
		network.NotifyLinkEvent(link, event.LinkFault)
	}

	pfxlog.Logger().WithField("linkId", link.Id).Info("removing failed link")
	network.Link.Remove(link)

	if wasUsable {
		network.RerouteLink(link)
	}
}

func (network *Network) VerifyRouter(routerId string, fingerprints []string) error {
	router, err := network.GetRouter(routerId)
	if err != nil {
		return err
	}

	routerFingerprint := router.Fingerprint
	if routerFingerprint == nil {
		return fmt.Errorf("invalid router %v, not yet enrolled", routerId)
	}

	for _, fp := range fingerprints {
		if fp == *routerFingerprint {
			return nil
		}
	}

	return fmt.Errorf("could not verify fingerprint for router %v", routerId)
}

func (network *Network) RerouteLink(l *model.Link) {
	// This is called from Channel.rxer() and thus may not block
	go func() {
		network.handleRerouteLink(l)
	}()
}

func (network *Network) CreateCircuit(params model.CreateCircuitParams) (*model.Circuit, error) {
	clientId := params.GetClientId()
	service := params.GetServiceId()
	ctx := params.GetLogContext()
	deadline := params.GetDeadline()

	startTime := time.Now()

	instanceId, serviceId := parseInstanceIdAndService(service)

	// 1: Allocate Circuit Identifier
	circuitId := params.GetCircuitId()
	if circuitId == "" {
		var err error
		circuitId, err = idgen.NewUUIDString()
		if err != nil {
			network.CircuitFailedEvent(circuitId, params, startTime, nil, nil, CircuitFailureIdGenerationError)
			return nil, err
		}
	}
	ctx.WithFields(map[string]interface{}{
		"circuitId":     circuitId,
		"serviceId":     service,
		"attemptNumber": 1,
	})
	logger := pfxlog.ChannelLogger(logcontext.SelectPath).Wire(ctx).Entry

	circuit := &model.Circuit{
		Id:        circuitId,
		ClientId:  clientId.Token,
		ServiceId: serviceId,
		Path:      &model.Path{}, // empty until the circuit is built
	}

	// Reserve the circuit ID in the map to prevent collisions and protect routing.
	// On any error path, the deferred cleanup removes the stub.
	if !network.Circuit.Reserve(circuit) {
		return nil, fmt.Errorf("circuit id %v already in use", circuitId)
	}
	removeReserved := true
	defer func() {
		if removeReserved {
			network.Circuit.Remove(circuit)
		}
	}()

	attempt := uint32(0)
	allCleanups := make(map[string]struct{})
	rs := network.newRouteSender(circuitId)
	defer func() { network.removeRouteSender(rs) }()
	for {
		// 2: Find Service
		svc, err := network.Service.Read(serviceId)
		if err != nil {
			network.CircuitFailedEvent(circuitId, params, startTime, nil, nil, CircuitFailureInvalidService)
			network.ServiceDialOtherError(serviceId)
			return circuit, err
		}
		logger = logger.WithField("serviceName", svc.Name)

		// 3: select terminator
		strategy, terminator, pathNodes, strategyData, circuitErr := network.selectPath(params, svc, instanceId, ctx)
		if circuitErr != nil {
			network.CircuitFailedEvent(circuitId, params, startTime, nil, nil, circuitErr.Cause())
			network.ServiceDialOtherError(serviceId)
			return circuit, circuitErr
		}

		circuit.Terminator = terminator

		// 4: Create Path
		path, pathErr := network.CreatePathWithNodes(pathNodes)
		if pathErr != nil {
			network.CircuitFailedEvent(circuitId, params, startTime, nil, terminator, pathErr.Cause())
			network.ServiceDialOtherError(serviceId)
			return circuit, pathErr
		}

		circuit.Path = path

		// get circuit tags
		tags := params.GetCircuitTags(terminator)

		circuit.Tags = tags

		// 4a: Create Route Messages
		rms := network.CreateRouteMessages(path, attempt, circuitId, terminator, deadline)
		rms[len(rms)-1].Egress.PeerData = clientId.Data
		for _, msg := range rms {
			msg.Context = &ctrl_pb.Context{
				Fields:      ctx.GetStringFields(),
				ChannelMask: ctx.GetChannelsMask(),
			}
			msg.Tags = tags
		}

		// 5: Routing
		logger.Debug("route attempt for circuit")
		peerData, cleanups, circuitErr := rs.route(attempt, path, rms, strategy, terminator, ctx.Clone())
		for k, v := range cleanups {
			allCleanups[k] = v
		}
		if circuitErr != nil {
			logger.WithError(circuitErr).Warn("route attempt for circuit failed")
			network.CircuitFailedEvent(circuitId, params, startTime, path, terminator, circuitErr.Cause())
			attempt++
			ctx.WithField("attemptNumber", attempt)
			logger = logger.WithField("attemptNumber", attempt)
			if attempt < network.options.CreateCircuitRetries {
				continue
			} else {
				// revert successful routes
				logger.Warnf("circuit creation failed after [%d] attempts, sending cleanup unroutes", network.options.CreateCircuitRetries)
				for cleanupRId := range allCleanups {
					if r := network.GetConnectedRouter(cleanupRId); r != nil {
						if err := sendUnroute(r, circuitId, true); err == nil {
							logger.WithField("routerId", cleanupRId).Debug("sent cleanup unroute for circuit")
						} else {
							logger.WithField("routerId", cleanupRId).Error("error sending cleanup unroute for circuit")
						}
					} else {
						logger.WithField("routerId", cleanupRId).Error("router for circuit cleanup not connected")
					}
				}

				return circuit, fmt.Errorf("exceeded maximum [%d] retries creating circuit [c/%s] (%w)", network.options.CreateCircuitRetries, circuitId, circuitErr)
			}
		}

		// 5.a: Unroute Abandoned Routers (from Previous Attempts)
		usedRouters := make(map[string]struct{})
		for _, r := range path.Nodes {
			usedRouters[r.Id] = struct{}{}
		}
		cleanupCount := 0
		for cleanupRId := range allCleanups {
			if _, found := usedRouters[cleanupRId]; !found {
				cleanupCount++
				if r := network.GetConnectedRouter(cleanupRId); r != nil {
					if err := sendUnroute(r, circuitId, true); err == nil {
						logger.WithField("routerId", cleanupRId).Debug("sent abandoned cleanup unroute for circuit to router")
					} else {
						logger.WithField("routerId", cleanupRId).WithError(err).Error("error sending abandoned cleanup unroute for circuit to router")
					}
				} else {
					logger.WithField("routerId", cleanupRId).Error("router not connected for circuit, abandoned cleanup")
				}
			}
		}
		logger.Debugf("cleaned up [%d] abandoned routers for circuit", cleanupCount)

		path.InitiatorLocalAddr = string(clientId.Data[uint32(ctrl_msg.InitiatorLocalAddressHeader)])
		path.InitiatorRemoteAddr = string(clientId.Data[uint32(ctrl_msg.InitiatorRemoteAddressHeader)])
		path.TerminatorLocalAddr = string(peerData[uint32(ctrl_msg.TerminatorLocalAddressHeader)])
		path.TerminatorRemoteAddr = string(peerData[uint32(ctrl_msg.TerminatorRemoteAddressHeader)])

		delete(peerData, uint32(ctrl_msg.InitiatorLocalAddressHeader))
		delete(peerData, uint32(ctrl_msg.InitiatorRemoteAddressHeader))
		delete(peerData, uint32(ctrl_msg.TerminatorLocalAddressHeader))
		delete(peerData, uint32(ctrl_msg.TerminatorRemoteAddressHeader))

		for k, v := range strategyData {
			peerData[k] = v
		}

		now := time.Now()
		// 6: Create Circuit Object
		circuit.PeerData = peerData
		circuit.CreatedAt = now
		circuit.UpdatedAt = now

		removeReserved = false // circuit is finalized, don't remove on defer
		creationTimespan := time.Since(startTime)
		network.CircuitEvent(event.CircuitCreated, circuit, &creationTimespan)
		strategy.NotifyEvent(xt.NewDialSucceeded(terminator))

		logger.WithField("path", circuit.Path).
			WithField("terminator_local_address", circuit.Path.TerminatorLocalAddr).
			WithField("terminator_remote_address", circuit.Path.TerminatorRemoteAddr).
			Debug("created circuit")
		return circuit, nil
	}
}

func (network *Network) ReportForwardingFaults(ffr *ForwardingFaultReport) {
	go network.handleForwardingFaults(ffr)
}

func parseInstanceIdAndService(service string) (string, string) {
	atIndex := strings.IndexRune(service, '@')
	if atIndex < 0 {
		return "", service
	}
	identityId := service[0:atIndex]
	serviceId := service[atIndex+1:]
	return identityId, serviceId
}

func (network *Network) selectPath(params model.CreateCircuitParams, svc *model.Service, instanceId string, ctx logcontext.Context) (xt.Strategy, xt.CostedTerminator, []*model.Router, xt.PeerData, CircuitError) {
	paths := map[string]*PathAndCost{}
	var weightedTerminators []xt.CostedTerminator
	var errList []error

	log := pfxlog.ChannelLogger(logcontext.SelectPath).Wire(ctx)

	hasOfflineRouters := false
	pathError := false

	for _, terminator := range svc.Terminators {
		if terminator.InstanceId != instanceId {
			continue
		}

		pathAndCost, found := paths[terminator.Router]
		if !found {
			dstR := network.Router.GetConnected(terminator.GetRouterId())
			if dstR == nil {
				err := fmt.Errorf("router with id=%v on terminator with id=%v for service name=%v is not online",
					terminator.GetRouterId(), terminator.GetId(), svc.Name)
				log.Debugf("error while calculating path for service %v: %v", svc.Id, err)

				errList = append(errList, err)
				hasOfflineRouters = true
				continue
			}

			path, cost, err := network.shortestPath(params.GetSourceRouter(), dstR)
			if err != nil {
				log.Debugf("error while calculating path for service %v: %v", svc.Id, err)
				errList = append(errList, err)
				pathError = true
				continue
			}

			pathAndCost = newPathAndCost(path, cost)
			paths[terminator.GetRouterId()] = pathAndCost
		}

		dynamicCost := xt.GlobalCosts().GetDynamicCost(terminator.Id)
		unbiasedCost := uint32(terminator.Cost) + uint32(dynamicCost) + pathAndCost.cost
		biasedCost := terminator.Precedence.GetBiasedCost(unbiasedCost)
		costedTerminator := &model.RoutingTerminator{
			Terminator: terminator,
			RouteCost:  biasedCost,
		}
		weightedTerminators = append(weightedTerminators, costedTerminator)
	}

	if len(svc.Terminators) == 0 {
		return nil, nil, nil, nil, newCircuitErrorf(CircuitFailureNoTerminators, "service %v has no terminators", svc.Id)
	}

	if len(weightedTerminators) == 0 {
		if pathError {
			return nil, nil, nil, nil, newCircuitErrWrap(CircuitFailureNoPath, errors.Join(errList...))
		}

		if hasOfflineRouters {
			return nil, nil, nil, nil, newCircuitErrorf(CircuitFailureNoOnlineTerminators, "service %v has no online terminators for instanceId %v", svc.Id, instanceId)
		}

		return nil, nil, nil, nil, newCircuitErrorf(CircuitFailureNoTerminators, "service %v has no terminators for instanceId %v", svc.Id, instanceId)
	}

	strategy, err := network.strategyRegistry.GetStrategy(svc.TerminatorStrategy)
	if err != nil {
		return nil, nil, nil, nil, newCircuitErrWrap(CircuitFailureInvalidStrategy, err)
	}

	sort.Slice(weightedTerminators, func(i, j int) bool {
		return weightedTerminators[i].GetRouteCost() < weightedTerminators[j].GetRouteCost()
	})

	terminator, peerData, err := strategy.Select(params, weightedTerminators)

	if err != nil {
		return nil, nil, nil, nil, newCircuitErrorf(CircuitFailureStrategyError, "strategy %v errored selecting terminator for service %v: %v", svc.TerminatorStrategy, svc.Id, err)
	}

	if terminator == nil {
		return nil, nil, nil, nil, newCircuitErrorf(CircuitFailureStrategyError, "strategy %v did not select terminator for service %v", svc.TerminatorStrategy, svc.Id)
	}

	path := paths[terminator.GetRouterId()].path

	if log.Logger.IsLevelEnabled(logrus.DebugLevel) {
		buf := strings.Builder{}
		buf.WriteString("[")
		if len(weightedTerminators) > 0 {
			fmt.Fprintf(&buf, "%v: %v", weightedTerminators[0].GetId(), weightedTerminators[0].GetRouteCost())
			for _, t := range weightedTerminators[1:] {
				buf.WriteString(", ")
				fmt.Fprintf(&buf, "%v: %v", t.GetId(), t.GetRouteCost())
			}
		}
		buf.WriteString("]")
		var routerIds []string
		for _, r := range path {
			routerIds = append(routerIds, fmt.Sprintf("r/%s", r.Id))
		}
		pathStr := strings.Join(routerIds, "->")
		log.Debugf("selected terminator %v for path %v from %v", terminator.GetId(), pathStr, buf.String())
	}

	return strategy, terminator, path, peerData, nil
}

func (network *Network) RemoveCircuit(circuitId string, now bool) error {
	log := pfxlog.Logger().WithField("circuitId", circuitId)

	if circuit, found := network.Circuit.Get(circuitId); found {
		for _, r := range circuit.Path.Nodes {
			err := sendUnroute(r, circuit.Id, now)
			if err != nil {
				log.Errorf("error sending unroute to [r/%s] (%s)", r.Id, err)
			}
		}

		network.Circuit.Remove(circuit)
		network.CircuitEvent(event.CircuitDeleted, circuit, nil)

		if svc, err := network.Service.Read(circuit.ServiceId); err == nil {
			if strategy, err := network.strategyRegistry.GetStrategy(svc.TerminatorStrategy); strategy != nil {
				strategy.NotifyEvent(xt.NewCircuitRemoved(circuit.Terminator))
			} else if err != nil {
				log.WithError(err).WithField("terminatorStrategy", svc.TerminatorStrategy).Warn("failed to notify strategy of circuit end, invalid strategy")
			}
		} else {
			log.WithError(err).Error("unable to get service for circuit")
		}

		log.Debug("removed circuit")

		return nil
	}
	return InvalidCircuitError{circuitId: circuitId}
}

func (network *Network) CreatePath(srcR, dstR *model.Router) (*model.Path, error) {
	ingressId, err := idgen.NewUUIDString()
	if err != nil {
		return nil, err
	}

	egressId, err := idgen.NewUUIDString()
	if err != nil {
		return nil, err
	}

	path := &model.Path{
		Links:     make([]*model.Link, 0),
		IngressId: ingressId,
		EgressId:  egressId,
		Nodes:     make([]*model.Router, 0),
	}
	path.Nodes = append(path.Nodes, srcR)
	path.Nodes = append(path.Nodes, dstR)

	return network.UpdatePath(path)
}

func (network *Network) setLinks(path *model.Path) error {
	if len(path.Nodes) > 1 {
		for i := 0; i < len(path.Nodes)-1; i++ {
			if link, found := network.Link.LeastExpensiveLink(path.Nodes[i], path.Nodes[i+1]); found {
				path.Links = append(path.Links, link)
			} else {
				return fmt.Errorf("no link from r/%v to r/%v", path.Nodes[i].Id, path.Nodes[i+1].Id)
			}
		}
	}
	return nil
}

func (network *Network) AddRouterPresenceHandler(h model.RouterPresenceHandler) {
	network.routerPresenceHandlers.Append(h)
}

func (network *Network) Run() {
	defer logrus.Info("exited")
	logrus.Info("started")

	go network.watchdog()

	ticker := time.NewTicker(time.Duration(network.options.CycleSeconds) * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			network.clean()
			network.smart()
			network.Link.ScanForDeadLinks()

		case <-network.closeNotify:
			network.eventDispatcher.RemoveMetricsMessageHandler(network)
			network.metricsRegistry.DisposeAll()
			return
		}

		// notify the watchdog that we're processing
		select {
		case network.watchdogCh <- struct{}{}:
		default:
		}
	}
}

func (network *Network) watchdog() {
	watchdogInterval := 2 * time.Duration(network.options.CycleSeconds) * time.Second
	consecutiveFails := 0

	watchDogTicker := time.NewTicker(watchdogInterval)
	defer watchDogTicker.Stop()

	for {
		// check every 2x cycle seconds
		select {
		case <-watchDogTicker.C:
		case <-network.closeNotify:
			return
		}

		select {
		case <-network.watchdogCh:
			consecutiveFails = 0
			continue
		case <-network.closeNotify:
			return
		default:
			consecutiveFails++
			// network.Run didn't complete, something is stalling it
			pfxlog.Logger().
				WithField("watchdogInterval", watchdogInterval.String()).
				WithField("consecutiveFails", consecutiveFails).
				Warn("network.Run did not finish within watchdog interval")

			if consecutiveFails == 3 {
				debugz.DumpStack()
			}
		}
	}
}

func (network *Network) handleRerouteLink(l *model.Link) {
	log := logrus.WithField("linkId", l.Id)
	log.Info("changed link")
	if err := network.rerouteLink(l, time.Now().Add(config.DefaultOptionsRouteTimeout)); err != nil {
		log.WithError(err).Error("unexpected error rerouting link")
	}
}

func (network *Network) handleForwardingFaults(ffr *ForwardingFaultReport) {
	network.fault(ffr)
}

func (network *Network) AddCapability(capability string) {
	network.lock.Lock()
	defer network.lock.Unlock()
	network.capabilities = append(network.capabilities, capability)
}

func (network *Network) GetCapabilities() []string {
	network.lock.Lock()
	defer network.lock.Unlock()
	return network.capabilities
}

func (network *Network) RemoveLink(linkId string) {
	log := pfxlog.Logger().WithField("linkId", linkId)

	link, _ := network.Link.Get(linkId)
	var iteration uint32

	var routerList []*model.Router
	if link != nil {
		iteration = link.Iteration
		routerList = []*model.Router{link.Src}
		if dst := link.GetDest(); dst != nil {
			routerList = append(routerList, dst)
		}
		log = log.WithField("srcRouterId", link.Src.Id).
			WithField("dstRouterId", link.DstId).
			WithField("iteration", iteration)
		log.Info("deleting known link")
	} else {
		routerList = network.AllConnectedRouters()
		log.Info("deleting unknown link (sending link fault to all connected routers)")
	}

	for _, router := range routerList {
		fault := &ctrl_pb.Fault{
			Subject:   ctrl_pb.FaultSubject_LinkFault,
			Id:        linkId,
			Iteration: iteration,
		}

		if ctrl := router.Control; ctrl != nil {
			if err := protobufs.MarshalTyped(fault).WithTimeout(15 * time.Second).Send(ctrl.GetDefaultSender()); err != nil {
				log.WithField("faultDestRouterId", router.Id).WithError(err).
					Error("failed to send link fault to router on link removal")
			} else {
				log.WithField("faultDestRouterId", router.Id).WithError(err).
					Info("sent link fault to router on link removal")
			}
		}
	}

	if link != nil {
		network.Link.Remove(link)
		network.RerouteLink(link)
	}
}

func (network *Network) rerouteLink(l *model.Link, deadline time.Time) error {
	circuits := network.Circuit.All()
	for _, circuit := range circuits {
		if circuit.Path.UsesLink(l) {
			log := logrus.WithField("linkId", l.Id).
				WithField("circuitId", circuit.Id)
			log.Info("circuit uses link")
			if err := network.rerouteCircuit(circuit, deadline); err != nil {
				log.WithError(err).Error("error rerouting circuit, removing")
				if err := network.RemoveCircuit(circuit.Id, true); err != nil {
					log.WithError(err).Error("error removing circuit after reroute failure")
				}
			}
		}
	}

	return nil
}

func (network *Network) rerouteCircuitWithTries(circuit *model.Circuit, retries int) bool {
	log := pfxlog.Logger().WithField("circuitId", circuit.Id)

	// Path is nil for reserved circuits that haven't been built yet
	if circuit.Path.IsValid() {
		for i := 0; i < retries; i++ {
			deadline := time.Now().Add(config.DefaultOptionsRouteTimeout)
			err := network.rerouteCircuit(circuit, deadline)
			if err == nil {
				return true
			}

			log.WithError(err).WithField("attempt", i).Error("error re-routing circuit")
		}
	}

	if err := network.RemoveCircuit(circuit.Id, true); err != nil {
		log.WithError(err).Error("failure while removing circuit after failed re-route attempt")
	}
	return false
}

func (network *Network) rerouteCircuit(circuit *model.Circuit, deadline time.Time) error {
	log := pfxlog.Logger().WithField("circuitId", circuit.Id)
	if circuit.Rerouting.CompareAndSwap(false, true) {
		defer circuit.Rerouting.Store(false)

		log.Warn("rerouting circuit")

		oldPath := circuit.Path
		if cq, err := network.UpdatePath(circuit.Path); err == nil {
			circuit.Path = cq
			circuit.UpdatedAt = time.Now()

			rms := network.CreateRouteMessages(cq, SmartRerouteAttempt, circuit.Id, circuit.Terminator, deadline)

			for i := 0; i < len(cq.Nodes); i++ {
				if _, err := sendRoute(cq.Nodes[i], rms[i], network.options.RouteTimeout); err != nil {
					log.WithError(err).Errorf("error sending route to [r/%s]", cq.Nodes[i].Id)
					return err
				}
			}

			network.unrouteRemovedPathNodes(log, circuit.Id, oldPath, cq)

			log.Info("rerouted circuit")

			network.CircuitEvent(event.CircuitUpdated, circuit, nil)
			return nil
		} else {
			return err
		}
	} else {
		log.Info("not rerouting circuit, already in progress")
		return nil
	}
}

func (network *Network) smartReroute(circuit *model.Circuit, cq *model.Path, deadline time.Time) bool {
	retry := false
	log := pfxlog.Logger().WithField("circuitId", circuit.Id)
	if circuit.Rerouting.CompareAndSwap(false, true) {
		defer circuit.Rerouting.Store(false)

		oldPath := circuit.Path
		circuit.Path = cq
		circuit.UpdatedAt = time.Now()

		rms := network.CreateRouteMessages(cq, SmartRerouteAttempt, circuit.Id, circuit.Terminator, deadline)

		for i := 0; i < len(cq.Nodes); i++ {
			if _, err := sendRoute(cq.Nodes[i], rms[i], network.options.RouteTimeout); err != nil {
				retry = true
				log.WithField("routerId", cq.Nodes[i].Id).WithError(err).Error("error sending smart route update to router")
				break
			}
		}

		if !retry {
			network.unrouteRemovedPathNodes(log, circuit.Id, oldPath, cq)
			logrus.Debug("rerouted circuit")
			network.CircuitEvent(event.CircuitUpdated, circuit, nil)
		}
	}
	return retry
}

func (network *Network) AcceptMetricsMsg(metrics *metrics_pb.MetricsMessage) {
	if metrics.SourceId == network.nodeId {
		return // ignore metrics coming from the controller itself
	}

	log := pfxlog.Logger()

	router, err := network.Router.Read(metrics.SourceId)
	if err != nil {
		log.Debugf("could not find router [r/%s] while processing metrics", metrics.SourceId)
		return
	}

	for _, link := range network.GetAllLinksForRouter(router.Id) {
		metricId := "link." + link.Id + ".latency"
		var latencyCost int64
		var found bool
		if latency, ok := metrics.Histograms[metricId]; ok {
			latencyCost = int64(latency.Mean)
			found = true

			metricId = "link." + link.Id + ".queue_time"
			if queueTime, ok := metrics.Histograms[metricId]; ok {
				latencyCost += int64(queueTime.Mean)
			}
		}

		if found {
			if link.Src.Id == router.Id {
				link.SetSrcLatency(latencyCost) // latency is in nanoseconds
			} else if link.DstId == router.Id {
				link.SetDstLatency(latencyCost) // latency is in nanoseconds
			} else {
				log.Warnf("link not for router")
			}
		}
	}
}

func sendRoute(r *model.Router, createMsg *ctrl_pb.Route, timeout time.Duration) (xt.PeerData, error) {
	log := pfxlog.Logger().WithField("routerId", r.Id).
		WithField("circuitId", createMsg.CircuitId)

	log.Debug("sending create route message")

	msg, err := protobufs.MarshalTyped(createMsg).WithTimeout(timeout).SendForReply(r.Control.GetHighPrioritySender())
	if err != nil {
		log.WithError(err).WithField("timeout", timeout).Error("error sending route message")
		return nil, err
	}

	if msg.ContentType == ctrl_msg.RouteResultType {
		_, success := msg.Headers[ctrl_msg.RouteResultSuccessHeader]
		if !success {
			message := "route error, but no error message from router"
			if errMsg, found := msg.Headers[ctrl_msg.RouteResultErrorHeader]; found {
				message = string(errMsg)
			}
			return nil, errors.New(message)
		}

		peerData := xt.PeerData{}
		for k, v := range msg.Headers {
			if k > 0 {
				peerData[uint32(k)] = v
			}
		}

		return peerData, nil
	}
	return nil, fmt.Errorf("unexpected response type %v received in reply to route request", msg.ContentType)
}

func sendUnroute(r *model.Router, circuitId string, now bool) error {
	unroute := &ctrl_pb.Unroute{
		CircuitId: circuitId,
		Now:       now,
	}
	return protobufs.MarshalTyped(unroute).Send(r.Control.GetHighPrioritySender())
}

// unrouteRemovedPathNodes sends Unroute to any nodes that were in the old path but are not in the new path.
// This handles the case where a circuit reroute changes intermediate transit nodes.
func (network *Network) unrouteRemovedPathNodes(log *logrus.Entry, circuitId string, oldPath, newPath *model.Path) {
	newNodeIds := make(map[string]struct{}, len(newPath.Nodes))
	for _, r := range newPath.Nodes {
		newNodeIds[r.Id] = struct{}{}
	}

	for _, r := range oldPath.Nodes {
		if _, ok := newNodeIds[r.Id]; !ok {
			if cr := network.GetConnectedRouter(r.Id); cr != nil {
				if err := sendUnroute(cr, circuitId, true); err != nil {
					log.WithError(err).Errorf("error sending unroute to removed path node [r/%s]", r.Id)
				}
			}
		}
	}
}

func (network *Network) showOptions() {
	if jsonOptions, err := json.MarshalIndent(network.options, "", "  "); err == nil {
		pfxlog.Logger().Infof("network = %s", string(jsonOptions))
	} else {
		panic(err)
	}
}

type renderConfig interface {
	RenderJsonConfig() (string, error)
}

func (network *Network) routerDeleted(routerId string) {
	circuits := network.GetAllCircuits()
	for _, circuit := range circuits {
		if circuit.HasRouter(routerId) {
			path := circuit.Path

			// If we're either the initiator, terminator (or both), cleanup the circuit since
			// we won't be able to re-establish it, and we'll never get a circuit fault
			if path.Nodes[0].Id == routerId || path.Nodes[len(path.Nodes)-1].Id == routerId {
				if err := network.RemoveCircuit(circuit.Id, true); err != nil {
					pfxlog.Logger().WithField("routerId", routerId).
						WithField("circuitId", circuit.Id).
						WithError(err).Error("unable to remove circuit after router was deleted")
				}
			}
		}
	}
}

var DbSnapshotTooFrequentError = dbSnapshotTooFrequentError{}

type dbSnapshotTooFrequentError struct{}

func (d dbSnapshotTooFrequentError) Error() string {
	return "may snapshot database at most once per minute"
}

func (network *Network) SnapshotDatabase() error {
	_, err := network.SnapshotDatabaseToFile("")
	return err
}

func (network *Network) SnapshotDatabaseToFile(path string) (string, error) {
	network.lock.Lock()
	defer network.lock.Unlock()

	if network.lastSnapshot.Add(time.Minute).After(time.Now()) {
		return "", DbSnapshotTooFrequentError
	}

	actualPath := path
	if actualPath == "" {
		actualPath = "__DB_DIR__/__DB_FILE__-__DATE__-__TIME__"
	}

	err := network.GetDb().View(func(tx *bbolt.Tx) error {
		currentIndex := db.LoadCurrentRaftIndex(tx)
		actualPath = strings.ReplaceAll(actualPath, "__RAFT_INDEX__", fmt.Sprintf("%v", currentIndex))
		actualPath = strings.ReplaceAll(actualPath, "RAFT_INDEX", fmt.Sprintf("%v", currentIndex))

		var err error
		actualPath, _, err = network.GetDb().SnapshotInTx(tx, actualPath)
		return err
	})

	if err == nil {
		network.lastSnapshot = time.Now()
	}

	return actualPath, err
}

func (network *Network) RestoreSnapshot(cmd *command.SyncSnapshotCommand, index uint64) error {
	log := pfxlog.Logger()
	currentTimelineId, err := network.GetDb().GetTimelineId(boltz.TimelineModeDefault, shortid.Generate)
	if err != nil {
		log.WithError(err).Error("unable to get current timeline id")
	}
	if currentTimelineId != "" && currentTimelineId == cmd.TimelineId {
		log.WithField("timelineId", cmd.TimelineId).Info("snapshot already current, skipping reload")
		// DB already restored; ensure cluster id then raft index (index last, see main path).
		if err = network.ensureClusterId(cmd.ClusterId); err != nil {
			return fmt.Errorf("failed to set cluster id for already-current snapshot (%w)", err)
		}
		if err = network.ensureRaftIndex(index); err != nil {
			return fmt.Errorf("failed to set raft index for already-current snapshot (%w)", err)
		}
		return nil
	}

	buf := bytes.NewBuffer(cmd.Snapshot)
	reader, err := gzip.NewReader(buf)
	if err != nil {
		return fmt.Errorf("unable to create gz reader for reading migration snapshot during restore (%w)", err)
	}

	network.GetDb().RestoreFromReader(reader)

	// Write the cluster id before the raft index. The index is the completion gate on restart (the
	// FSM skips entries at or below the stored index), so persist it last: any earlier failure then
	// replays and retries instead of skipping the command with a blank cluster id.
	if err = network.ensureClusterId(cmd.ClusterId); err != nil {
		return fmt.Errorf("failed to set cluster id after db restore (%w)", err)
	}
	if err = network.ensureRaftIndex(index); err != nil {
		return fmt.Errorf("failed to set raft index after db restore (%w)", err)
	}

	time.AfterFunc(5*time.Second, func() {
		log.Info("database restore requires controller restart. exiting...")
		os.Exit(0)
	})

	return nil
}

// ensureClusterId writes the cluster id if one is not already set (no-op when empty or matching).
// The snapshot restore replaces the whole db, which carries no cluster id, so it must be set here.
func (network *Network) ensureClusterId(clusterId string) error {
	if clusterId == "" {
		return nil
	}
	_, err := db.InitClusterId(network.GetDb(), nil, clusterId)
	return err
}

// ensureRaftIndex records the raft index if the stored one is behind it, returning an error on
// failure so a missed index update surfaces rather than being treated as success.
func (network *Network) ensureRaftIndex(index uint64) error {
	return network.GetDb().Update(nil, func(ctx boltz.MutateContext) error {
		if db.LoadCurrentRaftIndex(ctx.Tx()) >= index {
			return nil
		}
		raftBucket := boltz.GetOrCreatePath(ctx.Tx(), db.RootBucket, db.MetadataBucket)
		raftBucket.SetInt64(db.FieldRaftIndex, int64(index), nil)
		return raftBucket.GetError()
	})
}

func (network *Network) AddInspectTarget(target InspectTarget) {
	network.inspectionTargets.Append(target)
}

// SetCtrlDialerValidator registers the ctrl dialer's validation function with the network.
func (network *Network) SetCtrlDialerValidator(validator CtrlDialerValidator) {
	network.ctrlDialerValidator = validator
}

// GetCtrlDialerValidator returns the registered ctrl dialer validation function, or nil.
func (network *Network) GetCtrlDialerValidator() CtrlDialerValidator {
	return network.ctrlDialerValidator
}

func (network *Network) ValidateRouterLinks(router *model.Router, cb LinkValidationCallback) {
	request := &ctrl_pb.InspectRequest{RequestedValues: []string{"links"}}
	resp := &ctrl_pb.InspectResponse{}
	respMsg, err := protobufs.MarshalTyped(request).WithTimeout(time.Minute).SendForReply(router.Control.GetDefaultSender())
	if err = protobufs.TypedResponse(resp).Unmarshall(respMsg, err); err != nil {
		network.reportRouterLinksError(router, err, cb)
		return
	}

	var linkDetails *inspect.LinksInspectResult
	for _, val := range resp.Values {
		if val.Name == "links" {
			if err = json.Unmarshal([]byte(val.Value), &linkDetails); err != nil {
				network.reportRouterLinksError(router, err, cb)
				return
			}
		}
	}

	if linkDetails == nil {
		if len(resp.Errors) > 0 {
			err = errors.New(strings.Join(resp.Errors, ","))
			network.reportRouterLinksError(router, err, cb)
			return
		}
		network.reportRouterLinksError(router, errors.New("no link details returned from router"), cb)
		return
	}

	linkMap := network.Link.GetLinkMap()

	result := &mgmt_pb.RouterLinkDetails{
		RouterId:        router.Id,
		RouterName:      router.Name,
		ValidateSuccess: true,
	}

	for _, link := range linkDetails.Links {
		detail := &mgmt_pb.RouterLinkDetail{
			LinkId:       link.Id,
			RouterState:  mgmt_pb.LinkState_LinkEstablished,
			DestRouterId: link.Dest,
			Dialed:       link.Dialed,
		}
		detail.DestConnected = network.ConnectedRouter(link.Dest)
		if ctrlLink, found := linkMap[link.Id]; found {
			detail.CtrlState = mgmt_pb.LinkState_LinkEstablished
			detail.IsValid = detail.DestConnected
			if link.Dialed { // only compare against dialer side of the link, as src/dst will be flipped on the listener side
				network.checkLinkConns(ctrlLink, link, detail)
			}
		} else {
			detail.CtrlState = mgmt_pb.LinkState_LinkUnknown
			detail.IsValid = !detail.DestConnected
		}
		delete(linkMap, link.Id)
		result.LinkDetails = append(result.LinkDetails, detail)
	}

	for _, link := range linkMap {
		related := false
		dest := ""
		if link.Src.Id == router.Id {
			related = true
			dest = link.DstId
		} else if link.DstId == router.Id {
			related = true
			dest = link.Src.Id
		}

		if related {
			detail := &mgmt_pb.RouterLinkDetail{
				LinkId:        link.Id,
				CtrlState:     mgmt_pb.LinkState_LinkEstablished,
				DestConnected: network.ConnectedRouter(dest),
				RouterState:   mgmt_pb.LinkState_LinkUnknown,
				IsValid:       false,
				DestRouterId:  dest,
				Dialed:        link.Src.Id == router.Id,
			}
			result.LinkDetails = append(result.LinkDetails, detail)
		}
	}

	cb(result)
}

func (network *Network) checkLinkConns(ctrlLink *model.Link, routerLink *inspect.LinkInspectDetail, result *mgmt_pb.RouterLinkDetail) {
	sortF := func(v []*ctrl_pb.LinkConn) []*ctrl_pb.LinkConn {
		return slices.SortedFunc(slices.Values(v), func(e *ctrl_pb.LinkConn, e2 *ctrl_pb.LinkConn) int {
			if diff := strings.Compare(e.Type, e2.Type); diff != 0 {
				return diff
			}
			if diff := strings.Compare(e.LocalAddr, e2.LocalAddr); diff != 0 {
				return diff
			}
			return strings.Compare(e.RemoteAddr, e2.RemoteAddr)
		})
	}

	var routerConns []*ctrl_pb.LinkConn

	for _, v := range routerLink.Connections {
		routerConns = append(routerConns, &ctrl_pb.LinkConn{
			Type:       v.Type,
			LocalAddr:  v.Source,
			RemoteAddr: v.Dest,
		})
	}

	// The version comes from the hello, so only the connected instance has it. Not knowing it means the
	// comparison cannot be made, which is not a fault of the link.
	if srcR := ctrlLink.Src; srcR != nil {
		connectedSrc := network.Router.GetConnected(srcR.Id)
		if connectedSrc == nil || connectedSrc.VersionInfo == nil {
			return
		}
		hasMinVersion, err := connectedSrc.VersionInfo.HasMinimumVersion("v1.6.6")
		if err != nil {
			result.IsValid = false
			result.Messages = append(result.Messages, err.Error())
			return
		}
		if !hasMinVersion {
			return
		}
	}

	ctrlConnState := ctrlLink.GetConnsState()
	ctrlConns := sortF(ctrlConnState.GetConns())
	routerConns = sortF(routerConns)

	if len(ctrlConns) != len(routerConns) {
		result.Messages = append(result.Messages, fmt.Sprintf("for link %s, len(ctrlConns): %d != len(routerConns): %d",
			ctrlLink.Id, len(ctrlConns), len(ctrlConns)))
		return
	}

	if routerLink.ConnStateIteration != ctrlConnState.GetStateIteration() {
		result.Messages = append(result.Messages, fmt.Sprintf("for link %s, conn state iteration doesn't match, ctrl: %d != router: %d",
			ctrlLink.Id, ctrlConnState.GetStateIteration(), routerLink.ConnStateIteration))
		return
	}

	for i := 0; i < len(ctrlConns); i++ {
		ctrlConn := ctrlConns[i]
		routerConn := routerConns[i]
		if ctrlConn.Type != routerConn.Type {
			result.IsValid = false
			result.Messages = append(result.Messages, fmt.Sprintf("for link %s, type doesn't match. ctrl %s != router %s",
				ctrlLink.Id, ctrlConn.Type, routerConn.Type))
		}
		if ctrlConn.LocalAddr != routerConn.LocalAddr {
			result.IsValid = false
			result.Messages = append(result.Messages, fmt.Sprintf("for link %s, local addr doesn't match. ctrl %s != router %s",
				ctrlLink.Id, ctrlConn.LocalAddr, routerConn.LocalAddr))
		}
		if ctrlConn.RemoteAddr != routerConn.RemoteAddr {
			result.IsValid = false
			result.Messages = append(result.Messages, fmt.Sprintf("for link %s, remote addr doesn't match. ctrl %s != router %s",
				ctrlLink.Id, ctrlConn.RemoteAddr, routerConn.RemoteAddr))
		}
	}
}

func (network *Network) reportRouterLinksError(router *model.Router, err error, cb LinkValidationCallback) {
	result := &mgmt_pb.RouterLinkDetails{
		RouterId:        router.Id,
		RouterName:      router.Name,
		ValidateSuccess: false,
		Message:         err.Error(),
	}
	cb(result)
}

func minCost(q map[*model.Router]bool, dist map[*model.Router]int64) *model.Router {
	if len(dist) < 1 {
		return nil
	}

	currentMin := int64(math.MaxInt64)
	var selected *model.Router
	for r := range q {
		d := dist[r]
		if d <= currentMin {
			selected = r
			currentMin = d
		}
	}
	return selected
}

type Cache interface {
	RemoveFromCache(id string)
}

func newPathAndCost(path []*model.Router, cost int64) *PathAndCost {
	if cost > (1 << 20) {
		cost = 1 << 20
	}
	return &PathAndCost{
		path: path,
		cost: uint32(cost),
	}
}

type PathAndCost struct {
	path []*model.Router
	cost uint32
}

type InvalidCircuitError struct {
	circuitId string
}

func (err InvalidCircuitError) Error() string {
	return fmt.Sprintf("invalid circuit (%s)", err.circuitId)
}