Remove variables and leftovers of pregenerated ACL content

Prior to the code reorg, we would generate rules from the Policy and
store it on the global object. Now we generate it on the fly for each node
and this commit cleans up the old variables to make sure we have no
unexpected side effects.

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

hscontrol/app.go

@@ -87,8 +87,6 @@ type Headscale struct {
 	DERPServer *DERPServer
 
 	ACLPolicy *policy.ACLPolicy
-	aclRules  []tailcfg.FilterRule
-	sshPolicy *tailcfg.SSHPolicy
 
 	lastStateChange *xsync.MapOf[string, time.Time]
 
@@ -102,12 +100,6 @@ type Headscale struct {
 
 	stateUpdateChan       chan struct{}
 	cancelStateUpdateChan chan struct{}
-
-	// TODO(kradalby): Temporary measure to make sure we can update policy
-	// across modules, will be removed when aclRules are no longer stored
-	// globally but generated per node basis.
-	policyUpdateChan       chan struct{}
-	cancelPolicyUpdateChan chan struct{}
 }
 
 func NewHeadscale(cfg *Config) (*Headscale, error) {
@@ -168,20 +160,15 @@ func NewHeadscale(cfg *Config) (*Headscale, error) {
 		dbString:           dbString,
 		privateKey2019:     privateKey,
 		noisePrivateKey:    noisePrivateKey,
-		aclRules:           tailcfg.FilterAllowAll, // default allowall
 		registrationCache:  registrationCache,
 		pollNetMapStreamWG: sync.WaitGroup{},
 		lastStateChange:    xsync.NewMapOf[time.Time](),
 
 		stateUpdateChan:       make(chan struct{}),
 		cancelStateUpdateChan: make(chan struct{}),
-
-		policyUpdateChan:       make(chan struct{}),
-		cancelPolicyUpdateChan: make(chan struct{}),
 	}
 
 	go app.watchStateChannel()
-	go app.watchPolicyChannel()
 
 	database, err := db.NewHeadscaleDatabase(
 		cfg.DBtype,
@@ -189,7 +176,6 @@ func NewHeadscale(cfg *Config) (*Headscale, error) {
 		cfg.OIDC.StripEmaildomain,
 		app.dbDebug,
 		app.stateUpdateChan,
-		app.policyUpdateChan,
 		cfg.IPPrefixes,
 		cfg.BaseDomain)
 	if err != nil {
@@ -750,10 +736,6 @@ func (h *Headscale) Serve() error {
 				close(h.stateUpdateChan)
 				close(h.cancelStateUpdateChan)
 
-				<-h.cancelPolicyUpdateChan
-				close(h.policyUpdateChan)
-				close(h.cancelPolicyUpdateChan)
-
 				// Close db connections
 				err = h.db.Close()
 				if err != nil {
@@ -862,30 +844,6 @@ func (h *Headscale) watchStateChannel() {
 	}
 }
 
-// TODO(kradalby): baby steps, make this more robust.
-func (h *Headscale) watchPolicyChannel() {
-	for {
-		select {
-		case <-h.policyUpdateChan:
-			machines, err := h.db.ListMachines()
-			if err != nil {
-				log.Error().Err(err).Msg("failed to fetch machines during policy update")
-			}
-
-			rules, sshPolicy, err := policy.GenerateFilterRules(h.ACLPolicy, machines, h.cfg.OIDC.StripEmaildomain)
-			if err != nil {
-				log.Error().Err(err).Msg("failed to update ACL rules")
-			}
-
-			h.aclRules = rules
-			h.sshPolicy = sshPolicy
-
-		case <-h.cancelPolicyUpdateChan:
-			return
-		}
-	}
-}
-
 func (h *Headscale) setLastStateChangeToNow() {
 	var err error
 

hscontrol/db/db.go

@@ -38,7 +38,6 @@ type KV struct {
 type HSDatabase struct {
 	db              *gorm.DB
 	notifyStateChan chan<- struct{}
-	notifyPolicyChan chan<- struct{}
 
 	ipAllocationMutex sync.Mutex
 
@@ -53,7 +52,6 @@ func NewHeadscaleDatabase(
 	dbType, connectionAddr string,
 	stripEmailDomain, debug bool,
 	notifyStateChan chan<- struct{},
-	notifyPolicyChan chan<- struct{},
 	ipPrefixes []netip.Prefix,
 	baseDomain string,
 ) (*HSDatabase, error) {
@@ -65,7 +63,6 @@ func NewHeadscaleDatabase(
 	db := HSDatabase{
 		db:              dbConn,
 		notifyStateChan: notifyStateChan,
-		notifyPolicyChan: notifyPolicyChan,
 
 		ipPrefixes:       ipPrefixes,
 		baseDomain:       baseDomain,

hscontrol/db/machine.go

@@ -33,7 +33,7 @@ var (
 	)
 )
 
-// ListPeers returns all peers of machine, regardless of any Policy.
+// ListPeers returns all peers of machine, regardless of any Policy or if the node is expired.
 func (hsdb *HSDatabase) ListPeers(machine *types.Machine) (types.Machines, error) {
 	log.Trace().
 		Caller().
@@ -218,7 +218,6 @@ func (hsdb *HSDatabase) SetTags(
 	}
 	machine.ForcedTags = newTags
 
-	hsdb.notifyPolicyChan <- struct{}{}
 	hsdb.notifyStateChange()
 
 	if err := hsdb.db.Save(machine).Error; err != nil {

hscontrol/db/machine_test.go

@@ -459,7 +459,7 @@ func (s *Suite) TestSetTags(c *check.C) {
 		types.StringList([]string{"tag:bar", "tag:test", "tag:unknown"}),
 	)
 
-	c.Assert(channelUpdates, check.Equals, int32(4))
+	c.Assert(channelUpdates, check.Equals, int32(2))
 }
 
 func TestHeadscale_generateGivenName(t *testing.T) {

hscontrol/db/suite_test.go

@@ -62,7 +62,6 @@ func (s *Suite) ResetDB(c *check.C) {
 		false,
 		false,
 		sink,
-		sink,
 		[]netip.Prefix{
 			netip.MustParsePrefix("10.27.0.0/23"),
 		},

hscontrol/mapper/mapper.go

@@ -16,6 +16,7 @@ import (
 	"github.com/juanfont/headscale/hscontrol/util"
 	"github.com/klauspost/compress/zstd"
 	"github.com/rs/zerolog/log"
+	"github.com/samber/lo"
 	"tailscale.com/smallzstd"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/dnstype"
@@ -69,33 +70,18 @@ func NewMapper(
 	}
 }
 
-func (m *Mapper) tempWrap(
+// TODO: Optimise
-	machine *types.Machine,
+// As this work continues, the idea is that there will be one Mapper instance
-	pol *policy.ACLPolicy,
+// per node, attached to the open stream between the control and client.
-) (*tailcfg.MapResponse, error) {
+// This means that this can hold a state per machine and we can use that to
-	peers, err := m.db.ListPeers(machine)
+// improve the mapresponses sent.
-	if err != nil {
+// We could:
-		log.Error().
+// - Keep information about the previous mapresponse so we can send a diff
-			Caller().
+// - Store hashes
-			Err(err).
+// - Create a "minifier" that removes info not needed for the node
-			Msg("Cannot fetch peers")
-
-		return nil, err
-	}
-
-	return fullMapResponse(
-		pol,
-		machine,
-		peers,
-		m.stripEmailDomain,
-		m.baseDomain,
-		m.dnsCfg,
-		m.derpMap,
-		m.logtail,
-		m.randomClientPort,
-	)
-}
 
+// fullMapResponse is the internal function for generating a MapResponse
+// for a machine.
 func fullMapResponse(
 	pol *policy.ACLPolicy,
 	machine *types.Machine,
@@ -113,11 +99,23 @@ func fullMapResponse(
 		return nil, err
 	}
 
-	rules, sshPolicy, err := policy.GenerateFilterRules(pol, peers, stripEmailDomain)
+	rules, sshPolicy, err := policy.GenerateFilterRules(
+		pol,
+		// The policy is currently calculated for the entire Headscale network
+		append(peers, *machine),
+		stripEmailDomain,
+	)
 	if err != nil {
 		return nil, err
 	}
 
+	// Filter out peers that have expired.
+	peers = lo.Filter(peers, func(item types.Machine, index int) bool {
+		return !item.IsExpired()
+	})
+
+	// If there are filter rules present, see if there are any machines that cannot
+	// access eachother at all and remove them from the peers.
 	if len(rules) > 0 {
 		peers = policy.FilterMachinesByACL(machine, peers, rules)
 	}
@@ -278,12 +276,33 @@ func addNextDNSMetadata(resolvers []*dnstype.Resolver, machine types.Machine) {
 	}
 }
 
+// CreateMapResponse returns a MapResponse for the given machine.
 func (m Mapper) CreateMapResponse(
 	mapRequest tailcfg.MapRequest,
 	machine *types.Machine,
 	pol *policy.ACLPolicy,
 ) ([]byte, error) {
-	mapResponse, err := m.tempWrap(machine, pol)
+	peers, err := m.db.ListPeers(machine)
+	if err != nil {
+		log.Error().
+			Caller().
+			Err(err).
+			Msg("Cannot fetch peers")
+
+		return nil, err
+	}
+
+	mapResponse, err := fullMapResponse(
+		pol,
+		machine,
+		peers,
+		m.stripEmailDomain,
+		m.baseDomain,
+		m.dnsCfg,
+		m.derpMap,
+		m.logtail,
+		m.randomClientPort,
+	)
 	if err != nil {
 		return nil, err
 	}

hscontrol/mapper/mapper_test.go

@@ -6,6 +6,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/davecgh/go-spew/spew"
 	"github.com/google/go-cmp/cmp"
 	"github.com/google/go-cmp/cmp/cmpopts"
 	"github.com/juanfont/headscale/hscontrol/policy"
@@ -164,35 +165,7 @@ func Test_fullMapResponse(t *testing.T) {
 	lastSeen := time.Date(2009, time.November, 10, 23, 9, 0, 0, time.UTC)
 	expire := time.Date(2500, time.November, 11, 23, 0, 0, 0, time.UTC)
 
-	tests := []struct {
+	mini := &types.Machine{
-		name    string
-		pol     *policy.ACLPolicy
-		machine *types.Machine
-		peers   types.Machines
-
-		stripEmailDomain bool
-		baseDomain       string
-		dnsConfig        *tailcfg.DNSConfig
-		derpMap          *tailcfg.DERPMap
-		logtail          bool
-		randomClientPort bool
-		want             *tailcfg.MapResponse
-		wantErr          bool
-	}{
-		// {
-		// 	name:             "empty-machine",
-		// 	machine:          types.Machine{},
-		// 	pol:              &policy.ACLPolicy{},
-		// 	dnsConfig:        &tailcfg.DNSConfig{},
-		// 	baseDomain:       "",
-		// 	stripEmailDomain: false,
-		// 	want:             nil,
-		// 	wantErr:          true,
-		// },
-		{
-			name: "no-pol-no-peers-map-response",
-			pol:  &policy.ACLPolicy{},
-			machine: &types.Machine{
 		ID:          0,
 		MachineKey:  "mkey:f08305b4ee4250b95a70f3b7504d048d75d899993c624a26d422c67af0422507",
 		NodeKey:     "nodekey:9b2ffa7e08cc421a3d2cca9012280f6a236fd0de0b4ce005b30a98ad930306fe",
@@ -230,17 +203,9 @@ func Test_fullMapResponse(t *testing.T) {
 			},
 		},
 		CreatedAt: created,
-			},
+	}
-			peers:            []types.Machine{},
+
-			stripEmailDomain: false,
+	tailMini := &tailcfg.Node{
-			baseDomain:       "",
-			dnsConfig:        &tailcfg.DNSConfig{},
-			derpMap:          &tailcfg.DERPMap{},
-			logtail:          false,
-			randomClientPort: false,
-			want: &tailcfg.MapResponse{
-				KeepAlive: false,
-				Node: &tailcfg.Node{
 		ID:       0,
 		StableID: "0",
 		Name:     "mini",
@@ -276,64 +241,9 @@ func Test_fullMapResponse(t *testing.T) {
 			tailcfg.CapabilityAdmin,
 			tailcfg.CapabilitySSH,
 		},
-				},
+	}
-				DERPMap:         &tailcfg.DERPMap{},
+
-				Peers:           []*tailcfg.Node{},
+	peer1 := types.Machine{
-				DNSConfig:       &tailcfg.DNSConfig{},
-				Domain:          "",
-				CollectServices: "false",
-				PacketFilter:    []tailcfg.FilterRule{},
-				UserProfiles:    []tailcfg.UserProfile{{LoginName: "mini", DisplayName: "mini"}},
-				SSHPolicy:       nil,
-				ControlTime:     &time.Time{},
-				Debug: &tailcfg.Debug{
-					DisableLogTail: true,
-				},
-			},
-			wantErr: false,
-		},
-		{
-			name: "no-pol-map-response",
-			pol:  &policy.ACLPolicy{},
-			machine: &types.Machine{
-				ID:          0,
-				MachineKey:  "mkey:f08305b4ee4250b95a70f3b7504d048d75d899993c624a26d422c67af0422507",
-				NodeKey:     "nodekey:9b2ffa7e08cc421a3d2cca9012280f6a236fd0de0b4ce005b30a98ad930306fe",
-				DiscoKey:    "discokey:cf7b0fd05da556fdc3bab365787b506fd82d64a70745db70e00e86c1b1c03084",
-				IPAddresses: []netip.Addr{netip.MustParseAddr("100.64.0.1")},
-				Hostname:    "mini",
-				GivenName:   "mini",
-				UserID:      0,
-				User:        types.User{Name: "mini"},
-				ForcedTags:  []string{},
-				LastSeen:    &lastSeen,
-				Expiry:      &expire,
-				HostInfo:    types.HostInfo{},
-				Endpoints:   []string{},
-				Routes: []types.Route{
-					{
-						Prefix:     types.IPPrefix(netip.MustParsePrefix("0.0.0.0/0")),
-						Advertised: true,
-						Enabled:    true,
-						IsPrimary:  false,
-					},
-					{
-						Prefix:     types.IPPrefix(netip.MustParsePrefix("192.168.0.0/24")),
-						Advertised: true,
-						Enabled:    true,
-						IsPrimary:  true,
-					},
-					{
-						Prefix:     types.IPPrefix(netip.MustParsePrefix("172.0.0.0/10")),
-						Advertised: true,
-						Enabled:    false,
-						IsPrimary:  true,
-					},
-				},
-				CreatedAt: created,
-			},
-			peers: []types.Machine{
-				{
 		ID:          1,
 		MachineKey:  "mkey:f08305b4ee4250b95a70f3b7504d048d75d899993c624a26d422c67af0422507",
 		NodeKey:     "nodekey:9b2ffa7e08cc421a3d2cca9012280f6a236fd0de0b4ce005b30a98ad930306fe",
@@ -350,56 +260,9 @@ func Test_fullMapResponse(t *testing.T) {
 		Endpoints:   []string{},
 		Routes:      []types.Route{},
 		CreatedAt:   created,
-				},
+	}
-			},
+
-			stripEmailDomain: false,
+	tailPeer1 := &tailcfg.Node{
-			baseDomain:       "",
-			dnsConfig:        &tailcfg.DNSConfig{},
-			derpMap:          &tailcfg.DERPMap{},
-			logtail:          false,
-			randomClientPort: false,
-			want: &tailcfg.MapResponse{
-				KeepAlive: false,
-				Node: &tailcfg.Node{
-					ID:       0,
-					StableID: "0",
-					Name:     "mini",
-					User:     0,
-					Key: mustNK(
-						"nodekey:9b2ffa7e08cc421a3d2cca9012280f6a236fd0de0b4ce005b30a98ad930306fe",
-					),
-					KeyExpiry: expire,
-					Machine: mustMK(
-						"mkey:f08305b4ee4250b95a70f3b7504d048d75d899993c624a26d422c67af0422507",
-					),
-					DiscoKey: mustDK(
-						"discokey:cf7b0fd05da556fdc3bab365787b506fd82d64a70745db70e00e86c1b1c03084",
-					),
-					Addresses: []netip.Prefix{netip.MustParsePrefix("100.64.0.1/32")},
-					AllowedIPs: []netip.Prefix{
-						netip.MustParsePrefix("100.64.0.1/32"),
-						netip.MustParsePrefix("0.0.0.0/0"),
-						netip.MustParsePrefix("192.168.0.0/24"),
-					},
-					Endpoints:         []string{},
-					DERP:              "127.3.3.40:0",
-					Hostinfo:          hiview(tailcfg.Hostinfo{}),
-					Created:           created,
-					Tags:              []string{},
-					PrimaryRoutes:     []netip.Prefix{netip.MustParsePrefix("192.168.0.0/24")},
-					LastSeen:          &lastSeen,
-					Online:            new(bool),
-					KeepAlive:         true,
-					MachineAuthorized: true,
-					Capabilities: []string{
-						tailcfg.CapabilityFileSharing,
-						tailcfg.CapabilityAdmin,
-						tailcfg.CapabilitySSH,
-					},
-				},
-				DERPMap: &tailcfg.DERPMap{},
-				Peers: []*tailcfg.Node{
-					{
 		ID:       1,
 		StableID: "1",
 		Name:     "peer1",
@@ -430,8 +293,101 @@ func Test_fullMapResponse(t *testing.T) {
 			tailcfg.CapabilityAdmin,
 			tailcfg.CapabilitySSH,
 		},
+	}
+
+	peer2 := types.Machine{
+		ID:          2,
+		MachineKey:  "mkey:f08305b4ee4250b95a70f3b7504d048d75d899993c624a26d422c67af0422507",
+		NodeKey:     "nodekey:9b2ffa7e08cc421a3d2cca9012280f6a236fd0de0b4ce005b30a98ad930306fe",
+		DiscoKey:    "discokey:cf7b0fd05da556fdc3bab365787b506fd82d64a70745db70e00e86c1b1c03084",
+		IPAddresses: []netip.Addr{netip.MustParseAddr("100.64.0.3")},
+		Hostname:    "peer2",
+		GivenName:   "peer2",
+		UserID:      1,
+		User:        types.User{Name: "peer2"},
+		ForcedTags:  []string{},
+		LastSeen:    &lastSeen,
+		Expiry:      &expire,
+		HostInfo:    types.HostInfo{},
+		Endpoints:   []string{},
+		Routes:      []types.Route{},
+		CreatedAt:   created,
+	}
+
+	tests := []struct {
+		name    string
+		pol     *policy.ACLPolicy
+		machine *types.Machine
+		peers   types.Machines
+
+		stripEmailDomain bool
+		baseDomain       string
+		dnsConfig        *tailcfg.DNSConfig
+		derpMap          *tailcfg.DERPMap
+		logtail          bool
+		randomClientPort bool
+		want             *tailcfg.MapResponse
+		wantErr          bool
+	}{
+		// {
+		// 	name:             "empty-machine",
+		// 	machine:          types.Machine{},
+		// 	pol:              &policy.ACLPolicy{},
+		// 	dnsConfig:        &tailcfg.DNSConfig{},
+		// 	baseDomain:       "",
+		// 	stripEmailDomain: false,
+		// 	want:             nil,
+		// 	wantErr:          true,
+		// },
+		{
+			name:             "no-pol-no-peers-map-response",
+			pol:              &policy.ACLPolicy{},
+			machine:          mini,
+			peers:            []types.Machine{},
+			stripEmailDomain: false,
+			baseDomain:       "",
+			dnsConfig:        &tailcfg.DNSConfig{},
+			derpMap:          &tailcfg.DERPMap{},
+			logtail:          false,
+			randomClientPort: false,
+			want: &tailcfg.MapResponse{
+				Node:            tailMini,
+				KeepAlive:       false,
+				DERPMap:         &tailcfg.DERPMap{},
+				Peers:           []*tailcfg.Node{},
+				DNSConfig:       &tailcfg.DNSConfig{},
+				Domain:          "",
+				CollectServices: "false",
+				PacketFilter:    []tailcfg.FilterRule{},
+				UserProfiles:    []tailcfg.UserProfile{{LoginName: "mini", DisplayName: "mini"}},
+				SSHPolicy:       nil,
+				ControlTime:     &time.Time{},
+				Debug: &tailcfg.Debug{
+					DisableLogTail: true,
 				},
 			},
+			wantErr: false,
+		},
+		{
+			name:    "no-pol-with-peer-map-response",
+			pol:     &policy.ACLPolicy{},
+			machine: mini,
+			peers: []types.Machine{
+				peer1,
+			},
+			stripEmailDomain: false,
+			baseDomain:       "",
+			dnsConfig:        &tailcfg.DNSConfig{},
+			derpMap:          &tailcfg.DERPMap{},
+			logtail:          false,
+			randomClientPort: false,
+			want: &tailcfg.MapResponse{
+				KeepAlive: false,
+				Node:      tailMini,
+				DERPMap:   &tailcfg.DERPMap{},
+				Peers: []*tailcfg.Node{
+					tailPeer1,
+				},
 				DNSConfig:       &tailcfg.DNSConfig{},
 				Domain:          "",
 				CollectServices: "false",
@@ -445,6 +401,55 @@ func Test_fullMapResponse(t *testing.T) {
 			},
 			wantErr: false,
 		},
+		{
+			name: "with-pol-map-response",
+			pol: &policy.ACLPolicy{
+				ACLs: []policy.ACL{
+					{
+						Action:       "accept",
+						Sources:      []string{"mini"},
+						Destinations: []string{"100.64.0.2:*"},
+					},
+				},
+			},
+			machine: mini,
+			peers: []types.Machine{
+				peer1,
+				peer2,
+			},
+			stripEmailDomain: false,
+			baseDomain:       "",
+			dnsConfig:        &tailcfg.DNSConfig{},
+			derpMap:          &tailcfg.DERPMap{},
+			logtail:          false,
+			randomClientPort: false,
+			want: &tailcfg.MapResponse{
+				KeepAlive: false,
+				Node:      tailMini,
+				DERPMap:   &tailcfg.DERPMap{},
+				Peers: []*tailcfg.Node{
+					tailPeer1,
+				},
+				DNSConfig:       &tailcfg.DNSConfig{},
+				Domain:          "",
+				CollectServices: "false",
+				PacketFilter: []tailcfg.FilterRule{
+					{
+						SrcIPs: []string{"100.64.0.1/32", "100.64.0.2/32"},
+						DstPorts: []tailcfg.NetPortRange{
+							{IP: "100.64.0.2/32", Ports: tailcfg.PortRangeAny},
+						},
+					},
+				},
+				UserProfiles: []tailcfg.UserProfile{{LoginName: "mini", DisplayName: "mini"}},
+				SSHPolicy:    nil,
+				ControlTime:  &time.Time{},
+				Debug: &tailcfg.Debug{
+					DisableLogTail: true,
+				},
+			},
+			wantErr: false,
+		},
 	}
 
 	for _, tt := range tests {
@@ -467,6 +472,8 @@ func Test_fullMapResponse(t *testing.T) {
 				return
 			}
 
+			spew.Dump(got)
+
 			if diff := cmp.Diff(
 				tt.want,
 				got,

hscontrol/policy/acls.go

@@ -125,8 +125,9 @@ func GenerateFilterRules(
 	machines types.Machines,
 	stripEmailDomain bool,
 ) ([]tailcfg.FilterRule, *tailcfg.SSHPolicy, error) {
+	// If there is no policy defined, we default to allow all
 	if policy == nil {
-		return []tailcfg.FilterRule{}, &tailcfg.SSHPolicy{}, nil
+		return tailcfg.FilterAllowAll, &tailcfg.SSHPolicy{}, nil
 	}
 
 	rules, err := policy.generateFilterRules(machines, stripEmailDomain)

hscontrol/policy/acls_test.go

@@ -2319,6 +2319,48 @@ func Test_getFilteredByACLPeers(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "failing-edge-case-during-p3-refactor",
+			args: args{
+				machines: []types.Machine{
+					{
+						ID:          1,
+						IPAddresses: []netip.Addr{netip.MustParseAddr("100.64.0.2")},
+						Hostname:    "peer1",
+						User:        types.User{Name: "mini"},
+					},
+					{
+						ID:          2,
+						IPAddresses: []netip.Addr{netip.MustParseAddr("100.64.0.3")},
+						Hostname:    "peer2",
+						User:        types.User{Name: "peer2"},
+					},
+				},
+				rules: []tailcfg.FilterRule{
+					{
+						SrcIPs: []string{"100.64.0.1/32"},
+						DstPorts: []tailcfg.NetPortRange{
+							{IP: "100.64.0.3/32", Ports: tailcfg.PortRangeAny},
+							{IP: "::/0", Ports: tailcfg.PortRangeAny},
+						},
+					},
+				},
+				machine: &types.Machine{
+					ID:          0,
+					IPAddresses: []netip.Addr{netip.MustParseAddr("100.64.0.1")},
+					Hostname:    "mini",
+					User:        types.User{Name: "mini"},
+				},
+			},
+			want: []types.Machine{
+				{
+					ID:          2,
+					IPAddresses: []netip.Addr{netip.MustParseAddr("100.64.0.3")},
+					Hostname:    "peer2",
+					User:        types.User{Name: "peer2"},
+				},
+			},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

hscontrol/protocol_common_poll.go

@@ -59,10 +59,6 @@ func (h *Headscale) handlePollCommon(
 
 	// update ACLRules with peer informations (to update server tags if necessary)
 	if h.ACLPolicy != nil {
-		// TODO(kradalby): Since this is not blocking, I might have introduced a bug here.
-		// It will be resolved later as we change up the policy stuff.
-		h.policyUpdateChan <- struct{}{}
-
 		// update routes with peer information
 		err = h.db.EnableAutoApprovedRoutes(h.ACLPolicy, machine)
 		if err != nil {

hscontrol/types/machine_test.go

@@ -1 +1,101 @@
 package types
+
+import (
+	"net/netip"
+	"testing"
+
+	"tailscale.com/tailcfg"
+)
+
+func Test_MachineCanAccess(t *testing.T) {
+	tests := []struct {
+		name     string
+		machine1 Machine
+		machine2 Machine
+		rules    []tailcfg.FilterRule
+		want     bool
+	}{
+		{
+			name: "other-cant-access-src",
+			machine1: Machine{
+				ID:          0,
+				IPAddresses: []netip.Addr{netip.MustParseAddr("100.64.0.1")},
+				Hostname:    "mini",
+				User:        User{Name: "mini"},
+			},
+			machine2: Machine{
+				ID:          2,
+				IPAddresses: []netip.Addr{netip.MustParseAddr("100.64.0.3")},
+				Hostname:    "peer2",
+				User:        User{Name: "peer2"},
+			},
+			rules: []tailcfg.FilterRule{
+				{
+					SrcIPs: []string{"100.64.0.2/32"},
+					DstPorts: []tailcfg.NetPortRange{
+						{IP: "100.64.0.3/32", Ports: tailcfg.PortRangeAny},
+					},
+				},
+			},
+			want: false,
+		},
+		{
+			name: "dest-cant-access-src",
+			machine1: Machine{
+				ID:          2,
+				IPAddresses: []netip.Addr{netip.MustParseAddr("100.64.0.3")},
+				Hostname:    "peer2",
+				User:        User{Name: "peer2"},
+			},
+			machine2: Machine{
+				ID:          0,
+				IPAddresses: []netip.Addr{netip.MustParseAddr("100.64.0.2")},
+				Hostname:    "mini",
+				User:        User{Name: "mini"},
+			},
+			rules: []tailcfg.FilterRule{
+				{
+					SrcIPs: []string{"100.64.0.2/32"},
+					DstPorts: []tailcfg.NetPortRange{
+						{IP: "100.64.0.3/32", Ports: tailcfg.PortRangeAny},
+					},
+				},
+			},
+			want: false,
+		},
+		{
+			name: "src-can-access-dest",
+			machine1: Machine{
+				ID:          0,
+				IPAddresses: []netip.Addr{netip.MustParseAddr("100.64.0.2")},
+				Hostname:    "mini",
+				User:        User{Name: "mini"},
+			},
+			machine2: Machine{
+				ID:          2,
+				IPAddresses: []netip.Addr{netip.MustParseAddr("100.64.0.3")},
+				Hostname:    "peer2",
+				User:        User{Name: "peer2"},
+			},
+			rules: []tailcfg.FilterRule{
+				{
+					SrcIPs: []string{"100.64.0.2/32"},
+					DstPorts: []tailcfg.NetPortRange{
+						{IP: "100.64.0.3/32", Ports: tailcfg.PortRangeAny},
+					},
+				},
+			},
+			want: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := tt.machine1.CanAccess(tt.rules, &tt.machine2)
+
+			if got != tt.want {
+				t.Errorf("canAccess() failed: want (%t), got (%t)", tt.want, got)
+			}
+		})
+	}
+}