Experimental implementation of Policy v2 (#2214)

* utility iterator for ipset

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

* split policy -> policy and v1

This commit split out the common policy logic and policy implementation
into separate packages.

policy contains functions that are independent of the policy implementation,
this typically means logic that works on tailcfg types and generic formats.
In addition, it defines the PolicyManager interface which the v1 implements.

v1 is a subpackage which implements the PolicyManager using the "original"
policy implementation.

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

* use polivyv1 definitions in integration tests

These can be marshalled back into JSON, which the
new format might not be able to.

Also, just dont change it all to JSON strings for now.

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

* formatter: breaks lines

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

* remove compareprefix, use tsaddr version

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

* remove getacl test, add back autoapprover

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

* use policy manager tag handling

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

* rename display helper for user

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

* introduce policy v2 package

policy v2 is built from the ground up to be stricter
and follow the same pattern for all types of resolvers.

TODO introduce
aliass
resolver

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

* wire up policyv2 in integration testing

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

* split policy v2 tests into seperate workflow to work around github limit

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

* add policy manager output to /debug

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

* update changelog

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

---------

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

hscontrol/poll.go

@@ -10,10 +10,9 @@ import (
 	"time"
 
 	"github.com/juanfont/headscale/hscontrol/mapper"
+	"github.com/juanfont/headscale/hscontrol/policy"
 	"github.com/juanfont/headscale/hscontrol/types"
-	"github.com/juanfont/headscale/hscontrol/util"
 	"github.com/rs/zerolog/log"
-	"github.com/samber/lo"
 	"github.com/sasha-s/go-deadlock"
 	xslices "golang.org/x/exp/slices"
 	"tailscale.com/net/tsaddr"
@@ -459,25 +458,10 @@ func (m *mapSession) handleEndpointUpdate() {
 		// TODO(kradalby): I am not sure if we need this?
 		nodesChangedHook(m.h.db, m.h.polMan, m.h.nodeNotifier)
 
-		// Take all the routes presented to us by the node and check
-		// if any of them should be auto approved by the policy.
-		// If any of them are, add them to the approved routes of the node.
-		// Keep all the old entries and compact the list to remove duplicates.
-		var newApproved []netip.Prefix
-		for _, route := range m.node.Hostinfo.RoutableIPs {
-			if m.h.polMan.NodeCanApproveRoute(m.node, route) {
-				newApproved = append(newApproved, route)
-			}
-		}
-		if newApproved != nil {
-			newApproved = append(newApproved, m.node.ApprovedRoutes...)
-			slices.SortFunc(newApproved, util.ComparePrefix)
-			slices.Compact(newApproved)
-			newApproved = lo.Filter(newApproved, func(route netip.Prefix, index int) bool {
-				return route.IsValid()
-			})
-			m.node.ApprovedRoutes = newApproved
-
+		// Approve routes if they are auto-approved by the policy.
+		// If any of them are approved, report them to the primary route tracker
+		// and send updates accordingly.
+		if policy.AutoApproveRoutes(m.h.polMan, m.node) {
 			if m.h.primaryRoutes.SetRoutes(m.node.ID, m.node.SubnetRoutes()...) {
 				ctx := types.NotifyCtx(m.ctx, "poll-primary-change", m.node.Hostname)
 				m.h.nodeNotifier.NotifyAll(ctx, types.UpdateFull())