A unit may be user-scoped: applied through the account's own manager (hq ADR 0177)

A workstation's per-user daemons — a window manager's reload watcher, an
audio mask, a memory guard — are units in the operator account's own service
manager, and until now had no form the mesh could send (to-be 29). The
`service` shape gains `scope` ("system", the default, or "user") and `user`
(the account, named ${machine:account} by a module); a user-scoped unit
without an account, or a system unit naming one, is refused at parse.

The host reaches the account's manager as `systemctl --user --machine=<account>@`
from its own process: no environment to forge, no user to switch to. Done on
the runner rather than per system, since every system's reading of a unit
already goes through systemctl. Apply, reflect-only and removal all go through
the same manager, and the applied record carries scope and user so removal
gives the unit back to the manager it came from. It answers only while that
manager runs — a login, or lingering enabled for the account; declaring
lingering is a follow-up.

Tests: a user-scoped unit is started and enabled in the account's manager and
recorded with its scope; a system unit never sees --user; the validation of
scope and user.

cmd/mesh-host/main.go

@@ -1432,7 +1432,7 @@ func applyAndKeep(ctx context.Context, opts options, raw []byte, signed *store.D
 	// (novox/hq ADR 0140). Reported whatever the node's mode: a converged node's filter needs it,
 	// and an adopted one becomes converged without a further round trip. A machine that cannot read
 	// its own routing table says nothing rather than guessing, and is sent no filter.
-	if links, err := outward.Links(""); err != nil {
+	if links, err := outward.Links("", ""); err != nil {
 		fmt.Fprintf(os.Stderr, "mesh-host: applied, and could not read which links face outside: %v\n", err)
 	} else {
 		report.Outward = links

internal/apply/apply.go

@@ -58,6 +58,8 @@ type Outcome struct {
 	kept string
 	// stateless is a service whose unit's lifecycle is the machine's (novox/hq ADR 0117).
 	stateless bool
+	// scope and user are, for a service, whose manager it was applied through (novox/hq ADR 0177).
+	scope, user string
 	// found is, for a service, its unit as the host first found it (novox/hq ADR 0118).
 	found *store.FoundUnit
 	// reads is, for a container, the digest of each file it was created reading, by path — so
@@ -563,6 +565,8 @@ func ApplyKeeping(
 			Kept:      kept,
 			Reads:     outcome.reads,
 			Stateless: outcome.stateless,
+			Scope:     outcome.scope,
+			User:      outcome.user,
 			Found:     outcome.found,
 			Holds:     holds(resource),
 		})
@@ -1043,10 +1047,12 @@ type unitReloader interface {
 
 func applyService(ctx context.Context, sys system.System, r *declaration.Service, run Runner,
 	changed map[string]bool, previous store.Applied) (Outcome, error) {
+	run = managerFor(r.Scope, r.User, run)
 	if r.Stateless() {
 		return reflectOnly(ctx, sys, r, run, changed)
 	}
 	out := begin(r)
+	out.scope, out.user = r.Scope, r.User
 	var changes []string
 
 	// A file the service reflects changed, and it may be the unit's own file or a drop-in: the
@@ -1186,7 +1192,9 @@ func applyService(ctx context.Context, sys system.System, r *declaration.Service
 // a machine that uses another — and it reads the change when whatever starts it does.
 func reflectOnly(ctx context.Context, sys system.System, r *declaration.Service, run Runner,
 	changed map[string]bool) (Outcome, error) {
+	run = managerFor(r.Scope, r.User, run)
 	out := begin(r)
+	out.scope, out.user = r.Scope, r.User
 	out.stateless = true
 	restart := reflected(r, changed)
 	reload := restartedBy(r.ReloadOn, changed)
@@ -1407,6 +1415,25 @@ func applyPackage(ctx context.Context, sys system.System, r *declaration.Package
 	if err != nil {
 		return out, err
 	}
+	if r.Absent {
+		// Declared absent (novox/hq ADR 0175): removed when it is here, left alone when it is not.
+		if !installed {
+			out.Action = "unchanged"
+			out.Detail = "not installed, as declared"
+			return out, nil
+		}
+		if err := sys.RemovePackage(ctx, run, r.Package); err != nil {
+			return out, fmt.Errorf("removing %s: %w", r.Package, err)
+		}
+		if still, err := sys.PackageInstalled(ctx, run, r.Package); err != nil {
+			return out, err
+		} else if still {
+			return out, fmt.Errorf("%s was removed without error and the package database still has it", r.Package)
+		}
+		out.Action = "removed"
+		out.Detail = "declared absent; its configuration is left where the package manager leaves it"
+		return out, nil
+	}
 	if installed {
 		out.Action = "unchanged"
 		out.Detail = "already installed"
@@ -1583,6 +1610,11 @@ func containerSpecReading(r *declaration.Container, declares, reads map[string]s
 	for _, n := range r.Networks {
 		b.WriteString("also-on " + n + "\n")
 	}
+	// And the capabilities it was granted (ADR 0170): one gained or dropped is a different
+	// container, and the runtime cannot change a running one's.
+	for _, c := range r.Capabilities {
+		b.WriteString("cap " + c + "\n")
+	}
 	// The cadence is part of what was declared, so a changed schedule is a changed spec — the marker
 	// moves and the install is reported "updated" and re-established. Added only when present, so no
 	// ordinary container's or run-once step's digest moves for a field it does not set.
@@ -1777,6 +1809,9 @@ func applyContainer(ctx context.Context, r *declaration.Container, run Runner,
 	if r.Network != "" {
 		args = append(args, "--network", r.Network)
 	}
+	for _, c := range r.Capabilities {
+		args = append(args, "--cap-add", c)
+	}
 	for _, d := range r.Dns {
 		args = append(args, "--dns", d)
 	}
@@ -2208,6 +2243,7 @@ func declaredDigest(r declaration.Resource) string {
 // what was actually done — a unit already as it was found is forgotten, not "restored".
 func removeService(ctx context.Context, sys system.System, a store.Applied, run Runner,
 	made bool) (string, string, error) {
+	run = managerFor(a.Scope, a.User, run)
 	if a.Stateless {
 		// Declared with no state (novox/hq ADR 0117): its lifecycle was never the mesh's, and the
 		// declaration that said so is the operator's word to hold to, a file of the mesh's or not.
@@ -2382,3 +2418,23 @@ func moduleOf(identity string) (string, bool) {
 	}
 	return identity[:at], true
 }
+
+// managerFor routes a unit's commands to the manager it belongs to (novox/hq ADR 0177). A system
+// unit's go to the machine's manager as they always did. A user-scoped unit's go to the account's
+// own: `systemctl --user --machine=<account>@`, which reaches that manager from the host's own
+// process without an environment to forge or a user to switch to — and which only answers while
+// the account's manager runs (a login, or lingering enabled for the account). Done on the runner
+// rather than in each system: every system's reading of a unit already goes through `systemctl`,
+// so this is one place instead of one per system and one per method.
+func managerFor(scope, user string, run Runner) Runner {
+	if scope != declaration.ScopeUser || user == "" {
+		return run
+	}
+	return func(ctx context.Context, name string, args ...string) (string, error) {
+		if name != "systemctl" {
+			return run(ctx, name, args...)
+		}
+		scoped := append([]string{"--user", "--machine=" + user + "@"}, args...)
+		return run(ctx, name, scoped...)
+	}
+}

internal/apply/left_out_test.go

@@ -134,3 +134,81 @@ func TestALeftOutModuleIsNeitherRemovedNorForgotten(t *testing.T) {
 		t.Fatalf("keeping the left-out module's container was not said: %+v", report.Outcomes)
 	}
 }
+
+// A container's capabilities reach the runtime and are part of its spec (novox/hq ADR 0170).
+func TestACapabilityReachesTheRuntimeAndTheSpec(t *testing.T) {
+	var ran []string
+	run := func(_ context.Context, name string, args ...string) (string, error) {
+		if name != "docker" {
+			return "", errors.New("not installed")
+		}
+		switch args[0] {
+		case "info":
+			return "29.0.0\n", nil
+		case "container":
+			return "false\t\n", errors.New("no such container")
+		case "run":
+			ran = args
+			return "deadbeef\n", nil
+		}
+		return "", nil
+	}
+	d := parseTrusted(t, `{"declaration":1,"resources":[
+	  {"id":"fw","type":"container","name":"fw","image":"`+pinned+`","network":"host","capabilities":["NET_ADMIN"]}
+	]}`)
+	_, _, _ = Apply(context.Background(), archHost(t), d, store.State{}, store.OriginCarried, run, nil, nil)
+	granted := false
+	for i, a := range ran {
+		if a == "--cap-add" && i+1 < len(ran) && ran[i+1] == "NET_ADMIN" {
+			granted = true
+		}
+	}
+	if !granted {
+		t.Fatalf("the capability was not granted: %v", ran)
+	}
+	with := d.Resources[0].(*declaration.Container)
+	without := *with
+	without.Capabilities = nil
+	if containerSpec(with, inputs{}) == containerSpec(&without, inputs{}) {
+		t.Fatal("a capability is not part of the container's spec")
+	}
+}
+
+// A package may be declared absent (novox/hq ADR 0175): removed when it is installed, read back,
+// left alone when it is not.
+func TestAPackageDeclaredAbsentIsRemovedWhenPresentAndLeftWhenNot(t *testing.T) {
+	installed := true
+	var ran []string
+	run := func(_ context.Context, name string, args ...string) (string, error) {
+		ran = append(ran, name+" "+strings.Join(args, " "))
+		if name != "pacman" {
+			return "", nil
+		}
+		switch args[0] {
+		case "-Q":
+			if args[1] == "pacman" || installed {
+				return args[1] + " 1.0\n", nil
+			}
+			return "", errors.New("package not found")
+		case "-R":
+			installed = false
+		}
+		return "", nil
+	}
+	d := parseTrusted(t, `{"declaration":1,"resources":[{"id":"front-end","type":"package","package":"ufw","absent":true}]}`)
+	report, _, err := Apply(context.Background(), archHost(t), d, store.State{}, store.OriginCarried, run, nil, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if report.Outcomes[0].Action != "removed" || !strings.Contains(strings.Join(ran, "\n"), "pacman -R --noconfirm ufw") {
+		t.Fatalf("an installed package declared absent was not removed: %+v\n%v", report.Outcomes[0], ran)
+	}
+	ran = nil
+	report, _, err = Apply(context.Background(), archHost(t), d, store.State{}, store.OriginCarried, run, nil, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if report.Outcomes[0].Action != "unchanged" || strings.Contains(strings.Join(ran, "\n"), "-R") {
+		t.Fatalf("a package already absent was touched: %+v\n%v", report.Outcomes[0], ran)
+	}
+}

internal/apply/opening.go

@@ -76,6 +76,16 @@ func retireFirewall(ctx context.Context, d *declaration.Declaration, origin stri
 	if origin != store.OriginDeclared || d.Adoption != nil || rec == nil || rec.Kind != string(firewall.UFW) || !rec.WasActive {
 		return "", nil
 	}
+	if !firewall.Installed(ctx, run) {
+		// Uninstalled (novox/hq ADR 0175): retired for good, by the module that replaced it. Said
+		// once, and nothing is asked of a command that is not there.
+		if rec.RetiredBy != firewall.RetiredRemoved {
+			rec.RetiredBy = firewall.RetiredRemoved
+			log("  the found firewall (ufw) is no longer installed; the mesh's filter is what filters this machine")
+			return "removed: ufw is no longer installed; the mesh's filter is what filters this machine", nil
+		}
+		return "", nil
+	}
 	active := firewall.Active(ctx, run)
 	if !active && !(rec.Forward != nil && !rec.DisabledByMesh) {
 		// Inactive, and either the mesh's doing already or nobody's recorded here: said as found,

internal/apply/opening_test.go

@@ -8,6 +8,7 @@ import (
 	"path/filepath"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/novox/mesh-host/internal/declaration"
 	"github.com/novox/mesh-host/internal/store"
@@ -522,3 +523,33 @@ func TestUfwIsNotRetiredUntilTheMeshsOwnFilterIsLoaded(t *testing.T) {
 		t.Errorf("ufw was not retired once the mesh's filter was loaded: active %v, %+v", u.active, state.Firewall)
 	}
 }
+
+// A front end that is no longer installed is recorded as removed, said once, and asked nothing of
+// (novox/hq ADR 0175).
+func TestAnUninstalledFrontEndIsRetiredForGood(t *testing.T) {
+	dir := t.TempDir()
+	u := &ufwMachine{installed: false, ruleset: "table inet mesh\n"}
+	known := store.State{Firewall: &store.FoundFirewall{Kind: "ufw", WasActive: true, DisabledByMesh: true,
+		RetiredBy: "mesh", FoundAt: time.Now()}}
+	converged := parse(t, `{"declaration":1,"resources":[`+withConf(dir)+`]}`)
+	report, state, err := applyWith(t, converged, known, u.run)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if state.Firewall.RetiredBy != "removed" || !strings.Contains(report.Firewall, "no longer installed") {
+		t.Fatalf("record %+v, said %q", state.Firewall, report.Firewall)
+	}
+	u.asked = nil
+	report, _, err = applyWith(t, converged, state, u.run)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if report.Firewall != "" {
+		t.Errorf("said again: %q", report.Firewall)
+	}
+	for _, a := range u.asked {
+		if strings.HasPrefix(a, "ufw") && a != "ufw status" {
+			t.Errorf("asked something of a front end that is not there: %v", u.asked)
+		}
+	}
+}

internal/apply/userscope_test.go

@@ -0,0 +1,99 @@
+package apply
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/novox/mesh-host/internal/store"
+)
+
+// Defends novox/hq ADR 0177: a unit in the operator account's own service manager is applied
+// through that manager — `systemctl --user --machine=<account>@` — and never as a system unit of
+// the same name; its record remembers the scope so removal goes the same way.
+
+// accountManager is a user's service manager whose one unit starts when asked, recording the
+// commands and refusing any that reach it outside the account's scope.
+func accountManager(account string, commands *[]string) Runner {
+	active, enabled := false, false
+	return func(_ context.Context, name string, args ...string) (string, error) {
+		line := name + " " + strings.Join(args, " ")
+		*commands = append(*commands, line)
+		if name == "systemctl" && !strings.HasPrefix(line, "systemctl --user --machine="+account+"@ ") {
+			return "", fmt.Errorf("a system-scope command reached the account's manager: %s", line)
+		}
+		switch {
+		case strings.Contains(line, " start "):
+			active = true
+			return "", nil
+		case strings.Contains(line, " stop "):
+			active = false
+			return "", nil
+		case strings.Contains(line, " enable "):
+			enabled = true
+			return "", nil
+		case strings.Contains(line, " disable "):
+			enabled = false
+			return "", nil
+		case strings.Contains(line, "is-enabled"):
+			if enabled {
+				return "enabled", nil
+			}
+			return "disabled", nil
+		case strings.Contains(line, "show") && strings.Contains(line, "ActiveState"):
+			if active {
+				return "LoadState=loaded\nActiveState=active\nSubState=running", nil
+			}
+			return "LoadState=loaded\nActiveState=inactive\nSubState=dead", nil
+		}
+		return "", nil
+	}
+}
+
+func TestAUserScopedUnitIsAppliedThroughTheAccountsManager(t *testing.T) {
+	var commands []string
+	decl := `{"declaration":1,"resources":[
+	  {"id":"i3.watcher","type":"service","unit":"i3-reload-watcher.service","state":"running","boot":"enabled","scope":"user","user":"ops"}
+	]}`
+	report, known, err := Apply(context.Background(), archHost(t), parse(t, decl),
+		store.State{}, store.OriginDeclared, accountManager("ops", &commands), nil, nil)
+	if err != nil {
+		t.Fatalf("apply: %v\n%s", err, strings.Join(commands, "\n"))
+	}
+	if !report.Changed() {
+		t.Fatal("a unit that was stopped and is now running changed nothing")
+	}
+	var started, enabled bool
+	for _, c := range commands {
+		if c == "systemctl --user --machine=ops@ start i3-reload-watcher.service" {
+			started = true
+		}
+		if c == "systemctl --user --machine=ops@ enable i3-reload-watcher.service" {
+			enabled = true
+		}
+	}
+	if !started || !enabled {
+		t.Fatalf("the unit was not started and enabled in the account's manager:\n%s", strings.Join(commands, "\n"))
+	}
+	recorded, ok := known.At("service", "i3-reload-watcher.service")
+	if !ok || recorded.Scope != "user" || recorded.User != "ops" {
+		t.Fatalf("the record does not say whose manager the unit is in: %+v", recorded)
+	}
+}
+
+func TestASystemUnitIsUntouchedByTheScope(t *testing.T) {
+	var commands []string
+	decl := `{"declaration":1,"resources":[
+	  {"id":"x.daemon","type":"service","unit":"sshd.service","state":"running","boot":"enabled"}
+	]}`
+	if _, _, err := Apply(context.Background(), archHost(t), parse(t, decl),
+		store.State{}, store.OriginDeclared, unitIn(true, &commands), nil, nil); err != nil {
+		t.Fatal(err)
+	}
+	for _, c := range commands {
+		if strings.Contains(c, "--user") || strings.Contains(c, "--machine") {
+			t.Fatalf("a system unit was addressed to an account's manager: %s", c)
+		}
+	}
+}

internal/declaration/declaration.go

@@ -684,6 +684,16 @@ type Service struct {
 	// declaration that reports success and stops being true at the next power cut.
 	Boot string `json:"boot,omitempty"`
 
+	// Scope is whose service manager the unit belongs to: "system" (absent means system), or
+	// "user" — the operator account's own manager (novox/hq ADR 0177). A workstation's per-user
+	// daemons — a window manager's reload watcher, an audio mask, a memory guard — are units in
+	// that manager, and until this they had no form the mesh could send. A user-scoped unit names
+	// its User; the host talks to that account's manager and never starts a system unit by the
+	// same name.
+	Scope string `json:"scope,omitempty"`
+	// User is the account whose manager a user-scoped unit lives in. Required with scope "user",
+	// refused otherwise; a module names it ${machine:account} and never the person.
+	User string `json:"user,omitempty"`
 	// RestartOn names resources whose change means this service must be restarted.
 	//
 	// Because a running service does not re-read its configuration. Replace the file, find the
@@ -729,11 +739,33 @@ func (s *Service) Identity() string { return s.ID }
 func (s *Service) Kind() Type       { return TypeService }
 func (s *Service) Target() string   { return s.Unit }
 
+// ScopeSystem and ScopeUser are the two managers a unit may belong to (novox/hq ADR 0177).
+const (
+	ScopeSystem = "system"
+	ScopeUser   = "user"
+)
+
+// UserScoped is whether this unit lives in an account's own service manager.
+func (s *Service) UserScoped() bool { return s.Scope == ScopeUser }
+
 func (s *Service) validate(where string, _ bool) []string {
 	var problems []string
 	if s.Unit == "" {
 		problems = append(problems, where+": a service needs a unit")
 	}
+	switch s.Scope {
+	case "", ScopeSystem:
+		if s.User != "" {
+			problems = append(problems, where+": a system unit names no user; only a user-scoped unit does")
+		}
+	case ScopeUser:
+		if s.User == "" {
+			problems = append(problems, where+": a user-scoped unit names the account whose manager it lives in")
+		}
+	default:
+		problems = append(problems, fmt.Sprintf(
+			"%s: scope %q; a unit is in the \"system\" manager or the operator account's \"user\" one", where, s.Scope))
+	}
 	switch {
 	case s.State == "running" || s.State == "stopped":
 	case s.State != "":
@@ -870,6 +902,12 @@ type Package struct {
 	ID      string `json:"id"`
 	Type    Type   `json:"type"`
 	Package string `json:"package"`
+	// Absent declares that the package is NOT installed (novox/hq ADR 0175): the host removes it
+	// when it is, and leaves a machine that never had it alone. For the one case a module replaces
+	// software the machine was found with and the operator has decided it does not come back — the
+	// firewall front end a converged machine's filter module retired. Nothing to undo when the
+	// declaration drops it: the host does not install what a declaration stopped saying is absent.
+	Absent bool `json:"absent,omitempty"`
 }
 
 func (p *Package) Identity() string { return p.ID }
@@ -940,6 +978,12 @@ type Container struct {
 	// its siblings can name before any of them can resolve anything.
 	Dns []string `json:"dns,omitempty"`
 
+	// Capabilities are the Linux capabilities this container is granted beyond the runtime's
+	// default set, by name (novox/hq ADR 0170): a holder's runtime that changes the machine's packet
+	// filter asks for NET_ADMIN. Exactly these, named in the spec so a change recreates the
+	// container; a privileged container stays undeclarable.
+	Capabilities []string `json:"capabilities,omitempty"`
+
 	// Networks are networks this container also joins once created, by name — a found network a
 	// per-machine setting keeps for a taken container (novox/hq ADR 0163, rule 4), so a
 	// neighbour that resolves it there keeps resolving it until the neighbour is taken too.
@@ -1039,6 +1083,12 @@ func (c *Container) validate(where string, _ bool) []string {
 				"static address anywhere but a user-defined one")
 		}
 	}
+	for _, cap := range c.Capabilities {
+		if !capabilityName.MatchString(cap) {
+			problems = append(problems, where+": capabilities names "+strconv.Quote(cap)+", which is not a "+
+				"capability's name (CAP_NET_ADMIN or NET_ADMIN)")
+		}
+	}
 	for _, n := range c.Networks {
 		problems = append(problems, (&Network{Name: n}).validate(where+": networks", false)...)
 		if n == c.Network {
@@ -1209,6 +1259,10 @@ type Adoption struct {
 	Untaken map[string][]string `json:"untaken,omitempty"`
 }
 
+// capabilityName is what a Linux capability is called: upper case, underscores, an optional CAP_
+// prefix. The runtime accepts either spelling.
+var capabilityName = regexp.MustCompile(`^(CAP_)?[A-Z][A-Z0-9_]*$`)
+
 // AdoptionPrefix is the id prefix of what the mesh itself declares because a node is adopted —
 // its openings and its guard. Nothing under it belongs to a module, so none of it is ever held.
 const AdoptionPrefix = "adoption."

internal/declaration/declaration_test.go

@@ -504,3 +504,23 @@ func TestKeptNetworksAndLeftOutModulesAreReadStrictly(t *testing.T) {
 		t.Fatalf("a carried bundle leaving modules out was accepted: %v", err)
 	}
 }
+
+// A container may ask for a capability by name, and nothing else (novox/hq ADR 0170).
+func TestACapabilityIsNamedOrRefused(t *testing.T) {
+	image := "postgres@sha256:" + strings.Repeat("a", 64)
+	d, err := Parse([]byte(`{"declaration":1,"resources":[
+	  {"id":"fw","type":"container","name":"fw","image":"` + image + `","network":"host","capabilities":["NET_ADMIN","CAP_NET_RAW"]}
+	]}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got := d.Resources[0].(*Container).Capabilities; len(got) != 2 || got[0] != "NET_ADMIN" {
+		t.Fatalf("capabilities read as %v", got)
+	}
+	for _, bad := range []string{`"net_admin"`, `"ALL;rm -rf /"`, `"privileged"`} {
+		if _, err := Parse([]byte(`{"declaration":1,"resources":[
+		  {"id":"fw","type":"container","name":"fw","image":"` + image + `","capabilities":[` + bad + `]}]}`)); err == nil {
+			t.Errorf("%s was accepted as a capability", bad)
+		}
+	}
+}

internal/declaration/userscope_test.go

@@ -0,0 +1,30 @@
+package declaration
+
+import (
+	"strings"
+	"testing"
+)
+
+// novox/hq ADR 0177: a unit is in the system manager or an account's own; a user-scoped one names
+// the account, a system one may not, and any other word is refused.
+func TestAUserScopedUnitNamesItsAccountAndASystemOneMayNot(t *testing.T) {
+	cases := []struct{ scope, user, wants string }{
+		{"user", "ops", ""},
+		{"", "", ""},
+		{"system", "", ""},
+		{"user", "", "names the account"},
+		{"", "ops", "names no user"},
+		{"session", "ops", "scope \"session\""},
+	}
+	for _, c := range cases {
+		s := &Service{ID: "m.u", Type: TypeService, Unit: "u.service", State: "running", Scope: c.scope, User: c.user}
+		problems := s.validate("m.u", false)
+		got := strings.Join(problems, "; ")
+		if c.wants == "" && len(problems) != 0 {
+			t.Fatalf("scope %q user %q refused: %s", c.scope, c.user, got)
+		}
+		if c.wants != "" && !strings.Contains(got, c.wants) {
+			t.Fatalf("scope %q user %q: wanted a refusal saying %q, got %q", c.scope, c.user, c.wants, got)
+		}
+	}
+}

internal/firewall/filters.go

@@ -319,8 +319,17 @@ func Active(ctx context.Context, run Runner) bool {
 	return err == nil && statusActive(out)
 }
 
+// Installed says whether ufw is on this machine at all: a command that is not there is a front end
+// that was uninstalled (novox/hq ADR 0175), not one that is silent.
+func Installed(ctx context.Context, run Runner) bool {
+	_, err := run(ctx, "ufw", "status")
+	return !missing(err)
+}
+
 // Retirements of a found firewall, as the host records them.
 const (
 	RetiredByMesh  = "mesh"
 	RetiredFoundSo = "found-inactive"
+	// RetiredRemoved is a front end uninstalled by the module that replaced it (ADR 0175).
+	RetiredRemoved = "removed"
 )

internal/outward/links.go

@@ -29,17 +29,32 @@ import (
 // routing table without one.
 const ProcNet = "/proc/net"
 
-// Links are the interfaces carrying a default route, for both address families, sorted and without
-// repeats.
+// SysClassNet is where the kernel lists the machine's network interfaces, one directory each. A
+// parameter for the same reason.
+const SysClassNet = "/sys/class/net"
+
+// Links are the interfaces carrying a default route, for both address families, and every interface
+// backed by a physical device, sorted and without repeats.
+//
+// **A physical link faces outside whether or not it is up** (novox/hq issue 197). The filter accepts
+// whatever did not arrive on a link named here, so a link left out of this list is not filtered at
+// all. A cable unplugged when the machine last reported carries no default route, and was left out:
+// plugged in, everything arriving on it was accepted until the next report and the next push — and a
+// second physical link that never carries the default route was never filtered. A physical device is
+// read from the kernel's own list, where it has a `device` entry; a bridge, a veth, the tunnel and the
+// loopback have none, and stay what they are, this machine's own.
 //
 // A machine may have more than one: a laptop with a cable and a radio has two, and both face
 // outside. A machine with none — no route off itself — returns nothing, and the mesh refuses to
 // compose a filter for it rather than writing a rule around a link with no name, which would be a
 // rule set that does not load and a machine filtering nothing while its unit reports success.
-func Links(procNet string) ([]string, error) {
+func Links(procNet, sysClassNet string) ([]string, error) {
 	if procNet == "" {
 		procNet = ProcNet
 	}
+	if sysClassNet == "" {
+		sysClassNet = SysClassNet
+	}
 	seen := map[string]bool{}
 
 	four, err := defaultsV4(filepath.Join(procNet, "route"))
@@ -50,7 +65,11 @@ func Links(procNet string) ([]string, error) {
 	if err != nil {
 		return nil, err
 	}
-	for _, name := range append(four, six...) {
+	devices, err := physical(sysClassNet)
+	if err != nil {
+		return nil, err
+	}
+	for _, name := range append(append(four, six...), devices...) {
 		if name != "" && name != "lo" {
 			seen[name] = true
 		}
@@ -64,6 +83,25 @@ func Links(procNet string) ([]string, error) {
 	return out, nil
 }
 
+// physical is every interface the kernel lists with a device behind it. A list that is not there is
+// not an error — a machine without sysfs mounted reports what its routing table says, as before.
+func physical(sysClassNet string) ([]string, error) {
+	entries, err := os.ReadDir(sysClassNet)
+	if os.IsNotExist(err) {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	var out []string
+	for _, e := range entries {
+		if _, err := os.Stat(filepath.Join(sysClassNet, e.Name(), "device")); err == nil {
+			out = append(out, e.Name())
+		}
+	}
+	return out, nil
+}
+
 // defaultsV4 reads /proc/net/route, whose columns are
 //
 //	Iface Destination Gateway Flags RefCnt Use Metric Mask ...

internal/outward/links_test.go

@@ -32,7 +32,7 @@ func TestLinksAreTheOnesCarryingADefaultRoute(t *testing.T) {
 	write(t, dir, "route", routeV4)
 	write(t, dir, "ipv6_route", routeV6)
 
-	got, err := Links(dir)
+	got, err := Links(dir, t.TempDir())
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -52,7 +52,7 @@ func TestAZeroDestinationWithAMaskIsNotADefaultRoute(t *testing.T) {
 	write(t, dir, "route", `Iface	Destination	Gateway 	Flags	RefCnt	Use	Metric	Mask		MTU	Window	IRTT
 br-abc	00000000	00000000	0001	0	0	0	00FFFFFF	0	0	0
 `)
-	got, err := Links(dir)
+	got, err := Links(dir, t.TempDir())
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -67,7 +67,7 @@ br-abc	00000000	00000000	0001	0	0	0	00FFFFFF	0	0	0
 func TestNoDefaultRouteIsNoLinks(t *testing.T) {
 	dir := t.TempDir()
 	write(t, dir, "route", "Iface\tDestination\tGateway \tFlags\tRefCnt\tUse\tMetric\tMask\t\tMTU\tWindow\tIRTT\n")
-	got, err := Links(dir)
+	got, err := Links(dir, t.TempDir())
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -81,7 +81,7 @@ func TestNoDefaultRouteIsNoLinks(t *testing.T) {
 func TestAMissingTableIsNotAFailure(t *testing.T) {
 	dir := t.TempDir()
 	write(t, dir, "route", routeV4)
-	got, err := Links(dir)
+	got, err := Links(dir, t.TempDir())
 	if err != nil {
 		t.Fatalf("a missing v6 table should not fail: %v", err)
 	}
@@ -97,7 +97,7 @@ func TestALinkIsReportedOnce(t *testing.T) {
 	write(t, dir, "ipv6_route",
 		"00000000000000000000000000000000 00 00000000000000000000000000000000 00 "+
 			"fe800000000000000000000000000001 00000400 00000001 00000000 00000003     enp9s0\n")
-	got, err := Links(dir)
+	got, err := Links(dir, t.TempDir())
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -109,7 +109,7 @@ func TestALinkIsReportedOnce(t *testing.T) {
 // Against this machine's own routing table, so the parse is held to what the kernel actually writes
 // and not only to a fixture written to agree with it.
 func TestAgainstThisMachinesOwnTable(t *testing.T) {
-	got, err := Links("")
+	got, err := Links("", "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -118,3 +118,39 @@ func TestAgainstThisMachinesOwnTable(t *testing.T) {
 	}
 	t.Logf("this machine's outward links: %v", got)
 }
+
+// sysNet is a /sys/class/net: each name a directory, with a `device` entry when a device backs it.
+func sysNet(t *testing.T, physical []string, virtual []string) string {
+	t.Helper()
+	dir := t.TempDir()
+	for _, name := range physical {
+		if err := os.MkdirAll(filepath.Join(dir, name, "device"), 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	for _, name := range virtual {
+		if err := os.MkdirAll(filepath.Join(dir, name), 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	return dir
+}
+
+// **A physical link faces outside whether or not it carries the default route** (novox/hq issue
+// 197). A machine on its radio with its cable unplugged reported only the radio, and the filter then
+// accepted everything arriving on the cable the moment it was plugged in. Bridges, veths, the tunnel
+// and the loopback have no device behind them and stay this machine's own.
+func TestEveryPhysicalLinkFacesOutsideUpOrDown(t *testing.T) {
+	proc := t.TempDir()
+	write(t, proc, "route", `Iface	Destination	Gateway 	Flags	RefCnt	Use	Metric	Mask		MTU	Window	IRTT
+wlp5s0	00000000	01FEA8C0	0003	0	0	600	00000000	0	0	0
+`)
+	sys := sysNet(t, []string{"wlp5s0", "enp6s0"}, []string{"lo", "docker0", "br-0123456789ab", "veth1", "mesh0"})
+	got, err := Links(proc, sys)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if want := []string{"enp6s0", "wlp5s0"}; !reflect.DeepEqual(got, want) {
+		t.Fatalf("outward links are %v, want %v", got, want)
+	}
+}

internal/profile/detectors.go

@@ -15,6 +15,9 @@ const (
 	CapServiceManager   = "service-manager"
 	CapFirewall         = "firewall"
 	CapOverlay          = "overlay"
+	// CapVirtualisation is a running virtualisation daemon: what the lab raises its machines on
+	// (novox/hq ADR 0172), and what grants a module the daemon's socket.
+	CapVirtualisation   = "virtualisation"
 	CapGraphicalSession = "graphical-session"
 	// CapSeat is hardware: somewhere a display server COULD run. CapGraphicalSession above is
 	// state: whether one IS running. Assignment needs the first.
@@ -205,6 +208,11 @@ func Default(runner Runner) []Detector {
 			why:    "lists the ruleset — needs the tool AND the privilege to use it",
 			runner: runner,
 		},
+		commandCapability{
+			name: CapVirtualisation, command: "incus", args: []string{"info"},
+			why:    "asks the virtualisation daemon about itself — a running daemon, not an installed client",
+			runner: runner,
+		},
 		commandCapability{
 			name: CapOverlay, command: "wg", args: []string{"show", "interfaces"},
 			why:    "asks the kernel for interfaces — needs the module, not just the tool",

internal/store/store.go

@@ -82,6 +82,10 @@ type Applied struct {
 	// 0117) — kept here because removal happens once the declaration that said so is gone, and a
 	// service removed as if it had a state is stopped: the machine's network manager, for one.
 	Stateless bool `json:"stateless,omitempty"`
+	// Scope and User are, for a service in an account's own manager (novox/hq ADR 0177), which
+	// manager — so removal gives the unit back through the same one it was applied through.
+	Scope string `json:"scope,omitempty"`
+	User  string `json:"user,omitempty"`
 
 	// Found is, for a service, the state its unit was in when this host first applied it — before
 	// the mesh started, stopped, enabled or disabled anything. Removal gives that back and nothing

internal/system/alpine.go

@@ -46,6 +46,11 @@ func (a alpine) PackageInstalled(ctx context.Context, run Runner, name string) (
 	return strings.TrimSpace(out) != "", nil
 }
 
+func (alpine) RemovePackage(ctx context.Context, run Runner, name string) error {
+	_, err := run(ctx, "apk", "del", name)
+	return err
+}
+
 func (alpine) InstallPackage(ctx context.Context, run Runner, name string) error {
 	_, err := run(ctx, "apk", "add", "--no-cache", name)
 	return err

internal/system/android.go

@@ -65,6 +65,10 @@ func (a android) InstallPackage(context.Context, Runner, string) error {
 	return fmt.Errorf("%w: package", ErrUnsupported)
 }
 
+func (a android) RemovePackage(context.Context, Runner, string) error {
+	return fmt.Errorf("%w: package", ErrUnsupported)
+}
+
 func (a android) ServiceState(context.Context, Runner, string) (string, error) {
 	return "", fmt.Errorf("%w: service (init is not reachable without root)", ErrUnsupported)
 }

internal/system/arch.go

@@ -39,6 +39,14 @@ func (a arch) PackageInstalled(ctx context.Context, run Runner, name string) (bo
 	return true, nil
 }
 
+// RemovePackage removes one package and nothing it depends on: `-R`, not `-Rs`, because what else
+// relied on a dependency is not this declaration's to know. pacman keeps a configuration file the
+// operator changed as `.pacsave`, which is what "never flushed" comes to once the front end is gone.
+func (arch) RemovePackage(ctx context.Context, run Runner, name string) error {
+	_, err := run(ctx, "pacman", "-R", "--noconfirm", name)
+	return err
+}
+
 func (arch) InstallPackage(ctx context.Context, run Runner, name string) error {
 	out, err := run(ctx, "pacman", "-S", "--noconfirm", "--needed", name)
 	if err == nil {

internal/system/system.go

@@ -51,6 +51,9 @@ type System interface {
 
 	PackageInstalled(ctx context.Context, run Runner, name string) (bool, error)
 	InstallPackage(ctx context.Context, run Runner, name string) error
+	// RemovePackage uninstalls one package, leaving its dependencies and anything the operator
+	// changed in its configuration where the package manager leaves them (novox/hq ADR 0175).
+	RemovePackage(ctx context.Context, run Runner, name string) error
 
 	// ServiceState is "running" or "stopped". A unit that does not exist is an error, never
 	// "stopped" — reporting absence as satisfaction is the fault this host exists to prevent.