Raise a machine in use adopted: keep its firewall, load no dropping table, guard the mesh's own ports, and take only the mesh's own modules (hq ADR 0100)

internal/bootstrap/adopted.go

@@ -0,0 +1,192 @@
+package bootstrap
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"sort"
+	"strconv"
+	"strings"
+
+	"github.com/novox/mesh-host/internal/declaration"
+)
+
+// What an adopted genesis changes about the foundation (novox/hq ADR 0100).
+//
+// **The firewall found on the machine stays in force.** The foundation's own filter drops by
+// default, and every base chain at a hook runs; an accept ends only its own chain and a drop in any
+// is final — so loading it would close whatever the machine serves. On an adopted machine it is
+// not loaded. Its duty, the store never reachable from outside, passes to the mesh's guard: a table
+// of the mesh's own that only refuses, and only the foundation's own ports, which genesis has just
+// checked free — so it cannot close anything the machine serves.
+
+// The guard, as the controller declares it: the same ids, paths and text, so the first push
+// finds it already there and takes it over unchanged.
+const (
+	guardID        = declaration.AdoptionPrefix + "guard"
+	guardUnitID    = declaration.AdoptionPrefix + "guard-unit"
+	guardRunningID = declaration.AdoptionPrefix + "guard-running"
+	guardPath      = "/etc/mesh/guard.nft"
+	guardUnit      = "mesh-guard.service"
+	guardUnitPath  = "/etc/systemd/system/" + guardUnit
+)
+
+// AsGuard renders the mesh's refusal-only table for the given machine ports. It passes everything
+// by default; it refuses the ports except from the machine itself — its loopback and the container
+// runtime's own networks — and from the private network, known by the interface a packet arrives
+// on and never by its source address; at prerouting, ahead of the runtime's destination
+// translation, in the inet family so both address families.
+//
+// Character for character the controller's (mesh-controller internal/catalogue AsGuard); a test
+// on each side holds its copy to the same golden text.
+func AsGuard(ports []int) string {
+	sorted := append([]int{}, ports...)
+	sort.Ints(sorted)
+	listed := make([]string, len(sorted))
+	for i, p := range sorted {
+		listed[i] = strconv.Itoa(p)
+	}
+	var b strings.Builder
+	b.WriteString("table inet mesh_guard {}\n")
+	b.WriteString("delete table inet mesh_guard\n")
+	b.WriteString("table inet mesh_guard {\n")
+	b.WriteString("\tchain prerouting {\n")
+	b.WriteString("\t\ttype filter hook prerouting priority raw; policy accept;\n")
+	fmt.Fprintf(&b, "\t\tiifname != \"lo\" iifname != \"docker0\" iifname != \"br-*\" "+
+		"iifname != \"mesh0\" tcp dport { %s } drop\n", strings.Join(listed, ", "))
+	b.WriteString("\t}\n")
+	b.WriteString("}\n")
+	return b.String()
+}
+
+// guardUnitText is the unit that loads the guard. Stopping it deletes only its own table — never a
+// flush, which would take the container runtime's rules and the found firewall with it.
+func guardUnitText() string {
+	return "[Unit]\n" +
+		"Description=The mesh's guard: refuses its own ports from outside (novox/hq ADR 0100)\n" +
+		"After=network-pre.target\n" +
+		"Wants=network-pre.target\n" +
+		"\n" +
+		"[Service]\n" +
+		"Type=oneshot\n" +
+		"RemainAfterExit=yes\n" +
+		"ExecStart=nft -f " + guardPath + "\n" +
+		"ExecReload=nft -f " + guardPath + "\n" +
+		"ExecStop=nft delete table inet mesh_guard\n" +
+		"\n" +
+		"[Install]\n" +
+		"WantedBy=multi-user.target\n"
+}
+
+// guardResources are the guard as three resources of kinds the host already has.
+func guardResources(ports []int) []map[string]any {
+	return []map[string]any{
+		{"id": guardID, "type": "file", "path": guardPath, "content": AsGuard(ports), "mode": "0644"},
+		{"id": guardUnitID, "type": "file", "path": guardUnitPath, "content": guardUnitText(), "mode": "0644"},
+		{"id": guardRunningID, "type": "service", "unit": guardUnit, "state": "running",
+			"boot": "enabled", "restart-on": []any{guardID, guardUnitID}},
+	}
+}
+
+// guardAfter is where the guard goes: once the container runtime runs, before anything publishes
+// a port.
+const guardAfter = "container-runtime-running"
+
+// AdoptedRewrite says what RewriteAdopted did.
+type AdoptedRewrite struct {
+	Removed []string
+	Guarded []int
+}
+
+// RewriteAdopted makes the produced bundle one for an adopted machine: the foundation's own filter
+// taken out, and the mesh's guard put in its place, guarding the store's and the broker's
+// management ports on this node. The nftables package stays: the guard is loaded with it, and
+// installing a package loads no table. Openings are not the bundle's — the first push declares
+// them, once there is a controller to derive them.
+func RewriteAdopted(r *Rewritten, p FoundationPorts) (AdoptedRewrite, error) {
+	var out AdoptedRewrite
+	p = p.orDefaults()
+	bundle := r.Bundle
+	var err error
+	for _, id := range []string{"base-filter-loaded", "base-filter"} {
+		if !r.declares(id) {
+			continue
+		}
+		if bundle, err = removeResource(bundle, id); err != nil {
+			return out, err
+		}
+		out.Removed = append(out.Removed, id)
+	}
+
+	out.Guarded = []int{p.Store, p.Management}
+	var text bytes.Buffer
+	text.WriteString(",\n    // The mesh's guard (novox/hq ADR 0100): this machine is adopted, so its own firewall\n" +
+		"    // stays in force and the foundation's filter is not loaded. The guard only refuses: the\n" +
+		"    // store's and the broker's management ports, except from the machine and the private network.")
+	for _, res := range guardResources(out.Guarded) {
+		var one bytes.Buffer
+		enc := json.NewEncoder(&one)
+		enc.SetEscapeHTML(false)
+		if err := enc.Encode(res); err != nil {
+			return out, err
+		}
+		text.WriteString("\n    ")
+		text.Write(bytes.TrimSpace(one.Bytes()))
+		text.WriteString(",")
+	}
+	insert := bytes.TrimSuffix(text.Bytes(), []byte(","))
+
+	_, _, to, err := resourceAt(bundle, guardAfter)
+	if err != nil {
+		return out, fmt.Errorf("the guard goes after %q, and %w", guardAfter, err)
+	}
+	rest := bundle[to:]
+	joined := make([]byte, 0, len(bundle)+len(insert))
+	joined = append(joined, bundle[:to]...)
+	joined = append(joined, insert...)
+	// What followed the resource — its own comma, or the end of the list — now follows the guard.
+	if trimmed := bytes.TrimLeft(rest, " \t\r\n"); len(trimmed) > 0 && trimmed[0] != ',' && trimmed[0] != ']' {
+		return out, fmt.Errorf("the bundle does not separate %q from what follows it the way a list does", guardAfter)
+	}
+	joined = append(joined, rest...)
+
+	parsed, err := declaration.ParseFileTrusted(joined)
+	if err != nil {
+		return out, fmt.Errorf("the bundle stopped being a declaration once it was made an adopted one, which is this installer's fault: %w", err)
+	}
+	r.Bundle, r.Declaration, r.Resources = joined, parsed, len(parsed.Resources)
+	return out, nil
+}
+
+// declares is whether the produced bundle names a resource.
+func (r Rewritten) declares(id string) bool {
+	for _, res := range r.Declaration.Resources {
+		if res.Identity() == id {
+			return true
+		}
+	}
+	return false
+}
+
+// genesisTakes are the modules an adopted genesis takes as it installs them: the foundation's and
+// the mesh's own, whose names genesis checked free, so taking them replaces nothing a predecessor
+// ran. The private network is not among them — it rewrites the machine's hosts file and the
+// container runtime's configuration whole — and neither is anything the operator installs later.
+var genesisTakes = map[string]bool{
+	RegistryModule: true, ControlPlaneModule: true, BuilderModule: true,
+	"postgres": true, "lavinmq": true, "mesh-vault": true, "mesh-catalog": true,
+}
+
+// takeIfAdopted takes one of genesis's own modules on an adopted node, once it is assigned and
+// before the push that raises it.
+func takeIfAdopted(ctx context.Context, o Options, control controlPlane, module string, say func(string)) error {
+	if !o.Adopted || !genesisTakes[module] {
+		return nil
+	}
+	if _, err := control.tell(ctx, "take", o.Node, module); err != nil {
+		return err
+	}
+	say("  taken             " + module + " on " + o.Node + " — the mesh's own, its name checked free")
+	return nil
+}

internal/bootstrap/adopted_test.go

@@ -0,0 +1,192 @@
+package bootstrap
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/novox/mesh-host/internal/declaration"
+)
+
+// Defends novox/hq ADR 0100: an adopted genesis loads no table that drops by default or holds an
+// accept; the mesh guards its own ports in a table that only refuses; and genesis takes the mesh's
+// own modules as it installs them, and nothing else.
+
+// The same golden text the controller's test holds its AsGuard to.
+const goldenGuard = `table inet mesh_guard {}
+delete table inet mesh_guard
+table inet mesh_guard {
+	chain prerouting {
+		type filter hook prerouting priority raw; policy accept;
+		iifname != "lo" iifname != "docker0" iifname != "br-*" iifname != "mesh0" tcp dport { 5432, 15672 } drop
+	}
+}
+`
+
+func TestTheGuardIsExactlyThisTable(t *testing.T) {
+	if got := AsGuard([]int{15672, 5432}); got != goldenGuard {
+		t.Fatalf("the guard changed:\n%s", got)
+	}
+}
+
+func TestAnAdoptedBundleLoadsNoDroppingTableAndExactlyTheGuard(t *testing.T) {
+	r := producedBundle(t)
+	p := FoundationPorts{Store: 5433, Management: 15673}
+	if _, err := RewritePorts(&r, p, ""); err != nil {
+		t.Fatal(err)
+	}
+	got, err := RewriteAdopted(&r, p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Join(got.Removed, ",") != "base-filter-loaded,base-filter" {
+		t.Errorf("removed %v", got.Removed)
+	}
+	at := map[string]int{}
+	var guards []*declaration.File
+	for i, res := range r.Declaration.Resources {
+		at[res.Identity()] = i
+		if f, ok := res.(*declaration.File); ok {
+			if strings.Contains(f.Content, "policy drop") || strings.Contains(f.Content, " accept\n") &&
+				!strings.Contains(f.Content, "policy accept") {
+				t.Errorf("%s loads a table that drops or accepts: %q", f.ID, f.Content)
+			}
+			if f.Path == guardPath {
+				guards = append(guards, f)
+			}
+		}
+		if s, ok := res.(*declaration.Service); ok && s.Unit == "nftables.service" {
+			t.Errorf("the foundation's filter is still loaded by %s", s.ID)
+		}
+	}
+	if len(guards) != 1 {
+		t.Fatalf("%d guard table(s)", len(guards))
+	}
+	if !strings.Contains(guards[0].Content, "tcp dport { 5433, 15673 } drop") {
+		t.Errorf("the guard does not refuse this node's ports: %s", guards[0].Content)
+	}
+	if strings.Count(guards[0].Content, "accept") != 1 || !strings.Contains(guards[0].Content, "policy accept") {
+		t.Errorf("the guard holds an accept of its own: %s", guards[0].Content)
+	}
+	for _, id := range []string{guardID, guardUnitID, guardRunningID} {
+		if _, ok := at[id]; !ok {
+			t.Errorf("the bundle has no %s", id)
+		}
+	}
+	if !(at["container-runtime-running"] < at[guardID] && at[guardRunningID] < at["store"]) {
+		t.Errorf("the guard is not between the runtime and the store: %v", at)
+	}
+	if _, kept := at["base-filter-package"]; !kept {
+		t.Error("nft, which loads the guard, is no longer installed")
+	}
+	unit := r.Declaration.Resources[at[guardRunningID]].(*declaration.Service)
+	if unit.Unit != guardUnit || unit.State != "running" || strings.Join(unit.RestartOn, ",") != guardID+","+guardUnitID {
+		t.Errorf("the guard's service: %+v", unit)
+	}
+	stop := r.Declaration.Resources[at[guardUnitID]].(*declaration.File).Content
+	if !strings.Contains(stop, "ExecStop=nft delete table inet mesh_guard") || strings.Contains(stop, "flush") {
+		t.Errorf("stopping the guard does not delete only its own table: %s", stop)
+	}
+}
+
+func TestAConvergedBundleIsNotMadeAnAdoptedOne(t *testing.T) {
+	// The converged genesis keeps the foundation's filter, byte for byte (novox/hq ADR 0088).
+	r := producedBundle(t)
+	for _, res := range r.Declaration.Resources {
+		if strings.HasPrefix(res.Identity(), declaration.AdoptionPrefix) {
+			t.Errorf("a converged bundle carries %s", res.Identity())
+		}
+	}
+	if !r.declares("base-filter-loaded") {
+		t.Error("a converged bundle lost its filter")
+	}
+}
+
+func TestAnAdoptedGenesisTakesTheMeshsOwnModulesBeforePushingThem(t *testing.T) {
+	t.Setenv("TMPDIR", t.TempDir())
+	for _, c := range []struct {
+		module string
+		takes  bool
+	}{{RegistryModule, true}, {ControlPlaneModule, true}, {BuilderModule, true}, {"gitea", false}} {
+		rec := &controlRecorder{settings: map[string]string{}}
+		control := controlPlane{container: "temp-mesh-controller", run: rec.run, timeout: time.Second}
+		o := Options{Node: "anchor", Adopted: true, Wait: time.Second}
+		if _, err := installModule(context.Background(), o, control, c.module, []byte(`{}`), quietly); err != nil {
+			t.Fatal(err)
+		}
+		assign, take, push := rec.index("assign anchor "+c.module), rec.index("take anchor "+c.module), rec.index("push anchor")
+		if !c.takes {
+			if take >= 0 {
+				t.Errorf("%s was taken at genesis", c.module)
+			}
+			continue
+		}
+		if !(assign >= 0 && assign < take && take < push) {
+			t.Errorf("%s: assign %d, take %d, push %d: %v", c.module, assign, take, push, rec.told)
+		}
+	}
+}
+
+func TestAConvergedGenesisTakesNothing(t *testing.T) {
+	t.Setenv("TMPDIR", t.TempDir())
+	rec := &controlRecorder{settings: map[string]string{}}
+	control := controlPlane{container: "temp-mesh-controller", run: rec.run, timeout: time.Second}
+	if _, err := installModule(context.Background(), Options{Node: "anchor", Wait: time.Second}, control,
+		RegistryModule, []byte(`{}`), quietly); err != nil {
+		t.Fatal(err)
+	}
+	if rec.index("take") >= 0 {
+		t.Errorf("a converged genesis took a module: %v", rec.told)
+	}
+}
+
+func TestAnAdoptedGenesisOpensTheRegistryFromAnywhere(t *testing.T) {
+	t.Setenv("TMPDIR", t.TempDir())
+	rec := &controlRecorder{settings: map[string]string{}}
+	control := controlPlane{container: "temp-mesh-controller", run: rec.run, timeout: time.Second}
+	o := Options{Node: "anchor", Adopted: true, Ports: FoundationPorts{Registry: 5100}, Wait: time.Second}
+	if _, err := installModule(context.Background(), o, control, RegistryModule, []byte(`{}`), quietly); err != nil {
+		t.Fatal(err)
+	}
+	if got := rec.settings["distribution-settings.json"]; got != `{"expose":{"5000":"anywhere"},"ports":{"5000":5100}}` {
+		t.Errorf("the registry was told %s", got)
+	}
+}
+
+func TestAnAdoptedGenesisChoosesTheFilterAndLoadsNone(t *testing.T) {
+	rec := &controlRecorder{settings: map[string]string{}}
+	control := controlPlane{container: "mesh-controller", run: rec.run, timeout: time.Second}
+	o := Options{Node: "anchor", Adopted: true, Answers: map[string]string{"packet-filter": "nftables"}}
+	filter, err := ChooseAndInstallFilter(context.Background(), o, control, quietly)
+	if err != nil || filter != "nftables" {
+		t.Fatalf("%q %v", filter, err)
+	}
+	if len(rec.told) != 0 {
+		t.Errorf("an adopted genesis installed a filter: %v", rec.told)
+	}
+}
+
+func TestAnAdoptedNodeIsRecordedAdopted(t *testing.T) {
+	stop := errors.New("stop here")
+	runtime := &asked{answer: func(name string, args []string) (string, error) {
+		joined := strings.Join(args, " ")
+		switch {
+		case strings.Contains(joined, "node list"):
+			return "", nil
+		case strings.Contains(joined, "node add"):
+			return "", nil
+		}
+		return "", fmt.Errorf("%w: %s %v", stop, name, args)
+	}}
+	_, _ = Enrol(context.Background(), Options{
+		Node: "anchor", Adopted: true, State: t.TempDir() + "/state.json", Timeout: time.Second,
+		Host: "/usr/local/bin/mesh-host", HostInBackground: true,
+	}, arch(t), controlPlane{container: "temp-mesh-controller", run: runtime.run, timeout: time.Second},
+		func(string) {})
+	if !runtime.ran("node add anchor --adopted") {
+		t.Errorf("the node was not added adopted: %v", runtime.commands)
+	}
+}

internal/bootstrap/bootstrap.go

@@ -34,6 +34,8 @@ import (
 	"fmt"
 	"strings"
 	"time"
+
+	"github.com/novox/mesh-host/internal/firewall"
 )
 
 // Step names one stage. A failure says which one, because "the bootstrap failed" is a sentence
@@ -377,6 +379,23 @@ func Run(ctx context.Context, o Options, d Deps, say func(string)) (Result, erro
 
 	// Which half of the host applies things here. Asked of the machine and proved, because
 	// `mesh-host` pins this at link time and an installer run by hand has no link time.
+	// An adopted machine keeps the firewall it was found with, so the mesh must speak it; one no
+	// host speaks is refused here, before anything changes (novox/hq ADR 0100).
+	if o.Adopted {
+		kind, name, err := firewall.Detect(ctx, d.Run)
+		if err != nil {
+			return result, failed(StepPreflight, err)
+		}
+		if kind == firewall.Unsupported {
+			return result, failed(StepPreflight, fmt.Errorf(
+				"this machine is filtered by %s, and no host speaks that firewall yet. An adopted "+
+					"machine keeps its firewall in force, so the mesh could neither open what it needs "+
+					"through it nor say what it would close. Nothing was changed", name))
+		}
+		result.Firewall = string(kind)
+		say("  adopted           what is on this machine is kept; its firewall (" + string(kind) + ") stays in force")
+	}
+
 	sys, err := WorkOutSystem(ctx, d.Run, o.System)
 	if err != nil {
 		return result, failed(StepPreflight, err)
@@ -444,6 +463,14 @@ func Run(ctx context.Context, o Options, d Deps, say func(string)) (Result, erro
 	if moved.Places > 0 {
 		say(fmt.Sprintf("  ports             %d place(s) rewritten to this node's foundation ports", moved.Places))
 	}
+	if o.Adopted {
+		adopted, err := RewriteAdopted(&rewritten, o.Ports)
+		if err != nil {
+			return result, failed(StepBundle, err)
+		}
+		say(fmt.Sprintf("  adopted bundle    the foundation's filter is not loaded (%s); the mesh's guard refuses %v from outside",
+			strings.Join(adopted.Removed, ", "), adopted.Guarded))
+	}
 	for _, c := range []struct {
 		what, path string
 		made       bool
@@ -718,7 +745,9 @@ func Run(ctx context.Context, o Options, d Deps, say func(string)) (Result, erro
 
 	// ---- 17. filter -----------------------------------------------------------------------
 	say("filter — required, so the question is which, not whether")
-	if err := ChooseAndInstallFilter(ctx, o, permanentControl, say); err != nil {
+	filter, err := ChooseAndInstallFilter(ctx, o, permanentControl, say)
+	result.Filter = filter
+	if err != nil {
 		return result, failed(StepFilter, err)
 	}
 
@@ -736,6 +765,12 @@ func Run(ctx context.Context, o Options, d Deps, say func(string)) (Result, erro
 		return result, failed(StepExport, err)
 	}
 
+	if o.Adopted {
+		say("\nthis machine is a mesh of one adopted node: it builds its own software, holds its graph " +
+			"and sits on its private network, and what it ran before is kept as it was, behind the firewall " +
+			"it was found with. Take each module on it once its data has moved; converge it when done.")
+		return result, nil
+	}
 	say("\nthis machine is a mesh of one node: it builds its own software, holds its graph, " +
 		"sits on its private network, and filters what modules declared.")
 	say("what remains is somebody else's: adding nodes, and assigning what they should run.")

internal/bootstrap/enrol.go

@@ -72,7 +72,13 @@ func Enrol(ctx context.Context, o Options, sys system.System, control controlPla
 	if mentions(nodes, o.Node) {
 		say("  already a node    " + o.Node)
 	} else {
-		if _, err := control.tell(ctx, "node", "add", o.Node); err != nil {
+		add := []string{"node", "add", o.Node}
+		if o.Adopted {
+			// The controller records the node's mode; an adopted one keeps what it was found with
+			// until each module is taken (novox/hq ADR 0100).
+			add = append(add, "--adopted")
+		}
+		if _, err := control.tell(ctx, add...); err != nil {
 			return out, err
 		}
 		out.Added = true

internal/bootstrap/module.go

@@ -214,8 +214,12 @@ func pinPlaceholder(manifest []byte, reference, module string) ([]byte, int, err
 }
 
 // prepareModule is what genesis tells the controller about a module on this node once it is
-// assigned and before it is pushed: the ports this node gave it (novox/hq ADR 0100).
+// assigned and before it is pushed: the ports this node gave it, and on an adopted node that the
+// module is taken (novox/hq ADR 0100).
 func prepareModule(ctx context.Context, o Options, control controlPlane, module string,
 	say func(string)) error {
-	return setFoundationSettings(ctx, o, control, module, say)
+	if err := setFoundationSettings(ctx, o, control, module, say); err != nil {
+		return err
+	}
+	return takeIfAdopted(ctx, o, control, module, say)
 }

internal/bootstrap/phase2.go

@@ -150,16 +150,22 @@ func PlaceOnTheNetwork(ctx context.Context, o Options, control controlPlane,
 
 // ChooseAndInstallFilter picks the packet filter — required, so the question is which, not
 // whether — and installs it.
-func ChooseAndInstallFilter(ctx context.Context, o Options, control controlPlane, say func(string)) error {
+func ChooseAndInstallFilter(ctx context.Context, o Options, control controlPlane, say func(string)) (string, error) {
 	filter, err := decide(Choice{
 		Name:     "packet-filter",
 		Question: "Which packet filter should this machine run?",
 		Options:  []string{"nftables"},
 	}, o.Answers["packet-filter"], o.Prompt, say)
 	if err != nil {
-		return err
+		return "", err
 	}
-	return InstallFromCatalogue(ctx, o, control, filter, say)
+	if o.Adopted {
+		// The firewall found here stays in force until the node converges; the filter is
+		// chosen now and assigned by the flip (novox/hq ADR 0100).
+		say("  not installed     " + filter + " — this machine is adopted; converging it assigns " + filter)
+		return filter, nil
+	}
+	return filter, InstallFromCatalogue(ctx, o, control, filter, say)
 }
 
 // InstallExtras installs what was asked for beyond the floor.

internal/bootstrap/retire.go

@@ -132,18 +132,29 @@ func RetireTheTemporaryControlPlane(ctx context.Context, o Options, sys system.S
 // where the comment explaining it lives. A comment that outlives the thing it describes is worse
 // than no comment: it is the file telling somebody the machine has a control plane it does not.
 func removeResource(bundle []byte, id string) ([]byte, error) {
+	previous, from, to, err := resourceAt(bundle, id)
+	if err != nil {
+		return nil, err
+	}
+	return cut(bundle, previous, from, to), nil
+}
+
+// resourceAt finds one resource's object in a bundle's text by its id: where the one before it
+// ended, and where it starts and ends — comments and strings skipped, so an id quoted in a comment
+// or a command is never mistaken for the resource.
+func resourceAt(bundle []byte, id string) (previous, from, to int, err error) {
 	array := indexOutsideStrings(bundle, `"resources"`)
 	if array < 0 {
-		return nil, fmt.Errorf("this bundle has no resources array, so there is nothing to take out of it")
+		return 0, 0, 0, fmt.Errorf("this bundle has no resources array, so there is nothing to take out of it")
 	}
 	open := indexOutsideStrings(bundle[array:], "[")
 	if open < 0 {
-		return nil, fmt.Errorf("this bundle's resources are not a list")
+		return 0, 0, 0, fmt.Errorf("this bundle's resources are not a list")
 	}
 	open += array
 
-	depth, from := 0, -1
-	previous := open
+	depth := 0
+	from, previous = -1, open
 	inString, escaped, inLine, inBlock := false, false, false, false
 	for i := open + 1; i < len(bundle); i++ {
 		c := bundle[i]
@@ -181,16 +192,16 @@ func removeResource(bundle []byte, id string) ([]byte, error) {
 				break
 			}
 			if isResource(bundle[from:i+1], id) {
-				return cut(bundle, previous, from, i+1), nil
+				return previous, from, i + 1, nil
 			}
 			previous = i + 1
 			from = -1
 		case c == ']' && depth == 0:
-			return nil, fmt.Errorf(
+			return 0, 0, 0, fmt.Errorf(
 				"this bundle declares no %q, so there is nothing to take out of it", id)
 		}
 	}
-	return nil, fmt.Errorf("this bundle's resources list does not end")
+	return 0, 0, 0, fmt.Errorf("this bundle's resources list does not end")
 }
 
 // isResource reports whether one resource's text is the one wanted.