WIP: smb-server module and nfs-server's local-network grant (hq issue 613, ADR 0341)

Paused: the module's manifest test, README and a full merge-check run are still to do; tests pass locally for both modules.
2026-10-13 11:24:03 +02:00
18 changed files with 2558 additions and 19 deletions
@@ -17,7 +17,20 @@ another node requires.
  (`/etc/nfs-server/machines`, rendered by the mesh), never one a consumer gives, and it must lie inside
  the private network's range. The control node, or any node, gets a share only when both name it. A
  want that is not granted, and a grant nobody wants, are said by `exports`. Port 2049 is opened to the
-  mesh only; the home network is never named.
+  mesh by default. The machine's local network is reached only by a grant to `local-network` (below).
+- **The local network, only when granted and admitted** (novox/hq ADR 0341, after ADR 0340). `grants` may
+  name `local-network` in a node's place: `library=ws:rw,local-network:ro`. The process then reads the
+  machine's links (`ip -j`) and takes the subnets on the links carrying its default route that lie wholly
+  in a private range (RFC 1918, fc00::/7); a public subnet, the private network's link and container
+  bridges are never counted, and no range is ever typed in a setting. It exports to such a subnet only
+  when the mesh's packet filter (table `inet mesh`, chain `input`, read with `nft -j list ruleset`)
+  admits 2049/tcp from all of it, which it does once the assignment binds 2049 with the reach
+  `local-network`. A grant the filter does not admit is not exported, said by `exports`, and makes the
+  module unhealthy, naming that act. Every device on the local network then acts as the folder's owner,
+  as the hand-written export it replaces already allowed.
+- **A dataset's `sharenfs` is cleared only when nobody loses the folder.** `adopt` refuses while the
+  property, by its value or the file ZFS writes for it, exports to a client the mesh's live export does
+  not cover: for a property to the home network, the module's `local-network` export.
 - **Every client is the folder's owner.** NFS with `sec=sys` believes the user id a client sends, and one
  id names different accounts on different machines. Every line is `all_squash` with `anonuid` and
  `anongid` read from the folder's owner on this machine, so a file written from any node lands owned by
@@ -11,7 +11,7 @@ import (

 func TestStrayFindsAnExportOfTheModulesThatNoFileCarries(t *testing.T) {
 	live := []Entry{{Path: "/srv/library", Client: "10.0.0.4"}}
-	if got := Stray(live, nil, nil, meshRange); len(got) != 1 {
+	if got := Stray(live, nil, nil, meshRange, nil); len(got) != 1 {
 		t.Errorf("an export inside the mesh range that no file carries is the module's leftover: %+v", got)
 	}
 }
@@ -21,7 +21,7 @@ func TestStrayLeavesAnExportAnotherFileCarriesEvenInsideTheMeshRange(t *testing.
 	// ZFS's own file exports the library to a client inside the mesh's range.
 	foreign := ParseExports("/srv/library 10.0.0.9(rw,no_subtree_check)\n", "/etc/exports.d/zfs.exports")
 	live := []Entry{{Path: "/srv/library", Client: "10.0.0.9", Options: "rw"}}
-	if got := Stray(live, nil, foreign, meshRange); len(got) != 0 {
+	if got := Stray(live, nil, foreign, meshRange, nil); len(got) != 0 {
 		t.Errorf("what ZFS's file exports is not the module's, whatever its client: %+v", got)
 	}
 }
@@ -30,7 +30,7 @@ func TestStrayLeavesAnExportAnotherFileCarriesEvenInsideTheMeshRange(t *testing.
 func TestStrayLeavesAClientOutsideTheMeshRange(t *testing.T) {
 	live := []Entry{{Path: "/srv/library", Client: "192.0.2.0/24"}, {Path: "/srv/library", Client: "192.0.2.7"},
 		{Path: "/srv/library", Client: "10.0.0.0/16"}}
-	if got := Stray(live, nil, nil, meshRange); len(got) != 0 {
+	if got := Stray(live, nil, nil, meshRange, nil); len(got) != 0 {
 		t.Errorf("a client the module never exports to (outside or wider than the mesh's range) is not its leftover: %+v", got)
 	}
 }
@@ -0,0 +1,417 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/netip"
+	"sort"
+	"strings"
+)
+
+// A share granted to the machine's local network (novox/hq ADR 0341 clauses 8 and 9, after ADR 0340).
+//
+// **The grant names `local-network`, never a range.** `grants` may name `local-network` for a share beside
+// node names: `library=ws:rw,local-network:ro`. The export goes to the subnets this machine's own local
+// network is, by ADR 0340's rules: the networks on the links that carry its default route (the uplink),
+// each wholly inside a private range (RFC 1918, or fc00::/7), never a public or link-local one, never the
+// private network's own link or a container bridge. A range typed in a setting is never used.
+//
+// **A grant the filter does not admit is not exported, and is said.** ADR 0340 lets an assignment bind a
+// port with the reach `local-network`, and the filter then admits it from those subnets on that port's
+// rule alone. The module does not take the reach on trust: every pass it reads the mesh's filter (the
+// table `inet mesh`, chain `input`) and exports to a local subnet only when 2049/tcp is admitted from all
+// of it. Otherwise the share is not exported there, and the status and the health say so, naming the act
+// (bind 2049 with the reach local-network) — a grant never reads as served while the filter drops it.
+//
+// **What this does not promise.** NFS with sec=sys trusts the client, so every device on the local
+// network acts as the share's owner (all_squash, as for a node). That is what the hand-written export it
+// replaces already allowed.
+
+// LocalNetwork is the name a grant gives the machine's local network.
+const LocalNetwork = "local-network"
+
+// NFSPort is the port the filter must admit from a local subnet before a share is exported to it.
+const NFSPort = 2049
+
+// private are the ranges a local network must lie wholly inside (ADR 0340 §2).
+var private = []netip.Prefix{
+	netip.MustParsePrefix("10.0.0.0/8"),
+	netip.MustParsePrefix("172.16.0.0/12"),
+	netip.MustParsePrefix("192.168.0.0/16"),
+	netip.MustParsePrefix("fc00::/7"),
+}
+
+// wholly says whether a network lies wholly inside one of the private ranges.
+func wholly(p netip.Prefix) bool {
+	for _, r := range private {
+		if p.Bits() >= r.Bits() && r.Contains(p.Addr()) {
+			return true
+		}
+	}
+	return false
+}
+
+// ipRoute is one route as `ip -j route show default` answers it.
+type ipRoute struct {
+	Dev string `json:"dev"`
+}
+
+// ipLink is one link as `ip -j addr show` answers it.
+type ipLink struct {
+	Name     string `json:"ifname"`
+	AddrInfo []struct {
+		Family    string `json:"family"`
+		Local     string `json:"local"`
+		Prefixlen int    `json:"prefixlen"`
+		Scope     string `json:"scope"`
+	} `json:"addr_info"`
+}
+
+// LocalNetworksFrom is the machine's local networks from what `ip` answered: the links carrying a default
+// route, and their addresses. A network not wholly private, or not global in scope, is left out, and why.
+func LocalNetworksFrom(routes4, routes6, addrs string) ([]string, []string) {
+	uplinks := map[string]bool{}
+	for _, text := range []string{routes4, routes6} {
+		var rs []ipRoute
+		if strings.TrimSpace(text) == "" {
+			continue
+		}
+		if err := json.Unmarshal([]byte(text), &rs); err != nil {
+			continue
+		}
+		for _, r := range rs {
+			if r.Dev != "" {
+				uplinks[r.Dev] = true
+			}
+		}
+	}
+	var links []ipLink
+	if strings.TrimSpace(addrs) != "" {
+		_ = json.Unmarshal([]byte(addrs), &links)
+	}
+	seen := map[string]bool{}
+	var out, left []string
+	for _, l := range links {
+		if !uplinks[l.Name] {
+			continue
+		}
+		for _, a := range l.AddrInfo {
+			if a.Scope != "global" {
+				continue
+			}
+			addr, err := netip.ParseAddr(a.Local)
+			if err != nil {
+				continue
+			}
+			p, err := addr.Prefix(a.Prefixlen)
+			if err != nil {
+				continue
+			}
+			if !wholly(p) {
+				left = append(left, fmt.Sprintf("%s on %s is not wholly inside a private range, so it is not the local network", p, l.Name))
+				continue
+			}
+			if !seen[p.String()] {
+				seen[p.String()] = true
+				out = append(out, p.String())
+			}
+		}
+	}
+	sort.Strings(out)
+	return out, left
+}
+
+// LocalNetworks is this machine's local networks now, read with `ip`, and what was left out or could not
+// be read.
+func (m *Machine) LocalNetworks(ctx context.Context) ([]string, []string) {
+	r4 := m.Run(ctx, "ip", "-j", "-4", "route", "show", "default")
+	r6 := m.Run(ctx, "ip", "-j", "-6", "route", "show", "default")
+	ad := m.Run(ctx, "ip", "-j", "addr", "show")
+	var notes []string
+	if r4.Code != 0 || ad.Code != 0 {
+		notes = append(notes, "this machine's links could not be read with ip: "+firstLine(r4.Err+" "+ad.Err))
+	}
+	nets, left := LocalNetworksFrom(r4.Out, r6.Out, ad.Out)
+	return nets, append(notes, left...)
+}
+
+// nftRule is one rule of `nft -j list ruleset`.
+type nftRule struct {
+	Family string            `json:"family"`
+	Table  string            `json:"table"`
+	Chain  string            `json:"chain"`
+	Expr   []json.RawMessage `json:"expr"`
+}
+
+// nftChain is one chain of `nft -j list ruleset`.
+type nftChain struct {
+	Family string `json:"family"`
+	Table  string `json:"table"`
+	Name   string `json:"name"`
+	Policy string `json:"policy"`
+}
+
+// Admitted says, for each subnet, whether the mesh's filter (table inet mesh, chain input) accepts tcp to
+// the port from all of it, read from `nft -j list ruleset`. A rule counts only when every condition it has
+// is one this reads — the protocol, the destination port and the source address — and its verdict is
+// accept; a rule with any other condition (an interface, a connection state) is left out, so nothing is
+// called admitted that may not be. With no such table, nothing is admitted, and why.
+func Admitted(ruleset string, port int, subnets []string) (map[string]bool, string) {
+	out := map[string]bool{}
+	var doc struct {
+		Nftables []map[string]json.RawMessage `json:"nftables"`
+	}
+	if err := json.Unmarshal([]byte(ruleset), &doc); err != nil {
+		return out, "the packet filter's rules could not be read (nft -j list ruleset): " + err.Error()
+	}
+	var rules []nftRule
+	found := false
+	policy := ""
+	for _, item := range doc.Nftables {
+		if raw, ok := item["chain"]; ok {
+			var c nftChain
+			if json.Unmarshal(raw, &c) == nil && c.Family == "inet" && c.Table == "mesh" && c.Name == "input" {
+				found, policy = true, c.Policy
+			}
+		}
+		if raw, ok := item["rule"]; ok {
+			var r nftRule
+			if json.Unmarshal(raw, &r) == nil && r.Family == "inet" && r.Table == "mesh" && r.Chain == "input" {
+				rules = append(rules, r)
+			}
+		}
+	}
+	if !found {
+		return out, "the mesh's packet filter (table inet mesh, chain input) is not there, so no local network is admitted"
+	}
+	if policy == "accept" {
+		for _, s := range subnets {
+			out[s] = true
+		}
+		return out, ""
+	}
+	for _, r := range rules {
+		sources, ok := admitsPort(r.Expr, port)
+		if !ok {
+			continue
+		}
+		for _, s := range subnets {
+			p, err := netip.ParsePrefix(s)
+			if err != nil {
+				continue
+			}
+			if sources == nil {
+				out[s] = true
+				continue
+			}
+			for _, src := range sources {
+				if src.Bits() <= p.Bits() && src.Contains(p.Addr()) {
+					out[s] = true
+				}
+			}
+		}
+	}
+	return out, ""
+}
+
+// admitsPort reads one rule: whether it accepts tcp to the port, and from which sources (nil: from
+// anywhere). ok is false for a rule that does not accept that port, or that has a condition this does not
+// read.
+func admitsPort(exprs []json.RawMessage, port int) (sources []netip.Prefix, ok bool) {
+	accepts, portMatched, anywhere := false, false, true
+	for _, raw := range exprs {
+		var e map[string]json.RawMessage
+		if json.Unmarshal(raw, &e) != nil {
+			return nil, false
+		}
+		if _, is := e["accept"]; is {
+			accepts = true
+			continue
+		}
+		if _, is := e["counter"]; is {
+			continue
+		}
+		m, is := e["match"]
+		if !is {
+			return nil, false
+		}
+		var match struct {
+			Op    string          `json:"op"`
+			Left  json.RawMessage `json:"left"`
+			Right json.RawMessage `json:"right"`
+		}
+		if json.Unmarshal(m, &match) != nil || (match.Op != "==" && match.Op != "in") {
+			return nil, false
+		}
+		var left struct {
+			Payload *struct {
+				Protocol string `json:"protocol"`
+				Field    string `json:"field"`
+			} `json:"payload"`
+			Meta *struct {
+				Key string `json:"key"`
+			} `json:"meta"`
+		}
+		if json.Unmarshal(match.Left, &left) != nil {
+			return nil, false
+		}
+		switch {
+		case left.Meta != nil && left.Meta.Key == "l4proto":
+			var proto string
+			if json.Unmarshal(match.Right, &proto) != nil || proto != "tcp" {
+				return nil, false
+			}
+		case left.Payload != nil && left.Payload.Protocol == "tcp" && left.Payload.Field == "dport":
+			if !hasPort(match.Right, port) {
+				return nil, false
+			}
+			portMatched = true
+		case left.Payload != nil && (left.Payload.Protocol == "ip" || left.Payload.Protocol == "ip6") && left.Payload.Field == "saddr":
+			anywhere = false
+			sources = append(sources, prefixesOf(match.Right)...)
+		default:
+			return nil, false
+		}
+	}
+	if !accepts || !portMatched {
+		return nil, false
+	}
+	if anywhere {
+		return nil, true
+	}
+	if sources == nil {
+		sources = []netip.Prefix{}
+	}
+	return sources, true
+}
+
+// hasPort reads a match's right side: a number, or a set holding it.
+func hasPort(raw json.RawMessage, port int) bool {
+	var n int
+	if json.Unmarshal(raw, &n) == nil {
+		return n == port
+	}
+	var set struct {
+		Set []json.RawMessage `json:"set"`
+	}
+	if json.Unmarshal(raw, &set) == nil {
+		for _, item := range set.Set {
+			if json.Unmarshal(item, &n) == nil && n == port {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// prefixesOf reads a match's right side as sources: an address, a prefix, or a set of either.
+func prefixesOf(raw json.RawMessage) []netip.Prefix {
+	var s string
+	if json.Unmarshal(raw, &s) == nil {
+		if a, err := netip.ParseAddr(s); err == nil {
+			return []netip.Prefix{netip.PrefixFrom(a, a.BitLen())}
+		}
+		if p, err := netip.ParsePrefix(s); err == nil {
+			return []netip.Prefix{p.Masked()}
+		}
+		return nil
+	}
+	var pre struct {
+		Prefix *struct {
+			Addr string `json:"addr"`
+			Len  int    `json:"len"`
+		} `json:"prefix"`
+		Set []json.RawMessage `json:"set"`
+	}
+	if json.Unmarshal(raw, &pre) != nil {
+		return nil
+	}
+	if pre.Prefix != nil {
+		if a, err := netip.ParseAddr(pre.Prefix.Addr); err == nil {
+			if p, err := a.Prefix(pre.Prefix.Len); err == nil {
+				return []netip.Prefix{p}
+			}
+		}
+		return nil
+	}
+	var out []netip.Prefix
+	for _, item := range pre.Set {
+		out = append(out, prefixesOf(item)...)
+	}
+	return out
+}
+
+// LocalNetworkAdmitted is what the process learns each pass: the machine's local subnets, which of them the
+// filter admits 2049 from, and what it could not learn.
+func (m *Machine) LocalNetworkAdmitted(ctx context.Context) (nets []string, admitted map[string]bool, notes []string) {
+	nets, notes = m.LocalNetworks(ctx)
+	if len(nets) == 0 {
+		return nets, map[string]bool{}, notes
+	}
+	r := m.Run(ctx, "nft", "-j", "list", "ruleset")
+	if r.Code != 0 {
+		return nets, map[string]bool{}, append(notes, "the packet filter's rules could not be read (nft -j list ruleset): "+firstLine(r.Err))
+	}
+	admitted, note := Admitted(r.Out, NFSPort, nets)
+	if note != "" {
+		notes = append(notes, note)
+	}
+	return nets, admitted, notes
+}
+
+// Covered says whether a client a hand-made export names is covered by the mesh's live export of the same
+// path: the same address, or a network inside one the mesh exports to. "*" and a name are never covered.
+func Covered(client string, mine []Grantee) bool {
+	var want netip.Prefix
+	if a, err := netip.ParseAddr(client); err == nil {
+		want = netip.PrefixFrom(a, a.BitLen())
+	} else if p, err := netip.ParsePrefix(client); err == nil {
+		want = p.Masked()
+	} else {
+		return false
+	}
+	for _, g := range mine {
+		var have netip.Prefix
+		if a, err := netip.ParseAddr(g.Address); err == nil {
+			have = netip.PrefixFrom(a, a.BitLen())
+		} else if p, err := netip.ParsePrefix(g.Address); err == nil {
+			have = p.Masked()
+		} else {
+			continue
+		}
+		if have.Bits() <= want.Bits() && have.Contains(want.Addr()) {
+			return true
+		}
+	}
+	return false
+}
+
+// PropertyClients is who a dataset's sharenfs property exports to: every `@network` or address its value
+// names, and "*" for a bare `on` or a value naming nobody, which nothing the mesh exports ever covers.
+func PropertyClients(sharenfs string) []string {
+	v := strings.TrimSpace(sharenfs)
+	if v == "on" || v == "" {
+		return []string{"*"}
+	}
+	var out []string
+	for _, opt := range strings.Split(v, ",") {
+		key, list, ok := strings.Cut(strings.TrimSpace(opt), "=")
+		if key != "rw" && key != "ro" {
+			continue
+		}
+		if !ok {
+			return []string{"*"} // rw or ro alone: to everyone
+		}
+		for _, c := range strings.Split(list, ":") {
+			c = strings.TrimPrefix(strings.TrimSpace(c), "@")
+			if c != "" {
+				out = append(out, c)
+			}
+		}
+	}
+	if len(out) == 0 {
+		return []string{"*"}
+	}
+	return out
+}
@@ -0,0 +1,184 @@
+package main
+
+import (
+	"context"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// Defends novox/hq ADR 0341 clauses 8 to 10: a share granted to local-network is exported to the machine's
+// own private subnets on its uplink, only those the mesh's filter admits 2049 from; a grant the filter does
+// not admit is said and unhealthy; and sharenfs is cleared only once the mesh's export covers every client
+// the property exported to.
+
+const homeNet = "192.168.1.0/24"
+
+// The home server's links, as `ip -j` answers them: the uplink with a private and a public address, the
+// private network's link, and a container bridge.
+const (
+	routes4 = `[{"dst":"default","gateway":"192.168.1.1","dev":"enp6s0"}]`
+	addrs   = `[
+ {"ifname":"lo","addr_info":[{"family":"inet","local":"127.0.0.1","prefixlen":8,"scope":"host"}]},
+ {"ifname":"enp6s0","addr_info":[
+   {"family":"inet","local":"192.168.1.135","prefixlen":24,"scope":"global"},
+   {"family":"inet","local":"198.51.100.7","prefixlen":24,"scope":"global"},
+   {"family":"inet6","local":"fe80::1","prefixlen":64,"scope":"link"}]},
+ {"ifname":"mesh0","addr_info":[{"family":"inet","local":"10.0.0.2","prefixlen":32,"scope":"global"}]},
+ {"ifname":"docker0","addr_info":[{"family":"inet","local":"172.17.0.1","prefixlen":16,"scope":"global"}]}]`
+)
+
+// rulesetAdmitting is the mesh's filter with 2049 admitted from the nodes and, when local is set, from it.
+func rulesetAdmitting(local string) string {
+	src := `{"set":["10.0.0.1","10.0.0.3"]}`
+	if local != "" {
+		addr, bits, _ := strings.Cut(local, "/")
+		src = `{"set":["10.0.0.1","10.0.0.3",{"prefix":{"addr":"` + addr + `","len":` + bits + `}}]}`
+	}
+	return `{"nftables":[{"metainfo":{"version":"1.1"}},
+ {"table":{"family":"inet","name":"mesh"}},
+ {"chain":{"family":"inet","table":"mesh","name":"input","type":"filter","hook":"input","prio":0,"policy":"drop"}},
+ {"rule":{"family":"inet","table":"mesh","chain":"input","expr":[{"match":{"op":"!=","left":{"meta":{"key":"iifname"}},"right":{"set":["enp6s0","mesh0"]}}},{"accept":null}]}},
+ {"rule":{"family":"inet","table":"mesh","chain":"input","expr":[{"match":{"op":"==","left":{"payload":{"protocol":"ip","field":"saddr"}},"right":` + src + `}},{"match":{"op":"==","left":{"payload":{"protocol":"tcp","field":"dport"}},"right":2049}},{"accept":null}]}},
+ {"rule":{"family":"inet","table":"mesh","chain":"input","expr":[{"match":{"op":"==","left":{"payload":{"protocol":"tcp","field":"dport"}},"right":445}},{"accept":null}]}}]}`
+}
+
+func (f *fake) homeLinks(ruleset string) {
+	f.answers["ip -j -4 route show default"] = Ran{Out: routes4}
+	f.answers["ip -j -6 route show default"] = Ran{Out: "[]"}
+	f.answers["ip -j addr show"] = Ran{Out: addrs}
+	f.answers["nft -j list ruleset"] = Ran{Out: ruleset}
+}
+
+func TestTheLocalNetworkIsTheUplinksPrivateSubnetsOnly(t *testing.T) {
+	nets, left := LocalNetworksFrom(routes4, "", addrs)
+	if !reflect.DeepEqual(nets, []string{homeNet}) {
+		t.Errorf("local networks %v; the uplink's private subnet alone, never the public one, the mesh's link or a bridge", nets)
+	}
+	if len(left) != 1 || !strings.Contains(left[0], "198.51.100.0/24") {
+		t.Errorf("the public subnet is not said as left out: %v", left)
+	}
+	if nets, _ := LocalNetworksFrom("", "", addrs); len(nets) != 0 {
+		t.Errorf("with no default route there is no uplink and no local network: %v", nets)
+	}
+}
+
+func TestAdmittedReadsThePortsOwnRuleOnly(t *testing.T) {
+	got, note := Admitted(rulesetAdmitting(homeNet), 2049, []string{homeNet})
+	if note != "" || !got[homeNet] {
+		t.Errorf("2049 admitted from the home network is not read as admitted: %v %q", got, note)
+	}
+	got, _ = Admitted(rulesetAdmitting(""), 2049, []string{homeNet})
+	if got[homeNet] {
+		t.Error("2049 admitted from the nodes only is read as admitted from the home network")
+	}
+	// A rule open to every source on 445 says nothing of 2049, and the interface rule is not read as one.
+	if got, _ := Admitted(rulesetAdmitting(""), 445, []string{homeNet}); !got[homeNet] {
+		t.Error("a port open from anywhere is not admitted")
+	}
+	if got, note := Admitted(`{"nftables":[]}`, 2049, []string{homeNet}); got[homeNet] || note == "" {
+		t.Errorf("with no mesh filter a subnet is admitted, or nothing is said: %v %q", got, note)
+	}
+}
+
+// grantedLocal is the library granted to ws and to the local network, ws wanting it.
+func grantedLocal(f *fake, grant string) {
+	f.mountinfo("/", "/srv/library")
+	f.dir("/srv/library")
+	f.file(ConfigFile, grantsConfig("library=/srv/library", "library=ws:rw,"+grant))
+	f.serve("library")
+	f.kernelReads()
+}
+
+func TestAShareGrantedToTheLocalNetworkGoesToItsSubnetWhenTheFilterAdmitsIt(t *testing.T) {
+	f := newFake(t)
+	grantedLocal(f, "local-network:ro")
+	f.homeLinks(rulesetAdmitting(homeNet))
+	s := f.machine().Pass(context.Background(), nil)
+	text := f.read(ExportFile)
+	if !strings.Contains(text, " "+homeNet+"(ro,mp,sync,secure,no_subtree_check,all_squash,") {
+		t.Errorf("the library is not exported read-only to the home network, squashed:\n%s", text)
+	}
+	if strings.Contains(text, "198.51.100") || strings.Contains(text, "172.17") {
+		t.Errorf("a public subnet or a bridge is exported to:\n%s", text)
+	}
+	if len(s.Unreached) != 0 || !s.Shares[0].Live || len(s.Shares[0].To) != 2 {
+		t.Errorf("status: %+v", s)
+	}
+	if h := f.machine().Health(); !h.Healthy || !strings.Contains(h.Why, "local-network ("+homeNet+", ro)") {
+		t.Errorf("health: %+v", h)
+	}
+}
+
+func TestAGrantTheFilterDoesNotAdmitIsNotExportedAndIsUnhealthy(t *testing.T) {
+	f := newFake(t)
+	grantedLocal(f, "local-network:rw")
+	f.homeLinks(rulesetAdmitting(""))
+	s := f.machine().Pass(context.Background(), nil)
+	if strings.Contains(f.read(ExportFile), homeNet) {
+		t.Errorf("the library is exported to a subnet the filter drops:\n%s", f.read(ExportFile))
+	}
+	if len(s.Unreached) != 1 || !strings.Contains(s.Unreached[0], "reach local-network") {
+		t.Errorf("the unreached grant is not said with its act: %v", s.Unreached)
+	}
+	if h := f.machine().Health(); h.Healthy || !strings.Contains(h.Why, "does not admit 2049/tcp") {
+		t.Errorf("health: %+v", h)
+	}
+}
+
+func TestWithNoPrivateNetworkOnTheUplinkALocalGrantGoesNowhereAndIsSaid(t *testing.T) {
+	f := newFake(t)
+	grantedLocal(f, "local-network:rw")
+	s := f.machine().Pass(context.Background(), nil) // ip answers nothing
+	if strings.Contains(f.read(ExportFile), "192.168") {
+		t.Errorf("exported to a local network that was not found:\n%s", f.read(ExportFile))
+	}
+	if !strings.Contains(strings.Join(s.Said, "\n"), "reports no private network on its uplink") {
+		t.Errorf("not said: %v", s.Said)
+	}
+}
+
+func TestAdoptWaitsUntilTheLocalNetworkExportCoversTheProperty(t *testing.T) {
+	f := newFake(t)
+	f.uid = 1000
+	zfsWith(f, "rw=@"+homeNet)
+	f.file("/etc/exports.d/zfs.exports", "/srv/library "+homeNet+"(sec=sys,rw,no_subtree_check,mountpoint)\n")
+	grantedLocal(f, "local-network:rw")
+	f.homeLinks(rulesetAdmitting("")) // the filter does not admit the home network yet
+	f.machine().Pass(context.Background(), nil)
+	if _, err := f.machine().Adopt("/srv/library", false, ""); err == nil || !strings.Contains(err.Error(), "does not cover") {
+		t.Fatalf("adopt while the home network is not covered: %v", err)
+	}
+	f.homeLinks(rulesetAdmitting(homeNet))
+	f.machine().Pass(context.Background(), nil)
+	f.ran = nil
+	dry, err := f.machine().Adopt("/srv/library", false, "")
+	if err != nil || !strings.Contains(dry.Said, "would set sharenfs=off") {
+		t.Fatalf("dry run once covered: %+v %v", dry, err)
+	}
+	for _, r := range f.ran {
+		if strings.Contains(r, "zfs set") {
+			t.Fatalf("a dry run changed something: %v", f.ran)
+		}
+	}
+}
+
+func TestPropertyClientsAndCovered(t *testing.T) {
+	for v, want := range map[string]string{
+		"rw=@192.168.1.0/24":           "192.168.1.0/24",
+		"rw=@192.168.1.0/24:@10.0.0.3": "192.168.1.0/24 10.0.0.3",
+		"on":                           "*",
+		"rw,no_root_squash":            "*",
+		"sec=sys,ro=@10.0.0.3":         "10.0.0.3",
+	} {
+		if got := strings.Join(PropertyClients(v), " "); got != want {
+			t.Errorf("PropertyClients(%q) = %q, not %q", v, got, want)
+		}
+	}
+	mine := []Grantee{{Node: "ws", Address: "10.0.0.3"}, {Node: LocalNetwork, Address: homeNet}}
+	for client, want := range map[string]bool{"10.0.0.3": true, homeNet: true, "192.168.1.7": true, "192.168.0.0/16": false, "*": false, "10.0.0.4": false} {
+		if Covered(client, mine) != want {
+			t.Errorf("Covered(%q) is not %v", client, want)
+		}
+	}
+}
@@ -259,7 +259,9 @@ func TestAdoptIsADryRunWithoutConfirmAndRefusesWhileTheMeshExportIsNotLive(t *te
 	f := newFake(t)
 	f.uid = 1000
 	f.dir("/srv/library")
-	zfsWith(f, "rw=@192.0.2.0/24")
+	// A property the mesh's export covers once live: the one node. One to the home network is
+	// localnet_test.go's.
+	zfsWith(f, "rw=@"+wsAddress)
 	f.file(ConfigFile, config("library=/srv/library"))
 	f.serve("library")
 	// The kernel has not read the mesh's file: no exportfs effect.
@@ -31,6 +31,11 @@ type Status struct {
 	// Warnings make the module no less healthy but are said in its health: what it could not learn, and
 	// how old what it relies on is.
 	Warnings []string `json:"warnings,omitempty"`
+	// Local is the machine's local subnets this pass (ADR 0341): what a grant to local-network may reach.
+	Local []string `json:"local_networks,omitempty"`
+	// Unreached is each grant to the local network the packet filter does not admit: not exported, and the
+	// module is unhealthy until it is.
+	Unreached []string `json:"unreached,omitempty"`
 	// Reloaded is when the process last had the kernel read the export files again, and why.
 	Reloaded    *time.Time `json:"reloaded,omitempty"`
 	ReloadWhy   string     `json:"reload_why,omitempty"`
@@ -61,8 +66,17 @@ func (m *Machine) Pass(ctx context.Context, last *Status) Status {
 	if _, note := m.Backup(); note != "" {
 		s.Warnings = append(s.Warnings, note)
 	}
+	if grantsLocal(c) {
+		nets, admitted, notes := m.LocalNetworkAdmitted(ctx)
+		c.Local = &Local{Nets: nets, Admitted: admitted}
+		s.Local = nets
+		s.Said = append(s.Said, notes...)
+	}
 	m.setWalk(ctx)
 	exports, refused, said := m.Judge(c, roster, wants)
+	if c.Local != nil {
+		s.Unreached = c.Local.Unreached
+	}
 	m.setWalk(nil)
 	if ctx.Err() != nil {
 		// Stopping: write nothing and reload nothing, so Stopped starts at once.
@@ -100,7 +114,7 @@ func (m *Machine) Pass(ctx context.Context, last *Status) Status {
 		}
 	}
 	if reload == "" {
-		if stray := Stray(live, mine, foreign, c.Range); len(stray) > 0 {
+		if stray := Stray(live, mine, foreign, c.Range, s.Local); len(stray) > 0 {
 			reload = fmt.Sprintf("the kernel exports %s to %s, which the export file no longer carries", stray[0].Path, stray[0].Client)
 		}
 	}
@@ -116,7 +130,7 @@ func (m *Machine) Pass(ctx context.Context, last *Status) Status {
 	if note != "" && len(exports) > 0 {
 		s.Problems = append(s.Problems, note)
 	}
-	for _, e := range Stray(live, mine, foreign, c.Range) {
+	for _, e := range Stray(live, mine, foreign, c.Range, s.Local) {
 		s.Problems = append(s.Problems, fmt.Sprintf("the kernel still exports %s to %s, which the module's export file "+
 			"no longer carries: a reload has to take it away (exportfs -ra as root)", e.Path, e.Client))
 	}
@@ -256,21 +270,34 @@ func loud(what string) {
 }

 // Stray is what the kernel exports that is the module's and that its file no longer carries: an entry to a
-// client inside the private network's range — the only clients the module ever exports to — that neither
-// the module's file nor any other export file (/etc/exports, ZFS's own) has. What another file exports is
-// not the module's, whatever its client.
-func Stray(live, mine, foreign []Entry, rng string) []Entry {
+// client inside the private network's range, or one of the machine's local subnets — the only clients the
+// module ever exports to — that neither the module's file nor any other export file (/etc/exports, ZFS's
+// own) has. What another file exports is not the module's, whatever its client.
+func Stray(live, mine, foreign []Entry, rng string, local []string) []Entry {
 	prefix, err := netip.ParsePrefix(rng)
 	if err != nil {
 		return nil
 	}
+	ours := []netip.Prefix{prefix}
+	for _, n := range local {
+		if p, err := netip.ParsePrefix(n); err == nil {
+			ours = append(ours, p.Masked())
+		}
+	}
 	has := map[string]bool{}
 	for _, e := range append(append([]Entry{}, mine...), foreign...) {
 		has[path.Clean(e.Path)+" "+e.Client] = true
 	}
 	var out []Entry
 	for _, e := range live {
-		if has[path.Clean(e.Path)+" "+e.Client] || !insideRange(e.Client, prefix) {
+		if has[path.Clean(e.Path)+" "+e.Client] {
+			continue
+		}
+		inside := false
+		for _, p := range ours {
+			inside = inside || insideRange(e.Client, p)
+		}
+		if !inside {
 			continue
 		}
 		out = append(out, e)
@@ -288,3 +315,14 @@ func insideRange(client string, prefix netip.Prefix) bool {
 	}
 	return false
 }
+
+// grantsLocal says whether any share is granted to the local network, so the process looks at the links
+// and the filter only when a grant asks for them.
+func grantsLocal(c Config) bool {
+	for _, nodes := range c.Grants {
+		if _, ok := nodes[LocalNetwork]; ok {
+			return true
+		}
+	}
+	return false
+}
@@ -28,7 +28,8 @@ import (
 // write to WantsFile). The access is the lower of the two: a grant of ro is never widened by a want. The
 // address is the mesh's own, from the roster the mesh renders (RosterFile), never one a consumer gave,
 // and it must lie in the private network's range. A share nobody is granted and wants is exported to
-// nobody. The home network is never named.
+// nobody. The local network is named only by a grant to `local-network`, and then only the subnets the
+// packet filter admits 2049 from (localnet.go, novox/hq ADR 0341).
 //
 // **Never the backups, never root's.** A share is judged at its real path (symlinks resolved). It is
 // refused when it is the machine's root, is not there, is not a folder, is owned by root or root's group
@@ -86,6 +87,17 @@ type Config struct {
 	// Grants is, per share, the nodes this machine lets mount it and with which access.
 	Grants map[string]map[string]string
 	Range  string
+	// Local is the machine's local network as the process found it this pass (localnet.go): nil when it was
+	// not looked at, and a grant to local-network then goes nowhere.
+	Local *Local
+}
+
+// Local is the machine's local subnets, which of them the filter admits 2049 from, and — written by Judge —
+// each local-network grant the filter does not admit.
+type Local struct {
+	Nets      []string
+	Admitted  map[string]bool
+	Unreached []string
 }

 // Want is one share a node's mounts module wants of this machine, as it put it on the bus.
@@ -172,7 +184,8 @@ func ParseShares(value string) ([]Share, []string) {
 }

 // ParseGrants reads the `grants` setting: `share=node:rw|ro[,node:rw|ro]`, entries separated by spaces;
-// `none` grants nothing.
+// `none` grants nothing. `local-network` in a node's place grants the machine's local network
+// (localnet.go).
 func ParseGrants(value string) (map[string]map[string]string, []string) {
 	out := map[string]map[string]string{}
 	seen := map[string]bool{}
@@ -457,8 +470,25 @@ func (m *Machine) Judge(c Config, roster map[string]string, wants map[string][]W
 				e.To = append(e.To, Grantee{Node: node, Address: addr, Access: access})
 			}
 		}
+		if g, ok := granted[LocalNetwork]; ok {
+			switch {
+			case c.Local == nil || len(c.Local.Nets) == 0:
+				said = append(said, fmt.Sprintf("%s is granted to the local network, and this machine reports no private network on its uplink, so it is exported to no local network", s.Name))
+			default:
+				for _, n := range c.Local.Nets {
+					if !c.Local.Admitted[n] {
+						c.Local.Unreached = append(c.Local.Unreached, fmt.Sprintf("the share %s is granted to the local network %s, and the packet filter does not admit %d/tcp from it, so it is not exported there: bind nfs-server's %d with the reach local-network (novox/hq ADR 0340, ADR 0341)", s.Name, n, NFSPort, NFSPort))
+						continue
+					}
+					e.To = append(e.To, Grantee{Node: LocalNetwork, Address: n, Access: lower(g, s.Access)})
+				}
+			}
+		}
 		grantedNodes := make([]string, 0, len(granted))
 		for n := range granted {
+			if n == LocalNetwork {
+				continue
+			}
 			if !wanting[n] {
 				grantedNodes = append(grantedNodes, n)
 			}
@@ -474,7 +504,7 @@ func (m *Machine) Judge(c Config, roster map[string]string, wants map[string][]W
 		e.Clients = strings.Join(addrs, ",")
 		e.Line = ExportLine(e)
 		if len(e.To) == 0 {
-			said = append(said, fmt.Sprintf("%s is exported to no node: none is both granted it and wants it", s.Name))
+			said = append(said, fmt.Sprintf("%s is exported to no node: none is both granted it and wants it, and no local network is granted and admitted", s.Name))
 		}
 		out = append(out, e)
 	}
@@ -517,6 +547,7 @@ func ExportFileText(exports []Exported) string {
 	b.WriteString("# Written by the mesh's module nfs-server (novox/hq ADR 0263). Rendered by the module's own process\n")
 	b.WriteString("# from its assignment's `shares` and `grants` and the nodes that want each share; edit the settings,\n")
 	b.WriteString("# never this file. One share per folder, to each granted and wanting node's private address only,\n")
+	b.WriteString("# and to a local subnet only when local-network is granted and the filter admits 2049 from it;\n")
 	b.WriteString("# every client squashed to the folder's owner.\n")
 	for _, e := range exports {
 		if e.Line == "" {
@@ -127,7 +127,7 @@ func (m *Machine) Exports() ExportsAnswer {
 		}
 		a.Notes = append(a.Notes, st.Problems...)
 		a.Notes = append(a.Notes, st.Warnings...)
-		a.Unmatched = st.Said
+		a.Unmatched = append(append([]string{}, st.Said...), st.Unreached...)
 	}
 	entries, sets, notes := m.Foreign()
 	a.Notes = append(a.Notes, notes...)
@@ -380,6 +380,31 @@ func (m *Machine) Adopt(p string, confirm bool, why string) (AdoptAnswer, error)
 	if lnote != "" || !SharedLive(live, *mine) {
 		return a, fmt.Errorf("the mesh's export of %s to %s is not live in the kernel yet, so taking over would unexport it; wait for the module's process, or call reload", p, grantees(mine.To))
 	}
+	// Every client the property exported to must be covered by the mesh's live export, so no client loses
+	// the folder in the take-over (novox/hq ADR 0341 clause 10): for a property to the home network, the
+	// module's local-network export of it. Who the property exports to is read from its value and from the
+	// file ZFS writes for it.
+	clients := PropertyClients(ds.ShareNFS)
+	entries, _, _ := m.Foreign()
+	for _, e := range entries {
+		if strings.Contains(e.From, "zfs") && path.Clean(e.Path) == p {
+			clients = append(clients, e.Client)
+		}
+	}
+	var uncovered []string
+	seenClient := map[string]bool{}
+	for _, c := range clients {
+		if seenClient[c] {
+			continue
+		}
+		seenClient[c] = true
+		if !Covered(c, mine.To) {
+			uncovered = append(uncovered, c)
+		}
+	}
+	if len(uncovered) > 0 {
+		return a, fmt.Errorf("the dataset's sharenfs exports %s to %s, which the mesh's export (to %s) does not cover, so taking over would unexport it for them: grant the share to local-network (and bind %d with the reach local-network) until the mesh's export covers them, or have a person decide they lose it", p, strings.Join(uncovered, ", "), grantees(mine.To), NFSPort)
+	}
 	plan := fmt.Sprintf("set sharenfs=off on the dataset %s (now %q) and run exportfs -ra; %s stays exported as the share %s to %s, every client as %d:%d",
 		ds.Name, ds.ShareNFS, p, mine.Name, grantees(mine.To), mine.UID, mine.GID)
 	if !confirm {
@@ -428,6 +453,9 @@ func (m *Machine) Health() Health {
 	for _, r := range st.Refused {
 		found = append(found, r.Why)
 	}
+	for _, u := range st.Unreached {
+		found = append(found, sentence(u))
+	}
 	if st.ReloadError != "" {
 		found = append(found, sentence("the kernel could not read the export files again: "+st.ReloadError))
 	}
@@ -55,7 +55,7 @@
    "grants": {
      "kind": "preference",
      "default": "none",
-      "why": "which nodes may mount which share, and how, is this machine's to say (hq ADR 0263, review of mesh-catalog #136): share=node:rw|ro[,node:rw|ro], entries separated by spaces; none exports to no node, whatever a node wants"
+      "why": "which nodes may mount which share, and how, is this machine's to say (hq ADR 0263, review of mesh-catalog #136): share=node:rw|ro[,node:rw|ro], entries separated by spaces; none exports to no node, whatever a node wants. local-network in a node's place grants this machine's local network, the private subnets on its uplink (hq ADR 0341)"
    }
  },
  "facts": {
@@ -74,7 +74,7 @@
      "protocol": "tcp",
      "from": "mesh",
      "fixed": true,
-      "why": "the shares, to the mesh's machines only (hq ADR 0263): NFS version 4 alone, which needs no other port, and never the home network, where a device that is not a node could claim any user id"
+      "why": "the shares, to the mesh's machines (hq ADR 0263): NFS version 4 alone, which needs no other port. A machine whose grants name local-network binds this port with the reach local-network (hq ADR 0340, ADR 0341), and the module exports to a local subnet only while the filter admits it from there"
    }
  ],
  "resources": [
@@ -154,7 +154,7 @@
      "type": "file",
      "path": "/etc/nfs-server/shares.conf",
      "mode": "0644",
-      "content": "# Written by the mesh (module nfs-server, novox/hq ADR 0263) from this machine's assignment.\n# Replaced on every push; change the `shares` setting, never this file.\n#\n# The shares: name=folder, or name=folder:ro, one share per folder. The grants: share=node:rw|ro[,…],\n# which nodes may mount each and how. The module's process exports a share to a node's private address\n# only when it is granted here and that node's mounts module wants it, every client mapped to the\n# folder's owner, and only to addresses inside the range below.\nshares=${setting:shares}\ngrants=${setting:grants}\nrange=${machine:mesh-range}\n"
+      "content": "# Written by the mesh (module nfs-server, novox/hq ADR 0263) from this machine's assignment.\n# Replaced on every push; change the `shares` setting, never this file.\n#\n# The shares: name=folder, or name=folder:ro, one share per folder. The grants: share=node:rw|ro[,…],\n# which nodes may mount each and how; local-network in a node's place grants this machine's local\n# network (novox/hq ADR 0341). The module's process exports a share to a node's private address only\n# when it is granted here and that node's mounts module wants it, and to a local subnet only when the\n# packet filter admits 2049 from it; every client mapped to the folder's owner.\nshares=${setting:shares}\ngrants=${setting:grants}\nrange=${machine:mesh-range}\n"
    }
  ],
  "build": {
@@ -0,0 +1,288 @@
+package main
+
+import (
+	"fmt"
+	"path"
+	"sort"
+	"strings"
+)
+
+// The shares and logins, from the assignment, the hand-written configuration as found, and the module's
+// rendering (novox/hq ADR 0341 clauses 2 to 4).
+//
+// **One share per folder, every client as its owner.** A share is a name and a path in the `shares`
+// setting (`library=/srv/library`, `:ro` for read-only). It is served with `force user` and `force group`
+// read from the real folder's owner, never written as numbers in a setting, so a file written by any client
+// lands owned by the folder's owner. The refusals are ADR 0263's: the machine's root, a folder not there or
+// not a folder, a folder owned by root or root's group, and a folder inside or holding a backup repository.
+//
+// **SMB 2.1 and later, on 445 alone.** NetBIOS is off (`disable netbios`, `smb ports = 445`), so 137, 138 and
+// 139 are never served; the minimum protocol is SMB2_10. No guest: `map to guest = never`.
+
+// Share is one share the operator asked for.
+type Share struct {
+	Name   string `json:"name"`
+	Path   string `json:"path"`
+	Access string `json:"access"`
+}
+
+// Config is what the mesh rendered from the assignment.
+type Config struct {
+	Shares []Share
+	Users  []string
+	// Passwords is the folder the mesh places the logins' secrets in (smb-password-<user>.secret).
+	Passwords string
+}
+
+// ParseConfig reads the config file: `shares=`, `users=` and `passwords=` lines.
+func ParseConfig(text string) (Config, []string) {
+	var c Config
+	var problems []string
+	for _, line := range strings.Split(text, "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		key, value, ok := strings.Cut(line, "=")
+		if !ok {
+			problems = append(problems, fmt.Sprintf("the line %q of %s says nothing this module reads", line, ConfigFile))
+			continue
+		}
+		switch strings.TrimSpace(key) {
+		case "shares":
+			shares, bad := ParseShares(value)
+			c.Shares, problems = shares, append(problems, bad...)
+		case "users":
+			users, bad := ParseUsers(value)
+			c.Users, problems = users, append(problems, bad...)
+		case "passwords":
+			c.Passwords = strings.TrimSpace(value)
+		default:
+			problems = append(problems, fmt.Sprintf("%s names %q, which this module does not read", ConfigFile, key))
+		}
+	}
+	return c, problems
+}
+
+// ParseShares reads the `shares` setting: `name=path` or `name=path:ro`, separated by spaces.
+func ParseShares(value string) ([]Share, []string) {
+	var shares []Share
+	var problems []string
+	seen := map[string]bool{}
+	for _, item := range strings.Fields(value) {
+		if item == "none" {
+			continue
+		}
+		name, p, ok := strings.Cut(item, "=")
+		if !ok || name == "" || p == "" {
+			problems = append(problems, fmt.Sprintf("the share %q is not name=path", item))
+			continue
+		}
+		if !validName(name) {
+			problems = append(problems, fmt.Sprintf("the share name %q is not lower-case letters, digits and dashes", name))
+			continue
+		}
+		if seen[name] {
+			problems = append(problems, fmt.Sprintf("the share %q is named twice", name))
+			continue
+		}
+		seen[name] = true
+		s := Share{Name: name, Path: p, Access: "rw"}
+		if strings.HasSuffix(p, ":ro") {
+			s.Path, s.Access = strings.TrimSuffix(p, ":ro"), "ro"
+		} else if strings.HasSuffix(p, ":rw") {
+			s.Path = strings.TrimSuffix(p, ":rw")
+		}
+		shares = append(shares, s)
+	}
+	sort.Slice(shares, func(i, j int) bool { return shares[i].Name < shares[j].Name })
+	return shares, problems
+}
+
+// ParseUsers reads the `users` setting: login names separated by spaces; `none` is none.
+func ParseUsers(value string) ([]string, []string) {
+	var out, problems []string
+	seen := map[string]bool{}
+	for _, u := range strings.Fields(value) {
+		if u == "none" {
+			continue
+		}
+		if !validName(u) {
+			problems = append(problems, fmt.Sprintf("the login %q is not lower-case letters, digits and dashes", u))
+			continue
+		}
+		if !seen[u] {
+			seen[u] = true
+			out = append(out, u)
+		}
+	}
+	sort.Strings(out)
+	return out, problems
+}
+
+func validName(n string) bool {
+	if n == "" || n[0] == '-' {
+		return false
+	}
+	for _, r := range n {
+		if !(r >= 'a' && r <= 'z' || r >= '0' && r <= '9' || r == '-') {
+			return false
+		}
+	}
+	return true
+}
+
+// Section is one section of a Samba configuration: its name and its parameters, keys lower-cased with their
+// spaces folded.
+type Section struct {
+	Name   string            `json:"name"`
+	Params map[string]string `json:"params"`
+}
+
+// ParseSamba reads a Samba configuration's sections, in order. Comments (# and ;) and continuation lines are
+// handled as Samba does.
+func ParseSamba(text string) []Section {
+	var out []Section
+	var cur *Section
+	text = strings.ReplaceAll(text, "\\\n", " ")
+	for _, line := range strings.Split(text, "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" || line[0] == '#' || line[0] == ';' {
+			continue
+		}
+		if strings.HasPrefix(line, "[") && strings.HasSuffix(line, "]") {
+			out = append(out, Section{Name: strings.TrimSpace(line[1 : len(line)-1]), Params: map[string]string{}})
+			cur = &out[len(out)-1]
+			continue
+		}
+		k, v, ok := strings.Cut(line, "=")
+		if !ok || cur == nil {
+			continue
+		}
+		cur.Params[foldKey(k)] = strings.TrimSpace(v)
+	}
+	return out
+}
+
+func foldKey(k string) string { return strings.Join(strings.Fields(strings.ToLower(k)), " ") }
+
+// special are the sections that are not shares.
+var special = map[string]bool{"global": true, "homes": true, "printers": true, "print$": true}
+
+// HandShare is one share of the hand-written configuration, and the setting's share that takes its place.
+type HandShare struct {
+	Name string `json:"name"`
+	Path string `json:"path"`
+	// ValidUsers is who may log in to it, as the hand-written file said.
+	ValidUsers string `json:"valid_users,omitempty"`
+	ReadOnly   bool   `json:"read_only"`
+	// Counterpart is the setting's share of the same name and folder; empty when the settings name none.
+	Counterpart string `json:"counterpart,omitempty"`
+	Why         string `json:"why,omitempty"`
+}
+
+// HandShares are the hand-written configuration's shares, each matched to the setting's share of the same
+// name serving the same folder (a trailing slash aside).
+func HandShares(sections []Section, shares []Share) []HandShare {
+	byName := map[string]Share{}
+	for _, s := range shares {
+		byName[strings.ToLower(s.Name)] = s
+	}
+	var out []HandShare
+	for _, sec := range sections {
+		if special[strings.ToLower(sec.Name)] {
+			continue
+		}
+		h := HandShare{Name: sec.Name, Path: sec.Params["path"], ValidUsers: sec.Params["valid users"], ReadOnly: readOnly(sec.Params)}
+		s, ok := byName[strings.ToLower(sec.Name)]
+		switch {
+		case !ok:
+			h.Why = fmt.Sprintf("the setting shares names no share %s", sec.Name)
+		case cleanPath(s.Path) != cleanPath(h.Path):
+			h.Why = fmt.Sprintf("the setting's share %s serves %s, and the hand-written one serves %s", s.Name, s.Path, h.Path)
+		default:
+			h.Counterpart = s.Name
+		}
+		out = append(out, h)
+	}
+	return out
+}
+
+func cleanPath(p string) string {
+	if p == "" {
+		return ""
+	}
+	return path.Clean(p)
+}
+
+// readOnly is Samba's reading of a share's access: read only = yes unless writable/writeable/write ok says
+// otherwise, as Samba defaults it.
+func readOnly(p map[string]string) bool {
+	yes := func(v string) bool {
+		v = strings.ToLower(strings.TrimSpace(v))
+		return v == "yes" || v == "true" || v == "1"
+	}
+	if v, ok := p["read only"]; ok {
+		return yes(v)
+	}
+	for _, k := range []string{"writable", "writeable", "write ok"} {
+		if v, ok := p[k]; ok {
+			return !yes(v)
+		}
+	}
+	return true
+}
+
+// Served is a share as the module serves it.
+type Served struct {
+	Name   string   `json:"name"`
+	Path   string   `json:"path"`
+	Access string   `json:"access"`
+	UID    int      `json:"uid"`
+	GID    int      `json:"gid"`
+	User   string   `json:"force_user"`
+	Group  string   `json:"force_group"`
+	Users  []string `json:"valid_users"`
+	// Live is whether Samba serves it now, as testparm reads the configuration in use.
+	Live bool `json:"live"`
+}
+
+// Refused is a share that is not served, and why.
+type Refused struct {
+	Name string `json:"name"`
+	Path string `json:"path"`
+	Why  string `json:"why"`
+}
+
+// Render is Samba's whole configuration from the shares the module serves.
+func Render(shares []Served) string {
+	var b strings.Builder
+	b.WriteString(Marker + "\n")
+	b.WriteString("# Rendered by the module's own process from its assignment's settings shares and users; change the\n")
+	b.WriteString("# settings, never this file. The hand-written configuration it replaced is kept beside it, dated.\n")
+	b.WriteString("[global]\n")
+	for _, kv := range [][2]string{
+		{"server role", "standalone server"},
+		{"security", "user"},
+		{"passdb backend", "tdbsam"},
+		{"map to guest", "never"},
+		{"server min protocol", "SMB2_10"},
+		{"disable netbios", "yes"},
+		{"smb ports", "445"},
+		{"load printers", "no"},
+		{"printing", "bsd"},
+		{"printcap name", "/dev/null"},
+		{"disable spoolss", "yes"},
+	} {
+		fmt.Fprintf(&b, "   %s = %s\n", kv[0], kv[1])
+	}
+	for _, s := range shares {
+		ro := "no"
+		if s.Access == "ro" {
+			ro = "yes"
+		}
+		fmt.Fprintf(&b, "\n[%s]\n   path = %s\n   read only = %s\n   browseable = yes\n   guest ok = no\n", s.Name, s.Path, ro)
+		fmt.Fprintf(&b, "   valid users = %s\n   force user = %s\n   force group = %s\n", strings.Join(s.Users, " "), s.User, s.Group)
+	}
+	return b.String()
+}
@@ -0,0 +1,279 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"os/exec"
+	"path"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"syscall"
+	"time"
+)
+
+// The machine as the module sees it (novox/hq ADR 0341).
+//
+// **Two processes, two accounts.** The tools run as the operator account (ADR 0175 §4) and read; what only
+// root may do (`smbcontrol`, `smbstatus`) goes through `sudo -n`. The module's long-running process runs as
+// root: it judges the shares, and once a person adopted the configuration it writes Samba's configuration
+// file whole, sets the logins' passwords from their secrets, and stops NetBIOS.
+//
+// **It writes its own files and nothing else.** Samba's configuration (only after adoption), its dated copy
+// of the hand-written one, the status, and the record of which passwords it set. Nothing here can create,
+// chown, chmod or remove anything under a shared path: the machine offers no such call, and Write refuses
+// every path but the module's (novox/hq ADR 0051).
+
+// The module's files on the machine.
+const (
+	// ConfigFile is what the mesh renders from the assignment: the shares, the logins, where the secrets are.
+	ConfigFile = "/etc/smb-server/shares.conf"
+	// SambaConf is Samba's configuration: the hand-written one until adoption, the module's after.
+	SambaConf = "/etc/samba/smb.conf"
+	// Candidate is the module's rendering, checked with testparm before it takes SambaConf's place.
+	Candidate = "/etc/samba/smb.conf.mesh-new"
+	// HandCopyPrefix begins the dated copy of the hand-written configuration kept at adoption.
+	HandCopyPrefix = "/etc/samba/smb.conf.hand-written-"
+	// StatusFile is the process's last look, for the tools.
+	StatusFile = "/run/smb-server/status.json"
+	// AdoptDir is where the adopt verb, as the operator account, leaves a person's word for the process.
+	AdoptDir = "/var/lib/smb-server/adopt"
+	// AdoptFile is that word: when, and why.
+	AdoptFile = AdoptDir + "/adopt.json"
+	// SetFile is which password the process last set for each login, as a digest, readable by root only.
+	SetFile = "/var/lib/smb-server/passwords.json"
+	// Unit is Samba's service; NMBUnit its NetBIOS name service, stopped once the module takes over.
+	Unit    = "smb.service"
+	NMBUnit = "nmb.service"
+	// Port is the one port SMB is served on.
+	Port = 445
+)
+
+// Marker is the first line of a configuration the module wrote: how it tells its own from a person's.
+const Marker = "# Written by the mesh (module smb-server, novox/hq ADR 0341)."
+
+// writable is every file the module may write.
+func writable(p string) bool {
+	switch p {
+	case SambaConf, Candidate, StatusFile, AdoptFile, SetFile:
+		return true
+	}
+	return strings.HasPrefix(p, HandCopyPrefix) && !strings.Contains(strings.TrimPrefix(p, HandCopyPrefix), "/")
+}
+
+// CommandTimeout bounds every command.
+const CommandTimeout = 20 * time.Second
+
+// Ran is what one command did.
+type Ran struct {
+	Out  string
+	Err  string
+	Code int
+}
+
+// Runner runs one command, with what it reads on stdin; injected, so everything is tested over recorded
+// answers.
+type Runner func(ctx context.Context, input, name string, args ...string) Ran
+
+// ExecRunner runs a command on the machine, bounded by CommandTimeout.
+func ExecRunner(ctx context.Context, input, name string, args ...string) Ran {
+	ctx, cancel := context.WithTimeout(ctx, CommandTimeout)
+	defer cancel()
+	cmd := exec.CommandContext(ctx, name, args...)
+	if input != "" {
+		cmd.Stdin = strings.NewReader(input)
+	}
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout, cmd.Stderr = &stdout, &stderr
+	err := cmd.Run()
+	r := Ran{Out: stdout.String(), Err: strings.TrimSpace(stderr.String())}
+	if err != nil {
+		var exit *exec.ExitError
+		if errors.As(err, &exit) {
+			r.Code = exit.ExitCode()
+		} else {
+			r.Code = -1
+			if r.Err == "" {
+				r.Err = err.Error()
+			}
+		}
+	}
+	return r
+}
+
+// Owner is who owns a path, and whether it is a directory.
+type Owner struct {
+	UID, GID int
+	Dir      bool
+}
+
+// Machine is a filesystem root (the real one, or a test's tree), a runner, who this process is, and a clock.
+type Machine struct {
+	Root string
+	Run  Runner
+	UID  int
+	Now  func() time.Time
+	// ownerOf reads a file's owner from its inode; tests set it so their folders stand for an owner.
+	ownerOf func(info os.FileInfo) (uid, gid int)
+}
+
+// Here is this machine.
+func Here() *Machine {
+	return &Machine{Root: "/", Run: ExecRunner, UID: os.Getuid(), Now: time.Now, ownerOf: inodeOwner}
+}
+
+func (m *Machine) at(p string) string { return filepath.Join(m.Root, p) }
+
+// Read reads a file.
+func (m *Machine) Read(p string) (string, error) {
+	b, err := os.ReadFile(m.at(p))
+	return string(b), err
+}
+
+// Exists says whether a path is there.
+func (m *Machine) Exists(p string) bool {
+	_, err := os.Lstat(m.at(p))
+	return err == nil
+}
+
+// Stat is a path's owner and whether it is a folder.
+func (m *Machine) Stat(p string) (Owner, error) {
+	info, err := os.Stat(m.at(p))
+	if err != nil {
+		return Owner{}, err
+	}
+	of := m.ownerOf
+	if of == nil {
+		of = inodeOwner
+	}
+	uid, gid := of(info)
+	return Owner{UID: uid, GID: gid, Dir: info.IsDir()}, nil
+}
+
+// Real is a path with every symbolic link followed, as the machine sees it.
+func (m *Machine) Real(p string) (string, error) {
+	real, err := filepath.EvalSymlinks(m.at(p))
+	if err != nil {
+		return "", err
+	}
+	rel, err := filepath.Rel(m.Root, real)
+	if err != nil || strings.HasPrefix(rel, "..") {
+		return "", fmt.Errorf("%s leads outside the machine", p)
+	}
+	return path.Join("/", filepath.ToSlash(rel)), nil
+}
+
+// Children are a folder's subfolders, by name; symbolic links are not followed.
+func (m *Machine) Children(p string) []string {
+	entries, err := os.ReadDir(m.at(p))
+	if err != nil {
+		return nil
+	}
+	var out []string
+	for _, e := range entries {
+		if e.Type()&fs.ModeSymlink == 0 && e.IsDir() {
+			out = append(out, e.Name())
+		}
+	}
+	return out
+}
+
+// Write writes one of the module's own files, and refuses every other path.
+func (m *Machine) Write(p, content string, mode os.FileMode) error {
+	if !writable(p) {
+		return fmt.Errorf("%s is not one of the module's files; it writes nothing else", p)
+	}
+	if err := os.MkdirAll(filepath.Dir(m.at(p)), 0o755); err != nil {
+		return err
+	}
+	tmp := m.at(p) + ".tmp"
+	if err := os.WriteFile(tmp, []byte(content), mode); err != nil {
+		return err
+	}
+	return os.Rename(tmp, m.at(p))
+}
+
+// Place moves the checked candidate into Samba's configuration's place.
+func (m *Machine) Place() error { return os.Rename(m.at(Candidate), m.at(SambaConf)) }
+
+// NameOf is the account or group name for an id, read from the machine's passwd or group file.
+func (m *Machine) NameOf(file string, id int) string {
+	text, _ := m.Read(file)
+	for _, line := range strings.Split(text, "\n") {
+		f := strings.Split(line, ":")
+		if len(f) >= 3 && f[2] == strconv.Itoa(id) {
+			return f[0]
+		}
+	}
+	return ""
+}
+
+// HasAccount says whether the machine has an account of that name.
+func (m *Machine) HasAccount(name string) bool {
+	text, _ := m.Read("/etc/passwd")
+	for _, line := range strings.Split(text, "\n") {
+		if f := strings.SplitN(line, ":", 2); len(f) == 2 && f[0] == name {
+			return true
+		}
+	}
+	return false
+}
+
+// Escalated is a command as the operator account runs what only root may: through sudo without a prompt.
+func (m *Machine) Escalated(name string, args ...string) (string, []string) {
+	if m.UID == 0 {
+		return name, args
+	}
+	return "sudo", append([]string{"-n", name}, args...)
+}
+
+// AsRoot runs what only root may do, and names a refusal by how it failed.
+func (m *Machine) AsRoot(ctx context.Context, input, name string, args ...string) (Ran, error) {
+	program, argv := m.Escalated(name, args...)
+	r := m.Run(ctx, input, program, argv...)
+	if r.Code != 0 {
+		why := r.Err
+		if why == "" {
+			why = strings.TrimSpace(r.Out)
+		}
+		return r, fmt.Errorf("%s %s: exit %d: %s", name, strings.Join(args, " "), r.Code, why)
+	}
+	return r, nil
+}
+
+// UnitState is what the service manager says of a unit: active, inactive, failed, …
+func (m *Machine) UnitState(unit string) string {
+	r := m.Run(context.Background(), "", "systemctl", "is-active", unit)
+	if s := strings.TrimSpace(r.Out); s != "" {
+		return s
+	}
+	return "unknown"
+}
+
+// UnitEnabled is what the service manager says of a unit's boot: enabled, disabled, …
+func (m *Machine) UnitEnabled(unit string) string {
+	r := m.Run(context.Background(), "", "systemctl", "is-enabled", unit)
+	if s := strings.TrimSpace(r.Out); s != "" {
+		return s
+	}
+	return "unknown"
+}
+
+func inodeOwner(info os.FileInfo) (uid, gid int) {
+	if st, ok := info.Sys().(*syscall.Stat_t); ok {
+		return int(st.Uid), int(st.Gid)
+	}
+	return -1, -1
+}
+
+func firstLine(s string) string {
+	s = strings.TrimSpace(s)
+	if i := strings.IndexByte(s, '\n'); i >= 0 {
+		return s[:i]
+	}
+	return s
+}
@@ -0,0 +1,38 @@
+// The smb-server module's Go bundle (novox/hq ADR 0341): a node serves folders over SMB to the devices on its
+// own network, one share per folder, every client as the folder's owner, SMB 2.1 and later on 445 alone.
+//
+// Started with no arguments it is served by the node's runtime as the operator account, over MCP on stdio
+// (ADR 0188, ADR 0193): the node-smb-server seat's verbs and the module's health. Started as
+// `smb-server config` it is the module's long-running process, as root (process.go). stdout is the MCP
+// channel; everything else is said on stderr.
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/signal"
+	"syscall"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+func main() {
+	if len(os.Args) > 1 {
+		if os.Args[1] != "config" || len(os.Args) != 2 {
+			fmt.Fprintln(os.Stderr, "usage: smb-server [config]")
+			os.Exit(2)
+		}
+		ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGTERM, os.Interrupt)
+		defer stop()
+		if err := Here().RunConfig(ctx); err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+		return
+	}
+	if err := stdio.Serve("", Tools(Here())); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
@@ -0,0 +1,397 @@
+package main
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"path"
+	"strings"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/health"
+)
+
+// The module's process, as root: every Every it judges the shares, and — only once a person adopted the
+// configuration — writes Samba's configuration whole, checks it with testparm before Samba reads it, sets the
+// logins' passwords from their secrets and stops NetBIOS (novox/hq ADR 0341 clauses 3 to 7). Before adoption
+// it reads the hand-written configuration, reports it, and writes nothing but its status.
+
+// Every is how often the process looks.
+const Every = 30 * time.Second
+
+// Adoption is a person's word to take over, left by the adopt verb.
+type Adoption struct {
+	At  string `json:"at"`
+	Why string `json:"why"`
+	// Copy is the dated copy of the hand-written configuration, once the process kept it.
+	Copy string `json:"copy,omitempty"`
+}
+
+// Login is one login of the `users` setting, as the process found it.
+type Login struct {
+	Name string `json:"name"`
+	// Password is "set" (from its secret), "kept as found" (in Samba's database, no secret given),
+	// "waits" (no secret, not in Samba's database) or "refused" (why says).
+	Password string `json:"password"`
+	Why      string `json:"why,omitempty"`
+}
+
+// Status is the process's last look, as the tools read it.
+type Status struct {
+	At string `json:"at"`
+	// Mode is "found" (the hand-written configuration serves, kept as found) or "adopted" (the module's).
+	Mode     string        `json:"mode"`
+	Shares   []Served      `json:"shares"`
+	Refused  []Refused     `json:"refused,omitempty"`
+	Hand     []HandShare   `json:"hand_written,omitempty"`
+	Logins   []Login       `json:"logins,omitempty"`
+	Problems []string      `json:"problems,omitempty"`
+	Waits    []health.Wait `json:"waits,omitempty"`
+	Adopted  *Adoption     `json:"adopted,omitempty"`
+	// Written is when the process last wrote Samba's configuration, and Reloaded when Samba last read it.
+	Written  string `json:"written,omitempty"`
+	Reloaded string `json:"reloaded,omitempty"`
+	NetBIOS  string `json:"netbios,omitempty"`
+}
+
+// WalkDepth and WalkLimit bound the look below a share for a backup repository (ADR 0263 §3).
+const (
+	WalkDepth = 4
+	WalkLimit = 200000
+)
+
+// isRepository says whether a folder is a restic repository: `config` beside `keys`, `snapshots`, `data`.
+func (m *Machine) isRepository(dir string) bool {
+	if o, err := m.Stat(path.Join(dir, "config")); err != nil || o.Dir {
+		return false
+	}
+	for _, sub := range []string{"keys", "snapshots", "data"} {
+		if o, err := m.Stat(path.Join(dir, sub)); err != nil || !o.Dir {
+			return false
+		}
+	}
+	return true
+}
+
+// repositoryNear finds a backup repository at, above or within WalkDepth levels below a folder; complete is
+// false when the look below stopped at its bound.
+func (m *Machine) repositoryNear(real string) (found string, complete bool) {
+	for p := real; ; p = path.Dir(p) {
+		if m.isRepository(p) {
+			return p, true
+		}
+		if p == "/" {
+			break
+		}
+	}
+	seen, level := 0, []string{real}
+	for depth := 1; depth <= WalkDepth && len(level) > 0; depth++ {
+		var next []string
+		for _, d := range level {
+			for _, c := range m.Children(d) {
+				if seen++; seen > WalkLimit {
+					return "", false
+				}
+				p := path.Join(d, c)
+				if m.isRepository(p) {
+					return p, true
+				}
+				next = append(next, p)
+			}
+		}
+		level = next
+	}
+	return "", true
+}
+
+// Judge turns the asked-for shares into served shares, or refusals.
+func (m *Machine) Judge(c Config) ([]Served, []Refused) {
+	var out []Served
+	var refused []Refused
+	for _, s := range c.Shares {
+		no := func(why string) { refused = append(refused, Refused{Name: s.Name, Path: s.Path, Why: why}) }
+		if !path.IsAbs(s.Path) || strings.ContainsAny(s.Path, "\n\r\"\\") {
+			no(fmt.Sprintf("The share %s names %q, which is not an absolute path a configuration can carry.", s.Name, s.Path))
+			continue
+		}
+		real, err := m.Real(path.Clean(s.Path))
+		if err != nil {
+			no(fmt.Sprintf("The share %s's folder %s is not there (%v); the module never creates it.", s.Name, s.Path, err))
+			continue
+		}
+		if real == "/" {
+			no(fmt.Sprintf("The share %s is the machine's root, which is never shared.", s.Name))
+			continue
+		}
+		o, err := m.Stat(real)
+		if err != nil || !o.Dir {
+			no(fmt.Sprintf("The share %s's path %s is not a folder.", s.Name, real))
+			continue
+		}
+		if o.UID == 0 || o.GID == 0 {
+			no(fmt.Sprintf("The share %s's folder %s is owned by root (%d:%d), and every client would act as root there: give it an owner of its own.", s.Name, real, o.UID, o.GID))
+			continue
+		}
+		if p, complete := m.repositoryNear(real); p != "" {
+			no(fmt.Sprintf("The share %s's folder %s is at, inside or above the backup repository %s, and backups are never shared.", s.Name, real, p))
+			continue
+		} else if !complete {
+			no(fmt.Sprintf("The share %s's folder %s holds more folders than the module looks through (%d levels, at most %d), so it could not make sure no backup repository is under it.", s.Name, real, WalkDepth, WalkLimit))
+			continue
+		}
+		user, group := m.NameOf("/etc/passwd", o.UID), m.NameOf("/etc/group", o.GID)
+		if user == "" || group == "" {
+			no(fmt.Sprintf("The share %s's folder %s is owned by %d:%d, which this machine names no account or group for, so no client can be made its owner.", s.Name, real, o.UID, o.GID))
+			continue
+		}
+		if len(c.Users) == 0 {
+			no(fmt.Sprintf("The share %s is not served: the setting users names no login.", s.Name))
+			continue
+		}
+		out = append(out, Served{Name: s.Name, Path: real, Access: s.Access, UID: o.UID, GID: o.GID, User: user, Group: group, Users: c.Users})
+	}
+	return out, refused
+}
+
+// PasswordSecret is the secret holding a login's password.
+func PasswordSecret(user string) string { return "smb-password-" + user }
+
+// readSecret reads a login's password from its secret: one line; absent is not given.
+func (m *Machine) readSecret(dir, user string) (string, bool, error) {
+	if dir == "" || !path.IsAbs(dir) {
+		return "", false, fmt.Errorf("the mesh gave no folder for the logins' secrets")
+	}
+	raw, err := m.Read(path.Join(dir, PasswordSecret(user)+".secret"))
+	if err != nil {
+		if !m.Exists(path.Join(dir, PasswordSecret(user)+".secret")) {
+			return "", false, nil
+		}
+		return "", false, err
+	}
+	pw := strings.TrimRight(raw, "\r\n")
+	if pw == "" || strings.ContainsAny(pw, "\r\n") {
+		return "", false, fmt.Errorf("its secret is not one line")
+	}
+	return pw, true, nil
+}
+
+func digest(user, pw string) string {
+	h := sha256.Sum256([]byte(user + "\x00" + pw))
+	return hex.EncodeToString(h[:])
+}
+
+// Logins judges every login of the setting and, when adopted, sets a password whose secret is new or changed
+// (clause 5). A login in Samba's database with no secret given keeps its password; the module never removes
+// or resets an entry by itself.
+func (m *Machine) Logins(ctx context.Context, c Config, adopted bool) ([]Login, []health.Wait, []string) {
+	var logins []Login
+	var waits []health.Wait
+	var problems []string
+	set := map[string]string{}
+	if raw, err := m.Read(SetFile); err == nil {
+		_ = json.Unmarshal([]byte(raw), &set)
+	}
+	changed := false
+	for _, u := range c.Users {
+		l := Login{Name: u}
+		inDB := m.Run(ctx, "", "pdbedit", "-L", "-u", u).Code == 0
+		pw, given, err := m.readSecret(c.Passwords, u)
+		switch {
+		case err != nil:
+			l.Password, l.Why = "refused", "its password "+PasswordSecret(u)+" could not be read: "+err.Error()
+			problems = append(problems, fmt.Sprintf("the login %s: %s", u, l.Why))
+		case !given && inDB:
+			l.Password, l.Why = "kept as found", "no secret "+PasswordSecret(u)+" is given, so the password in Samba's database stands"
+		case !given:
+			l.Password, l.Why = "waits", "no secret "+PasswordSecret(u)+" is given and Samba's database has no such login"
+			waits = append(waits, health.Wait{Part: "the login " + u, Secret: PasswordSecret(u), What: "the password of the login " + u})
+		case !m.HasAccount(u):
+			l.Password, l.Why = "refused", "this machine has no account "+u+"; the module creates no account"
+			problems = append(problems, fmt.Sprintf("the login %s: %s", u, l.Why))
+		case !adopted:
+			l.Password, l.Why = "kept as found", "its secret is given and is set once the configuration is adopted"
+		case set[u] == digest(u, pw) && inDB:
+			l.Password = "set"
+		default:
+			// smbpasswd -s reads the new password twice from stdin; -a adds the login when it is not there.
+			args := []string{"-s", "-a", u}
+			if r := m.Run(ctx, pw+"\n"+pw+"\n", "smbpasswd", args...); r.Code != 0 {
+				l.Password, l.Why = "refused", "smbpasswd refused it: "+firstLine(r.Err)
+				problems = append(problems, fmt.Sprintf("the login %s: %s", u, l.Why))
+				break
+			}
+			set[u], changed, l.Password = digest(u, pw), true, "set"
+		}
+		logins = append(logins, l)
+	}
+	if changed {
+		raw, _ := json.MarshalIndent(set, "", "  ")
+		if err := m.Write(SetFile, string(raw)+"\n", 0o600); err != nil {
+			problems = append(problems, "which passwords were set could not be kept: "+err.Error())
+		}
+	}
+	return logins, waits, problems
+}
+
+// Pass is one look; what it did is in the status it answers, which it has written.
+func (m *Machine) Pass(ctx context.Context) Status {
+	s := Status{At: m.Now().UTC().Format(time.RFC3339), Mode: "found", Shares: []Served{}}
+	text, err := m.Read(ConfigFile)
+	if err != nil {
+		s.Problems = append(s.Problems, fmt.Sprintf("the assignment's shares (%s) could not be read: %v", ConfigFile, err))
+	}
+	c, problems := ParseConfig(text)
+	s.Problems = append(s.Problems, problems...)
+	served, refused := m.Judge(c)
+	s.Refused = refused
+	conf, _ := m.Read(SambaConf)
+	ours := strings.HasPrefix(conf, Marker)
+	if !ours {
+		s.Hand = HandShares(ParseSamba(conf), c.Shares)
+	}
+	var adoption *Adoption
+	if raw, err := m.Read(AdoptFile); err == nil {
+		var a Adoption
+		if json.Unmarshal([]byte(raw), &a) == nil && a.At != "" {
+			adoption = &a
+		}
+	}
+	if ours && adoption == nil {
+		// Written by the module before, and the word is gone: what it wrote stands, and is the module's.
+		adoption = &Adoption{At: "before", Why: "the configuration is already the module's"}
+	}
+	s.Adopted = adoption
+	if adoption != nil {
+		if !ours {
+			if missing := withoutCounterpart(s.Hand); len(missing) > 0 {
+				s.Problems = append(s.Problems, "the configuration is not taken over: "+strings.Join(missing, "; "))
+				adoption = nil
+			} else if served == nil && len(c.Shares) > 0 {
+				s.Problems = append(s.Problems, "the configuration is not taken over: no share the settings name can be served")
+				adoption = nil
+			}
+		}
+	}
+	if adoption != nil {
+		s.Mode = "adopted"
+		m.takeOver(ctx, &s, conf, ours, served, adoption)
+	} else {
+		for i := range served {
+			served[i].Live = false
+		}
+	}
+	logins, waits, lp := m.Logins(ctx, c, s.Mode == "adopted")
+	s.Logins, s.Waits = logins, waits
+	s.Problems = append(s.Problems, lp...)
+	if s.Mode == "adopted" {
+		s.Shares = m.markLive(ctx, served)
+	} else {
+		s.Shares = served
+	}
+	raw, _ := json.MarshalIndent(s, "", "  ")
+	if err := m.Write(StatusFile, string(raw)+"\n", 0o644); err != nil {
+		s.Problems = append(s.Problems, "the status file could not be written: "+err.Error())
+	}
+	return s
+}
+
+// withoutCounterpart is each hand-written share the settings do not take the place of, in words.
+func withoutCounterpart(hand []HandShare) []string {
+	var out []string
+	for _, h := range hand {
+		if h.Counterpart == "" {
+			out = append(out, fmt.Sprintf("the hand-written share %s (%s) has no counterpart: %s", h.Name, h.Path, h.Why))
+		}
+	}
+	return out
+}
+
+// takeOver writes the module's configuration when it differs from what is there: the first time, a dated
+// copy of the hand-written one is kept; every time, testparm checks the candidate before it takes the
+// configuration's place and Samba reads it. Then NetBIOS is stopped.
+func (m *Machine) takeOver(ctx context.Context, s *Status, conf string, ours bool, served []Served, a *Adoption) {
+	want := Render(served)
+	if conf != want {
+		if err := m.Write(Candidate, want, 0o644); err != nil {
+			s.Problems = append(s.Problems, "the module's configuration could not be written: "+err.Error())
+			return
+		}
+		if r := m.Run(ctx, "", "testparm", "-s", m.at(Candidate)); r.Code != 0 {
+			s.Problems = append(s.Problems, "the module's configuration fails Samba's own check and is kept out of use: "+firstLine(r.Err))
+			return
+		}
+		if !ours {
+			copyAt := HandCopyPrefix + m.Now().UTC().Format("20060102T150405Z")
+			if err := m.Write(copyAt, conf, 0o644); err != nil {
+				s.Problems = append(s.Problems, "the hand-written configuration could not be kept, so it is not replaced: "+err.Error())
+				return
+			}
+			a.Copy = copyAt
+			if a.At != "before" {
+				raw, _ := json.MarshalIndent(a, "", "  ")
+				_ = m.Write(AdoptFile, string(raw)+"\n", 0o644)
+			}
+		}
+		if err := m.Place(); err != nil {
+			s.Problems = append(s.Problems, "the module's configuration could not take its place: "+err.Error())
+			return
+		}
+		s.Written = m.Now().UTC().Format(time.RFC3339)
+		if r := m.Run(ctx, "", "smbcontrol", "smbd", "reload-config"); r.Code != 0 {
+			s.Problems = append(s.Problems, "Samba did not read its configuration again: "+firstLine(r.Err))
+		} else {
+			s.Reloaded = s.Written
+		}
+	}
+	if m.UnitState(NMBUnit) == "active" || m.UnitEnabled(NMBUnit) == "enabled" {
+		if r := m.Run(ctx, "", "systemctl", "disable", "--now", NMBUnit); r.Code != 0 {
+			s.Problems = append(s.Problems, "NetBIOS ("+NMBUnit+") could not be stopped: "+firstLine(r.Err))
+		}
+	}
+	s.NetBIOS = m.UnitState(NMBUnit)
+}
+
+// markLive marks each share Samba serves now, as testparm reads the configuration in use.
+func (m *Machine) markLive(ctx context.Context, served []Served) []Served {
+	r := m.Run(ctx, "", "testparm", "-s", m.at(SambaConf))
+	live := map[string]bool{}
+	if r.Code == 0 {
+		for _, sec := range ParseSamba(r.Out) {
+			live[strings.ToLower(sec.Name)] = true
+		}
+	}
+	for i := range served {
+		served[i].Live = live[strings.ToLower(served[i].Name)] && m.UnitState(Unit) == "active"
+	}
+	return served
+}
+
+// RunConfig is the process: a pass now and every Every until the context ends.
+func (m *Machine) RunConfig(ctx context.Context) error {
+	m.Pass(ctx)
+	t := time.NewTicker(Every)
+	defer t.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return nil
+		case <-t.C:
+			m.Pass(ctx)
+		}
+	}
+}
+
+// LastStatus is the process's last look, or why there is none.
+func (m *Machine) LastStatus() (*Status, error) {
+	text, err := m.Read(StatusFile)
+	if err != nil {
+		return nil, fmt.Errorf("the module's process has written no status (%s): %v", StatusFile, err)
+	}
+	var s Status
+	if err := json.Unmarshal([]byte(text), &s); err != nil {
+		return nil, fmt.Errorf("the module's status file is not one: %v", err)
+	}
+	return &s, nil
+}
@@ -0,0 +1,301 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+// Defends novox/hq ADR 0341 clauses 2 to 7 and 11 to 13: an SMB share is served as its folder's owner, SMB
+// 2.1 and later on 445 alone with NetBIOS off; before a person adopts it the hand-written configuration is
+// kept as found and nothing is written; adoption keeps a dated copy, writes the module's configuration only
+// once testparm passes it, and refuses while a hand-written share has no counterpart; a login without its
+// secret keeps its password, and one with it is set once.
+
+type fake struct {
+	t       *testing.T
+	root    string
+	answers map[string]Ran
+	ran     []string
+	inputs  map[string]string
+	now     time.Time
+}
+
+func newFake(t *testing.T) *fake {
+	f := &fake{t: t, root: t.TempDir(), answers: map[string]Ran{}, inputs: map[string]string{}, now: time.Date(2026, 10, 13, 9, 30, 0, 0, time.UTC)}
+	f.answers["systemctl is-active smb.service"] = Ran{Out: "active\n"}
+	f.answers["systemctl is-active nmb.service"] = Ran{Out: "active\n"}
+	f.answers["systemctl is-enabled nmb.service"] = Ran{Out: "enabled\n"}
+	f.answers["pdbedit -L -u media"] = Ran{Out: "media:1001:\n"}
+	f.file("/etc/passwd", "root:x:0:0::/root:/bin/sh\nmedia:x:1001:2000::/home/media:/bin/sh\n")
+	f.file("/etc/group", "root:x:0:\nmedia:x:2000:\n")
+	return f
+}
+
+func (f *fake) machine() *Machine {
+	return &Machine{Root: f.root, UID: 0, Now: func() time.Time { return f.now },
+		ownerOf: func(info os.FileInfo) (int, int) {
+			if strings.HasPrefix(info.Name(), "rootowned") {
+				return 0, 0
+			}
+			return 1001, 2000
+		},
+		Run: func(_ context.Context, input, name string, args ...string) Ran {
+			line := strings.Join(append([]string{name}, args...), " ")
+			line = strings.ReplaceAll(line, f.root, "")
+			f.ran = append(f.ran, line)
+			if input != "" {
+				f.inputs[line] = input
+			}
+			if line == "systemctl disable --now nmb.service" {
+				f.answers["systemctl is-active nmb.service"] = Ran{Out: "inactive\n"}
+				f.answers["systemctl is-enabled nmb.service"] = Ran{Out: "disabled\n"}
+			}
+			if strings.HasPrefix(line, "testparm -s ") {
+				if r, ok := f.answers["testparm"]; ok {
+					return r
+				}
+				return Ran{Out: f.read(strings.TrimPrefix(line, "testparm -s "))}
+			}
+			return f.answers[line]
+		}}
+}
+
+func (f *fake) dir(p string) {
+	if err := os.MkdirAll(filepath.Join(f.root, p), 0o755); err != nil {
+		f.t.Fatal(err)
+	}
+}
+
+func (f *fake) file(p, content string) {
+	f.dir(filepath.Dir(p))
+	if err := os.WriteFile(filepath.Join(f.root, p), []byte(content), 0o644); err != nil {
+		f.t.Fatal(err)
+	}
+}
+
+func (f *fake) read(p string) string {
+	b, _ := os.ReadFile(filepath.Join(f.root, p))
+	return string(b)
+}
+
+func (f *fake) ran1(prefix string) []string {
+	var out []string
+	for _, r := range f.ran {
+		if strings.HasPrefix(r, prefix) {
+			out = append(out, r)
+		}
+	}
+	return out
+}
+
+// handWritten is the home server's configuration as issue 169's survey found it.
+const handWritten = "[global]\n   workgroup = WORKGROUP\n   server string = home\n\n[media]\n   path = /storage/media/\n   valid users = media\n   writable = yes\n"
+
+func (f *fake) home(shares, users string) {
+	f.dir("/storage/media")
+	f.file(ConfigFile, "shares="+shares+"\nusers="+users+"\npasswords=/var/lib/mesh/smb-server/state\n")
+	f.file(SambaConf, handWritten)
+}
+
+func TestTheRenderingServesAsTheOwnerOnFourFortyFiveAloneWithoutNetBIOS(t *testing.T) {
+	text := Render([]Served{{Name: "media", Path: "/storage/media", Access: "rw", User: "media", Group: "media", Users: []string{"media"}}})
+	for _, want := range []string{Marker, "server min protocol = SMB2_10", "disable netbios = yes", "smb ports = 445", "map to guest = never",
+		"[media]", "path = /storage/media", "read only = no", "valid users = media", "force user = media", "force group = media"} {
+		if !strings.Contains(text, want) {
+			t.Errorf("the rendering lacks %q:\n%s", want, text)
+		}
+	}
+	if strings.Contains(text, "139") || strings.Contains(text, "1001") {
+		t.Errorf("the rendering names 139, or an owner as a number:\n%s", text)
+	}
+}
+
+func TestAShareIsRefusedAtRootRootOwnedMissingOrNearABackupAndNothingIsCreated(t *testing.T) {
+	f := newFake(t)
+	f.dir("/srv/rootowned")
+	f.dir("/srv/pool/library")
+	f.file("/srv/pool/library/deep/repo/config", "x")
+	for _, d := range []string{"keys", "snapshots", "data"} {
+		f.dir("/srv/pool/library/deep/repo/" + d)
+	}
+	f.dir("/srv/ok")
+	c, _ := ParseConfig("shares=root=/ owned=/srv/rootowned gone=/srv/gone lib=/srv/pool/library ok=/srv/ok:ro\nusers=media\n")
+	served, refused := f.machine().Judge(c)
+	why := map[string]string{}
+	for _, r := range refused {
+		why[r.Name] = r.Why
+	}
+	for name, says := range map[string]string{"root": "machine's root", "owned": "owned by root", "gone": "not there", "lib": "backup repository"} {
+		if !strings.Contains(why[name], says) {
+			t.Errorf("%s is not refused as %q: %q", name, says, why[name])
+		}
+	}
+	if len(served) != 1 || served[0].Name != "ok" || served[0].Access != "ro" || served[0].User != "media" {
+		t.Errorf("served: %+v", served)
+	}
+	if f.machine().Exists("/srv/gone") {
+		t.Error("the module created a missing folder")
+	}
+}
+
+func TestBeforeAdoptionTheHandWrittenConfigurationIsKeptAndNothingIsWritten(t *testing.T) {
+	f := newFake(t)
+	f.home("media=/storage/media", "media")
+	s := f.machine().Pass(context.Background())
+	if s.Mode != "found" || f.read(SambaConf) != handWritten {
+		t.Fatalf("mode %s; the hand-written configuration changed:\n%s", s.Mode, f.read(SambaConf))
+	}
+	if len(s.Hand) != 1 || s.Hand[0].Counterpart != "media" || s.Hand[0].ReadOnly {
+		t.Errorf("the hand-written share is not matched: %+v", s.Hand)
+	}
+	for _, r := range f.ran {
+		if strings.HasPrefix(r, "smbcontrol") || strings.HasPrefix(r, "systemctl disable") || strings.HasPrefix(r, "smbpasswd") {
+			t.Errorf("before adoption the process ran %q", r)
+		}
+	}
+	if s.Logins[0].Password != "kept as found" {
+		t.Errorf("the login: %+v", s.Logins)
+	}
+	if h := f.machine().Health(); !h.Healthy || !strings.Contains(h.Why, "adopt") {
+		t.Errorf("health before adoption: %+v", h)
+	}
+}
+
+func TestAdoptRefusesWhileAHandWrittenShareHasNoCounterpart(t *testing.T) {
+	f := newFake(t)
+	f.home("library=/storage/media", "media")
+	f.machine().Pass(context.Background())
+	if _, err := f.machine().Adopt(true, "take it over"); err == nil || !strings.Contains(err.Error(), "no share disappears") {
+		t.Fatalf("adopt with a hand-written share the settings do not name: %v", err)
+	}
+	if f.machine().Exists(AdoptFile) {
+		t.Error("a refused adopt left the word for the process")
+	}
+	f.file(ConfigFile, "shares=media=/storage/media\nusers=media\npasswords=/x\n")
+	f.machine().Pass(context.Background())
+	dry, err := f.machine().Adopt(false, "")
+	if err != nil || !dry.DryRun || len(dry.Beside) != 1 || !strings.Contains(dry.Beside[0], "every client as media:media") {
+		t.Fatalf("dry run: %+v %v", dry, err)
+	}
+	if f.machine().Exists(AdoptFile) {
+		t.Error("a dry run left the word for the process")
+	}
+	if _, err := f.machine().Adopt(true, ""); err == nil {
+		t.Error("adopt with confirm and no why was done")
+	}
+}
+
+func TestAdoptionKeepsADatedCopyChecksAndThenStopsNetBIOS(t *testing.T) {
+	f := newFake(t)
+	f.home("media=/storage/media", "media")
+	f.machine().Pass(context.Background())
+	f.file(AdoptFile, `{"at":"2026-10-13T09:31:00Z","why":"the operator keeps the share"}`)
+	f.ran = nil
+	s := f.machine().Pass(context.Background())
+	if s.Mode != "adopted" || len(s.Problems) != 0 {
+		t.Fatalf("status: %+v", s)
+	}
+	copyAt := HandCopyPrefix + "20261013T093000Z"
+	if f.read(copyAt) != handWritten {
+		t.Errorf("the dated copy is not the hand-written configuration: %q", f.read(copyAt))
+	}
+	if !strings.HasPrefix(f.read(SambaConf), Marker) || !strings.Contains(f.read(SambaConf), "force user = media") {
+		t.Errorf("the module's configuration is not in place:\n%s", f.read(SambaConf))
+	}
+	want := []string{"testparm -s " + Candidate, "smbcontrol smbd reload-config", "systemctl disable --now nmb.service"}
+	for _, w := range want {
+		if len(f.ran1(w)) != 1 {
+			t.Errorf("%q ran %d times: %v", w, len(f.ran1(w)), f.ran)
+		}
+	}
+	if !s.Shares[0].Live || s.NetBIOS != "inactive" {
+		t.Errorf("served: %+v netbios %s", s.Shares, s.NetBIOS)
+	}
+	// The next pass finds its own configuration and writes nothing again.
+	f.ran = nil
+	f.machine().Pass(context.Background())
+	if len(f.ran1("smbcontrol")) != 0 || len(f.ran1("systemctl disable")) != 0 {
+		t.Errorf("an unchanged configuration was written or reloaded again: %v", f.ran)
+	}
+}
+
+func TestAConfigurationFailingTestparmIsKeptOutOfUse(t *testing.T) {
+	f := newFake(t)
+	f.home("media=/storage/media", "media")
+	f.file(AdoptFile, `{"at":"2026-10-13T09:31:00Z","why":"take over"}`)
+	f.answers["testparm"] = Ran{Code: 1, Err: "Unknown parameter encountered"}
+	s := f.machine().Pass(context.Background())
+	if f.read(SambaConf) != handWritten {
+		t.Errorf("a configuration testparm refused took the hand-written one's place")
+	}
+	if len(f.ran1("smbcontrol")) != 0 || !strings.Contains(strings.Join(s.Problems, " "), "fails Samba's own check") {
+		t.Errorf("not said, or reloaded: %v %v", s.Problems, f.ran)
+	}
+	if h := f.machine().Health(); h.Healthy {
+		t.Errorf("healthy with a refused configuration: %+v", h)
+	}
+}
+
+func TestALoginKeepsItsPasswordWithoutASecretWaitsWhenNewAndIsSetOnce(t *testing.T) {
+	f := newFake(t)
+	f.home("media=/storage/media", "media guest2")
+	f.answers["pdbedit -L -u guest2"] = Ran{Code: 255}
+	f.file(AdoptFile, `{"at":"2026-10-13T09:31:00Z","why":"take over"}`)
+	s := f.machine().Pass(context.Background())
+	got := map[string]string{}
+	for _, l := range s.Logins {
+		got[l.Name] = l.Password
+	}
+	if got["media"] != "kept as found" || got["guest2"] != "waits" || len(f.ran1("smbpasswd")) != 0 {
+		t.Fatalf("logins %v; smbpasswd ran %v", got, f.ran1("smbpasswd"))
+	}
+	h := f.machine().Health()
+	if h.State != "waits" || len(h.Waits) != 1 || h.Waits[0].Secret != "smb-password-guest2" {
+		t.Errorf("health: %+v", h)
+	}
+	// The secret given: set once from stdin, never on the command line, and not again while unchanged.
+	f.file("/etc/passwd", f.read("/etc/passwd")+"guest2:x:1002:2000::/:/bin/sh\n")
+	f.file("/var/lib/mesh/smb-server/state/smb-password-guest2.secret", "s3cret\n")
+	f.machine().Pass(context.Background())
+	runs := f.ran1("smbpasswd")
+	if len(runs) != 1 || runs[0] != "smbpasswd -s -a guest2" || f.inputs[runs[0]] != "s3cret\ns3cret\n" {
+		t.Fatalf("smbpasswd: %v %q", runs, f.inputs)
+	}
+	f.answers["pdbedit -L -u guest2"] = Ran{Out: "guest2:1002:\n"}
+	f.machine().Pass(context.Background())
+	if len(f.ran1("smbpasswd")) != 1 {
+		t.Errorf("an unchanged password was set again: %v", f.ran1("smbpasswd"))
+	}
+	var set map[string]string
+	_ = json.Unmarshal([]byte(f.read(SetFile)), &set)
+	if strings.Contains(f.read(SetFile), "s3cret") || set["guest2"] == "" {
+		t.Errorf("the record of set passwords holds the password, or nothing: %s", f.read(SetFile))
+	}
+	if info, err := os.Stat(filepath.Join(f.root, SetFile)); err != nil || info.Mode().Perm() != 0o600 {
+		t.Errorf("the record of set passwords is not root's alone: %v", info.Mode())
+	}
+}
+
+func TestTheModuleWritesOnlyItsOwnFiles(t *testing.T) {
+	m := newFake(t).machine()
+	for _, p := range []string{"/etc/passwd", "/storage/media/x", "/etc/samba/other.conf", HandCopyPrefix + "x/../../evil"} {
+		if err := m.Write(p, "x", 0o644); err == nil {
+			t.Errorf("wrote %s", p)
+		}
+	}
+}
+
+func TestParseSambaReadsSectionsAndAccess(t *testing.T) {
+	secs := ParseSamba("; c\n[global]\nworkgroup = W\n[a]\n path = /x\n read only = no\n[b]\n path = /y\n[c]\n path = /z\n writeable = yes\n")
+	if len(secs) != 4 || secs[1].Params["path"] != "/x" {
+		t.Fatalf("%+v", secs)
+	}
+	if readOnly(secs[1].Params) || !readOnly(secs[2].Params) || readOnly(secs[3].Params) {
+		t.Error("read only is not read as Samba reads it")
+	}
+}
@@ -0,0 +1,366 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"strings"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/health"
+)
+
+// Seat is the role this module holds on its machine (novox/hq ADR 0341).
+const Seat = "node-smb-server"
+
+// Stale is how old the process's last look may be before the tools say it stopped looking.
+const Stale = 5 * time.Minute
+
+func verb(name, description string, input map[string]any, run func(a map[string]any) (any, error)) stdio.Tool {
+	return stdio.Tool{Name: Seat + "." + name, Description: description, Input: input, Run: run}
+}
+
+func str(description string) map[string]any {
+	return map[string]any{"type": "string", "description": description}
+}
+
+func arg(a map[string]any, k string) string {
+	v, _ := a[k].(string)
+	return strings.TrimSpace(v)
+}
+
+// confirmed says whether an act was confirmed: the boolean true, or the string "true" the seat's schema passes.
+func confirmed(a map[string]any) bool {
+	switch v := a["confirm"].(type) {
+	case bool:
+		return v
+	case string:
+		return strings.EqualFold(strings.TrimSpace(v), "true")
+	}
+	return false
+}
+
+// Tools are the seat's verbs and the module's health.
+func Tools(m *Machine) []stdio.Tool {
+	return []stdio.Tool{
+		verb("shares", "Every SMB share this machine serves: its name, folder, rw or ro, the owner every client acts as "+
+			"(uid, gid, names), the logins allowed and whether each login's password was set from its secret, is kept "+
+			"as found or waits for it, and whether Samba serves it now; whether the configuration is the mesh's or still "+
+			"the hand-written one, and each hand-written share with whether the settings take its place; the shares "+
+			"refused, and why. A password is never shown. Replaces testparm -s, cat /etc/samba/smb.conf and pdbedit -L. (r)",
+			map[string]any{}, func(map[string]any) (any, error) { return m.Shares(), nil }),
+		verb("sessions", "Which devices are connected to which share now, with the login and protocol each uses, as "+
+			"Samba knows them (smbstatus, as root). Replaces smbstatus. (r)",
+			map[string]any{}, func(map[string]any) (any, error) { return m.Sessions(context.Background()) }),
+		verb("test", "Whether this machine serves one share now: asked for and not refused, served by Samba, Samba "+
+			"active, and 445 listening. Replaces smbclient -L. (r)",
+			map[string]any{"share": str("the share's name")},
+			func(a map[string]any) (any, error) { return m.Test(context.Background(), arg(a, "share")) }),
+		verb("reload", "Have Samba read its configuration again now (smbcontrol smbd reload-config, as root). The "+
+			"module's process does this itself whenever it writes the configuration; this is for after a change made "+
+			"outside it. Changes no shared folder. Replaces smbcontrol smbd reload-config. (a)",
+			map[string]any{}, func(map[string]any) (any, error) { return m.Reload(context.Background()) }),
+		verb("adopt", "Take over Samba's hand-written configuration: the module's process keeps a dated copy of it "+
+			"beside it and writes the mesh's own in its place, checked with testparm, then stops NetBIOS. Only when every "+
+			"hand-written share has its counterpart in the setting shares (same name, same folder), so no share "+
+			"disappears. Without confirm, a dry run: each hand-written share beside the module's rendering of it. A "+
+			"person's act, with why. Replaces edit /etc/samba/smb.conf. (a)",
+			map[string]any{
+				"confirm": str("\"true\" to do it; anything else, a dry run"),
+				"why":     str("why, in a sentence (required with confirm)"),
+			},
+			func(a map[string]any) (any, error) { return m.Adopt(confirmed(a), arg(a, "why")) }),
+		{
+			Name: "smb_health",
+			Description: "Whether this machine's SMB shares are served, as the module's health check (novox/hq ADR 0240, " +
+				"ADR 0341): unhealthy when Samba is not active, the module's process has not looked for five minutes, a " +
+				"share is refused or not served, or the configuration fails Samba's check; waits when a login's password " +
+				"is its secret not yet given; with why. (r)",
+			Run: func(map[string]any) (any, error) { return m.Health(), nil },
+		},
+	}
+}
+
+// SharesAnswer is what `shares` answers.
+type SharesAnswer struct {
+	Mode    string      `json:"configuration"`
+	Shares  []Served    `json:"shares"`
+	Refused []Refused   `json:"refused,omitempty"`
+	Hand    []HandShare `json:"hand_written,omitempty"`
+	Logins  []Login     `json:"logins,omitempty"`
+	Service string      `json:"service"`
+	Looked  string      `json:"looked,omitempty"`
+	Said    []string    `json:"said"`
+	Notes   []string    `json:"notes,omitempty"`
+}
+
+// Shares is the machine's SMB shares now.
+func (m *Machine) Shares() SharesAnswer {
+	a := SharesAnswer{Shares: []Served{}, Service: m.UnitState(Unit)}
+	st, err := m.LastStatus()
+	if err != nil {
+		a.Notes = append(a.Notes, err.Error())
+		a.Said = append(a.Said, "the module's process has not looked yet")
+		return a
+	}
+	a.Mode, a.Shares, a.Refused, a.Hand, a.Logins, a.Looked = st.Mode, st.Shares, st.Refused, st.Hand, st.Logins, st.At
+	a.Notes = st.Problems
+	if st.Mode == "found" {
+		a.Said = append(a.Said, "the configuration is the hand-written one, kept as found; the module takes it over by adopt, a person's act")
+	} else {
+		a.Said = append(a.Said, "the configuration is the module's")
+	}
+	for _, s := range st.Shares {
+		state := "served"
+		if !s.Live {
+			state = "NOT served"
+		}
+		a.Said = append(a.Said, fmt.Sprintf("%s: %s, %s, every client as %s:%s, for %s — %s", s.Name, s.Path, s.Access, s.User, s.Group, strings.Join(s.Users, " "), state))
+	}
+	for _, h := range st.Hand {
+		if h.Counterpart != "" {
+			a.Said = append(a.Said, fmt.Sprintf("hand-written %s (%s): the setting's share %s takes its place", h.Name, h.Path, h.Counterpart))
+		} else {
+			a.Said = append(a.Said, fmt.Sprintf("hand-written %s (%s): %s", h.Name, h.Path, h.Why))
+		}
+	}
+	for _, l := range st.Logins {
+		a.Said = append(a.Said, fmt.Sprintf("login %s: password %s", l.Name, l.Password))
+	}
+	for _, r := range st.Refused {
+		a.Said = append(a.Said, "refused: "+r.Why)
+	}
+	a.Said = append(a.Said, "Samba is "+a.Service)
+	return a
+}
+
+// Sessions is what smbstatus says of the connected devices.
+func (m *Machine) Sessions(ctx context.Context) (any, error) {
+	r, err := m.AsRoot(ctx, "", "smbstatus", "--json")
+	if err != nil {
+		return nil, err
+	}
+	var v struct {
+		Sessions map[string]struct {
+			Machine  string `json:"remote_machine"`
+			Username string `json:"username"`
+			Dialect  string `json:"session_dialect"`
+		} `json:"sessions"`
+		Tcons map[string]struct {
+			Service string `json:"service"`
+			Machine string `json:"machine"`
+		} `json:"tcons"`
+	}
+	if err := json.Unmarshal([]byte(r.Out), &v); err != nil {
+		return nil, fmt.Errorf("smbstatus answered what this cannot read: %v", err)
+	}
+	type session struct {
+		Device   string   `json:"device"`
+		Login    string   `json:"login"`
+		Protocol string   `json:"protocol"`
+		Shares   []string `json:"shares"`
+	}
+	var out []session
+	for _, s := range v.Sessions {
+		se := session{Device: s.Machine, Login: s.Username, Protocol: s.Dialect}
+		for _, t := range v.Tcons {
+			if t.Machine == s.Machine {
+				se.Shares = append(se.Shares, t.Service)
+			}
+		}
+		out = append(out, se)
+	}
+	return map[string]any{"sessions": out}, nil
+}
+
+// TestAnswer is what `test` answers.
+type TestAnswer struct {
+	Share     string `json:"share"`
+	Served    bool   `json:"served"`
+	Service   string `json:"service"`
+	Listening bool   `json:"listening_445"`
+	Said      string `json:"said"`
+}
+
+// Test says whether one share is served now.
+func (m *Machine) Test(ctx context.Context, share string) (TestAnswer, error) {
+	if share == "" {
+		return TestAnswer{}, fmt.Errorf("name the share")
+	}
+	a := TestAnswer{Share: share, Service: m.UnitState(Unit)}
+	r := m.Run(ctx, "", "ss", "-ltnH", "sport", "=", ":445")
+	a.Listening = strings.TrimSpace(r.Out) != ""
+	st, err := m.LastStatus()
+	if err != nil {
+		return a, err
+	}
+	for _, s := range st.Shares {
+		if s.Name == share {
+			a.Served = s.Live && a.Service == "active" && a.Listening
+		}
+	}
+	for _, rf := range st.Refused {
+		if rf.Name == share {
+			a.Said = rf.Why
+			return a, nil
+		}
+	}
+	switch {
+	case a.Served:
+		a.Said = fmt.Sprintf("%s is served on 445", share)
+	case st.Mode == "found":
+		a.Said = fmt.Sprintf("%s is not served by the module: the configuration is still the hand-written one", share)
+	default:
+		a.Said = fmt.Sprintf("%s is not served now: Samba is %s, 445 listening: %v", share, a.Service, a.Listening)
+	}
+	return a, nil
+}
+
+// Reload has Samba read its configuration again.
+func (m *Machine) Reload(ctx context.Context) (any, error) {
+	if _, err := m.AsRoot(ctx, "", "smbcontrol", "smbd", "reload-config"); err != nil {
+		return nil, err
+	}
+	return m.Shares(), nil
+}
+
+// AdoptAnswer is what `adopt` answers.
+type AdoptAnswer struct {
+	DryRun bool     `json:"dry_run"`
+	Done   bool     `json:"done"`
+	Copy   string   `json:"copy,omitempty"`
+	Beside []string `json:"beside"`
+	Said   string   `json:"said"`
+}
+
+// AdoptWait is how long a confirmed adopt waits for the process to take over.
+var AdoptWait = 45 * time.Second
+
+// Adopt leaves a person's word for the process to take over, after a dry run that shows each hand-written share
+// beside its rendering. It refuses while a hand-written share has no counterpart.
+func (m *Machine) Adopt(confirm bool, why string) (AdoptAnswer, error) {
+	a := AdoptAnswer{DryRun: !confirm}
+	st, err := m.LastStatus()
+	if err != nil {
+		return a, err
+	}
+	if st.Mode == "adopted" {
+		return a, fmt.Errorf("the configuration is already the module's; nothing to take over")
+	}
+	served := map[string]Served{}
+	for _, s := range st.Shares {
+		served[s.Name] = s
+	}
+	var missing []string
+	for _, h := range st.Hand {
+		if h.Counterpart == "" {
+			missing = append(missing, fmt.Sprintf("%s (%s): %s", h.Name, h.Path, h.Why))
+			a.Beside = append(a.Beside, fmt.Sprintf("hand-written %s, %s, valid users %s → no counterpart", h.Name, h.Path, h.ValidUsers))
+			continue
+		}
+		s, ok := served[h.Counterpart]
+		if !ok {
+			missing = append(missing, fmt.Sprintf("%s: the setting's share %s is refused", h.Name, h.Counterpart))
+			continue
+		}
+		a.Beside = append(a.Beside, fmt.Sprintf("hand-written %s, %s, valid users %s, read only %v → the mesh's %s, %s, %s, valid users %s, every client as %s:%s",
+			h.Name, h.Path, h.ValidUsers, h.ReadOnly, s.Name, s.Path, s.Access, strings.Join(s.Users, " "), s.User, s.Group))
+	}
+	if len(missing) > 0 {
+		return a, fmt.Errorf("not taken over, so no share disappears: %s", strings.Join(missing, "; "))
+	}
+	plan := "keep a dated copy of the hand-written configuration beside it, write the mesh's own in its place once testparm passes it, have Samba read it, and stop NetBIOS"
+	if !confirm {
+		a.Said = "Dry run: would " + plan + "."
+		return a, nil
+	}
+	if why == "" {
+		return a, fmt.Errorf("say why: adopt is a person's act, and the why is kept with it")
+	}
+	raw, _ := json.MarshalIndent(Adoption{At: m.Now().UTC().Format(time.RFC3339), Why: why}, "", "  ")
+	if err := m.Write(AdoptFile, string(raw)+"\n", 0o644); err != nil {
+		return a, err
+	}
+	deadline := m.Now().Add(AdoptWait)
+	for {
+		if st, err := m.LastStatus(); err == nil && st.Mode == "adopted" && st.Written != "" {
+			a.Done = true
+			if st.Adopted != nil {
+				a.Copy = st.Adopted.Copy
+			}
+			a.Said = fmt.Sprintf("Did: %s. Why: %s", plan, why)
+			return a, nil
+		}
+		if !m.Now().Before(deadline) {
+			a.Said = "The word is left for the module's process, which has not taken over yet; read shares for why."
+			return a, nil
+		}
+		time.Sleep(2 * time.Second)
+	}
+}
+
+// HealthAnswer is the module's health: mesh-sdk's answer, with what was found.
+type HealthAnswer struct {
+	health.Answer
+	Found []string `json:"found,omitempty"`
+}
+
+// Health judges the shares.
+func (m *Machine) Health() HealthAnswer {
+	var found []string
+	if s := m.UnitState(Unit); s != "active" {
+		found = append(found, fmt.Sprintf("Samba (%s) is %s.", Unit, s))
+	}
+	st, err := m.LastStatus()
+	if err != nil {
+		found = append(found, err.Error()+".")
+		return HealthAnswer{Answer: health.Unhealthy(strings.Join(found, " ")), Found: found}
+	}
+	if at, err := time.Parse(time.RFC3339, st.At); err != nil || m.Now().Sub(at) > Stale {
+		found = append(found, "The module's process has not looked for five minutes.")
+	}
+	for _, p := range st.Problems {
+		found = append(found, sentence(p))
+	}
+	for _, r := range st.Refused {
+		found = append(found, r.Why)
+	}
+	if st.Mode == "adopted" {
+		for _, s := range st.Shares {
+			if !s.Live {
+				found = append(found, fmt.Sprintf("The share %s (%s) is not served by Samba.", s.Name, s.Path))
+			}
+		}
+	}
+	if len(found) > 0 {
+		return HealthAnswer{Answer: health.Unhealthy(strings.Join(found, " "), st.Waits...), Found: found}
+	}
+	if len(st.Waits) > 0 {
+		var why []string
+		for _, w := range st.Waits {
+			why = append(why, fmt.Sprintf("%s waits for %s.", sentence(w.Part), w.What))
+		}
+		return HealthAnswer{Answer: health.Waiting(strings.Join(why, " "), st.Waits...)}
+	}
+	if st.Mode == "found" {
+		return HealthAnswer{Answer: health.Healthy("Samba serves the hand-written configuration, kept as found; the module takes it over by node-smb-server.adopt, a person's act.")}
+	}
+	var parts []string
+	for _, s := range st.Shares {
+		parts = append(parts, s.Name)
+	}
+	return HealthAnswer{Answer: health.Healthy(fmt.Sprintf("Samba is active and serves %s on 445.", strings.Join(parts, ", ")))}
+}
+
+func sentence(s string) string {
+	s = strings.TrimSpace(s)
+	if s == "" {
+		return s
+	}
+	s = strings.ToUpper(s[:1]) + s[1:]
+	if !strings.HasSuffix(s, ".") {
+		s += "."
+	}
+	return s
+}
@@ -0,0 +1,5 @@
+module smbserver
+
+go 1.22
+
+require git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261010191001-33917f91ac3c
@@ -0,0 +1,8 @@
+git.novox.be/novox/mesh-sdk/go v0.1.6 h1:9qzdYONYbJdWcu6sxQcq9v1LI0JxcfkiKYkMUzJSkVQ=
+git.novox.be/novox/mesh-sdk/go v0.1.6/go.mod h1:GFuZUElBZ9A++mxgIKo97aXXo+kV0uJ/UkbhQPPIbrY=
+git.novox.be/novox/mesh-sdk/go v0.1.7 h1:C0sTQmtTiyYH7bnqZb7PusXnqA37gKuT7Nqjn9gG47w=
+git.novox.be/novox/mesh-sdk/go v0.1.7/go.mod h1:GFuZUElBZ9A++mxgIKo97aXXo+kV0uJ/UkbhQPPIbrY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261010190644-622b6b4f556d h1:BR8uwv4BqyLaBwITuLylrd9DRUnu0D5DjJw0RuQSXbk=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261010190644-622b6b4f556d/go.mod h1:GFuZUElBZ9A++mxgIKo97aXXo+kV0uJ/UkbhQPPIbrY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261010191001-33917f91ac3c h1:l5onJwoIeH8yE/PjVlEeoPyXBsHp2NQiWLllz2fwX7s=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261010191001-33917f91ac3c/go.mod h1:GFuZUElBZ9A++mxgIKo97aXXo+kV0uJ/UkbhQPPIbrY=
@@ -0,0 +1,144 @@
+{
+  "module": "smb-server",
+  "version": "1",
+  "upgrade": {
+    "policy": "record",
+    "why": "the folders the devices on the home network open: a build that breaks Samba's configuration leaves every device's share refused, and the gate on this one machine does not see the devices (hq ADR 0236, ADR 0341)"
+  },
+  "capabilities": [
+    "package-manager",
+    "service-manager"
+  ],
+  "claims": [
+    {
+      "name": "node-smb-server",
+      "scope": "node",
+      "serves": [
+        "shares",
+        "sessions",
+        "test",
+        "reload",
+        "adopt"
+      ]
+    }
+  ],
+  "tools": [
+    "smb_health"
+  ],
+  "settings": {
+    "shares": {
+      "kind": "preference",
+      "default": "none",
+      "why": "a machine serves no SMB share until its assignment names one: space-separated name=folder, each optionally :ro, one share per folder, every client acting as the folder's owner (hq ADR 0341)"
+    },
+    "users": {
+      "kind": "preference",
+      "default": "none",
+      "why": "the logins allowed on every share, space-separated; each login's password is the secret smb-password-<login>, and a login already in Samba's database whose secret is not given keeps its password (hq ADR 0341)"
+    }
+  },
+  "own-secrets": {
+    "smb-password-*": {
+      "path": "${dir:state}/smb-password-*.secret",
+      "issued-by": "outside"
+    }
+  },
+  "listens": [
+    {
+      "name": "smb",
+      "port": 445,
+      "protocol": "tcp",
+      "from": "mesh",
+      "fixed": true,
+      "why": "SMB 2.1 and later, on 445 alone: NetBIOS is off, so 137, 138 and 139 are never opened. The home server's assignment binds it with the reach local-network (hq ADR 0340, ADR 0341), so the devices on its own network reach it and nothing beyond"
+    }
+  ],
+  "resources": [
+    {
+      "id": "package",
+      "type": "package",
+      "package": "samba"
+    },
+    {
+      "id": "state",
+      "type": "directory",
+      "mode": "0700",
+      "place": "."
+    },
+    {
+      "id": "config-dir",
+      "type": "directory",
+      "path": "/etc/smb-server",
+      "mode": "0755"
+    },
+    {
+      "id": "run-dir",
+      "type": "directory",
+      "path": "/run/smb-server",
+      "mode": "0755"
+    },
+    {
+      "id": "lib-dir",
+      "type": "directory",
+      "path": "/var/lib/smb-server",
+      "mode": "0755"
+    },
+    {
+      "id": "adopt-dir",
+      "type": "directory",
+      "path": "/var/lib/smb-server/adopt",
+      "mode": "0755",
+      "owner": "${machine:account}"
+    },
+    {
+      "id": "config",
+      "type": "file",
+      "path": "/etc/smb-server/shares.conf",
+      "mode": "0644",
+      "content": "# Written by the mesh (module smb-server, novox/hq ADR 0341) from this machine's assignment.\n# Replaced on every push; change the settings, never this file.\n#\n# The shares: name=folder, or name=folder:ro, one share per folder. The users: the logins allowed. The\n# module's process serves each share with every client as the folder's owner, and writes Samba's\n# configuration only once a person adopted it (node-smb-server.adopt).\nshares=${setting:shares}\nusers=${setting:users}\npasswords=${dir:state}\n"
+    },
+    {
+      "id": "server",
+      "type": "service",
+      "unit": "smb.service",
+      "state": "running",
+      "boot": "enabled",
+      "health": {
+        "kind": "unit"
+      }
+    },
+    {
+      "id": "config-process",
+      "type": "process",
+      "name": "smb-server-config",
+      "artifact": "tools",
+      "run": [
+        "./smb-server",
+        "config"
+      ],
+      "health": {
+        "kind": "tool",
+        "tool": "smb_health",
+        "interval": "60s",
+        "timeout": "10s",
+        "looks": 2,
+        "grace": "90s"
+      }
+    }
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "tools",
+        "kind": "bundle",
+        "language": "go",
+        "system": "arch",
+        "from": "cmd/smb-server",
+        "binary": "smb-server",
+        "loads": [
+          "smb-server"
+        ]
+      }
+    ]
+  }
+}