Address order: sequential, reverse or random, per subnet and pool

- Which never-used pool address a new client gets: sequential (the
  lowest, as before), reverse or random, in the settings, a subnet or
  a single pool (FIRST-LAST:ORDER). When no never-used address is left,
  the one free the longest, whatever the order; returning clients keep
  theirs.
- A subnet's pools are used in the order listed, or one at random
  weighted by its never-used addresses. Pools now keep the order they
  are given in (no more sorting by address).
- CLI --address-order and --pool-order; --add-pool of an existing range
  changes its order in place. Web UI: per-pool order and a move-up
  button, pool and address order on the subnet and settings pages.
- Kea's allocator: random is imported. Schema migration 5.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/web/static/assets/pages/settings.js

@@ -1,8 +1,8 @@
 // Settings: the default lease time, conflict checks, authority, and the
 // options every subnet gets.
-import { h, mount, input, field, checkbox, errorBox, readOnly } from "../ui.js";
+import { h, mount, input, field, checkbox, errorBox, readOnly, select } from "../ui.js";
 import { get, change, can } from "../api.js";
-import { optionsEditor, fmtSeconds, parseSeconds } from "../widgets.js";
+import { optionsEditor, fmtSeconds, parseSeconds, ADDRESS_ORDERS } from "../widgets.js";
 import { rerender } from "../app.js";
 
 export async function render(el) {
@@ -14,6 +14,7 @@ export async function render(el) {
   timeout.style.width = "7em";
   const hold = input({ value: fmtSeconds(s.decline_hold || 86400) });
   const auth = checkbox("Authoritative: refuse (NAK) requests for addresses that don't belong on the interface", !s.not_authoritative);
+  const order = select(ADDRESS_ORDERS, s.address_order || "sequential");
   const opts = await optionsEditor(s.options);
   const err = h("div");
   const save = async (dry) => {
@@ -22,7 +23,7 @@ export async function render(el) {
     if (lt === null || dh === null) { mount(err, h("div", { class: "msg err" }, "Write times as 12h, 1d or 30m.")); return; }
     try {
       const r = await change("PATCH", "/settings", { lease_time: lt, ping_check: ping.input.checked, ping_timeout_ms: parseInt(timeout.value, 10) || 0,
-        decline_hold: dh, not_authoritative: !auth.input.checked, options: opts.value() }, { query: dry ? { dry_run: 1 } : undefined });
+        decline_hold: dh, not_authoritative: !auth.input.checked, address_order: order.value, options: opts.value() }, { query: dry ? { dry_run: 1 } : undefined });
       if (!dry && r.applied) rerender();
     } catch (e) { mount(err, errorBox(e)); }
   };
@@ -35,6 +36,7 @@ export async function render(el) {
         field("Default lease time", lease, "How long clients keep an address unless a subnet says otherwise (12h, 1d). They renew halfway."),
         field("Options for every subnet", opts, "Usually domain-name-servers and domain-name; routers belong to each subnet."),
         field("Conflict check", h("div", null, ping, h("div", { class: "small" }, "wait ", timeout, " ms for an answer"))),
+        field("Address order", order, "Which address of a pool a new client gets: sequential (the lowest), reverse (the highest) or random. Only addresses never handed out count; when there are none left, the one free the longest. Subnets and pools can set their own."),
         field("Hold back for", hold, "How long an address a client declined (or one that answered a ping) isn't handed out."),
         field("Authority", auth, "Turn this off only if another DHCP server serves the same network.")),
       err,

internal/web/static/assets/pages/subnet.js

@@ -1,7 +1,7 @@
 // A subnet's page: its leases, its reservations and its settings.
 import { h, mount, badge, errorBox, confirmDialog, modal, input, debounce, readOnly, checkbox } from "../ui.js";
 import { get, change, can } from "../api.js";
-import { usageBar, subnetForm, fmtSeconds, subnetLabel } from "../widgets.js";
+import { usageBar, subnetForm, fmtSeconds, subnetLabel, poolText, orderText } from "../widgets.js";
 import { leasesTable } from "./leases.js";
 import { reservationsTable, reservationDialog } from "./reservations.js";
 import { rerender } from "../app.js";
@@ -19,7 +19,8 @@ export async function render(el, params) {
       h("div", { class: "grow" },
         h("h1", null, subnetLabel(s), " ", s.disabled ? badge("disabled", "off") : null),
         h("div", { class: "muted" }, "On ", h("span", { class: "mono" }, s.interface), " · pools ",
-          s.pools.length ? h("span", { class: "mono" }, s.pools.map((p) => p.start + "-" + p.end).join(", ")) : "none",
+          s.pools.length ? h("span", { class: "mono" }, s.pools.map(poolText).join(", ")) : "none",
+          orderText(s) ? " · " + orderText(s) : "",
           " · lease time ", s.lease_time ? fmtSeconds(s.lease_time) : "the default")),
       h("div", { class: "subnet-usage" }, usageBar(s.usage)),
       can("config", true) ? h("div", { class: "actions" }, h("button", {

internal/web/static/assets/pages/subnets.js

@@ -1,12 +1,12 @@
 // The subnets, and the New subnet dialog.
 import { h, mount, table, modal, errorBox, badge } from "../ui.js";
 import { get, change, can } from "../api.js";
-import { usageBar, subnetForm, fmtSeconds, subnetLabel } from "../widgets.js";
+import { usageBar, subnetForm, fmtSeconds, subnetLabel, poolText } from "../widgets.js";
 import { toggleSubnet } from "./subnet.js";
 
 export async function render(el, params, query) {
   const subnets = await get("/subnets");
-  const poolsText = (s) => s.pools.length ? s.pools.map((p) => p.start + "-" + p.end).join(", ") : "–";
+  const poolsText = (s) => s.pools.length ? s.pools.map(poolText).join(", ") : "–";
   mount(el,
     h("div", { class: "page-head" },
       h("div", { class: "grow" }, h("h1", null, "Subnets"),

internal/web/static/assets/style.css

@@ -342,6 +342,7 @@ button.chip:hover { background: var(--accent-soft); border-color: var(--accent);
 .pool-rows { display: flex; flex-direction: column; gap: 6px; }
 .pool-row { display: flex; gap: 6px; align-items: center; }
 .pool-row input { font-family: var(--mono); width: 18em; }
+.pool-row select { width: auto; }
 /* Activity: one line per message. */
 table.activity td { white-space: nowrap; }
 table.activity td.detail { white-space: normal; color: var(--muted); }

internal/web/static/assets/widgets.js

@@ -114,25 +114,51 @@ const examples = {
 // ---- pools
 
 // poolsEditor edits a subnet's pools; value() is ["first-last", ...].
+// Each pool has its own address order, or the subnet's; ↑ moves a pool up
+// (with pools in the order listed, the first is used first).
 export function poolsEditor(pools, placeholder) {
   const rows = h("div", { class: "pool-rows" });
   const box = h("div", null, rows);
-  const list = [];
-  const addRow = (v) => {
-    const inp = input({ value: v || "", placeholder: placeholder || "10.0.10.100-10.0.10.199" });
-    const row = h("div", { class: "pool-row" }, inp,
-      h("button", { type: "button", class: "small", title: "Remove this pool", onclick: () => { row.remove(); list.splice(list.indexOf(inp), 1); } }, "✕"));
-    list.push(inp);
-    rows.append(row);
-    return inp;
+  let list = [];
+  const addRow = (v, order) => {
+    const it = { inp: input({ value: v || "", placeholder: placeholder || "10.0.10.100-10.0.10.199" }) };
+    it.sel = select([["", "subnet's order"], ...ADDRESS_ORDERS.map((o) => [o, o])], order || "", { title: "The order addresses of this pool are handed out in" });
+    it.row = h("div", { class: "pool-row" }, it.inp, it.sel,
+      h("button", { type: "button", class: "small", title: "Move this pool up: it is used before the ones below", onclick: () => {
+        const i = list.indexOf(it);
+        if (i > 0) { list.splice(i, 1); list.splice(i - 1, 0, it); rows.insertBefore(it.row, list[i].row); }
+      } }, "↑"),
+      h("button", { type: "button", class: "small", title: "Remove this pool", onclick: () => { it.row.remove(); list = list.filter((x) => x !== it); } }, "✕"));
+    list.push(it);
+    rows.append(it.row);
+    return it.inp;
   };
-  for (const p of pools || []) addRow(p.start + "-" + p.end);
+  for (const p of pools || []) addRow(p.start + "-" + p.end, p.order);
   box.append(h("button", { type: "button", class: "small", onclick: () => addRow("").focus() }, "+ Add pool"));
-  box.value = () => list.map((i) => i.value.trim()).filter((s) => s !== "");
-  box.setFirst = (v) => { if (!list.length) addRow(v); else if (!list[0].value) list[0].value = v; };
+  box.value = () => list.map((it) => {
+    const v = it.inp.value.trim();
+    return v && it.sel.value && !v.includes(":") ? v + ":" + it.sel.value : v;
+  }).filter((s) => s !== "");
+  box.setFirst = (v) => { if (!list.length) addRow(v); else if (!list[0].inp.value) list[0].inp.value = v; };
   return box;
 }
 
+export const ADDRESS_ORDERS = ["sequential", "reverse", "random"];
+
+// poolText shows a pool, with its own address order.
+export function poolText(p) {
+  return p.start + "-" + p.end + (p.order ? " (" + p.order + ")" : "");
+}
+
+// orderText says how a subnet hands out new addresses, or "" for the
+// defaults.
+export function orderText(s) {
+  const parts = [];
+  if (s.pool_order === "random") parts.push("a pool at random");
+  if (s.address_order) parts.push(s.address_order + " addresses");
+  return parts.join(", ");
+}
+
 // ---- the subnet form
 
 // v4 helpers for suggestions.
@@ -163,6 +189,8 @@ export async function subnetForm(sn, settings) {
   const ifaceOther = input({ value: sn && !ifaceNames.includes(sn.interface) ? sn.interface : "", placeholder: "eth0.30 (one that comes up later)" });
   const prefix = input({ value: sn ? sn.prefix : "", placeholder: "10.0.10.0/24", class: "mono" });
   const pools = poolsEditor(sn ? sn.pools : []);
+  const poolOrder = select([["", "in the order listed"], ["random", "at random (weighted by free addresses)"]], sn ? sn.pool_order || "" : "");
+  const addrOrder = select([["", "the settings' (" + (settings.address_order || "sequential") + ")"], ...ADDRESS_ORDERS.map((o) => [o, o])], sn ? sn.address_order || "" : "");
   const lease = input({ value: sn ? fmtSeconds(sn.lease_time) : "", placeholder: "the default: " + fmtSeconds(settings.lease_time || 43200) });
   const opts = await optionsEditor(sn ? sn.options : [], settings.options);
   const comment = input({ value: sn ? sn.comment : "" });
@@ -192,6 +220,8 @@ export async function subnetForm(sn, settings) {
     field("Interface", h("div", null, ifaceSel, " ", ifaceOther)), ifaceHint,
     field("Network", prefix, "The subnet's prefix; the mask clients get comes from it."),
     field("Pools", pools, "Ranges handed out to any client: FIRST-LAST, or a prefix. Reserved addresses inside a pool are never handed out to others."),
+    field("Pool order", poolOrder, "Which pool a new client's address comes from."),
+    field("Address order", addrOrder, "Which address of a pool: sequential (the lowest), reverse (the highest) or random. A pool can set its own. New clients get an address never handed out before; when there are none, the one free the longest. Returning clients keep theirs."),
     field("Lease time", lease, "12h, 1d, 30m; empty for the default."),
     field("Options", opts),
     field("Comment", comment),
@@ -199,7 +229,7 @@ export async function subnetForm(sn, settings) {
   grid.values = () => {
     const lt = parseSeconds(lease.value);
     if (lt === null) throw new Error("Lease time: write it as 12h, 1d or 30m");
-    const v = { name: name.value.trim(), interface: ifaceValue(), prefix: prefix.value.trim(), pools: pools.value(), lease_time: lt, options: opts.value(), comment: comment.value };
+    const v = { name: name.value.trim(), interface: ifaceValue(), prefix: prefix.value.trim(), pools: pools.value(), pool_order: poolOrder.value || "listed", address_order: addrOrder.value || "default", lease_time: lt, options: opts.value(), comment: comment.value };
     if (sn) v.disabled = disabled.input.checked;
     return v;
   };