Quotas: reset one address, or give some back

POST /rules/{ref}/reset-quota takes an optional address (one entry of a
per-address quota starts again) and give (bytes taken off what was used,
one address's or everyone's, until the next reset). The firewall keeps
the adjustment for its next apply, which writes the new usage into the
ruleset; housecarld applies at once and saves the usage. hc rule
reset-quota --address/--give; Reset and Give back in the web UI, per
address in the usage dialog.

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

internal/nft/nft.go

@@ -422,6 +422,8 @@ type Firewall struct {
 	// restore is the quota usage saved before housecarld (or the machine)
 	// stopped, put back by the next apply.
 	restore *QuotaUsage
+	// adjust are quota changes the next apply makes (AdjustQuota).
+	adjust []QuotaAdjust
 	// flowDevs are the flowtable's devices in the ruleset in force, by
 	// name, with their interface index then (0: left out, missing).
 	flowDevs map[string]int
@@ -462,6 +464,52 @@ func (f *Firewall) RestoreQuotas(u *QuotaUsage) {
 	f.restore = u
 }
 
+// QuotaAdjust takes Give bytes off what a quota used (never below zero):
+// the named quota Name, or the entries of the per-address sets Name_v4
+// and Name_v6, Addr's alone if given (the set's key, as listed).
+type QuotaAdjust struct {
+	Name string
+	Addr string
+	Give int64
+}
+
+// AdjustQuota has the next apply change what a quota used.
+func (f *Firewall) AdjustQuota(a QuotaAdjust) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.adjust = append(f.adjust, a)
+}
+
+// apply takes what a's say off u. An entry with nothing left used is
+// dropped, so its quota starts again with its next packet.
+func (u *QuotaUsage) apply(adj []QuotaAdjust) {
+	less := func(used, give int64) int64 {
+		if give >= used {
+			return 0
+		}
+		return used - give
+	}
+	for _, a := range adj {
+		if used, ok := u.Quotas[a.Name]; ok {
+			u.Quotas[a.Name] = less(used, a.Give)
+		}
+		for _, set := range []string{a.Name + "_v4", a.Name + "_v6"} {
+			var kept []render.Element
+			for _, e := range u.QuotaSets[set] {
+				if a.Addr == "" || e.Addr == a.Addr {
+					e.Used = less(e.Used, a.Give)
+				}
+				if e.Used > 0 {
+					kept = append(kept, e)
+				}
+			}
+			if _, ok := u.QuotaSets[set]; ok {
+				u.QuotaSets[set] = kept
+			}
+		}
+	}
+}
+
 // ResetQuota starts a rule's quota again: the named quota, or the
 // per-address quota sets (both families).
 func (f *Firewall) ResetQuota(ctx context.Context, ruleID int64, perAddress bool) error {
@@ -531,6 +579,8 @@ func (f *Firewall) Apply(ctx context.Context, st *model.State) error {
 		usage = old.QuotaUsage
 	}
 	usage.merge(f.restore)
+	usage.apply(f.adjust)
+	f.adjust = nil
 	opt.Quotas, opt.QuotaSets = usage.Quotas, usage.QuotaSets
 	if old != nil {
 		opt.DeviceSets = old.DeviceSets

internal/nft/nft_test.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"reflect"
 	"sort"
 	"strings"
 	"testing"
@@ -186,6 +187,16 @@ func TestQuotasInContainer(t *testing.T) {
 	if t2, d2 := used(); t2 < total || d2 < dev {
 		t.Errorf("after a reload: total %d (was %d), per destination %d (was %d)", t2, total, d2, dev)
 	}
+	// Some given back, and one address started again, by the next apply.
+	total, dev = used()
+	fw.AdjustQuota(QuotaAdjust{Name: "quota_r1", Give: 1000})
+	fw.AdjustQuota(QuotaAdjust{Name: "quota_r2", Addr: "127.0.0.3", Give: 1 << 62})
+	if err := fw.Apply(ctx, st); err != nil {
+		t.Fatal(err)
+	}
+	if t2, d2 := used(); t2 > total-1000 || t2 < total-2000 || d2 != 0 {
+		t.Errorf("after giving back: total %d (was %d, gave 1000), per destination %d (was %d, reset)", t2, total, d2, dev)
+	}
 	// Reset by hand.
 	if err := fw.ResetQuota(ctx, 1, false); err != nil {
 		t.Fatal(err)
@@ -212,6 +223,23 @@ func TestQuotasInContainer(t *testing.T) {
 	}
 }
 
+// TestQuotaAdjust: giving back takes off what was used, never below
+// zero; an entry with nothing left goes.
+func TestQuotaAdjust(t *testing.T) {
+	u := QuotaUsage{Quotas: map[string]int64{"quota_r1": 5000, "quota_r9": 10},
+		QuotaSets: map[string][]render.Element{"quota_r2_v4": {{Addr: "10.0.0.1", Used: 3000}, {Addr: "10.0.0.2", Used: 4000}},
+			"quota_r2_v6": {{Addr: "2001:db8::", Used: 100}}}}
+	u.apply([]QuotaAdjust{{Name: "quota_r1", Give: 2000}, {Name: "quota_r9", Give: 2000}, {Name: "quota_r2", Addr: "10.0.0.2", Give: 1500},
+		{Name: "quota_r2", Give: 100}})
+	if u.Quotas["quota_r1"] != 3000 || u.Quotas["quota_r9"] != 0 {
+		t.Errorf("named: %v", u.Quotas)
+	}
+	want := map[string][]render.Element{"quota_r2_v4": {{Addr: "10.0.0.1", Used: 2900}, {Addr: "10.0.0.2", Used: 2400}}, "quota_r2_v6": nil}
+	if !reflect.DeepEqual(u.QuotaSets, want) {
+		t.Errorf("sets: %+v", u.QuotaSets)
+	}
+}
+
 // TestDeviceCountsInContainer: the per-device counters are read back and
 // survive a reload.
 func TestDeviceCountsInContainer(t *testing.T) {