[client] Unify peer and route ACL filtering with multi-source rules (#6322)

* Unify peer and route ACL filtering with multi-source peer rules

* Remove partial userspace firewall mode and open foreign chains via a table-less allower

* Snapshot iptables rule maps before persisting state

* Scope userspace firewall wildcard source rules per address family

* Install nftables peer filter and mangle rules in a single transaction

* Share the iptables jump rule spec between install and cleanup

* Fix legacy ACL source wildcard and keep rollback tracking on delete failure

* Fix CI: recognize multi-value port set lookups in tests and correct PeerIP lint suppression

* Fall back to per-prefix filter rules when ipset is unavailable

* Annotate legacy PeerIP usages in ACL tests and fix import formatting

* Keep firewall rule bookkeeping in step with the kernel on replace and teardown

* Release the routing reference when the route manager shuts down

* Keep set references and rule tracking consistent when a routing rule fails

client/firewall/iptables/ipset_linux.go

@@ -0,0 +1,131 @@
+//go:build !android
+
+package iptables
+
+import (
+	"fmt"
+	"net/netip"
+
+	"github.com/google/uuid"
+	"github.com/hashicorp/go-multierror"
+	"github.com/lrh3321/ipset-go"
+	log "github.com/sirupsen/logrus"
+
+	nberrors "github.com/netbirdio/netbird/client/errors"
+	firewall "github.com/netbirdio/netbird/client/firewall/manager"
+)
+
+// probeIPSetSupport checks whether the kernel can create the ipset type
+// used for source and destination matches. On kernels lacking the
+// required ipset hash module, set creation fails (e.g. "invalid
+// argument"), which would otherwise fail every multi-source rule and
+// leave traffic the policy permits blocked by the catch-all drop. When
+// unsupported, multi-source rules fall back to one rule per prefix.
+func (r *family) probeIPSetSupport() bool {
+	// Use a unique name so concurrent processes don't collide and we only ever
+	// destroy the set we created ourselves. ipset names are limited to 31 chars,
+	// so use a short random suffix.
+	probeName := "nb-probe-" + uuid.New().String()[:8]
+
+	if err := r.createIPSet(probeName); err != nil {
+		log.Warnf("ipset is not available (failed to create probe set: %v); "+
+			"falling back to per-IP iptables ACL rules. Ensure the kernel provides "+
+			"the ipset hash:net module (ip_set_hash_net) for better performance with large rule sets", err)
+		return false
+	}
+
+	if err := r.destroyIPSet(probeName); err != nil {
+		log.Debugf("destroy ipset probe set %q: %v", probeName, err)
+	}
+
+	return true
+}
+
+func (r *family) createIpSet(setName string, sources []netip.Prefix) error {
+	if err := r.createIPSet(setName); err != nil {
+		return fmt.Errorf("create set %s: %w", setName, err)
+	}
+
+	for _, prefix := range sources {
+		if err := r.addPrefixToIPSet(setName, prefix); err != nil {
+			// The refcounter records nothing when this callback errors,
+			// so destroy the set or it leaks in the kernel. A partial
+			// source set would also fail-open for deny rules, so the
+			// rule must fail rather than install with a missing source.
+			if derr := r.destroyIPSet(setName); derr != nil {
+				log.Warnf("rollback ipset %s after add failure: %v", setName, derr)
+			}
+			return fmt.Errorf("add element to set %s: %w", setName, err)
+		}
+	}
+
+	return nil
+}
+
+func (r *family) deleteIpSet(setName string) error {
+	if err := r.destroyIPSet(setName); err != nil {
+		return fmt.Errorf("destroy set %s: %w", setName, err)
+	}
+
+	log.Debugf("deleted unused ipset %s", setName)
+	return nil
+}
+
+func (r *family) UpdateSet(set firewall.Set, prefixes []netip.Prefix) error {
+	name := r.ipsetName(set.HashedName())
+	var merr *multierror.Error
+	for _, prefix := range prefixes {
+		if err := r.addPrefixToIPSet(name, prefix); err != nil {
+			merr = multierror.Append(merr, fmt.Errorf("add prefix to ipset: %w", err))
+		}
+	}
+	if merr == nil {
+		log.Debugf("updated set %s with prefixes %v", name, prefixes)
+	}
+
+	return nberrors.FormatErrorOrNil(merr)
+}
+
+func (r *family) ipsetName(name string) string {
+	if r.v6 {
+		return name + "-v6"
+	}
+	return name
+}
+
+func (r *family) createIPSet(name string) error {
+	opts := ipset.CreateOptions{
+		Replace: true,
+	}
+	if r.v6 {
+		opts.Family = ipset.FamilyIPV6
+	}
+
+	if err := ipset.Create(name, ipset.TypeHashNet, opts); err != nil {
+		return fmt.Errorf("create ipset %s: %w", name, err)
+	}
+
+	log.Debugf("created ipset %s with type hash:net", name)
+	return nil
+}
+
+func (r *family) addPrefixToIPSet(name string, prefix netip.Prefix) error {
+	addr := prefix.Addr()
+	ip := addr.AsSlice()
+
+	entry := &ipset.Entry{
+		IP:      ip,
+		CIDR:    uint8(prefix.Bits()),
+		Replace: true,
+	}
+
+	if err := ipset.Add(name, entry); err != nil {
+		return fmt.Errorf("add prefix to ipset %s: %w", name, err)
+	}
+
+	return nil
+}
+
+func (r *family) destroyIPSet(name string) error {
+	return ipset.Destroy(name)
+}