[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/rule.go

@@ -1,18 +1,37 @@
 package iptables
 
-// Rule to handle management of rules
-type Rule struct {
-	ruleID    string
-	ipsetName string
+import "github.com/netbirdio/netbird/client/firewall/manager"
 
+// Rule to handle management of rules. Source set membership (when the
+// rule was built against a shared hash:net ipset) is encoded in specs;
+// DeleteFilterRule recovers it via findSets so the refcounter can drop
+// the right reference.
+type Rule struct {
+	id          manager.RuleID
 	specs       []string
 	mangleSpecs []string
-	ip          string
-	chain       string
-	v6          bool
+	// extraRules holds the rules beyond the first when the ipset
+	// fallback expands a multi-source rule into one rule per prefix.
+	extraRules []filterSpecs
+	chain      string
+	v6         bool
 }
 
-// GetRuleID returns the rule id
-func (r *Rule) ID() string {
-	return r.ruleID
+// filterSpecs is one installed iptables rule: its filter-table spec and
+// the paired mangle redirect-mark spec (nil for route rules or when the
+// mangle rule could not be added).
+type filterSpecs struct {
+	specs       []string
+	mangleSpecs []string
+}
+
+// allSpecs returns the spec pairs of every iptables rule backing this
+// Rule, the primary one first.
+func (r *Rule) allSpecs() []filterSpecs {
+	return append([]filterSpecs{{specs: r.specs, mangleSpecs: r.mangleSpecs}}, r.extraRules...)
+}
+
+// ID returns the rule id
+func (r *Rule) ID() manager.RuleID {
+	return r.id
 }