chore(all): return concrete types, accept interfaces

- Remove exported interfaces unused locally
- Define interfaces to accept arguments
- Return concrete types, not interfaces

internal/netlink/rule.go

@@ -8,14 +8,6 @@ func NewRule() *Rule {
 	return netlink.NewRule()
 }
 
-var _ Ruler = (*NetLink)(nil)
-
-type Ruler interface {
-	RuleList(family int) (rules []netlink.Rule, err error)
-	RuleAdd(rule *netlink.Rule) error
-	RuleDel(rule *netlink.Rule) error
-}
-
 func (n *NetLink) RuleList(family int) (rules []Rule, err error) {
 	return netlink.RuleList(family)
 }