Add Chain API for managing nftables chains, including Add, Create, Delete, Clear, and Rename operations.

chain/hook.go

@@ -0,0 +1,36 @@
+package chain
+
+import "fmt"
+
+type Hook int8
+
+const (
+	HookInput Hook = iota
+	HookOutput
+	HookForward
+	HookPrerouting
+	HookPostrouting
+	HookIngress
+	HookEgress
+)
+
+func (h Hook) String() string {
+	switch h {
+	case HookInput:
+		return "input"
+	case HookOutput:
+		return "output"
+	case HookForward:
+		return "forward"
+	case HookPrerouting:
+		return "prerouting"
+	case HookPostrouting:
+		return "postrouting"
+	case HookIngress:
+		return "ingress"
+	case HookEgress:
+		return "egress"
+	default:
+		return fmt.Sprintf("unknown hook %d", h)
+	}
+}

chain/policy.go

@@ -0,0 +1,21 @@
+package chain
+
+import "fmt"
+
+type Policy int8
+
+const (
+	PolicyAccept Policy = iota + 1
+	PolicyDrop
+)
+
+func (p Policy) String() string {
+	switch p {
+	case PolicyAccept:
+		return "accept"
+	case PolicyDrop:
+		return "drop"
+	default:
+		return fmt.Sprintf("unknown policy %d", p)
+	}
+}

chain/type.go

@@ -0,0 +1,68 @@
+package chain
+
+import (
+	"fmt"
+	"strconv"
+)
+
+type ChainOptions interface {
+	String() string
+}
+
+type Type int8
+
+const (
+	TypeNone Type = iota
+	TypeFilter
+	TypeNat
+	TypeRoute
+)
+
+func (t Type) String() string {
+	switch t {
+	case TypeNone:
+		return ""
+	case TypeFilter:
+		return "filter"
+	case TypeNat:
+		return "inet"
+	case TypeRoute:
+		return "nat"
+	default:
+		return fmt.Sprintf("unknown type %d", t)
+	}
+}
+
+type BaseChainOptions struct {
+	Type     Type
+	Hook     Hook
+	Priority int32
+	Policy   Policy
+	Device   string
+}
+
+func (b BaseChainOptions) String() string {
+	if b.Type == TypeNone {
+		return ""
+	}
+
+	device := ""
+	if b.Hook == HookEgress || b.Hook == HookIngress {
+		if b.Device != "" {
+			device = " device " + b.Device + " "
+		}
+	}
+
+	policy := ""
+	if b.Type == TypeFilter {
+		policy = "policy " + b.Policy.String() + " ; "
+	}
+
+	return "{ type " + b.Type.String() + " hook " + b.Hook.String() + " " + device + " priority " + strconv.Itoa(int(b.Priority)) + " ; " + policy + " }"
+}
+
+func NewBaseChainOptions(t Type) BaseChainOptions {
+	return BaseChainOptions{
+		Type: t,
+	}
+}