Feat firewall controller interface (#740)

Add a standard interface for the client firewall to support ACL.

client/firewall/firewall.go

@@ -0,0 +1,57 @@
+package firewall
+
+import (
+	"net"
+)
+
+// Rule abstraction should be implemented by each firewall manager
+//
+// Each firewall type for different OS can use different type
+// of the properties to hold data of the created rule
+type Rule interface {
+	// GetRuleID returns the rule id
+	GetRuleID() string
+}
+
+// Direction is the direction of the traffic
+type Direction int
+
+const (
+	// DirectionSrc is the direction of the traffic from the source
+	DirectionSrc Direction = iota
+	// DirectionDst is the direction of the traffic from the destination
+	DirectionDst
+)
+
+// Action is the action to be taken on a rule
+type Action int
+
+const (
+	// ActionAccept is the action to accept a packet
+	ActionAccept Action = iota
+	// ActionDrop is the action to drop a packet
+	ActionDrop
+)
+
+// Manager is the high level abstraction of a firewall manager
+//
+// It declares methods which handle actions required by the
+// Netbird client for ACL and routing functionality
+type Manager interface {
+	// AddFiltering rule to the firewall
+	AddFiltering(
+		ip net.IP,
+		port *Port,
+		direction Direction,
+		action Action,
+		comment string,
+	) (Rule, error)
+
+	// DeleteRule from the firewall by rule definition
+	DeleteRule(rule Rule) error
+
+	// Reset firewall to the default state
+	Reset() error
+
+	// TODO: migrate routemanager firewal actions to this interface
+}