Fix/acl for forward (#1305)

Fix ACL on routed traffic and code refactor

client/firewall/manager/firewall.go

@@ -0,0 +1,88 @@
+package manager
+
+import (
+	"fmt"
+	"net"
+)
+
+const (
+	NatFormat          = "netbird-nat-%s"
+	ForwardingFormat   = "netbird-fwd-%s"
+	InNatFormat        = "netbird-nat-in-%s"
+	InForwardingFormat = "netbird-fwd-in-%s"
+)
+
+// 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
+}
+
+// RuleDirection is the traffic direction which a rule is applied
+type RuleDirection int
+
+const (
+	// RuleDirectionIN applies to filters that handlers incoming traffic
+	RuleDirectionIN RuleDirection = iota
+	// RuleDirectionOUT applies to filters that handlers outgoing traffic
+	RuleDirectionOUT
+)
+
+// 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 {
+	// AllowNetbird allows netbird interface traffic
+	AllowNetbird() error
+
+	// AddFiltering rule to the firewall
+	//
+	// If comment argument is empty firewall manager should set
+	// rule ID as comment for the rule
+	AddFiltering(
+		ip net.IP,
+		proto Protocol,
+		sPort *Port,
+		dPort *Port,
+		direction RuleDirection,
+		action Action,
+		ipsetName string,
+		comment string,
+	) ([]Rule, error)
+
+	// DeleteRule from the firewall by rule definition
+	DeleteRule(rule Rule) error
+
+	// IsServerRouteSupported returns true if the firewall supports server side routing operations
+	IsServerRouteSupported() bool
+
+	// InsertRoutingRules inserts a routing firewall rule
+	InsertRoutingRules(pair RouterPair) error
+
+	// RemoveRoutingRules removes a routing firewall rule
+	RemoveRoutingRules(pair RouterPair) error
+
+	// Reset firewall to the default state
+	Reset() error
+
+	// Flush the changes to firewall controller
+	Flush() error
+}
+
+func GenKey(format string, input string) string {
+	return fmt.Sprintf(format, input)
+}