Fix/acl for forward (#1305)

Fix ACL on routed traffic and code refactor

client/firewall/create_linux.go

@@ -0,0 +1,107 @@
+//go:build !android
+
+package firewall
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/coreos/go-iptables/iptables"
+	"github.com/google/nftables"
+	log "github.com/sirupsen/logrus"
+
+	nbiptables "github.com/netbirdio/netbird/client/firewall/iptables"
+	firewall "github.com/netbirdio/netbird/client/firewall/manager"
+	nbnftables "github.com/netbirdio/netbird/client/firewall/nftables"
+	"github.com/netbirdio/netbird/client/firewall/uspfilter"
+)
+
+const (
+	// UNKNOWN is the default value for the firewall type for unknown firewall type
+	UNKNOWN FWType = iota
+	// IPTABLES is the value for the iptables firewall type
+	IPTABLES
+	// NFTABLES is the value for the nftables firewall type
+	NFTABLES
+)
+
+// SKIP_NFTABLES_ENV is the environment variable to skip nftables check
+const SKIP_NFTABLES_ENV = "NB_SKIP_NFTABLES_CHECK"
+
+// FWType is the type for the firewall type
+type FWType int
+
+func NewFirewall(context context.Context, iface IFaceMapper) (firewall.Manager, error) {
+	// on the linux system we try to user nftables or iptables
+	// in any case, because we need to allow netbird interface traffic
+	// so we use AllowNetbird traffic from these firewall managers
+	// for the userspace packet filtering firewall
+	var fm firewall.Manager
+	var errFw error
+
+	switch check() {
+	case IPTABLES:
+		log.Debug("creating an iptables firewall manager")
+		fm, errFw = nbiptables.Create(context, iface)
+		if errFw != nil {
+			log.Errorf("failed to create iptables manager: %s", errFw)
+		}
+	case NFTABLES:
+		log.Debug("creating an nftables firewall manager")
+		fm, errFw = nbnftables.Create(context, iface)
+		if errFw != nil {
+			log.Errorf("failed to create nftables manager: %s", errFw)
+		}
+	default:
+		errFw = fmt.Errorf("no firewall manager found")
+		log.Debug("no firewall manager found, try to use userspace packet filtering firewall")
+	}
+
+	if iface.IsUserspaceBind() {
+		var errUsp error
+		if errFw == nil {
+			fm, errUsp = uspfilter.CreateWithNativeFirewall(iface, fm)
+		} else {
+			fm, errUsp = uspfilter.Create(iface)
+		}
+		if errUsp != nil {
+			log.Debugf("failed to create userspace filtering firewall: %s", errUsp)
+			return nil, errUsp
+		}
+
+		if err := fm.AllowNetbird(); err != nil {
+			log.Errorf("failed to allow netbird interface traffic: %v", err)
+		}
+		return fm, nil
+	}
+
+	if errFw != nil {
+		return nil, errFw
+	}
+
+	return fm, nil
+}
+
+// check returns the firewall type based on common lib checks. It returns UNKNOWN if no firewall is found.
+func check() FWType {
+	nf := nftables.Conn{}
+	if _, err := nf.ListChains(); err == nil && os.Getenv(SKIP_NFTABLES_ENV) != "true" {
+		return NFTABLES
+	}
+
+	ip, err := iptables.NewWithProtocol(iptables.ProtocolIPv4)
+	if err != nil {
+		return UNKNOWN
+	}
+	if isIptablesClientAvailable(ip) {
+		return IPTABLES
+	}
+
+	return UNKNOWN
+}
+
+func isIptablesClientAvailable(client *iptables.IPTables) bool {
+	_, err := client.ListChains("filter")
+	return err == nil
+}