Add Connection tracking expression and test (#38)

Signed-off-by: Serguei Bezverkhi <sbezverk@cisco.com>

expr/ct.go

@@ -0,0 +1,60 @@
+// Copyright 2018 Google LLC. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package expr
+
+import (
+	"encoding/binary"
+
+	"github.com/google/nftables/binaryutil"
+	"github.com/mdlayher/netlink"
+	"golang.org/x/sys/unix"
+)
+
+// Ct defines type for NFT connection tracking
+type Ct struct {
+	Register uint32
+	Key      uint32
+}
+
+func (e *Ct) marshal() ([]byte, error) {
+	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_CT_KEY, Data: binaryutil.BigEndian.PutUint32(uint32(e.Key))},
+		{Type: unix.NFTA_CT_DREG, Data: binaryutil.BigEndian.PutUint32(e.Register)},
+	})
+	if err != nil {
+		return nil, err
+	}
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("ct\x00")},
+		{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data},
+	})
+}
+
+func (e *Ct) unmarshal(data []byte) error {
+	ad, err := netlink.NewAttributeDecoder(data)
+	if err != nil {
+		return err
+	}
+	ad.ByteOrder = binary.BigEndian
+	for ad.Next() {
+		switch ad.Type() {
+		case unix.NFTA_CT_KEY:
+			e.Key = ad.Uint32()
+		case unix.NFTA_CT_DREG:
+			e.Register = ad.Uint32()
+		}
+	}
+	return ad.Err()
+}

nftables_test.go

@@ -669,6 +669,59 @@ func TestTProxy(t *testing.T) {
 	}
 }
 
+func TestCt(t *testing.T) {
+	want := [][]byte{
+		// batch begin
+		[]byte("\x00\x00\x00\x0a"),
+		// sudo nft add rule ipv4table ipv4chain-5 ct mark 123 counter
+		[]byte("\x02\x00\x00\x00\x0e\x00\x01\x00\x69\x70\x76\x34\x74\x61\x62\x6c\x65\x00\x00\x00\x10\x00\x02\x00\x69\x70\x76\x34\x63\x68\x61\x69\x6e\x2d\x35\x00\x24\x00\x04\x80\x20\x00\x01\x80\x07\x00\x01\x00\x63\x74\x00\x00\x14\x00\x02\x80\x08\x00\x02\x00\x00\x00\x00\x03\x08\x00\x01\x00\x00\x00\x00\x01"),
+		// batch end
+		[]byte("\x00\x00\x00\x0a"),
+	}
+
+	c := &nftables.Conn{
+		TestDial: func(req []netlink.Message) ([]netlink.Message, error) {
+			for idx, msg := range req {
+				b, err := msg.MarshalBinary()
+				if err != nil {
+					t.Fatal(err)
+				}
+				if len(b) < 16 {
+					continue
+				}
+				b = b[16:]
+				if len(want) == 0 {
+					t.Errorf("no want entry for message %d: %x", idx, b)
+					continue
+				}
+				if got, want := b, want[0]; !bytes.Equal(got, want) {
+					t.Errorf("message %d: %s", idx, linediff(nfdump(got), nfdump(want)))
+				}
+				want = want[1:]
+			}
+			return req, nil
+		},
+	}
+
+	c.AddRule(&nftables.Rule{
+		Table: &nftables.Table{Name: "ipv4table", Family: nftables.TableFamilyIPv4},
+		Chain: &nftables.Chain{
+			Name: "ipv4chain-5",
+		},
+		Exprs: []expr.Any{
+			//	[ ct load mark => reg 1 ]
+			&expr.Ct{
+				Key:      unix.NFT_CT_MARK,
+				Register: 1,
+			},
+		},
+	})
+
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestAddRuleWithPosition(t *testing.T) {
 	want := [][]byte{
 		// batch begin