add notrack

expr/notrack.go

@@ -0,0 +1,39 @@
+// Copyright 2019 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 (
+	"github.com/mdlayher/netlink"
+	"golang.org/x/sys/unix"
+)
+
+type Notrack struct{}
+
+func (e *Notrack) marshal() ([]byte, error) {
+
+	return netlink.MarshalAttributes([]netlink.Attribute{
+		{Type: unix.NFTA_EXPR_NAME, Data: []byte("notrack\x00")},
+	})
+}
+
+func (e *Notrack) unmarshal(data []byte) error {
+	ad, err := netlink.NewAttributeDecoder(data)
+
+	if err != nil {
+		return err
+	}
+
+	return ad.Err()
+}

nftables_test.go

@@ -3817,3 +3817,77 @@ func TestDupWoDev(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestNotrack(t *testing.T) {
+	// The want byte sequences come from stracing nft(8), e.g.:
+	// strace -f -v -x -s 2048 -eraw=sendto nft add rule filter prerouting mark set jhash ip saddr mod 2
+	//
+	// The nft(8) command sequence was taken from:
+	// https://wiki.nftables.org/wiki-nftables/index.php/Quick_reference-nftables_in_10_minutes#Tcp
+	want := [][]byte{
+		// batch begin
+		[]byte("\x00\x00\x00\x0a"),
+		// nft flush ruleset
+		[]byte("\x00\x00\x00\x00"),
+		// nft add table ip filter
+		[]byte("\x02\x00\x00\x00\x0b\x00\x01\x00\x66\x69\x6c\x74\x65\x72\x00\x00\x08\x00\x02\x00\x00\x00\x00\x00"),
+		// nft add chain ip filter base-chain { type filter hook prerouting priority 0 \; }
+		[]byte("\x02\x00\x00\x00\x0b\x00\x01\x00\x66\x69\x6c\x74\x65\x72\x00\x00\x0f\x00\x03\x00\x62\x61\x73\x65\x2d\x63\x68\x61\x69\x6e\x00\x00\x14\x00\x04\x80\x08\x00\x01\x00\x00\x00\x00\x00\x08\x00\x02\x00\x00\x00\x00\x00\x0b\x00\x07\x00\x66\x69\x6c\x74\x65\x72\x00\x00"),
+		// nft add rule filter base_chain notrack
+		[]byte("\x02\x00\x00\x00\x0b\x00\x01\x00\x66\x69\x6c\x74\x65\x72\x00\x00\x0f\x00\x02\x00\x62\x61\x73\x65\x2d\x63\x68\x61\x69\x6e\x00\x00\x14\x00\x04\x80\x10\x00\x01\x80\x0c\x00\x01\x00\x6e\x6f\x74\x72\x61\x63\x6b\x00"),
+		// 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.FlushRuleset()
+
+	filter := c.AddTable(&nftables.Table{
+		Family: nftables.TableFamilyIPv4,
+		Name:   "filter",
+	})
+
+	prerouting := c.AddChain(&nftables.Chain{
+		Name:     "base-chain",
+		Table:    filter,
+		Type:     nftables.ChainTypeFilter,
+		Hooknum:  nftables.ChainHookPrerouting,
+		Priority: nftables.ChainPriorityFilter,
+	})
+
+	c.AddRule(&nftables.Rule{
+		Table: filter,
+		Chain: prerouting,
+		Exprs: []expr.Any{
+			// [ notrack ]
+			&expr.Notrack{},
+		},
+	})
+
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+}