Stateless NAT and notrack support (#82)

expr/notrack.go

@@ -0,0 +1,38 @@
+// 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()
+}

expr/payload.go

@@ -23,6 +23,8 @@ import (
 )
 
 type PayloadBase uint32
+type PayloadCsumType uint32
+type PayloadOperationType uint32
 
 // Possible PayloadBase values.
 const (
@@ -31,20 +33,64 @@ const (
 	PayloadBaseTransportHeader PayloadBase = unix.NFT_PAYLOAD_TRANSPORT_HEADER
 )
 
+// Possible PayloadCsumType values.
+const (
+	CsumTypeNone PayloadCsumType = unix.NFT_PAYLOAD_CSUM_NONE
+	CsumTypeInet PayloadCsumType = unix.NFT_PAYLOAD_CSUM_INET
+)
+
+// Possible PayloadOperationType values.
+const (
+	PayloadLoad PayloadOperationType = iota
+	PayloadWrite
+)
+
 type Payload struct {
+	OperationType  PayloadOperationType
 	DestRegister   uint32
+	SourceRegister uint32
 	Base           PayloadBase
 	Offset         uint32
 	Len            uint32
+	CsumType       PayloadCsumType
+	CsumOffset     uint32
+	CsumFlags      uint32
 }
 
 func (e *Payload) marshal() ([]byte, error) {
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+
+	var attrs []netlink.Attribute
+
+	if e.OperationType == PayloadWrite {
+		attrs = []netlink.Attribute{
+			{Type: unix.NFTA_PAYLOAD_SREG, Data: binaryutil.BigEndian.PutUint32(e.SourceRegister)},
+		}
+	} else {
+		attrs = []netlink.Attribute{
 			{Type: unix.NFTA_PAYLOAD_DREG, Data: binaryutil.BigEndian.PutUint32(e.DestRegister)},
-		{Type: unix.NFTA_PAYLOAD_BASE, Data: binaryutil.BigEndian.PutUint32(uint32(e.Base))},
+		}
-		{Type: unix.NFTA_PAYLOAD_OFFSET, Data: binaryutil.BigEndian.PutUint32(e.Offset)},
+	}
-		{Type: unix.NFTA_PAYLOAD_LEN, Data: binaryutil.BigEndian.PutUint32(e.Len)},
+
-	})
+	attrs = append(attrs,
+		netlink.Attribute{Type: unix.NFTA_PAYLOAD_BASE, Data: binaryutil.BigEndian.PutUint32(uint32(e.Base))},
+		netlink.Attribute{Type: unix.NFTA_PAYLOAD_OFFSET, Data: binaryutil.BigEndian.PutUint32(e.Offset)},
+		netlink.Attribute{Type: unix.NFTA_PAYLOAD_LEN, Data: binaryutil.BigEndian.PutUint32(e.Len)},
+	)
+
+	if e.CsumType > 0 {
+		attrs = append(attrs,
+			netlink.Attribute{Type: unix.NFTA_PAYLOAD_CSUM_TYPE, Data: binaryutil.BigEndian.PutUint32(uint32(e.CsumType))},
+			netlink.Attribute{Type: unix.NFTA_PAYLOAD_CSUM_OFFSET, Data: binaryutil.BigEndian.PutUint32(uint32(e.CsumOffset))},
+		)
+		if e.CsumFlags > 0 {
+			attrs = append(attrs,
+				netlink.Attribute{Type: unix.NFTA_PAYLOAD_CSUM_FLAGS, Data: binaryutil.BigEndian.PutUint32(e.CsumFlags)},
+			)
+		}
+	}
+
+	data, err := netlink.MarshalAttributes(attrs)
+
 	if err != nil {
 		return nil, err
 	}
@@ -64,12 +110,20 @@ func (e *Payload) unmarshal(data []byte) error {
 		switch ad.Type() {
 		case unix.NFTA_PAYLOAD_DREG:
 			e.DestRegister = ad.Uint32()
+		case unix.NFTA_PAYLOAD_SREG:
+			e.SourceRegister = ad.Uint32()
 		case unix.NFTA_PAYLOAD_BASE:
 			e.Base = PayloadBase(ad.Uint32())
 		case unix.NFTA_PAYLOAD_OFFSET:
 			e.Offset = ad.Uint32()
 		case unix.NFTA_PAYLOAD_LEN:
 			e.Len = ad.Uint32()
+		case unix.NFTA_PAYLOAD_CSUM_TYPE:
+			e.CsumType = PayloadCsumType(ad.Uint32())
+		case unix.NFTA_PAYLOAD_CSUM_OFFSET:
+			e.CsumOffset = ad.Uint32()
+		case unix.NFTA_PAYLOAD_CSUM_FLAGS:
+			e.CsumFlags = ad.Uint32()
 		}
 	}
 	return ad.Err()

nftables_test.go

@@ -3817,3 +3817,166 @@ 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)
+	}
+}
+
+func TestStatelessNAT(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 ip filter base-chain ip daddr set 192.168.1.1 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\x8c\x00\x04\x80\x2c\x00\x01\x80\x0e\x00\x01\x00\x69\x6d\x6d\x65\x64\x69\x61\x74\x65\x00\x00\x00\x18\x00\x02\x80\x08\x00\x01\x00\x00\x00\x00\x01\x0c\x00\x02\x80\x08\x00\x01\x00\xc0\xa8\x01\x01\x4c\x00\x01\x80\x0c\x00\x01\x00\x70\x61\x79\x6c\x6f\x61\x64\x00\x3c\x00\x02\x80\x08\x00\x05\x00\x00\x00\x00\x01\x08\x00\x02\x00\x00\x00\x00\x01\x08\x00\x03\x00\x00\x00\x00\x10\x08\x00\x04\x00\x00\x00\x00\x04\x08\x00\x06\x00\x00\x00\x00\x01\x08\x00\x07\x00\x00\x00\x00\x0a\x08\x00\x08\x00\x00\x00\x00\x01\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",
+	})
+
+	forward := 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: forward,
+		Exprs: []expr.Any{
+			&expr.Immediate{
+				Register: 1,
+				Data:     net.ParseIP("192.168.1.1").To4(),
+			},
+			// [ payload write reg 1 => 4b @ network header + 16 csum_type 1 csum_off 10 csum_flags 0x1 ]
+			&expr.Payload{
+				OperationType:  expr.PayloadWrite,
+				SourceRegister: 1,
+				Base:           expr.PayloadBaseNetworkHeader,
+				Offset:         16,
+				Len:            4,
+				CsumType:       expr.CsumTypeInet,
+				CsumOffset:     10,
+				CsumFlags:      unix.NFT_PAYLOAD_L4CSUM_PSEUDOHDR,
+			},
+			// [ notrack ]
+			&expr.Notrack{},
+		},
+	})
+
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+}