From 9a6c96795b65e862a3293e85ce78de7d369cdd11 Mon Sep 17 00:00:00 2001 From: Alexis PIRES Date: Tue, 17 Dec 2019 21:54:26 +0100 Subject: [PATCH] Stateless NAT and notrack support (#82) --- expr/notrack.go | 38 +++++++++++ expr/payload.go | 74 ++++++++++++++++++--- nftables_test.go | 163 +++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 265 insertions(+), 10 deletions(-) create mode 100644 expr/notrack.go diff --git a/expr/notrack.go b/expr/notrack.go new file mode 100644 index 0000000..d7b28ae --- /dev/null +++ b/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() +} diff --git a/expr/payload.go b/expr/payload.go index d6a53d4..f7e7957 100644 --- a/expr/payload.go +++ b/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 { - DestRegister uint32 - Base PayloadBase - Offset uint32 - Len uint32 + 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{ - {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)}, - }) + + 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)}, + } + } + + 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() diff --git a/nftables_test.go b/nftables_test.go index a735e63..e3337ef 100644 --- a/nftables_test.go +++ b/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) + } +}