diff --git a/expr/hash.go b/expr/hash.go new file mode 100644 index 0000000..08e0d3f --- /dev/null +++ b/expr/hash.go @@ -0,0 +1,87 @@ +// 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" +) + +type HashType uint32 + +const ( + HashTypeJenkins HashType = unix.NFT_HASH_JENKINS + HashTypeSym HashType = unix.NFT_HASH_SYM +) + +// Hash defines type for nftables internal hashing functions +type Hash struct { + SourceRegister uint32 + DestRegister uint32 + Length uint32 + Modulus uint32 + Seed uint32 + Offset uint32 + Type HashType +} + +func (e *Hash) marshal() ([]byte, error) { + data, err := netlink.MarshalAttributes([]netlink.Attribute{ + {Type: unix.NFTA_HASH_SREG, Data: binaryutil.BigEndian.PutUint32(uint32(e.SourceRegister))}, + {Type: unix.NFTA_HASH_DREG, Data: binaryutil.BigEndian.PutUint32(uint32(e.DestRegister))}, + {Type: unix.NFTA_HASH_LEN, Data: binaryutil.BigEndian.PutUint32(uint32(e.Length))}, + {Type: unix.NFTA_HASH_MODULUS, Data: binaryutil.BigEndian.PutUint32(uint32(e.Modulus))}, + {Type: unix.NFTA_HASH_SEED, Data: binaryutil.BigEndian.PutUint32(uint32(e.Seed))}, + {Type: unix.NFTA_HASH_OFFSET, Data: binaryutil.BigEndian.PutUint32(uint32(e.Offset))}, + {Type: unix.NFTA_HASH_TYPE, Data: binaryutil.BigEndian.PutUint32(uint32(e.Type))}, + }) + if err != nil { + return nil, err + } + return netlink.MarshalAttributes([]netlink.Attribute{ + {Type: unix.NFTA_EXPR_NAME, Data: []byte("hash\x00")}, + {Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: data}, + }) +} + +func (e *Hash) 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_HASH_SREG: + e.SourceRegister = ad.Uint32() + case unix.NFTA_HASH_DREG: + e.DestRegister = ad.Uint32() + case unix.NFTA_HASH_LEN: + e.Length = ad.Uint32() + case unix.NFTA_HASH_MODULUS: + e.Modulus = ad.Uint32() + case unix.NFTA_HASH_SEED: + e.Seed = ad.Uint32() + case unix.NFTA_HASH_OFFSET: + e.Offset = ad.Uint32() + case unix.NFTA_HASH_TYPE: + e.Type = HashType(ad.Uint32()) + } + } + return ad.Err() +} diff --git a/nftables_test.go b/nftables_test.go index 3283fbf..175c164 100644 --- a/nftables_test.go +++ b/nftables_test.go @@ -3044,3 +3044,98 @@ func TestVmap(t *testing.T) { } } } + +func TestJHash(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 mark set jhash ip saddr mod 2 seed 0xfeedcafe offset 1 + []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\xa8\x00\x04\x80\x34\x00\x01\x80\x0c\x00\x01\x00\x70\x61\x79\x6c\x6f\x61\x64\x00\x24\x00\x02\x80\x08\x00\x01\x00\x00\x00\x00\x02\x08\x00\x02\x00\x00\x00\x00\x01\x08\x00\x03\x00\x00\x00\x00\x0c\x08\x00\x04\x00\x00\x00\x00\x04\x4c\x00\x01\x80\x09\x00\x01\x00\x68\x61\x73\x68\x00\x00\x00\x00\x3c\x00\x02\x80\x08\x00\x01\x00\x00\x00\x00\x02\x08\x00\x02\x00\x00\x00\x00\x01\x08\x00\x03\x00\x00\x00\x00\x04\x08\x00\x04\x00\x00\x00\x00\x02\x08\x00\x05\x00\xfe\xed\xca\xfe\x08\x00\x06\x00\x00\x00\x00\x01\x08\x00\x07\x00\x00\x00\x00\x00\x24\x00\x01\x80\x09\x00\x01\x00\x6d\x65\x74\x61\x00\x00\x00\x00\x14\x00\x02\x80\x08\x00\x02\x00\x00\x00\x00\x03\x08\x00\x03\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.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{ + // [ payload load 4b @ network header + 12 => reg 2 ] + &expr.Payload{ + DestRegister: 2, + Base: expr.PayloadBaseNetworkHeader, + Offset: 12, + Len: 4, + }, + // [ hash reg 1 = jhash(reg 2, 4, 0xfeedcafe) % mod 2 offset 1 ] + &expr.Hash{ + SourceRegister: 2, + DestRegister: 1, + Length: 4, + Modulus: 2, + Seed: 4276996862, + Offset: 1, + Type: expr.HashTypeJenkins, + }, + // [ meta set mark with reg 1 ] + &expr.Meta{ + Key: expr.MetaKeyMARK, + SourceRegister: true, + Register: 1, + }, + }, + }) + + if err := c.Flush(); err != nil { + t.Fatal(err) + } +}