Skip to content

set: fix byte order metadata for host-endian types and map data #353

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
anthonyrisinger wants to merge 1 commit into from
Closed

set: fix byte order metadata for host-endian types and map data #353

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
200 changes: 200 additions & 0 deletions nftables_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6495,6 +6495,206 @@ func TestVmap(t *testing.T) {
}
}

func TestSetByteOrder(t *testing.T) {
// Verify that KEYBYTEORDER and DATABYTEORDER userdata are emitted correctly
// for sets and maps with host-endian (NativeEndian) and big-endian types.
//
// Bug context: the library previously hard-coded KEYBYTEORDER=2 (big-endian)
// for all anonymous/constant/interval sets, ignoring the actual key type.
// Host-endian types like mark and ifname need KEYBYTEORDER=1 for correct
// display in nft list ruleset on little-endian systems.
// Additionally, DATABYTEORDER was never emitted for maps, causing map data
// values (like marks) to display byte-swapped.

tests := []struct {
name string
set nftables.Set
element []nftables.SetElement
// wantUserData is the expected NFTA_SET_USERDATA content (TLV encoded).
// NFTNL_UDATA_SET_KEYBYTEORDER (type=0): 1=host-endian, 2=big-endian
// NFTNL_UDATA_SET_DATABYTEORDER (type=1): 1=host-endian, 2=big-endian
wantUserData []byte
}{
{
name: "anonymous set with big-endian key (inet_service) emits KEYBYTEORDER=2",
set: nftables.Set{
Anonymous: true,
Constant: true,
KeyType: nftables.TypeInetService,
},
element: []nftables.SetElement{
{Key: binaryutil.BigEndian.PutUint16(80)},
},
// type=0 len=4 value=2 (KEYBYTEORDER=big-endian)
wantUserData: []byte{0x00, 0x04, 0x02, 0x00, 0x00, 0x00},
},
{
name: "anonymous set with host-endian key (mark) emits KEYBYTEORDER=1",
set: nftables.Set{
Anonymous: true,
Constant: true,
KeyType: nftables.TypeMark,
KeyByteOrder: binaryutil.NativeEndian,
},
element: []nftables.SetElement{
{Key: binaryutil.NativeEndian.PutUint32(1)},
},
// type=0 len=4 value=1 (KEYBYTEORDER=host-endian)
wantUserData: []byte{0x00, 0x04, 0x01, 0x00, 0x00, 0x00},
},
{
name: "named set with host-endian key emits KEYBYTEORDER=1",
set: nftables.Set{
Name: "test-marks",
KeyType: nftables.TypeMark,
KeyByteOrder: binaryutil.NativeEndian,
},
element: []nftables.SetElement{
{Key: binaryutil.NativeEndian.PutUint32(1)},
},
// type=0 len=4 value=1 (KEYBYTEORDER=host-endian)
wantUserData: []byte{0x00, 0x04, 0x01, 0x00, 0x00, 0x00},
},
{
name: "map with host-endian key and data emits both KEYBYTEORDER=1 and DATABYTEORDER=1",
set: nftables.Set{
Name: "test-map",
KeyType: nftables.TypeMark,
DataType: nftables.TypeMark,
KeyByteOrder: binaryutil.NativeEndian,
DataByteOrder: binaryutil.NativeEndian,
IsMap: true,
},
element: []nftables.SetElement{
{
Key: binaryutil.NativeEndian.PutUint32(1),
Val: binaryutil.NativeEndian.PutUint32(2),
},
},
// type=0 len=4 value=1 (KEYBYTEORDER=host), type=1 len=4 value=1 (DATABYTEORDER=host)
wantUserData: []byte{
0x00, 0x04, 0x01, 0x00, 0x00, 0x00,
0x01, 0x04, 0x01, 0x00, 0x00, 0x00,
},
},
{
name: "named map without explicit KeyByteOrder emits only DATABYTEORDER=1",
set: nftables.Set{
Name: "test-map",
KeyType: nftables.TypeInetService,
DataType: nftables.TypeMark,
DataByteOrder: binaryutil.NativeEndian,
IsMap: true,
},
element: []nftables.SetElement{
{
Key: binaryutil.BigEndian.PutUint16(22),
Val: binaryutil.NativeEndian.PutUint32(1),
},
},
// No KEYBYTEORDER (named, non-anonymous/interval, no explicit KeyByteOrder)
// type=1 len=4 value=1 (DATABYTEORDER=host)
wantUserData: []byte{
0x01, 0x04, 0x01, 0x00, 0x00, 0x00,
},
},
{
name: "anonymous map with big-endian key and host-endian data emits KEYBYTEORDER=2 and DATABYTEORDER=1",
set: nftables.Set{
Anonymous: true,
Constant: true,
KeyType: nftables.TypeInetService,
DataType: nftables.TypeMark,
DataByteOrder: binaryutil.NativeEndian,
IsMap: true,
},
element: []nftables.SetElement{
{
Key: binaryutil.BigEndian.PutUint16(22),
Val: binaryutil.NativeEndian.PutUint32(1),
},
},
// type=0 len=4 value=2 (KEYBYTEORDER=big), type=1 len=4 value=1 (DATABYTEORDER=host)
wantUserData: []byte{
0x00, 0x04, 0x02, 0x00, 0x00, 0x00,
0x01, 0x04, 0x01, 0x00, 0x00, 0x00,
},
},
}

for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
var captured []netlink.Message
c, err := nftables.New(nftables.WithTestDial(func(req []netlink.Message) ([]netlink.Message, error) {
captured = append(captured, req...)
return nil, nil
}))
if err != nil {
t.Fatal(err)
}

filter := c.AddTable(&nftables.Table{
Family: nftables.TableFamilyIPv4,
Name: "filter",
})

tt.set.Table = filter
if err := c.AddSet(&tt.set, tt.element); err != nil {
t.Fatalf("c.AddSet() failed: %v", err)
}

if err := c.Flush(); err != nil {
t.Fatalf("c.Flush() failed: %v", err)
}

// Find the NFTA_SET_USERDATA attribute (type 0x0d) in captured messages.
// The attribute uses standard netlink TLV: 2-byte length, 2-byte type, then data.
const nftaSetUserData = 0x0d
var foundUserData []byte
for _, msg := range captured {
b, err := msg.MarshalBinary()
if err != nil {
continue
}
// Skip netlink header (16 bytes) and nfgenmsg (4 bytes)
if len(b) < 20 {
continue
}
attrs := b[20:]
// Walk netlink attributes looking for type 0x0d
for len(attrs) >= 4 {
aLen := int(attrs[0]) | int(attrs[1])<<8
aType := int(attrs[2]) | int(attrs[3])<<8
if aLen < 4 || aLen > len(attrs) {
break
}
if aType == nftaSetUserData {
foundUserData = attrs[4:aLen]
break
}
// Align to 4 bytes
aLen = (aLen + 3) &^ 3
if aLen > len(attrs) {
break
}
attrs = attrs[aLen:]
}
if foundUserData != nil {
break
}
}

if foundUserData == nil {
t.Fatal("NFTA_SET_USERDATA attribute not found in captured messages")
}

if !bytes.Equal(foundUserData, tt.wantUserData) {
t.Errorf("userdata mismatch:\n got: %x\n want: %x", foundUserData, tt.wantUserData)
}
})
}
}

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
Expand Down
28 changes: 22 additions & 6 deletions set.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -267,8 +267,9 @@ type Set struct {
DataType SetDatatype
// Either host (binaryutil.NativeEndian) or big (binaryutil.BigEndian) endian as per
// https://git.netfilter.org/nftables/tree/include/datatype.h?id=d486c9e626405e829221b82d7355558005b26d8a#n109
KeyByteOrder binaryutil.ByteOrder
Comment string
KeyByteOrder binaryutil.ByteOrder
DataByteOrder binaryutil.ByteOrder
Comment string
// Indicates that the set has "size" specifier
Size uint32
}
Expand Down Expand Up @@ -716,12 +717,27 @@ func (cc *Conn) AddSet(s *Set, vals []SetElement) error {
// https://git.netfilter.org/libnftnl/tree/include/udata.h#n17
var userData []byte

if s.Anonymous || s.Constant || s.Interval || s.KeyByteOrder == binaryutil.BigEndian {
// Semantically useless - kept for binary compatability with nft
userData = userdata.AppendUint32(userData, userdata.NFTNL_UDATA_SET_KEYBYTEORDER, 2)
} else if s.KeyByteOrder == binaryutil.NativeEndian {
// Emit KEYBYTEORDER metadata matching nft C tool behavior (mnl.c:mnl_nft_set_add).
// Anonymous, constant, and interval sets always need byte order metadata.
// When KeyByteOrder is explicitly set, use it; otherwise default to big-endian
// for backward compatibility with prior library behavior.
if s.KeyByteOrder == binaryutil.NativeEndian {
// Per https://git.netfilter.org/nftables/tree/src/mnl.c?id=187c6d01d35722618c2711bbc49262c286472c8f#n1165
userData = userdata.AppendUint32(userData, userdata.NFTNL_UDATA_SET_KEYBYTEORDER, 1)
} else if s.Anonymous || s.Constant || s.Interval || s.KeyByteOrder == binaryutil.BigEndian {
userData = userdata.AppendUint32(userData, userdata.NFTNL_UDATA_SET_KEYBYTEORDER, 2)
}

// Emit DATABYTEORDER for maps, matching nft C tool behavior (mnl.c:mnl_nft_set_add).
// Without this, nft list ruleset cannot determine the data byte order and displays
// host-endian values (like marks) as byte-swapped on LE systems.
if s.IsMap {
switch s.DataByteOrder {
case binaryutil.NativeEndian:
userData = userdata.AppendUint32(userData, userdata.NFTNL_UDATA_SET_DATABYTEORDER, 1)
case binaryutil.BigEndian:
userData = userdata.AppendUint32(userData, userdata.NFTNL_UDATA_SET_DATABYTEORDER, 2)
}
}

if s.Interval && s.AutoMerge {
Expand Down