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// 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 userdata implements a TLV parser/serializer for libnftables-compatible comments
package userdata
import (
"bytes"
"encoding/binary"
)
type Type byte
// TLV type values are defined in:
// https://git.netfilter.org/iptables/tree/iptables/nft.c?id=73611d5582e72367a698faf1b5301c836e981465#n1659
const (
TypeComment Type = iota
TypeEbtablesPolicy
TypesCount
)
func Append(udata []byte, typ Type, data []byte) []byte {
udata = append(udata, byte(typ), byte(len(data)))
udata = append(udata, data...)
return udata
}
func Get(udata []byte, styp Type) []byte {
for {
if len(udata) < 2 {
break
}
typ := Type(udata[0])
length := int(udata[1])
data := udata[2 : 2+length]
if styp == typ {
return data
}
if len(udata) < 2+length {
break
} else {
udata = udata[2+length:]
}
}
return nil
}
func AppendUint32(udata []byte, typ Type, num uint32) []byte {
data := binary.LittleEndian.AppendUint32(nil, num)
return Append(udata, typ, data)
}
func GetUint32(udata []byte, typ Type) (uint32, bool) {
data := Get(udata, typ)
if data == nil {
return 0, false
}
return binary.LittleEndian.Uint32(data), true
}
func AppendString(udata []byte, typ Type, str string) []byte {
data := append([]byte(str), 0)
return Append(udata, typ, data)
}
func GetString(udata []byte, typ Type) (string, bool) {
data := Get(udata, typ)
if data == nil {
return "", false
}
data, _ = bytes.CutSuffix(data, []byte{0})
return string(data), true
}
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