2018-05-24 23:47:16 -05:00
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// Copyright 2018 Google LLC. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package expr provides nftables rule expressions.
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package expr
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import (
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"encoding/binary"
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"fmt"
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"github.com/google/nftables/binaryutil"
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"github.com/mdlayher/netlink"
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"golang.org/x/sys/unix"
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)
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// Marshal serializes the specified expression into a byte slice.
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func Marshal(e Any) ([]byte, error) {
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return e.marshal()
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}
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// Unmarshal fills an expression from the specified byte slice.
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func Unmarshal(data []byte, e Any) error {
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return e.unmarshal(data)
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}
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// Any is an interface implemented by any expression type.
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type Any interface {
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marshal() ([]byte, error)
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unmarshal([]byte) error
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}
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// MetaKey specifies which piece of meta information should be loaded. See also
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// https://wiki.nftables.org/wiki-nftables/index.php/Matching_packet_metainformation
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type MetaKey uint32
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// Possible MetaKey values.
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const (
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MetaKeyLEN MetaKey = unix.NFT_META_LEN
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MetaKeyPROTOCOL MetaKey = unix.NFT_META_PROTOCOL
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MetaKeyPRIORITY MetaKey = unix.NFT_META_PRIORITY
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MetaKeyMARK MetaKey = unix.NFT_META_MARK
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MetaKeyIIF MetaKey = unix.NFT_META_IIF
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MetaKeyOIF MetaKey = unix.NFT_META_OIF
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MetaKeyIIFNAME MetaKey = unix.NFT_META_IIFNAME
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MetaKeyOIFNAME MetaKey = unix.NFT_META_OIFNAME
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MetaKeyIIFTYPE MetaKey = unix.NFT_META_IIFTYPE
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MetaKeyOIFTYPE MetaKey = unix.NFT_META_OIFTYPE
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MetaKeySKUID MetaKey = unix.NFT_META_SKUID
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MetaKeySKGID MetaKey = unix.NFT_META_SKGID
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MetaKeyNFTRACE MetaKey = unix.NFT_META_NFTRACE
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MetaKeyRTCLASSID MetaKey = unix.NFT_META_RTCLASSID
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MetaKeySECMARK MetaKey = unix.NFT_META_SECMARK
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MetaKeyNFPROTO MetaKey = unix.NFT_META_NFPROTO
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MetaKeyL4PROTO MetaKey = unix.NFT_META_L4PROTO
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MetaKeyBRIIIFNAME MetaKey = unix.NFT_META_BRI_IIFNAME
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MetaKeyBRIOIFNAME MetaKey = unix.NFT_META_BRI_OIFNAME
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MetaKeyPKTTYPE MetaKey = unix.NFT_META_PKTTYPE
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MetaKeyCPU MetaKey = unix.NFT_META_CPU
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MetaKeyIIFGROUP MetaKey = unix.NFT_META_IIFGROUP
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MetaKeyOIFGROUP MetaKey = unix.NFT_META_OIFGROUP
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MetaKeyCGROUP MetaKey = unix.NFT_META_CGROUP
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MetaKeyPRANDOM MetaKey = unix.NFT_META_PRANDOM
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)
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// Meta loads packet meta information for later comparisons. See also
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// https://wiki.nftables.org/wiki-nftables/index.php/Matching_packet_metainformation
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type Meta struct {
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Key MetaKey
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Register uint32
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}
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func (e *Meta) marshal() ([]byte, error) {
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exprData, err := netlink.MarshalAttributes(
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[]netlink.Attribute{
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{Type: unix.NFTA_META_KEY, Data: binaryutil.BigEndian.PutUint32(uint32(e.Key))},
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{Type: unix.NFTA_META_DREG, Data: binaryutil.BigEndian.PutUint32(e.Register)},
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},
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)
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if err != nil {
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return nil, err
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}
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return netlink.MarshalAttributes([]netlink.Attribute{
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{Type: unix.NFTA_EXPR_NAME, Data: []byte("meta\x00")},
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{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: exprData},
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})
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}
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func (e *Meta) unmarshal(data []byte) error {
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ad, err := netlink.NewAttributeDecoder(data)
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if err != nil {
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return err
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}
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ad.ByteOrder = binary.BigEndian
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for ad.Next() {
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switch ad.Type() {
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case unix.NFTA_META_DREG:
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e.Register = ad.Uint32()
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case unix.NFTA_META_KEY:
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e.Key = MetaKey(ad.Uint32())
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}
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}
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return ad.Err()
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}
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// Masq (Masquerade) is a special case of SNAT, where the source address is
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// automagically set to the address of the output interface. See also
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// https://wiki.nftables.org/wiki-nftables/index.php/Performing_Network_Address_Translation_(NAT)#Masquerading
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type Masq struct{}
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func (e *Masq) marshal() ([]byte, error) {
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return netlink.MarshalAttributes([]netlink.Attribute{
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{Type: unix.NFTA_EXPR_NAME, Data: []byte("masq\x00")},
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{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: nil},
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})
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}
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func (e *Masq) unmarshal(data []byte) error {
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return fmt.Errorf("not yet implemented")
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}
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// CmpOp specifies which type of comparison should be performed.
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type CmpOp uint32
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// Possible CmpOp values.
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const (
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CmpOpEq CmpOp = unix.NFT_CMP_EQ
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CmpOpNeq CmpOp = unix.NFT_CMP_NEQ
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CmpOpLt CmpOp = unix.NFT_CMP_LT
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CmpOpLte CmpOp = unix.NFT_CMP_LTE
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CmpOpGt CmpOp = unix.NFT_CMP_GT
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CmpOpGte CmpOp = unix.NFT_CMP_GTE
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)
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// Cmp compares a register with the specified data.
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type Cmp struct {
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Op CmpOp
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Register uint32
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Data []byte
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}
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func (e *Cmp) marshal() ([]byte, error) {
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cmpData, err := netlink.MarshalAttributes([]netlink.Attribute{
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{Type: unix.NFTA_DATA_VALUE, Data: e.Data},
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})
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if err != nil {
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return nil, err
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}
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exprData, err := netlink.MarshalAttributes([]netlink.Attribute{
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{Type: unix.NFTA_CMP_SREG, Data: binaryutil.BigEndian.PutUint32(e.Register)},
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{Type: unix.NFTA_CMP_OP, Data: binaryutil.BigEndian.PutUint32(uint32(e.Op))},
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{Type: unix.NLA_F_NESTED | unix.NFTA_CMP_DATA, Data: cmpData},
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})
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if err != nil {
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return nil, err
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}
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return netlink.MarshalAttributes([]netlink.Attribute{
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{Type: unix.NFTA_EXPR_NAME, Data: []byte("cmp\x00")},
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{Type: unix.NLA_F_NESTED | unix.NFTA_EXPR_DATA, Data: exprData},
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})
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}
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func (e *Cmp) unmarshal(data []byte) error {
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ad, err := netlink.NewAttributeDecoder(data)
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if err != nil {
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return err
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}
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ad.ByteOrder = binary.BigEndian
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for ad.Next() {
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switch ad.Type() {
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case unix.NFTA_CMP_SREG:
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e.Register = ad.Uint32()
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case unix.NFTA_CMP_OP:
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e.Op = CmpOp(ad.Uint32())
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case unix.NFTA_CMP_DATA:
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ad.Do(func(b []byte) error {
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ad, err := netlink.NewAttributeDecoder(b)
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if err != nil {
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return err
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}
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ad.ByteOrder = binary.BigEndian
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if ad.Next() && ad.Type() == unix.NFTA_DATA_VALUE {
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ad.Do(func(b []byte) error {
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e.Data = b
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return nil
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})
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}
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return ad.Err()
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})
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}
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}
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return ad.Err()
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}
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