294 lines
8.4 KiB
Go
294 lines
8.4 KiB
Go
// 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 nftables
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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/google/nftables/expr"
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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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var ruleHeaderType = netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_NEWRULE)
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// A Rule does something with a packet. See also
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// https://wiki.nftables.org/wiki-nftables/index.php/Simple_rule_management
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type Rule struct {
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Table *Table
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Chain *Chain
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RuleID uint32
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Position uint64
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Handle uint64
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Exprs []expr.Any
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}
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// GetRule returns the rules in the specified table and chain.
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func (cc *Conn) GetRule(t *Table, c *Chain) ([]*Rule, error) {
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conn, err := cc.dialNetlink()
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if err != nil {
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return nil, err
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}
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defer conn.Close()
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data, err := netlink.MarshalAttributes([]netlink.Attribute{
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{Type: unix.NFTA_RULE_TABLE, Data: []byte(t.Name + "\x00")},
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{Type: unix.NFTA_RULE_CHAIN, Data: []byte(c.Name + "\x00")},
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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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message := netlink.Message{
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Header: netlink.Header{
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Type: netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_GETRULE),
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Flags: netlink.Request | netlink.Acknowledge | netlink.Dump | unix.NLM_F_ECHO,
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},
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Data: append(extraHeader(uint8(t.Family), 0), data...),
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}
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if _, err := conn.SendMessages([]netlink.Message{message}); err != nil {
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return nil, fmt.Errorf("SendMessages: %v", err)
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}
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reply, err := conn.Receive()
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if err != nil {
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return nil, fmt.Errorf("Receive: %v", err)
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}
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var rules []*Rule
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for _, msg := range reply {
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r, err := ruleFromMsg(msg)
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if err != nil {
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return nil, err
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}
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rules = append(rules, r)
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}
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return rules, nil
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}
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// GetRuleHandle returns a specific rule's handle. Rule is identified by Table, Chain and RuleID.
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func (cc *Conn) GetRuleHandle(t *Table, c *Chain, ruleID uint32) (uint64, error) {
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conn, err := cc.dialNetlink()
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if err != nil {
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return 0, err
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}
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defer conn.Close()
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if ruleID == 0 {
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return 0, fmt.Errorf("rule's id cannot be 0")
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}
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data, err := netlink.MarshalAttributes([]netlink.Attribute{
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{Type: unix.NFTA_RULE_TABLE, Data: []byte(t.Name + "\x00")},
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{Type: unix.NFTA_RULE_CHAIN, Data: []byte(c.Name + "\x00")},
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{Type: unix.NFTA_RULE_USERDATA, Data: binaryutil.BigEndian.PutUint32(ruleID)},
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})
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if err != nil {
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return 0, err
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}
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message := netlink.Message{
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Header: netlink.Header{
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Type: netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_GETRULE),
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Flags: netlink.Request | netlink.Acknowledge | netlink.Dump | unix.NLM_F_ECHO,
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},
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Data: append(extraHeader(uint8(t.Family), 0), data...),
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}
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if _, err := conn.SendMessages([]netlink.Message{message}); err != nil {
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return 0, fmt.Errorf("SendMessages: %v", err)
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}
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reply, err := conn.Receive()
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if err != nil {
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return 0, fmt.Errorf("Receive: %v", err)
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}
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for _, msg := range reply {
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rr, err := ruleFromMsg(msg)
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if err != nil {
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return 0, err
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}
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if rr.RuleID == ruleID {
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return rr.Handle, nil
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}
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}
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return 0, fmt.Errorf("rule with id %d is not found", ruleID)
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}
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// AddRule adds the specified Rule
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func (cc *Conn) AddRule(r *Rule) *Rule {
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exprAttrs := make([]netlink.Attribute, len(r.Exprs))
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for idx, expr := range r.Exprs {
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exprAttrs[idx] = netlink.Attribute{
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Type: unix.NLA_F_NESTED | unix.NFTA_LIST_ELEM,
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Data: cc.marshalExpr(expr),
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}
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}
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data := cc.marshalAttr([]netlink.Attribute{
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{Type: unix.NFTA_RULE_TABLE, Data: []byte(r.Table.Name + "\x00")},
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{Type: unix.NFTA_RULE_CHAIN, Data: []byte(r.Chain.Name + "\x00")},
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{Type: unix.NLA_F_NESTED | unix.NFTA_RULE_EXPRESSIONS, Data: cc.marshalAttr(exprAttrs)},
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})
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msgData := []byte{}
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msgData = append(msgData, data...)
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var flags netlink.HeaderFlags
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if r.RuleID != 0 {
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msgData = append(msgData, cc.marshalAttr([]netlink.Attribute{
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{Type: unix.NFTA_RULE_USERDATA, Data: binaryutil.BigEndian.PutUint32(r.RuleID)},
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})...)
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}
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if r.Position != 0 {
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msgData = append(msgData, cc.marshalAttr([]netlink.Attribute{
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{Type: unix.NFTA_RULE_POSITION, Data: binaryutil.BigEndian.PutUint64(r.Position)},
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})...)
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// when a rule's position is specified, it becomes nft insert rule operation
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flags = netlink.Request | netlink.Acknowledge | netlink.Create | unix.NLM_F_ECHO
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} else {
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// unix.NLM_F_APPEND is added when nft add rule operation is executed.
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flags = netlink.Request | netlink.Acknowledge | netlink.Create | unix.NLM_F_ECHO | unix.NLM_F_APPEND
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}
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cc.messages = append(cc.messages, netlink.Message{
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Header: netlink.Header{
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Type: ruleHeaderType,
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Flags: flags,
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},
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Data: append(extraHeader(uint8(r.Table.Family), 0), msgData...),
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})
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return r
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}
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// DelRule deletes the specified Rule, rule's handle cannot be 0
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func (cc *Conn) DelRule(r *Rule) error {
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data := cc.marshalAttr([]netlink.Attribute{
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{Type: unix.NFTA_RULE_TABLE, Data: []byte(r.Table.Name + "\x00")},
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{Type: unix.NFTA_RULE_CHAIN, Data: []byte(r.Chain.Name + "\x00")},
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})
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if r.Handle == 0 {
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return fmt.Errorf("rule's handle cannot be 0")
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}
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data = append(data, cc.marshalAttr([]netlink.Attribute{
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{Type: unix.NFTA_RULE_HANDLE, Data: binaryutil.BigEndian.PutUint64(r.Handle)},
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})...)
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flags := netlink.Request | netlink.Acknowledge
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cc.messages = append(cc.messages, netlink.Message{
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Header: netlink.Header{
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Type: netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_DELRULE),
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Flags: flags,
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},
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Data: append(extraHeader(uint8(r.Table.Family), 0), data...),
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})
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return nil
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}
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func exprsFromMsg(b []byte) ([]expr.Any, error) {
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ad, err := netlink.NewAttributeDecoder(b)
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if err != nil {
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return nil, err
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}
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ad.ByteOrder = binary.BigEndian
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var exprs []expr.Any
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for ad.Next() {
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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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var name string
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for ad.Next() {
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switch ad.Type() {
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case unix.NFTA_EXPR_NAME:
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name = ad.String()
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case unix.NFTA_EXPR_DATA:
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var e expr.Any
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switch name {
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case "meta":
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e = &expr.Meta{}
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case "cmp":
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e = &expr.Cmp{}
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case "counter":
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e = &expr.Counter{}
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case "payload":
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e = &expr.Payload{}
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case "lookup":
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e = &expr.Lookup{}
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case "immediate":
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e = &expr.Immediate{}
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}
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if e == nil {
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// TODO: introduce an opaque expression type so that users know
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// something is here.
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continue // unsupported expression type
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}
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ad.Do(func(b []byte) error {
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if err := expr.Unmarshal(b, e); err != nil {
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return err
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}
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// Verdict expressions are a special-case of immediate expressions, so
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// if the expression is an immediate writing nothing into the verdict
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// register (invalid), re-parse it as a verdict expression.
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if imm, isImmediate := e.(*expr.Immediate); isImmediate && imm.Register == unix.NFT_REG_VERDICT && len(imm.Data) == 0 {
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e = &expr.Verdict{}
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if err := expr.Unmarshal(b, e); err != nil {
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return err
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}
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}
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exprs = append(exprs, e)
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return nil
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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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}
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return exprs, ad.Err()
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}
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func ruleFromMsg(msg netlink.Message) (*Rule, error) {
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if got, want := msg.Header.Type, ruleHeaderType; got != want {
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return nil, fmt.Errorf("unexpected header type: got %v, want %v", got, want)
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}
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ad, err := netlink.NewAttributeDecoder(msg.Data[4:])
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if err != nil {
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return nil, err
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}
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ad.ByteOrder = binary.BigEndian
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var r Rule
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for ad.Next() {
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switch ad.Type() {
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case unix.NFTA_RULE_TABLE:
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r.Table = &Table{Name: ad.String()}
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case unix.NFTA_RULE_CHAIN:
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r.Chain = &Chain{Name: ad.String()}
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case unix.NFTA_RULE_EXPRESSIONS:
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ad.Do(func(b []byte) error {
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r.Exprs, err = exprsFromMsg(b)
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return err
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})
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case unix.NFTA_RULE_POSITION:
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r.Position = ad.Uint64()
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case unix.NFTA_RULE_HANDLE:
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r.Handle = ad.Uint64()
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case unix.NFTA_RULE_USERDATA:
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r.RuleID = ad.Uint32()
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}
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}
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return &r, ad.Err()
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}
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