268 lines
7.6 KiB
Go
268 lines
7.6 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/google/nftables/internal/parseexprfunc"
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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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type ruleOperation uint32
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// Possible PayloadOperationType values.
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const (
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operationAdd ruleOperation = iota
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operationInsert
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operationReplace
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)
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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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Position uint64
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Handle uint64
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// The list of possible flags are specified by nftnl_rule_attr, see
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// https://git.netfilter.org/libnftnl/tree/include/libnftnl/rule.h#n21
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// Current nftables go implementation supports only
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// NFTNL_RULE_POSITION flag for setting rule at position 0
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Flags uint32
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Exprs []expr.Any
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UserData []byte
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}
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// GetRule returns the rules in the specified table and chain.
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//
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// Deprecated: use GetRules instead.
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func (cc *Conn) GetRule(t *Table, c *Chain) ([]*Rule, error) {
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return cc.GetRules(t, c)
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}
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// GetRules returns the rules in the specified table and chain.
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func (cc *Conn) GetRules(t *Table, c *Chain) ([]*Rule, error) {
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conn, closer, err := cc.netlinkConn()
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if err != nil {
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return nil, err
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}
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defer func() { _ = closer() }()
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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 := receiveAckAware(conn, message.Header.Flags)
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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(t.Family, 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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// AddRule adds the specified Rule
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func (cc *Conn) newRule(r *Rule, op ruleOperation) *Rule {
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cc.mu.Lock()
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defer cc.mu.Unlock()
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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(byte(r.Table.Family), 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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})
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if r.Handle != 0 {
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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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}
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data = append(data, cc.marshalAttr([]netlink.Attribute{
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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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if compatPolicy, err := getCompatPolicy(r.Exprs); err != nil {
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cc.setErr(err)
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} else if compatPolicy != nil {
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data = append(data, cc.marshalAttr([]netlink.Attribute{
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{Type: unix.NLA_F_NESTED | unix.NFTA_RULE_COMPAT, Data: cc.marshalAttr([]netlink.Attribute{
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{Type: unix.NFTA_RULE_COMPAT_PROTO, Data: binaryutil.BigEndian.PutUint32(compatPolicy.Proto)},
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{Type: unix.NFTA_RULE_COMPAT_FLAGS, Data: binaryutil.BigEndian.PutUint32(compatPolicy.Flag & nft_RULE_COMPAT_F_MASK)},
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})},
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})...)
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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.UserData != nil {
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msgData = append(msgData, cc.marshalAttr([]netlink.Attribute{
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{Type: unix.NFTA_RULE_USERDATA, Data: r.UserData},
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})...)
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}
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switch op {
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case operationAdd:
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flags = netlink.Request | netlink.Acknowledge | netlink.Create | unix.NLM_F_ECHO | unix.NLM_F_APPEND
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case operationInsert:
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flags = netlink.Request | netlink.Acknowledge | netlink.Create | unix.NLM_F_ECHO
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case operationReplace:
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flags = netlink.Request | netlink.Acknowledge | netlink.Replace | unix.NLM_F_ECHO | unix.NLM_F_REPLACE
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}
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if r.Position != 0 || (r.Flags&(1<<unix.NFTA_RULE_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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}
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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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func (cc *Conn) ReplaceRule(r *Rule) *Rule {
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return cc.newRule(r, operationReplace)
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}
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func (cc *Conn) AddRule(r *Rule) *Rule {
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if r.Handle != 0 {
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return cc.newRule(r, operationReplace)
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}
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return cc.newRule(r, operationAdd)
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}
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func (cc *Conn) InsertRule(r *Rule) *Rule {
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if r.Handle != 0 {
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return cc.newRule(r, operationReplace)
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}
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return cc.newRule(r, operationInsert)
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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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cc.mu.Lock()
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defer cc.mu.Unlock()
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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 ruleFromMsg(fam TableFamily, 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{
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Name: ad.String(),
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Family: fam,
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}
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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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exprs, err := parseexprfunc.ParseExprMsgFunc(byte(fam), b)
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if err != nil {
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return err
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}
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r.Exprs = make([]expr.Any, len(exprs))
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for i := range exprs {
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r.Exprs[i] = exprs[i].(expr.Any)
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}
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return nil
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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.UserData = ad.Bytes()
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}
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}
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return &r, ad.Err()
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}
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