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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 nftables
import (
"fmt"
"github.com/mdlayher/netlink"
"golang.org/x/sys/unix"
)
var tableHeaderType = netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_NEWTABLE)
// TableFamily specifies the address family for this table.
type TableFamily byte
// Possible TableFamily values.
const (
TableFamilyUnspecified TableFamily = unix.NFPROTO_UNSPEC
TableFamilyINet TableFamily = unix.NFPROTO_INET
TableFamilyIPv4 TableFamily = unix.NFPROTO_IPV4
TableFamilyIPv6 TableFamily = unix.NFPROTO_IPV6
TableFamilyARP TableFamily = unix.NFPROTO_ARP
TableFamilyNetdev TableFamily = unix.NFPROTO_NETDEV
TableFamilyBridge TableFamily = unix.NFPROTO_BRIDGE
)
// A Table contains Chains. See also
// https://wiki.nftables.org/wiki-nftables/index.php/Configuring_tables
type Table struct {
Name string // NFTA_TABLE_NAME
Use uint32 // NFTA_TABLE_USE (Number of chains in table)
Flags uint32 // NFTA_TABLE_FLAGS
Family TableFamily
}
// DelTable deletes a specific table, along with all chains/rules it contains.
func (cc *Conn) DelTable(t *Table) {
cc.mu.Lock()
defer cc.mu.Unlock()
data := cc.marshalAttr([]netlink.Attribute{
{Type: unix.NFTA_TABLE_NAME, Data: []byte(t.Name + "\x00")},
{Type: unix.NFTA_TABLE_FLAGS, Data: []byte{0, 0, 0, 0}},
})
cc.messages = append(cc.messages, netlink.Message{
Header: netlink.Header{
Type: netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_DELTABLE),
Flags: netlink.Request | netlink.Acknowledge,
},
Data: append(extraHeader(uint8(t.Family), 0), data...),
})
}
// AddTable adds the specified Table. See also
// https://wiki.nftables.org/wiki-nftables/index.php/Configuring_tables
func (cc *Conn) AddTable(t *Table) *Table {
cc.mu.Lock()
defer cc.mu.Unlock()
data := cc.marshalAttr([]netlink.Attribute{
{Type: unix.NFTA_TABLE_NAME, Data: []byte(t.Name + "\x00")},
{Type: unix.NFTA_TABLE_FLAGS, Data: []byte{0, 0, 0, 0}},
})
cc.messages = append(cc.messages, netlink.Message{
Header: netlink.Header{
Type: netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_NEWTABLE),
Flags: netlink.Request | netlink.Acknowledge | netlink.Create,
},
Data: append(extraHeader(uint8(t.Family), 0), data...),
})
return t
}
// FlushTable removes all rules in all chains within the specified Table. See also
// https://wiki.nftables.org/wiki-nftables/index.php/Configuring_tables#Flushing_tables
func (cc *Conn) FlushTable(t *Table) {
cc.mu.Lock()
defer cc.mu.Unlock()
data := cc.marshalAttr([]netlink.Attribute{
{Type: unix.NFTA_RULE_TABLE, Data: []byte(t.Name + "\x00")},
})
cc.messages = append(cc.messages, netlink.Message{
Header: netlink.Header{
Type: netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_DELRULE),
Flags: netlink.Request | netlink.Acknowledge,
},
Data: append(extraHeader(uint8(t.Family), 0), data...),
})
}
// ListTables returns currently configured tables in the kernel
func (cc *Conn) ListTables() ([]*Table, error) {
return cc.ListTablesOfFamily(TableFamilyUnspecified)
}
// ListTablesOfFamily returns currently configured tables for the specified table family
// in the kernel. It lists all tables if family is TableFamilyUnspecified.
func (cc *Conn) ListTablesOfFamily(family TableFamily) ([]*Table, error) {
conn, closer, err := cc.netlinkConn()
if err != nil {
return nil, err
}
defer func() { _ = closer() }()
msg := netlink.Message{
Header: netlink.Header{
Type: netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_GETTABLE),
Flags: netlink.Request | netlink.Dump,
},
Data: extraHeader(uint8(family), 0),
}
response, err := conn.Execute(msg)
if err != nil {
return nil, err
}
var tables []*Table
for _, m := range response {
t, err := tableFromMsg(m)
if err != nil {
return nil, err
}
tables = append(tables, t)
}
return tables, nil
}
func tableFromMsg(msg netlink.Message) (*Table, error) {
if got, want := msg.Header.Type, tableHeaderType; got != want {
return nil, fmt.Errorf("unexpected header type: got %v, want %v", got, want)
}
var t Table
t.Family = TableFamily(msg.Data[0])
ad, err := netlink.NewAttributeDecoder(msg.Data[4:])
if err != nil {
return nil, err
}
for ad.Next() {
switch ad.Type() {
case unix.NFTA_TABLE_NAME:
t.Name = ad.String()
case unix.NFTA_TABLE_USE:
t.Use = ad.Uint32()
case unix.NFTA_TABLE_FLAGS:
t.Flags = ad.Uint32()
}
}
return &t, nil
}
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