nftables/monitor.go

320 lines
9.0 KiB
Go

// 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 (
"math"
"strings"
"sync"
"github.com/mdlayher/netlink"
"golang.org/x/sys/unix"
)
type MonitorAction uint8
// Possible MonitorAction values.
const (
MonitorActionNew MonitorAction = 1 << iota
MonitorActionDel
MonitorActionMask MonitorAction = (1 << iota) - 1
MonitorActionAny MonitorAction = MonitorActionMask
)
type MonitorObject uint32
// Possible MonitorObject values.
const (
MonitorObjectTables MonitorObject = 1 << iota
MonitorObjectChains
MonitorObjectSets
MonitorObjectRules
MonitorObjectElements
MonitorObjectRuleset
MonitorObjectMask MonitorObject = (1 << iota) - 1
MonitorObjectAny MonitorObject = MonitorObjectMask
)
var (
monitorFlags = map[MonitorAction]map[MonitorObject]uint32{
MonitorActionAny: {
MonitorObjectAny: 0xffffffff,
MonitorObjectTables: 1<<unix.NFT_MSG_NEWTABLE | 1<<unix.NFT_MSG_DELTABLE,
MonitorObjectChains: 1<<unix.NFT_MSG_NEWCHAIN | 1<<unix.NFT_MSG_DELCHAIN,
MonitorObjectRules: 1<<unix.NFT_MSG_NEWRULE | 1<<unix.NFT_MSG_DELRULE,
MonitorObjectSets: 1<<unix.NFT_MSG_NEWSET | 1<<unix.NFT_MSG_DELSET,
MonitorObjectElements: 1<<unix.NFT_MSG_NEWSETELEM | 1<<unix.NFT_MSG_DELSETELEM,
MonitorObjectRuleset: 1<<unix.NFT_MSG_NEWTABLE | 1<<unix.NFT_MSG_DELTABLE |
1<<unix.NFT_MSG_NEWCHAIN | 1<<unix.NFT_MSG_DELCHAIN |
1<<unix.NFT_MSG_NEWRULE | 1<<unix.NFT_MSG_DELRULE |
1<<unix.NFT_MSG_NEWSET | 1<<unix.NFT_MSG_DELSET |
1<<unix.NFT_MSG_NEWSETELEM | 1<<unix.NFT_MSG_DELSETELEM |
1<<unix.NFT_MSG_NEWOBJ | 1<<unix.NFT_MSG_DELOBJ,
},
MonitorActionNew: {
MonitorObjectAny: 1<<unix.NFT_MSG_NEWTABLE |
1<<unix.NFT_MSG_NEWCHAIN |
1<<unix.NFT_MSG_NEWRULE |
1<<unix.NFT_MSG_NEWSET |
1<<unix.NFT_MSG_NEWSETELEM,
MonitorObjectTables: 1 << unix.NFT_MSG_NEWTABLE,
MonitorObjectChains: 1 << unix.NFT_MSG_NEWCHAIN,
MonitorObjectRules: 1 << unix.NFT_MSG_NEWRULE,
MonitorObjectSets: 1 << unix.NFT_MSG_NEWSET,
MonitorObjectRuleset: 1<<unix.NFT_MSG_NEWTABLE |
1<<unix.NFT_MSG_NEWCHAIN |
1<<unix.NFT_MSG_NEWRULE |
1<<unix.NFT_MSG_NEWSET |
1<<unix.NFT_MSG_NEWSETELEM |
1<<unix.NFT_MSG_NEWOBJ,
},
MonitorActionDel: {
MonitorObjectAny: 1<<unix.NFT_MSG_DELTABLE |
1<<unix.NFT_MSG_DELCHAIN |
1<<unix.NFT_MSG_DELRULE |
1<<unix.NFT_MSG_DELSET |
1<<unix.NFT_MSG_DELSETELEM |
1<<unix.NFT_MSG_DELOBJ,
},
}
)
type MonitorEventType int
const (
MonitorEventTypeNewTable MonitorEventType = unix.NFT_MSG_NEWTABLE
MonitorEventTypeDelTable MonitorEventType = unix.NFT_MSG_DELTABLE
MonitorEventTypeNewChain MonitorEventType = unix.NFT_MSG_NEWCHAIN
MonitorEventTypeDelChain MonitorEventType = unix.NFT_MSG_DELCHAIN
MonitorEventTypeNewRule MonitorEventType = unix.NFT_MSG_NEWRULE
MonitorEventTypeDelRule MonitorEventType = unix.NFT_MSG_DELRULE
MonitorEventTypeNewSet MonitorEventType = unix.NFT_MSG_NEWSET
MonitorEventTypeDelSet MonitorEventType = unix.NFT_MSG_DELSET
MonitorEventTypeNewSetElem MonitorEventType = unix.NFT_MSG_NEWSETELEM
MonitorEventTypeDelSetElem MonitorEventType = unix.NFT_MSG_DELSETELEM
MonitorEventTypeNewObj MonitorEventType = unix.NFT_MSG_NEWOBJ
MonitorEventTypeDelObj MonitorEventType = unix.NFT_MSG_DELOBJ
MonitorEventTypeOOB MonitorEventType = math.MaxInt // out of band event
)
// A MonitorEvent represents a single change received via a [Monitor].
//
// Depending on the Type, the Data field can be type-asserted to the specific
// data type for this event, e.g. when Type is
// nftables.MonitorEventTypeNewTable, you can access the corresponding table
// details via Data.(*nftables.Table).
type MonitorEvent struct {
Type MonitorEventType
Data any
Error error
}
const (
monitorOK = iota
monitorClosed
)
// A Monitor is an event-based nftables monitor that will receive one event per
// new (or deleted) table, chain, rule, set, etc., depending on the monitor
// configuration.
type Monitor struct {
action MonitorAction
object MonitorObject
monitorFlags uint32
conn *netlink.Conn
closer netlinkCloser
// mu covers eventCh and status
mu sync.Mutex
eventCh chan *MonitorEvent
status int
}
type MonitorOption func(*Monitor)
func WithMonitorEventBuffer(size int) MonitorOption {
return func(monitor *Monitor) {
monitor.eventCh = make(chan *MonitorEvent, size)
}
}
// WithMonitorAction to set monitor actions like new, del or any.
func WithMonitorAction(action MonitorAction) MonitorOption {
return func(monitor *Monitor) {
monitor.action = action
}
}
// WithMonitorObject to set monitor objects.
func WithMonitorObject(object MonitorObject) MonitorOption {
return func(monitor *Monitor) {
monitor.object = object
}
}
// NewMonitor returns a Monitor with options to be started.
//
// Note that NewMonitor only prepares a Monitor. To install the monitor, call
// [Conn.AddMonitor].
func NewMonitor(opts ...MonitorOption) *Monitor {
monitor := &Monitor{
status: monitorOK,
}
for _, opt := range opts {
opt(monitor)
}
if monitor.eventCh == nil {
monitor.eventCh = make(chan *MonitorEvent)
}
objects, ok := monitorFlags[monitor.action]
if !ok {
objects = monitorFlags[MonitorActionAny]
}
flags, ok := objects[monitor.object]
if !ok {
flags = objects[MonitorObjectAny]
}
monitor.monitorFlags = flags
return monitor
}
func (monitor *Monitor) monitor() {
for {
msgs, err := monitor.conn.Receive()
if err != nil {
if strings.Contains(err.Error(), "use of closed file") {
// ignore the error that be closed
break
} else {
// any other errors will be send to user, and then to close eventCh
event := &MonitorEvent{
Type: MonitorEventTypeOOB,
Data: nil,
Error: err,
}
monitor.eventCh <- event
break
}
}
for _, msg := range msgs {
if msg.Header.Type&0xff00>>8 != netlink.HeaderType(unix.NFNL_SUBSYS_NFTABLES) {
continue
}
msgType := msg.Header.Type & 0x00ff
if monitor.monitorFlags&1<<msgType == 0 {
continue
}
switch msgType {
case unix.NFT_MSG_NEWTABLE, unix.NFT_MSG_DELTABLE:
table, err := tableFromMsg(msg)
event := &MonitorEvent{
Type: MonitorEventType(msgType),
Data: table,
Error: err,
}
monitor.eventCh <- event
case unix.NFT_MSG_NEWCHAIN, unix.NFT_MSG_DELCHAIN:
chain, err := chainFromMsg(msg)
event := &MonitorEvent{
Type: MonitorEventType(msgType),
Data: chain,
Error: err,
}
monitor.eventCh <- event
case unix.NFT_MSG_NEWRULE, unix.NFT_MSG_DELRULE:
rule, err := parseRuleFromMsg(msg)
event := &MonitorEvent{
Type: MonitorEventType(msgType),
Data: rule,
Error: err,
}
monitor.eventCh <- event
case unix.NFT_MSG_NEWSET, unix.NFT_MSG_DELSET:
set, err := setsFromMsg(msg)
event := &MonitorEvent{
Type: MonitorEventType(msgType),
Data: set,
Error: err,
}
monitor.eventCh <- event
case unix.NFT_MSG_NEWSETELEM, unix.NFT_MSG_DELSETELEM:
elems, err := elementsFromMsg(uint8(TableFamilyUnspecified), msg)
event := &MonitorEvent{
Type: MonitorEventType(msgType),
Data: elems,
Error: err,
}
monitor.eventCh <- event
case unix.NFT_MSG_NEWOBJ, unix.NFT_MSG_DELOBJ:
obj, err := objFromMsg(msg, true)
event := &MonitorEvent{
Type: MonitorEventType(msgType),
Data: obj,
Error: err,
}
monitor.eventCh <- event
}
}
}
monitor.mu.Lock()
defer monitor.mu.Unlock()
if monitor.status != monitorClosed {
monitor.status = monitorClosed
}
close(monitor.eventCh)
}
func (monitor *Monitor) Close() error {
monitor.mu.Lock()
defer monitor.mu.Unlock()
if monitor.status != monitorClosed {
monitor.status = monitorClosed
return monitor.closer()
}
return nil
}
// AddMonitor to perform the monitor immediately. The channel will be closed after
// calling Close on Monitor or encountering a netlink conn error while Receive.
// Caller may receive a MonitorEventTypeOOB event which contains an error we didn't
// handle, for now.
func (cc *Conn) AddMonitor(monitor *Monitor) (chan *MonitorEvent, error) {
conn, closer, err := cc.netlinkConn()
if err != nil {
return nil, err
}
monitor.conn = conn
monitor.closer = closer
if monitor.monitorFlags != 0 {
if err = conn.JoinGroup(uint32(unix.NFNLGRP_NFTABLES)); err != nil {
monitor.closer()
return nil, err
}
}
go monitor.monitor()
return monitor.eventCh, nil
}
func parseRuleFromMsg(msg netlink.Message) (*Rule, error) {
genmsg := &NFGenMsg{}
genmsg.Decode(msg.Data[:4])
return ruleFromMsg(TableFamily(genmsg.NFGenFamily), msg)
}