279 lines
8.3 KiB
Go
279 lines
8.3 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 manipulates Linux nftables (the iptables successor).
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package nftables
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import (
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"fmt"
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"math"
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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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"github.com/mdlayher/netlink/nltest"
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"golang.org/x/sys/unix"
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)
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func extraHeader(family uint8, resID uint16) []byte {
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return append([]byte{
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family,
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unix.NFNETLINK_V0,
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}, binaryutil.NativeEndian.PutUint16(resID)...)
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}
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func batch(messages []netlink.Message) []netlink.Message {
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batch := []netlink.Message{
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{
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Header: netlink.Header{
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Type: netlink.HeaderType(unix.NFNL_MSG_BATCH_BEGIN),
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Flags: netlink.HeaderFlagsRequest,
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},
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Data: extraHeader(0, unix.NFNL_SUBSYS_NFTABLES),
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},
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}
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batch = append(batch, messages...)
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batch = append(batch, netlink.Message{
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Header: netlink.Header{
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Type: netlink.HeaderType(unix.NFNL_MSG_BATCH_END),
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Flags: netlink.HeaderFlagsRequest,
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},
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Data: extraHeader(0, unix.NFNL_SUBSYS_NFTABLES),
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})
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return batch
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}
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// ChainHook specifies at which step in packet processing the Chain should be
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// executed. See also
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// https://wiki.nftables.org/wiki-nftables/index.php/Configuring_chains#Base_chain_hooks
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type ChainHook uint32
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// Possible ChainHook values.
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const (
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ChainHookPrerouting ChainHook = unix.NF_INET_PRE_ROUTING
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ChainHookInput ChainHook = unix.NF_INET_LOCAL_IN
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ChainHookForward ChainHook = unix.NF_INET_FORWARD
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ChainHookOutput ChainHook = unix.NF_INET_LOCAL_OUT
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ChainHookPostrouting ChainHook = unix.NF_INET_POST_ROUTING
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ChainHookIngress ChainHook = unix.NF_NETDEV_INGRESS
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)
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// ChainPriority orders the chain relative to Netfilter internal operations. See
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// also
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// https://wiki.nftables.org/wiki-nftables/index.php/Configuring_chains#Base_chain_priority
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type ChainPriority int32
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// Possible ChainPriority values.
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const ( // from /usr/include/linux/netfilter_ipv4.h
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ChainPriorityFirst ChainPriority = math.MinInt32
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ChainPriorityConntrackDefrag ChainPriority = -400
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ChainPriorityRaw ChainPriority = -300
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ChainPrioritySELinuxFirst ChainPriority = -225
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ChainPriorityConntrack ChainPriority = -200
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ChainPriorityMangle ChainPriority = -150
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ChainPriorityNATDest ChainPriority = -100
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ChainPriorityFilter ChainPriority = 0
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ChainPrioritySecurity ChainPriority = 50
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ChainPriorityNATSource ChainPriority = 100
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ChainPrioritySELinuxLast ChainPriority = 225
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ChainPriorityConntrackHelper ChainPriority = 300
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ChainPriorityConntrackConfirm ChainPriority = math.MaxInt32
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ChainPriorityLast ChainPriority = math.MaxInt32
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)
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// ChainType defines what this chain will be used for. See also
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// https://wiki.nftables.org/wiki-nftables/index.php/Configuring_chains#Base_chain_types
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type ChainType string
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// Possible ChainType values.
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const (
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ChainTypeFilter ChainType = "filter"
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ChainTypeRoute ChainType = "route"
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ChainTypeNAT ChainType = "nat"
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)
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// A Chain contains Rules. See also
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// https://wiki.nftables.org/wiki-nftables/index.php/Configuring_chains
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type Chain struct {
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Name string
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Table *Table
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Hooknum ChainHook
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Priority ChainPriority
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Type ChainType
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}
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// AddChain adds the specified Chain. See also
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// https://wiki.nftables.org/wiki-nftables/index.php/Configuring_chains#Adding_base_chains
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func (cc *Conn) AddChain(c *Chain) *Chain {
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chainHook := cc.marshalAttr([]netlink.Attribute{
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{Type: unix.NFTA_HOOK_HOOKNUM, Data: binaryutil.BigEndian.PutUint32(uint32(c.Hooknum))},
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{Type: unix.NFTA_HOOK_PRIORITY, Data: binaryutil.BigEndian.PutUint32(uint32(c.Priority))},
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})
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data := cc.marshalAttr([]netlink.Attribute{
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{Type: unix.NFTA_CHAIN_TABLE, Data: []byte(c.Table.Name + "\x00")},
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{Type: unix.NFTA_CHAIN_NAME, Data: []byte(c.Name + "\x00")},
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{Type: unix.NLA_F_NESTED | unix.NFTA_CHAIN_HOOK, Data: chainHook},
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{Type: unix.NFTA_CHAIN_TYPE, Data: []byte(c.Type + "\x00")},
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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: netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_NEWCHAIN),
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Flags: netlink.HeaderFlagsRequest | netlink.HeaderFlagsAcknowledge | netlink.HeaderFlagsCreate,
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},
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Data: append(extraHeader(unix.AF_INET, 0), data...),
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})
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return c
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}
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func (cc *Conn) setErr(err error) {
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if cc.err != nil {
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return
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}
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cc.err = err
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}
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func (cc *Conn) marshalAttr(attrs []netlink.Attribute) []byte {
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b, err := netlink.MarshalAttributes(attrs)
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if err != nil {
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cc.setErr(err)
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return nil
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}
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return b
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}
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func (cc *Conn) marshalExpr(e expr.Any) []byte {
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b, err := expr.Marshal(e)
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if err != nil {
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cc.setErr(err)
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return nil
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}
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return b
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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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Exprs []expr.Any
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}
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// AddRule adds the specified Rule. See also
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// https://wiki.nftables.org/wiki-nftables/index.php/Simple_rule_management
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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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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_NEWRULE),
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Flags: netlink.HeaderFlagsRequest | netlink.HeaderFlagsAcknowledge | netlink.HeaderFlagsCreate,
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},
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Data: append(extraHeader(unix.AF_INET, 0), data...),
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})
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return r
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}
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// TableFamily specifies the address family for this table.
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type TableFamily byte
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// Possible TableFamily values.
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const (
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TableFamilyIPv4 TableFamily = unix.AF_INET
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TableFamilyIPv6 TableFamily = unix.AF_INET6
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)
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// A Table contains Chains. See also
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// https://wiki.nftables.org/wiki-nftables/index.php/Configuring_tables
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type Table struct {
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Name string
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Family TableFamily
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}
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// A Conn represents a netlink connection of the nftables family.
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//
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// All methods return their input, so that variables can be defined from string
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// literals when desired.
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//
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// Commands are buffered. Flush sends all buffered commands in a single batch.
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type Conn struct {
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TestDial nltest.Func // for testing only; passed to nltest.Dial
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messages []netlink.Message
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err error
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}
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// AddTable adds the specified Table. See also
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// https://wiki.nftables.org/wiki-nftables/index.php/Configuring_tables
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func (cc *Conn) AddTable(t *Table) *Table {
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data := cc.marshalAttr([]netlink.Attribute{
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{Type: unix.NFTA_TABLE_NAME, Data: []byte(t.Name + "\x00")},
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{Type: unix.NFTA_TABLE_FLAGS, Data: []byte{0, 0, 0, 0}},
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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: netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_NEWTABLE),
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Flags: netlink.HeaderFlagsRequest | netlink.HeaderFlagsAcknowledge | netlink.HeaderFlagsCreate,
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},
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Data: append(extraHeader(uint8(t.Family), 0), data...),
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})
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return t
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}
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// Flush sends all buffered commands in a single batch to nftables.
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func (cc *Conn) Flush() error {
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if cc.err != nil {
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return cc.err // serialization error
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}
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var conn *netlink.Conn
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var err error
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if cc.TestDial == nil {
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conn, err = netlink.Dial(unix.NETLINK_NETFILTER, nil)
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} else {
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conn = nltest.Dial(cc.TestDial)
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}
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if err != nil {
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return err
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}
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if _, err := conn.SendMessages(batch(cc.messages)); err != nil {
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return fmt.Errorf("SendMessages: %v", err)
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}
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if _, err := conn.Receive(); err != nil {
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return fmt.Errorf("Receive: %v", err)
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}
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cc.messages = nil
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return nil
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}
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