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// +build linux
// Copyright 2016 CNI authors
//
// 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.
// This is a "meta-plugin". It reads in its own netconf, it does not create
// any network interface but just changes the network sysctl.
package firewall
import (
"fmt"
"net"
"github.com/coreos/go-iptables/iptables"
)
func getPrivChainRules(ip string) [][]string {
var rules [][]string
rules = append(rules, []string{"-d", ip, "-m", "conntrack", "--ctstate", "RELATED,ESTABLISHED", "-j", "ACCEPT"})
rules = append(rules, []string{"-s", ip, "-j", "ACCEPT"})
return rules
}
func ensureChain(ipt *iptables.IPTables, table, chain string) error {
chains, err := ipt.ListChains(table)
if err != nil {
return fmt.Errorf("failed to list iptables chains: %v", err)
}
for _, ch := range chains {
if ch == chain {
return nil
}
}
return ipt.NewChain(table, chain)
}
func generateFilterRule(privChainName string) []string {
return []string{"-m", "comment", "--comment", "CNI firewall plugin rules", "-j", privChainName}
}
func cleanupRules(ipt *iptables.IPTables, privChainName string, rules [][]string) {
for _, rule := range rules {
ipt.Delete("filter", privChainName, rule...)
}
}
func ensureFirstChainRule(ipt *iptables.IPTables, chain string, rule []string) error {
exists, err := ipt.Exists("filter", chain, rule...)
if !exists && err == nil {
err = ipt.Insert("filter", chain, 1, rule...)
}
return err
}
func (ib *iptablesBackend) setupChains(ipt *iptables.IPTables) error {
privRule := generateFilterRule(ib.privChainName)
adminRule := generateFilterRule(ib.adminChainName)
// Ensure our private chains exist
if err := ensureChain(ipt, "filter", ib.privChainName); err != nil {
return err
}
if err := ensureChain(ipt, "filter", ib.adminChainName); err != nil {
return err
}
// Ensure our filter rule exists in the forward chain
if err := ensureFirstChainRule(ipt, "FORWARD", privRule); err != nil {
return err
}
// Ensure our admin override chain rule exists in our private chain
if err := ensureFirstChainRule(ipt, ib.privChainName, adminRule); err != nil {
return err
}
return nil
}
func protoForIP(ip net.IPNet) iptables.Protocol {
if ip.IP.To4() != nil {
return iptables.ProtocolIPv4
}
return iptables.ProtocolIPv6
}
func (ib *iptablesBackend) addRules(conf *FirewallNetConf, ipt *iptables.IPTables, proto iptables.Protocol) error {
rules := make([][]string, 0)
for _, ip := range conf.PrevResult.IPs {
if protoForIP(ip.Address) == proto {
rules = append(rules, getPrivChainRules(ipString(ip.Address))...)
}
}
if len(rules) > 0 {
if err := ib.setupChains(ipt); err != nil {
return err
}
// Clean up on any errors
var err error
defer func() {
if err != nil {
cleanupRules(ipt, ib.privChainName, rules)
}
}()
for _, rule := range rules {
err = ipt.AppendUnique("filter", ib.privChainName, rule...)
if err != nil {
return err
}
}
}
return nil
}
func (ib *iptablesBackend) delRules(conf *FirewallNetConf, ipt *iptables.IPTables, proto iptables.Protocol) error {
rules := make([][]string, 0)
for _, ip := range conf.PrevResult.IPs {
if protoForIP(ip.Address) == proto {
rules = append(rules, getPrivChainRules(ipString(ip.Address))...)
}
}
if len(rules) > 0 {
cleanupRules(ipt, ib.privChainName, rules)
}
return nil
}
type iptablesBackend struct {
protos map[iptables.Protocol]*iptables.IPTables
privChainName string
adminChainName string
ifName string
}
// iptablesBackend implements the FirewallBackend interface
var _ FirewallBackend = &iptablesBackend{}
func newIptablesBackend() (FirewallBackend, error) {
adminChainName := "CNI-ADMIN"
backend := &iptablesBackend{
privChainName: "CNI-FORWARD",
adminChainName: adminChainName,
protos: make(map[iptables.Protocol]*iptables.IPTables),
}
for _, proto := range []iptables.Protocol{iptables.ProtocolIPv4, iptables.ProtocolIPv6} {
ipt, err := iptables.NewWithProtocol(proto)
if err != nil {
return nil, fmt.Errorf("could not initialize iptables protocol %v: %v", proto, err)
}
backend.protos[proto] = ipt
}
return backend, nil
}
func (ib *iptablesBackend) Add(conf *FirewallNetConf) error {
for proto, ipt := range ib.protos {
if err := ib.addRules(conf, ipt, proto); err != nil {
return err
}
}
return nil
}
func (ib *iptablesBackend) Del(conf *FirewallNetConf) error {
for proto, ipt := range ib.protos {
ib.delRules(conf, ipt, proto)
}
return nil
}
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