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// Copyright 2015 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.
package ip
import (
"fmt"
"net"
"github.com/coreos/go-iptables/iptables"
)
// SetupIPMasq installs iptables rules to masquerade traffic
// coming from ip of ipn and going outside of ipn
func SetupIPMasq(ipn *net.IPNet, chain string, comment string) error {
isV6 := ipn.IP.To4() == nil
var ipt *iptables.IPTables
var err error
var multicastNet string
if isV6 {
ipt, err = iptables.NewWithProtocol(iptables.ProtocolIPv6)
multicastNet = "ff00::/8"
} else {
ipt, err = iptables.NewWithProtocol(iptables.ProtocolIPv4)
multicastNet = "224.0.0.0/4"
}
if err != nil {
return fmt.Errorf("failed to locate iptables: %v", err)
}
// Create chain if doesn't exist
exists := false
chains, err := ipt.ListChains("nat")
if err != nil {
return fmt.Errorf("failed to list chains: %v", err)
}
for _, ch := range chains {
if ch == chain {
exists = true
break
}
}
if !exists {
if err = ipt.NewChain("nat", chain); err != nil {
return err
}
}
// Packets to this network should not be touched
if err := ipt.AppendUnique("nat", chain, "-d", ipn.String(), "-j", "ACCEPT", "-m", "comment", "--comment", comment); err != nil {
return err
}
// Don't masquerade multicast - pods should be able to talk to other pods
// on the local network via multicast.
if err := ipt.AppendUnique("nat", chain, "!", "-d", multicastNet, "-j", "MASQUERADE", "-m", "comment", "--comment", comment); err != nil {
return err
}
// Packets from the specific IP of this network will hit the chain
return ipt.AppendUnique("nat", "POSTROUTING", "-s", ipn.IP.String(), "-j", chain, "-m", "comment", "--comment", comment)
}
// TeardownIPMasq undoes the effects of SetupIPMasq
func TeardownIPMasq(ipn *net.IPNet, chain string, comment string) error {
isV6 := ipn.IP.To4() == nil
var ipt *iptables.IPTables
var err error
if isV6 {
ipt, err = iptables.NewWithProtocol(iptables.ProtocolIPv6)
} else {
ipt, err = iptables.NewWithProtocol(iptables.ProtocolIPv4)
}
if err != nil {
return fmt.Errorf("failed to locate iptables: %v", err)
}
err = ipt.Delete("nat", "POSTROUTING", "-s", ipn.IP.String(), "-j", chain, "-m", "comment", "--comment", comment)
if err != nil && !isNotExist(err) {
return err
}
// for downward compatibility
err = ipt.Delete("nat", "POSTROUTING", "-s", ipn.String(), "-j", chain, "-m", "comment", "--comment", comment)
if err != nil && !isNotExist(err) {
return err
}
err = ipt.ClearChain("nat", chain)
if err != nil && !isNotExist(err) {
return err
}
err = ipt.DeleteChain("nat", chain)
if err != nil && !isNotExist(err) {
return err
}
return nil
}
// isNotExist returnst true if the error is from iptables indicating
// that the target does not exist.
func isNotExist(err error) bool {
e, ok := err.(*iptables.Error)
if !ok {
return false
}
return e.IsNotExist()
}
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