/
iptables.go
299 lines (263 loc) · 7.66 KB
/
iptables.go
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package iptables
import (
"errors"
"fmt"
"net"
"os/exec"
"regexp"
"strconv"
"strings"
log "github.com/Sirupsen/logrus"
)
type Action string
type Table string
const (
Append Action = "-A"
Delete Action = "-D"
Insert Action = "-I"
Nat Table = "nat"
Filter Table = "filter"
Mangle Table = "mangle"
)
var (
iptablesPath string
supportsXlock = false
ErrIptablesNotFound = errors.New("Iptables not found")
)
type Chain struct {
Name string
Bridge string
Table Table
}
type ChainError struct {
Chain string
Output []byte
}
func (e *ChainError) Error() string {
return fmt.Sprintf("Error iptables %s: %s", e.Chain, string(e.Output))
}
func initCheck() error {
if iptablesPath == "" {
path, err := exec.LookPath("iptables")
if err != nil {
return ErrIptablesNotFound
}
iptablesPath = path
supportsXlock = exec.Command(iptablesPath, "--wait", "-L", "-n").Run() == nil
}
return nil
}
func NewChain(name, bridge string, table Table) (*Chain, error) {
c := &Chain{
Name: name,
Bridge: bridge,
Table: table,
}
if string(c.Table) == "" {
c.Table = Filter
}
// Add chain if it doesn't exist
if _, err := Raw("-t", string(c.Table), "-n", "-L", c.Name); err != nil {
if output, err := Raw("-t", string(c.Table), "-N", c.Name); err != nil {
return nil, err
} else if len(output) != 0 {
return nil, fmt.Errorf("Could not create %s/%s chain: %s", c.Table, c.Name, output)
}
}
switch table {
case Nat:
preroute := []string{
"-m", "addrtype",
"--dst-type", "LOCAL"}
if !Exists(Nat, "PREROUTING", preroute...) {
if err := c.Prerouting(Append, preroute...); err != nil {
return nil, fmt.Errorf("Failed to inject docker in PREROUTING chain: %s", err)
}
}
output := []string{
"-m", "addrtype",
"--dst-type", "LOCAL",
"!", "--dst", "127.0.0.0/8"}
if !Exists(Nat, "OUTPUT", output...) {
if err := c.Output(Append, output...); err != nil {
return nil, fmt.Errorf("Failed to inject docker in OUTPUT chain: %s", err)
}
}
case Filter:
link := []string{
"-o", c.Bridge,
"-j", c.Name}
if !Exists(Filter, "FORWARD", link...) {
insert := append([]string{string(Insert), "FORWARD"}, link...)
if output, err := Raw(insert...); err != nil {
return nil, err
} else if len(output) != 0 {
return nil, fmt.Errorf("Could not create linking rule to %s/%s: %s", c.Table, c.Name, output)
}
}
}
return c, nil
}
func RemoveExistingChain(name string, table Table) error {
c := &Chain{
Name: name,
Table: table,
}
if string(c.Table) == "" {
c.Table = Filter
}
return c.Remove()
}
// Add forwarding rule to 'filter' table and corresponding nat rule to 'nat' table
func (c *Chain) Forward(action Action, ip net.IP, port int, proto, destAddr string, destPort int) error {
daddr := ip.String()
if ip.IsUnspecified() {
// iptables interprets "0.0.0.0" as "0.0.0.0/32", whereas we
// want "0.0.0.0/0". "0/0" is correctly interpreted as "any
// value" by both iptables and ip6tables.
daddr = "0/0"
}
if output, err := Raw("-t", string(Nat), string(action), c.Name,
"-p", proto,
"-d", daddr,
"--dport", strconv.Itoa(port),
"!", "-i", c.Bridge,
"-j", "DNAT",
"--to-destination", net.JoinHostPort(destAddr, strconv.Itoa(destPort))); err != nil {
return err
} else if len(output) != 0 {
return &ChainError{Chain: "FORWARD", Output: output}
}
if output, err := Raw("-t", string(Filter), string(action), c.Name,
"!", "-i", c.Bridge,
"-o", c.Bridge,
"-p", proto,
"-d", destAddr,
"--dport", strconv.Itoa(destPort),
"-j", "ACCEPT"); err != nil {
return err
} else if len(output) != 0 {
return &ChainError{Chain: "FORWARD", Output: output}
}
if output, err := Raw("-t", string(Nat), string(action), "POSTROUTING",
"-p", proto,
"-s", destAddr,
"-d", destAddr,
"--dport", strconv.Itoa(destPort),
"-j", "MASQUERADE"); err != nil {
return err
} else if len(output) != 0 {
return &ChainError{Chain: "FORWARD", Output: output}
}
return nil
}
// Add reciprocal ACCEPT rule for two supplied IP addresses.
// Traffic is allowed from ip1 to ip2 and vice-versa
func (c *Chain) Link(action Action, ip1, ip2 net.IP, port int, proto string) error {
if output, err := Raw("-t", string(Filter), string(action), c.Name,
"-i", c.Bridge, "-o", c.Bridge,
"-p", proto,
"-s", ip1.String(),
"-d", ip2.String(),
"--dport", strconv.Itoa(port),
"-j", "ACCEPT"); err != nil {
return err
} else if len(output) != 0 {
return fmt.Errorf("Error iptables forward: %s", output)
}
if output, err := Raw("-t", string(Filter), string(action), c.Name,
"-i", c.Bridge, "-o", c.Bridge,
"-p", proto,
"-s", ip2.String(),
"-d", ip1.String(),
"--sport", strconv.Itoa(port),
"-j", "ACCEPT"); err != nil {
return err
} else if len(output) != 0 {
return fmt.Errorf("Error iptables forward: %s", output)
}
return nil
}
// Add linking rule to nat/PREROUTING chain.
func (c *Chain) Prerouting(action Action, args ...string) error {
a := []string{"-t", string(Nat), string(action), "PREROUTING"}
if len(args) > 0 {
a = append(a, args...)
}
if output, err := Raw(append(a, "-j", c.Name)...); err != nil {
return err
} else if len(output) != 0 {
return &ChainError{Chain: "PREROUTING", Output: output}
}
return nil
}
// Add linking rule to an OUTPUT chain
func (c *Chain) Output(action Action, args ...string) error {
a := []string{"-t", string(c.Table), string(action), "OUTPUT"}
if len(args) > 0 {
a = append(a, args...)
}
if output, err := Raw(append(a, "-j", c.Name)...); err != nil {
return err
} else if len(output) != 0 {
return &ChainError{Chain: "OUTPUT", Output: output}
}
return nil
}
func (c *Chain) Remove() error {
// Ignore errors - This could mean the chains were never set up
if c.Table == Nat {
c.Prerouting(Delete, "-m", "addrtype", "--dst-type", "LOCAL")
c.Output(Delete, "-m", "addrtype", "--dst-type", "LOCAL", "!", "--dst", "127.0.0.0/8")
c.Output(Delete, "-m", "addrtype", "--dst-type", "LOCAL") // Created in versions <= 0.1.6
c.Prerouting(Delete)
c.Output(Delete)
}
Raw("-t", string(c.Table), "-F", c.Name)
Raw("-t", string(c.Table), "-X", c.Name)
return nil
}
// Check if a rule exists
func Exists(table Table, chain string, rule ...string) bool {
if string(table) == "" {
table = Filter
}
// iptables -C, --check option was added in v.1.4.11
// http://ftp.netfilter.org/pub/iptables/changes-iptables-1.4.11.txt
// try -C
// if exit status is 0 then return true, the rule exists
if _, err := Raw(append([]string{
"-t", string(table), "-C", chain}, rule...)...); err == nil {
return true
}
// parse "iptables -S" for the rule (this checks rules in a specific chain
// in a specific table)
rule_string := strings.Join(rule, " ")
existingRules, _ := exec.Command("iptables", "-t", string(table), "-S", chain).Output()
// regex to replace ips in rule
// because MASQUERADE rule will not be exactly what was passed
re := regexp.MustCompile(`[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\/[0-9]{1,2}`)
return strings.Contains(
re.ReplaceAllString(string(existingRules), "?"),
re.ReplaceAllString(rule_string, "?"),
)
}
// Call 'iptables' system command, passing supplied arguments
func Raw(args ...string) ([]byte, error) {
if err := initCheck(); err != nil {
return nil, err
}
if supportsXlock {
args = append([]string{"--wait"}, args...)
}
log.Debugf("%s, %v", iptablesPath, args)
output, err := exec.Command(iptablesPath, args...).CombinedOutput()
if err != nil {
return nil, fmt.Errorf("iptables failed: iptables %v: %s (%s)", strings.Join(args, " "), output, err)
}
// ignore iptables' message about xtables lock
if strings.Contains(string(output), "waiting for it to exit") {
output = []byte("")
}
return output, err
}