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moby--moby/libnetwork/iptables/iptables.go
Danny Milosavljevic 6b5dc55e93 Use fewer modprobes
Signed-off-by: Danny Milosavljevic <dannym@scratchpost.org>
2019-04-10 17:32:39 +02:00

577 lines
16 KiB
Go

package iptables
import (
"errors"
"fmt"
"net"
"os/exec"
"regexp"
"strconv"
"strings"
"sync"
"time"
"github.com/sirupsen/logrus"
)
// Action signifies the iptable action.
type Action string
// Policy is the default iptable policies
type Policy string
// Table refers to Nat, Filter or Mangle.
type Table string
const (
// Append appends the rule at the end of the chain.
Append Action = "-A"
// Delete deletes the rule from the chain.
Delete Action = "-D"
// Insert inserts the rule at the top of the chain.
Insert Action = "-I"
// Nat table is used for nat translation rules.
Nat Table = "nat"
// Filter table is used for filter rules.
Filter Table = "filter"
// Mangle table is used for mangling the packet.
Mangle Table = "mangle"
// Drop is the default iptables DROP policy
Drop Policy = "DROP"
// Accept is the default iptables ACCEPT policy
Accept Policy = "ACCEPT"
)
var (
iptablesPath string
supportsXlock = false
supportsCOpt = false
xLockWaitMsg = "Another app is currently holding the xtables lock"
// used to lock iptables commands if xtables lock is not supported
bestEffortLock sync.Mutex
// ErrIptablesNotFound is returned when the rule is not found.
ErrIptablesNotFound = errors.New("Iptables not found")
initOnce sync.Once
)
// ChainInfo defines the iptables chain.
type ChainInfo struct {
Name string
Table Table
HairpinMode bool
}
// ChainError is returned to represent errors during ip table operation.
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 probe() {
path, err := exec.LookPath("iptables")
if err != nil {
logrus.Warnf("Failed to find iptables: %v", err)
return
}
if out, err := exec.Command(path, "--wait", "-t", "nat", "-L", "-n").CombinedOutput(); err != nil {
logrus.Warnf("Running iptables --wait -t nat -L -n failed with message: `%s`, error: %v", strings.TrimSpace(string(out)), err)
}
}
func initFirewalld() {
if err := FirewalldInit(); err != nil {
logrus.Debugf("Fail to initialize firewalld: %v, using raw iptables instead", err)
}
}
func detectIptables() {
path, err := exec.LookPath("iptables")
if err != nil {
return
}
iptablesPath = path
supportsXlock = exec.Command(iptablesPath, "--wait", "-L", "-n").Run() == nil
mj, mn, mc, err := GetVersion()
if err != nil {
logrus.Warnf("Failed to read iptables version: %v", err)
return
}
supportsCOpt = supportsCOption(mj, mn, mc)
}
func initDependencies() {
probe()
initFirewalld()
detectIptables()
}
func initCheck() error {
initOnce.Do(initDependencies)
if iptablesPath == "" {
return ErrIptablesNotFound
}
return nil
}
// NewChain adds a new chain to ip table.
func NewChain(name string, table Table, hairpinMode bool) (*ChainInfo, error) {
c := &ChainInfo{
Name: name,
Table: table,
HairpinMode: hairpinMode,
}
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)
}
}
return c, nil
}
// ProgramChain is used to add rules to a chain
func ProgramChain(c *ChainInfo, bridgeName string, hairpinMode, enable bool) error {
if c.Name == "" {
return errors.New("Could not program chain, missing chain name")
}
switch c.Table {
case Nat:
preroute := []string{
"-m", "addrtype",
"--dst-type", "LOCAL",
"-j", c.Name}
if !Exists(Nat, "PREROUTING", preroute...) && enable {
if err := c.Prerouting(Append, preroute...); err != nil {
return fmt.Errorf("Failed to inject %s in PREROUTING chain: %s", c.Name, err)
}
} else if Exists(Nat, "PREROUTING", preroute...) && !enable {
if err := c.Prerouting(Delete, preroute...); err != nil {
return fmt.Errorf("Failed to remove %s in PREROUTING chain: %s", c.Name, err)
}
}
output := []string{
"-m", "addrtype",
"--dst-type", "LOCAL",
"-j", c.Name}
if !hairpinMode {
output = append(output, "!", "--dst", "127.0.0.0/8")
}
if !Exists(Nat, "OUTPUT", output...) && enable {
if err := c.Output(Append, output...); err != nil {
return fmt.Errorf("Failed to inject %s in OUTPUT chain: %s", c.Name, err)
}
} else if Exists(Nat, "OUTPUT", output...) && !enable {
if err := c.Output(Delete, output...); err != nil {
return fmt.Errorf("Failed to inject %s in OUTPUT chain: %s", c.Name, err)
}
}
case Filter:
if bridgeName == "" {
return fmt.Errorf("Could not program chain %s/%s, missing bridge name",
c.Table, c.Name)
}
link := []string{
"-o", bridgeName,
"-j", c.Name}
if !Exists(Filter, "FORWARD", link...) && enable {
insert := append([]string{string(Insert), "FORWARD"}, link...)
if output, err := Raw(insert...); err != nil {
return err
} else if len(output) != 0 {
return fmt.Errorf("Could not create linking rule to %s/%s: %s", c.Table, c.Name, output)
}
} else if Exists(Filter, "FORWARD", link...) && !enable {
del := append([]string{string(Delete), "FORWARD"}, link...)
if output, err := Raw(del...); err != nil {
return err
} else if len(output) != 0 {
return fmt.Errorf("Could not delete linking rule from %s/%s: %s", c.Table, c.Name, output)
}
}
establish := []string{
"-o", bridgeName,
"-m", "conntrack",
"--ctstate", "RELATED,ESTABLISHED",
"-j", "ACCEPT"}
if !Exists(Filter, "FORWARD", establish...) && enable {
insert := append([]string{string(Insert), "FORWARD"}, establish...)
if output, err := Raw(insert...); err != nil {
return err
} else if len(output) != 0 {
return fmt.Errorf("Could not create establish rule to %s: %s", c.Table, output)
}
} else if Exists(Filter, "FORWARD", establish...) && !enable {
del := append([]string{string(Delete), "FORWARD"}, establish...)
if output, err := Raw(del...); err != nil {
return err
} else if len(output) != 0 {
return fmt.Errorf("Could not delete establish rule from %s: %s", c.Table, output)
}
}
}
return nil
}
// RemoveExistingChain removes existing chain from the table.
func RemoveExistingChain(name string, table Table) error {
c := &ChainInfo{
Name: name,
Table: table,
}
if string(c.Table) == "" {
c.Table = Filter
}
return c.Remove()
}
// Forward adds forwarding rule to 'filter' table and corresponding nat rule to 'nat' table.
func (c *ChainInfo) Forward(action Action, ip net.IP, port int, proto, destAddr string, destPort int, bridgeName string) 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"
}
args := []string{
"-p", proto,
"-d", daddr,
"--dport", strconv.Itoa(port),
"-j", "DNAT",
"--to-destination", net.JoinHostPort(destAddr, strconv.Itoa(destPort))}
if !c.HairpinMode {
args = append(args, "!", "-i", bridgeName)
}
if err := ProgramRule(Nat, c.Name, action, args); err != nil {
return err
}
args = []string{
"!", "-i", bridgeName,
"-o", bridgeName,
"-p", proto,
"-d", destAddr,
"--dport", strconv.Itoa(destPort),
"-j", "ACCEPT",
}
if err := ProgramRule(Filter, c.Name, action, args); err != nil {
return err
}
args = []string{
"-p", proto,
"-s", destAddr,
"-d", destAddr,
"--dport", strconv.Itoa(destPort),
"-j", "MASQUERADE",
}
if err := ProgramRule(Nat, "POSTROUTING", action, args); err != nil {
return err
}
if proto == "sctp" {
// Linux kernel v4.9 and below enables NETIF_F_SCTP_CRC for veth by
// the following commit.
// This introduces a problem when conbined with a physical NIC without
// NETIF_F_SCTP_CRC. As for a workaround, here we add an iptables entry
// to fill the checksum.
//
// https://github.com/torvalds/linux/commit/c80fafbbb59ef9924962f83aac85531039395b18
args = []string{
"-p", proto,
"--sport", strconv.Itoa(destPort),
"-j", "CHECKSUM",
"--checksum-fill",
}
if err := ProgramRule(Mangle, "POSTROUTING", action, args); err != nil {
return err
}
}
return nil
}
// Link adds reciprocal ACCEPT rule for two supplied IP addresses.
// Traffic is allowed from ip1 to ip2 and vice-versa
func (c *ChainInfo) Link(action Action, ip1, ip2 net.IP, port int, proto string, bridgeName string) error {
// forward
args := []string{
"-i", bridgeName, "-o", bridgeName,
"-p", proto,
"-s", ip1.String(),
"-d", ip2.String(),
"--dport", strconv.Itoa(port),
"-j", "ACCEPT",
}
if err := ProgramRule(Filter, c.Name, action, args); err != nil {
return err
}
// reverse
args[7], args[9] = args[9], args[7]
args[10] = "--sport"
return ProgramRule(Filter, c.Name, action, args)
}
// ProgramRule adds the rule specified by args only if the
// rule is not already present in the chain. Reciprocally,
// it removes the rule only if present.
func ProgramRule(table Table, chain string, action Action, args []string) error {
if Exists(table, chain, args...) != (action == Delete) {
return nil
}
return RawCombinedOutput(append([]string{"-t", string(table), string(action), chain}, args...)...)
}
// Prerouting adds linking rule to nat/PREROUTING chain.
func (c *ChainInfo) 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(a...); err != nil {
return err
} else if len(output) != 0 {
return ChainError{Chain: "PREROUTING", Output: output}
}
return nil
}
// Output adds linking rule to an OUTPUT chain.
func (c *ChainInfo) 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(a...); err != nil {
return err
} else if len(output) != 0 {
return ChainError{Chain: "OUTPUT", Output: output}
}
return nil
}
// Remove removes the chain.
func (c *ChainInfo) 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", "-j", c.Name)
c.Output(Delete, "-m", "addrtype", "--dst-type", "LOCAL", "!", "--dst", "127.0.0.0/8", "-j", c.Name)
c.Output(Delete, "-m", "addrtype", "--dst-type", "LOCAL", "-j", c.Name) // 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
}
// Exists checks if a rule exists
func Exists(table Table, chain string, rule ...string) bool {
return exists(false, table, chain, rule...)
}
// ExistsNative behaves as Exists with the difference it
// will always invoke `iptables` binary.
func ExistsNative(table Table, chain string, rule ...string) bool {
return exists(true, table, chain, rule...)
}
func exists(native bool, table Table, chain string, rule ...string) bool {
f := Raw
if native {
f = raw
}
if string(table) == "" {
table = Filter
}
if err := initCheck(); err != nil {
// The exists() signature does not allow us to return an error, but at least
// we can skip the (likely invalid) exec invocation.
return false
}
if supportsCOpt {
// if exit status is 0 then return true, the rule exists
_, err := f(append([]string{"-t", string(table), "-C", chain}, rule...)...)
return err == nil
}
// parse "iptables -S" for the rule (it checks rules in a specific chain
// in a specific table and it is very unreliable)
return existsRaw(table, chain, rule...)
}
func existsRaw(table Table, chain string, rule ...string) bool {
ruleString := fmt.Sprintf("%s %s\n", chain, strings.Join(rule, " "))
existingRules, _ := exec.Command(iptablesPath, "-t", string(table), "-S", chain).Output()
return strings.Contains(string(existingRules), ruleString)
}
// Maximum duration that an iptables operation can take
// before flagging a warning.
const opWarnTime = 2 * time.Second
func filterOutput(start time.Time, output []byte, args ...string) []byte {
// Flag operations that have taken a long time to complete
opTime := time.Since(start)
if opTime > opWarnTime {
logrus.Warnf("xtables contention detected while running [%s]: Waited for %.2f seconds and received %q", strings.Join(args, " "), float64(opTime)/float64(time.Second), string(output))
}
// ignore iptables' message about xtables lock:
// it is a warning, not an error.
if strings.Contains(string(output), xLockWaitMsg) {
output = []byte("")
}
// Put further filters here if desired
return output
}
// Raw calls 'iptables' system command, passing supplied arguments.
func Raw(args ...string) ([]byte, error) {
if firewalldRunning {
startTime := time.Now()
output, err := Passthrough(Iptables, args...)
if err == nil || !strings.Contains(err.Error(), "was not provided by any .service files") {
return filterOutput(startTime, output, args...), err
}
}
return raw(args...)
}
func raw(args ...string) ([]byte, error) {
if err := initCheck(); err != nil {
return nil, err
}
if supportsXlock {
args = append([]string{"--wait"}, args...)
} else {
bestEffortLock.Lock()
defer bestEffortLock.Unlock()
}
logrus.Debugf("%s, %v", iptablesPath, args)
startTime := time.Now()
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)
}
return filterOutput(startTime, output, args...), err
}
// RawCombinedOutput internally calls the Raw function and returns a non nil
// error if Raw returned a non nil error or a non empty output
func RawCombinedOutput(args ...string) error {
if output, err := Raw(args...); err != nil || len(output) != 0 {
return fmt.Errorf("%s (%v)", string(output), err)
}
return nil
}
// RawCombinedOutputNative behave as RawCombinedOutput with the difference it
// will always invoke `iptables` binary
func RawCombinedOutputNative(args ...string) error {
if output, err := raw(args...); err != nil || len(output) != 0 {
return fmt.Errorf("%s (%v)", string(output), err)
}
return nil
}
// ExistChain checks if a chain exists
func ExistChain(chain string, table Table) bool {
if _, err := Raw("-t", string(table), "-nL", chain); err == nil {
return true
}
return false
}
// GetVersion reads the iptables version numbers during initialization
func GetVersion() (major, minor, micro int, err error) {
out, err := exec.Command(iptablesPath, "--version").CombinedOutput()
if err == nil {
major, minor, micro = parseVersionNumbers(string(out))
}
return
}
// SetDefaultPolicy sets the passed default policy for the table/chain
func SetDefaultPolicy(table Table, chain string, policy Policy) error {
if err := RawCombinedOutput("-t", string(table), "-P", chain, string(policy)); err != nil {
return fmt.Errorf("setting default policy to %v in %v chain failed: %v", policy, chain, err)
}
return nil
}
func parseVersionNumbers(input string) (major, minor, micro int) {
re := regexp.MustCompile(`v\d*.\d*.\d*`)
line := re.FindString(input)
fmt.Sscanf(line, "v%d.%d.%d", &major, &minor, &micro)
return
}
// iptables -C, --check option was added in v.1.4.11
// http://ftp.netfilter.org/pub/iptables/changes-iptables-1.4.11.txt
func supportsCOption(mj, mn, mc int) bool {
return mj > 1 || (mj == 1 && (mn > 4 || (mn == 4 && mc >= 11)))
}
// AddReturnRule adds a return rule for the chain in the filter table
func AddReturnRule(chain string) error {
var (
table = Filter
args = []string{"-j", "RETURN"}
)
if Exists(table, chain, args...) {
return nil
}
err := RawCombinedOutput(append([]string{"-A", chain}, args...)...)
if err != nil {
return fmt.Errorf("unable to add return rule in %s chain: %s", chain, err.Error())
}
return nil
}
// EnsureJumpRule ensures the jump rule is on top
func EnsureJumpRule(fromChain, toChain string) error {
var (
table = Filter
args = []string{"-j", toChain}
)
if Exists(table, fromChain, args...) {
err := RawCombinedOutput(append([]string{"-D", fromChain}, args...)...)
if err != nil {
return fmt.Errorf("unable to remove jump to %s rule in %s chain: %s", toChain, fromChain, err.Error())
}
}
err := RawCombinedOutput(append([]string{"-I", fromChain}, args...)...)
if err != nil {
return fmt.Errorf("unable to insert jump to %s rule in %s chain: %s", toChain, fromChain, err.Error())
}
return nil
}