1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491
|
// 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 main
import (
"fmt"
"log"
"math/rand"
"net"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/d2g/dhcp4"
"github.com/d2g/dhcp4client"
"github.com/vishvananda/netlink"
"github.com/containernetworking/cni/pkg/types"
"github.com/containernetworking/plugins/pkg/ns"
)
// RFC 2131 suggests using exponential backoff, starting with 4sec
// and randomized to +/- 1sec
const resendDelay0 = 4 * time.Second
const resendDelayMax = 62 * time.Second
// To speed up the retry for first few failures, we retry without
// backoff for a few times
const resendFastDelay = 2 * time.Second
const resendFastMax = 4
const (
leaseStateBound = iota
leaseStateRenewing
leaseStateRebinding
)
// This implementation uses 1 OS thread per lease. This is because
// all the network operations have to be done in network namespace
// of the interface. This can be improved by switching to the proper
// namespace for network ops and using fewer threads. However, this
// needs to be done carefully as dhcp4client ops are blocking.
type DHCPLease struct {
clientID string
ack *dhcp4.Packet
opts dhcp4.Options
link netlink.Link
renewalTime time.Time
rebindingTime time.Time
expireTime time.Time
timeout time.Duration
resendMax time.Duration
broadcast bool
stopping uint32
stop chan struct{}
wg sync.WaitGroup
// list of requesting and providing options and if they are necessary / their value
optsRequesting map[dhcp4.OptionCode]bool
optsProviding map[dhcp4.OptionCode][]byte
}
var requestOptionsDefault = map[dhcp4.OptionCode]bool{
dhcp4.OptionRouter: true,
dhcp4.OptionSubnetMask: true,
}
func prepareOptions(cniArgs string, ProvideOptions []ProvideOption, RequestOptions []RequestOption) (
optsRequesting map[dhcp4.OptionCode]bool, optsProviding map[dhcp4.OptionCode][]byte, err error) {
// parse CNI args
cniArgsParsed := map[string]string{}
for _, argPair := range strings.Split(cniArgs, ";") {
args := strings.SplitN(argPair, "=", 2)
if len(args) > 1 {
cniArgsParsed[args[0]] = args[1]
}
}
// parse providing options map
var optParsed dhcp4.OptionCode
optsProviding = make(map[dhcp4.OptionCode][]byte)
for _, opt := range ProvideOptions {
optParsed, err = parseOptionName(string(opt.Option))
if err != nil {
err = fmt.Errorf("Can not parse option %q: %w", opt.Option, err)
return
}
if len(opt.Value) > 0 {
if len(opt.Value) > 255 {
err = fmt.Errorf("value too long for option %q: %q", opt.Option, opt.Value)
return
}
optsProviding[optParsed] = []byte(opt.Value)
}
if value, ok := cniArgsParsed[opt.ValueFromCNIArg]; ok {
if len(value) > 255 {
err = fmt.Errorf("value too long for option %q from CNI_ARGS %q: %q", opt.Option, opt.ValueFromCNIArg, opt.Value)
return
}
optsProviding[optParsed] = []byte(value)
}
}
// parse necessary options map
optsRequesting = make(map[dhcp4.OptionCode]bool)
skipRequireDefault := false
for _, opt := range RequestOptions {
if opt.SkipDefault {
skipRequireDefault = true
}
optParsed, err = parseOptionName(string(opt.Option))
if err != nil {
err = fmt.Errorf("Can not parse option %q: %w", opt.Option, err)
return
}
optsRequesting[optParsed] = true
}
for k, v := range requestOptionsDefault {
// only set if not skipping default and this value does not exists
if _, ok := optsRequesting[k]; !ok && !skipRequireDefault {
optsRequesting[k] = v
}
}
return
}
// AcquireLease gets an DHCP lease and then maintains it in the background
// by periodically renewing it. The acquired lease can be released by
// calling DHCPLease.Stop()
func AcquireLease(
clientID, netns, ifName string,
optsRequesting map[dhcp4.OptionCode]bool, optsProviding map[dhcp4.OptionCode][]byte,
timeout, resendMax time.Duration, broadcast bool,
) (*DHCPLease, error) {
errCh := make(chan error, 1)
l := &DHCPLease{
clientID: clientID,
stop: make(chan struct{}),
timeout: timeout,
resendMax: resendMax,
broadcast: broadcast,
optsRequesting: optsRequesting,
optsProviding: optsProviding,
}
log.Printf("%v: acquiring lease", clientID)
l.wg.Add(1)
go func() {
errCh <- ns.WithNetNSPath(netns, func(_ ns.NetNS) error {
defer l.wg.Done()
link, err := netlink.LinkByName(ifName)
if err != nil {
return fmt.Errorf("error looking up %q: %v", ifName, err)
}
l.link = link
if err = l.acquire(); err != nil {
return err
}
log.Printf("%v: lease acquired, expiration is %v", l.clientID, l.expireTime)
errCh <- nil
l.maintain()
return nil
})
}()
if err := <-errCh; err != nil {
return nil, err
}
return l, nil
}
// Stop terminates the background task that maintains the lease
// and issues a DHCP Release
func (l *DHCPLease) Stop() {
if atomic.CompareAndSwapUint32(&l.stopping, 0, 1) {
close(l.stop)
}
l.wg.Wait()
}
func (l *DHCPLease) getOptionsWithClientId() dhcp4.Options {
opts := make(dhcp4.Options)
opts[dhcp4.OptionClientIdentifier] = []byte(l.clientID)
// client identifier's first byte is "type"
newClientID := []byte{0}
newClientID = append(newClientID, opts[dhcp4.OptionClientIdentifier]...)
opts[dhcp4.OptionClientIdentifier] = newClientID
return opts
}
func (l *DHCPLease) getAllOptions() dhcp4.Options {
opts := l.getOptionsWithClientId()
for k, v := range l.optsProviding {
opts[k] = v
}
opts[dhcp4.OptionParameterRequestList] = []byte{}
for k := range l.optsRequesting {
opts[dhcp4.OptionParameterRequestList] = append(opts[dhcp4.OptionParameterRequestList], byte(k))
}
return opts
}
func (l *DHCPLease) acquire() error {
c, err := newDHCPClient(l.link, l.clientID, l.timeout, l.broadcast)
if err != nil {
return err
}
defer c.Close()
if (l.link.Attrs().Flags & net.FlagUp) != net.FlagUp {
log.Printf("Link %q down. Attempting to set up", l.link.Attrs().Name)
if err = netlink.LinkSetUp(l.link); err != nil {
return err
}
}
opts := l.getAllOptions()
pkt, err := backoffRetry(l.resendMax, func() (*dhcp4.Packet, error) {
ok, ack, err := DhcpRequest(c, opts)
switch {
case err != nil:
return nil, err
case !ok:
return nil, fmt.Errorf("DHCP server NACK'd own offer")
default:
return &ack, nil
}
})
if err != nil {
return err
}
return l.commit(pkt)
}
func (l *DHCPLease) commit(ack *dhcp4.Packet) error {
opts := ack.ParseOptions()
leaseTime, err := parseLeaseTime(opts)
if err != nil {
return err
}
rebindingTime, err := parseRebindingTime(opts)
if err != nil || rebindingTime > leaseTime {
// Per RFC 2131 Section 4.4.5, it should default to 85% of lease time
rebindingTime = leaseTime * 85 / 100
}
renewalTime, err := parseRenewalTime(opts)
if err != nil || renewalTime > rebindingTime {
// Per RFC 2131 Section 4.4.5, it should default to 50% of lease time
renewalTime = leaseTime / 2
}
now := time.Now()
l.expireTime = now.Add(leaseTime)
l.renewalTime = now.Add(renewalTime)
l.rebindingTime = now.Add(rebindingTime)
l.ack = ack
l.opts = opts
return nil
}
func (l *DHCPLease) maintain() {
state := leaseStateBound
for {
var sleepDur time.Duration
switch state {
case leaseStateBound:
sleepDur = l.renewalTime.Sub(time.Now())
if sleepDur <= 0 {
log.Printf("%v: renewing lease", l.clientID)
state = leaseStateRenewing
continue
}
case leaseStateRenewing:
if err := l.renew(); err != nil {
log.Printf("%v: %v", l.clientID, err)
if time.Now().After(l.rebindingTime) {
log.Printf("%v: renawal time expired, rebinding", l.clientID)
state = leaseStateRebinding
}
} else {
log.Printf("%v: lease renewed, expiration is %v", l.clientID, l.expireTime)
state = leaseStateBound
}
case leaseStateRebinding:
if err := l.acquire(); err != nil {
log.Printf("%v: %v", l.clientID, err)
if time.Now().After(l.expireTime) {
log.Printf("%v: lease expired, bringing interface DOWN", l.clientID)
l.downIface()
return
}
} else {
log.Printf("%v: lease rebound, expiration is %v", l.clientID, l.expireTime)
state = leaseStateBound
}
}
select {
case <-time.After(sleepDur):
case <-l.stop:
if err := l.release(); err != nil {
log.Printf("%v: failed to release DHCP lease: %v", l.clientID, err)
}
return
}
}
}
func (l *DHCPLease) downIface() {
if err := netlink.LinkSetDown(l.link); err != nil {
log.Printf("%v: failed to bring %v interface DOWN: %v", l.clientID, l.link.Attrs().Name, err)
}
}
func (l *DHCPLease) renew() error {
c, err := newDHCPClient(l.link, l.clientID, l.timeout, l.broadcast)
if err != nil {
return err
}
defer c.Close()
opts := l.getOptionsWithClientId()
pkt, err := backoffRetry(l.resendMax, func() (*dhcp4.Packet, error) {
ok, ack, err := DhcpRenew(c, *l.ack, opts)
switch {
case err != nil:
return nil, err
case !ok:
return nil, fmt.Errorf("DHCP server did not renew lease")
default:
return &ack, nil
}
})
if err != nil {
return err
}
l.commit(pkt)
return nil
}
func (l *DHCPLease) release() error {
log.Printf("%v: releasing lease", l.clientID)
c, err := newDHCPClient(l.link, l.clientID, l.timeout, l.broadcast)
if err != nil {
return err
}
defer c.Close()
opts := l.getOptionsWithClientId()
if err = DhcpRelease(c, *l.ack, opts); err != nil {
return fmt.Errorf("failed to send DHCPRELEASE")
}
return nil
}
func (l *DHCPLease) IPNet() (*net.IPNet, error) {
mask := parseSubnetMask(l.opts)
if mask == nil {
return nil, fmt.Errorf("DHCP option Subnet Mask not found in DHCPACK")
}
return &net.IPNet{
IP: l.ack.YIAddr(),
Mask: mask,
}, nil
}
func (l *DHCPLease) Gateway() net.IP {
return parseRouter(l.opts)
}
func (l *DHCPLease) Routes() []*types.Route {
routes := []*types.Route{}
// RFC 3442 states that if Classless Static Routes (option 121)
// exist, we ignore Static Routes (option 33) and the Router/Gateway.
opt121_routes := parseCIDRRoutes(l.opts)
if len(opt121_routes) > 0 {
return append(routes, opt121_routes...)
}
// Append Static Routes
routes = append(routes, parseRoutes(l.opts)...)
// The CNI spec says even if there is a gateway specified, we must
// add a default route in the routes section.
if gw := l.Gateway(); gw != nil {
_, defaultRoute, _ := net.ParseCIDR("0.0.0.0/0")
routes = append(routes, &types.Route{Dst: *defaultRoute, GW: gw})
}
return routes
}
// jitter returns a random value within [-span, span) range
func jitter(span time.Duration) time.Duration {
return time.Duration(float64(span) * (2.0*rand.Float64() - 1.0))
}
func backoffRetry(resendMax time.Duration, f func() (*dhcp4.Packet, error)) (*dhcp4.Packet, error) {
var baseDelay time.Duration = resendDelay0
var sleepTime time.Duration
var fastRetryLimit = resendFastMax
for {
pkt, err := f()
if err == nil {
return pkt, nil
}
log.Print(err)
if fastRetryLimit == 0 {
sleepTime = baseDelay + jitter(time.Second)
} else {
sleepTime = resendFastDelay + jitter(time.Second)
fastRetryLimit--
}
log.Printf("retrying in %f seconds", sleepTime.Seconds())
time.Sleep(sleepTime)
// only adjust delay time if we are in normal backoff stage
if baseDelay < resendMax && fastRetryLimit == 0 {
baseDelay *= 2
} else if fastRetryLimit == 0 { // only break if we are at normal delay
break
}
}
return nil, errNoMoreTries
}
func newDHCPClient(
link netlink.Link, clientID string,
timeout time.Duration,
broadcast bool,
) (*dhcp4client.Client, error) {
pktsock, err := dhcp4client.NewPacketSock(link.Attrs().Index)
if err != nil {
return nil, err
}
return dhcp4client.New(
dhcp4client.HardwareAddr(link.Attrs().HardwareAddr),
dhcp4client.Timeout(timeout),
dhcp4client.Broadcast(broadcast),
dhcp4client.Connection(pktsock),
)
}
|