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package l2tp
import (
"fmt"
"github.com/go-kit/kit/log"
"github.com/go-kit/kit/log/level"
"sync"
)
type dynamicSession struct {
*baseSession
isClosed bool
established bool
callSerial uint32
ifname string
result string
dt *dynamicTunnel
dp SessionDataPlane
wg sync.WaitGroup
msgRxChan chan controlMessage
eventChan chan string
closeChan chan interface{}
killChan chan interface{}
fsm fsm
}
func (ds *dynamicSession) Close() {
ds.parent.unlinkSession(ds)
close(ds.closeChan)
ds.wg.Wait()
}
func (ds *dynamicSession) kill() {
ds.parent.unlinkSession(ds)
close(ds.killChan)
ds.wg.Wait()
}
func (ds *dynamicSession) onTunnelUp() {
ds.eventChan <- "tunnelopen"
}
func (ds *dynamicSession) handleCtlMsg(msg controlMessage) {
ds.msgRxChan <- msg
}
func (ds *dynamicSession) runSession() {
defer ds.wg.Done()
level.Info(ds.logger).Log(
"message", "new dynamic session",
"session_id", ds.cfg.SessionID,
"peer_session_id", ds.cfg.PeerSessionID,
"pseudowire", ds.cfg.Pseudowire)
for !ds.isClosed {
select {
case msg, ok := <-ds.msgRxChan:
if !ok {
ds.fsmActClose(nil)
return
}
ds.handleMsg(msg)
case ev, ok := <-ds.eventChan:
if !ok {
ds.fsmActClose(nil)
return
}
ds.handleEvent(ev)
case <-ds.killChan:
ds.fsmActClose(nil)
return
case <-ds.closeChan:
ds.handleEvent("close", avpCDNResultCodeAdminDisconnect)
return
}
}
}
func (ds *dynamicSession) handleEvent(ev string, args ...interface{}) {
if ev != "" {
level.Debug(ds.logger).Log(
"message", "fsm event",
"event", ev)
err := ds.fsm.handleEvent(ev, args...)
if err != nil {
level.Error(ds.logger).Log(
"message", "failed to handle fsm event",
"error", err)
ds.fsmActClose(nil)
}
}
}
// panics if expected arguments are not passed
func fsmArgsToV2Msg(args []interface{}) (msg *v2ControlMessage) {
if len(args) != 1 {
panic(fmt.Sprintf("unexpected argument count (wanted 1, got %v)", len(args)))
}
msg, ok := args[0].(*v2ControlMessage)
if !ok {
panic(fmt.Sprintf("first argument %T not *v2ControlMessage", args[0]))
}
return
}
// cdn args are optional, we set defaults here
func fsmArgsToCdnResult(args []interface{}) *resultCode {
rc := resultCode{
result: avpCDNResultCodeAdminDisconnect,
errCode: avpErrorCodeNoError,
}
for i := 0; i < len(args); i++ {
switch v := args[i].(type) {
case avpResultCode:
rc.result = v
case avpErrorCode:
rc.errCode = v
case string:
rc.errMsg = v
}
}
return &rc
}
func cdnResultCodeToString(rc *resultCode) string {
var resStr, errStr, errMsg string
switch rc.result {
case avpCDNResultCodeReserved:
resStr = "reserved"
case avpCDNResultCodeLostCarrier:
resStr = "lost carrier"
case avpCDNResultCodeGeneralError:
resStr = "general error"
case avpCDNResultCodeAdminDisconnect:
resStr = "admin disconnect"
case avpCDNResultCodeNoResources:
resStr = "temporary lack of resources"
case avpCDNResultCodeNotAvailable:
resStr = "permanent lack of resources"
case avpCDNResultCodeInvalidDestination:
resStr = "invalid destination"
case avpCDNResultCodeNoAnswer:
resStr = "not carrier detected"
case avpCDNResultCodeBusy:
resStr = "busy signal detected"
case avpCDNResultCodeNoDialTone:
resStr = "no dial tone"
case avpCDNResultCodeTimeout:
resStr = "establish timeout"
case avpCDNResultCodeBadTransport:
resStr = "no appropriate framing detected"
}
switch rc.errCode {
case avpErrorCodeNoError:
errStr = "no general error"
case avpErrorCodeNoControlConnection:
errStr = "no control connection exists yet"
case avpErrorCodeBadLength:
errStr = "length is wrong"
case avpErrorCodeBadValue:
errStr = "field out of range or reserved field was non-zero"
case avpErrorCodeNoResource:
errStr = "insufficient resources to handle this operation now"
case avpErrorCodeInvalidSessionID:
errStr = "session ID invalid in this context"
case avpErrorCodeVendorSpecificError:
errStr = "generic vendor-specific error"
case avpErrorCodeTryAnother:
errStr = "try another LNS"
case avpErrorCodeMBitShutdown:
errStr = "shut down due to unknown AVP with the M bit set"
}
if rc.errMsg != "" {
errMsg = rc.errMsg
} else {
errMsg = "unset"
}
return fmt.Sprintf("result %d (%s), error %d (%s), message '%s'",
rc.result, resStr,
rc.errCode, errStr,
errMsg)
}
func (ds *dynamicSession) handleMsg(msg controlMessage) {
switch msg.protocolVersion() {
case ProtocolVersion2:
msg, ok := msg.(*v2ControlMessage)
if !ok {
// This shouldn't occur, since the header protocol version
// dictates the message type during parsing. Bail out if
// it does since it indicates some dire coding error.
level.Error(ds.logger).Log(
"message", "couldn't cast L2TPv2 message as v2ControlMessage")
ds.fsmActClose(nil)
return
}
ds.handleV2Msg(msg)
return
}
level.Error(ds.logger).Log(
"message", "unhandled protocol version",
"version", msg.protocolVersion())
}
func (ds *dynamicSession) handleV2Msg(msg *v2ControlMessage) {
// It's possible to have a message mis-delivered on our control
// socket. Ignore these messages: ideally we'd redirect them
// but dropping them is a good compromise for now.
if msg.Sid() != uint16(ds.cfg.SessionID) {
level.Error(ds.logger).Log(
"message", "received control message with the wrong SID",
"expected", ds.cfg.SessionID,
"got", msg.Sid())
return
}
// Validate the message. If validation fails drive shutdown via.
// the FSM to allow the error to be communicated to the peer.
err := msg.validate()
if err != nil {
level.Error(ds.logger).Log(
"message", "bad control message",
"message_type", msg.getType(),
"error", err)
ds.handleEvent("close",
avpCDNResultCodeGeneralError,
avpErrorCodeBadValue,
fmt.Sprintf("bad %v message: %v", msg.getType(), err))
}
// Map the message to the appropriate event type. If we haven't got
// an event appropriate to the incoming message close the tunnel.
eventMap := []struct {
m avpMsgType
e string
}{
{avpMsgTypeIcrq, "icrq"},
{avpMsgTypeIcrp, "icrp"},
{avpMsgTypeIccn, "iccn"},
{avpMsgTypeCdn, "cdn"},
}
for _, em := range eventMap {
if msg.getType() == em.m {
ds.handleEvent(em.e, msg)
return
}
}
level.Error(ds.logger).Log(
"message", "unhandled v2 control message",
"message_type", msg.getType())
ds.handleEvent("close",
avpCDNResultCodeGeneralError,
avpErrorCodeBadValue,
fmt.Sprintf("unhandled v2 control message %v", msg.getType()))
}
func (ds *dynamicSession) sendMessage(msg controlMessage) {
err := ds.dt.sendMessage(msg)
if err != nil {
level.Error(ds.logger).Log(
"message", "failed to send control message",
"message_type", msg.getType(),
"error", err)
ds.fsmActClose(nil)
}
}
func (ds *dynamicSession) fsmActSendIcrq(args []interface{}) {
err := ds.sendIcrq()
if err != nil {
level.Error(ds.logger).Log(
"message", "failed to send ICRQ message",
"error", err)
ds.fsmActClose(nil)
}
}
func (ds *dynamicSession) sendIcrq() (err error) {
msg, err := newV2Icrq(ds.callSerial, ds.parent.getCfg().PeerTunnelID, ds.cfg)
if err != nil {
return err
}
ds.sendMessage(msg)
return
}
func (ds *dynamicSession) fsmActOnIcrp(args []interface{}) {
msg := fsmArgsToV2Msg(args)
psid, err := findUint16Avp(msg.getAvps(), vendorIDIetf, avpTypeSessionID)
if err != nil {
// Shouldn't occur since session ID is mandatory
level.Error(ds.logger).Log(
"message", "failed to parse peer session ID from ICRP",
"error", err)
ds.handleEvent("close",
avpCDNResultCodeGeneralError,
avpErrorCodeBadValue,
"no Assigned Session ID AVP in ICRP message")
return
}
ds.cfg.PeerSessionID = ControlConnID(psid)
err = ds.sendIccn()
if err != nil {
level.Error(ds.logger).Log(
"message", "failed to send ICCN",
"error", err)
// TODO: CDN args
ds.fsmActClose(nil)
return
}
level.Info(ds.logger).Log("message", "control plane established")
// establish the data plane
ds.dp, err = ds.parent.getDP().NewSession(
ds.parent.getCfg().TunnelID,
ds.parent.getCfg().PeerTunnelID,
ds.cfg)
if err != nil {
level.Error(ds.logger).Log(
"message", "failed to establish data plane",
"error", err)
// TODO: CDN args
ds.fsmActClose(nil)
return
}
ds.ifname, err = ds.dp.GetInterfaceName()
if err != nil {
level.Error(ds.logger).Log(
"message", "failed to retrieve session interface name",
"error", err)
// TODO: CDN args
ds.fsmActClose(nil)
}
level.Info(ds.logger).Log("message", "data plane established")
ds.established = true
ds.parent.handleUserEvent(&SessionUpEvent{
TunnelName: ds.parent.getName(),
Tunnel: ds.parent,
TunnelConfig: ds.parent.getCfg(),
SessionName: ds.getName(),
Session: ds,
SessionConfig: ds.cfg,
InterfaceName: ds.ifname,
})
}
func (ds *dynamicSession) sendIccn() (err error) {
msg, err := newV2Iccn(ds.parent.getCfg().PeerTunnelID, ds.cfg)
if err != nil {
return err
}
ds.sendMessage(msg)
return
}
func (ds *dynamicSession) fsmActSendCdn(args []interface{}) {
rc := fsmArgsToCdnResult(args)
if ds.result == "" {
ds.result = cdnResultCodeToString(rc)
}
_ = ds.sendCdn(rc)
ds.fsmActClose(args)
}
func (ds *dynamicSession) sendCdn(rc *resultCode) (err error) {
msg, err := newV2Cdn(ds.parent.getCfg().PeerTunnelID, rc, ds.cfg)
if err != nil {
return err
}
ds.sendMessage(msg)
return
}
func (ds *dynamicSession) fsmActOnCdn(args []interface{}) {
msg := fsmArgsToV2Msg(args)
rc, err := findResultCodeAvp(msg.getAvps(), vendorIDIetf, avpTypeResultCode)
if err == nil && ds.result == "" {
ds.result = cdnResultCodeToString(rc)
}
ds.fsmActClose(args)
}
func (ds *dynamicSession) fsmActClose(args []interface{}) {
if ds.dp != nil {
err := ds.dp.Down()
if err != nil {
level.Error(ds.logger).Log("message", "dataplane down failed", "error", err)
}
}
if ds.established {
ds.established = false
ds.parent.handleUserEvent(&SessionDownEvent{
TunnelName: ds.parent.getName(),
Tunnel: ds.parent,
TunnelConfig: ds.parent.getCfg(),
SessionName: ds.getName(),
Session: ds,
SessionConfig: ds.cfg,
InterfaceName: ds.ifname,
Result: ds.result,
})
}
ds.parent.unlinkSession(ds)
level.Info(ds.logger).Log("message", "close")
ds.isClosed = true
}
// Create a new client/LAC mode session instance
func newDynamicSession(serial uint32, name string, parent *dynamicTunnel, cfg *SessionConfig) (ds *dynamicSession, err error) {
ds = &dynamicSession{
baseSession: newBaseSession(
log.With(parent.getLogger(), "session_name", name),
name,
parent,
cfg),
callSerial: serial,
dt: parent,
msgRxChan: make(chan controlMessage),
eventChan: make(chan string),
closeChan: make(chan interface{}),
killChan: make(chan interface{}),
}
// Ref: RFC2661 section 7.4.1
ds.fsm = fsm{
current: "waittunnel",
table: []eventDesc{
{from: "waittunnel", events: []string{"tunnelopen"}, cb: ds.fsmActSendIcrq, to: "waitreply"},
{from: "waittunnel", events: []string{"close"}, cb: ds.fsmActClose, to: "dead"},
{from: "waitreply", events: []string{"icrp"}, cb: ds.fsmActOnIcrp, to: "established"},
{from: "waitreply", events: []string{"iccn"}, cb: ds.fsmActClose, to: "dead"},
{from: "waitreply", events: []string{"cdn"}, cb: ds.fsmActOnCdn, to: "dead"},
{from: "waitreply", events: []string{"icrq", "close"}, cb: ds.fsmActSendCdn, to: "dead"},
{from: "established", events: []string{"cdn"}, cb: ds.fsmActOnCdn, to: "dead"},
{
from: "established",
events: []string{
"icrq",
"icrp",
"iccn",
"close",
},
cb: ds.fsmActSendCdn,
to: "dead",
},
},
}
ds.wg.Add(1)
go ds.runSession()
return
}
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