sctp
Version:
SCTP network protocol (RFC4960) in plain Javascript
1,434 lines (1,331 loc) • 65.8 kB
JavaScript
const crypto = require('crypto')
const EventEmitter = require('events').EventEmitter
const debug = require('debug')
const ip = require('ip')
const Chunk = require('./chunk')
const defs = require('./defs')
const SN = require('./serial')
const Reassembly = require('./reassembly')
class Association extends EventEmitter {
constructor (endpoint, options) {
super()
this.state = 'CLOSED'
this.endpoint = endpoint
this.localPort = endpoint.localPort
this.remoteAddress = options.remoteAddress || undefined
this.remotePort = options.remotePort
this.my_tag = options.my_tag || crypto.randomBytes(4).readUInt32BE(0)
this.a_rwnd = options.a_rwnd || endpoint.a_rwnd || defs.NET_SCTP.RWND
this.OS = options.OS
this.MIS = options.MIS
this.debugger = {}
const label = `[${this.localPort}/${this.remoteAddress}:${this.remotePort}]`
this.debugger.warn = debug(`sctp:assoc:### ${label}`)
this.debugger.info = debug(`sctp:assoc:## ${label}`)
this.debugger.debug = debug(`sctp:assoc:# ${label}`)
this.debugger.trace = debug(`sctp:assoc: ${label}`)
this.debugger.debug('create association')
// TODO provide also good way to iterate
const key = this.remoteAddress + ':' + this.remotePort
endpoint.associations_lookup[key] = this
endpoint.associations.push(this)
this.reassembly = new Reassembly({
rwnd: this.a_rwnd
})
this.reassembly.on('data', (buffer, stream, ppid) => {
this._deliver(buffer, stream, ppid)
})
this.rto_initial = defs.NET_SCTP.rto_initial
this.rto_min = defs.NET_SCTP.rto_min
this.rto_max = defs.NET_SCTP.rto_max
const PMTU = defs.NET_SCTP.PMTU || 1500 // TODO
this.peer_rwnd = 0
// TODO: for each remote address if multi-homing
this.sack_timeout = defs.NET_SCTP.sack_timeout
this.sack_freq = defs.NET_SCTP.sack_freq
this.hb_interval = defs.NET_SCTP.hb_interval
this.flightsize = 0
// 13.3. Per Transport Address Data
this.default_address_data = {
active: false,
errors: 0,
error_threshold: 10,
cwnd: Math.min(4 * PMTU, Math.max(2 * PMTU, 4380)), // 7.2.1. Slow-Start
RTO: this.rto_initial,
SRTT: 0,
RTTVAR: 0,
PMTU,
rtoPending: false // RTO-Pending
}
Object.assign(this, this.default_address_data) // TODO
this.destinations = {}
if (this.remoteAddress) {
this.destinations[this.remoteAddress] = this.default_address_data
}
this.my_next_tsn = new SN(this.my_tag)
this.HTNA = this.my_next_tsn.copy()
this.bundling = 0
this.sacks = 0
this.ssn = []
this.fastRecovery = false
this.readBuffer = []
this.everSentSack = false
this.packetsSinceLastSack = 0
this.queue = []
this.sent = {}
this.countRcv = 0
this.nonces = {}
this.mute = false // If received ABORT chunk
this.drainCallback = null
this.on('data', this.onData.bind(this))
this.on('sack', this.onSack.bind(this))
this.on('init', this.onInit.bind(this))
this.on('init_ack', this.onInitAck.bind(this))
this.on('heartbeat', this.onHeartbeat.bind(this))
this.on('heartbeat_ack', this.onHeartbeatAck.bind(this))
this.on('cookie_echo', this.onCookieEcho.bind(this))
this.on('cookie_ack', this.onCookieAck.bind(this))
this.on('shutdown', this.onShutdown.bind(this))
this.on('shutdown_ack', this.onShutdownAck.bind(this))
this.on('shutdown_complete', this.onShutdownComplete.bind(this))
this.on('error', this.onError.bind(this))
this.on('abort', this.onAbort.bind(this))
this.on('icmp', this.onICMP.bind(this))
}
acceptRemote (chunk) {
if (!chunk) {
throw new Error('peer init chunk not provided')
}
this.debugger.debug('accept remote association with chunk %O', chunk)
this._updatePeer(chunk)
/*
TODO
A COOKIE ACK MAY be sent to an UNCONFIRMED address,
but it MUST be bundled with a HEARTBEAT including a nonce.
An implementation that does NOT support bundling
MUST NOT send a COOKIE ACK to an UNCONFIRMED address.
2) For the receiver of the COOKIE ECHO,
the only CONFIRMED address is the one to which the INIT-ACK was sent.
*/
this._up()
this._sendChunk('cookie_ack', {})
}
onInit (chunk, src, header) {
this.debugger.warn('rfc4960 "5.2.2. Unexpected INIT ...', this.state, chunk, src, header)
// TODO restart association
/*
Before responding, the endpoint MUST check to see if the
unexpected INIT adds new addresses to the association. If new
addresses are added to the association, the endpoint MUST respond
with an ABORT, copying the 'Initiate Tag' of the unexpected INIT into
the 'Verification Tag' of the outbound packet carrying the ABORT. In
the ABORT response, the cause of error MAY be set to 'restart of an
association with new addresses'. The error SHOULD list the addresses
that were added to the restarting association.
*/
if (chunk.ipv4_address) {
// TODO check if addresses are really new. now is a placeholder
let abort = new Chunk('abort', {})
// we MUST copy initiate_tag, so use low-level endpoint function to send packet
this.endpoint._sendPacket(
src,
this.remotePort,
chunk.initiate_tag,
[abort.toBuffer()],
() => {
this.debugger.info('responded with an ABORT')
}
)
}
}
onCookieEcho (chunk, src, header) {
this.debugger.warn(
'Handle a COOKIE ECHO when a TCB Exists',
this.state,
chunk
)
const cookieData = this.endpoint.validateCookie(chunk.cookie, header)
let initChunk
if (cookieData) {
this.debugger.trace('cookie is valid %O', cookieData)
initChunk = Chunk.fromBuffer(cookieData.initChunk)
}
this.debugger.debug('association my_tag %d peer_tag %d, cookie my_tag %d peer_tag %d',
this.my_tag, this.peer_tag, cookieData.my_tag, initChunk.initiate_tag)
let action = ''
if (this.my_tag === cookieData.my_tag) {
// B or D
if (this.peer_tag === initChunk.initiate_tag) {
action = 'D'
} else {
action = 'B'
}
} else if (this.peer_tag === initChunk.initiate_tag) {
// TODO tmp, implement tie-tags
const tieTagsUnknown = true
if (tieTagsUnknown) {
action = 'C'
}
} else {
// TODO tmp, implement tie-tags
const tieTagsMatch = true
if (tieTagsMatch) {
action = 'A'
}
}
this.debugger.warn('COOKIE ECHO action', action)
switch (action) {
case 'A':
/*
TODO tie-tags
TODO SHUTDOWN-ACK-SENT state
A) In this case, the peer may have restarted. When the endpoint
recognizes this potential 'restart', the existing session is
treated the same as if it received an ABORT followed by a new
COOKIE ECHO with the following exceptions:
- Any SCTP DATA chunks MAY be retained (this is an
implementation-specific option).
- A notification of RESTART SHOULD be sent to the ULP instead of
a "COMMUNICATION LOST" notification.
All the congestion control parameters (e.g., cwnd, ssthresh)
related to this peer MUST be reset to their initial values (see
Section 6.2.1).
After this, the endpoint shall enter the ESTABLISHED state.
If the endpoint is in the SHUTDOWN-ACK-SENT state and recognizes
that the peer has restarted (Action A), it MUST NOT set up a new
association but instead resend the SHUTDOWN ACK and send an ERROR
chunk with a "Cookie Received While Shutting Down" error cause to
its peer.
*/
if (this.state === 'SHUTDOWN-ACK-SENT') {
this._sendChunk('shutdown_ack', {}, src, () => {
this.debugger.info('sent shutdown_ack')
})
return
}
// TODO
this.debugger.warn('association restart is not implemented and was not tested!')
this.emit('RESTART')
break
case 'B':
/*
TODO init collision
B) In this case, both sides may be attempting to start an association
at about the same time, but the peer endpoint started its INIT
after responding to the local endpoint's INIT. Thus, it may have
picked a new Verification Tag, not being aware of the previous tag
it had sent this endpoint. The endpoint should stay in or enter
the ESTABLISHED state, but it MUST update its peer's Verification
Tag from the State Cookie, stop any init or cookie timers that may
be running, and send a COOKIE ACK.
*/
this.peer_tag = initChunk.initiate_tag
// TODO stop init & cookie timers
this._sendChunk('cookie_ack')
break
case 'C':
/*
C) In this case, the local endpoint's cookie has arrived late.
Before it arrived, the local endpoint sent an INIT and received an
INIT ACK and finally sent a COOKIE ECHO with the peer's same tag
but a new tag of its own. The cookie should be silently
discarded. The endpoint SHOULD NOT change states and should leave
any timers running.
*/
break
case 'D':
/*
D) When both local and remote tags match, the endpoint should enter
the ESTABLISHED state, if it is in the COOKIE-ECHOED state. It
should stop any cookie timer that may be running and send a COOKIE ACK.
*/
if (this.state === 'COOKIE-ECHOED') {
this.state = 'ESTABLISHED'
}
// TODO should be already running, state also be ESTABLISHED
// this._enableHeartbeat()
// TODO stop cookie timer
this.debugger.warn('COOKIE ECHO send cookie_ack')
this._sendChunk('cookie_ack')
break
default:
/*
Note: For any case not shown in Table 2,
the cookie should be silently discarded
*/
}
}
onICMP (packet, code) {
/*
An implementation MAY ignore any ICMPv4 messages where the code
does not indicate "Protocol Unreachable" or "Fragmentation Needed".
*/
this.debugger.warn('< received ICMP code %d', code)
if (packet.v_tag && packet.v_tag !== this.peer_tag) {
return
}
if (code === 4) {
if (packet.v_tag === 0 && packet.chunks.length === 1) {
const chunk = packet.chunks[0]
if (chunk.chunkType === 'init' && chunk.initiate_tag === this.my_tag) {
this.debugger.warn('< ICMP fragmentation needed')
// TODO process this information as defined for PATH MTU discovery
}
}
} else {
this.debugger.warn('< ICMP signals that peer unreachable')
this.emit('COMMUNICATION LOST')
this._destroy()
}
}
onData (chunk, source) {
this.countRcv++
this.debugger.debug('< DATA %d, total: %d', chunk.tsn, this.countRcv)
if (!(this.state === 'ESTABLISHED' ||
this.state === 'SHUTDOWN-PENDING' ||
this.state === 'SHUTDOWN-SENT'
)) {
return
}
if (!chunk.user_data || !chunk.user_data.length > 0) {
this.debugger.warn('< received empty DATA chunk %o', chunk)
this._abort({ error_causes: [{ cause: 'NO_USER_DATA', tsn: chunk.tsn }] }, source)
return
}
const dataAccepted = this.reassembly.process(chunk)
if (this.state === 'SHUTDOWN-SENT') {
/*
While in the SHUTDOWN-SENT state, the SHUTDOWN sender MUST
immediately respond to each received packet containing one or more
DATA chunks with a SHUTDOWN chunk and restart the T2-shutdown timer.
If a SHUTDOWN chunk by itself cannot acknowledge all of the received
DATA chunks (i.e., there are TSNs that can be acknowledged that are
larger than the cumulative TSN, and thus gaps exist in the TSN
sequence), or if duplicate TSNs have been received, then a SACK chunk
MUST also be sent.
*/
this.debugger.trace('we are in the SHUTDOWN-SENT state - repeat SHUTDOWN')
this._sendChunk('shutdown', { c_tsn_ack: this.reassembly.peer_c_tsn.number })
if (!this.reassembly.have_gaps && this.duplicates.length === 0) {
return
}
}
/*
The guidelines on delayed acknowledgement algorithm specified in
Section 4.2 of [RFC2581] SHOULD be followed. Specifically, an
acknowledgement SHOULD be generated for at least every second packet
(not every second DATA chunk) received, and SHOULD be generated
within 200 ms of the arrival of any unacknowledged DATA chunk. In
some situations, it may be beneficial for an SCTP transmitter to be
more conservative than the algorithms detailed in this document
allow. However, an SCTP transmitter MUST NOT be more aggressive than
the following algorithms allow.
*/
if (!chunk.last_in_packet) {
/*
An SCTP receiver MUST NOT generate more than one SACK for every
incoming packet, other than to update the offered window as the
receiving application consumes new data.
*/
// TODO sacks on data consumption?
return
}
let immediately = false
if (dataAccepted) {
if (++this.packetsSinceLastSack >= this.sack_freq) {
immediately = true
}
}
if (!this.everSentSack) {
/*
After the reception of the first DATA chunk in an association the
endpoint MUST immediately respond with a SACK to acknowledge the DATA
chunk. Subsequent acknowledgements should be done as described in
Section 6.2.
*/
immediately = true
}
if (this.reassembly.have_gaps) {
/*
If the endpoint detects a gap in the received DATA chunk sequence,
it SHOULD send a SACK with Gap Ack Blocks immediately.
*/
immediately = true
}
if (this.reassembly.duplicates.length > 0) {
/*
When a packet arrives with duplicate DATA chunk(s) and with no new
DATA chunk(s), the endpoint MUST immediately send a SACK with no delay.
*/
immediately = true
}
if (!dataAccepted) {
/*
In either case, if such a DATA chunk is dropped, the
receiver MUST immediately send back a SACK with the current receive
window showing only DATA chunks received and accepted so far.
*/
immediately = true
}
if (immediately) {
// For all such we do sack immediately
this.debugger.trace('SACK immediately')
// Serves to group sack sending for chunks in packet
this.sacks++
this._sack()
} else {
this.scheduleSack()
}
}
scheduleSack () {
if (this._sack_timer) {
this.debugger.trace('SACK timer already set')
} else {
this.debugger.trace('SACK timer set', this.sack_timeout)
this._sack_timer = setTimeout(() => {
this.debugger.trace('SACK timer expired', this.sack_timeout)
this._sack()
}, this.sack_timeout)
}
}
onSack (chunk) {
this.debugger.trace('< sack c_tsn %d, peer_rwnd %d', chunk.c_tsn_ack, chunk.a_rwnd)
/*
A SACK MUST be processed in ESTABLISHED, SHUTDOWN-PENDING, and
SHUTDOWN-RECEIVED. An incoming SACK MAY be processed in COOKIE-
ECHOED. A SACK in the CLOSED state is out of the blue and SHOULD be
processed according to the rules in Section 8.4. A SACK chunk
received in any other state SHOULD be discarded.
*/
if (
!(
this.state === 'ESTABLISHED' ||
this.state === 'SHUTDOWN-PENDING' ||
this.state === 'SHUTDOWN-RECEIVED' ||
this.state === 'COOKIE-ECHOED'
)
) {
return
}
// TODO 'PROTOCOL_VIOLATION' The cumulative tsn ack beyond the max tsn currently sent
// This.debugger.warn('< sack %O', chunk)
this.peer_rwnd = chunk.a_rwnd
const cTSN = new SN(chunk.c_tsn_ack)
const ackAdvanced = this.c_tsn_ack ? cTSN.gt(this.c_tsn_ack) : true
this.c_tsn_ack = cTSN.copy()
if (this.fastRecovery && cTSN.ge(this.fastRecoveryExitPoint)) {
this.fastRecovery = false
this.fastRecoveryExitPoint = null
}
const flightsize = this.flightsize
for (const tsn in this.sent) {
const TSN = new SN(tsn)
if (TSN.le(this.c_tsn_ack)) {
// this.debugger.trace('acknowledge tsn %d, flightsize %d', tsn, flightsize)
this._acknowledge(TSN)
}
}
if (this.drainCallback && this.drain()) {
this.debugger.debug('drain callback c_tsn %d, peer_rwnd %d', chunk.c_tsn_ack, chunk.peer_rwnd)
this.drainCallback()
delete this.drainCallback
}
if (
chunk.sack_info &&
chunk.sack_info.gap_blocks &&
chunk.sack_info.gap_blocks.length > 0
) {
const gapBlocks = chunk.sack_info.gap_blocks
this.debugger.trace('< gap blocks ', chunk.c_tsn_ack, gapBlocks)
/*
Whenever an endpoint receives a SACK that indicates that some TSNs
are missing, it SHOULD wait for two further miss indications (via
subsequent SACKs for a total of three missing reports) on the same
TSNs before taking action with regard to Fast Retransmit.
*/
const absent = []
gapBlocks.forEach((block, idx) => {
// TODO rewrite with SN api
absent.push({
start: new SN(idx ? chunk.c_tsn_ack + gapBlocks[idx - 1].finish + 1 : chunk.c_tsn_ack + 1),
finish: new SN(chunk.c_tsn_ack + block.start - 1)
})
for (
let t = this.c_tsn_ack.copy().inc(block.start);
t.le(this.c_tsn_ack.copy().inc(block.finish));
t.inc(1)
) {
if (this.sent[t.getNumber()]) {
this._acknowledge(t)
}
}
})
// 7.2.4. Fast Retransmit on Gap Reports
/*
Whenever an endpoint receives a SACK that indicates that some TSNs
are missing, it SHOULD wait for two further miss indications (via
subsequent SACKs for a total of three missing reports) on the same
TSNs before taking action with regard to Fast Retransmit.
*/
let doFastRetransmit = false
absent.forEach(block => {
for (let TSN = block.start.copy(); TSN.le(block.finish); TSN.inc(1)) {
const tsn = TSN.getNumber()
if (this.sent[tsn]) {
/*
Miss indications SHOULD follow the HTNA (Highest TSN Newly
Acknowledged) algorithm. For each incoming SACK, miss indications
are incremented only for missing TSNs prior to the highest TSN newly
acknowledged in the SACK. A newly acknowledged DATA chunk is one not
previously acknowledged in a SACK. If an endpoint is in Fast
Recovery and a SACK arrives that advances the Cumulative TSN Ack
Point, the miss indications are incremented for all TSNs reported
missing in the SACK.
*/
this.debugger.trace(
'fast retransmit %d ? HTNA %d, fast recovery %s, ack advanced %s',
tsn,
this.HTNA.number,
this.fastRecovery,
ackAdvanced
)
if (TSN.lt(this.HTNA) || (this.fastRecovery && ackAdvanced)) {
this.sent[tsn].losses++
this.debugger.trace(
'increase miss indications for %d to %d',
tsn,
this.sent[tsn].losses
)
if (this.sent[tsn].losses >= 3) {
/*
Mark the DATA chunk(s) with three miss indications for
retransmission.
A straightforward implementation of the above keeps a counter for
each TSN hole reported by a SACK. The counter increments for each
consecutive SACK reporting the TSN hole. After reaching 3 and
starting the Fast-Retransmit procedure, the counter resets to 0.
*/
this.sent[tsn].losses = 0
this.sent[tsn].fastRetransmit = true
doFastRetransmit = true
}
}
}
}
})
if (doFastRetransmit) {
this._fastRetransmit()
}
/*
Whenever a SACK is received missing a TSN that was previously
acknowledged via a Gap Ack Block, start the T3-rtx for the
destination address to which the DATA chunk was originally
transmitted if it is not already running.
*/
} else if (this.my_next_tsn.eq(this.c_tsn_ack.copy().inc(1))) {
/*
Whenever all outstanding data sent to an address have been
acknowledged, turn off the T3-rtx timer of that address.
*/
this.flightsize = 0
this.debugger.trace('all outstanding data has been acknowledged')
this._stopT3()
if (this.state === 'SHUTDOWN-PENDING') {
this._shutdown()
return
}
}
if (chunk.sack_info && chunk.sack_info.duplicate_tsn &&
chunk.sack_info.duplicate_tsn.length > 0) {
this.debugger.trace('peer indicates duplicates %o', chunk.sack_info.duplicate_tsn)
}
if (ackAdvanced && this.flightsize) {
/*
When cwnd is less than or equal to ssthresh, an SCTP endpoint MUST
use the slow-start algorithm to increase cwnd only if the current
congestion window is being fully utilized, an incoming SACK
advances the Cumulative TSN Ack Point, and the data sender is not
in Fast Recovery. Only when these three conditions are met can
the cwnd be increased; otherwise, the cwnd MUST not be increased.
If these conditions are met, then cwnd MUST be increased by, at
most, the lesser of 1) the total size of the previously
outstanding DATA chunk(s) acknowledged, and 2) the destination's
path MTU. This upper bound protects against the ACK-Splitting
attack outlined in [SAVAGE99].
*/
// TODO: rule to increase cwnd is unclear to me
if (this.cwnd <= this.ssthresh && this.cwnd <= this.flightsize && !this.fastRecovery) {
const totalAcknowledgedSize = flightsize - this.flightsize
const cwndIncrease = Math.min(totalAcknowledgedSize, this.PMTU)
const previousCwnd = this.cwnd
this.cwnd += cwndIncrease
this.debugger.debug('increase cwnd +%d from %d to %d, ssthresh %d',
cwndIncrease, previousCwnd, this.cwnd, this.ssthresh)
}
/*
Whenever a SACK is received that acknowledges the DATA chunk
with the earliest outstanding TSN for that address, restart the
T3-rtx timer for that address with its current RTO (if there is
still outstanding data on that address).
*/
this.debugger.trace('c_tsn_ack advanced to %d', this.c_tsn_ack.number)
this._restartT3()
}
if (this.flightsize > 0 && this.flightsize < this.cwnd) {
this.debugger.trace('flightsize %d < cwnd %d', this.flightsize, this.cwnd)
this._retransmit()
}
}
onInitAck (chunk, source) {
if (this.state === 'COOKIE-WAIT') {
this.debugger.debug('< init_ack cookie', chunk.state_cookie)
clearTimeout(this.T1)
if (chunk.inbound_streams === 0) {
// Receiver of an INIT ACK with the MIS value set to 0
// SHOULD destroy the association discarding its TCB
this._abort({ error_causes: [{ cause: 'INVALID_MANDATORY_PARAMETER' }] }, source)
return
}
this._updatePeer(chunk)
this._sendChunk('cookie_echo', { cookie: chunk.state_cookie }, source, () => {
this.debugger.debug('sent cookie_echo', chunk.state_cookie)
})
/*
If the receiver of an INIT ACK chunk detects unrecognized parameters
and has to report them according to Section 3.2.1, it SHOULD bundle
the ERROR chunk containing the 'Unrecognized Parameters' error cause
with the COOKIE ECHO chunk sent in response to the INIT ACK chunk.
If the receiver of the INIT ACK cannot bundle the COOKIE ECHO chunk
with the ERROR chunk, the ERROR chunk MAY be sent separately but not
before the COOKIE ACK has been received.
Note: Any time a COOKIE ECHO is sent in a packet, it MUST be the
first chunk.
*/
if (chunk.errors) {
this.ERROR([{
cause: 'UNRECONGNIZED_PARAMETERS',
unrecognized_parameters: Buffer.concat(chunk.errors)
}], source)
}
this.state = 'COOKIE-ECHOED'
} else {
/*
5.2.3. Unexpected INIT ACK
If an INIT ACK is received by an endpoint in any state other than the
COOKIE-WAIT state, the endpoint should discard the INIT ACK chunk.
An unexpected INIT ACK usually indicates the processing of an old or
duplicated INIT chunk.
*/
this.debugger.warn('Unexpected INIT ACK')
}
}
ERROR (errors, dst) {
this._sendChunk('error', {
error_causes: errors
}, dst)
}
onHeartbeat (chunk, source) {
/*
A receiver of a HEARTBEAT MUST respond to a
HEARTBEAT with a HEARTBEAT-ACK after entering the COOKIE-ECHOED state
(INIT sender) or the ESTABLISHED state (INIT receiver), up until
reaching the SHUTDOWN-SENT state (SHUTDOWN sender) or the SHUTDOWN-
ACK-SENT state (SHUTDOWN receiver). TODO
*/
this.debugger.trace(
'< HEARTBEAT',
chunk.heartbeat_info.length,
chunk.heartbeat_info
)
this._sendChunk(
'heartbeat_ack',
{ heartbeat_info: chunk.heartbeat_info },
source
)
}
onHeartbeatAck (chunk) {
this.debugger.trace(
'< HEARTBEAT ACK',
chunk.heartbeat_info.length,
chunk.heartbeat_info
)
/*
Upon receipt of the HEARTBEAT ACK, a verification is made that the
nonce included in the HEARTBEAT parameter is the one sent to the
address indicated inside the HEARTBEAT parameter. When this match
occurs, the address that the original HEARTBEAT was sent to is now
considered CONFIRMED and available for normal data transfer.
*/
const nonce = chunk.heartbeat_info.readUInt32BE(0)
if (this.nonces[nonce]) {
const address = ip.toString(chunk.heartbeat_info, 8, 4)
this.debugger.trace('address confirmed alive', address)
}
delete this.nonces[nonce]
}
onCookieAck () {
this.debugger.debug('< COOKIE ACK in state %s', this.state)
if (this.state === 'COOKIE-ECHOED') {
this._up()
}
}
onShutdown (chunk, source) {
// TODO: 9.2. Shutdown of an Association
if (this.state === 'SHUTDOWN-RECEIVED') {
/*
Once an endpoint has reached the SHUTDOWN-RECEIVED state, it MUST NOT
send a SHUTDOWN in response to a ULP request, and should discard
subsequent SHUTDOWN chunks.
*/
return
}
this.debugger.info('< SHUTDOWN')
// TODO check c_tsn_ack
/*
cause: 'PROTOCOL_VIOLATION',
additional_information:
'The cumulative tsn ack beyond the max tsn currently sent:...'
verify, by checking the Cumulative TSN Ack field of the chunk,
that all its outstanding DATA chunks have been received by the
SHUTDOWN sender.
If there are still outstanding DATA chunks left, the SHUTDOWN
receiver MUST continue to follow normal data transmission procedures
defined in Section 6, until all outstanding DATA chunks are
acknowledged; however, the SHUTDOWN receiver MUST NOT accept new data
from its SCTP user.
*/
if (this.state === 'SHUTDOWN-SENT') {
/*
If an endpoint is in the SHUTDOWN-SENT state and receives a SHUTDOWN
chunk from its peer, the endpoint shall respond immediately with a
SHUTDOWN ACK to its peer, and move into the SHUTDOWN-ACK-SENT state
restarting its T2-shutdown timer.
*/
this._sendChunk('shutdown_ack', {}, source, () => {
this.debugger.info('sent shutdown_ack')
})
this._restartT2()
return
}
this.state = 'SHUTDOWN-RECEIVED'
if (this.flightsize === 0) {
this._sendChunk('shutdown_ack', {}, source, () => {
this.state = 'SHUTDOWN-ACK-SENT'
this.debugger.info('sent shutdown_ack')
})
this._startT2()
}
}
onShutdownAck (chunk, source) {
/*
Upon the receipt of the SHUTDOWN ACK, the SHUTDOWN sender shall stop
the T2-shutdown timer, send a SHUTDOWN COMPLETE chunk to its peer,
and remove all record of the association.
*/
this.debugger.info('< SHUTDOWN ACK in state %s', this.state)
if (this.state === 'SHUTDOWN-SENT' || this.state === 'SHUTDOWN-ACK-SENT') {
this._down()
this.state = 'CLOSED'
this.debugger.info('> sending SHUTDOWN COMPLETE')
this._sendChunk('shutdown_complete', {}, source, () => {
this.debugger.trace('sent SHUTDOWN COMPLETE')
this.emit('SHUTDOWN COMPLETE')
this._destroy()
})
}
}
onShutdownComplete () {
/*
- The receiver of a SHUTDOWN COMPLETE shall accept the packet if
the Verification Tag field of the packet matches its own tag and
the T bit is not set OR if it is set to its peer's tag and the T
bit is set in the Chunk Flags. Otherwise, the receiver MUST
silently discard the packet and take no further action. An
endpoint MUST ignore the SHUTDOWN COMPLETE if it is not in the
SHUTDOWN-ACK-SENT state.
Upon reception of the SHUTDOWN COMPLETE chunk, the endpoint will
verify that it is in the SHUTDOWN-ACK-SENT state; if it is not, the
chunk should be discarded. If the endpoint is in the SHUTDOWN-ACK-
SENT state, the endpoint should stop the T2-shutdown timer and remove
all knowledge of the association (and thus the association enters the
CLOSED state).
*/
if (this.state === 'SHUTDOWN-ACK-SENT') {
this._down()
this.debugger.info('< SHUTDOWN COMPLETE')
this.emit('SHUTDOWN COMPLETE')
this._destroy()
}
}
onError (chunk) {
this.debugger.warn('< ERROR', chunk)
if (
chunk.error_causes.some(
item => item.cause === 'STALE_COOKIE_ERROR'
)
) {
// TODO: 5.2.6. Handle Stale COOKIE Error
}
this.emit('COMMUNICATION ERROR', chunk.error_causes)
}
onAbort (chunk) {
this.debugger.info('< ABORT, connection closed')
if (chunk.error_causes) {
this.debugger.warn('< ABORT has error causes', chunk.error_causes)
}
this._down()
if (this.queue.length > 0) {
this.debugger.trace('abandon sending of chunks', this.queue.length)
}
this.queue = []
this.emit('COMMUNICATION LOST', 'abort', chunk.error_causes)
this._destroy()
}
init () {
const initParams = {
initiate_tag: this.my_tag,
a_rwnd: this.a_rwnd,
outbound_streams: this.OS,
inbound_streams: this.MIS,
initial_tsn: this.my_next_tsn.number
}
if (this.endpoint.localAddress) {
initParams.ipv4_address = this.endpoint.localAddress
}
this.debugger.info('INIT params', initParams)
let counter = 0
this.RTI = this.rto_initial
const init = () => {
if (counter >= defs.NET_SCTP.max_init_retransmits) {
// Fail
} else {
if (counter) {
// Not from RFC, but from lk-sctp
this.RTI *= 2
if (this.RTI > this.rto_max) {
this.RTI = this.rto_max
}
}
this._sendChunk('init', initParams)
counter++
this.T1 = setTimeout(init, this.RTO)
}
}
init()
this.state = 'COOKIE-WAIT'
}
_sendChunk (chunkType, options, destination, callback) {
const chunk = new Chunk(chunkType, options)
this.debugger.debug('> send chunk', chunkType)
this.debugger.trace('> %O', chunk)
/*
By default, an endpoint SHOULD always transmit to the primary path,
unless the SCTP user explicitly specifies the destination transport
address (and possibly source transport address) to use.
An endpoint SHOULD transmit reply chunks (e.g., SACK, HEARTBEAT ACK,
etc.) to the same destination transport address from which it
received the DATA or control chunk to which it is replying. This
rule should also be followed if the endpoint is bundling DATA chunks
together with the reply chunk.
However, when acknowledging multiple DATA chunks received in packets
from different source addresses in a single SACK, the SACK chunk may
be transmitted to one of the destination transport addresses from
which the DATA or control chunks being acknowledged were received.
*/
if (
chunkType === 'data' ||
chunkType === 'sack' ||
chunkType === 'heartbeat_ack'
) {
// RFC allows to bundle other control chunks,
// but this gives almost no benefits
this.debugger.trace('> bundle-send', chunkType, options)
chunk.callback = callback
if (chunkType === 'data') {
// Do not encode here because we'll add tsn later, during bundling
chunk.size = chunk.user_data.length + 16
} else {
chunk.buffer = chunk.toBuffer()
chunk.size = chunk.buffer.length
}
this.debugger.trace('chunk size', chunk.size)
this.queue.push(chunk)
this.bundling++
setTimeout(() => {
this._bundle()
})
} else {
// No bundle
// setTimeout(() => {
// use nextTick to be in order with bundled chunks
const buffer = chunk.toBuffer()
this.debugger.trace('> no-bundle send', chunkType)
this._sendPacket([buffer], destination, [callback])
// }, 0)
}
}
_sack () {
if (this._sack_timer) {
this.debugger.trace('cancel SACK timer and do it now')
clearTimeout(this._sack_timer)
delete this._sack_timer
}
this.sacks--
if (this.sacks > 0) {
// Wait for last sack request in idle cycle
this.debugger.trace('grouping SACKs, wait %d more...', this.sacks)
return
}
const sackOptions = this.reassembly.sackInfo()
this.debugger.trace('prepared SACK %O', sackOptions)
this._sendChunk('sack', sackOptions)
this.everSentSack = true
this.packetsSinceLastSack = 0
}
_acknowledge (TSN) {
// this.debugger.trace('acknowledge tsn %d, peer_rwnd %d, flightsize %d', TSN.number, this.peer_rwnd, this.flightsize)
this.flightsize -= this.sent[TSN.getNumber()].size
this.debugger.trace('acknowledge tsn %d, peer_rwnd %d, flightsize %d', TSN.number, this.peer_rwnd, this.flightsize)
if (!this.HTNA || TSN.gt(this.HTNA)) {
this.HTNA = TSN.copy()
}
delete this.sent[TSN.getNumber()]
// RTO calculation
if (this.rtoPending && this.rtoPending.tsn.eq(TSN)) {
this._updateRTO(new Date() - this.rtoPending.sent)
this.rtoPending = false
}
}
_updateRTO (R) {
if (this.SRTT) {
const alpha = 1 / defs.NET_SCTP.rto_alpha_exp_divisor
const beta = 1 / defs.NET_SCTP.rto_beta_exp_divisor
this.RTTVAR = (1 - beta) * this.RTTVAR + beta * Math.abs(this.SRTT - R)
this.RTTVAR = Math.max(this.RTTVAR, defs.NET_SCTP.G)
this.SRTT = (1 - alpha) * this.SRTT + alpha * R
this.RTO = this.SRTT + 4 * this.RTTVAR
} else {
this.SRTT = R
this.RTTVAR = R / 2
this.RTTVAR = Math.max(this.RTTVAR, defs.NET_SCTP.G)
this.RTO = this.SRTT + 4 * this.RTTVAR
}
if (this.RTO < this.rto_min) {
this.RTO = this.rto_min
}
if (this.RTO > this.rto_max) {
this.RTO = this.rto_max
}
this.debugger.trace('new RTO %d', this.RTO)
}
_startT2 () {
if (this.T2) {
this.debugger.trace('T2-shutdown timer is already running')
return
}
this.debugger.trace('start T3-shutdown timer (RTO %d)', this.RTO)
this.T2 = setTimeout(this._expireT2.bind(this), this.RTO)
}
_stopT2 () {
if (this.T2) {
this.debugger.trace('stop T2-shutdown timer')
clearTimeout(this.T2)
this.T2 = null
}
}
_restartT2 () {
this.debugger.trace('restart T2-shutdown timer')
this._stopT2()
this._startT2()
}
_expireT2 () {
if (this.state === 'SHUTDOWN-SENT') {
// TODO source
this._sendChunk('shutdown', {}, null, () => {
this.debugger.info('resent shutdown')
})
} else if (this.state === 'SHUTDOWN-ACK-SENT') {
// TODO source
this._sendChunk('shutdown_ack', {}, null, () => {
this.debugger.info('resent shutdown ack')
})
}
}
_startT3 () {
if (this.T3) {
this.debugger.trace('T3-rtx timer is already running')
return
}
this.debugger.trace('start T3-rtx timer (RTO %d)', this.RTO)
this.T3 = setTimeout(this._expireT3.bind(this), this.RTO)
}
_stopT3 () {
if (this.T3) {
this.debugger.trace('stop T3-rtx timer')
clearTimeout(this.T3)
this.T3 = null
}
}
_restartT3 () {
this.debugger.trace('restart T3-rtx timer')
this._stopT3()
this._startT3()
}
_expireT3 () {
this.T3 = null
this.debugger.trace('T3-rtx timer has expired')
if (Object.keys(this.sent).length === 0) {
this.debugger.warn('bug: there are no chunks in flight')
return
}
/*
6.3.3. Handle T3-rtx Expiration
Whenever the retransmission timer T3-rtx expires for a destination
address, do the following:
E1) For the destination address for which the timer expires, adjust
its ssthresh with rules defined in Section 7.2.3 and set the
cwnd <- MTU.
When the T3-rtx timer expires on an address, SCTP should perform slow
start by:
ssthresh = max(cwnd/2, 4*MTU)
cwnd = 1*MTU
and ensure that no more than one SCTP packet will be in flight for
that address until the endpoint receives acknowledgement for
successful delivery of data to that address.
*/
this.ssthresh = Math.max(this.cwnd / 2, 4 * this.PMTU)
this.cwnd = this.PMTU
/*
E2) For the destination address for which the timer expires, set RTO
<- RTO * 2 ("back off the timer"). The maximum value discussed
in rule C7 above (RTO.max) may be used to provide an upper bound
to this doubling operation.
*/
if (this.RTO < this.rto_max) {
this.RTO *= 2
if (this.RTO > this.rto_max) {
this.RTO = this.rto_max
}
}
this.debugger.trace(
'adjustments on expire: cwnd %d / ssthresh %d / RTO %d',
this.cwnd,
this.ssthresh,
this.RTO
)
/*
E3) Determine how many of the earliest (i.e., lowest TSN)
outstanding DATA chunks for the address for which the T3-rtx has
expired will fit into a single packet, subject to the MTU
constraint for the path corresponding to the destination
transport address to which the retransmission is being sent
(this may be different from the address for which the timer
expires; see Section 6.4). Call this value K. Bundle and
retransmit those K DATA chunks in a single packet to the
destination endpoint.
*/
let bundledLength = 20
let bundledCount = 0
const tsns = []
for (const tsn in this.sent) {
const chunk = this.sent[tsn]
this.debugger.trace('retransmit tsn %d', chunk.tsn)
if (bundledLength + chunk.user_data.length + 16 > this.PMTU) {
/*
Note: Any DATA chunks that were sent to the address for which the
T3-rtx timer expired but did not fit in one MTU (rule E3 above)
should be marked for retransmission and sent as soon as cwnd allows
(normally, when a SACK arrives).
*/
this.debugger.trace('retransmit tsn later %d', chunk.tsn)
chunk.retransmit = true
} else {
bundledCount++
bundledLength += chunk.user_data.length + 16
tsns.push(chunk.tsn)
this._sendChunk('data', chunk)
}
}
this.debugger.trace(
'retransmit %d chunks, %d bytes, %o',
bundledLength,
bundledCount,
tsns
)
if (bundledCount > 0) {
/*
E4) Start the retransmission timer T3-rtx on the destination address
to which the retransmission is sent, if rule R1 above indicates
to do so. The RTO to be used for starting T3-rtx should be the
one for the destination address to which the retransmission is
sent, which, when the receiver is multi-homed, may be different
from the destination address for which the timer expired (see
Section 6.4 below).
*/
this._startT3()
}
/*
After retransmitting, once a new RTT measurement is obtained (which
can happen only when new data has been sent and acknowledged, per
rule C5, or for a measurement made from a HEARTBEAT; see Section
8.3), the computation in rule C3 is performed, including the
computation of RTO, which may result in "collapsing" RTO back down
after it has been subject to doubling (rule E2).
*/
}
_retransmit () {
this.debugger.trace('check retransmits')
for (const tsn in this.sent) {
const chunk = this.sent[tsn]
if (chunk.retransmit) {
// TODO explain
this.debugger.warn('more retransmit', chunk.tsn)
this._sendChunk('data', chunk)
}
}
}
_fastRetransmit () {
/*
Note: Before the above adjustments, if the received SACK also
acknowledges new DATA chunks and advances the Cumulative TSN Ack
Point, the cwnd adjustment rules defined in Section 7.2.1 and Section
7.2.2 must be applied first.
*/
if (!this.fastRecovery) {
/*
If not in Fast Recovery, adjust the ssthresh and cwnd of the
destination address(es) to which the missing DATA chunks were
last sent, according to the formula described in Section 7.2.3.
ssthresh = max(cwnd/2, 4*MTU)
cwnd = ssthresh
partial_bytes_acked = 0
Basically, a packet loss causes cwnd to be cut in half.
*/
this.ssthresh = Math.max(this.cwnd / 2, 4 * this.PMTU)
this.cwnd = this.ssthresh
this.partial_bytes_acked = 0 // TODO
/*
If not in Fast Recovery, enter Fast Recovery and mark the highest
outstanding TSN as the Fast Recovery exit point. When a SACK
acknowledges all TSNs up to and including this exit point, Fast
Recovery is exited. While in Fast Recovery, the ssthresh and
cwnd SHOULD NOT change for any destinations due to a subsequent
Fast Recovery event (i.e., one SHOULD NOT reduce the cwnd further
due to a subsequent Fast Retransmit).
*/
this.fastRecovery = true
this.fastRecoveryExitPoint = this.my_next_tsn.prev()
this.debugger.trace('entered fast recovery mode, cwnd %d, ssthresh %d',
this.cwnd,
this.ssthresh
)
}
/*
3) Determine how many of the earliest (i.e., lowest TSN) DATA chunks
marked for retransmission will fit into a single packet, subject
to constraint of the path MTU of the destination transport
address to which the packet is being sent. Call this value K.
Retransmit those K DATA chunks in a single packet. When a Fast
Retransmit is being performed, the sender SHOULD ignore the value
of cwnd and SHOULD NOT delay retransmission for this single
packet.
*/
let bundledLength = 36 // 20 + 16
let bundledCount = 0
const tsns = []
for (const tsn in this.sent) {
const chunk = this.sent[tsn]
if (chunk.fastRetransmit) {
this.debugger.trace('fast retransmit tsn %d', chunk.tsn)
if (bundledLength + chunk.user_data.length + 16 > this.PMTU) {
return true
}
bundledCount++
bundledLength += chunk.user_data.length + 16
tsns.push(chunk.tsn)
this._sendChunk('data', chunk)
}
}
this.debugger.trace(
'fast retransmit %d chunks, %d bytes, %o',
bundledLength,
bundledCount,
tsns
)
/*
4) Restart the T3-rtx timer only if the last SACK acknowledged the
lowest outstanding TSN number sent to that address, or the
endpoint is retransmitting the first outstanding DATA chunk sent
to that address.
*/
// TODO: Restart the T3-rtx timer only if the last SACK acknowledged
if (bundledCount > 0) {
this._restartT3()
}
}
_up () {
/*
HEARTBEAT sending MAY begin upon reaching the
ESTABLISHED state and is discontinued after sending either SHUTDOWN
or SHUTDOWN-ACK. TODO
*/
this.state = 'ESTABLISHED'
this._enableHeartbeat()
this.debugger.info('association established')
this.emit('COMMUNICATION UP')
}
_down () {
clearInterval(this._heartbeatInterval)
clearTimeout(this.T1)
clearTimeout(this.T2)
clearTimeout(this.T3)
clearTimeout(this._sack_timer)
}
_enableHeartbeat () {
this._heartbeatInterval = setInterval(() => {
/*
To probe an address for verification, an endpoint will send
HEARTBEATs including a 64-bit random nonce and a path indicator (to
identify the address that the HEARTBEAT is sent to) within the
HEARTBEAT parameter.
*/
for (const address in this.destinations) {
const destination = this.destinations[address]
const heartbeatInfo = crypto.randomBytes(12)
const nonce = heartbeatInfo.readUInt32BE(0)
this.nonces[nonce] = true
ip.toBuffer(address, heartbeatInfo, 8)
this.debugger.trace(
'> heartbeat to %s, %d bytes',
address,
heartbeatInfo.length,
heartbeatInfo,
destination
)
this._sendChunk('heartbeat', { heartbeat_info: heartbeatInfo }, address)
/*
The endpoint should increment the respective error counter of the
destination transport address each time a HEARTBEAT is sent to that
address and not acknowledged within one RTO.
When the value of this counter reaches the protocol parameter
'Path.Max.Retrans', the endpoint should mark the corresponding
destination address as inactive if it is not so marked, and may also
optionally report to the upper layer the change of reachability of
this destination address. After this, the endpoint should continue
HEARTBEAT on this destination address but should stop increasing the
counter.
*/
}
}, this.hb_interval)
}
_sendPacket (buffers, destination, callbacks) {
// TODO: order of destroying
if (this.mute) {
return
}
if (!this.endpoint) {
return
}
this.endpoint._sendPacket(
destination || this.remoteAddress,
this.remotePort,
this.peer_tag,
buffers,
() => {
callbacks.forEach(cb => {
// Callback for each last chunk
if (typeof cb === 'function') {
cb()
}
})
}
)
}
_deliver (data, stream, ppid) {
this.debugger.debug('< receive user data %d bytes, ppid %s', data.length, ppid)
if (this.listeners('DATA ARRIVE')) {
this.debugger.trace('emit DATA ARRIVE')
data.ppid = ppid
this.readBuffer.push(data)
this.emit('DATA ARRIVE', stream)
}
/*
An SCTP receiver MUST NOT generate more than one SACK for every
incoming packet, other than to update the offered window as the
receiving application consumes new data.
*/
this.scheduleSack()
}
_bundle () {
if (this.state === 'CLOSED') {
return
}
if (this.queue.length === 0) {
return
}
this.bundling--
if (this.bundling > 0) {
return
}
let callbacks = []
let bundledChunks = []
let bundledLength = 36 // 20 + 16
const mtu = this.PMTU
const emulateLoss = false
let haveCookieEcho = false
let haveData = false
let tsns = []
let sack
let skip
// Move last sack to the beginning of queue, ignore others
const processedQueue = []
this.queue.forEach(chunk => {
if (chunk.chunkType === 'sack') {
sack = chunk
} else {
processedQueue.push(chunk)
}
})
if (sack) {
processedQueue.unshift(sack)
}
this.debugger.trace('process bundle queue %O', processedQueue)
processedQueue.forEach((chunk, index) => {
let buffer
if (chunk.size > mtu) {
this.debugger.warn('chunk size %d > MTU %d', chunk.size, mtu)
// TODO split chunks? they were already split at send()
skip = true
} else if (chunk.chunkType === 'data') {
haveData = true
/*
Data transmission MUST only happen in the ESTABLISHED, SHUTDOWN-
PENDING, and SHUTDOWN-RECEIVED states. The only exception to this is
that DATA chunks are allowed to be bundled with an outbound COOKIE
ECHO chunk when in the COOKIE-WAIT state.
*/
if (
this.state === 'ESTABLISHED' ||
this.state === 'SHUTDOWN-PENDING' ||
this.state === 'SHUTDOWN-RECEIVED'
) {
// Allow
} else if (this.state === 'COOKIE-WAIT' && haveCookieEcho) {
// Allow
} else {
// TODO: force bundle
this.debugger.warn(
'data transmission MUST only happen ' +
'in the ESTABLISHED, SHUTDOWN-PENDING, ' +
'and SHUTDOWN-RECEIVED states'
)
return
}
/*
IMPLEMENTATION NOTE: In order to better support the data life time
option, the transmitter may hold back the assigning of the TSN number
to an outbound DATA chunk to the last moment. And, for
implementation simplicity, once a TSN number has been assigned the
sender should consider the send of this DATA chunk as committed,
overriding any life time option attached to the DATA chunk.
*/