Add initial handling of acks (#406)

* Add initial handling of acks

Add implemetaion of circular buffer based on reference implementation
Add way to test number of packet in flight
Add acking of initial syn packet
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KonradStaniec 2021-10-15 13:38:51 +02:00 committed by GitHub
parent 7ae287ad1b
commit 6fbf129ba9
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9 changed files with 280 additions and 24 deletions

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@ -65,7 +65,7 @@ jobs:
uses: actions/cache@v1
with:
path: rocks-db-cache-${{ matrix.target.cpu }}
key: 'rocksdb-${{ matrix.target.os }}-${{ matrix.target.cpu }}'
key: 'rocksdb-v1-${{ matrix.target.os }}-${{ matrix.target.cpu }}'
- name: Build and install rocksdb (Linux i386)
# no librocksdb-dev:i386

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@ -0,0 +1,67 @@
import
std/[options, math]
export options
# Buffer implementation similar to the one in in reference implementation.
# Main rationale for it, is to refer to items in buffer by their sequence number,
# and support out of order packets.
# Therefore it is super specific data structure, and it mostly usefull for
# utp implementation.
# Another alternative would be to use standard deque from deques module, and caluclate
# item indexes from their sequence numbers.
type GrowableCircularBuffer*[A] = object
items: seq[Option[A]]
mask: int
# provided size will always be adjusted to next power of two
proc init*[A](T: type GrowableCircularBuffer[A], size: Natural = 16): T =
let powOfTwoSize = nextPowerOfTwo(size)
T(
items: newSeq[Option[A]](size),
mask: powOfTwoSize - 1
)
proc get*[A](buff: GrowableCircularBuffer[A], i: Natural): Option[A] =
buff.items[i and buff.mask]
proc putImpl[A](buff: var GrowableCircularBuffer[A], i: Natural, elem: Option[A]) =
buff.items[i and buff.mask] = elem
proc put*[A](buff: var GrowableCircularBuffer[A], i: Natural, elem: A) =
buff.putImpl(i, some(elem))
proc delete*[A](buff: var GrowableCircularBuffer[A], i: Natural) =
buff.putImpl(i, none[A]())
proc len*[A](buff: GrowableCircularBuffer[A]): int =
buff.mask + 1
# Item contains the element we want to make space for
# index is the index in the list.
proc ensureSize*[A](buff: var GrowableCircularBuffer[A], item: Natural, index: Natural) =
# Increase size until is next power of 2 which consists given index
proc getNextSize(currentSize: int, index: int): int =
var newSize = currentSize
while true:
newSize = newSize * 2
if not (index >= newSize):
break
newSize
if (index > buff.mask):
let currentSize = buff.mask + 1
let newSize = getNextSize(currentSize, index)
let newMask = newSize - 1
var newSeq = newSeq[Option[A]](newSize)
var i = 0
while i <= buff.mask:
let idx = item - index + i
newSeq[idx and newMask] = buff.get(idx)
inc i
buff.items = move(newSeq)
buff.mask = newMask
iterator items*[A](buff: GrowableCircularBuffer[A]): Option[A] =
for e in buff.items:
yield e

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@ -33,9 +33,13 @@ type
extension*: uint8
connectionId*: uint16
timestamp*: MicroSeconds
# This is the difference between the local time, at the time the last packet
# was received, and the timestamp in this last received packet
timestampDiff*: MicroSeconds
# The window size is the number of bytes currently in-flight, i.e. sent but not acked
wndSize*: uint32
seqNr*: uint16
# sequence number the sender of the packet last received in the other direction
ackNr*: uint16
Packet* = object

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@ -24,4 +24,6 @@ when isMainModule:
let remoteServer = initTAddress("127.0.0.1", 9078)
let soc = waitFor utpProt.connectTo(remoteServer)
doAssert(soc.numPacketsInOutGoingBuffer() == 0)
waitFor utpProt.closeWait()

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@ -10,6 +10,7 @@ import
std/[tables, options, hashes],
chronos, chronicles, bearssl,
./packets,
./growable_buffer,
../keys
logScope:
@ -41,16 +42,30 @@ type
seqNr: uint16
# All seq number up to this havve been correctly acked by us
ackNr: uint16
# Should be completed after succesful connection to remote host.
# TODO check if nim gc handles properly cyclic references, as this future will
# contain reference to socket which hold this future.
# If that is not the case, then this future will need to be hold independly
connectionFuture: Future[UtpSocket]
# the number of packets in the send queue. Packets that haven't
# yet been sent count as well as packets marked as needing resend
# the oldest un-acked packet in the send queue is seq_nr - cur_window_packets
curWindowPackets: uint16
# out going buffer for all send packets
outBuffer: GrowableCircularBuffer[Packet]
# incoming buffer for out of order packets
inBuffer: GrowableCircularBuffer[Packet]
UtpSocketsContainerRef = ref object
sockets: Table[UtpSocketKey, UtpSocket]
AckResult = enum
PacketAcked, PacketAlreadyAcked, PacketNotSentYet
# For now utp protocol is tied to udp transport, but ultimatly we would like to
# abstract underlying transport to be able to run utp over udp, discoveryv5 or
# maybe some test transport
@ -62,6 +77,9 @@ type
proc new(T: type UtpSocketsContainerRef): T =
UtpSocketsContainerRef(sockets: initTable[UtpSocketKey, UtpSocket]())
proc init(T: type UtpSocketKey, remoteAddress: TransportAddress, rcvId: uint16): T =
UtpSocketKey(remoteAddress: remoteAddress, rcvId: rcvId)
# This should probably be defined in TransportAddress module, as hash function should
# be consitent with equality function
# in nim zero arrays always have hash equal to 0, irrespectively of array size, to
@ -117,7 +135,9 @@ proc initOutgoingSocket(to: TransportAddress, rng: var BrHmacDrbgContext): UtpSo
connectionIdRcv: rcvConnectionId,
connectionIdSnd: sndConnectionId,
seqNr: initialSeqNr,
connectionFuture: newFuture[UtpSocket]()
connectionFuture: newFuture[UtpSocket](),
outBuffer: GrowableCircularBuffer[Packet].init(),
inBuffer: GrowableCircularBuffer[Packet].init()
)
proc initIncomingSocket(to: TransportAddress, connectionId: uint16, ackNr: uint16, rng: var BrHmacDrbgContext): UtpSocket =
@ -129,21 +149,78 @@ proc initIncomingSocket(to: TransportAddress, connectionId: uint16, ackNr: uint1
connectionIdSnd: connectionId,
seqNr: initialSeqNr,
ackNr: ackNr,
connectionFuture: newFuture[UtpSocket]()
connectionFuture: newFuture[UtpSocket](),
outBuffer: GrowableCircularBuffer[Packet].init(),
inBuffer: GrowableCircularBuffer[Packet].init()
)
proc ack(socket: UtpSocket): Packet =
proc getAckPacket(socket: UtpSocket): Packet =
ackPacket(socket.seqNr, socket.connectionIdSnd, socket.ackNr, 1048576)
proc ackPacket(socket: UtpSocket, seqNr: uint16): AckResult =
let packetOpt = socket.outBuffer.get(seqNr)
if packetOpt.isSome():
let packet = packetOpt.get()
# TODO Add number of transmision to each packet to track which packet was sent
# how many times, and handle here case when we try to ack packet which was not
# sent yet
socket.outBuffer.delete(seqNr)
# TODO Update estimates about roundtrip time, when we are acking packed which
# acked without re sends
PacketAcked
else:
# the packet has already been acked (or not sent)
PacketAlreadyAcked
proc ackPackets(socket: UtpSocket, nrPacketsToAck: uint16) =
var i = 0
while i < int(nrPacketsToack):
let result = socket.ackPacket(socket.seqNr - socket.curWindowPackets)
case result
of PacketAcked:
dec socket.curWindowPackets
of PacketAlreadyAcked:
dec socket.curWindowPackets
of PacketNotSentYet:
debug "Tried to ack packed which was not sent yet"
break
inc i
proc getSocketKey(socket: UtpSocket): UtpSocketKey =
UtpSocketKey.init(socket.remoteAddress, socket.connectionIdRcv)
proc initSynPacket(socket: UtpSocket): seq[byte] =
assert(socket.state == SynSent)
let packet = synPacket(socket.seqNr, socket.connectionIdRcv, 1048576)
socket.outBuffer.ensureSize(socket.seqNr, socket.curWindowPackets)
socket.outBuffer.put(socket.seqNr, packet)
inc socket.seqNr
inc socket.curWindowPackets
encodePacket(packet)
proc isConnected*(socket: UtpSocket): bool =
socket.state == Connected
# Check how many packets are still in the out going buffer, usefull for tests or
# debugging.
# It throws assertion error when number of elements in buffer do not equal kept counter
proc numPacketsInOutGoingBuffer*(socket: UtpSocket): int =
var num = 0
for e in socket.outBuffer.items():
if e.isSome():
inc num
assert(num == int(socket.curWindowPackets))
num
# TODO not implemented
# for now just log incoming packets
proc processPacket(prot: UtpProtocol, p: Packet, sender: TransportAddress) =
notice "Received packet ", packet = p
let socketKey = UtpSocketKey(remoteAddress: sender, rcvId: p.header.connectionId)
let socketKey = UtpSocketKey.init(sender, p.header.connectionId)
let maybeSocket = prot.activeSockets.getUtpSocket(socketKey)
let pkSeqNr = p.header.seqNr
let pkAckNr = p.header.ackNr
if (maybeSocket.isSome()):
let socket = maybeSocket.unsafeGet()
case p.header.pType
@ -155,12 +232,31 @@ proc processPacket(prot: UtpProtocol, p: Packet, sender: TransportAddress) =
notice "Received ST_FIN on known socket"
of ST_STATE:
notice "Received ST_STATE on known socket"
# acks is the number of packets that was acked, in normal case - no selective
# acks, no losses, no resends, it will usually be equal to 1
let acks = pkAckNr - (socket.seqNr - 1 - socket.curWindowPackets)
socket.ackPackets(acks)
if (socket.state == SynSent):
socket.state = Connected
socket.ackNr = p.header.seqNr
# TODO reference implementation sets ackNr (p.header.seqNr - 1), although
# spec mention that it should be equal p.header.seqNr. For now follow the
# reference impl to be compatible with it. Later investigate trin compatibility.
socket.ackNr = p.header.seqNr - 1
# In case of SynSent complate the future as last thing to make sure user of libray will
# receive socket in correct state
socket.connectionFuture.complete(socket)
# TODO to finish handhske we should respond with ST_DATA packet, without it
# socket is left in half-open state
# number of packets past the expected
# ack_nr is the last acked, seq_nr is the
# current. Subtracring 1 makes 0 mean "this is the next expected packet"
let pastExpected = pkSeqNr - socket.ackNr - 1
# TODO to finish handhske we should respond with ST_DATA packet, without it
# socket is left in half-open state.
# Actual reference implementation waits for user to send data, as it assumes
# existence of application level handshake over utp. We may need to modify this
# to automaticly send ST_DATA .
of ST_RESET:
# TODO not implemented
notice "Received ST_RESET on known socket"
@ -173,12 +269,10 @@ proc processPacket(prot: UtpProtocol, p: Packet, sender: TransportAddress) =
if (p.header.pType == ST_SYN):
# Initial ackNr is set to incoming packer seqNr
let incomingSocket = initIncomingSocket(sender, p.header.connectionId, p.header.seqNr, prot.rng[])
let socketKey = UtpSocketKey(remoteAddress: incomingSocket.remoteAddress, rcvId: incomingSocket.connectionIdRcv)
prot.activeSockets.registerUtpSocket(socketKey, incomingSocket)
let synAck = incomingSocket.ack()
let encoded = encodePacket(synAck)
prot.activeSockets.registerUtpSocket(incomingSocket.getSocketKey(), incomingSocket)
let encodedAck= encodePacket(incomingSocket.getAckPacket())
# TODO sending should be done from UtpSocket context
discard prot.transport.sendTo(sender, encoded)
discard prot.transport.sendTo(sender, encodedAck)
notice "Received ST_SYN and socket is not known"
else:
# TODO not implemented
@ -189,16 +283,13 @@ proc processPacket(prot: UtpProtocol, p: Packet, sender: TransportAddress) =
# TODO not implemented
proc connectTo*(p: UtpProtocol, address: TransportAddress): Future[UtpSocket] =
let socket = initOutgoingSocket(address, p.rng[])
let socketKey = UtpSocketKey(remoteAddress: socket.remoteAddress, rcvId: socket.connectionIdRcv)
# TODO Buffer in syn packet should be based on our current buffer size
let packet = synPacket(socket.seqNr, socket.connectionIdRcv, 1048576)
notice "Sending packet", packet = packet
let packetEncoded = encodePacket(packet)
p.activeSockets.registerUtpSocket(socketKey, socket)
p.activeSockets.registerUtpSocket(socket.getSocketKey(), socket)
let synEncoded = socket.initSynPacket()
notice "Sending packet", packet = synEncoded
# TODO add callback to handle errors and cancellation i.e unregister socket on
# send error and finish connection future with failure
# sending should be done from UtpSocketContext
discard p.transport.sendTo(address, packetEncoded)
discard p.transport.sendTo(address, synEncoded)
return socket.connectionFuture
proc processDatagram(transp: DatagramTransport, raddr: TransportAddress):

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@ -8,4 +8,5 @@
import
./test_packets,
./test_protocol
./test_protocol,
./test_buffer

88
tests/utp/test_buffer.nim Normal file
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@ -0,0 +1,88 @@
# Copyright (c) 2020-2021 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
{.used.}
import
unittest,
../../eth/utp/growable_buffer
suite "Utp ring buffer":
test "Empty buffer":
let buff = GrowableCircularBuffer[int].init(size = 4)
check:
buff.len() == 4
buff.get(0).isNone()
test "Adding elements to buffer":
var buff = GrowableCircularBuffer[int].init(size = 4)
buff.put(11, 11)
buff.put(12, 12)
buff.put(13, 13)
buff.put(14, 14)
check:
buff.get(11) == some(11)
buff.get(12) == some(12)
buff.get(13) == some(13)
buff.get(14) == some(14)
test "Deleting elements from buffer":
var buff = GrowableCircularBuffer[int].init(size = 4)
buff.put(11, 11)
check:
buff.get(11) == some(11)
buff.delete(11)
check:
buff.get(11) == none[int]()
test "Adding elements to buffer while ensuring proper size":
var buff = GrowableCircularBuffer[int].init(size = 4)
buff.put(11, 11)
buff.put(12, 12)
buff.put(13, 13)
buff.put(14, 14)
# next element will be 5 in buffer, so it has index equal to 4
buff.ensureSize(15, 4)
buff.put(15, 15)
check:
# it growed to next power of two
buff.len() == 8
buff.get(11) == some(11)
buff.get(12) == some(12)
buff.get(13) == some(13)
buff.get(14) == some(14)
buff.get(15) == some(15)
test "Adding out of order elements to buffer while ensuring proper size":
var buff = GrowableCircularBuffer[int].init(size = 4)
buff.put(11, 11)
buff.put(12, 12)
buff.put(13, 13)
buff.put(14, 14)
# element with nr 17 will be on needed on index 6
buff.ensureSize(17, 6)
buff.put(17, 17)
check:
# it growed to next power of two
buff.len() == 8
buff.get(11) == some(11)
buff.get(12) == some(12)
buff.get(13) == some(13)
buff.get(14) == some(14)
# elements 15 and 16 are not present yet
buff.get(15) == none[int]()
buff.get(16) == none[int]()
buff.get(17) == some(17)

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@ -8,8 +8,8 @@
import
unittest,
../eth/utp/packets,
../../eth/keys
../../eth/utp/packets,
../../eth/keys
suite "Utp packets encoding/decoding":

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@ -26,6 +26,9 @@ procSuite "Utp protocol tests":
check:
sock.isConnected()
# after successful connection outgoing buffer should be empty as syn packet
# should be correctly acked
sock.numPacketsInOutGoingBuffer() == 0
await utpProt1.closeWait()
await utpProt2.closeWait()