nim-libp2p/libp2p/muxers/mplex/lpchannel.nim

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## Nim-LibP2P
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## Copyright (c) 2019 Status Research & Development GmbH
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## Licensed under either of
## * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
## * MIT license ([LICENSE-MIT](LICENSE-MIT))
## at your option.
## This file may not be copied, modified, or distributed except according to
## those terms.
import std/[oids, strformat]
import chronos, chronicles, metrics
import ./coder,
../muxer,
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nimcrypto/utils,
../../stream/[bufferstream, connection, streamseq],
../../peerinfo
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export connection
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logScope:
topics = "mplexchannel"
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## Channel half-closed states
##
## | State | Closed local | Closed remote
## |=============================================
## | Read | Yes (until EOF) | No
## | Write | No | Yes
##
## Channels are considered fully closed when both outgoing and incoming
## directions are closed and when the reader of the channel has read the
## EOF marker
const
MaxWrites = 1024 ##\
## Maximum number of in-flight writes - after this, we disconnect the peer
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type
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LPChannel* = ref object of BufferStream
id*: uint64 # channel id
name*: string # name of the channel (for debugging)
conn*: Connection # wrapped connection used to for writing
initiator*: bool # initiated remotely or locally flag
isOpen*: bool # has channel been opened
closedLocal*: bool # has channel been closed locally
msgCode*: MessageType # cached in/out message code
closeCode*: MessageType # cached in/out close code
resetCode*: MessageType # cached in/out reset code
writes*: int # In-flight writes
proc open*(s: LPChannel) {.async, gcsafe.}
func shortLog*(s: LPChannel): auto =
if s.isNil: "LPChannel(nil)"
elif s.conn.peerInfo.isNil: $s.oid
elif s.name != $s.oid and s.name.len > 0:
&"{shortLog(s.conn.peerInfo.peerId)}:{s.oid}:{s.name}"
else: &"{shortLog(s.conn.peerInfo.peerId)}:{s.oid}"
chronicles.formatIt(LPChannel): shortLog(it)
proc open*(s: LPChannel) {.async, gcsafe.} =
trace "Opening channel", s, conn = s.conn
await s.conn.writeMsg(s.id, MessageType.New, s.name)
s.isOpen = true
method closed*(s: LPChannel): bool =
s.closedLocal
proc closeUnderlying(s: LPChannel): Future[void] {.async.} =
## Channels may be closed for reading and writing in any order - we'll close
## the underlying bufferstream when both directions are closed
if s.closedLocal and s.isEof:
await procCall BufferStream(s).close()
proc reset*(s: LPChannel) {.async, gcsafe.} =
if s.isClosed:
trace "Already closed", s
return
trace "Resetting channel", s, len = s.len
# First, make sure any new calls to `readOnce` and `pushData` etc will fail -
# there may already be such calls in the event queue however
s.closedLocal = true
s.isEof = true
s.readBuf = StreamSeq()
s.pushedEof = true
for i in 0..<s.pushing:
# Make sure to drain any ongoing pushes - there's already at least one item
# more in the queue already so any ongoing reads shouldn't interfere
# Notably, popFirst is not fair - which reader/writer gets woken up depends
discard await s.readQueue.popFirst()
if s.readQueue.len == 0 and s.pushing == 0:
# There is no push ongoing and nothing on the queue - let's place an
# EOF marker there so that any reader is woken up - we don't need to
# synchronize here
await s.readQueue.addLast(@[])
if not s.conn.isClosed:
# If the connection is still active, notify the other end
proc resetMessage() {.async.} =
try:
trace "sending reset message", s, conn = s.conn
await s.conn.writeMsg(s.id, s.resetCode) # write reset
except CatchableError as exc:
# No cancellations, errors handled in writeMsg
trace "Can't send reset message", s, conn = s.conn, msg = exc.msg
asyncSpawn resetMessage()
# This should wake up any readers by pushing an EOF marker at least
await procCall BufferStream(s).close() # noraises, nocancels
trace "Channel reset", s
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method close*(s: LPChannel) {.async, gcsafe.} =
## Close channel for writing - a message will be sent to the other peer
## informing them that the channel is closed and that we're waiting for
## their acknowledgement.
if s.closedLocal:
trace "Already closed", s
return
s.closedLocal = true
trace "Closing channel", s, conn = s.conn, len = s.len
if s.isOpen:
try:
await s.conn.writeMsg(s.id, s.closeCode) # write close
except CancelledError as exc:
raise exc
except CatchableError as exc:
# It's harmless that close message cannot be sent - the connection is
# likely down already
trace "Cannot send close message", s, id = s.id
await s.closeUnderlying() # maybe already eofed
trace "Closed channel", s, len = s.len
method initStream*(s: LPChannel) =
if s.objName.len == 0:
s.objName = "LPChannel"
s.timeoutHandler = proc(): Future[void] {.gcsafe.} =
trace "Idle timeout expired, resetting LPChannel", s
s.reset()
procCall BufferStream(s).initStream()
method readOnce*(s: LPChannel,
pbytes: pointer,
nbytes: int):
Future[int] {.async.} =
## Mplex relies on reading being done regularly from every channel, or all
## channels are blocked - in particular, this means that reading from one
## channel must not be done from within a callback / read handler of another
## or the reads will lock each other.
try:
let bytes = await procCall BufferStream(s).readOnce(pbytes, nbytes)
trace "readOnce", s, bytes
if bytes == 0:
await s.closeUnderlying()
return bytes
except CatchableError as exc:
await s.closeUnderlying()
raise exc
method write*(s: LPChannel, msg: seq[byte]): Future[void] {.async.} =
## Write to mplex channel - there may be up to MaxWrite concurrent writes
## pending after which the peer is disconencted
if s.closedLocal or s.conn.closed:
raise newLPStreamClosedError()
if msg.len == 0:
return
if s.writes >= MaxWrites:
debug "Closing connection, too many in-flight writes on channel",
s, conn = s.conn, writes = s.writes
await s.conn.close()
return
s.writes += 1
try:
if not s.isOpen:
await s.open()
# writes should happen in sequence
trace "write msg", s, conn = s.conn, len = msg.len
await s.conn.writeMsg(s.id, s.msgCode, msg)
s.activity = true
except CatchableError as exc:
trace "exception in lpchannel write handler", s, msg = exc.msg
await s.conn.close()
raise exc
finally:
s.writes -= 1
proc init*(
L: type LPChannel,
id: uint64,
conn: Connection,
initiator: bool,
name: string = "",
timeout: Duration = DefaultChanTimeout): LPChannel =
let chann = L(
id: id,
name: name,
conn: conn,
initiator: initiator,
timeout: timeout,
isOpen: if initiator: false else: true,
msgCode: if initiator: MessageType.MsgOut else: MessageType.MsgIn,
closeCode: if initiator: MessageType.CloseOut else: MessageType.CloseIn,
resetCode: if initiator: MessageType.ResetOut else: MessageType.ResetIn,
dir: if initiator: Direction.Out else: Direction.In)
chann.initStream()
when chronicles.enabledLogLevel == LogLevel.TRACE:
chann.name = if chann.name.len > 0: chann.name else: $chann.oid
trace "Created new lpchannel", chann, id, initiator
return chann