108 lines
3.9 KiB
Nim
108 lines
3.9 KiB
Nim
import asyncdispatch, asyncnet, net, port_prediction, strformat
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from nativesockets import
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SockAddr,
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SockAddr_storage,
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SockLen,
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getSockOptInt,
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setSockOptInt
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from sequtils import any
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type
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Attempt* = object
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## A hole punching attempt.
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srcPort*: Port
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dstIp*: IpAddress
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dstPorts*: seq[Port]
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future*: Future[Port]
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Puncher* = ref object
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sock: AsyncSocket
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attempts: seq[Attempt]
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PunchHoleError* = object of ValueError
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var IPPROTO_IP {.importc: "IPPROTO_IP", header: "<netinet/in.h>".}: cint
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var IP_TTL {.importc: "IP_TTL", header: "<netinet/in.h>".}: cint
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const Timeout = 3000
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proc `==`(a, b: Attempt): bool =
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## ``==`` for hole punching attempts.
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##
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## Two hole punching attempts are considered equal if their ``srcPort`` and
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## ``dstIp`` are equal and their ``dstPorts`` overlap.
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a.srcPort == b.srcPort and a.dstIp == b.dstIp and
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a.dstPorts.any(proc (p: Port): bool = p in b.dstPorts)
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proc initPuncher*(sock: AsyncSocket): Puncher =
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Puncher(sock: sock)
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proc punch(puncher: Puncher, peerIp: IpAddress, peerPort: Port,
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peerProbedPorts: seq[Port], lowTTL: bool, msg: string):
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Future[Attempt] {.async.} =
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let punchFuture = newFuture[Port]("punch")
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let predictedDstPorts = predictPortRange(peerPort, peerProbedPorts)
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let (_, myPort) = puncher.sock.getLocalAddr()
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result = Attempt(srcPort: myPort, dstIp: peerIp, dstPorts: predictedDstPorts,
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future: punchFuture)
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if puncher.attempts.contains(result):
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raise newException(PunchHoleError,
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"hole punching for given parameters already active")
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puncher.attempts.add(result)
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echo &"sending msg {msg} to {peerIp}, predicted ports: {result.dstPorts}"
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var peerAddr: Sockaddr_storage
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var peerSockLen: SockLen
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try:
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var defaultTTL: int
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if lowTTL:
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defaultTTL = puncher.sock.getFd.getSockOptInt(IPPROTO_IP, IP_TTL)
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puncher.sock.getFd.setSockOptInt(IPPROTO_IP, IP_TTL, 2)
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for dstPort in result.dstPorts:
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toSockAddr(result.dstIp, dstPort, peerAddr, peerSockLen)
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# TODO: replace asyncdispatch.sendTo with asyncnet.sendTo (Nim 1.4 required)
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await sendTo(puncher.sock.getFd().AsyncFD, msg.cstring, msg.len,
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cast[ptr SockAddr](addr peerAddr), peerSockLen)
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if lowTTL:
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puncher.sock.getFd.setSockOptInt(IPPROTO_IP, IP_TTL, defaultTTL)
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except OSError as e:
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raise newException(PunchHoleError, e.msg)
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proc initiate*(puncher: Puncher, peerIp: IpAddress, peerPort: Port,
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peerProbedPorts: seq[Port]): Future[Attempt] =
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punch(puncher, peerIp, peerPort, peerProbedPorts, true, "SYN")
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proc respond*(puncher: Puncher, peerIp: IpAddress, peerPort: Port,
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peerProbedPorts: seq[Port]): Future[Attempt] =
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punch(puncher, peerIp, peerPort, peerProbedPorts, false, "ACK")
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proc finalize*(attempt: Attempt): Future[Port] {.async.} =
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await attempt.future or sleepAsync(Timeout)
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if attempt.future.finished:
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result = attempt.future.read()
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else:
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raise newException(PunchHoleError, "timeout")
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proc handleMsg*(puncher: Puncher, msg: string, peerIp: IpAddress,
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peerPort: Port) =
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## Handles an incoming UDP message which may complete the Futures returned by
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## ``initiate`` and ``respond``.
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if msg == "SYN":
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# We received a SYN packet. We ignore it because we expected it to be
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# filtered by our NAT.
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return
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echo &"handling ACK message from {peerIp}:{peerPort}"
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let (_, myPort) = puncher.sock.getLocalAddr()
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let query = Attempt(srcPort: myPort, dstIp: peerIp, dstPorts: @[peerPort])
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let i = puncher.attempts.find(query)
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if i != -1:
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puncher.attempts[i].future.complete(peerPort)
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puncher.attempts.del(i)
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proc handleMsg*(puncher: Puncher, msg: string,
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peerAddr: SockAddr | Sockaddr_storage, peerSockLen: SockLen) =
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var peerIp: IpAddress
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var peerPort: Port
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fromSockAddr(peerAddr, peerSockLen, peerIp, peerPort)
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handleMsg(puncher, msg, peerIp, peerPort)
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