301 lines
12 KiB
Nim
301 lines
12 KiB
Nim
import algorithm
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import net
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import sequtils
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import unittest
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type
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NatType* = enum
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Unknown,
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Cone,
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SymmetricProgressive,
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SymmetricRandom
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NatProperties* = object
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case natType*: NatType
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of Unknown:
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guess*: seq[uint16]
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of Cone:
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prediction*: uint16
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of SymmetricProgressive:
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order*: SortOrder
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previousPort*: uint16
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minDistance*: uint16
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maxDistance*: uint16
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of SymmetricRandom:
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minPort*: uint16
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maxPort*: uint16
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const RandomPortCount = 10000'u16
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proc min(a, b: uint16): uint16 =
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min(a.int32, b.int32).uint16
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proc toUInt16(p: Port): uint16 = uint16(p)
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proc toPort(u: uint16): Port = Port(u)
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proc addOffset(port: uint16, offset: uint16, minValue = 1024'u16,
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maxValue = uint16.high): uint16 =
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assert(port >= minValue)
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assert(port <= maxValue)
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let distanceToMaxValue = maxValue - port
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if distanceToMaxValue < offset:
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return minValue + offset - distanceToMaxValue - 1
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return port + offset
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proc subtractOffset(port: uint16, offset: uint16, minValue = 1024'u16,
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maxValue = uint16.high): uint16 =
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assert(port >= minValue)
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assert(port <= maxValue)
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let distanceToMinValue = port - minValue
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if distanceToMinValue < offset:
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return maxValue - offset + distanceToMinValue + 1
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return port - offset
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proc getNatProperties*(localPort: uint16, probedPorts: seq[uint16]):
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NatProperties =
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if probedPorts.len == 0:
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# No probed ports, so our only guess can be that the NAT is a cone-type NAT
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# and the port allocation preserves the local Port.
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return NatProperties(natType: Unknown, guess: @[localPort])
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if probedPorts.len == 1:
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# Only one server was used for probing, so we cannot know if the NAT is
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# symmetric or not. We are trying the probed port (assuming cone-type NAT)
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# and the next port in a progressive sequence if applicable (assuming
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# symmetric NAT with progressive port allocation).
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result = NatProperties(natType: Unknown, guess: @[probedPorts[0]])
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if probedPorts[0] > localPort:
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let offset = probedPorts[0] - localPort
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result.guess.add(probedPorts[0].addOffset(offset))
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elif probedPorts[0] < localPort:
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let offset = localPort - probedPorts[0]
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result.guess.add(probedPorts[0].subtractOffset(offset))
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return
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let deduplicatedPorts = probedPorts.deduplicate()
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if deduplicatedPorts.len() == 1:
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# It looks like the NAT is a cone-type NAT.
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return NatProperties(natType: Cone, prediction: deduplicatedPorts[0])
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let probedPortsSorted = probedPorts.sorted()
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let minPort = probedPortsSorted[probedPortsSorted.minIndex()]
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let maxPort = probedPortsSorted[probedPortsSorted.maxIndex()]
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var minDistance = uint16.high()
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var maxDistance = uint16.low()
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for i in 1 .. probedPortsSorted.len() - 1:
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# FIXME: use rotated distance
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let distance = probedPortsSorted[i] - probedPortsSorted[i - 1]
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minDistance = min(minDistance, distance)
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maxDistance = max(maxDistance, distance)
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if maxDistance < 10:
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if probedPorts.isSorted(Ascending):
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# assume symmetric NAT with positive-progressive port allocation
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return NatProperties(natType: SymmetricProgressive,
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order: Ascending, previousPort: maxPort,
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minDistance: minDistance, maxDistance: maxDistance)
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if probedPorts.isSorted(Descending):
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# assume symmetric NAT with negative-progressive port allocation
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return NatProperties(natType: SymmetricProgressive,
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order: Descending, previousPort: minPort,
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minDistance: minDistance, maxDistance: maxDistance)
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# assume symmetric NAT with random port allocation
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return NatProperties(natType: SymmetricRandom, minPort: minPort,
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maxPort: maxPort)
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proc getNatProperties*(localPort: Port, probedPorts: seq[Port]): NatProperties =
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getNatProperties(localPort.uint16, probedPorts.map(toUInt16))
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proc predictPortRange*(props: NatProperties): seq[Port] =
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case props.natType
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of Unknown:
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result = props.guess.map(toPort)
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of Cone:
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result = @[Port(props.prediction)]
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of SymmetricProgressive:
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if props.order == Ascending:
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if props.minDistance == props.maxDistance:
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return @[Port(props.previousPort.addOffset(props.maxDistance))]
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else:
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let minPort = props.previousPort - props.maxDistance
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for i in countup(0'u16, props.maxDistance):
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result.add(Port(minPort.addOffset(i)))
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else:
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if props.minDistance == props.maxDistance:
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return @[Port(props.previousPort.subtractOffset(props.maxDistance))]
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else:
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let maxPort = props.previousPort + props.maxDistance
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for i in countup(0'u16, props.maxDistance):
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result.add(Port(maxPort.subtractOffset(i)))
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of SymmetricRandom:
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assert(RandomPortCount mod 2 == 0)
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let center = props.minPort + (props.maxPort - props.minPort) div 2
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let half = RandomPortCount div 2
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let first = if (1024'u16 + half) < center:
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min(center - half, uint16.high - RandomPortCount + 1)
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else:
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1024'u16
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result = newSeq[Port](RandomPortCount)
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for i in 0'u16 .. RandomPortCount - 1'u16:
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result[i] = Port(first + i)
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suite "port prediction tests":
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test "single port":
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let props = getNatProperties(1234'u16, @[])
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check(props.natType == Unknown)
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check(props.guess == @[1234'u16])
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let predicted = predictPortRange(props)
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check(predicted == @[Port(1234)])
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test "single probe equal":
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let props = getNatProperties(1234'u16, @[1234'u16])
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check(props.natType == Unknown)
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check(props.guess == @[1234'u16])
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let predicted = predictPortRange(props)
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check(predicted == @[Port(1234)])
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test "single probe positive-progressive":
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let props = getNatProperties(1234'u16, @[1236'u16])
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check(props.natType == Unknown)
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check(props.guess == @[1236'u16, 1238'u16])
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let predicted = predictPortRange(props)
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check(predicted == @[Port(1236), Port(1238)])
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test "single probe negative-progressive":
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let props = getNatProperties(1234'u16, @[1232'u16])
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check(props.natType == Unknown)
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check(props.guess == @[1232'u16, 1230'u16])
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let predicted = predictPortRange(props)
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check(predicted == @[Port(1232), Port(1230)])
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test "all equal":
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let props = getNatProperties(1234'u16, @[1234'u16, 1234'u16])
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check(props.natType == Cone)
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check(props.prediction == 1234'u16)
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let predicted = predictPortRange(props)
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check(predicted == @[Port(1234)])
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test "positive-progressive, offset 1":
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let props = getNatProperties(1234'u16, @[2034'u16, 2035'u16])
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check(props.natType == SymmetricProgressive)
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check(props.order == Ascending)
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check(props.previousPort == 2035'u16)
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check(props.minDistance == 1'u16)
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check(props.maxDistance == 1'u16)
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let predicted = predictPortRange(props)
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check(predicted == @[Port(2036)])
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test "positive-progressive, offset 9":
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let props = getNatProperties(1234'u16, @[2034'u16, 2043'u16])
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check(props.natType == SymmetricProgressive)
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check(props.order == Ascending)
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check(props.previousPort == 2043'u16)
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check(props.minDistance == 9'u16)
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check(props.maxDistance == 9'u16)
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let predicted = predictPortRange(props)
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check(predicted == @[Port(2052)])
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test "negative-progressive, offset 1":
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let props = getNatProperties(1234'u16, @[1100'u16, 1099'u16])
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check(props.natType == SymmetricProgressive)
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check(props.order == Descending)
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check(props.previousPort == 1099'u16)
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check(props.minDistance == 1'u16)
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check(props.maxDistance == 1'u16)
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let predicted = predictPortRange(props)
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check(predicted == @[Port(1098)])
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test "negative-progressive, offset 9":
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let props = getNatProperties(1234'u16, @[1100'u16, 1091'u16])
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check(props.natType == SymmetricProgressive)
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check(props.order == Descending)
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check(props.previousPort == 1091'u16)
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check(props.minDistance == 9'u16)
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check(props.maxDistance == 9'u16)
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let predicted = predictPortRange(props)
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check(predicted == @[Port(1082)])
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test "positive-progressive, 3 probed ports, low offset":
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let props = getNatProperties(1234'u16, @[2000'u16, 2000'u16, 2002'u16])
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check(props.natType == SymmetricProgressive)
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check(props.order == Ascending)
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check(props.previousPort == 2002)
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check(props.minDistance == 0'u16)
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check(props.maxDistance == 2'u16)
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let predicted = predictPortRange(props)
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check(predicted == @[Port(2000), Port(2001), Port(2002)])
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test "negative-progressive, 3 probed ports, low offset":
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let props = getNatProperties(1234'u16, @[2002'u16, 2000'u16, 2000'u16])
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check(props.natType == SymmetricProgressive)
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check(props.order == Descending)
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check(props.previousPort == 2000)
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check(props.minDistance == 0'u16)
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check(props.maxDistance == 2'u16)
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let predicted = predictPortRange(props)
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check(predicted == @[Port(2002), Port(2001), Port(2000)])
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test "high port, positive-progressive, offset 1":
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let props = getNatProperties(1234'u16, @[65534'u16, 65535'u16])
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check(props.natType == SymmetricProgressive)
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check(props.order == Ascending)
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check(props.previousPort == 65535'u16)
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check(props.minDistance == 1'u16)
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check(props.maxDistance == 1'u16)
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let predicted = predictPortRange(props)
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check(predicted == @[Port(1024)])
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test "high port, positive-progressive, offset 9":
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let props = getNatProperties(1234'u16, @[65520'u16, 65529'u16])
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check(props.natType == SymmetricProgressive)
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check(props.order == Ascending)
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check(props.previousPort == 65529'u16)
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check(props.minDistance == 9'u16)
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check(props.maxDistance == 9'u16)
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let predicted = predictPortRange(props)
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check(predicted == @[Port(1026)])
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test "low port, negative-progressive, offset 1":
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let props = getNatProperties(1234'u16, @[1025'u16, 1024'u16])
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check(props.natType == SymmetricProgressive)
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check(props.order == Descending)
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check(props.previousPort == 1024'u16)
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check(props.minDistance == 1'u16)
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check(props.maxDistance == 1'u16)
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let predicted = predictPortRange(props)
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check(predicted == @[Port(65535)])
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test "low port, negative-progressive, offset 9":
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let props = getNatProperties(1234'u16, @[1039'u16, 1030'u16])
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check(props.natType == SymmetricProgressive)
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check(props.order == Descending)
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check(props.previousPort == 1030'u16)
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check(props.minDistance == 9'u16)
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check(props.maxDistance == 9'u16)
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let predicted = predictPortRange(props)
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check(predicted == @[Port(65533)])
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test "random port allocation":
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let props = getNatProperties(1234'u16, @[20000'u16, 24000'u16])
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check(props.natType == SymmetricRandom)
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check(props.minPort == 20000'u16)
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check(props.maxPort == 24000'u16)
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let predicted = predictPortRange(props)
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let half = RandomPortCount div 2'u16
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check(predicted == toSeq(countup(22000'u16 - half, 22000'u16 + half - 1)).map(toPort))
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test "random port allocation":
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let props = getNatProperties(1234'u16, @[1200'u16, 1600'u16])
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check(props.natType == SymmetricRandom)
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check(props.minPort == 1200'u16)
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check(props.maxPort == 1600'u16)
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let predicted = predictPortRange(props)
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check(predicted.len == RandomPortCount.int)
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check(predicted == toSeq(countup(1024'u16, 1024'u16 + RandomPortCount - 1)).map(toPort))
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test "random port allocation, high":
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let props = getNatProperties(1234'u16, @[65000'u16, 65400'u16])
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check(props.natType == SymmetricRandom)
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check(props.minPort == 65000'u16)
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check(props.maxPort == 65400'u16)
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let predicted = predictPortRange(props)
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check(predicted.len == RandomPortCount.int)
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check(predicted == toSeq(countup(uint16.high - RandomPortCount + 1, uint16.high)).map(toPort))
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