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BEP 29: packets with unrecognized IDs #83

povilasb opened this Issue May 4, 2018 · 4 comments


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povilasb commented May 4, 2018 doesn't specify how one should handle packets whose connection ID is not known for us.
For example,

  1. we receive Fin(connection_id=1234) packet.
  2. We have never sent or received Syn(connection_id=1234)
  3. What do we do with the packet?
  • ignore it?
  • send Reset packet back?

Thanks :)


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ssiloti commented May 4, 2018

In theory a reset packet should be sent in response to a packet with an unknown connection ID, but libtorrent at least ignores such packets. I assume this was done to avoid amplification attacks.


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the8472 commented May 5, 2018

RST packets should be small, so there shouldn't be any amplification as long as you verify that you're responding to something that has the minimum plausible packet size and rate-limit them. Sure, there's reflections, but those are unavoidable and you get them with TCP or properly-crafted requests too.


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arvidn commented May 20, 2018

as a separate note, you shouldn't send an RST back to an unrecognised RST packet.


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povilasb commented May 21, 2018

Okey dokes, thanks guys, before closing this issue I'll try to do a PR for BEP 29 that specifies this behavior when I'm done with my work on uTP - that might take about 2 weeks though :)

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