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Treat packet according to its size #70

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mpastor opened this issue Apr 3, 2020 · 1 comment
Open

Treat packet according to its size #70

mpastor opened this issue Apr 3, 2020 · 1 comment
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@rmind
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@mpastor
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mpastor commented Apr 3, 2020

Hi, is it possible to pass/block packet according to its size? I need to block outgoing UDP/123 (NTP) packets bigger than 128B to disable DDoS amplification. There is nothing about it in doc.
Thanks.
@rmind rmind self-assigned this Apr 8, 2020
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rmind commented Apr 29, 2020

@mpastor: NPF already supports this using the pcap-filter i.e. the tcpdump syntax, e.g.:

block in final pcap-filter "greater 128"

See npf.conf(5) and pcap-filter(7) man pages. However, I think I will add more options to filter based on some IP header values using the native syntax.

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@mpastor @rmind