[Cake] best way at getting at tcp ack data?

Dave Taht dave.taht at gmail.com
Sat Sep 30 23:10:43 EDT 2017

I was thinking about how I'd go about adding saner ack filtering [1]
to cake (or maybe to a tc filter), and perhaps it is way simple, now.

Merely using the skb_flow_dissect stuff gives me all the flow related
fields, from potentially deeply encapsulated packets - and seems to
have grown FLOW_DISSECTOR_KEY_TCP at some point since I last looked.

Seems promising. Not sure how to get at it in the context of cake?


The infamous wondershaper filter looks like this:

tc filter add dev $DEV parent 1: protocol ip prio 12 u32 \
   match ip protocol 6 0xff \
   match u8 0x05 0x0f at 0 \
   match u16 0x0000 0xffc0 at 2 \
   match u8 0x10 0xff at 33 \
   flowid 1:10

And that filter is wrong for encapsulated traffic, and ipv6.

[1] https://tools.ietf.org/html/rfc3449


Dave Täht
CEO, TekLibre, LLC
Tel: 1-669-226-2619

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