[Cake] the Cake stalemate

Pete Heist pete at heistp.net
Tue Jun 19 08:26:56 EDT 2018

> On Jun 19, 2018, at 1:54 PM, Toke Høiland-Jørgensen <toke at toke.dk> wrote:
> We also saw a bug on 32-bit MIPS where some combinations of 64-bit
> netlink attributes would cause stats display in tc to fail. However, I
> believe this is more a case of Cake exposing a latent bug somewhere in
> the tc or kernel netlink code (alignment issues, perhaps?), and so I'm
> not sure it is necessarily a blocker for merging Cake. However, if
> someone could take a look that would be very helpful. I forget if the
> current head of the cobalt branch exposes the bug, but I think it does.
> It's quite obvious when it happens: no stats output whatsoever...

I have a 32-bit MIPS in my ER-X, but it sounds like what I saw (outrageous refcnt values) was something different:

qdisc pfifo_fast 0: dev vtun1 root refcnt 23227372115329026 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
 Sent 3696 bytes 44 pkt (dropped 0, overlimits 0 requeues 0) 
 backlog 0b 0p requeues 0
qdisc cake 800a: dev ifb4eth4 root refcnt 23227372115329026 bandwidth 30Mbit diffserv3 dual-dsthost nat ingress split-gso rtt 100.0ms raw overhead 0 
 Sent 41906985 bytes 41340 pkt (dropped 347, overlimits 57700 requeues 0)

This may be related to its old 3.10 kernel though (BTW, looks like Ubiquiti will move to 4.9 soon, alpha is out…).

However, if there’s a way I should try to reproduce something on this hardware to take a look, send any info you’ve got (how to add 64-bit netlink attributes?). I even have a spare ER-X on which I could put OpenWRT in case I need to be working with a more modern kernel…

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