netdev - Re: [PATCH net-next] selftests: net: verify fq per-band packet limit

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Date: Mon, 20 Nov 2023 08:42:05 +0000
From: Simon Horman <horms@...nel.org>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
	edumazet@...gle.com, pabeni@...hat.com,
	linux-kselftest@...r.kernel.org,
	Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net-next] selftests: net: verify fq per-band packet limit

On Thu, Nov 16, 2023 at 03:34:43PM -0500, Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@...gle.com>
> 
> Commit 29f834aa326e ("net_sched: sch_fq: add 3 bands and WRR
> scheduling") introduces multiple traffic bands, and per-band maximum
> packet count.
> 
> Per-band limits ensures that packets in one class cannot fill the
> entire qdisc and so cause DoS to the traffic in the other classes.
> 
> Verify this behavior:
>   1. set the limit to 10 per band
>   2. send 20 pkts on band A: verify that 10 are queued, 10 dropped
>   3. send 20 pkts on band A: verify that  0 are queued, 20 dropped
>   4. send 20 pkts on band B: verify that 10 are queued, 10 dropped
> 
> Packets must remain queued for a period to trigger this behavior.
> Use SO_TXTIME to store packets for 100 msec.
> 
> The test reuses existing upstream test infra. The script is a fork of
> cmsg_time.sh. The scripts call cmsg_sender.
> 
> The test extends cmsg_sender with two arguments:
> 
> * '-P' SO_PRIORITY
>   There is a subtle difference between IPv4 and IPv6 stack behavior:
>   PF_INET/IP_TOS        sets IP header bits and sk_priority
>   PF_INET6/IPV6_TCLASS  sets IP header bits BUT NOT sk_priority
> 
> * '-n' num pkts
>   Send multiple packets in quick succession.
>   I first attempted a for loop in the script, but this is too slow in
>   virtualized environments, causing flakiness as the 100ms timeout is
>   reached and packets are dequeued.
> 
> Also do not wait for timestamps to be queued unless timestamps are
> requested.
> 
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>

Thanks Willem,

this looks nice and clean to me.

Reviewed-by: Simon Horman <horms@...nel.org>