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

[Simon Horman <horms@kernel.org>]

On Thu, Nov 16, 2023 at 03:34:43PM -0500, Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@google.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@google.com>

Thanks Willem,

this looks nice and clean to me.

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