netdev - Re: [PATCH] net: sched: tbf: handle GSO_BY

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Message-ID: <20180215132900.GB4716@localhost.localdomain>
Date:   Thu, 15 Feb 2018 11:29:00 -0200
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Daniel Axtens <dja@...ens.net>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH] net: sched: tbf: handle GSO_BY_FRAGS case in enqueue

On Mon, Feb 05, 2018 at 02:34:33PM +1100, Daniel Axtens wrote:
> tbf_enqueue() checks the size of a packet before enqueuing it.
> However, the GSO size check does not consider the GSO_BY_FRAGS
> case, and so will drop GSO SCTP packets, causing a massive drop
> in throughput.
> 
> Use skb_gso_validate_mac_len() instead, as it does consider that
> case.
> 
> ---
> 
> skb_gso_validate_mac_len() is an out-of-line call, but so is
> skb_gso_mac_seglen(), so this is slower but not much slower. I
> will send a patch to make the skb_gso_validate_* functions
> inline-able shortly.
> 
> Also, GSO_BY_FRAGS considered harmful - I'm pretty sure this is
> not the only place it causes issues.

Thanks for spotting these issues and fixing them.

> 
> Signed-off-by: Daniel Axtens <dja@...ens.net>

If this block was meant to be an out-of-band/changelog comment, your
SOB line should be above the first --- marker.
Anyhow,
Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>

> ---
>  net/sched/sch_tbf.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
> index 229172d509cc..03225a8df973 100644
> --- a/net/sched/sch_tbf.c
> +++ b/net/sched/sch_tbf.c
> @@ -188,7 +188,8 @@ static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch,
>  	int ret;
>  
>  	if (qdisc_pkt_len(skb) > q->max_size) {
> -		if (skb_is_gso(skb) && skb_gso_mac_seglen(skb) <= q->max_size)
> +		if (skb_is_gso(skb) &&
> +		    skb_gso_validate_mac_len(skb, q->max_size))
>  			return tbf_segment(skb, sch, to_free);
>  		return qdisc_drop(skb, sch, to_free);
>  	}
> -- 
> 2.14.1
>