netdev - Re: [net-next PATCH 3/5] bpf: cpumap xdp_buff to skb conversion and allocation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 29 Sep 2017 17:49:23 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org
Cc:     jakub.kicinski@...ronome.com,
        "Michael S. Tsirkin" <mst@...hat.com>, mchan@...adcom.com,
        John Fastabend <john.fastabend@...il.com>,
        peter.waskiewicz.jr@...el.com,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>
Subject: Re: [net-next PATCH 3/5] bpf: cpumap xdp_buff to skb conversion and
 allocation



On 2017年09月28日 20:57, Jesper Dangaard Brouer wrote:
> +};
> +
> +/* Convert xdp_buff to xdp_pkt */
> +static struct xdp_pkt *convert_to_xdp_pkt(struct xdp_buff *xdp)
> +{
> +	struct xdp_pkt *xdp_pkt;
> +	int headroom;
> +
> +	/* Assure headroom is available for storing info */
> +	headroom = xdp->data - xdp->data_hard_start;
> +	if (headroom < sizeof(*xdp_pkt))
> +		return NULL;

Hi Jesper:

Do you consider this as a trick or a long term solution? Is it better to 
store XDP in a circular buffer? (I'm asking since I meet similar issue 
when doing xdp_xmit for tun).

> +
> +	/* Store info in top of packet */
> +	xdp_pkt = xdp->data_hard_start;
> +
> +	xdp_pkt->data = xdp->data;
> +	xdp_pkt->len  = xdp->data_end - xdp->data;
> +	xdp_pkt->headroom = headroom - sizeof(*xdp_pkt);
> +

Is wmb() needed here?

> +	return xdp_pkt;
> +}

Thanks