netdev - Re: [PATCH net-next 1/2] net: Export skb_zerocopy() to zerocopy from one skb to another

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, 24 May 2013 17:01:06 +0100
From:	Thomas Graf <tgraf@...g.ch>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org, jesse@...ira.com, dev@...nvswitch.org
Subject: Re: [PATCH net-next 1/2] net: Export skb_zerocopy() to zerocopy from
 one skb to another

On 05/24/13 at 08:31am, Eric Dumazet wrote:
> Hmm. Big warning here : In the nfnetlink case, we specifically made sure
> that this path was taken only if skb->head_frag was set (all incoming
> packets have this property, but not outgoing ones yet)
> 
> This should be documented if we move it to net/core/skbuff.c, or we
> should add a BUG_ON()

Good point.

I guess we could ensure in skb_zerocopy() that if !head_frag then we
enforce hlen = max(hlen, skb_headlen(skb)) to always fall back to
skb_copy_bits() for !head_frag.

> I see your openvswitch code seems OK.
> 
> Maybe also put in net/core/skbuff.c the code dealing with  this stuff ?
> 
> +       if (!skb->head_frag ||
> +           skb_headlen(skb) < L1_CACHE_BYTES ||
> +           skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS)
> +               hlen = skb_headlen(skb);
> +
> +       if (skb_has_frag_list(skb))
> +               hlen = skb->len;

I'll put this into skb_zerocopy_hdrlen()
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html