netdev - Re: A couple of questions about the SKB fragments

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Message-ID: <CAKh5naYgXko0NBefiNXio7_oPQmmuEtSw4BXCZFMmjshFriYMA@mail.gmail.com>
Date:	Sat, 7 May 2016 12:21:01 +0300
From:	Ilya Matveychikov <matvejchikov@...il.com>
To:	Edward Cree <ecree@...arflare.com>
Cc:	netdev@...r.kernel.org, Aleksey.Baulin@...il.com
Subject: Re: A couple of questions about the SKB fragments

2016-05-05 14:13 GMT+03:00 Edward Cree <ecree@...arflare.com>:
> On 05/05/16 08:40, Ilya Matveychikov wrote:
> > Is there any docs except the kernel sources itself to refer to?

> davem has some docs up at http://vger.kernel.org/~davem/skb.html and
> http://vger.kernel.org/~davem/skb_data.html
> In particular note the following:
> "The frag_list is used to maintain a chain of SKBs organized for
>  fragmentation purposes, it is _not_ used for maintaining paged data."
> So my reading would suggest there is no way to multiple-layer-fragment
> an SKB; the frags are page pointers and offsets, not entire sk_buff
> structs in their own right.
>

Seems that the docs is slightly outdated. I think the structure of SKB does
not impose any restrictions on the nesting of the fragments. But is there
any of them in the kernel's code?