Re: A couple of questions about the SKB fragments

On 05/05/16 08:40, Ilya Matveychikov wrote:

Hello folks,

While working with fragmented SKBs we've got stuck with the following:
- is it possible for an SKB fragment in skb_shinfo(skb)->frag_list to
be fragmented too (i.e. to have SKBs in frag_list)?
- do skb->len and skb->data_len contain the whole SKB length,
including the length of all fragments (not only the paged parts)?

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.

-Ed