On 06/08/2018 02:27 PM, Daniel Borkmann wrote:
On 06/08/2018 11:00 PM, Tushar Dave wrote:
Today socket filter only deals with linear skbs. This change allows
ebpf programs to look into non-linear skb e.g. skb frags. This will be
useful when users need to look into data which is not contained in the
linear part of skb.
Hmm, I don't think this statement is correct in its form here ... they
can handle non-linear skbs just fine.
Thanks Daniel for your reply.
Straight forward way is to use bpf_skb_load_bytes(). It's simple and uses
internally skb_header_pointer(), and that one of course walks everything
if it really has to via skb_copy_bits() (page frags _and_ frag list). And
if you need to look into mac/net headers that may otherwise not be accessible
anymore from socket layer, there's bpf_skb_load_bytes_relative() helper
which is effectively doing the negative offset trick from ld_abs/ind more
efficient for multi-byte loads.
I'm looking into bpf_skb_load_bytes and friends.
Thanks.
-Tushar
Thanks,
Daniel
