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. 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. Thanks, Daniel
