From: Johannes Berg <johannes@xxxxxxxxxxxxxxxx> Date: Thu, 13 Apr 2017 08:10:56 +0200 > On Wed, 2017-04-12 at 21:20 -0700, Alexei Starovoitov wrote: > >> > + if (skb_linearize(skb)) >> > + goto do_drop; >> >> when we discussed supporting jumbo frames in XDP, the idea >> was that the program would need to look at first 3+k bytes only >> and the rest of the packet will be in non-contiguous pages. >> If we do that, it means that XDP program would have to assume >> that the packet is more than [data, data_end] and this range >> only covers linear part. >> If that's the future, we don't need to linearize the skb here >> and can let the program access headlen only. > > I'm not sure how you think that would work - at least with our (wifi) > driver, the headlen should be maybe ETH_HLEN or so at this point. We'd > let the program know that it can only look at so much, but then the > program can't do anything at all with those frames. At some point then > we go back to bpf_skb_load_bytes() being necessary in one form or > another, no? Agreed, this is completely unusable. Some wired ethernet drivers do the same exact thing.
|