Eelco Chaudron wrote: > > > On 23 Jun 2021, at 1:49, John Fastabend wrote: > > > Lorenzo Bianconi wrote: > >> From: Eelco Chaudron <echaudro@xxxxxxxxxx> > >> > >> This patch adds support for multi-buffer for the following helpers: > >> - bpf_xdp_output() > >> - bpf_perf_event_output() > >> > >> Signed-off-by: Eelco Chaudron <echaudro@xxxxxxxxxx> > >> Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx> > >> --- > > > > Ah ok so at least xdp_output will work with all bytes. But this is > > getting close to having access into the frags so I think doing > > the last bit shouldn't be too hard? > > > Guess you are talking about multi-buffer access in the XDP program? > > I did suggest an API a while back, https://lore.kernel.org/bpf/FD3E6E08-DE78-4FBA-96F6-646C93E88631@xxxxxxxxxx/ but I had/have not time to work on it. Guess the difficult part is to convince the verifier to allow the data to be accessed. Ah great I think we had the same idea I called it xdp_pull_data() though. Whats the complication though it looks like it can be done by simply moving the data and data_end pointers around then marking them invalidated. This way the verifier knows the program needs to rewrite them. I can probably look more into next week. >From my first glance it looks relatively straight forward to do now. I really would like to avoid yet another iteration of programs features I have to discover and somehow work around if we can get the helper into this series. If you really don't have time I can probably take a look early next week on an RFC for something like above helper. .John
