On Mon, Oct 29, 2018 at 8:08 PM Eric Dumazet <eric.duma...@gmail.com> wrote: > > > > On 10/29/2018 07:41 PM, Cong Wang wrote: > > On Mon, Oct 29, 2018 at 7:25 PM Eric Dumazet <eric.duma...@gmail.com> wrote: > >> > >> > >> > >> On 10/29/2018 07:21 PM, Cong Wang wrote: > >>> On Mon, Oct 29, 2018 at 7:14 PM Eric Dumazet <eric.duma...@gmail.com> > >>> wrote: > >>>> > >>>> Would not it be simpler to set ip_summed to CHECKSUM_NONE (no need to > >>>> save old_csum) ? > >>> > >>> For !CHECKSUM_COMPLETE, ip_summed should be untouched, right? > >>> > >>> If you mean only setting to CHECKSUM_NONE for CHECKSUM_COMPLETE case, > >>> the end result may not be simpler. > >> > >> I meant to reinstate what was there before my patch in this error case > >> > >> if (skb->ip_summed == CHECKSUM_COMPLETE) > >> skb->ip_summed = CHECKSUM_NONE; > >> > >> That would only be run in error (quite unlikely) path, instead of saving > >> old_csum in all cases. > > > > I know your point, however, I am not sure that is a desired behavior. > > > > On failure, I think the whole skb should be restored to its previous state > > before entering this function, changing it to CHECKSUM_NONE on failure > > is inconsistent with success case. > > > > Before my patch, we were changing skb->ip_summed to CHECKSUM_NONE, > so why suddenly we need to be consistent ?
That is because setting it to CHECKSUM_NONE _was_ how the success case works and nothing _was_ needed for failure case. You changed how we handle checksum for success case, it is why we need to change for the failure case too. > > In any case, ip_check_defrag() should really drop this skb, as for other > allocation > failures (like skb_share_check()), if really we want consistency. I have the same feeling, just not brave enough to change the logic of ip_check_defrag() where pskb_may_pull() failure is treated in a same way.
