On 05/04/2018 11:30 AM, Alexander Duyck wrote: > From: Alexander Duyck <alexander.h.du...@intel.com> > > This patch is meant to allow us to avoid having to recompute the checksum > from scratch and have it passed as a parameter. > > Instead of taking that approach we can take advantage of the fact that the > length that was used to compute the existing checksum is included in the > UDP header. If we cancel that out by adding the value XOR with 0xFFFF we > can then just add the new length in and fold that into the new result. >
> > + uh = udp_hdr(segs); > + > + /* compute checksum adjustment based on old length versus new */ > + newlen = htons(sizeof(*uh) + mss); > + check = ~csum_fold((__force __wsum)((__force u32)uh->check + > + ((__force u32)uh->len ^ 0xFFFF) + > + (__force u32)newlen)); > + Can't this use csum_sub() instead of this ^ 0xFFFF trick ?
