On Thu, 2017-01-26 at 05:44 -0800, Eric Dumazet wrote: > On Thu, 2017-01-26 at 14:27 +0100, Johannes Berg wrote: > > Hi, > > > > It looks like right now we may have a hardware bug and accept > > 0x0000 as > > valid, when the outcome of the calculation is 0xffff. > > > > What do you think we should do about this? > > > > We could ignore the issue entirely, since 0 wasn't ever supposed to > > be > > sent anyway - but then we don't drop frames that we should drop. I > > didn't manage to find the code in the IPv6/UDP stack that even does > > that, but I assume it's there somewhere. > > > > Alternatively, we could parse the packet to find the checksum > > inside, > > and if it's 0 then don't report CHECKSUM_UNNECESSARY, but that > > seems > > rather expensive/difficult due to the IPv6 variable header and all > > that. If we wanted to go this route, are there any helper functions > > for > > this? > > > > Unfortunately, in the current devices, we neither have a complete > > indication that the packet was even UDP-IPv6, nor do we have the > > raw > > csum or anything like that. I think they're adding that to the next > > hardware spin, but we probably need to address this issue now. > Is this a xmit or rcv problem ? Oops, sorry - receive. We can only indicate "CHECKSUM_UNNECESSARY", nothing more advanced right now, but right now we'd indicate that if the packet had 0x0000 in the checksum field, but should've had 0xffff. On TX I believe we actually do in HW exactly what your patch just did. johannes
