On Mon, 1 Jun 2020, Daniel Borkmann wrote: > On 6/1/20 7:48 PM, Alan Maguire wrote: > > On Wed, 13 May 2020, Lorenz Bauer wrote: > > > >>>> Option 1: always downgrade UNNECESSARY to NONE > >>>> - Easiest to back port > >>>> - The helper is safe by default > >>>> - Performance impact unclear > >>>> - No escape hatch for Cilium > >>>> > >>>> Option 2: add a flag to force CHECKSUM_NONE > >>>> - New UAPI, can this be backported? > >>>> - The helper isn't safe by default, needs documentation > >>>> - Escape hatch for Cilium > >>>> > >>>> Option 3: downgrade to CHECKSUM_NONE, add flag to skip this > >>>> - New UAPI, can this be backported? > >>>> - The helper is safe by default > >>>> - Escape hatch for Cilium (though you'd need to detect availability of > >>>> the > >>>> flag somehow) > >>> > >>> This seems most reasonable to me; I can try and cook a proposal for > >>> tomorrow as > >>> potential fix. Even if we add a flag, this is still backportable to stable > >>> (as > >>> long as the overall patch doesn't get too complex and the backport itself > >>> stays > >>> compatible uapi-wise to latest kernels. We've done that before.). I happen > >>> to > >>> have two ixgbe NICs on some of my test machines which seem to be setting > >>> the > >>> CHECKSUM_UNNECESSARY, so I'll run some experiments from over here as well. > >> > >> Great! I'm happy to test, of course. > > > > I had a go at implementing option 3 as a few colleagues ran into this > > problem. They confirmed the fix below resolved the issue. Daniel is > > this roughly what you had in mind? I can submit a patch for the bpf > > tree if that's acceptable with the new flag. Do we need a few > > tests though? > > Coded this [0] up last week which Lorenz gave a spin as well. Originally > wanted to > get it out Friday night, but due to internal release stuff it got too late Fri > night > and didn't want to rush it at 3am anymore, so the series as fixes is going out > tomorrow > morning [today was public holiday in CH over here]. > Looks great! Although I've only seen this issue arise for cases where csum_level == 0, should we also add "skb->csum_level = 0;" when we reset the ip_summed value? Feel free to add a Reviewed-by: Alan Maguire <alan.maguire@xxxxxxxxxx> ...for the series if needed. Thanks again! Alan > Thanks, > Daniel > > [0] > https://git.kernel.org/pub/scm/linux/kernel/git/dborkman/bpf.git/log/?h=pr/adjust-csum > >
