Vitaly Kuznetsov <vkuzn...@redhat.com> writes: > David Vrabel <david.vra...@citrix.com> writes: > >> On 22/08/16 16:42, Vitaly Kuznetsov wrote: >>> >>> I see two ways to fix the issue: >>> - Change the 'wire' protocol between netfront and netback to start keeping >>> the original SKB structure. We'll have to add a flag indicating the fact >>> that the particular request is a part of the original linear part and not >>> a frag. We'll need to know the length of the linear part to pre-allocate >>> memory. >> >> I don't think there needs to be a protocol change. I think the check in >> netback is bogus -- it's the total packet length that must be > >> HLEN_ETH. The upper layers will pull any headers from the frags as >> needed > > I'm afraid this is not always true, just removing the check leads us to > the following: > > [ 495.442186] kernel BUG at ./include/linux/skbuff.h:1927! > [ 495.468789] invalid opcode: 0000 [#1] SMP
What I wanted to say here is that this test makes me think the description of the patch I suggested is correct: an SKB can't have its linear part shorter than ETH_HLEN as the header is being pointed directly, upper network layers don't assemble it from frags, the check in netback is valid. So, how can we proceed here? -- Vitaly
