On Sat, Apr 02, 2016 at 11:11:52PM -0700, Brenden Blanco wrote:
> On Sat, Apr 02, 2016 at 10:23:31AM +0200, Jesper Dangaard Brouer wrote:
> [...]
> >
> > I think you need to DMA sync RX-page before you can safely access
> > packet data in page (on all arch's).
> >
> Thanks, I will give that a try in the next spin.
> > > + ethh = (struct ethhdr *)(page_address(frags[0].page) +
> > > + frags[0].page_offset);
> > > + if (mlx4_call_bpf(prog, ethh, length)) {
> >
> > AFAIK length here covers all the frags[n].page, thus potentially
> > causing the BPF program to access memory out of bound (crash).
> >
> > Having several page fragments is AFAIK an optimization for jumbo-frames
> > on PowerPC (which is a bit annoying for you use-case ;-)).
> >
> Yeah, this needs some more work. I can think of some options:
> 1. limit pseudo skb.len to first frag's length only, and signal to
> program that the packet is incomplete
> 2. for nfrags>1 skip bpf processing, but this could be functionally
> incorrect for some use cases
> 3. run the program for each frag
> 4. reject ndo_bpf_set when frags are possible (large mtu?)
>
> My preference is to go with 1, thoughts?
hmm and what program will do with 'incomplete' packet?
imo option 4 is only way here. If phys_dev bpf program already
attached to netdev then mlx4_en_change_mtu() can reject jumbo mtus.
My understanding of mlx4_en_calc_rx_buf is that mtu < 1514
will have num_frags==1. That's the common case and one we
want to optimize for.
If later we can find a way to change mlx4 driver to support
phys_dev bpf programs with jumbo mtus, great.
