On 09/03/2013 10:52 PM, Daniel Borkmann wrote:

On 09/03/2013 09:58 PM, Vladimir Murzin wrote:

[...]

quoted

quoted

Do you have a test case/suite by any chance ?

Ben.

Hi Ben!

Thanks for your feedback.

This patch is only compile tested. I have no real hardware, but I'll
probably bring up qemu ppc64 till end of the week...
Meanwhile, I've made simple how-to for testing. You can use it if you wish.
It is mainly based on the [1] and rechecked on x86-64.

Please also cc netdev on BPF related changes.

Actually, your test plan can be further simplified ...

For retrieving and disassembling the JIT image, we have bpf_jit_disasm [1].

  1) echo 2 > /proc/sys/net/core/bpf_jit_enable
  2) ... attach filter ...
  3) bpf_jit_disasm -o

For generating a simple stupid test filter, you can use bpfc [2] (also
see its man page). E.g. ...

   # cat blub
   ldi #10
   mod #8
   ret a
   # bpfc blub
   { 0x0, 0, 0, 0x0000000a },
   { 0x94, 0, 0, 0x00000008 },
   { 0x16, 0, 0, 0x00000000 },

Plus something like ...

ldxi #0
mod x
ret a

For longer-term testing, also trinity has BPF support. ;)

And load this array e.g. either into a small C program that attaches this
as BPF filter, or simply do bpfc blub > blub2 and run netsniff-ng -f blub2\
-s -i eth0, that should also do it.

Then, when attached, the kernel should truncate incoming frames for pf_packet
into max length of 2, just as an example.

   [1] kernel tree, tools/net/bpf_jit_disasm.c
   [2] git clone git://github.com/borkmann/netsniff-ng.git