Hi Guy Harris,
Here is the translated code.
/*initialization*/
static u_int off_didx = 5;
bpf_u_int32 didx_mask = 0x0ffc0000;
didx = didx<<18;
b0 = gen_ncmp(OR_MACPL, off_didx, BPF_W, didx_mask, BPF_JEQ, 0,
(bpf_int32)didx);
the i/p value of didx is 0x40.
here is what 'gen_ncmp' generates:
gen_load_a(offrel, offset, size); ==> { 0x20, 0, 0, 0x00000013 }
load one word at offset 0x13 into accumulator(A)
new_stmt(BPF_ALU|BPF_AND|BPF_K); ===> { 0x54, 0, 0, 0x0ffc0000 }
AND the mask entered with the value in A.
new_block(JMP(jtype)); ===> { 0x15, 0, 1,0x01000000 } a jump
statement to compare value in didx with value in A.
Thanks and Regards,
Aparna
On 6 November 2014 13:04, Guy Harris <g...@alum.mit.edu> wrote:
>
> On Nov 5, 2014, at 10:41 PM, Aparna Nagarajan <aparna.nagaraja...@gmail.com>
> wrote:
>
>>>
>>> Hi All,
>>>
>>> I am trying to add some BPF code for capture filters.
>>>
>>> I am basically trying to load data into accumilator from some offset,
>>> Mask it and them match it with some value.
>>>
>>> Here is the OPcode:
>>>
>>> { 0x20, 0, 0, 0x00000013 }, { 0x54, 0, 0, 0x0ffc0000 }, { 0x15, 0, 1,
>>> 0x01000000 }, { 0x6, 0, 0, 0x0000ffff }, { 0x6, 0, 0, 0x00000000 },
>
> Please translate that to BPF assembler language; I'm too busy to translate it
> myself.
>
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