Here's a patch to libpcap-1.3 to test against. I still need to
include changes to man pages.
g
On Sat, 08 Sep 2012 10:03:35 +0200
Eric Dumazet wrote:
> From: Eric Dumazet
>
> On Fri, 2012-09-07 at 20:03 -0700, Andi Kleen wrote:
> > On Fri, Sep 07, 2012 at 07:49:10AM +, George Bakos wrote:
> > > Gents,
> > > Any fundamental reason why the following (, etc.) shouldn't be
> > > included in net/core/filter.c?
> > >
> > > case BPF_S_ALU_MOD_X:
> > > if (X == 0)
> > > return 0;
> > > A %= X;
> > > continue;
> >
> > Copying netdev.
> >
> > In principle no reason against it, but you may need to update
> > the various BPF JITs too that Linux now has too.
>
> Hi Andi, thanks for the forward
>
> In recent commit ffe06c17afbb was added ALU_XOR_X,
> so we could add ALU_MOD_X as well.
>
> ALU_MOD_K is a bit more complex as we cant use an ancillary, and must
> instead use a new BPF_OP code :
>
> /* alu/jmp fields */
> #define BPF_OP(code)((code) & 0xf0)
> #define BPF_ADD 0x00
> #define BPF_SUB 0x10
> #define BPF_MUL 0x20
> #define BPF_DIV 0x30
> #define BPF_OR 0x40
> #define BPF_AND 0x50
> #define BPF_LSH 0x60
> #define BPF_RSH 0x70
> #define BPF_NEG 0x80
>
> So I guess we could use
>
> #define BPF_MOD 0x90
>
> About the various arches JIT, there is no hurry :
> We can update them later.
>
> At JIT 'compile' time, if we find a not yet handled instruction, we fall
> back to the net/core/filter.c interpreter.
>
> If the following patch is accepted, I'll do the x86 part as a followup.
>
> Thanks !
>
> [PATCH net-next] filter: add MOD operation
>
> Add a new ALU opcode, to compute a modulus.
>
> Commit ffe06c17afbbb used an ancillary to implement XOR_X,
> but here we reserve one of the available ALU opcode to implement both
> MOD_X and MOD_K
>
> Signed-off-by: Eric Dumazet
> Suggested-by: George Bakos
> Cc: Jay Schulist
> Cc: Jiri Pirko
> Cc: Andi Kleen
> ---
> include/linux/filter.h |4
> net/core/filter.c | 15 +++
> 2 files changed, 19 insertions(+)
>
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index 82b0135..3cf5fd5 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -74,6 +74,8 @@ struct sock_fprog { /* Required for SO_ATTACH_FILTER. */
> #define BPF_LSH 0x60
> #define BPF_RSH 0x70
> #define BPF_NEG 0x80
> +#define BPF_MOD 0x90
> +
> #define BPF_JA 0x00
> #define BPF_JEQ 0x10
> #define BPF_JGT 0x20
> @@ -196,6 +198,8 @@ enum {
> BPF_S_ALU_MUL_K,
> BPF_S_ALU_MUL_X,
> BPF_S_ALU_DIV_X,
> + BPF_S_ALU_MOD_K,
> + BPF_S_ALU_MOD_X,
> BPF_S_ALU_AND_K,
> BPF_S_ALU_AND_X,
> BPF_S_ALU_OR_K,
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 907efd2..fbe3a8d 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -167,6 +167,14 @@ unsigned int sk_run_filter(const struct sk_buff *skb,
> case BPF_S_ALU_DIV_K:
> A = reciprocal_divide(A, K);
> continue;
> + case BPF_S_ALU_MOD_X:
> + if (X == 0)
> + return 0;
> + A %= X;
> + continue;
> + case BPF_S_ALU_MOD_K:
> + A %= K;
> + continue;
> case BPF_S_ALU_AND_X:
> A &= X;
> continue;
> @@ -469,6 +477,8 @@ int sk_chk_filter(struct sock_filter *filter, unsigned
> int flen)
> [BPF_ALU|BPF_MUL|BPF_K] = BPF_S_ALU_MUL_K,
> [BPF_ALU|BPF_MUL|BPF_X] = BPF_S_ALU_MUL_X,
> [BPF_ALU|BPF_DIV|BPF_X] = BPF_S_ALU_DIV_X,
> + [BPF_ALU|BPF_MOD|BPF_K] = BPF_S_ALU_MOD_K,
> + [BPF_ALU|BPF_MOD|BPF_X] = BPF_S_ALU_MOD_X,
> [BPF_ALU|BPF_AND|BPF_K] = BPF_S_ALU_AND_K,
> [BPF_ALU|BPF_AND|BPF_X] = BPF_S_ALU_AND_X,
> [BPF_ALU|BPF_OR|BPF_K] = BPF_S_ALU_OR_K,
> @@ -531,6 +541,11 @@ int sk_chk_filter(struct sock_filter *filter, unsigned
> int flen)
> return -EINVAL;
>
