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Date: Thu, 5 Mar 2015 11:57:05 +0300
From: Denis Kirjanov <kda@...ux-powerpc.org>
To: Michal Sekletar <msekleta@...hat.com>
Cc: netdev@...r.kernel.org, Alexei Starovoitov <ast@...mgrid.com>,
Jiri Pirko <jpirko@...hat.com>
Subject: Re: [PATCH] filter: introduce SKF_AD_VLAN_PROTO BPF extension
On 3/4/15, Michal Sekletar <msekleta@...hat.com> wrote:
> This commit introduces new BPF extension. It makes possible to load value
> of
> skb->vlan_proto (vlan tpid) to register A.
>
> Currently, vlan header is removed from frame and information is available
> to
> userspace only via tpacket interface. Hence, it is not possible to install
> filter which uses value of vlan tpid field.
>
> AFAICT only way how to filter based on tpid value is to reconstruct
> original
> frame encapsulation and interpret BPF filter code in userspace. Doing that
> is
> way slower than doing filtering in kernel.
>
> Cc: Alexei Starovoitov <ast@...mgrid.com>
> Cc: Jiri Pirko <jpirko@...hat.com>
> Signed-off-by: Michal Sekletar <msekleta@...hat.com>
> ---
> Documentation/networking/filter.txt | 1 +
> arch/arm/net/bpf_jit_32.c | 6 ++++++
> arch/mips/net/bpf_jit.c | 6 ++++++
> arch/powerpc/net/bpf_jit_comp.c | 5 +++++
> arch/s390/net/bpf_jit_comp.c | 5 +++++
> arch/sparc/net/bpf_jit_comp.c | 3 +++
> include/linux/filter.h | 1 +
> include/uapi/linux/filter.h | 3 ++-
> net/core/filter.c | 10 ++++++++++
> tools/net/bpf_exp.l | 1 +
> tools/net/bpf_exp.y | 11 ++++++++++-
> 11 files changed, 50 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/networking/filter.txt
> b/Documentation/networking/filter.txt
> index 9930ecfb..3155c4c 100644
> --- a/Documentation/networking/filter.txt
> +++ b/Documentation/networking/filter.txt
> @@ -282,6 +282,7 @@ Possible BPF extensions are shown in the following
> table:
> vlan_tci skb_vlan_tag_get(skb)
> vlan_pr skb_vlan_tag_present(skb)
> rand prandom_u32()
> + vlan_proto skb->vlan_proto
>
> These extensions can also be prefixed with '#'.
> Examples for low-level BPF:
> diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
> index e1268f9..2954e05 100644
> --- a/arch/arm/net/bpf_jit_32.c
> +++ b/arch/arm/net/bpf_jit_32.c
> @@ -843,6 +843,12 @@ b_epilogue:
> else
> OP_IMM3(ARM_AND, r_A, r_A, VLAN_TAG_PRESENT, ctx);
> break;
> + case BPF_ANC | SKF_AD_VLAN_PROTO:
> + ctx->seen |= SEEN_SKB;
> + BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_proto) != 2);
> + off = offsetof(struct sk_buff, vlan_proto);
> + emit(ARM_LDR_I(r_A, r_skb, off), ctx);
> + break;
> case BPF_ANC | SKF_AD_QUEUE:
> ctx->seen |= SEEN_SKB;
> BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
> diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
> index 5d61393..732fb1d 100644
> --- a/arch/mips/net/bpf_jit.c
> +++ b/arch/mips/net/bpf_jit.c
> @@ -1295,6 +1295,12 @@ jmp_cmp:
> emit_sltu(r_A, r_zero, r_A, ctx);
> }
> break;
> + case BPF_ANC | SKF_AD_VLAN_PROTO:
> + ctx->flags |= SEEN_SKB | SEEN_A;
> + BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_proto) != 2);
> + off = offsetof(struct sk_buff, vlan_proto);
> + emit_load(r_A, r_skb, off, ctx);
> + break;
> case BPF_ANC | SKF_AD_PKTTYPE:
> ctx->flags |= SEEN_SKB;
>
> diff --git a/arch/powerpc/net/bpf_jit_comp.c
> b/arch/powerpc/net/bpf_jit_comp.c
> index 17cea18..acfa732 100644
> --- a/arch/powerpc/net/bpf_jit_comp.c
> +++ b/arch/powerpc/net/bpf_jit_comp.c
> @@ -399,6 +399,11 @@ static int bpf_jit_build_body(struct bpf_prog *fp, u32
> *image,
> PPC_SRWI(r_A, r_A, 12);
> }
> break;
> + case BPF_ANC | SKF_AD_VLAN_PROTO:
> + BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_proto) != 2);
> + PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
> + vlan_proto));
You're going to load a halfword, so lhz has to be used
> + break;
> case BPF_ANC | SKF_AD_QUEUE:
> BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
> queue_mapping) != 2);
> diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
> index bbd1981..55b6db7 100644
> --- a/arch/s390/net/bpf_jit_comp.c
> +++ b/arch/s390/net/bpf_jit_comp.c
> @@ -722,6 +722,11 @@ call_fn: /* lg %r1,<d(function)>(%r13) */
> EMIT4_DISP(0x88500000, 12);
> }
> break;
> + case BPF_ANC | SKF_AD_VLAN_PROTO: /* A = skb->vlan_proto */
> + BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_proto) != 2);
> + /* l %r5,<d(vlan_proto)>(%r2) */
> + EMIT4_DISP(0x58502000, offsetof(struct sk_buff, vlan_proto));
> + break;
> case BPF_ANC | SKF_AD_PKTTYPE:
> /* lhi %r5,0 */
> EMIT4(0xa7580000);
> diff --git a/arch/sparc/net/bpf_jit_comp.c b/arch/sparc/net/bpf_jit_comp.c
> index 7931eee..cf3e6ac 100644
> --- a/arch/sparc/net/bpf_jit_comp.c
> +++ b/arch/sparc/net/bpf_jit_comp.c
> @@ -624,6 +624,9 @@ void bpf_jit_compile(struct bpf_prog *fp)
> emit_and(r_A, r_TMP, r_A);
> }
> break;
> + case BPF_ANC | SKF_AD_VLAN_PROTO:
> + emit_skb_load32(vlan_proto, r_A);
> + break;
> case BPF_LD | BPF_W | BPF_LEN:
> emit_skb_load32(len, r_A);
> break;
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index 9ee8c67..3ec42a1 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -454,6 +454,7 @@ static inline u16 bpf_anc_helper(const struct
> sock_filter *ftest)
> BPF_ANCILLARY(VLAN_TAG_PRESENT);
> BPF_ANCILLARY(PAY_OFFSET);
> BPF_ANCILLARY(RANDOM);
> + BPF_ANCILLARY(VLAN_PROTO);
> }
> /* Fallthrough. */
> default:
> diff --git a/include/uapi/linux/filter.h b/include/uapi/linux/filter.h
> index 47785d5..aef103bf 100644
> --- a/include/uapi/linux/filter.h
> +++ b/include/uapi/linux/filter.h
> @@ -77,7 +77,8 @@ struct sock_fprog { /* Required for SO_ATTACH_FILTER. */
> #define SKF_AD_VLAN_TAG_PRESENT 48
> #define SKF_AD_PAY_OFFSET 52
> #define SKF_AD_RANDOM 56
> -#define SKF_AD_MAX 60
> +#define SKF_AD_VLAN_PROTO 60
> +#define SKF_AD_MAX 64
> #define SKF_NET_OFF (-0x100000)
> #define SKF_LL_OFF (-0x200000)
>
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 7a4eb70..b14cc40 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -236,6 +236,16 @@ static bool convert_bpf_extensions(struct sock_filter
> *fp,
> }
> break;
>
> + case SKF_AD_OFF + SKF_AD_VLAN_PROTO:
> + BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_proto) != 2);
> +
> + /* A = *(u16 *) (CTX + offsetof(vlan_proto)) */
> + *insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
> + offsetof(struct sk_buff, vlan_proto));
> + /* A = ntohs(A) [emitting a nop or swap16] */
> + *insn = BPF_ENDIAN(BPF_FROM_BE, BPF_REG_A, 16);
> + break;
> +
> case SKF_AD_OFF + SKF_AD_PAY_OFFSET:
> case SKF_AD_OFF + SKF_AD_NLATTR:
> case SKF_AD_OFF + SKF_AD_NLATTR_NEST:
> diff --git a/tools/net/bpf_exp.l b/tools/net/bpf_exp.l
> index 833a966..0d4e72f 100644
> --- a/tools/net/bpf_exp.l
> +++ b/tools/net/bpf_exp.l
> @@ -93,6 +93,7 @@ extern void yyerror(const char *str);
> "#"?("vlan_tci") { return K_VLANT; }
> "#"?("vlan_pr") { return K_VLANP; }
> "#"?("rand") { return K_RAND; }
> +"#"?("vlan_proto") { return K_VLANPR; }
>
> ":" { return ':'; }
> "," { return ','; }
> diff --git a/tools/net/bpf_exp.y b/tools/net/bpf_exp.y
> index e6306c5..9c7a0e7 100644
> --- a/tools/net/bpf_exp.y
> +++ b/tools/net/bpf_exp.y
> @@ -56,7 +56,7 @@ static void bpf_set_jmp_label(char *label, enum jmp_type
> type);
> %token OP_LDXI
>
> %token K_PKT_LEN K_PROTO K_TYPE K_NLATTR K_NLATTR_NEST K_MARK K_QUEUE
> K_HATYPE
> -%token K_RXHASH K_CPU K_IFIDX K_VLANT K_VLANP K_POFF K_RAND
> +%token K_RXHASH K_CPU K_IFIDX K_VLANT K_VLANP K_POFF K_RAND K_VLANPR
>
> %token ':' ',' '[' ']' '(' ')' 'x' 'a' '+' 'M' '*' '&' '#' '%'
>
> @@ -167,6 +167,9 @@ ldb
> | OP_LDB K_RAND {
> bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
> SKF_AD_OFF + SKF_AD_RANDOM); }
> + | OP_LDB K_VLANPR {
> + bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
> + SKF_AD_OFF + SKF_AD_VLAN_PROTO); }
> ;
>
> ldh
> @@ -218,6 +221,9 @@ ldh
> | OP_LDH K_RAND {
> bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
> SKF_AD_OFF + SKF_AD_RANDOM); }
> + | OP_LDH K_VLANPR {
> + bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
> + SKF_AD_OFF + SKF_AD_VLAN_PROTO); }
> ;
>
> ldi
> @@ -274,6 +280,9 @@ ld
> | OP_LD K_RAND {
> bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
> SKF_AD_OFF + SKF_AD_RANDOM); }
> + | OP_LD K_VLANPR {
> + bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
> + SKF_AD_OFF + SKF_AD_VLAN_PROTO); }
> | OP_LD 'M' '[' number ']' {
> bpf_set_curr_instr(BPF_LD | BPF_MEM, 0, 0, $4); }
> | OP_LD '[' 'x' '+' number ']' {
> --
> 1.8.3.1
>
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