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Date: Thu, 5 Mar 2015 15:33:20 +0100
From: Michal Sekletar <msekleta@...hat.com>
To: Denis Kirjanov <kda@...ux-powerpc.org>
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 Thu, Mar 05, 2015 at 11:57:05AM +0300, Denis Kirjanov wrote:
> 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
I treated skb->vlan_proto as word instead of halfword on other arches
too. I fixed them all now, but I will not send out v2 just yet. First, I'd like
to hear back from Alexei.
>
> > + 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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> >
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