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Date: Tue, 15 Apr 2014 11:16:56 -0700
From: Chema Gonzalez <chema@...gle.com>
To: David Miller <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Daniel Borkmann <dborkman@...hat.com>,
Alexei Starovoitov <ast@...mgrid.com>
Cc: netdev@...r.kernel.org, Chema Gonzalez <chema@...gle.com>
Subject: [PATCH] filter: added BPF random opcode
This should allow random packet sampling.
Signed-off-by: Chema Gonzalez <chema@...gle.com>
---
Documentation/networking/filter.txt | 13 +++++++++++++
include/linux/filter.h | 1 +
include/uapi/linux/filter.h | 3 ++-
net/core/filter.c | 12 ++++++++++++
tools/net/bpf_exp.l | 1 +
tools/net/bpf_exp.y | 11 ++++++++++-
6 files changed, 39 insertions(+), 2 deletions(-)
diff --git a/Documentation/networking/filter.txt b/Documentation/networking/filter.txt
index 81f940f..82e1cb0 100644
--- a/Documentation/networking/filter.txt
+++ b/Documentation/networking/filter.txt
@@ -281,6 +281,7 @@ Possible BPF extensions are shown in the following table:
cpu raw_smp_processor_id()
vlan_tci vlan_tx_tag_get(skb)
vlan_pr vlan_tx_tag_present(skb)
+ rand prandom_u32()
These extensions can also be prefixed with '#'.
Examples for low-level BPF:
@@ -308,6 +309,18 @@ Examples for low-level BPF:
ret #-1
drop: ret #0
+** icmp random packet sampling, 1 in 4
+ ldh [12]
+ jne #0x800, drop
+ ldb [23]
+ jneq #1, drop
+ # get a random uint32 number
+ ld rand
+ mod #4
+ jneq #1, drop
+ ret #-1
+ drop: ret #0
+
** SECCOMP filter example:
ld [4] /* offsetof(struct seccomp_data, arch) */
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 262dcbb..49c28aa 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -224,6 +224,7 @@ enum {
BPF_S_ANC_VLAN_TAG,
BPF_S_ANC_VLAN_TAG_PRESENT,
BPF_S_ANC_PAY_OFFSET,
+ BPF_S_ANC_RANDOM,
};
#endif /* __LINUX_FILTER_H__ */
diff --git a/include/uapi/linux/filter.h b/include/uapi/linux/filter.h
index 8eb9cca..253b4d4 100644
--- a/include/uapi/linux/filter.h
+++ b/include/uapi/linux/filter.h
@@ -130,7 +130,8 @@ struct sock_fprog { /* Required for SO_ATTACH_FILTER. */
#define SKF_AD_VLAN_TAG 44
#define SKF_AD_VLAN_TAG_PRESENT 48
#define SKF_AD_PAY_OFFSET 52
-#define SKF_AD_MAX 56
+#define SKF_AD_RANDOM 56
+#define SKF_AD_MAX 60
#define SKF_NET_OFF (-0x100000)
#define SKF_LL_OFF (-0x200000)
diff --git a/net/core/filter.c b/net/core/filter.c
index 765556b..b2a80a1 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -637,6 +637,12 @@ static u64 __get_raw_cpu_id(u64 ctx, u64 A, u64 X, u64 r4, u64 r5)
return raw_smp_processor_id();
}
+/* note that this only generates 32-bit random numbers */
+static u64 __skb_get_random(u64 ctx, u64 A, u64 X, u64 r4, u64 r5)
+{
+ return (u64)prandom_u32();
+}
+
/* Register mappings for user programs. */
#define A_REG 0
#define X_REG 7
@@ -773,6 +779,7 @@ static bool convert_bpf_extensions(struct sock_filter *fp,
case SKF_AD_OFF + SKF_AD_NLATTR:
case SKF_AD_OFF + SKF_AD_NLATTR_NEST:
case SKF_AD_OFF + SKF_AD_CPU:
+ case SKF_AD_OFF + SKF_AD_RANDOM:
/* arg1 = ctx */
insn->code = BPF_ALU64 | BPF_MOV | BPF_X;
insn->a_reg = ARG1_REG;
@@ -806,6 +813,9 @@ static bool convert_bpf_extensions(struct sock_filter *fp,
case SKF_AD_OFF + SKF_AD_CPU:
insn->imm = __get_raw_cpu_id - __bpf_call_base;
break;
+ case SKF_AD_OFF + SKF_AD_RANDOM:
+ insn->imm = __skb_get_random - __bpf_call_base;
+ break;
}
break;
@@ -1356,6 +1366,7 @@ int sk_chk_filter(struct sock_filter *filter, unsigned int flen)
ANCILLARY(VLAN_TAG);
ANCILLARY(VLAN_TAG_PRESENT);
ANCILLARY(PAY_OFFSET);
+ ANCILLARY(RANDOM);
}
/* ancillary operation unknown or unsupported */
@@ -1741,6 +1752,7 @@ void sk_decode_filter(struct sock_filter *filt, struct sock_filter *to)
[BPF_S_ANC_VLAN_TAG] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_VLAN_TAG_PRESENT] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_PAY_OFFSET] = BPF_LD|BPF_B|BPF_ABS,
+ [BPF_S_ANC_RANDOM] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_LD_W_LEN] = BPF_LD|BPF_W|BPF_LEN,
[BPF_S_LD_W_IND] = BPF_LD|BPF_W|BPF_IND,
[BPF_S_LD_H_IND] = BPF_LD|BPF_H|BPF_IND,
diff --git a/tools/net/bpf_exp.l b/tools/net/bpf_exp.l
index bf7be77..833a966 100644
--- a/tools/net/bpf_exp.l
+++ b/tools/net/bpf_exp.l
@@ -92,6 +92,7 @@ extern void yyerror(const char *str);
"#"?("cpu") { return K_CPU; }
"#"?("vlan_tci") { return K_VLANT; }
"#"?("vlan_pr") { return K_VLANP; }
+"#"?("rand") { return K_RAND; }
":" { return ':'; }
"," { return ','; }
diff --git a/tools/net/bpf_exp.y b/tools/net/bpf_exp.y
index d15efc9..e6306c5 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
+%token K_RXHASH K_CPU K_IFIDX K_VLANT K_VLANP K_POFF K_RAND
%token ':' ',' '[' ']' '(' ')' 'x' 'a' '+' 'M' '*' '&' '#' '%'
@@ -164,6 +164,9 @@ ldb
| OP_LDB K_POFF {
bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
SKF_AD_OFF + SKF_AD_PAY_OFFSET); }
+ | OP_LDB K_RAND {
+ bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+ SKF_AD_OFF + SKF_AD_RANDOM); }
;
ldh
@@ -212,6 +215,9 @@ ldh
| OP_LDH K_POFF {
bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
SKF_AD_OFF + SKF_AD_PAY_OFFSET); }
+ | OP_LDH K_RAND {
+ bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+ SKF_AD_OFF + SKF_AD_RANDOM); }
;
ldi
@@ -265,6 +271,9 @@ ld
| OP_LD K_POFF {
bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
SKF_AD_OFF + SKF_AD_PAY_OFFSET); }
+ | OP_LD K_RAND {
+ bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+ SKF_AD_OFF + SKF_AD_RANDOM); }
| OP_LD 'M' '[' number ']' {
bpf_set_curr_instr(BPF_LD | BPF_MEM, 0, 0, $4); }
| OP_LD '[' 'x' '+' number ']' {
--
1.9.1.423.g4596e3a
--
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