diff options
| author | Chema Gonzalez <chema@google.com> | 2014-04-21 09:21:24 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-04-22 21:27:57 -0400 |
| commit | 4cd3675ebf74d7f559038ded6aa8088e4099a83d (patch) | |
| tree | 6988d7dc3352fbcce10c5c510ffa11e6f30217de /net | |
| parent | 5a4ae5f6e7d4b2b5a9b8981d513345053e40b6ac (diff) | |
filter: added BPF random opcode
Added a new ancillary load (bpf call in eBPF parlance) that produces
a 32-bit random number. We are implementing it as an ancillary load
(instead of an ISA opcode) because (a) it is simpler, (b) allows easy
JITing, and (c) seems more in line with generic ISAs that do not have
"get a random number" as a instruction, but as an OS call.
The main use for this ancillary load is to perform random packet sampling.
Signed-off-by: Chema Gonzalez <chema@google.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/core/filter.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index cd58614660cf..78a636e60a0b 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -643,6 +643,12 @@ 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 __get_random_u32(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 @@ -779,6 +785,7 @@ 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; @@ -812,6 +819,9 @@ 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 = __get_random_u32 - __bpf_call_base; + break; } break; @@ -1362,6 +1372,7 @@ 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 */ @@ -1746,6 +1757,7 @@ 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, |