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filter: added BPF random opcode

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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>
This commit is contained in:
Chema Gonzalez 2014-04-21 09:21:24 -07:00 • committed by David S. Miller
commit 4cd3675ebf
6 changed files with 39 additions and 2 deletions
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3
include/uapi/linux/filter.h
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@ -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)