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.

Chema Gonzalez committed 12 years ago

Commit 4cd36751 parent 5a4ae5f6 files · +39 −2Browse files

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include/uapi/linux/filter.h+2−1

@@ -130,7 +130,8 @@ struct sock_fprog { /* Required for SO_ATTACH_FILTER. */ · 129 unmodified lines
130	130	#define SKF_AD_VLAN_TAG 44
131	131	#define SKF_AD_VLAN_TAG_PRESENT 48
132	132	#define SKF_AD_PAY_OFFSET 52
133		−#define SKF_AD_MAX 56
	133	+#define SKF_AD_RANDOM 56
	134	+#define SKF_AD_MAX 60
134	135	#define SKF_NET_OFF (-0x100000)
135	136	#define SKF_LL_OFF (-0x200000)
136	137