ebpf: add prandom helper for packet sampling

This work is similar to commit 4cd3675ebf74 ("filter: added BPF
random opcode") and adds a possibility for packet sampling in eBPF.

Currently, this is only possible in classic BPF and useful to
combine sampling with f.e. packet sockets, possible also with tc.

Example function proto-type looks like:

  u32 (*prandom_u32)(void) = (void *)BPF_FUNC_get_prandom_u32;

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/core/filter.c b/net/core/filter.c
index 7a4eb7030dba..4344db39af2e 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1139,6 +1139,8 @@ sk_filter_func_proto(enum bpf_func_id func_id)
                 return &bpf_map_update_elem_proto;
         case BPF_FUNC_map_delete_elem:
                 return &bpf_map_delete_elem_proto;
+        case BPF_FUNC_get_prandom_u32:
+                return &bpf_get_prandom_u32_proto;
         default:
                 return NULL;
         }