netfilter: meta: add PRANDOM support

Can be used to randomly match packets e.g. for statistic traffic sampling.

See commit 3ad0040573b0c00f8848
("bpf: split state from prandom_u32() and consolidate {c, e}BPF prngs")
for more info why this doesn't use prandom_u32 directly.

Unlike bpf nft_meta can be built as a module, so add an EXPORT_SYMBOL
for prandom_seed_full_state too.

Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index be41ffc128b8..b19be0a098c0 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -681,6 +681,7 @@ enum nft_exthdr_attributes {
  * @NFT_META_IIFGROUP: packet input interface group
  * @NFT_META_OIFGROUP: packet output interface group
  * @NFT_META_CGROUP: socket control group (skb->sk->sk_classid)
+ * @NFT_META_PRANDOM: a 32bit pseudo-random number
  */
 enum nft_meta_keys {
         NFT_META_LEN,
@@ -707,6 +708,7 @@ enum nft_meta_keys {
         NFT_META_IIFGROUP,
         NFT_META_OIFGROUP,
         NFT_META_CGROUP,
+        NFT_META_PRANDOM,
 };
 
 /**