netfilter: nf_tables: add nft_dup expression

This new expression uses the nf_dup engine to clone packets to a given gateway.
Unlike xt_TEE, we use an index to indicate output interface which should be
fine at this stage.

Moreover, change to the preemtion-safe this_cpu_read(nf_skb_duplicated) from
nf_dup_ipv{4,6} to silence a lockdep splat.

Based on the original tee expression from Arturo Borrero Gonzalez, although
this patch has diverted quite a bit from this initial effort due to the
change to support maps.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/net/netfilter/nft_dup.h b/include/net/netfilter/nft_dup.h
new file mode 100644
index 000000000000..6b84cf6491a2
--- /dev/null
+++ b/include/net/netfilter/nft_dup.h
@@ -0,0 +1,9 @@
+#ifndef _NFT_DUP_H_
+#define _NFT_DUP_H_
+
+struct nft_dup_inet {
+	enum nft_registers	sreg_addr:8;
+	enum nft_registers	sreg_dev:8;
+};
+
+#endif /* _NFT_DUP_H_ */