netfilter: nf_tables: add forward expression to the netdev family

You can use this to forward packets from ingress to the egress path of
the specified interface. This provides a fast path to bounce packets
from one interface to another specific destination interface.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index 22043ce..731288a 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -984,6 +984,18 @@
 #define NFTA_DUP_MAX		(__NFTA_DUP_MAX - 1)
 
 /**
+ * enum nft_fwd_attributes - nf_tables fwd expression netlink attributes
+ *
+ * @NFTA_FWD_SREG_DEV: source register of output interface (NLA_U32: nft_register)
+ */
+enum nft_fwd_attributes {
+	NFTA_FWD_UNSPEC,
+	NFTA_FWD_SREG_DEV,
+	__NFTA_FWD_MAX
+};
+#define NFTA_FWD_MAX	(__NFTA_FWD_MAX - 1)
+
+/**
  * enum nft_gen_attributes - nf_tables ruleset generation attributes
  *
  * @NFTA_GEN_ID: Ruleset generation ID (NLA_U32)