netfilter: nft_bitwise: track register operations

Check if the destination register already contains the data that this
bitwise expression performs. This allows to skip this redundant
operation.

If the destination contains a different bitwise operation, cancel the
register tracking information. If the destination contains no bitwise
operation, update the register tracking information.

Update the payload and meta expression to check if this bitwise
operation has been already performed on the register. Hence, both the
payload/meta and the bitwise expressions are reduced.

There is also a special case: If source register != destination register
and source register is not updated by a previous bitwise operation, then
transfer selector from the source register to the destination register.

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

1 files changed, 1 insertions, 1 deletions

diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c
index 7a7c66e9a50e..f518bf634997 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -235,7 +235,7 @@ static bool nft_payload_reduce(struct nft_regs_track *track,
 	if (!track->regs[priv->dreg].bitwise)
 		return true;
 
-	return false;
+	return nft_expr_reduce_bitwise(track, expr);
 }
 
 static bool nft_payload_offload_mask(struct nft_offload_reg *reg,