netfilter: nf_tables: missing iterator type in lookup walk

Add missing decorator type to lookup expression and tighten WARN_ON_ONCE
check in pipapo to spot earlier that this is unset.

Fixes: 29b359cf ("netfilter: nft_set_pipapo: walk over current view on netlink dump")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nft_lookup.c

@@ -216,6 +216,7 @@ static int nft_lookup_validate(const struct nft_ctx *ctx,
 		return 0;
 
 	iter.genmask	= nft_genmask_next(ctx->net);
+	iter.type	= NFT_ITER_UPDATE;
 	iter.skip	= 0;
 	iter.count	= 0;
 	iter.err	= 0;

net/netfilter/nft_set_pipapo.c

@@ -2123,7 +2123,8 @@ static void nft_pipapo_walk(const struct nft_ctx *ctx, struct nft_set *set,
 	const struct nft_pipapo_field *f;
 	unsigned int i, r;
 
-	WARN_ON_ONCE(iter->type == NFT_ITER_UNSPEC);
+	WARN_ON_ONCE(iter->type != NFT_ITER_READ &&
+		     iter->type != NFT_ITER_UPDATE);
 
 	rcu_read_lock();
 	if (iter->type == NFT_ITER_READ)