netfilter: nf_tables: prepare nft audit for set element compaction

nftables audit log format emits the number of added/deleted rules, sets,
set elements and so on, to userspace:

    table=t1 family=2 entries=4 op=nft_register_set
                      ~~~~~~~~~

At this time, the 'entries' key is the number of transactions that will
be applied.

The upcoming set element compression will coalesce subsequent
adds/deletes to the same set requests in the same transaction
request to conseve memory.

Without this patch, we'd under-report the number of altered elements.

Increment the audit counter by the number of elements to keep the reported
entries value the same.

Without this, nft_audit.sh selftest fails because the recorded
(expected) entries key is smaller than the expected one.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Author: Florian Westphal

net/netfilter/nf_tables_api.c

@@ -10398,9 +10398,24 @@ static void nf_tables_commit_audit_free(struct list_head *adl)
 	}
 }
 
+/* nft audit emits the number of elements that get added/removed/updated,
+ * so NEW/DELSETELEM needs to increment based on the total elem count.
+ */
+static unsigned int nf_tables_commit_audit_entrycount(const struct nft_trans *trans)
+{
+	switch (trans->msg_type) {
+	case NFT_MSG_NEWSETELEM:
+	case NFT_MSG_DELSETELEM:
+		return nft_trans_container_elem(trans)->nelems;
+	}
+
+	return 1;
+}
+
 static void nf_tables_commit_audit_collect(struct list_head *adl,
-					   struct nft_table *table, u32 op)
+					   const struct nft_trans *trans, u32 op)
 {
+	const struct nft_table *table = trans->table;
 	struct nft_audit_data *adp;
 
 	list_for_each_entry(adp, adl, list) {
@@ -10410,7 +10425,7 @@ static void nf_tables_commit_audit_collect(struct list_head *adl,
 	WARN_ONCE(1, "table=%s not expected in commit list", table->name);
 	return;
 found:
-	adp->entries++;
+	adp->entries += nf_tables_commit_audit_entrycount(trans);
 	if (!adp->op || adp->op > op)
 		adp->op = op;
 }
@@ -10569,7 +10584,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
 
 		nft_ctx_update(&ctx, trans);
 
-		nf_tables_commit_audit_collect(&adl, table, trans->msg_type);
+		nf_tables_commit_audit_collect(&adl, trans, trans->msg_type);
 		switch (trans->msg_type) {
 		case NFT_MSG_NEWTABLE:
 			if (nft_trans_table_update(trans)) {