[nf PATCH 3/5] netfilter: nf_tables: Introduce struct nft_obj_dump_ctx

[Phil Sutter <phil@nwl.cc>]

Convert struct nft_obj_filter into a dump context data structure
equivalent to nft_rule_dump_ctx. Make it reside inside struct
netlink_callback::ctx scratch area so there's no need to allocate and
free it. Also carry the 'reset' boolean instead of determining this upon
each call to nf_tables_dump_obj() by inspecting the nlmsg_type.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 net/netfilter/nf_tables_api.c | 66 ++++++++++++++---------------------
 1 file changed, 26 insertions(+), 40 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 4bccd15a67105..f6d8edcf0b9d5 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -7665,25 +7665,23 @@ static int nf_tables_fill_obj_info(struct sk_buff *skb, struct net *net,
 	return -1;
 }
 
-struct nft_obj_filter {
+struct nft_obj_dump_ctx {
+	unsigned int	s_idx;
 	char		*table;
 	u32		type;
+	bool		reset;
 };
 
 static int nf_tables_dump_obj(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	const struct nfgenmsg *nfmsg = nlmsg_data(cb->nlh);
-	const struct nft_table *table;
-	unsigned int idx = 0, s_idx = cb->args[0];
-	struct nft_obj_filter *filter = cb->data;
+	struct nft_obj_dump_ctx *ctx = (void *)cb->ctx;
 	struct net *net = sock_net(skb->sk);
 	int family = nfmsg->nfgen_family;
 	struct nftables_pernet *nft_net;
+	const struct nft_table *table;
 	struct nft_object *obj;
-	bool reset = false;
-
-	if (NFNL_MSG_TYPE(cb->nlh->nlmsg_type) == NFT_MSG_GETOBJ_RESET)
-		reset = true;
+	unsigned int idx = 0;
 
 	rcu_read_lock();
 	nft_net = nft_pernet(net);
@@ -7696,19 +7694,14 @@ static int nf_tables_dump_obj(struct sk_buff *skb, struct netlink_callback *cb)
 		list_for_each_entry_rcu(obj, &table->objects, list) {
 			if (!nft_is_active(net, obj))
 				goto cont;
-			if (idx < s_idx)
+			if (idx < ctx->s_idx)
 				goto cont;
-			if (idx > s_idx)
-				memset(&cb->args[1], 0,
-				       sizeof(cb->args) - sizeof(cb->args[0]));
-			if (filter && filter->table &&
-			    strcmp(filter->table, table->name))
+			if (ctx->table && strcmp(ctx->table, table->name))
 				goto cont;
-			if (filter &&
-			    filter->type != NFT_OBJECT_UNSPEC &&
-			    obj->ops->type->type != filter->type)
+			if (ctx->type != NFT_OBJECT_UNSPEC &&
+			    obj->ops->type->type != ctx->type)
 				goto cont;
-			if (reset) {
+			if (ctx->reset) {
 				char *buf = kasprintf(GFP_ATOMIC,
 						      "%s:%u",
 						      table->name,
@@ -7727,7 +7720,7 @@ static int nf_tables_dump_obj(struct sk_buff *skb, struct netlink_callback *cb)
 						    NFT_MSG_NEWOBJ,
 						    NLM_F_MULTI | NLM_F_APPEND,
 						    table->family, table,
-						    obj, reset) < 0)
+						    obj, ctx->reset) < 0)
 				goto done;
 
 			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
@@ -7738,44 +7731,37 @@ static int nf_tables_dump_obj(struct sk_buff *skb, struct netlink_callback *cb)
 done:
 	rcu_read_unlock();
 
-	cb->args[0] = idx;
+	ctx->s_idx = idx;
 	return skb->len;
 }
 
 static int nf_tables_dump_obj_start(struct netlink_callback *cb)
 {
+	struct nft_obj_dump_ctx *ctx = (void *)cb->ctx;
 	const struct nlattr * const *nla = cb->data;
-	struct nft_obj_filter *filter = NULL;
 
-	if (nla[NFTA_OBJ_TABLE] || nla[NFTA_OBJ_TYPE]) {
-		filter = kzalloc(sizeof(*filter), GFP_ATOMIC);
-		if (!filter)
+	BUILD_BUG_ON(sizeof(*ctx) > sizeof(cb->ctx));
+
+	if (nla[NFTA_OBJ_TABLE]) {
+		ctx->table = nla_strdup(nla[NFTA_OBJ_TABLE], GFP_ATOMIC);
+		if (!ctx->table)
 			return -ENOMEM;
+	}
 
-		if (nla[NFTA_OBJ_TABLE]) {
-			filter->table = nla_strdup(nla[NFTA_OBJ_TABLE], GFP_ATOMIC);
-			if (!filter->table) {
-				kfree(filter);
-				return -ENOMEM;
-			}
-		}
+	if (nla[NFTA_OBJ_TYPE])
+		ctx->type = ntohl(nla_get_be32(nla[NFTA_OBJ_TYPE]));
 
-		if (nla[NFTA_OBJ_TYPE])
-			filter->type = ntohl(nla_get_be32(nla[NFTA_OBJ_TYPE]));
-	}
+	if (NFNL_MSG_TYPE(cb->nlh->nlmsg_type) == NFT_MSG_GETOBJ_RESET)
+		ctx->reset = true;
 
-	cb->data = filter;
 	return 0;
 }
 
 static int nf_tables_dump_obj_done(struct netlink_callback *cb)
 {
-	struct nft_obj_filter *filter = cb->data;
+	struct nft_obj_dump_ctx *ctx = (void *)cb->ctx;
 
-	if (filter) {
-		kfree(filter->table);
-		kfree(filter);
-	}
+	kfree(ctx->table);
 
 	return 0;
 }
-- 
2.41.0