netfilter: nftables: add helper function to set the base sequence number

This patch adds a helper function to calculate the base sequence number
field that is stored in the nfnetlink header. Use the helper function
whenever possible.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -688,6 +688,11 @@ nf_tables_chain_type_lookup(struct net *net, const struct nlattr *nla,
 	return ERR_PTR(-ENOENT);
 }
 
+static __be16 nft_base_seq(const struct net *net)
+{
+	return htons(net->nft.base_seq & 0xffff);
+}
+
 static const struct nla_policy nft_table_policy[NFTA_TABLE_MAX + 1] = {
 	[NFTA_TABLE_NAME]	= { .type = NLA_STRING,
 				    .len = NFT_TABLE_MAXNAMELEN - 1 },
@@ -712,7 +717,7 @@ static int nf_tables_fill_table_info(struct sk_buff *skb, struct net *net,
 	nfmsg = nlmsg_data(nlh);
 	nfmsg->nfgen_family	= family;
 	nfmsg->version		= NFNETLINK_V0;
-	nfmsg->res_id		= htons(net->nft.base_seq & 0xffff);
+	nfmsg->res_id		= nft_base_seq(net);
 
 	if (nla_put_string(skb, NFTA_TABLE_NAME, table->name) ||
 	    nla_put_be32(skb, NFTA_TABLE_FLAGS, htonl(table->flags)) ||
@@ -1473,7 +1478,7 @@ static int nf_tables_fill_chain_info(struct sk_buff *skb, struct net *net,
 	nfmsg = nlmsg_data(nlh);
 	nfmsg->nfgen_family	= family;
 	nfmsg->version		= NFNETLINK_V0;
-	nfmsg->res_id		= htons(net->nft.base_seq & 0xffff);
+	nfmsg->res_id		= nft_base_seq(net);
 
 	if (nla_put_string(skb, NFTA_CHAIN_TABLE, table->name))
 		goto nla_put_failure;
@@ -2832,7 +2837,7 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, struct net *net,
 	nfmsg = nlmsg_data(nlh);
 	nfmsg->nfgen_family	= family;
 	nfmsg->version		= NFNETLINK_V0;
-	nfmsg->res_id		= htons(net->nft.base_seq & 0xffff);
+	nfmsg->res_id		= nft_base_seq(net);
 
 	if (nla_put_string(skb, NFTA_RULE_TABLE, table->name))
 		goto nla_put_failure;
@@ -3820,7 +3825,7 @@ static int nf_tables_fill_set(struct sk_buff *skb, const struct nft_ctx *ctx,
 	nfmsg = nlmsg_data(nlh);
 	nfmsg->nfgen_family	= ctx->family;
 	nfmsg->version		= NFNETLINK_V0;
-	nfmsg->res_id		= htons(ctx->net->nft.base_seq & 0xffff);
+	nfmsg->res_id		= nft_base_seq(ctx->net);
 
 	if (nla_put_string(skb, NFTA_SET_TABLE, ctx->table->name))
 		goto nla_put_failure;
@@ -4831,7 +4836,7 @@ static int nf_tables_dump_set(struct sk_buff *skb, struct netlink_callback *cb)
 	nfmsg = nlmsg_data(nlh);
 	nfmsg->nfgen_family = table->family;
 	nfmsg->version      = NFNETLINK_V0;
-	nfmsg->res_id	    = htons(net->nft.base_seq & 0xffff);
+	nfmsg->res_id	    = nft_base_seq(net);
 
 	if (nla_put_string(skb, NFTA_SET_ELEM_LIST_TABLE, table->name))
 		goto nla_put_failure;
@@ -4903,7 +4908,7 @@ static int nf_tables_fill_setelem_info(struct sk_buff *skb,
 	nfmsg = nlmsg_data(nlh);
 	nfmsg->nfgen_family	= ctx->family;
 	nfmsg->version		= NFNETLINK_V0;
-	nfmsg->res_id		= htons(ctx->net->nft.base_seq & 0xffff);
+	nfmsg->res_id		= nft_base_seq(ctx->net);
 
 	if (nla_put_string(skb, NFTA_SET_TABLE, ctx->table->name))
 		goto nla_put_failure;
@@ -6233,7 +6238,7 @@ static int nf_tables_fill_obj_info(struct sk_buff *skb, struct net *net,
 	nfmsg = nlmsg_data(nlh);
 	nfmsg->nfgen_family	= family;
 	nfmsg->version		= NFNETLINK_V0;
-	nfmsg->res_id		= htons(net->nft.base_seq & 0xffff);
+	nfmsg->res_id		= nft_base_seq(net);
 
 	if (nla_put_string(skb, NFTA_OBJ_TABLE, table->name) ||
 	    nla_put_string(skb, NFTA_OBJ_NAME, obj->key.name) ||
@@ -7146,7 +7151,7 @@ static int nf_tables_fill_flowtable_info(struct sk_buff *skb, struct net *net,
 	nfmsg = nlmsg_data(nlh);
 	nfmsg->nfgen_family	= family;
 	nfmsg->version		= NFNETLINK_V0;
-	nfmsg->res_id		= htons(net->nft.base_seq & 0xffff);
+	nfmsg->res_id		= nft_base_seq(net);
 
 	if (nla_put_string(skb, NFTA_FLOWTABLE_TABLE, flowtable->table->name) ||
 	    nla_put_string(skb, NFTA_FLOWTABLE_NAME, flowtable->name) ||
@@ -7391,7 +7396,7 @@ static int nf_tables_fill_gen_info(struct sk_buff *skb, struct net *net,
 	nfmsg = nlmsg_data(nlh);
 	nfmsg->nfgen_family	= AF_UNSPEC;
 	nfmsg->version		= NFNETLINK_V0;
-	nfmsg->res_id		= htons(net->nft.base_seq & 0xffff);
+	nfmsg->res_id		= nft_base_seq(net);
 
 	if (nla_put_be32(skb, NFTA_GEN_ID, htonl(net->nft.base_seq)) ||
 	    nla_put_be32(skb, NFTA_GEN_PROC_PID, htonl(task_pid_nr(current))) ||