JSON: Add support for echo option

The basic principle is to not return a JSON object freshly created from
netlink responses, but just update the existing user-provided one to
make sure callers get back exactly what they expect.

To achieve that, keep the parsed JSON object around in a global variable
('cur_root') and provide a custom callback to insert handles into it
from received netlink messages. The tricky bit here is updating rules
since unique identification is problematic. Therefore drop possibly
present handles from input and later assume updates are received in
order so the first rule not having a handle set is the right one.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 8 insertions, 5 deletions

diff --git a/src/monitor.c b/src/monitor.c
index 14ccbc5f..88a61de4 100644
--- a/src/monitor.c
+++ b/src/monitor.c
@@ -42,7 +42,7 @@
 
 #define nft_mon_print(monh, ...) nft_print(&monh->ctx->nft->output, __VA_ARGS__)
 
-static struct nftnl_table *netlink_table_alloc(const struct nlmsghdr *nlh)
+struct nftnl_table *netlink_table_alloc(const struct nlmsghdr *nlh)
 {
 	struct nftnl_table *nlt;
 
@@ -55,7 +55,7 @@ static struct nftnl_table *netlink_table_alloc(const struct nlmsghdr *nlh)
 	return nlt;
 }
 
-static struct nftnl_chain *netlink_chain_alloc(const struct nlmsghdr *nlh)
+struct nftnl_chain *netlink_chain_alloc(const struct nlmsghdr *nlh)
 {
 	struct nftnl_chain *nlc;
 
@@ -68,7 +68,7 @@ static struct nftnl_chain *netlink_chain_alloc(const struct nlmsghdr *nlh)
 	return nlc;
 }
 
-static struct nftnl_set *netlink_set_alloc(const struct nlmsghdr *nlh)
+struct nftnl_set *netlink_set_alloc(const struct nlmsghdr *nlh)
 {
 	struct nftnl_set *nls;
 
@@ -94,7 +94,7 @@ static struct nftnl_set *netlink_setelem_alloc(const struct nlmsghdr *nlh)
 	return nls;
 }
 
-static struct nftnl_rule *netlink_rule_alloc(const struct nlmsghdr *nlh)
+struct nftnl_rule *netlink_rule_alloc(const struct nlmsghdr *nlh)
 {
 	struct nftnl_rule *nlr;
 
@@ -107,7 +107,7 @@ static struct nftnl_rule *netlink_rule_alloc(const struct nlmsghdr *nlh)
 	return nlr;
 }
 
-static struct nftnl_obj *netlink_obj_alloc(const struct nlmsghdr *nlh)
+struct nftnl_obj *netlink_obj_alloc(const struct nlmsghdr *nlh)
 {
 	struct nftnl_obj *nlo;
 
@@ -908,6 +908,9 @@ int netlink_echo_callback(const struct nlmsghdr *nlh, void *data)
 	if (!echo_monh.ctx->nft->output.echo)
 		return MNL_CB_OK;
 
+	if (ctx->nft->output.json)
+		return json_events_cb(nlh, &echo_monh);
+
 	return netlink_events_cb(nlh, &echo_monh);
 }