[nft PATCH] JSON: Improve performance of json_events_cb()

From: Phil Sutter <phil@nwl.cc>
To: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: netfilter-devel@vger.kernel.org, Eric Garver <e@erig.me>
Subject: [nft PATCH] JSON: Improve performance of json_events_cb()
Date: Wed, 13 May 2020 16:38:03 +0200	[thread overview]
Message-ID: <20200513143803.25109-1-phil@nwl.cc> (raw)

The function tries to insert handles into JSON input for echo option.
Yet there may be nothing to do if the given netlink message doesn't
contain a handle, e.g. if it is an 'add element' command. Calling
seqnum_to_json() is pointless overhead in that case, and if input is
large this overhead is significant. Better wait with that call until
after checking if the message is relevant at all.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 src/parser_json.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/parser_json.c b/src/parser_json.c
index 4468407b0ecd0..3a84bd96af31f 100644
--- a/src/parser_json.c
+++ b/src/parser_json.c
@@ -3847,12 +3847,15 @@ static uint64_t handle_from_nlmsg(const struct nlmsghdr *nlh)
 }
 int json_events_cb(const struct nlmsghdr *nlh, struct netlink_mon_handler *monh)
 {
-	json_t *tmp, *json = seqnum_to_json(nlh->nlmsg_seq);
 	uint64_t handle = handle_from_nlmsg(nlh);
+	json_t *tmp, *json;
 	void *iter;
 
-	/* might be anonymous set, ignore message */
-	if (!json || !handle)
+	if (!handle)
+		return MNL_CB_OK;
+
+	json = seqnum_to_json(nlh->nlmsg_seq);
+	if (!json)
 		return MNL_CB_OK;
 
 	tmp = json_object_get(json, "add");
-- 
2.26.2

