[PATCH iproute2-next 2/2] tc: Add NLM_F_ECHO support for filters

[Victor Nogueira <victor@mojatatu.com>]

If the user specifies this flag for a filter command the kernel will
return the command's result back to user space.
For example:

  tc -echo filter add dev lo parent ffff: protocol ip matchall action ok

  added filter dev lo parent ffff: protocol ip pref 49152 matchall chain 0

As illustrated above, the kernel will give us a pref of 491252

The same can be done for other filter commands (replace, delete, and
change). For example:

  tc -echo filter del dev lo parent ffff: pref 49152 protocol ip matchall

  deleted filter dev lo parent ffff: protocol ip pref 49152 matchall chain 0

Signed-off-by: Victor Nogueira <victor@mojatatu.com>
---
 tc/tc_filter.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tc/tc_filter.c b/tc/tc_filter.c
index eb45c5887..54790ddc6 100644
--- a/tc/tc_filter.c
+++ b/tc/tc_filter.c
@@ -76,6 +76,7 @@ static int tc_filter_modify(int cmd, unsigned int flags, int argc, char **argv)
 	char  d[IFNAMSIZ] = {};
 	char  k[FILTER_NAMESZ] = {};
 	struct tc_estimator est = {};
+	int ret;
 
 	if (cmd == RTM_NEWTFILTER && flags & NLM_F_CREATE)
 		protocol = htons(ETH_P_ALL);
@@ -221,7 +222,12 @@ static int tc_filter_modify(int cmd, unsigned int flags, int argc, char **argv)
 	if (est.ewma_log)
 		addattr_l(&req.n, sizeof(req), TCA_RATE, &est, sizeof(est));
 
-	if (rtnl_talk(&rth, &req.n, NULL) < 0) {
+	if (echo_request)
+		ret = rtnl_echo_talk(&rth, &req.n, json, print_filter);
+	else
+		ret = rtnl_talk(&rth, &req.n, NULL);
+
+	if (ret < 0) {
 		fprintf(stderr, "We have an error talking to the kernel\n");
 		return 2;
 	}
-- 
2.25.1