netdev - [PATCH iproute2 v2] iplink: enable to specify index when changing netns

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Date:   Tue, 12 Oct 2021 11:34:05 +0200
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     stephen@...workplumber.org
Cc:     netdev@...r.kernel.org, dsahern@...il.com,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>
Subject: [PATCH iproute2 v2] iplink: enable to specify index when changing netns

When an interface is moved to another netns, it's possible to specify a
new ifindex. Let's add this support.

Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=eeb85a14ee34
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>
---

v1 -> v2:
  reuse index option instead adding a new option

 ip/iplink.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/ip/iplink.c b/ip/iplink.c
index 18b2ea25b7c2..1d2776c3b5c9 100644
--- a/ip/iplink.c
+++ b/ip/iplink.c
@@ -578,6 +578,7 @@ static int iplink_parse_vf(int vf, int *argcp, char ***argvp,
 
 int iplink_parse(int argc, char **argv, struct iplink_req *req, char **type)
 {
+	bool move_netns = false;
 	char *name = NULL;
 	char *dev = NULL;
 	char *link = NULL;
@@ -683,6 +684,7 @@ int iplink_parse(int argc, char **argv, struct iplink_req *req, char **type)
 					  IFLA_NET_NS_PID, &netns, 4);
 			else
 				invarg("Invalid \"netns\" value\n", *argv);
+			move_netns = true;
 		} else if (strcmp(*argv, "multicast") == 0) {
 			NEXT_ARG();
 			req->i.ifi_change |= IFF_MULTICAST;
@@ -980,9 +982,11 @@ int iplink_parse(int argc, char **argv, struct iplink_req *req, char **type)
 		}
 	}
 
-	if (!(req->n.nlmsg_flags & NLM_F_CREATE) && index) {
+	if (index &&
+	    (!(req->n.nlmsg_flags & NLM_F_CREATE) &&
+	     !move_netns)) {
 		fprintf(stderr,
-			"index can be used only when creating devices.\n");
+			"index can be used only when creating devices or when moving device to another netns.\n");
 		exit(-1);
 	}
 
@@ -1019,6 +1023,9 @@ int iplink_parse(int argc, char **argv, struct iplink_req *req, char **type)
 		/* Not renaming to the same name */
 		if (name == dev)
 			name = NULL;
+
+		if (index)
+			addattr32(&req->n, sizeof(*req), IFLA_NEW_IFINDEX, index);
 	} else {
 		if (name != dev) {
 			fprintf(stderr,
-- 
2.33.0