From: Jiri Pirko <redacted>

Nested handle may contain DEVLINK_ATTR_NETNS_ID attribute that indicates
the network namespace where the nested devlink instance resides. Process
this converting to netns name if possible and print to user.

Signed-off-by: Jiri Pirko <redacted>
---
v2->v3:
- moved netns_name_by_id() into lib/namespace.c
- s/netns_name_by_id/netns_name_from_id/
- rebased on top of new patch "devlink: extend pr_out_nested_handle() to
  print object"
v1->v2:
- use previously introduced netns_netnsid_from_name() instead of code
  duplication for the same function.
- s/nesns_name_by_id_func/netns_name_by_id_func/
---
 devlink/devlink.c   | 23 ++++++++++++++++++++++-
 include/namespace.h |  1 +
 lib/namespace.c     | 34 ++++++++++++++++++++++++++++++++++
 3 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/devlink/devlink.c b/devlink/devlink.c
index f7325477f271..7ba2d0dcac72 100644
--- a/devlink/devlink.c
+++ b/devlink/devlink.c

@@ -24,6 +24,7 @@
 #include <linux/genetlink.h>
 #include <linux/devlink.h>
 #include <linux/netlink.h>
+#include <linux/net_namespace.h>
 #include <libmnl/libmnl.h>
 #include <netinet/ether.h>
 #include <sys/select.h>

@@ -722,6 +723,7 @@ static const enum mnl_attr_data_type devlink_policy[DEVLINK_ATTR_MAX + 1] = {
 	[DEVLINK_ATTR_LINECARD_SUPPORTED_TYPES] = MNL_TYPE_NESTED,
 	[DEVLINK_ATTR_NESTED_DEVLINK] = MNL_TYPE_NESTED,
 	[DEVLINK_ATTR_SELFTESTS] = MNL_TYPE_NESTED,
+	[DEVLINK_ATTR_NETNS_ID] = MNL_TYPE_U32,
 };
 
 static const enum mnl_attr_data_type

@@ -2865,7 +2867,26 @@ static void __pr_out_nested_handle(struct dl *dl, struct nlattr *nla_nested_dl,
 		return;
 	}
 
-	__pr_out_handle_start(dl, tb, false, false);
+	__pr_out_handle_start(dl, tb, tb[DEVLINK_ATTR_NETNS_ID], false);
+	if (tb[DEVLINK_ATTR_NETNS_ID]) {
+		int32_t id = mnl_attr_get_u32(tb[DEVLINK_ATTR_NETNS_ID]);
+
+		if (id >= 0) {