[patch net-next v4 5/7] devlink: introduce support for netns id for nested handle

[Jiri Pirko <jiri@resnulli.us>]

From: Jiri Pirko <jiri@nvidia.com>

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 <jiri@nvidia.com>
---
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 f06f3069e80a..f276026b9ba7 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
@@ -2866,7 +2868,26 @@ 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) {
+			char *name = netns_name_from_id(id);
+
+			if (name) {
+				print_string(PRINT_ANY, "netns",
+					     " netns %s", name);
+				free(name);
+			} else {
+				print_int(PRINT_ANY, "netnsid",
+					  " netnsid %d", id);
+			}
+		} else {
+			print_string(PRINT_FP, NULL, " netnsid %s", "unknown");
+			print_int(PRINT_JSON, "netnsid", NULL, id);
+		}
+	}
 	pr_out_handle_end(dl);
 }
 
diff --git a/include/namespace.h b/include/namespace.h
index 6483630b8082..4ae294749962 100644
--- a/include/namespace.h
+++ b/include/namespace.h
@@ -59,5 +59,6 @@ struct netns_func {
 };
 
 int netns_id_from_name(struct rtnl_handle *rtnl, const char *name);
+char *netns_name_from_id(int32_t id);
 
 #endif /* __NAMESPACE_H__ */
diff --git a/lib/namespace.c b/lib/namespace.c
index f03f4bbabceb..d3aeb9658e73 100644
--- a/lib/namespace.c
+++ b/lib/namespace.c
@@ -188,3 +188,37 @@ out:
 	free(answer);
 	return ret;
 }
+
+struct netns_name_from_id_ctx {
+	int32_t id;
+	char *name;
+	struct rtnl_handle *rth;
+};
+
+static int netns_name_from_id_func(char *nsname, void *arg)
+{
+	struct netns_name_from_id_ctx *ctx = arg;
+	int32_t ret;
+
+	ret = netns_id_from_name(ctx->rth, nsname);
+	if (ret < 0 || ret != ctx->id)
+		return 0;
+	ctx->name = strdup(nsname);
+	return 1;
+}
+
+char *netns_name_from_id(int32_t id)
+{
+	struct rtnl_handle rth;
+	struct netns_name_from_id_ctx ctx = {
+		.id = id,
+		.rth = &rth,
+	};
+
+	if (rtnl_open(&rth, 0) < 0)
+		return NULL;
+	netns_foreach(netns_name_from_id_func, &ctx);
+	rtnl_close(&rth);
+
+	return ctx.name;
+}
-- 
2.41.0