netdev - Re: [patch iproute2-next v3 4/6] devlink: introduce support for netns id for nested handle

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Date: Thu, 26 Oct 2023 11:08:04 -0600
From: David Ahern <dsahern@...il.com>
To: Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org
Cc: stephen@...workplumber.org, daniel.machon@...rochip.com
Subject: Re: [patch iproute2-next v3 4/6] devlink: introduce support for netns
 id for nested handle

On 10/24/23 4:04 AM, Jiri Pirko wrote:
> From: Jiri Pirko <jiri@...dia.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@...dia.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 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) {

why does the kernel side even add DEVLINK_ATTR_NETNS_ID if
peernet2id_alloc fails?


> +			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);

ie., how is -1 useful to userspace?


> +		}
> +	}
>  	pr_out_handle_end(dl);
>  }
>