Re: [PATCH net-next v4 01/22] rtnetlink: provide permanent hardware address in RTM_NEWLINK

[Jakub Kicinski <jakub.kicinski@netronome.com>]

On Thu, 21 Mar 2019 14:40:21 +0100 (CET), Michal Kubecek wrote:
> Permanent hardware address of a network device was traditionally provided
> via ethtool ioctl interface but as Jiri Pirko pointed out in a review of
> ethtool netlink interface, rtnetlink is much more suitable for it so let's
> add it to the RTM_NEWLINK message.
> 
> As permanent address is not modifiable, reject userspace requests
> containing IFLA_PERM_ADDRESS attribute.
> 
> Note: we already provide permanent hardware address for bond slaves;
> unfortunately we cannot drop that attribute for backward compatibility
> reasons.
> 
> Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
> ---
>  include/uapi/linux/if_link.h | 1 +
>  net/core/rtnetlink.c         | 4 ++++
>  2 files changed, 5 insertions(+)
> 
> diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> index 5b225ff63b48..351ef746b8b0 100644
> --- a/include/uapi/linux/if_link.h
> +++ b/include/uapi/linux/if_link.h
> @@ -167,6 +167,7 @@ enum {
>  	IFLA_NEW_IFINDEX,
>  	IFLA_MIN_MTU,
>  	IFLA_MAX_MTU,
> +	IFLA_PERM_ADDRESS,
>  	__IFLA_MAX
>  };
>  
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index a51cab95ba64..a72e8f4d777b 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -1026,6 +1026,7 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
>  	       + nla_total_size(4)  /* IFLA_CARRIER_DOWN_COUNT */
>  	       + nla_total_size(4)  /* IFLA_MIN_MTU */
>  	       + nla_total_size(4)  /* IFLA_MAX_MTU */
> +	       + nla_total_size(MAX_ADDR_LEN) /* IFLA_PERM_ADDRESS */
>  	       + 0;
>  }
>  
> @@ -1683,6 +1684,8 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
>  	    nla_put_s32(skb, IFLA_NEW_IFINDEX, new_ifindex) < 0)
>  		goto nla_put_failure;
>  
> +	if (nla_put(skb, IFLA_PERM_ADDRESS, dev->addr_len, dev->perm_addr))

Should we check the perm_addr is non-zero, i.e. it has been filled in
by the driver?

> +		goto nla_put_failure;
>  
>  	rcu_read_lock();
>  	if (rtnl_fill_link_af(skb, dev, ext_filter_mask))
> @@ -1742,6 +1745,7 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
>  	[IFLA_CARRIER_DOWN_COUNT] = { .type = NLA_U32 },
>  	[IFLA_MIN_MTU]		= { .type = NLA_U32 },
>  	[IFLA_MAX_MTU]		= { .type = NLA_U32 },
> +	[IFLA_PERM_ADDRESS]	= { .type = NLA_REJECT },
>  };
>  
>  static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {