On 7/27/20 1:47 PM, Stephen Hemminger wrote:

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On Mon, 27 Jul 2020 12:21:17 -0700
Roopa Prabhu [off-list ref] wrote:

quoted

-            + nla_total_size(1)  /* IFLA_PROTO_DOWN */
+            + rtnl_proto_down_size(dev)  /* proto down */

Changing the size of a netlink field is an ABI change in the kernel.
This has the potential to break existing programs.

Wouldn't it be safer to add a new link attribute for the reason
rather than overloading the existing attribute?

yes, It does add a new attribute. Its just that I moved all protodown 
attribute handling to a separate function