Re: [PATCH net-next v5] rtnetlink: add new RTM_GETSTATS message to dump link stats

[Nicolas Dichtel]

Le 19/04/2016 20:47, Eric Dumazet a écrit :

On Tue, 2016-04-19 at 14:31 -0400, David Miller wrote:

+#ifndef HAVE_EFFICIENT_UNALIGNED_ACCESS
+       /* IF necessary, add a zero length NOP attribute so that the
+        * nla_data() of the IFLA_STATS64 will be 64-bit aligned.
+        *
+        * The nlattr header is 4 bytes in size, that's why we test
+        * if the skb->data _is_ aligned.  This NOP attribute, plus
+        * nlattr header for IFLA_STATS64, will make nla_data() 8-byte
+        * aligned.
+        */
+       if (IS_ALIGNED((unsigned long)skb->data, 8)) {
+               attr = nla_reserve(skb, IFLA_PAD, 0);
+               if (!attr)
+                       return -EMSGSIZE;
+       }
+#endif

Since we want to use this in other places, we could define a helper.

nla_align_64bit(skb, attribute)  or something.

Yes, with the corresponding nla_total_size_64bit()