Re: [batadv,v14 5/5] batman-adv: avoid superfluous DAT DHT_PUT additions to local DAT

["Linus Lüssing" <linus.luessing@c0d3.blue>]

On Wed, Oct 07, 2026 at 09:24:23AM +0200, Sven Eckelmann wrote:
> On Wednesday, 7 October 2026 03:08:03 CEST Linus Lüssing wrote:
> > > - [Medium] batadv: UAPI source compatibility breakage via reserved field rename
> > 
> > I would have thought that for a field called "reserved" it would
> > be clear that it'd be subject to change in the future.
> 
> To play the devils advocate: But programs would still fail when they 
> manually initialize this field to 0.

On the other hand I'm thinking they should have memset() the
struct to zero in the first place, instead of manually setting a
reserved field to 0.

Similar to ioctl()'s for instance, where there too you should
memset/zero the full struct, passed argument, I believe, instead of
just zero'ing individual fields as there might be new fields getting
appended in the future.

Interestingly, include/uapi/linux/ethtool.h has an explicit note
for this:

```
  26 /* Note on reserved space.
  27  * Reserved fields must not be accessed directly by user space because
  28  * they may be replaced by a different field in the future. They must
  29  * be initialized to zero before making the request, e.g. via memset
  30  * of the entire structure or implicitly by not being set in a structure
  31  * initializer.
  32  */
```

Which we don't have in batadv_packet.h though. (So technically,
someone could complain about such a rename because we don't have such a note?)