On Wed, 28 Feb 2024 16:01:49 -0800 Kees Cook wrote:

So, I found several cases where struct net_device is included in the
middle of another structure, which makes my proposal more awkward. But I
also don't understand why it's in the _middle_. Shouldn't it always be
at the beginning (with priv stuff following it?)
Quick search and examined manually: git grep 'struct net_device [a-z0-9_]*;'

struct rtw89_dev
struct ath10k
etc.

Ugh, yes, the (ab)use of NAPI.

Some even have two included (?)

And some seem to be cargo-culted from out-of-tree code and are unused :S

But I still like the idea -- Gustavo has been solving these cases with
having two structs, e.g.:

struct net_device {
	...unchanged...
};

struct net_device_alloc {
	struct net_device	dev;
	u32			priv_size;
	u8			priv_data[] __counted_by(priv_size) __aligned(NETDEV_ALIGN);
};

And internals can use struct net_device_alloc...

That's... less pretty. I'd rather push the ugly into the questionable
users. Make them either allocate the netdev dynamically and store 
a pointer, or move the netdev to the end of the struct.

But yeah, that's a bit of a cleanup :(