Re: [Patch 4/5] Network Drop Monitor: Adding drop monitor implementation & Netlink protocol

[David Miller <davem@davemloft.net>]

From: Neil Horman <nhorman@tuxdriver.com>
Date: Tue, 3 Mar 2009 14:21:07 -0500

> On Tue, Mar 03, 2009 at 09:19:09PM +0300, Evgeniy Polyakov wrote:
> > > +struct net_dm_config_msg {
> > > +	size_t entries;
> > > +	struct net_dm_config_entry options[0];
> > > +};
> > 
> > Isn't size_t have different size on different platforms?
> > 
> Probably, but we're only sending this data over netlink sockets, so despite the
> platform, I don't really see this as an issue.  About the only place for concern
> I think are cases like x86_64 and ppc64, in the event you have a 64 bit kernel
> and 32 bit user space, and in those the app can be adjusted to compensate for
> this.  I suppose I can fixate the size if its a real concern, but I don't think
> it really is.

Neil, that is _THE_ concern.  You have to use portable types that
will be both sized and aligned identically on both 32-bit and
64-bit variants of a given platform.

This means size_t is absolutely not usable.

We really don't have a clean way to add compat layer translators
for netlink, so you have to get this right from the beginning.