Subject: Re: [PATCH net-next 0/2] Pack struct xfrm_usersa_info and struct xfrm_userpolicy_info

From: Steffen Klassert <[email-masked]>
Date: Tue, 7 Jan 2014 08:47:24 +0100

On Tue, Jan 07, 2014 at 02:48:57PM +0800, Fan Du wrote:
> When trying to setup IPsec configuration on a 64bits host with
> iproute2(32bits compiled), the intened xfrm policy and sa is
> either deficit or wrong when kernel trying to parse user land
> information.
> 
> Further investigatino shows that:
> L: kernel
> R: iproute2
> 
>           sizeof       userpolicy      usersa
> 64bits(unpacked)        168/168        224/224
> 32bits(unpacked)        164/164        220/220
>                          ^   ^
>                          L   R
> 
> To keep kernel and user land see a consistent structure, after
> add packing attribute, now it looks like this:
> 
> 64bits(  packed)        164/164        217/217
> 32bits(  packed)        164/164        217/217
>                          ^   ^
>                          L   R
> 

We don't change userspace exported structures. This breaks
existing userspace tools.