Re: [PATCH net-next 3/5] sctp: add spp_ipv6_flowlabel and spp_dscp for sctp_paddrparams

[Neil Horman]

On Mon, Jun 25, 2018 at 04:31:26PM +0900, David Miller wrote:
> From: Xin Long <lucien....@gmail.com>
> Date: Mon, 25 Jun 2018 10:14:35 +0800
> 
> >  struct sctp_paddrparams {
> > @@ -773,6 +775,8 @@ struct sctp_paddrparams {
> >     __u32                   spp_pathmtu;
> >     __u32                   spp_sackdelay;
> >     __u32                   spp_flags;
> > +   __u32                   spp_ipv6_flowlabel;
> > +   __u8                    spp_dscp;
> >  } __attribute__((packed, aligned(4)));
> 
> I don't think you can change the size of this structure like this.
> 
> This check in sctp_setsockopt_peer_addr_params():
> 
>       if (optlen != sizeof(struct sctp_paddrparams))
>               return -EINVAL;
> 
> is going to trigger in old kernels when executing programs
> built against the new struct definition.
> 
I think thats also the reason its a packed aligned attribute, it can't be
changed, or older kernels won't be able to fill it out properly.
Neil