Messages in this thread | | | Date | Mon, 13 Mar 2023 15:17:58 +0800 | Subject | Re: [PATCH net-next v6 4/5] ip_tunnel: Preserve pointer const in ip_tunnel_info_opts | From | Gavin Li <> |
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On 3/9/2023 11:05 PM, Eric Dumazet wrote: > External email: Use caution opening links or attachments > > > On Thu, Mar 9, 2023 at 3:59 PM Eric Dumazet <edumazet@google.com> wrote: >> On Thu, Mar 9, 2023 at 2:48 PM Gavin Li <gavinl@nvidia.com> wrote: >>> Change ip_tunnel_info_opts( ) from static function to macro to cast return >>> value and preserve the const-ness of the pointer. >>> >>> Signed-off-by: Gavin Li <gavinl@nvidia.com> >>> --- >>> include/net/ip_tunnels.h | 11 ++++++----- >>> 1 file changed, 6 insertions(+), 5 deletions(-) >>> >>> diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h >>> index fca357679816..3e5c102b841f 100644 >>> --- a/include/net/ip_tunnels.h >>> +++ b/include/net/ip_tunnels.h >>> @@ -67,6 +67,12 @@ struct ip_tunnel_key { >>> GENMASK((sizeof_field(struct ip_tunnel_info, \ >>> options_len) * BITS_PER_BYTE) - 1, 0) >>> >>> +#define ip_tunnel_info_opts(info) \ >>> + _Generic(info, \ >>> + const typeof(*(info)) * : ((const void *)((info) + 1)),\ >>> + default : ((void *)((info) + 1)) \ >>> + ) >>> + >> Hmm... >> >> This looks quite dangerous, we lost type safety with the 'default' >> case, with all these casts. >> >> What about using something cleaner instead ? >> >> (Not sure why we do not have an available generic helper for this kind >> of repetitive things) >> > Or more exactly : > > diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h > index fca3576798166416982ee6a9100b003810c49830..17fc6c8f7e0b9e5303c1fb9e5dad77c5310e01a9 > 100644 > --- a/include/net/ip_tunnels.h > +++ b/include/net/ip_tunnels.h > @@ -485,10 +485,11 @@ static inline void iptunnel_xmit_stats(struct > net_device *dev, int pkt_len) > } > } > > -static inline void *ip_tunnel_info_opts(struct ip_tunnel_info *info) > -{ > - return info + 1; > -} > +#define ip_tunnel_info_opts(info) \ > + (_Generic(info, \ > + const struct ip_tunnel_info * : (const void *)((info) > + 1), \ > + struct ip_tunnel_info * : (void *)((info) + 1)) \ > + ) > > static inline void ip_tunnel_info_opts_get(void *to, > const struct ip_tunnel_info *info) ACK
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