Re: [Lksctp-developers] Re: [PATCH] subset of RFC2553

[Jon Grimm <jgrimm2@us.ibm.com>]

Or if you don't care about the alignment of the __data field at all:

#define _SS_MAXSIZE 128
#if ULONG_MAX > 0xffffffff
#define _ALIGNSIZE ((sizeof(__u64)))
#else
#define _ALIGNSIZE ((sizeof(__u32)))
#endif
struct sockaddr_storage {
	sa_family_t     ss_family;
	char            __data[_SS_MAXSIZE-sizeof(sa_family_t)*2 + _ALIGNSIZE];
} __attribute ((aligned(_ALIGNSIZE)));


jon



Jon Grimm wrote:
> 
> Bruce Allan wrote:
> >
> > How about this instead (a combination of your comment above and glibc's
> > definition of sockaddr_storage):
> > #define _SS_MAXSIZE     128
> > #define _ALIGNSIZE      (sizeof(struct sockaddr *))
> > #if ULONG_MAX > 0xffffffff
> > #define __ss_aligntype  __u64
> > #else
> > #define __ss_aligntype  __u32
> > #endif
> > struct sockaddr_storage {
> >         sa_family_t     ss_family;
> >         __ss_aligntype  __data[(_SS_MAXSIZE/sizeof(__ss_aligntype))-1];
> > } __attribute__ ((aligned(_ALIGNSIZE)));
> >
> 
> Hmmm... this seemed to generate a 124-byte struct instead of the stated
> intent of 128.
> 
> Maybe instead:
> 
> #define _SS_MAXSIZE 128
> #if ULONG_MAX > 0xffffffff
> #define __ss_aligntype      __u64
> #else
> #define __ss_aligntype      __u32
> #endif
> #define _ALIGNSIZE (sizeof(__ss_aligntype))
> struct sockaddr_storage {
>         sa_family_t     ss_family;
>         __ss_aligntype  __data[_SS_MAXSIZE/_ALIGNSIZE-1] __attribute__
> ((aligned(_ALIGNSIZE)));
> } __attribute ((aligned(_ALIGNSIZE)));
> 
> Align the struct on _ALIGNSIZE; align _data on _ALIGNSIZE to to generate
> padding between ss_family and __data.
> 
> Best Regards,
> jon
> 
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