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

To: Bruce Allan <bwa@xxxxxxxxxx>
Subject: Re: [Lksctp-developers] Re: [PATCH] subset of RFC2553
From: Jon Grimm <jgrimm2@xxxxxxxxxx>
Date: Wed, 19 Feb 2003 17:26:04 -0600
Cc: davem@xxxxxxxxxx, lksctp-developers@xxxxxxxxxxxxxxxxxxxxx, linux-net@xxxxxxxxxxxxxxx, netdev@xxxxxxxxxxx
References: <1045621941.1253.21.camel@xxxxxxxxxxxxxxxxxxxxxxxx>
Sender: netdev-bounce@xxxxxxxxxxx
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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