Re: [PATCH] daemon.c: avoid accessing ss_family member of struct sockaddr_storage

From: Brandon Casey <casey@nrlssc.navy.mil>
Date: Mar 15, 2010, 21:42 UTC
Message-ID: <s0MQZSOEsdBJUhITxC3jwfFJk5PnIEo0WR5z_GEnSOw@cipher.nrlssc.navy.mil>
In-Reply-To: <20100315212915.GB25342@coredump.intra.peff.net>

On 03/15/2010 04:29 PM, Jeff King wrote:

Show 17 quoted lines

> On Mon, Mar 15, 2010 at 04:03:00PM -0500, Brandon Casey wrote:
> 
>> When NO_SOCKADDR_STORAGE is set for a platform, either sockaddr_in or
>> sockaddr_in6 is used intead.  Neither of which has an ss_family member.
>> They have an sin_family and sin6_family member respectively.  Since the
>> addrcmp() function accesses the ss_family member of a sockaddr_storage
>> struct, compilation fails on platforms which define NO_SOCKADDR_STORGAGE.
>>
>> Since any sockaddr_* structure can be cast to a struct sockaddr and
>> have its sa_family member read, do so here to workaround this issue.
> 
> Didn't Gary say that AIX 5.2 sticks sa_len at the front of their
> sockaddr?
> 
> We know that whatever we actually have (an actual sockaddr_storage, or a
> sockaddr_in, or a sockaddr_in6) will have the family at the front, so
> can you just cast it to sa_family_t?

I expect that the layout of the sockaddr_* family of structures will follow the layout of struct sockaddr, otherwise they wouldn't be compatible.

In other words, I think that if struct sockaddr looks like this:

  struct sockaddr {
        uchar_t         sa_len;         /* total length */
        sa_family_t     sa_family;      /* address family */
        char            sa_data[14];    /* actually longer; address value */
  };

then somewhere else, struct sockaddr_in looks like this:

  struct sockaddr_in {
        uchar_t         sin_len;
        sin_family_t    sin_family;
        sin_port;
        sin_addr;
        ...
  };

> Or am I wrong in assuming that, and on AIX sockaddr_in actually has
> sa_len at the front, so casting to sockaddr does the right thing (and my
> recommendation above would actually be broken)? The AIX boxen I have
> access to are all down at the moment.

Maybe Gary can check for us... Gary, what does the declaration for struct sockaddr_in look like in your AIX header file?

-brandon