[PATCH] inet: getnameinfo fix serv for abstract socket [BZ #27634]

[Florian Weimer]

* Daniel Black:

> @@ -459,6 +459,15 @@ gni_serv_local (struct scratch_buffer *tmpbuf,
>  	       const struct sockaddr *sa, socklen_t addrlen,
>  	       char *serv, socklen_t servlen, int flags)
>  {
> +  if (((const struct sockaddr_un *) sa)->sun_path[0] == '\0')
> +    {
> +      /* Abstract socket */
> +      socklen_t len = addrlen - offsetof (struct sockaddr_un, sun_path);
> +      if (len > servlen)
> +	return EAI_OVERFLOW;
> +      memcpy (serv, ((const struct sockaddr_un *) sa)->sun_path, len);
> +      return 0;
> +    }
>    return checked_copy
>      (serv, servlen, ((const struct sockaddr_un *) sa)->sun_path);
>  }

Is this really useful as an interface?  The caller would still have to
know the struct sockaddr_un layout to figure out the length.  So it
could just struct sockaddr_un directly.

In general, getnameinfo itself is not very portable when applied to
AF_UNIX addresses.  Not all systems that have AF_UNIX also implement
it for getnameinfo.  How the path is mapped between the host and
service names also differs.  Therefore, I think applications should
look for AF_UNIX addresses directly.  There is also no string
transformation needed, unlike for the other address families.