[PATCH] getaddrinfo: Always allocate canonical name on the heap

[Adhemerval Zanella]

On 11/05/2017 07:07, Florian Weimer wrote:
> A further simplification could eliminate the canon variable in
> gaih_inet and replace it with canonbuf.  However, canonbuf is
> used as a flag in the nscd code, which makes this somewhat
> non-straightforward.
> 
> 2017-05-11  Florian Weimer  <fweimer@redhat.com>
> 
> 	* sysdeps/posix/getaddrinfo.c (getcanonname): New function.
> 	(gaih_inet): Remove malloc_canonbuf variable.  Call getcanonname.
> 
> diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
> index dc02b11..d92db70 100644
> --- a/sysdeps/posix/getaddrinfo.c
> +++ b/sysdeps/posix/getaddrinfo.c
> @@ -308,6 +308,30 @@ typedef enum nss_status (*nss_getcanonname_r)
>     int *errnop, int *h_errnop);
>  extern service_user *__nss_hosts_database attribute_hidden;
>  
> +/* This function is called if a canonical name is requested, but if
> +   the service function did not provide it.  It tries to obtain the
> +   name using getcanonname_r from the same service NIP.  If the name
> +   cannot be canonicalized, return a copy of NAME.  Return NULL on
> +   memory allocation failure.  The returned string is allocated on the
> +   heap; the caller has to free it.  */
> +static char *
> +getcanonname (service_user *nip, struct gaih_addrtuple *at, const char *name)
> +{
> +  nss_getcanonname_r cfct = __nss_lookup_function (nip, "getcanonname_r");
> +  char *s = (char *) name;
> +  if (cfct != NULL)
> +    {
> +      char buf[256];
> +      int herrno;
> +      int rc;
> +      if (DL_CALL_FCT (cfct, (at->name ?: name, buf, sizeof (buf),
> +			      &s, &rc, &herrno)) != NSS_STATUS_SUCCESS)
> +	/* If the canonical name cannot be determined, use the passed
> +	   string.  */
> +	s = (char *) name;
> +    }
> +  return strdup (name);
> +}

I think you need to use __strdup here, I am seeing check-local-plt failures on
master.