[ping][PATCH v2][BZ #15339] Avoid returning EAI_SYSTEM when there's a network error

[Siddhesh Poyarekar <siddhesh at redhat dot com>]

Ping.  I'm looking for an additional review of this code since it's a
bit tricky and I want to be sure I'm not leaving any open gaps.

Thanks,
Siddhesh

On Tue, Apr 09, 2013 at 05:08:49PM +0530, Siddhesh Poyarekar wrote:
> On Mon, Apr 08, 2013 at 09:42:39PM +0400, Dmitry V. Levin wrote:
> > The configuration is essentially a bare chroot without additional
> > configuration, the kernel is 3.8.6.  send_dg doesn't call sendmmsg because
> > of buf2 == NULL.
> 
> Aha, so it's AF_INET and not AF_UNSPEC like your original reproducer
> suggested.  Here's an updated patch for 15339.  The major difference
> here is that I had incorrectly concluded that NSS_STATUS_UNAVAIL
> equals to an internal failure.  It's only an internal failure if none
> of the services were usable and in that case too, only when the
> failure was due to something other than not being able to find the nss
> module.  The latter case is implied if NSS_STATUS_UNAVAIL is returned
> as is along with h_errno as NO_RECOVERY.
> 
> Siddhesh
> 
> 	[BZ #15339]
> 	* nss/getXXbyYY_r.c (REENTRANT_NAME): Set NETDB_INTERNAL only
> 	when no services were used.
> 	* sysdeps/posix/getaddrinfo.c (gaih_inet): Set h_errno.
> 	Return EAI_SYSTEM if h_errno is NETDB_INTERNAL.
> 
> diff --git a/nss/getXXbyYY_r.c b/nss/getXXbyYY_r.c
> index 1067744..9e4d110 100644
> --- a/nss/getXXbyYY_r.c
> +++ b/nss/getXXbyYY_r.c
> @@ -284,11 +284,11 @@ done:
>  #endif
>    *result = status == NSS_STATUS_SUCCESS ? resbuf : NULL;
>  #ifdef NEED_H_ERRNO
> -  if (status == NSS_STATUS_UNAVAIL)
> -    /* Either we failed to lookup the functions or the functions themselves
> -       had a system error.  Set NETDB_INTERNAL here to let the caller know
> -       that the errno may have the real reason for failure.  */
> -      *h_errnop = NETDB_INTERNAL;
> +  if (status == NSS_STATUS_UNAVAIL && !any_service && errno != ENOENT)
> +    /* This happens when we weren't able to use a service for reasons other
> +       than the module not being found.  In such a case, we'd want to tell the
> +       caller that errno has the real reason for failure.  */
> +    *h_errnop = NETDB_INTERNAL;
>    else if (status != NSS_STATUS_SUCCESS && !any_service)
>      /* We were not able to use any service.  */
>      *h_errnop = NO_RECOVERY;
> diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
> index 2309281..2928537 100644
> --- a/sysdeps/posix/getaddrinfo.c
> +++ b/sysdeps/posix/getaddrinfo.c
> @@ -1035,7 +1035,14 @@ gaih_inet (const char *name, const struct gaih_service *service,
>  			}
>  		    }
>  		  else
> -		    status = NSS_STATUS_UNAVAIL;
> +		    {
> +		      status = NSS_STATUS_UNAVAIL;
> +		      /* Could not load any of the lookup functions.  Indicate
> +		         an internal error if the file was found but some other
> +		         error led to the failure.  */
> +		      if (errno != ENOENT)
> +			__set_h_errno (NETDB_INTERNAL);
> +		    }
>  		}
>  
>  	      if (nss_next_action (nip, status) == NSS_ACTION_RETURN)
> @@ -1049,7 +1056,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
>  
>  	  _res.options |= old_res_options & RES_USE_INET6;
>  
> -	  if (status == NSS_STATUS_UNAVAIL)
> +	  if (h_errno == NETDB_INTERNAL)
>  	    {
>  	      result = GAIH_OKIFUNSPEC | -EAI_SYSTEM;
>  	      goto free_and_return;