[ping][PATCH v2.1][BZ #15339] Avoid returning EAI_SYSTEM when there's a network error

[Siddhesh Poyarekar <siddhesh at redhat dot com>]

Ping!

Dmitry has already retested, but I'd like another code level review to
make sure that I haven't missed anything obvious.

Thanks,
Siddhesh

On Thu, May 16, 2013 at 09:09:32AM +0530, Siddhesh Poyarekar wrote:
> Hi,
> 
> I've updated this patch to fix another case that the original patch
> broke.  The case can be seen here:
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=958652
> 
> Dmitry, could you please run your testsuite against this to see if
> anything breaks?  It's unlikely, but I'd like to be sure.
> 
> Thanks,
> 
> 	[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.
> 
> commit e656c197931865499a33db8237265ce9de860363
> Author: Siddhesh Poyarekar <siddhesh@redhat.com>
> Date:   Wed May 15 20:46:11 2013 +0530
> 
>     Set EAI_SYSTEM only when h_errno is NETDB_INTERNAL
>     
>     Fixes BZ #15339.
>     
>     NSS_STATUS_UNAVAIL may mean that a necessary input resource is not
>     available.  This could occur in a number of cases including when the
>     network is down, system runs out of file descriptors, etc.  The
>     correct differentiator in such a case is the h_errno, which gives the
>     nature of failure.  In case of failures other than a simple 'not
>     found', we set h_errno as NETDB_INTERNAL and let errno be the
>     identifier for the exact error.
> 
> 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 d368306..bde7dfe 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 failure was due to a system
> +			 error other than the file not being found.  */
> +		      if (errno != 0 && 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;