Re: [PATCH] Fix incorrect getaddrinfo assertion trigger

[Allan McRae <allan at archlinux dot org>]

Ping.

On 30/08/13 22:05, Allan McRae wrote:
> [BS #9954]
> 
> With the following /etc/hosts:
> 127.0.0.1       www.my-domain.es
> 127.0.1.1       www.my-domain.es
> 192.168.0.1     www.my-domain.es
> 
> Using getaddrinfo() on www.my-domain.es, trigger the following assertion:
> ../sysdeps/posix/getaddrinfo.c:1473: rfc3484_sort: Assertion
> `src->results[i].native == -1 || src->results[i].native == a1_native' failed.
> 
> This is due to two different bugs:
> - In rfc3484_sort() rule 7, src->results[i].native is assigned even if
> src->results[i].index is -1, meaning that no interface is associated.
> - In getaddrinfo() the source IP address used with the lo interface needs a
> special case, as it can be any IP within 127.X.Y.Z.
> 
> ---
> 
> This is a patch taken from bugzilla.  I can not replicate it myself, even
> with the attached testcase on bugzilla.  However, I have users reporting this
> issue that also can confirm this patch fixes the assertions for them.  I
> believe this patch is widely used by other distributions (at least Debian
> and Fedora).
> 
> There is a negative comment by Ulrich here:
> https://sourceware.org/bugzilla/show_bug.cgi?id=9954#c2
> 
> I think that comment is partially correct, in that it is hiding a bug from
> a faulty DNS provider, in which case this patch is correct in that it
> improves robustness.  That is why this bug does not affect most people.
> However, I am not fully confident about that assessment...
> 
> Can anyone replicate or confirm/correct my reasoning why most people can
> not replicate?
> 
> 
> 
> 20xx-xx-xx  Aurelien Jarno  <aurelien@aurel32.net>
> 
> 	[BS #9954]
> 	* sysdeps/posix/getaddrinfo.c (rfc3484_sort): do not assign native
> 	result if the result has no associated interface.
> 	* sysdeps/posix/getaddrinfo.c (getaddrinfo): correctly detect 
> 	interface for all 127.X.Y.Z addresses.
> 
> 
>  sysdeps/posix/getaddrinfo.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
> index 52177e4..c0ded84 100644
> --- a/sysdeps/posix/getaddrinfo.c
> +++ b/sysdeps/posix/getaddrinfo.c
> @@ -1735,13 +1735,13 @@ rfc3484_sort (const void *p1, const void *p2, void *arg)
>  
>  	      /* Fill in the results in all the records.  */
>  	      for (int i = 0; i < src->nresults; ++i)
> -		if (src->results[i].index == a1_index)
> +		if (a1_index != -1 && src->results[i].index == a1_index)
>  		  {
>  		    assert (src->results[i].native == -1
>  			    || src->results[i].native == a1_native);
>  		    src->results[i].native = a1_native;
>  		  }
> -		else if (src->results[i].index == a2_index)
> +		else if (a2_index != -1 && src->results[i].index == a2_index)
>  		  {
>  		    assert (src->results[i].native == -1
>  			    || src->results[i].native == a2_native);
> @@ -2601,7 +2601,14 @@ getaddrinfo (const char *name, const char *service,
>  			  tmp.addr[0] = 0;
>  			  tmp.addr[1] = 0;
>  			  tmp.addr[2] = htonl (0xffff);
> -			  tmp.addr[3] = sinp->sin_addr.s_addr;
> +			  /* Special case for lo interface, the source address
> +			     being possibly different than the interface 
> +			     address. */
> +			  if ((ntohl(sinp->sin_addr.s_addr) & 0xff000000)
> +			      == 0x7f000000)
> +			    tmp.addr[3] = htonl(0x7f000001);
> +			  else
> +			    tmp.addr[3] = sinp->sin_addr.s_addr;
>  			}
>  		      else
>  			{
>