Description of problem:

Everything started when i was having strange results with DNS reverse
restriction functions in postfix configurations. With some tests we found that
postfix was receiving 'unknown' from getnameinfo system function and, so, wasnt
being able to 'see' reverse addresses. The discussion can be found here:

http://marc.info/?l=postfix-users&m=119973018023513&w=2

So .... we found that the problem isnt with postfix, but with getnameinfo
function which returned 'unknown' for ip addresses that DO had correctly setup
reverse names.

With some further testings, i found that getnameinfo behaves strangely with
multiple PTR records that has a LOT of records. In my initial problem, as
related on the postfix mailing list threaded linked above, the ip address had
258 PTR records.


Version-Release number of selected component (if applicable):

[root@correio name-addr-test]# rpm -qf /usr/include/netdb.h             
glibc-headers-2.3.6-3
[root@correio name-addr-test]# 


How reproducible:

in fedora 7 i tried, apparently always

i found this problem in a fedora 5 box, but then i did further tests on a fedora
7 box and found it's already buggy. Unfortunelly i have no fedora 8 box to test.


Steps to Reproduce:

1. grab getnameinfo.c which cames with postfix sources
(auxiliary/name-addr-test/getnameinfo.c) and compile it. This is a simple plain
program to invoke getnameinfo and resolve some name/ip address

I have attached the getnameinfo.c file to this bug request to make it easier for
those who want test it

compile it with:  gcc getnameinfo.c -o getnameinfo

2. grab the reverse zone i have attached to this bug request, 192.168.1.rev

and load it in some bind with

zone "1.168.192.in-addr.arpa" IN {
        type master;
        file "192.168.1.rev";
};

3. make sure your /etc/resolv.conf points to the bind you loaded the reverse
zone above and run getnameinfo and try to resolve 192.168.1.1

./getnameinfo 192.168.1.1

Actual results:

host line command shows that this IP address has 197 PTR records:

[root@firewall named]# host 192.168.1.1 | grep "domain name pointer" | wc -l    
197
[root@firewall named]#


but getnameinfo shows the ip address has NO PTR record

[root@firewall named]# ./getnameinfo  192.168.1.1                           
getnameinfo 192.168.1.1: Name or service not known
[root@firewall named]# 

Expected results:

i would expect to see getnameinfo returning any of the PTR records, not unknown

Please note that if you comment the last line (use ;) of this reverse zone file
and reload it, getnameinfo WILL work.

[root@firewall named]# host 192.168.1.1 | grep "domain name pointer" | wc -l   
196
[root@firewall named]#


[root@firewall named]# ./getnameinfo  192.168.1.1                           
Hostname:       ptr160.short.com.br
Address:        192.168.1.1
[root@firewall named]# 


Additional info:

it seems that this 196 and 197 number is not exact. If i used a larger domain
name different than short.com.br, this work/not work number will change.

Using a pretty large name (ptrXXX.thisisnotashortdomainname.com.br), the
work/not work number changed to 193 and 194.

WORKS with 193 records

[root@firewall named]# host 192.168.1.1 | grep "domain name pointer" | wc -l
193
[root@firewall named]# 

[root@firewall named]# ./getnameinfo  192.168.1.1                           
Hostname:       ptr157.thisisnotashortdomainname.com.br
Address:        192.168.1.1
[root@firewall named]# 

does NOT works with 194 records

[root@firewall named]# host 192.168.1.1 | grep "domain name pointer" | wc -l 
194
[root@firewall named]# 

[root@firewall named]# ./getnameinfo  192.168.1.1                           
getnameinfo 192.168.1.1: Name or service not known
[root@firewall named]# 


other interesting situation is that i tried this in VERY old redhat 9 box and
getnameinfo.c correctly resolved IP addresses with 400 PTRs ...

[root@aparecida named]# cat /etc/redhat-release 
Red Hat Linux release 9 (Shrike)
[root@aparecida named]# 

[root@aparecida named]# host 192.168.1.1  | grep "domain name pointer" | wc -l
    400
[root@aparecida named]# 

[root@aparecida named]# ./getnameinfo 192.168.1.1
Hostname:       ptr396.short.com.br
Address:        192.168.1.1
[root@aparecida named]#