DNS glibc functions confused by trailing hyphen in host name

My company uses a very simple http browser implemenation written in
gnu C++ to asynchronously post data to customers. We use
gethostbyname_r to convert FQDN to IP address, then set up a socket,
set the headers, send the data, etc.

One of our customers has a host name with a trailing hypen, i.e their
FQDN is like

foo-.bar.com

The various glibc library DNS lookup functions fail when looking up
this FQDN. I tried gethostbyname_r and getaddrinfo. gethostbyname_r
returns NO_RECOVERY. getaddrinfo returns EAI_NONAME. I've tried this
on RH 6.2, and on RHEL 3 and 4.

nslookup, host, and dig all find this name with no problem.

AFAIKT from looking at IETF specs, the trailing hyphen is illegal.
But
I don't want to have to tell my customer to change his host name.

What are the nslookup, host, and dig commands doing differently to
lookup the name than what is done in the glibc functions?

Thanks for the help!

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

>>>>> davelasker writes:

davelasker> My company uses a very simple http browser implemenation written in
davelasker> gnu C++ to asynchronously post data to customers. We use
davelasker> gethostbyname_r to convert FQDN to IP address, then set up a socket,
davelasker> set the headers, send the data, etc.

davelasker> One of our customers has a host name with a trailing hypen,i.e their
davelasker> FQDN is like

davelasker> foo-.bar.com

davelasker> The various glibc library DNS lookup functions fail when looking up
davelasker> this FQDN. I tried gethostbyname_r and getaddrinfo. gethostbyname_r
davelasker> returns NO_RECOVERY. getaddrinfo returns EAI_NONAME. I've tried this
davelasker> on RH 6.2, and on RHEL 3 and 4.

davelasker> nslookup, host, and dig all find this name with no problem.

davelasker> AFAIKT from looking at IETF specs, the trailing hyphen is illegal.
davelasker> But
davelasker> I don't want to have to tell my customer to change his hostname.

davelasker> What are the nslookup, host, and dig commands doing differently to
davelasker> lookup the name than what is done in the glibc
davelasker> functions?

They're doing DNS queries without using glibc get...() routines. To fix
this issue at your end, you've to patch /lib{64,}/libnss_dns.so* which
is provided by glibc.

davelasker> Thanks for the help!

HTH
- --
Ashish Shukla आशीष श�क�ल http://wahjava.wordpress.com/
·-- ·- ···· ·--- ·- ···- ·- ·--·-· --· -- ·- ·· ·-·· ·-·-·- -·-· --- --
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.9 (GNU/Linux)

iEYEARECAAYFAkg3J4UACgkQHy+EEHYuXnRtAgCfVoFMpvZeZC OcgNk2JyD7wHKY
zsgAoOw/t7eAk7h9pHscOzRCMvCdo2da
=+FPX
-----END PGP SIGNATURE-----