[NTLUG:Discuss] Bug in gethostbyaddr?
Neil Aggarwal
neil at JAMMConsulting.com
Fri Mar 12 09:57:00 CST 2004
Hello:
I am trying to use gethostbyaddr to find the reverse DNS entry for
the IP 216.234.230.2 but it gives me back a null result.
When I do a dig on that IP, I get many results. Is that throwing
off gethostbyaddr?
I have tried this on RedHat 9 and Fedora Core 1 and they both
act the same.
Here is a piece of test code that I used:
#include <sys/types.h>
#include <netinet/in.h>
#include <netdb.h>
#define BUFFER_SIZE 1024
/** Function to format an IP address */
void format_ip(ip, buffer)
unsigned long ip;
char *buffer;
{
snprintf(buffer,BUFFER_SIZE,"%lu.%lu.%lu.%lu",
(ip & 0xff000000) >> 24,
(ip & 0x00ff0000) >> 16,
(ip & 0x0000ff00) >> 8,
(ip & 0x000000ff) >> 0);
}
/** Function to print an IP to the screen */
void print_ip(prefix, ip)
char *prefix;
unsigned long ip;
{
char buffer[BUFFER_SIZE];
format_ip(ip,buffer);
printf( "%s %s\n", prefix, buffer );
}
/** Function to check reverse DNS for an IP */
void check_revDns(remote_ip)
unsigned long remote_ip;
{
/* Print the IP */
print_ip( "Checking ", remote_ip );
/* Perform the lookup */
unsigned long network_ip = htonl(remote_ip);
struct hostent *result;
result = gethostbyaddr((const void*)&network_ip, sizeof(unsigned
long), AF_INET);
if( result == NULL ) {
printf( "Hostentry is null\n" );
return;
}
if( result->h_name == NULL ) {
printf( "Hostname is null\n" );
return;
}
printf( "Got back %s\n", result->h_name );
}
int main(argc, argv)
int argc;
char *argv[];
{
/* Check the reverse DNS for 216.234.230.2 */
check_revDns(0xd8eae602);
/* Check the reverse DNS for 207.229.77.210 */
check_revDns(0xcfe54dd2);
}
Here is its output:
Checking 216.234.230.2
Hostentry is null
Checking 207.229.77.210
Got back 207-229-77-210.cortland.com
When I do: dig -x 216.234.230.2
I get this result:
;; Truncated, retrying in TCP mode.
; <<>> DiG 9.2.2-P3 <<>> -x 216.234.230.2
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16406
;; flags: qr rd ra; QUERY: 1, ANSWER: 215, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION:
;2.230.234.216.in-addr.arpa. IN PTR
;; ANSWER SECTION:
2.230.234.216.in-addr.arpa. 2188 IN PTR tx.carbone-int.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR ns1.alphainternet.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR usa.carbone-int.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.jwd.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.ppf.org.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.4act.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.gtbc.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.otcon.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.tgabc.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.wgmak.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.7falls.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.avlcom.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.bpnavs.org.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.drgkfc.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.ergnow.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.nuvine.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.petsch.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.ppadot.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.alphaip.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.gugirls.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.kidcore.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.mcenery.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.mvp-hot.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.petmate.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.rsueiso.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.shoptms.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.sifocus.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.speed-x.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.sw-asse.org.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.world21.us.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.am-photo.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.artbyian.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.bowguard.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.cowtruxs.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.doskocil.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.drhoward.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.ebumpkin.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.gunguard.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.gunguard.net.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.hpaustin.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.ipsclone.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.maidoors.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.radijazz.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.radiovet.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.shoplvms.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.vidpoker.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.altermann.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.ameritint.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.bluesanta.org.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.deepellum.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.donnieday.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.eddoandco.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.golfguard.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.golfguard.net.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.hifi-home.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.medialogy.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.nxtonline.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.partsdemo.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.pokersyte.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.red-river.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.rollstock.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.sepradyne.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.swatrocks.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.tetrajazz.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.truckresq.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.vettablet.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.bingobugle.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.bingobugle.net.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.bitesafety.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.dewittseed.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.dinner4two.org.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.e-toolcrib.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.eamesworld.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.ergsystems.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.evasjunque.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.nickelrama.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.panelparts.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.pkgsaysall.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.pokercheck.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.sharmellas.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.sipfwc2000.org.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.slotsdepot.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.spencetrim.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.stevetrine.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.stevetrine.net.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.texasleads.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.tony-evers.keller.tx.us.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.visualaide.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.cameraguard.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.capitaltree.net.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.ceceliashop.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.curvestexas.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.haveyouread.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.helpthekids.net.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.justwatchus.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.knickknacks.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.namegame101.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.vetedtablet.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.worldslides.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.aztecbg-club.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.branchwarren.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.dbgtechsales.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.dentonsports.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.easybizideas.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.eformsonline.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.hearindallas.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.impactsports.net.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.jabbconcepts.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.kellersoccer.org.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.livinthegame.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.livinthegame.org.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.midwestminis.net.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.rrministries.org.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.shirleymissa.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.southwestwja.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.tdaflashtest.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.thesourceusa.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.uproarsports.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.urbanleasing.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.whydoyouride.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.alphacommerce.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.alphainternet.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.blacksonbrick.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.cardcollector.info.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.cubesolutions.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.feedthemonkey.info.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.funskillgames.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.galaxycabling.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.go-dragracing.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.got2givegirls.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.lonestarfilms.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.mortgage-zone.net.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.pafenbachtrio.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.red-river-eng.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.sarahhamilton.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.senioramatour.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.sportsbeanies.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.texomamedical.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.bkb-associates.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.bnbconnections.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.cardcollecting.info.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.dallascochlear.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.m3technologies.net.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.moonfishstudio.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.newportsdallas.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.recruitmentads.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.rodneyanderson.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.swingpointgolf.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.thesilverchair.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.treborstaffing.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR mail.zebra-printing.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.counselorethics.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.fabricmarketing.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.galaxytechnical.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.hearingimpaired.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.holisticurology.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.moonfishstudios.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.neighborhoodvet.net.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.profishinreport.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.shadeswholesale.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.theoremcreative.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.thestockscalper.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.aquacool-gaffney.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.aviddistributors.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.blacksonlighting.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.eagleadvisorsinc.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.findatexaslawyer.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.hotspringscondos.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.jamesedwardgroup.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.morris-whiteside.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.prestigiouspaper.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.thecardcollector.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.cambridgegroupdls.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.compliancegateway.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.densonproductions.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.gamblinginfosites.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.hothouserecording.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.lakewoodpediatric.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.landesengineering.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.markofdistinction.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.womensgolfsociety.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.artistsexpressions.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.athleticrecruiters.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.dallasleasingguide.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.discovernorthtexas.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.newportsrestaurant.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.packagingsolutions.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.pinnaclerecruiting.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.acacorporatehousing.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.artists-expressions.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.gracefellowshipintl.org.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.longconsultinggroup.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.northtexasprecision.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.oldetowneconsulting.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.outcomesimprovement.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.shopinfineonraceway.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.thecompletebackyard.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.themysterybookstore.net.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.allianceteleservices.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.collegiateconnection.org.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.corpimagingsolutions.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.choicefurnituresource.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.greatamericanbassclub.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.identicalpanelsystems.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.totallyuniquecleaning.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.americaninn-greenville.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.lawnandgardenofhouston.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.onlinesalesproductions.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.southlakefitnesscenter.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.athleticrecruitingreport.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.businesstravelersnetwork.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.greenelectronicsolutions.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.bluechiprecruitingservice.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR
mail.pediatricnetworkfoundation.com.
2.230.234.216.in-addr.arpa. 2188 IN PTR sql1.alphainternet.com.
;; AUTHORITY SECTION:
230.234.216.in-addr.arpa. 2188 IN NS tony.alphainternet.com.
;; Query time: 425 msec
;; SERVER: 207.229.64.3#53(207.229.64.3)
;; WHEN: Fri Mar 12 09:51:34 2004
;; MSG SIZE rcvd: 7019
Any ideas what is happening and a way to work around it?
Thanks,
Neil
--
Neil Aggarwal, JAMM Consulting, (972)612-6056, www.JAMMConsulting.com
FREE! Valuable info on how your business can reduce operating costs by
17% or more in 6 months or less! => http://newsletter.JAMMConsulting.com
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