getaddrinfo makes a PTR lookup when called with ai_flags = AI_CANONNAME and ai_family = AF_INET: #include <sys/types.h> #include <sys/socket.h> #include <netdb.h> struct addrinfo hints = {.ai_flags = AI_CANONNAME, .ai_family = AF_INET}; int main (int argc, char *argv[]) { struct addrinfo *ap; int err; err = getaddrinfo("netestate.de", "500", &hints, &ap); } This is problematic for me as Javas InetAddress.getByName() works like this on ipv4 systems and causes an unnecessary reverse lookup for every forward lookup. It seems to be fixed in current distributions: https://bugzilla.redhat.com/show_bug.cgi?id=714823 I get the problem when using glibc 2.17 compiled from source. Is this still an issue with glibc 2.19?
Dup. *** This bug has been marked as a duplicate of bug 15218 ***