cdbfile not opening inside djbdns-1.05

Question

I am performing an assignment named DNS filtering. For that I compiled djbdns-1.05 source code. I have maintained my data using constant database (cdb) file named as "cdbDomainList.cdb" in root.

Also I have configured dnscache using localhost.

But, I am struggling whenever I am going to open that "cdbDomainList.cdb" file inside query.c file. My logic is :

---

int fd;

fd = open("/root/cdbDomainList.cdb", O_RDWR);

if(fd == -1){

        printf("Error while opening cdbDomainList.cdb.\n");

        return EXIT_FAILURE;
}

---

cdbDomainList.cdb file is present at given path But, still While running dnscache, always I am getting "Error while opening cdbDomainList.cdb.".

I have tried with O_RDONLY flag also still same results.

I am expecting some intelligent suggestions. Thanks in advance.