made more robust and commented my code.
This commit is contained in:
John Beppu
parent
b332e779e6
commit
50bc101b7d
@ -32,14 +32,24 @@
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#include <sys/types.h>
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#include <netinet/in.h>
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/*
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| I'm only implementing non-interactive mode;
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| I totally forgot nslookup even had an interactive mode.
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| [ TODO ]
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| + find out how to use non-default name servers
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| + find out how the real nslookup gets the default name server
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*/
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static const char nslookup_usage[] =
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"only implementing non-interactive mode\n"
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"I totally forgot nslookup even had an interactive mode\n"
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"nslookup [HOST]\n\n"
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;
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/* */
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/* I have to see how the real nslookup does this.
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* I could dig through /etc/resolv.conf, but is there a
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* better (programatic) way?
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*/
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static void
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server_fprint(FILE *dst)
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{
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@ -67,7 +77,9 @@ addr_fprint(char *addr, FILE *dst)
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return 0;
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}
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/* */
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/* changes a c-string matching the perl regex \d+\.\d+\.\d+\.\d+
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* into a uint32_t
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*/
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static uint32_t
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str_to_addr(const char *addr)
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{
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@ -86,59 +98,63 @@ str_to_addr(const char *addr)
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return htonl(ip);
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}
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/* */
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/* takes the NULL-terminated array h_addr_list, and
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* prints its contents appropriately
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*/
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static int
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addr_list_fprint(char **h_addr_list, FILE *dst)
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{
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int i;
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int i, j;
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char *addr_string = (h_addr_list[1])
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? "Addresses"
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: "Address";
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fprintf(dst, "%s: ", addr_string);
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for (i = 0; h_addr_list[i]; i++) {
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for (i = 0, j = 0; h_addr_list[i]; i++, j++) {
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addr_fprint(h_addr_list[i], dst);
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if (h_addr_list[i+1]) {
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fprintf(dst, ", ");
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/* real nslookup does this */
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if (j == 4) {
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if (h_addr_list[i+1]) {
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fprintf(dst, "\n ");
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}
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j = 0;
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} else {
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if (h_addr_list[i+1]) {
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fprintf(dst, ", ");
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}
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}
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}
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fprintf(dst,"\n");
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return 0;
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}
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/* */
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/* gethostbyaddr wrapper */
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static struct hostent *
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lookup_by_name(const char *hostname)
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gethostbyaddr_wrapper(const char *address)
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{
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struct hostent *host;
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struct in_addr addr;
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host = gethostbyname(hostname);
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addr.s_addr = str_to_addr(address);
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return gethostbyaddr((char *) &addr, 4, AF_INET); /* IPv4 only for now */
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}
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/* print the results as nslookup would */
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static struct hostent *
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hostent_fprint(struct hostent *host, FILE *dst)
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{
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if (host) {
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fprintf(stdout, "Name: %s\n", host->h_name);
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addr_list_fprint(host->h_addr_list, stdout);
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fprintf(dst, "Name: %s\n", host->h_name);
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addr_list_fprint(host->h_addr_list, dst);
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} else {
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herror("crap");
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fprintf(dst, "*** %s\n", hstrerror(h_errno));
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}
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return host;
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}
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/* */
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static struct hostent *
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lookup_by_addr(const char *addr)
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{
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struct hostent *host;
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host = gethostbyaddr(addr, 4, AF_INET); /* IPv4 only for now */
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if (host) {
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fprintf(stdout, "Name: %s\n", host->h_name);
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addr_list_fprint(host->h_addr_list, stdout);
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} else {
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herror("crap");
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}
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return host;
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}
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/* */
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/* naive function to check whether char *s is an ip address */
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static int
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is_ip_address(const char *s)
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{
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@ -153,16 +169,20 @@ is_ip_address(const char *s)
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int
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nslookup_main(int argc, char **argv)
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{
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struct in_addr addr;
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struct hostent *host;
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if (argc < 2) {
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usage(nslookup_usage);
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}
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server_fprint(stdout);
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if (is_ip_address(argv[1])) {
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addr.s_addr = str_to_addr(argv[1]);
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lookup_by_addr((char *) &addr);
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host = gethostbyaddr_wrapper(argv[1]);
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} else {
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lookup_by_name(argv[1]);
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host = gethostbyname(argv[1]);
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}
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hostent_fprint(host, stdout);
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return 0;
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}
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/* $Id: nslookup.c,v 1.1 2000/01/29 12:59:01 beppu Exp $ */
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/* $Id: nslookup.c,v 1.2 2000/01/30 09:47:16 beppu Exp $ */
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94
nslookup.c
94
nslookup.c
@ -32,14 +32,24 @@
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#include <sys/types.h>
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#include <netinet/in.h>
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/*
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| I'm only implementing non-interactive mode;
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| I totally forgot nslookup even had an interactive mode.
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|
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| [ TODO ]
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| + find out how to use non-default name servers
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| + find out how the real nslookup gets the default name server
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*/
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static const char nslookup_usage[] =
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"only implementing non-interactive mode\n"
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"I totally forgot nslookup even had an interactive mode\n"
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"nslookup [HOST]\n\n"
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;
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/* */
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/* I have to see how the real nslookup does this.
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* I could dig through /etc/resolv.conf, but is there a
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* better (programatic) way?
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*/
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static void
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server_fprint(FILE *dst)
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{
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@ -67,7 +77,9 @@ addr_fprint(char *addr, FILE *dst)
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return 0;
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}
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/* */
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/* changes a c-string matching the perl regex \d+\.\d+\.\d+\.\d+
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* into a uint32_t
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*/
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static uint32_t
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str_to_addr(const char *addr)
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{
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@ -86,59 +98,63 @@ str_to_addr(const char *addr)
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return htonl(ip);
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}
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/* */
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/* takes the NULL-terminated array h_addr_list, and
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* prints its contents appropriately
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*/
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static int
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addr_list_fprint(char **h_addr_list, FILE *dst)
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{
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int i;
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int i, j;
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char *addr_string = (h_addr_list[1])
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? "Addresses"
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: "Address";
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fprintf(dst, "%s: ", addr_string);
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for (i = 0; h_addr_list[i]; i++) {
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for (i = 0, j = 0; h_addr_list[i]; i++, j++) {
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addr_fprint(h_addr_list[i], dst);
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if (h_addr_list[i+1]) {
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fprintf(dst, ", ");
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/* real nslookup does this */
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if (j == 4) {
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if (h_addr_list[i+1]) {
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fprintf(dst, "\n ");
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}
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j = 0;
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} else {
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if (h_addr_list[i+1]) {
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fprintf(dst, ", ");
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}
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}
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}
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fprintf(dst,"\n");
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return 0;
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}
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/* */
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/* gethostbyaddr wrapper */
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static struct hostent *
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lookup_by_name(const char *hostname)
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gethostbyaddr_wrapper(const char *address)
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{
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struct hostent *host;
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struct in_addr addr;
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host = gethostbyname(hostname);
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addr.s_addr = str_to_addr(address);
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return gethostbyaddr((char *) &addr, 4, AF_INET); /* IPv4 only for now */
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}
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/* print the results as nslookup would */
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static struct hostent *
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hostent_fprint(struct hostent *host, FILE *dst)
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{
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if (host) {
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fprintf(stdout, "Name: %s\n", host->h_name);
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addr_list_fprint(host->h_addr_list, stdout);
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fprintf(dst, "Name: %s\n", host->h_name);
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addr_list_fprint(host->h_addr_list, dst);
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} else {
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herror("crap");
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fprintf(dst, "*** %s\n", hstrerror(h_errno));
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}
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return host;
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}
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/* */
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static struct hostent *
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lookup_by_addr(const char *addr)
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{
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struct hostent *host;
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host = gethostbyaddr(addr, 4, AF_INET); /* IPv4 only for now */
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if (host) {
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fprintf(stdout, "Name: %s\n", host->h_name);
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addr_list_fprint(host->h_addr_list, stdout);
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} else {
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herror("crap");
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}
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return host;
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}
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/* */
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/* naive function to check whether char *s is an ip address */
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static int
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is_ip_address(const char *s)
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{
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@ -153,16 +169,20 @@ is_ip_address(const char *s)
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int
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nslookup_main(int argc, char **argv)
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{
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struct in_addr addr;
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struct hostent *host;
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if (argc < 2) {
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usage(nslookup_usage);
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}
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server_fprint(stdout);
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if (is_ip_address(argv[1])) {
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addr.s_addr = str_to_addr(argv[1]);
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lookup_by_addr((char *) &addr);
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host = gethostbyaddr_wrapper(argv[1]);
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} else {
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lookup_by_name(argv[1]);
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host = gethostbyname(argv[1]);
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}
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hostent_fprint(host, stdout);
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return 0;
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}
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/* $Id: nslookup.c,v 1.1 2000/01/29 12:59:01 beppu Exp $ */
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/* $Id: nslookup.c,v 1.2 2000/01/30 09:47:16 beppu Exp $ */
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