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Old 12-06-2011, 05:32 AM   #1
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Registered: Dec 2011
Posts: 3

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Problem with inet_pton()

hello every body,
My name is roxy and i am from brazil.I want to expand IPv6 address using inet_pton().After that increment the address by 1 using C code.If my address is - 1234:12::ffff then after expand it will be 1234:0012:0000:0000:0000:0000:0000:ffff
When I increment the address it will display - 1234:0012:0000:0000:0000:0000:0001:0000
Whenever it will reaches ffff it just put 0x0000 and increment the next value by 1.
I already done some code part.Please help me in this matter.

#include "stdafx.h"
#include "string.h"
#include "stdlib.h"
#include "conio.h"
#include "arpa/inet.h"
#include "inet/ip6.h"

int _tmain(int argc, char argv[])

struct in6_addr {
unsigned char s6_addr[16]; // IPv6 address
struct in6_addr ipv6;
char str[]="abcd:1234::ffff";
printf("%s is %0llu(IPv6)\n",str,ipv6.s6_addr);


return 0;

Old 12-06-2011, 11:56 AM   #2
Nominal Animal
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Registered: Dec 2010
Location: Finland
Distribution: Xubuntu, CentOS, LFS
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struct in6_addr has a single member, an array of 16 bytes named s6_addr. It is in network byte order, i.e. most significant byte first. I don't know why you redefined the structure -- I'd just use #include <arpa/inet.h>

Increase the last value in the array. If it turns zero, increase the previous value; if that turns zero, increase the one before that too, and so on. Finally, use inet_ntop() to convert the modified address back to a string.
#include <arpa/inet.h>
#include <stdio.h>

struct in6_addr  ipv6;
char             addrbuf[INET6_ADDRSTRLEN]; /* 46 */
const char      *addrstr;
int              i;

if (inet_pton(AF_INET6, address_string, &ipv6) == 1) {

    /* Increase address by one */
    /* Carry over to more significant bytes */
    i = 15;
    while (i > 0 && !ipv6.s6_addr[i--])

    /* Convert back to a string and print. */
    if ((addrstr = inet_ntop(AF_INET6, &ipv6, addrbuf, sizeof(addrbuf))))
        printf("%s\n", addrstr);
1 members found this post helpful.
Old 12-07-2011, 02:01 AM   #3
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Registered: Dec 2011
Posts: 3

Original Poster
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Hi nominal,

Thank you very much for your reply.

Last edited by roxy99; 12-07-2011 at 04:47 AM.


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