how to get IPv6 address using ioctl() SIOCGIFADDR

ashok449 · 05-19-2010, 04:46 AM

Hello All,

I have retrieved IPv4 address successfully using

Code:

struct ifreq ifr;
 fd = socket(AF_INET, SOCK_DGRAM, 0);
 ifr.ifr_addr.sa_family = AF_INET;
ioctl(fd, SIOCGIFADDR, &ifr)

for IPv6 address I tried

Code:

struct ifreq ifr;
 fd = socket(AF_INET6, SOCK_DGRAM, 0);
ifr.ifr_addr.sa_family = AF_INET6;
ioctl(fd, SIOCGIFADDR, &ifr)

but ioctl() returning error here, please suggest

Regards,
Ashok

climbingdrummer · 06-08-2010, 12:05 PM

Any chance you've figured this out? I'm having the same problem. I'm trying to use ioctl to find my ipv6 addresses but I'm only getting back ipv4. I'm using kernel 2.6.18

ashok449 · 06-09-2010, 04:33 AM

Hello,

I tried for some time and not succeeded yet

any how here is the code where I've reached regarding this issue.

Code:

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>
   int main(void)
   {
     int                sfd, i;
  struct in6_ifreq {
        struct in6_addr ifr6_addr;
        uint32_t        ifr6_prefixlen;
        int             ifr6_ifindex;
};
  struct in6_ifreq       ifr;
     struct sockaddr_in6 *sin = (struct sockaddr_in6 *) &ifr.ifr6_addr;

     memset(&ifr, 0, sizeof ifr);

     if (0 > (sfd = socket(AF_INET6, SOCK_DGRAM, 0))) {
       perror("socket()");
       exit(1);
     }

   //  strncpy(ifr.ifr_name, "eth0", IFNAMSIZ -1);
     sin->sin6_family = AF_INET6;

     if (0 == ioctl(sfd, SIOCGIFADDR, &ifr)) {

         //printf("%s: %s\n", ifr.ifr_name, inet_ntoa(sin->sin6_addr));

        }
     else
        printf("ioctl() ---error\n");


char str[INET6_ADDRSTRLEN];
printf("ntop ret= %s\n",inet_ntop(AF_INET6, &(((struct sockaddr_in6 *)sin)->sin6_addr), str, INET6_ADDRSTRLEN));

printf("%s\n", str);


     return 0;
   }

please let me know if there is a break through.

Thanks
Ashok

climbingdrummer · 06-09-2010, 10:43 AM

I found this site which may be useful to you. I could not get it to print ipv6 addresses though.

http://www.adamrisi.com/?p=84

climbingdrummer · 06-09-2010, 05:31 PM

If you don't need to use the ioctl call, you can use the method getifaddrs.

Code:

#include <sys/types.h>
#include <sys/socket.h>
#include <ifaddrs.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <string.h>
#include <vector>
#include <string>
#include <iostream>
#include <netinet/in.h>
#include <net/if.h>

using namespace std;
 
std::vector<std::string> listAddresses();
void printAddresses(const std::vector<std::string>& addresses);

int main(int argc, char* argv[], char* envp[])
{
    addresses = listAddresses();
    printAddresses(addresses);
    return 0;
}

void printAddresses(const vector<string>& addresses) {
    for(vector<string>::const_iterator it=addresses.begin(); it!=addresses.end(); ++it) {
        string address = *it;
	cout << address << endl;
    }
}

vector<string> listAddresses()
{
    vector<string> addresses;

    struct ifaddrs *ifa=NULL,*ifEntry=NULL;
    void *addPtr = NULL;
    int rc = 0;
    char addressBuffer[INET6_ADDRSTRLEN];

    rc = getifaddrs(&ifa);
    if (rc==0) {
        for(ifEntry=ifa; ifEntry!=NULL; ifEntry=ifEntry->ifa_next) {
	    if(ifEntry->ifa_addr->sa_data == NULL) {
                continue;
	    }
            if(ifEntry->ifa_addr->sa_family==AF_INET) {
                 addPtr = &((struct sockaddr_in *)ifEntry->ifa_addr)->sin_addr;
            } else if(ifEntry->ifa_addr->sa_family==AF_INET6) {
                 addPtr = &((struct sockaddr_in6 *)ifEntry->ifa_addr)->sin6_addr;
            } else {
                //It isn't IPv4 or IPv6
		continue;
	    }

            const char *a = inet_ntop(ifEntry->ifa_addr->sa_family,
                          addPtr,
                          addressBuffer,
                          sizeof(addressBuffer));
	    if(a != NULL) {
                addresses.push_back(string(a));
 	    }
        }
    }
    freeifaddrs(ifa);

    return addresses;
}

ashok449 · 06-11-2010, 04:35 AM

Thanks for the Post, Its working.

ssitaram · 01-03-2012, 11:39 PM

use this method instead of ioctl it will work. Hope this helps

/******************************************************************
* FUNCTION: my_get_ipv6_ifindex_from_addr
*
* DESCRIPTION: this function returns ifindex for a given IPV6 address string
*
* PARAMETERS: 'ipv6_addr_str' char string in the format given by inet_ntop()
*
* RETURN VALUE: On Success return value is greater than Zero,
* Zero or Negetive on Error.
*******************************************************************/
int my_get_ipv6_ifindex_from_addr(char *ipv6_addr_str)
{
struct ifaddrs *if_addr, *ifap;
int family, res;
char host_id[NI_MAXHOST], *host_addr;
int ifcount;
int ifindex_matched = -1;

if (getifaddrs(&if_addr) == -1)
{
perror("getif_addrs");
return(ERROR);
}
ifcount = 0;
for (ifap = if_addr; ifap != NULL; ifap = ifap->ifa_next)
{
if (ifap->ifa_addr == NULL)
{
ifcount++;
continue;
}

family = ifap->ifa_addr->sa_family;
if (family == AF_INET6)
{
res = getnameinfo(ifap->ifa_addr, sizeof(struct sockaddr_in6),
host_id, NI_MAXHOST, NULL, 0, NI_NUMERICHOST);
if (res != 0)
{ /* failure to get IPv6 address */

continue;
}
host_addr = strtok(host_id, "%");
if ((strncmp(host_id, ipv6_addr_str, INET6_ADDRSTRLEN)) == 0)
{
ifindex_matched = if_nametoindex(ifap->ifa_name);
break;
}
ifcount++;
}
}

return (ifindex_matched);
}