getifaddrs

[ecureuil]

Hi

I'm trying to get interfaces' list and infos with getifaddrs().
The ifa_data struct should contain all needed information, but 
this is a NULL pointer for IPv4 interfaces. Why ?

a sample output for my ethernet card :

   ed0 (        6.3.6.0) : UP, AF_INET6 MTU=1500   (struct ifa_data)
   ed0 (       10.0.0.1) : UP MTU=1500   (struct ifa_data is a null pointer)


BTW, there is always 2 nodes for each interface, even if INET6 is not
enabled in the kernel. is it normal ?

thanks (see the source attached)

-- 
ecureuil <[EMAIL PROTECTED]>

/* ecureuil <[EMAIL PROTECTED]>
   get interface information
 */

#include <stdio.h>
#include <string.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>
#include <unistd.h>
#include <ifaddrs.h>

int 
main(int argc, char **argv)
{
        struct ifaddrs          *ifap, *ifa;
        struct sockaddr_in      *sa;
        int                     fd;
        struct ifreq            ifr;
        char                    ifstraddr[16];
        sa_family_t             fam;

        if (getifaddrs(&ifap) < 0) {
                perror("getifaddrs");
                return -1;
        }

        for (ifa = ifap; ifa; ifa = ifa->ifa_next) {

                printf("%6s ", ifa->ifa_name);

                /* get if address */
                sa = (struct sockaddr_in *) ifa->ifa_addr;
                strncpy(ifstraddr, inet_ntoa(sa->sin_addr), 16);
                printf("(%15s) : ",ifstraddr);

                if (!(ifa->ifa_flags & IFF_UP)) printf("DOWN");
                else printf("UP");

                if (ifa->ifa_flags & IFF_PROMISC) printf(", PROMISCUOUS");

                if (ifa->ifa_addr->sa_family & AF_INET6) printf(", AF_INET6");

                /* get if mtu */
                fam = ifa->ifa_addr->sa_family == AF_LINK ? AF_INET : 
ifa->ifa_addr->sa_family;
                if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0 ) {
                        perror("[get_if_name] socket(AF_INET, SOCK_DGRAM, 0)");
                        return -1;
                }
                
                strncpy(ifr.ifr_name,ifa->ifa_name,IFNAMSIZ);           

                if (ioctl(fd, SIOCGIFMTU, &ifr) < 0 ) {
                        perror("ioctl");
                        return -1;
                } else {
                        printf(" MTU=%d   ",ifr.ifr_mtu);
                }

                close(fd);
                
                if(ifa->ifa_data) printf("(struct ifa_data)\n");
                else printf("(struct ifa_data is a null pointer)\n");
                
        }               
                freeifaddrs(ifap);
                return 0;
}