ioctl(SIOCGIFCONF)

Hello,
I have a problem on my Suse 8.2 system: The ioctl(SIOCGIFCONF) call
returns only 127.0.0.1, not the IP-numbers of the NICs. I use the
openmosix-kernel 2.4.20. I need to get the ioctl working in order to
boot lam-mpi.

Any ideas?

andreas

(E-Mail Removed) (AW) wrote:
>Hello,
>I have a problem on my Suse 8.2 system: The ioctl(SIOCGIFCONF) call
>returns only 127.0.0.1, not the IP-numbers of the NICs. I use the
>openmosix-kernel 2.4.20. I need to get the ioctl working in order to
>boot lam-mpi.
>
>Any ideas?

Post some code showing what you are doing. The ideal thing
would be a small, complete, program which demonstrates your
problem. It should be something everyone can compile to see
what it does or doesn't do.

That said, here is a demo program which shows how to get
a variety of information about an interface.

/*
* display info about network interfaces
*/

#define _BSD_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <arpa/inet.h>

#define inaddrr(x) (*(struct in_addr *) &ifr->x[sizeof sa.sin_port])
#define IFRSIZE ((int)(size * sizeof (struct ifreq)))

static int
get_addr(int sock, char * ifname, struct sockaddr * ifaddr) {

struct ifreq *ifr;
struct ifreq ifrr;
struct sockaddr_in sa;

ifr = &ifrr;

ifrr.ifr_addr.sa_family = AF_INET;

strncpy(ifrr.ifr_name, ifname, sizeof(ifrr.ifr_name));

if (ioctl(sock, SIOCGIFADDR, ifr) < 0) {
printf("No %s interface.\n", ifname);
return -1;
}

*ifaddr = ifrr.ifr_addr;
printf("Address for %s: %s\n", ifname, inet_ntoa(inaddrr(ifr_addr.sa_data)));
return 0;
}

int main(void)
{
unsigned char *u;
int sockfd, size = 1;
struct ifreq *ifr;
struct ifconf ifc;
struct sockaddr_in sa;


if (0 > (sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP))) {
fprintf(stderr, "Cannot open socket.\n");
exit(EXIT_FAILURE);
}

ifc.ifc_len = IFRSIZE;
ifc.ifc_req = NULL;

do {
++size;
/* realloc buffer size until no overflow occurs */
if (NULL == (ifc.ifc_req = realloc(ifc.ifc_req, IFRSIZE))) {
fprintf(stderr, "Out of memory.\n");
exit(EXIT_FAILURE);
}
ifc.ifc_len = IFRSIZE;
if (ioctl(sockfd, SIOCGIFCONF, &ifc)) {
perror("ioctl SIOCFIFCONF");
exit(EXIT_FAILURE);
}
} while (IFRSIZE <= ifc.ifc_len);

/* this is an alternate way to get info... */
{
struct sockaddr ifa;
get_addr(sockfd, "ppp0", &ifa);
}

ifr = ifc.ifc_req;
for (;(char *) ifr < (char *) ifc.ifc_req + ifc.ifc_len; ++ifr) {

if (ifr->ifr_addr.sa_data == (ifr+1)->ifr_addr.sa_data) {
continue; /* duplicate, skip it */
}

if (ioctl(sockfd, SIOCGIFFLAGS, ifr)) {
continue; /* failed to get flags, skip it */
}

printf("Interface: %s\n", ifr->ifr_name);
printf("IP Address: %s\n", inet_ntoa(inaddrr(ifr_addr.sa_data)));

/*
This won't work on HP-UX 10.20 as there's no SIOCGIFHWADDR ioctl. You'll
need to use DLPI or the NETSTAT ioctl on /dev/lan0, etc (and you'll need
to be root to use the NETSTAT ioctl. Also this is deprecated and doesn't
work on 11.00).

On Digital Unix you can use the SIOCRPHYSADDR ioctl according to an old
utility I have. Also on SGI I think you need to use a raw socket, e.g. s
= socket(PF_RAW, SOCK_RAW, RAWPROTO_SNOOP)

Dave

From: David Peter <(E-Mail Removed)>
*/

if (0 == ioctl(sockfd, SIOCGIFHWADDR, ifr)) {

/* Select which hardware types to process.
*
* See list in system include file included from
* /usr/include/net/if_arp.h (For example, on
* Linux see file /usr/include/linux/if_arp.h to
* get the list.)
*/
switch (ifr->ifr_hwaddr.sa_family) {
default:
printf("\n");
continue;
case ARPHRD_NETROM: case ARPHRD_ETHER: case ARPHRD_PPP:
case ARPHRD_EETHER: case ARPHRD_IEEE802: break;
}

u = (unsigned char *) &ifr->ifr_addr.sa_data;

if (u[0] + u[1] + u[2] + u[3] + u[4] + u[5]) {
printf("HW Address: %2.2x.%2.2x.%2.2x.%2.2x.%2.2x.%2.2x\n",
u[0], u[1], u[2], u[3], u[4], u[5]);
}
}

if (0 == ioctl(sockfd, SIOCGIFNETMASK, ifr) &&
strcmp("255.255.255.255", inet_ntoa(inaddrr(ifr_addr.sa_data)))) {
printf("Netmask: %s\n", inet_ntoa(inaddrr(ifr_addr.sa_data)));
}

if (ifr->ifr_flags & IFF_BROADCAST) {
if (0 == ioctl(sockfd, SIOCGIFBRDADDR, ifr) &&
strcmp("0.0.0.0", inet_ntoa(inaddrr(ifr_addr.sa_data)))) {
printf("Broadcast: %s\n", inet_ntoa(inaddrr(ifr_addr.sa_data)));
}
}

if (0 == ioctl(sockfd, SIOCGIFMTU, ifr)) {
printf("MTU: %u\n", ifr->ifr_mtu);
}

if (0 == ioctl(sockfd, SIOCGIFMETRIC, ifr)) {
printf("Metric: %u\n", ifr->ifr_metric);
}
printf("\n");
}

close(sockfd);
return EXIT_SUCCESS;
}


--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) (E-Mail Removed)