>Hello
>I would like to know if there is a way to know my ip address of each
>interface from a C program, if them are up or down...
>Of course, I can do it scanningf the output of "ifconfig", (more
>concretelly "ifconfig ppp0 | grep inetaddr"), but it would be great if
>exists the possibility of reading a structure with this information with a
>system call, just like sysinfo allows me to know how many free memory I
>have, for example.
>I have looked for such a function, but I havent found it. (I also have
>tried to look at the ifconfig code for a hint, but for me it is too
>complicated).
/* 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;
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 <dave.pe...@eu.citrix.com>
*/
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;
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