nterface name is something like “eth0″ and the ip address of the interface can be retrieved using the ioctl function.
Here is a simple piece of code that demonstrates how :
Code
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#include <stdio.h> |
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#include <string.h> |
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#include <sys/types.h> |
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#include <sys/socket.h> |
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#include <sys/ioctl.h> |
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#include <netinet/in.h> |
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#include <net/if.h> |
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#include <unistd.h> |
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#include <arpa/inet.h> |
10 |
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int main() |
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{ |
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int fd; |
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struct ifreq ifr; |
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|
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char iface[] = "eth0"; |
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|
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fd = socket(AF_INET, SOCK_DGRAM, 0); |
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//Type of address to retrieve - IPv4 IP address |
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ifr.ifr_addr.sa_family = AF_INET; |
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//Copy the interface name in the ifreq structure |
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strncpy(ifr.ifr_name , iface , IFNAMSIZ-1); |
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ioctl(fd, SIOCGIFADDR, &ifr); |
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close(fd); |
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//display result |
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printf("%s - %s\n" , iface , inet_ntoa(( (struct sockaddr_in *)&ifr.ifr_addr )->sin_addr) ); |
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return 0; |
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} |
Output
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$ gcc ioctl.c && ./a.out |
2 |
eth0 - 192.168.0.6 |
The socket used can be a TCP socket (SOCK_STREAM) as well.
If you also need the netmask then use the SIOCGIFNETMASK value in ioctl like this :
1 |
#include <stdio.h> |
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#include <string.h> |
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#include <sys/socket.h> |
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#include <sys/ioctl.h> |
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#include <net/if.h> |
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#include <unistd.h> |
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#include <arpa/inet.h> |
8 |
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int main() |
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{ |
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int fd; |
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struct ifreq ifr; |
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|
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char iface[] = "eth0"; |
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|
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fd = socket(AF_INET, SOCK_DGRAM, 0); |
17 |
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//Type of address to retrieve - IPv4 IP address |
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ifr.ifr_addr.sa_family = AF_INET; |
20 |
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//Copy the interface name in the ifreq structure |
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strncpy(ifr.ifr_name , iface , IFNAMSIZ-1); |
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|
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//get the ip address |
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ioctl(fd, SIOCGIFADDR, &ifr); |
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|
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//display ip |
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printf("IP address of %s - %s\n" , iface , inet_ntoa(( (struct sockaddr_in *)&ifr.ifr_addr )->sin_addr) ); |
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|
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//get the netmask ip |
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ioctl(fd, SIOCGIFNETMASK, &ifr); |
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|
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//display netmask |
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printf("Netmask of %s - %s\n" , iface , inet_ntoa(( (struct sockaddr_in *)&ifr.ifr_addr )->sin_addr) ); |
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|
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close(fd); |
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|
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return 0; |
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} |
Output :
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$ gcc ioctl.c && ./a.out |
2 |
IP address of eth0 - 192.168.0.6 |
3 |
Netmask of eth0 - 255.255.255.0 |
