Re: Getting local subnet mask

rich kubota

#include <stdio.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <net/if.h>

#include <netinet/in.h>

#include <ifaddrs.h>

int main (int argc, const char * argv[]) {

// insert code here...

int result;

struct ifaddrs *ifbase, *ifiterator;

result = getifaddrs(&ifbase);

ifiterator = ifbase;

while (!result && (ifiterator != NULL))

{

if (ifiterator->ifa_addr->sa_family == AF_INET)

{

struct sockaddr *saddr, *netmask, *daddr;

saddr = ifiterator->ifa_addr;

netmask = ifiterator->ifa_netmask;

daddr = ifiterator->ifa_dstaddr;

// we've found an entry for the IP address

struct sockaddr_in *iaddr;

char addrstr[64];

iaddr = (struct sockaddr_in *)saddr;

inet_ntop(saddr->sa_family, &iaddr->sin_addr, addrstr, sizeof(addrstr));

fprintf(stderr, "ipv4 enet interface name %s, source IP addr %s ", ifiterator->ifa_name, addrstr);

iaddr = (struct sockaddr_in *)netmask;

if (iaddr)

{

inet_ntop(saddr->sa_family, &iaddr->sin_addr, addrstr, sizeof(addrstr));

fprintf(stderr, "netmask IP addr %s ", addrstr);

}

iaddr = (struct sockaddr_in *)daddr;

if (iaddr)

{

inet_ntop(saddr->sa_family, &iaddr->sin_addr, addrstr, sizeof(addrstr));

fprintf(stderr, "dest/broadcast IP addr %s.\n\n", addrstr);

}

else if (ifiterator->ifa_addr->sa_family == AF_INET6)

{

// we've found an entry for the IP address

struct sockaddr_in6 *iaddr6 = (struct sockaddr_in6 *)ifiterator->ifa_addr;

char addrstr[256];

inet_ntop(ifiterator->ifa_addr->sa_family, iaddr6, addrstr, sizeof(addrstr));

fprintf(stderr, "ipv6 enet interface name %s, source IP addr %s \n\n", ifiterator->ifa_name, addrstr);

}

ifiterator = ifiterator->ifa_next;

}

return 0;

}

On Feb 28, 2008, at 4:54 PM, Hamish Allan wrote:

Hi,

Is there a way to programmatically discover a machine's subnet mask?

I can see how this might be done using AppleScript to query System
Preferences but I'm hoping for something a bit more portable than that
(yes I know this is a Mac list but I think some members have wider
expertise. Also, the only 3 results for mailing lists returned from
googling "network programming mailing list" are for this one!)

Preferably in cross-platform Python, but beggars can't be choosers :)

Hamish
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References:
	>Getting local subnet mask (From: "Hamish Allan" <email@hidden>)