iOS - Get ARP table

Question

I am trying to build a network scanner. I know the procedure so I want to ping all available hosts in the network and then get the ARP table so I can map the MAC address for each IP. I Googled for ARP table but I didn't find any guide how to implement this feature. I also found these similar questions on Stack overflow:

Link1

Link2

The answer are unclear on how to implement the ARP feature. Is there any official guide for this one? Is Apple approving the ARP table feature?

Answer 1

UPDATE AFTER 10.2

Check the library here

I finally got it working so I will post the procedure in detail to save some time for other guys:

1. Go to Applications and right click on Xcode -> Show package contents and browse to: Developer ▸ Platforms ▸ MacOSX.platform ▸ Developer ▸ SDKs ▸ MacOSX10.10.sdk ▸ usr ▸ include. From "net" folder copy the route.h and if_types.h and from the "netinet" folder copy the if_ether.h into your Xcode project.
2. Then import the following .m and .h files:

MacFinder.h

#import <Foundation/Foundation.h>
#include <sys/param.h>
#include <sys/file.h>
#include <sys/socket.h>
#include <sys/sysctl.h>

#include <net/if.h>
#include <net/if_dl.h>
#include "if_types.h"

#if TARGET_IPHONE_SIMULATOR
#include <net/route.h>
#else
#include "route.h"
#endif

#include "if_ether.h"
#include <netinet/in.h>


#include <arpa/inet.h>

#include <err.h>
#include <errno.h>
#include <netdb.h>

#include <paths.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

@interface MacFinder : NSObject{

    int nflag;
}

-(NSString*) ip2mac: (char*)ip;

@end

MacFinder.m

#import "MacFinder.h"

@implementation MacFinder
-(NSString*) ip2mac: (char*)ip
{
    int  found_entry = 0;



    NSString *mAddr = nil;
    u_long addr = inet_addr(ip);
    int mib[6];
    size_t needed;
    char *host, *lim, *buf, *next;
    struct rt_msghdr *rtm;
    struct sockaddr_inarp *sin;
    struct sockaddr_dl *sdl;
    extern int h_errno;
    struct hostent *hp;

    mib[0] = CTL_NET;
    mib[1] = PF_ROUTE;
    mib[2] = 0;
    mib[3] = AF_INET;
    mib[4] = NET_RT_FLAGS;
    mib[5] = RTF_LLINFO;
    if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
        err(1, "route-sysctl-estimate");
    if ((buf = malloc(needed)) == NULL)
        err(1, "malloc");
    if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0)
        err(1, "actual retrieval of routing table");


    lim = buf + needed;
    for (next = buf; next < lim; next += rtm->rtm_msglen) {
        rtm = (struct rt_msghdr *)next;
        sin = (struct sockaddr_inarp *)(rtm + 1);
        sdl = (struct sockaddr_dl *)(sin + 1);
        if (addr) {
            if (addr != sin->sin_addr.s_addr)
                continue;
            found_entry = 1;
        }
        if (nflag == 0)
            hp = gethostbyaddr((caddr_t)&(sin->sin_addr),
                               sizeof sin->sin_addr, AF_INET);
        else
            hp = 0;
        if (hp)
            host = hp->h_name;
        else {
            host = "?";
            if (h_errno == TRY_AGAIN)
                nflag = 1;
        }



        if (sdl->sdl_alen) {

            u_char *cp = LLADDR(sdl);

            mAddr = [NSString stringWithFormat:@"%x:%x:%x:%x:%x:%x", cp[0], cp[1], cp[2], cp[3], cp[4], cp[5]];


            //  ether_print((u_char *)LLADDR(sdl));
        }
        else

            mAddr = nil;



    }


    if (found_entry == 0) {
        return nil;
    } else {
        return mAddr;
    }




}
@end

3. Then import the MacFinder.h file in your ViewController
4. Example how to use it for each host you want to find the MAC Address:

MacFinder *mc = [[MacFinder alloc]init]; NSString *mac = [mc ip2mac:"192.168.10.24"]; NSLog(@"Mac:%@",mac);

If you still having trouble here is tutorial and here the full working project (Including the necessary files)