How to get the WIFI gateway address on the iPhone? [duplicate]

Add to your project route.h file from http://opensource.apple.com/source/xnu/xnu-1456.1.26/bsd/net/route.h

Create getgateway.h

int getdefaultgateway(in_addr_t * addr);

Create getgateway.c

#include <stdio.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <sys/sysctl.h>
#include "getgateway.h"

#include "TargetConditionals.h"
#if TARGET_IPHONE_SIMULATOR
    #include <net/route.h>
    #define TypeEN    "en1"
#else
    #include "route.h"
    #define TypeEN    "en0"
#endif

#include <net/if.h>
#include <string.h>

#define CTL_NET         4               /* network, see socket.h */


#if defined(BSD) || defined(__APPLE__)

#define ROUNDUP(a) \
((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))

int getdefaultgateway(in_addr_t * addr)
{
    int mib[] = {CTL_NET, PF_ROUTE, 0, AF_INET,
        NET_RT_FLAGS, RTF_GATEWAY};
    size_t l;
    char * buf, * p;
    struct rt_msghdr * rt;
    struct sockaddr * sa;
    struct sockaddr * sa_tab[RTAX_MAX];
    int i;
    int r = -1;
    if(sysctl(mib, sizeof(mib)/sizeof(int), 0, &l, 0, 0) < 0) {
        return -1;
    }
    if(l>0) {
        buf = malloc(l);
        if(sysctl(mib, sizeof(mib)/sizeof(int), buf, &l, 0, 0) < 0) {
            return -1;
        }
        for(p=buf; p<buf+l; p+=rt->rtm_msglen) {
            rt = (struct rt_msghdr *)p;
            sa = (struct sockaddr *)(rt + 1);
            for(i=0; i<RTAX_MAX; i++) {
                if(rt->rtm_addrs & (1 << i)) {
                    sa_tab[i] = sa;
                    sa = (struct sockaddr *)((char *)sa + ROUNDUP(sa->sa_len));
                } else {
                    sa_tab[i] = NULL;
                }
            }

            if( ((rt->rtm_addrs & (RTA_DST|RTA_GATEWAY)) == (RTA_DST|RTA_GATEWAY))
               && sa_tab[RTAX_DST]->sa_family == AF_INET
               && sa_tab[RTAX_GATEWAY]->sa_family == AF_INET) {


                if(((struct sockaddr_in *)sa_tab[RTAX_DST])->sin_addr.s_addr == 0) {
                        char ifName[128];
                        if_indextoname(rt->rtm_index,ifName);
                        if(strcmp(TypeEN,ifName)==0){
                            *addr = ((struct sockaddr_in *)(sa_tab[RTAX_GATEWAY]))->sin_addr.s_addr;
                                r = 0;                        
                        }
                }
            }
        }
        free(buf);
    }
    return r;
}
#endif

Through the following snippet, this example will be good work on the simulator and the devise.

#include "TargetConditionals.h"
#if TARGET_IPHONE_SIMULATOR
    #include <net/route.h>
    #define TypeEN    "en1"
#else
    #include "route.h"
    #define TypeEN    "en0"
#endif

Use this code in your Objective C project

#import "getgateway.h"
#import <arpa/inet.h>

- (NSString *)getGatewayIP {
    NSString *ipString = nil;
    struct in_addr gatewayaddr;
    int r = getdefaultgateway(&(gatewayaddr.s_addr));
    if(r >= 0) {
        ipString = [NSString stringWithFormat: @"%s",inet_ntoa(gatewayaddr)];
        NSLog(@"default gateway : %@", ipString );
    } else {
        NSLog(@"getdefaultgateway() failed");
    }

    return ipString;

}