#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdarg.h>

#include <errno.h>
#include <string.h>
#include <ctype.h>

#include <sys/socket.h>
#include <netinet/in.h>
#include <linux/if.h>
#include <linux/sockios.h>
#include <arpa/inet.h>
#include <linux/route.h>

static void die(const char *fmt, ...)
{
    va_list p;

    va_start(p, fmt);
    fprintf(stderr,"error(%s): ", strerror(errno));
    fprintf(stderr, fmt, p);
    va_end(p);
    exit(-1);
}

static inline void init_sockaddr_in(struct sockaddr_in *sin, const char *addr)
{
	sin->sin_family = AF_INET;
	sin->sin_port = 0;
	sin->sin_addr.s_addr = inet_addr(addr);
}

#define ADVANCE(argc, argv) do { argc--, argv++; } while(0)
#define EXPECT_NEXT(argc, argv) do {        \
    ADVANCE(argc, argv);                    \
	if (0 == argc) {  						\
		errno = EINVAL;                     \
		die("expecting one more argument"); \
	}                                       \
} while(0)		

/* current support the following routing entries */
/* route add default dev wlan0 */
/* route add default gw 192.168.20.1 dev wlan0 */
/* route add net 192.168.1.1 netmask 255.255.255.0 gw 172.24.192.10 */

int route_main(int argc, char *argv[])
{
    struct ifreq ifr;
    int s,i;
    struct rtentry rt;
    struct sockaddr_in ina;
   
    if (!argc)
        return 0;

    strncpy(ifr.ifr_name, argv[0], IFNAMSIZ);
    ifr.ifr_name[IFNAMSIZ-1] = 0;
    ADVANCE(argc, argv);

    if ((s = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        die("cannot open control socket\n");
    }

    while(argc > 0){
        if (!strcmp(argv[0], "add")) {
            EXPECT_NEXT(argc, argv);
            if (!strcmp(argv[0], "default")) {
                EXPECT_NEXT(argc, argv);
                memset((char *) &rt, 0, sizeof(struct rtentry));
                rt.rt_dst.sa_family = AF_INET;	
                if(!strcmp(argv[0], "dev")) {
                    EXPECT_NEXT(argc, argv);
                    rt.rt_flags = RTF_UP | RTF_HOST;
                    rt.rt_dev = argv[0];
                    if (ioctl(s, SIOCADDRT, &rt) < 0)
                        die("SIOCADDRT\n");
                } else if (!strcmp(argv[0], "gw")) {
                    EXPECT_NEXT(argc, argv);
                    rt.rt_flags = RTF_UP | RTF_GATEWAY;
                    init_sockaddr_in((struct sockaddr_in *)&(rt.rt_genmask), "0.0.0.0");
                    if(isdigit(argv[0][0])) {
                        init_sockaddr_in((struct sockaddr_in *)&(rt.rt_gateway), argv[0]);
                    } else {
                        die("expecting an IP address for parameter \"gw\"\n");
                    }
                    EXPECT_NEXT(argc, argv);
                    if (!strcmp(argv[0], "dev")) {
                        EXPECT_NEXT(argc, argv);
                        rt.rt_dev = argv[0];
                        if (ioctl(s, SIOCADDRT, &rt) < 0) {
                            die("SIOCADDRT\n");
                        }
                    }
                }
            } else {
                char keywords[3][10] = { "-net", "netmask", "gw" };
                struct sockaddr_in *paddr[3] = { &rt.rt_dst, &rt.rt_genmask, &rt.rt_gateway };
                int k = 0;

                memset((char *) &rt, 0, sizeof(struct rtentry));
                rt.rt_flags = RTF_UP | RTF_GATEWAY;
                do {
                     if (!strcmp(argv[0], keywords[k])) {
                         EXPECT_NEXT(argc, argv);
                         if (isdigit(argv[0][0])) {
                             init_sockaddr_in(paddr[k], argv[0]);
                         } else {
                            die("expecting an IP/MASK address for parameter %s\n", keywords[k]);
                         }
                     if (k < 2)
                         EXPECT_NEXT(argc, argv);
                     } else {
                         die("expecting keyword(s)\n");
                     }
                 } while (++k < 3);

                if (ioctl(s, SIOCADDRT, &rt) < 0) {
                    die("SIOCADDRT\n");
                }
            }
        }
        ADVANCE(argc, argv);
    }

    return 0;
}