Linux C语言 检测IP冲突

分析一个基于C语言实现的IP冲突检测工具。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <getopt.h>
#include <arpa/inet.h>

#define dbg(fmt, args...) printf("\033[1m[ %s ] %03d: "fmt"\033[0m\n\r", __FUNCTION__, __LINE__, ##args)

#define IP_STR_LEN      (16)

typedef struct _NET_ {
    unsigned int ip;
    unsigned int mask;
} NET;

static int debug_on = 0;

static void usage(const char *program)
{
    if (NULL == program) {
        return;
    }

	printf("usage: %s [OPTION], check the ip1/mask1 and ip2/mask2 has conflict or not.\n"
            "\n"
			"  -h, --help\n      print this message\n"
			"  -d, --debug\n     print more message for debug\n"
			"  -i, --ip1         the first ip to check\n"
			"  -m, --mask1       the mask of first ip\n"
			"  -I, --ip2         the second ip to check\n"
			"  -M, --mask2       the mask of second ip\n",
            program);

    return;
}

static unsigned int mask_str_to_val(const char *mask)
{
    unsigned int a, b, c, d;
    if (sscanf(mask, "%u.%u.%u.%u", &a, &b, &c, &d) != 4) {
        dbg("invalid mask:%s", mask);
        return 0;
    }

    /*dbg("%u.%u.%u.%u", a, b, c, d);*/
    return (a << 24) + (b << 16) + (c << 8) + (d);
}

static unsigned int ip_str_to_val(const char *ip)
{
    struct in_addr s;
    if (!ip) {
        return 0;
    }

    inet_pton(AF_INET, ip, (void *)&s);
    return (unsigned int)ntohl(s.s_addr);
}

static int process_options(int argc, char * argv[], NET *net1, NET *net2)
{
    int c = 0;
    int option_index = 0;
    char ip_str[IP_STR_LEN] = {0};
    char mask_str[IP_STR_LEN] = {0};

    static const char *short_options = "hi:m:I:M:d";
    static const struct option long_options[] = {
        {"help", no_argument, 0, 'h'},
        {"debug", no_argument, 0, 'd'},
        {"ip1", no_argument, 0, 'i'},
        {"mask1", no_argument, 0, 'm'},
        {"ip2", no_argument, 0, 'I'},
        {"mask2", no_argument, 0, 'M'},
        {0,0,0,0},
    };

    for (;;) {
		c = getopt_long(argc, argv, short_options,
				long_options, &option_index);

		if (c == EOF) {
			break;
		}

        switch (c) {
        case 'h':
            usage(argv[0]);
			exit(0);
			break;
        case 'd':
            debug_on = 1;
			break;
        case 'i':
            net1->ip = ip_str_to_val(optarg);
			break;
		case 'm':
            net1->mask = mask_str_to_val(optarg);
            break;
		case 'I':
            net2->ip = ip_str_to_val(optarg);
            break;
		case 'M':
            net2->mask = mask_str_to_val(optarg);
            break;
        default:
            dbg("unknown param:%c", c);
            break;
        }
    }
    
    return 0;
}

static int check_conflict(NET *net1, NET *net2)
{
    unsigned int net1_min = net1->ip & net1->mask;
    unsigned int net1_max = net1_min + (~net1->mask);

    if (net1_min > net1_max) {
        dbg("net1_min(%u) > net1_max(%u)", net1_min, net1_max);
        return 1;
    }

    unsigned int net2_min = net2->ip & net2->mask;
    unsigned int net2_max = net2_min + ((~net2->mask));

    if (debug_on) {
        dbg("mask1:%u", ~(net1->mask));
        dbg("mask2:%u", ~(net2->mask));
        dbg("net1_min:%u, net1_max:%u", net1_min, net1_max);
        dbg("net2_min:%u, net2_max:%u", net2_min, net2_max);
    }

    if (net2_min > net2_max) {
        dbg("net2_min(%u) > net2_max(%u)", net2_min, net2_max);
        return 1;
    }

    if (net1_max < net2_min || net1_min > net2_max) {
        return 0;
    } else {
        system("touch /tmp/ip_conflict");
        return 1;
    }
}

int main(int argc, char *argv[])
{
    int conflict = 0;
    NET net1;
    NET net2;

    memset(&net1, 0, sizeof(NET));
    memset(&net2, 0, sizeof(NET));

    if (process_options(argc, argv, &net1, &net2) < 0) {
        return -1;
    }

    if (0 == net1.ip || 0 == net1.mask || 0 == net2.ip || 0 == net2.mask) {
        dbg("no valid net(%u/%u)(%u/%u)", net1.ip, net1.mask, net2.ip, net2.mask);
        return -1;
    }

    conflict = check_conflict(&net1, &net2);

    if (debug_on) {
        dbg("(%u/%u) VS (%u/%u), conflict:%d", net1.ip, net1.mask, net2.ip, net2.mask, conflict);
    }

    return conflict;
}