C:if it is a valid ipv4 address

ip-address.c

#include <stdio.h>
#include <string.h>

int is_valid_ipv4(const char *str) {
    int tmp = 0, dot = 0, digit = 0, i = 0;
    size_t len = strlen(str) + 1;
    while (i < len) {
        //printf("%s, %d\n", str, tmp);
        if (*str < 48 || *str > 57) {
            if (*str == '.' || *str == '\0') {
                if (tmp < 0 || tmp > 255) {
                    return 2;
                } else {
                    if (digit == 0) {
                        if (*str == '\0') {
                            return 5;
                        } else {
                            return 4;
                        }
                    } else {
                        tmp = 0;
                        digit = 0;
                        if (*str == '.') {
                            dot++;
                        }
                    }
                }
            } else {
                return 1;
            }
        } else {
            tmp = tmp*10 + (*str) - 48;
            digit++;
        }
        str++, i++;
    }
    if (dot < 1 || dot > 3) {
        return 3;
    }
    return 0;
}

int main(int argc, char *argv[]) {
    int i;
    for (i=1; i<argc; i++) {
        switch (is_valid_ipv4(argv[i])) {
            case 0:
                printf("\"%s\" is valid IPv4 address.\n", argv[i]);
                break;
            case 1:
                printf("Error: \"%s\" is invalid!\n", argv[i]);
                break;
            case 2:
                printf("Error: \"%s\" is out of range!\n", argv[i]);
                break;
            case 3:
                printf("Error: \".\" in \"%s\" are more or less than THREE!\n", argv[i]);
                break;
            case 4:
                printf("Error: one \".\" in \"%s\" is adjacent to another!\n", argv[i]);
                break;
            case 5:
                printf("Error: \"%s\" need more decimal!\n", argv[i]);
                break;
        }
    }
    return 0;
}