IPv6地址用冒号和16进制数表示,其中遇到连续的0可以作省略处理,如2001:0:0:0:0:0:0:1可以写成2001::1,这样对于书写很方便,但是带来一个额外的问题:两个地址比较的时候不能像IPv4那样调用字符串比较函数进行比较。本文通过比较两个IPv6地址的网络字节序来判断是否相等。
#include <stdio.h> #include <arpa/inet.h> int ipv6_equal(char *addr1, char *addr2) { int ret = -1; int i = 0; unsigned char n_addr1[16] = {-1}; unsigned char n_addr2[16] = {-1}; if (!addr1) { printf("addr1 is NULL\n"); return -1; } if (!addr2) { printf("addr2 is NULL\n"); return -1; } ret = inet_pton(AF_INET6, addr1, &(n_addr1)); if (ret <= 0 ) { if (ret == 0) { printf("addr1: Invalid IPv6 address\n"); } return -1; } ret = inet_pton(AF_INET6, addr2, &(n_addr2)); if (ret <=0 ) { if (ret == 0) { printf("addr2: Invalid IPv6 address\n"); } return -1; } for (i = 0; i < 16; i++) { //printf("i: %d, addr1: %u, addr2: %u\n", i, n_addr1[i], n_addr2[i]); if (n_addr1[i] != n_addr2[i]) { return 1; } } return 0; } int main(void) { if (ipv6_equal("2001::1", "2001::1") == 0) { printf("test: 2001::1 equal 2001::1\n"); } if (ipv6_equal("2001:0:0:0:0:0:0:1", "2001::1") == 0) { printf("test: 2001:0:0:0:0:0:0:1 equal 2001::1\n"); } if (ipv6_equal("2001::1", "2001::4") == 1) { printf("test: 2001::1 not equal 2001::4\n"); } if (ipv6_equal("2001:::1", "2001::4") == -1) { printf("test: Invalid address\n"); } return 0; }
test: 2001::1 equal 2001::1
test: 2001:0:0:0:0:0:0:1 equal 2001::1
test: 2001::1 not equal 2001::4
addr1: Invalid IPv6 address
test: Invalid address