Python使用ipaddress库高效遍历匹配后缀的IPv6地址的实现方法

核心问题 #

• 原有方案的逻辑是先遍历网段内所有地址再做后缀匹配，/64的IPv6网段包含1844亿亿个地址，遍历完全不可行，效率极低。
• 优化核心思路是完全避免遍历，直接通过位运算构造符合后缀要求的IP地址。

实现思路 #

1. 先将输入的后缀转换为完整展开的IP字符串的后缀，再计算该后缀对应的二进制位数、以及后缀的整数值
2. 计算步长：step = 1 << 后缀位数，也就是每次地址递增的步长刚好覆盖后缀的所有位，保证每次生成的地址后缀都符合要求
3. 用网段的网络地址整数值，加上后缀整数值得到第一个符合要求的地址，之后每次加步长即可批量生成所有符合要求的地址

优化后代码 #

import ipaddress
from itertools import islice

def suffix_to_mask_and_value(ip_version, suffix):
    # 构造对应版本的全0展开地址，替换后缀得到样例地址
    if ip_version == 4:
        dummy = ipaddress.IPv4Address('0.0.0.0').exploded
        suffix_len = len(suffix)
        sample_addr = dummy[:-suffix_len] + suffix
        sample_ip = ipaddress.IPv4Address(sample_addr)
        # 计算后缀占用的二进制位数
        mask = 0
        for i in range(32):
            bit_val = 1 << i
            if (sample_ip._ip & bit_val) == (0 & bit_val):
                break
            mask +=1
        return mask, sample_ip._ip & ((1 << mask) - 1)
    else:
        dummy = ipaddress.IPv6Address('::').exploded
        suffix_len = len(suffix)
        sample_addr = dummy[:-suffix_len] + suffix
        sample_ip = ipaddress.IPv6Address(sample_addr)
        mask = 0
        for i in range(128):
            bit_val = 1 << i
            if (sample_ip._ip & bit_val) == (0 & bit_val):
                break
            mask +=1
        return mask, sample_ip._ip & ((1 << mask) - 1)

for address, suffix in zip(['10.10.0.0/16','2A00:7E40:F020::/64'],['.1',':00FF:FE00:0003']):
    print('===============')
    network = ipaddress.ip_network(address)
    print(f'{network.num_addresses} addresses available')
    print(f'suffix {suffix}')
    print('===============')
    suffix_bit_len, suffix_val = suffix_to_mask_and_value(network.version, suffix)
    step = 1 << suffix_bit_len
    first_ip = network.network_address._ip | suffix_val
    max_ip = network.broadcast_address._ip
    current = first_ip
    # 输出前2个匹配地址
    for _ in range(2):
        if current > max_ip:
            break
        print(ipaddress.ip_address(current))
        current += step

运行效果 #

===============
65536 addresses available
suffix .1
===============
10.10.0.1
10.10.1.1
===============
18446744073709551616 addresses available
suffix :00FF:FE00:0003
===============
2a00:7e40:f020::ff:fe00:3
2a00:7e40:f020:1::ff:fe00:3

无需遍历整个网段，不管多大的IPv6网段都可以瞬间返回结果。

内容的提问来源于stack exchange，提问作者rockandska