dnsmasq strickorder分析

dnsmasq的strickorder使代理dns服务器向上游请求时执行不同的行为：

16:42:15.430429 IP 192.168.166.122.53330 > 192.168.99.1.53: 6833+ A? www.baidu.com. (31)
16:42:16.422702 IP 192.168.166.122.53330 > 192.168.88.1.53: 6833+ A? www.baidu.com. (31)
16:42:17.422713 IP 192.168.166.122.53330 > 192.168.166.1.53: 6833+ A? www.baidu.com. (31)
16:42:18.030365 IP 192.168.166.1.53 > 192.168.166.122.53330: 6833 3/0/0 CNAME www.a.shifen.com., A 110.242.68.3, A 110.242.68.4 (90)
16:45:37.440278 IP 192.168.166.122.17293 > 192.168.99.1.53: 39402+ A? www.baidu.com. (31)
16:45:38.439595 IP 192.168.166.122.17293 > 192.168.88.1.53: 39402+ A? www.baidu.com. (31)
16:45:39.453443 IP 192.168.166.122.17293 > 192.168.166.1.53: 39402+ A? www.baidu.com. (31)
16:45:39.482043 IP 192.168.166.1.53 > 192.168.166.122.17293: 39402 3/0/0 CNAME www.a.shifen.com., A 110.242.68.3, A 110.242.68.4 (90)

当启用strict order时，dns每次都遍历一下dns列表

16:51:20.668260 IP 192.168.166.122.45778 > 192.168.99.1.53: 7173+ A? github.com. (28)
16:51:20.668535 IP 192.168.166.122.45778 > 192.168.88.1.53: 7173+ A? github.com. (28)
16:51:20.668877 IP 192.168.166.122.45778 > 192.168.166.1.53: 7173+ A? github.com. (28)
16:51:20.743899 IP 192.168.166.1.53 > 192.168.166.122.45778: 7173 1/0/0 A 20.205.243.166 (44)
16:52:52.536542 IP 192.168.166.122.4479 > 192.168.166.1.53: 3714+ A? github.com. (28)
16:52:52.620581 IP 192.168.166.1.53 > 192.168.166.122.4479: 3714 1/0/0 A 20.205.243.166 (44)

当不启用strict order，则dns请求使用最后一次成功的请求