系统解析保存多个缓存副本？

Question

我将systemd-resolved设置为调试模式，试图对此计算机(tcfe01)中的大量DNS查询进行故障排除。systemd-resolved似乎保存了多个缓存副本，一个用于全局范围(*/*)，另一个用于特定网络设备(eno1/*)。从日志中看，似乎只有全局范围(*/*)被缓存，而不是(eno1/*)。对于第一个查询，我们看到两个作用域的Cache miss，但对于后续的查询，我们得到了全局作用域的Positive cache hit，而设备作用域的Cache miss，最后每次都会访问DNS服务器。

这违背了缓存的全部目的，不仅损害了本地机器(tcfe01)上的性能，而且不必要地打击了DNS服务器。任何对这种行为的洞察力都会很有帮助。

Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Got DNS stub UDP query packet for id 14184
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Looking up RR for google.com IN A.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Switching to DNS server 192.168.10.25 for interface eno1.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Switching to system DNS server 192.168.10.25.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Cache miss for google.com IN A
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Transaction 48281 for <google.com IN A> scope dns on */*.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Using feature level UDP+EDNS0 for transaction 48281.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Using DNS server 192.168.10.25 for transaction 48281.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Sending query packet with id 48281.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Cache miss for google.com IN A
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Transaction 1213 for <google.com IN A> scope dns on eno1/*.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Using feature level UDP+EDNS0 for transaction 1213.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Using DNS server 192.168.10.25 for transaction 1213.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Sending query packet with id 1213.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Processing query...
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Processing incoming packet on transaction 48281. (rcode=SUCCESS)
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Verified we get a response at feature level UDP+EDNS0 from DNS server 192.168.10.25.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Added positive unauthenticated cache entry for google.com IN A 299s on */INET/192.168.10.25
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Transaction 48281 for <google.com IN A> on scope dns on */* now complete with <success> from network (unsigned).
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Freeing transaction 1213.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Sending response packet with id 14184 on interface 1/AF_INET.
Apr 23 16:45:34 tcfe01 systemd-resolved[26041]: Freeing transaction 48281.


Apr 23 16:45:45 tcfe01 systemd-resolved[26041]: Got DNS stub UDP query packet for id 50679
Apr 23 16:45:45 tcfe01 systemd-resolved[26041]: Looking up RR for google.com IN A.
Apr 23 16:45:45 tcfe01 systemd-resolved[26041]: Positive cache hit for google.com IN A
Apr 23 16:45:45 tcfe01 systemd-resolved[26041]: Transaction 51371 for <google.com IN A> on scope dns on */* now complete with <success> from cache (unsigned).
Apr 23 16:45:45 tcfe01 systemd-resolved[26041]: Cache miss for google.com IN A
Apr 23 16:45:45 tcfe01 systemd-resolved[26041]: Transaction 16504 for <google.com IN A> scope dns on eno1/*.
Apr 23 16:45:45 tcfe01 systemd-resolved[26041]: Using feature level UDP+EDNS0 for transaction 16504.
Apr 23 16:45:45 tcfe01 systemd-resolved[26041]: Using DNS server 192.168.10.25 for transaction 16504.
Apr 23 16:45:45 tcfe01 systemd-resolved[26041]: Sending query packet with id 16504.
Apr 23 16:45:45 tcfe01 systemd-resolved[26041]: Freeing transaction 51371.
Apr 23 16:45:45 tcfe01 systemd-resolved[26041]: Freeing transaction 16504.
Apr 23 16:45:45 tcfe01 systemd-resolved[26041]: Sending response packet with id 50679 on interface 1/AF_INET.
Apr 23 16:45:45 tcfe01 systemd-resolved[26041]: Processing query...


Apr 23 16:45:48 tcfe01 systemd-resolved[26041]: Got DNS stub UDP query packet for id 50950
Apr 23 16:45:48 tcfe01 systemd-resolved[26041]: Looking up RR for google.com IN A.
Apr 23 16:45:48 tcfe01 systemd-resolved[26041]: Positive cache hit for google.com IN A
Apr 23 16:45:48 tcfe01 systemd-resolved[26041]: Transaction 27482 for <google.com IN A> on scope dns on */* now complete with <success> from cache (unsigned).
Apr 23 16:45:48 tcfe01 systemd-resolved[26041]: Cache miss for google.com IN A
Apr 23 16:45:48 tcfe01 systemd-resolved[26041]: Transaction 24663 for <google.com IN A> scope dns on eno1/*.
Apr 23 16:45:48 tcfe01 systemd-resolved[26041]: Using feature level UDP+EDNS0 for transaction 24663.
Apr 23 16:45:48 tcfe01 systemd-resolved[26041]: Using DNS server 192.168.10.25 for transaction 24663.
Apr 23 16:45:48 tcfe01 systemd-resolved[26041]: Sending query packet with id 24663.
Apr 23 16:45:48 tcfe01 systemd-resolved[26041]: Freeing transaction 27482.
Apr 23 16:45:48 tcfe01 systemd-resolved[26041]: Freeing transaction 24663.
Apr 23 16:45:48 tcfe01 systemd-resolved[26041]: Sending response packet with id 50950 on interface 1/AF_INET.
Apr 23 16:45:48 tcfe01 systemd-resolved[26041]: Processing query...

Answer 1

我在这里回答我自己的问题，因为我所面临的问题现在已经解决了。谢谢你为我指出正确的方向。因此，systemd-resolve --status显示DNS服务器配置为全局服务器以及每个链接设置。这导致每个查询被解析两次。我将全局DNS配置为最终的DNS，将条目Domains=~.添加到/etc/systemd/resolved.conf文件中，并重新启动systemd解析.systemd。

正如@bac0n所提到的，我本可以通过systemd-网络设置对我的特定链接进行同样的操作。由于我使用的是netplan，而不是直接配置systemd，所以我认为我必须使用netplan来进行这些设置。我很难找到网络计划的选择。所以我现在就不谈这个了。