今天 DNS 停止解析。我仍然可以通过 IP 地址 ping 互联网，但没有解析任何域名。
我试过了
- 重启已解决
- 编辑 solved 的配置文件：禁用 DNSSec，手动输入名称服务器
- 重启机器
- 禁用防火墙
日志中出现了一些内容Using degraded feature set，不确定是否相关。
有什么想法可以修复该问题并再次进行 DNS 解析吗？
$ IP 地址
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ens36: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 00:0c:29:6c:c8:a3 brd ff:ff:ff:ff:ff:ff
altname enp2s4
inet 192.168.79.129/24 brd 192.168.79.255 scope global dynamic noprefixroute ens36
valid_lft 1248sec preferred_lft 1248sec
$ ip 路由
default via 192.168.79.2 dev ens36 proto dhcp metric 20100
169.254.0.0/16 dev ens36 scope link metric 1000
192.168.79.0/24 dev ens36 proto kernel scope link src 192.168.79.129 metric 100
$ ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=128 time=39.0 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=128 time=32.4 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=128 time=56.9 ms
64 bytes from 8.8.8.8: icmp_seq=4 ttl=128 time=33.9 ms
64 bytes from 8.8.8.8: icmp_seq=5 ttl=128 time=38.8 ms
--- 8.8.8.8 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4006ms
rtt min/avg/max/mdev = 32.356/40.182/56.881/8.757 ms
$ pingwww.google.com
ping: www.google.com: Temporary failure in name resolution
$ nslookupwww.google.com
;; communications error to 8.8.8.8#53: timed out
;; communications error to 8.8.8.8#53: timed out
;; communications error to 8.8.8.8#53: timed out
;; no servers could be reached
$ resolvectl 状态
Global
Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: foreign
DNS Servers: 1.1.1.1
Fallback DNS Servers: 8.8.8.8
Link 2 (ens36)
Current Scopes: DNS
Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 8.8.8.8
DNS Servers: 8.8.8.8 9.9.9.9
$ journalctl
Mar 11 16:21:08 ubuntu systemd-resolved[3428]: Using degraded feature set UDP instead of UDP+EDNS0 for DNS server 1.1.1.1.
Mar 11 16:21:14 ubuntu systemd-resolved[3428]: Using degraded feature set UDP instead of UDP+EDNS0 for DNS server 9.9.9.9.
Mar 11 16:21:19 ubuntu systemd-resolved[3428]: Using degraded feature set UDP instead of UDP+EDNS0 for DNS server 192.168.79.2.
Mar 11 16:21:56 ubuntu systemd-resolved[3428]: Using degraded feature set TCP instead of UDP for DNS server 1.1.1.1.
Mar 11 16:22:06 ubuntu systemd-resolved[3428]: Using degraded feature set TCP instead of UDP for DNS server 9.9.9.9.
Mar 11 16:22:16 ubuntu systemd-resolved[3428]: Using degraded feature set TCP instead of UDP for DNS server 192.168.79.2.
$ nc -v -u -z -w 3 8.8.8.8 53-53
Connection to 8.8.8.8 53 port [udp/domain] succeeded!
$ nc -v -u -z -w 3 9.9.9.9 53-53
Connection to 9.9.9.9 53 port [udp/domain] succeeded!
$ nc -v -u -z -w 3 1.1.1.1 53-53
Connection to 1.1.1.1 53 port [udp/domain] succeeded!
$ nc -v -u -z -w 3 192.168.79.2 53-53
Connection to 192.168.79.2 53 port [udp/domain] succeeded!
$ ufw 状态
Status: inactive
$ cat /etc/systemd/resolved.conf
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation; either version 2.1 of the License, or (at your option)
# any later version.
#
# Entries in this file show the compile time defaults. Local configuration
# should be created by either modifying this file, or by creating "drop-ins" in
# the resolved.conf.d/ subdirectory. The latter is generally recommended.
# Defaults can be restored by simply deleting this file and all drop-ins.
#
# Use 'systemd-analyze cat-config systemd/resolved.conf' to display the full config.
#
# See resolved.conf(5) for details.
[Resolve]
# Some examples of DNS servers which may be used for DNS= and FallbackDNS=:
# Cloudflare: 1.1.1.1#cloudflare-dns.com 1.0.0.1#cloudflare-dns.com 2606:4700:4700::1111#cloudflare-dns.com 2606:4700:4700::1001#cloudflare-dns.com
# Google: 8.8.8.8#dns.google 8.8.4.4#dns.google 2001:4860:4860::8888#dns.google 2001:4860:4860::8844#dns.google
# Quad9: 9.9.9.9#dns.quad9.net 149.112.112.112#dns.quad9.net 2620:fe::fe#dns.quad9.net 2620:fe::9#dns.quad9.net
DNS=1.1.1.1
FallbackDNS=8.8.8.8
Domains=
DNSSEC=no
#DNSOverTLS=no
#MulticastDNS=no
#LLMNR=no
#Cache=no-negative
#CacheFromLocalhost=no
#DNSStubListener=yes
#DNSStubListenerExtra=
#ReadEtcHosts=yes
#ResolveUnicastSingleLabel=no
$ cat /run/systemd/resolv/resolv.conf
# This is /run/systemd/resolve/resolv.conf managed by man:systemd-resolved(8).
# Do not edit.
#
# This file might be symlinked as /etc/resolv.conf. If you're looking at
# /etc/resolv.conf and seeing this text, you have followed the symlink.
#
# This is a dynamic resolv.conf file for connecting local clients directly to
# all known uplink DNS servers. This file lists all configured search domains.
#
# Third party programs should typically not access this file directly, but only
# through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a
# different way, replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.
nameserver 1.1.1.1
nameserver 8.8.8.8
nameserver 9.9.9.9
search .