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以 .local 结尾的域名未解析

tag-icon • tag-icon systemd systemd-resolved mdns resolvconf
以 .local 结尾的域名未解析

我在 Linux (ubuntu) 桌面上解析 .local 主机时遇到一个奇怪的问题。 （我注意到，因为我的打印机停止工作。我发现打印机的 IP 地址是使用 mdns 解析的，但它不起作用。）然后我尝试 ping 另一台计算机。结果是：

ping: zoe.local: Name or service not known

avahi-browse 能够解析 IP 地址

= enp0s31f6 IPv4 zoe [xx:xx:xx:xx:xx:xx]                       Workstation          local
   hostname = [zoe.local]
   address = [192.168.3.221]
   port = [9]
   txt = []

然后我检查了内容/etc/nsswitch.conf。看起来很正常。

# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# If you have the `glibc-doc-reference' and `info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.

passwd:         compat systemd
group:          compat systemd
shadow:         compat
gshadow:        files

hosts:          files mdns4_minimal [NOTFOUND=return] dns myhostname mymachines
networks:       files

protocols:      db files
services:       db files
ethers:         db files
rpc:            db files

netgroup:       nis

/etc/resolv.conf 是 /run/resolvconf/resolv.conf 的符号链接，内容似乎是标准的：

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.

nameserver 127.0.0.53
search intern

libnss-mdns 也已安装。

在同一网络中的第二台机器上，.local 地址解析工作正常。然后我用 strace 比较了这两个 ping 命令。我发现systemd-resolved的结果是不同的。我捕获了环回接口的流量。有趣的是，systemd-resolvd 报告了 .local 域的 SOA。在下一步中，地址解析会向我的路由器询问 .local 地址。这会导致上述错误。

Wireshark 捕获显示：

1   0.000000000 127.0.0.1   127.0.0.53  DNS 65  Standard query 0x70d2 SOA local
2   0.001437    127.0.0.53  127.0.0.1   DNS 113 Standard query response 0x459c SOA local SOA router.intern

我的第二台机器本地 systemd 解析器不报告 SOA，并且 mdns 地址解析运行良好。

1   0.000000000 127.0.0.1   127.0.0.53  DNS 65  Standard query 0x70d2 SOA local
2   0.027250385 127.0.0.53  127.0.0.1   DNS 65  Standard query response 0x70d2 No such name SOA local

我尝试刷新 dns 缓存，systemd-resolve --flush-caches但没有什么区别。

systemd-resolvd 的行为似乎很奇怪。有谁知道这里出了什么问题？为什么用 SOA 来解决 systemd 解决的问题？

systemd-resolve --status在我看来很好：

Global
       LLMNR setting: no                  
MulticastDNS setting: no                  
  DNSOverTLS setting: no                  
      DNSSEC setting: no                  
    DNSSEC supported: no                  
          DNS Domain: intern              
          DNSSEC NTA: 10.in-addr.arpa     
                      16.172.in-addr.arpa 
                      168.192.in-addr.arpa
                      17.172.in-addr.arpa 
                      18.172.in-addr.arpa 
                      19.172.in-addr.arpa 
                      20.172.in-addr.arpa 
                      21.172.in-addr.arpa 
                      22.172.in-addr.arpa 
                      23.172.in-addr.arpa 
                      24.172.in-addr.arpa 
                      25.172.in-addr.arpa 
                      26.172.in-addr.arpa 
                      27.172.in-addr.arpa 
                      28.172.in-addr.arpa 
                      29.172.in-addr.arpa 
                      30.172.in-addr.arpa 
                      31.172.in-addr.arpa 
                      corp                
                      d.f.ip6.arpa        
                      home                
                      internal            
                      intranet            
                      lan                 
                      local               
                      private             
                      test                

Link 6 (vmnet8)
      Current Scopes: none
DefaultRoute setting: no  
       LLMNR setting: yes 
MulticastDNS setting: no  
  DNSOverTLS setting: no  
      DNSSEC setting: no  
    DNSSEC supported: no  

Link 5 (vmnet1)
      Current Scopes: none
DefaultRoute setting: no  
       LLMNR setting: yes 
MulticastDNS setting: no  
  DNSOverTLS setting: no  
      DNSSEC setting: no  
    DNSSEC supported: no  

Link 4 (virbr0-nic)
      Current Scopes: none
DefaultRoute setting: no  
       LLMNR setting: yes 
MulticastDNS setting: no  
  DNSOverTLS setting: no  
      DNSSEC setting: no  
    DNSSEC supported: no  

Link 3 (virbr0)
      Current Scopes: none
DefaultRoute setting: no  
       LLMNR setting: yes 
MulticastDNS setting: no  
  DNSOverTLS setting: no  
      DNSSEC setting: no  
    DNSSEC supported: no  

Link 2 (enp0s31f6)
      Current Scopes: DNS                     
DefaultRoute setting: yes                     
       LLMNR setting: yes                     
MulticastDNS setting: no                      
  DNSOverTLS setting: no                      
      DNSSEC setting: no                      
    DNSSEC supported: no                      
  Current DNS Server: 192.168.3.1             
         DNS Servers: 192.168.3.1             
                      fe80::2a0:57ff:fe24:94c9
          DNS Domain: ~.                      
                      intern

答案1

更新：

我发现了以下问题：https://github.com/lathiat/nss-mdns/issues/75

我的路由器/ISP 为 .local 域提供 SOA。阻止unicast SOA heuristicmdns 解析。我添加了/etc/mdns.allow以下内容：

.local.
.local

切换到 mdns4 而不是 mdns4_minimal 后，它可以工作。

hosts:          files mdns4 [NOTFOUND=return] dns myhostname mymachines

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