[Bug 2003778] [NEW] systemd-resolved uses malformed link-local IPv6 forwarder

[geppi]

Public bug reported:

In a network with a local nameserver that has IPv4-address 10.1.0.1 and
link-local IPv6-address fe80::2a0:57ff:fe24:b041%2 'resolvectl' returns:

Global
       Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: uplink

Link 2 (ens33)
    Current Scopes: DNS
         Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: fe80::2a0:57ff:fe24:b041
       DNS Servers: 10.1.0.1 fe80::2a0:57ff:fe24:b041%21905
        DNS Domain: < edited >

Name resolution fails because the indicated 'Current DNS Server'
IPv6-address is an incomplete link-local address. Also the link-local
IPv6-address indicated in the second position of the 'DNS Servers' line
is malformed. Issuing consecutive 'resolvectl' calls have the last 4
digits in this line changing, i.e. they all show
'fe80::2a0:57ff:fe24:b041%2', which would be the correct link-local
IPv6-address including the interface specification, but then 4 digits
that are not constant.

Workaround:

Take systemd-resoved out of stub-mode with:

(cd /etc && sudo rm -f resolv.conf && sudo ln -s
/run/systemd/resolve/resolv.conf resolv.conf)

The auto generate file '/run/systemd/resolve/resolv.conf' has the proper
specification of the name servers link-local IPv6-address:

nameserver 10.1.0.1
nameserver fe80::2a0:57ff:fe24:b041%2
search < edited >

The broken stub mode is configured with:

(cd /etc && rm -f resolv.conf && ln -s /run/systemd/resolve/stub-
resolv.conf resolv.conf)

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New

** Summary changed:

- systemd-resoled uses malformed link-local IPv6 forwarder
+ systemd-resolved uses malformed link-local IPv6 forwarder

** Description changed:

  In a network with a local nameserver that has IPv4-address 10.1.0.1 and
  link-local IPv6-address fe80::2a0:57ff:fe24:b041%2 'resolvectl' returns:
  
  Global
-        Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
+        Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
  resolv.conf mode: uplink
  
  Link 2 (ens33)
-     Current Scopes: DNS
-          Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
+     Current Scopes: DNS
+          Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
  Current DNS Server: fe80::2a0:57ff:fe24:b041
-        DNS Servers: 10.1.0.1 fe80::2a0:57ff:fe24:b041%21905
-         DNS Domain: < edited >
+        DNS Servers: 10.1.0.1 fe80::2a0:57ff:fe24:b041%21905
+         DNS Domain: < edited >
  
- Name resolution fails because the indicated name server IPv6-address is
- an incomplete link-local address. Also the link-local IPv6-address
- indicated in the second position of the 'DNS Servers' line is malformed.
- Issuing consecutive 'resolvectl' calls have the last 4 digits in this
- line changing, i.e. they all show 'fe80::2a0:57ff:fe24:b041%2', which
- would be the correct link-local IPv6-address including the interface
- specification, but then 4 digits that are not constant.
+ Name resolution fails because the indicated 'Current DNS Server'
+ IPv6-address is an incomplete link-local address. Also the link-local
+ IPv6-address indicated in the second position of the 'DNS Servers' line
+ is malformed. Issuing consecutive 'resolvectl' calls have the last 4
+ digits in this line changing, i.e. they all show
+ 'fe80::2a0:57ff:fe24:b041%2', which would be the correct link-local
+ IPv6-address including the interface specification, but then 4 digits
+ that are not constant.
  
  Workaround:
  
  Take systemd-resoved out of stub-mode with:
  
  (cd /etc && sudo rm -f resolv.conf && sudo ln -s
  /run/systemd/resolve/resolv.conf resolv.conf)
  
  The auto generate file '/run/systemd/resolve/resolv.conf' has the proper
  specification of the name servers link-local IPv6-address:
  
  nameserver 10.1.0.1
  nameserver fe80::2a0:57ff:fe24:b041%2
  search < edited >
  
- 
  The broken stub mode is configured with:
  
  (cd /etc && rm -f resolv.conf && ln -s /run/systemd/resolve/stub-
  resolv.conf resolv.conf)

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https://bugs.launchpad.net/bugs/2003778

Title:
  systemd-resolved uses malformed link-local IPv6 forwarder

Status in systemd package in Ubuntu:
  New

Bug description:
  In a network with a local nameserver that has IPv4-address 10.1.0.1
  and link-local IPv6-address fe80::2a0:57ff:fe24:b041%2 'resolvectl'
  returns:

  Global
         Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
  resolv.conf mode: uplink

  Link 2 (ens33)
      Current Scopes: DNS
           Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
  Current DNS Server: fe80::2a0:57ff:fe24:b041
         DNS Servers: 10.1.0.1 fe80::2a0:57ff:fe24:b041%21905
          DNS Domain: < edited >

  Name resolution fails because the indicated 'Current DNS Server'
  IPv6-address is an incomplete link-local address. Also the link-local
  IPv6-address indicated in the second position of the 'DNS Servers'
  line is malformed. Issuing consecutive 'resolvectl' calls have the
  last 4 digits in this line changing, i.e. they all show
  'fe80::2a0:57ff:fe24:b041%2', which would be the correct link-local
  IPv6-address including the interface specification, but then 4 digits
  that are not constant.

  Workaround:

  Take systemd-resoved out of stub-mode with:

  (cd /etc && sudo rm -f resolv.conf && sudo ln -s
  /run/systemd/resolve/resolv.conf resolv.conf)

  The auto generate file '/run/systemd/resolve/resolv.conf' has the
  proper specification of the name servers link-local IPv6-address:

  nameserver 10.1.0.1
  nameserver fe80::2a0:57ff:fe24:b041%2
  search < edited >

  The broken stub mode is configured with:

  (cd /etc && rm -f resolv.conf && ln -s /run/systemd/resolve/stub-
  resolv.conf resolv.conf)

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