[Bug 1812748] Re: netplan.io's secondary IP address feature causes snmpd errors

[Robie Basak]

Thank you for taking the time to report this bug and helping to make
Ubuntu better.

Based on your description I can make a guess as to what is going on.

The "old" kernel interface for network interfaces (still supported under
Linux's interface stability promise) allowed named aliases. This is what
"ifconfig" uses ("ifconfig eth0:1 ..." etc).

The new interface, used by "ip" and everything new, generalises that to
a list - no specific alias names required - but supports a "label" for
backwards compatibility. See ip-address(8) for details (search for
"label").

I suspect that snmpd doesn't understand additional addresses attached to
a network interface that don't have a label.

I'm going to make an executive call here and say that a workaround in
netplan to always add a label is not feasible because that would require
a suitable implementation to exist in all of its backends as well as
maintenance of the labels to avoid conflicts, etc.

Therefore I think this bug can only realistically be fixed in net-snmp
by supporting the new kernel interface.

With this background (that I hope is accurate), could someone verify if
the latest upstream version of net-snmp still has this issue? I think
it's unlikely we'll be able to fix this in Ubuntu without an
implementation upstream.

Accordingly I'm marking the netplan.io task Invalid, but feel free to
reopen if you think my assessment is incorrect.

** Changed in: netplan.io (Ubuntu)
       Status: New => Invalid

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https://bugs.launchpad.net/bugs/1812748

Title:
  netplan.io's secondary IP address feature causes snmpd errors

Status in net-snmp package in Ubuntu:
  New
Status in netplan.io package in Ubuntu:
  Invalid

Bug description:
  netplan doesn't provide for interface aliases (for example: eth0:0),
  however, assigning two IP addresses to an interface the way netplan
  does causes snmpd to produce numerous "error on subcontainer 'ia_addr'
  insert (-1)" entries in syslog reported by snmpd.  This should'nt
  happen and is either a problem with snmpd or netplan.  This also
  occurs on non-netplan systems (for example, Ubuntu 16.04 using
  keepalived) when a secondary IP address is added without making it an
  alias.  Ubuntu 16.04 systems using interface aliases do not experience
  this problem.  If needed, I can supply information from the Ubuntu
  16.04 systems.

  apt-cache policy netplan.io
  netplan.io:
    Installed: 0.40.1~18.04.4
    Candidate: 0.40.1~18.04.4
    Version table:
   *** 0.40.1~18.04.4 500
          500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
          500 http://archive.ubuntu.com/ubuntu bionic-security/main amd64 Packages
          100 /var/lib/dpkg/status
       0.36.1 500
          500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages

  apt-cache policy snmpd
  snmpd:
    Installed: 5.7.3+dfsg-1.8ubuntu3.1
    Candidate: 5.7.3+dfsg-1.8ubuntu3.1
    Version table:
   *** 5.7.3+dfsg-1.8ubuntu3.1 500
          500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
          500 http://archive.ubuntu.com/ubuntu bionic-security/main amd64 Packages
          100 /var/lib/dpkg/status
       5.7.3+dfsg-1.8ubuntu3 500
          500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages

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