The (administratively maintained) mapping file /etc/iproute2/rt_tables is not writeable.

[lukisi]

The file /etc/iproute2/rt_tables resides on the squashfs mounted at / (root).
It is not symlinked to any writeable path, thus is not writeable.
For what I read at http://linux-ip.net/html/routing-tables.html it should be
writeable by the administrator of a system.

[Mark Shuttleworth (sabdfl)]

It should be possible to manipulate rt_tables on Ubuntu Core.

 status: confirmed

[Oliver Grawert (ogra)]

as a start i'll make the dir writable in the edge images.

but i think the remaining question is if we just want to make it rw in the network-control interface (the dir is already listed in the interface definition, but only in read mode) or if it makes sense to have a dedicated network-routing interface, i'll talk to the security team tomorrow to get some input on this topic.

[Oliver Grawert (ogra)]

done, tomorrows build on http://people.canonical.com/~ogra/snappy/all-snaps/daily/ will have the dir writable.

[Jamie Strandboge (jdstrand)]

I think network-control is fine. It already has a ton of other rules for routing. I can update the policy for that.

[lukisi (luca-dionisi)]

This is the workflow with which my application uses the file rt_tables.

* The administrator of a system, after the install of the application
  will be directed to modify (manually) the file rt_tables adding a
  certain range of ID numbers reserved for its tasks.
    E.g.
    # Reserved for (MY_APP)
    200 myapp_reserved_table_200
    199 myapp_reserved_table_199
    198 myapp_reserved_table_198
    ...
    # END Reserved for (MY_APP)
* The application can alter the names for those tables by directly
  altering the file rt_tables.
* The application issues 'ip' commands that involve the use of such
  names.
    E.g.
    ip rule add table mytablename
    ip route add 169.254.1.1 dev eth0 table mytablename
    ip route add 10.0.0.16/28 via 169.254.1.1 dev eth0 table mytablename

[Jamie Strandboge (jdstrand)]

@lukisi, thanks for your feedback! I'll make sure all of this is supported when I do the PR.

[Jamie Strandboge (jdstrand)]

The policy changes are committed and will be part of snapd 2.22.

[Jamie Strandboge (jdstrand)]

This was fixed in 2.22.