ip6addrctl —
configure address selection policy for IPv6 and IPv4
  
    | ip6addrctl | addprefix precedence
      label | 
  
    | ip6addrctl | installconfigfile | 
The ip6addrctl utility manages the policy table of
  source and destination address selection for outgoing IPv4 and IPv6 packets.
  When ip6addrctl is invoked without an argument or with
  a single argument show, it prints the content of the
  policy table currently installed in the kernel.
To modify the table, the following operations are available:
  - addprefix precedence label
- Add a policy entry. The prefix argument is an IPv6
      prefix, which is a key for the entry. An IPv4 prefix should be specified
      with an IPv6 prefix using an IPv4-mapped IPv6 address. The
      precedence and label arguments
      are decimal numbers, which specify the precedence and label values for the
      entry, respectively. This operation should be performed without an
      existing entry for the prefix.
- deleteprefix
- Delete a policy entry specified by prefix, which
      should be an IPv6 prefix. A corresponding entry for the prefix should have
      already been installed.
- flush
- Delete all existing policy entries in the kernel.
- installconfigfile
- Install policy entries from a configuration file named
      configfile. The configuration file should contain a
      set of policy entries. Each entry is specified in a single line which
      contains an IPv6 prefix, a decimal precedence value, and a decimal label
      value, separated with white space or tab characters. In the configuration
      file, lines beginning with the pound-sign
      (‘#’) are comments and are
    ignored.
Theip6addrctl utility exits 0 on success,
  and >0 if an error occurs.
Richard Draves,
    Default Address Selection for IPv6,
    RFC 3484.
The ip6addrctl utility first appeared in the KAME IPv6
  protocol stack kit. The original command name was
  addrselect, but it was then renamed to the current one
  so that the name would describe its function well.