• Donald Hunter's avatar
    doc/netlink: Add sub-message support to netlink-raw · de2d9874
    Donald Hunter authored
    Add a 'sub-message' attribute type with a selector that supports
    polymorphic attribute formats for raw netlink families like tc.
    
    A sub-message attribute uses the value of another attribute as a
    selector key to choose the right sub-message format. For example if the
    following attribute has already been decoded:
    
      { "kind": "gre" }
    
    and we encounter the following attribute spec:
    
      -
        name: data
        type: sub-message
        sub-message: linkinfo-data-msg
        selector: kind
    
    Then we look for a sub-message definition called 'linkinfo-data-msg' and
    use the value of the 'kind' attribute i.e. 'gre' as the key to choose
    the correct format for the sub-message:
    
      sub-messages:
        name: linkinfo-data-msg
        formats:
          -
            value: bridge
            attribute-set: linkinfo-bridge-attrs
          -
            value: gre
            attribute-set: linkinfo-gre-attrs
          -
            value: geneve
            attribute-set: linkinfo-geneve-attrs
    
    This would decode the attribute value as a sub-message with the
    attribute-set called 'linkinfo-gre-attrs' as the attribute space.
    
    A sub-message can have an optional 'fixed-header' followed by zero or
    more attributes from an attribute-set. For example the following
    'tc-options-msg' sub-message defines message formats that use a mixture
    of fixed-header, attribute-set or both together:
    
      sub-messages:
        -
          name: tc-options-msg
          formats:
            -
              value: bfifo
              fixed-header: tc-fifo-qopt
            -
              value: cake
              attribute-set: tc-cake-attrs
            -
              value: netem
              fixed-header: tc-netem-qopt
              attribute-set: tc-netem-attrs
    Reviewed-by: default avatarJakub Kicinski <kuba@kernel.org>
    Signed-off-by: default avatarDonald Hunter <donald.hunter@gmail.com>
    Link: https://lore.kernel.org/r/20231215093720.18774-3-donald.hunter@gmail.comSigned-off-by: default avatarJakub Kicinski <kuba@kernel.org>
    de2d9874
netlink-raw.yaml 17.4 KB