Re: [ovs-dev] [dp version v6] bridge: Store datapath version into ovsdb

[Ben Pfaff]

On Wed, Nov 05, 2014 at 01:32:32PM -0800, Andy Zhou wrote:
> OVS userspace are backward compatible with older Linux kernel modules.
> However, not having the most up-to-date datapath kernel modules can
> some times lead to user confusion. Storing the datapath version in
> OVSDB allows management software to check and optionally provide
> notifications to users.
> 
> Signed-off-by: Andy Zhou <az...@nicira.com>

Acked-by: Ben Pfaff <b...@nicira.com>

I think that the documentation could use some elaboration.  First a
few typos:
> +      <column name="datapath_version">
> +        Reports the Open vSwitch datapath version in use.  If the bridge
> +        uses a datapath that is  linked into ovsvswitchd, "&lt;built-in&gt;"
> +        will be stored, in liue of the actual version. If datapath version
> +        cannot be determined, "&lt;unknown&gt;" will be stored.
> +      </column>

s/ovsvswitchd/ovs-vswitchd/
s/liue/lieu/

But I'd add some text too that explains what this is good for.  Maybe
like this:

      <column name="datapath_version">
        <p>
          Reports the version number of the Open vSwitch datapath in use.  This
          allows management software to detect and report discrepancies between
          Open vSwitch userspace and datapath versions.  (The <ref
          column="ovs_version" table="Open_vSwitch"/> column in the <ref
          table="Open_vSwitch"/> reports the Open vSwitch userspace version.)
          The version reported depends on the datapath in use:
        </p>

        <ul>
          <li>
            When the kernel module included in the Open vSwitch source tree is
            used, this column reports the Open vSwitch version from which the
            module was taken.
          </li>

          <li>
            When the kernel module that is part of the upstream Linux kernel is
            used, this column reports <code>&lt;unknown&gt;</code>.
          </li>

          <li>
            When the datapath is built into the <code>ovs-vswitchd</code>
            binary, this column reports <code>&lt;built-in&gt;</code>.  A
            built-in datapath is by definition the same version as the rest of
            the Open VSwitch userspace.
          </li>

          <li>
            Other datapaths (such as the Hyper-V kernel datapath) currently
            report <code>&lt;unknown&gt;</code>.
          </li>
        </ul>

        <p>
          A version discrepancy between <code>ovs-vswitchd</code> and the
          datapath in use is not normally cause for alarm.  The Open vSwitch
          kernel datapaths for Linux and Hyper-V, in particular, are designed
          for maximum inter-version compatibility: any userspace version works
          with with any kernel version.  Some reasons do exist to insist on
          particular user/kernel pairings.  First, newer kernel versions add
          new features, that can only be used by new-enough userspace, e.g.
          VXLAN tunneling requires certain minimal userspace and kernel
          versions.  Second, as an extension to the first reason, some newer
          kernel versions add new features for enhancing performance that only
          new-enough userspace versions can take advantage of.
        </p>
      </column>

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