On 6/22/2018 5:36 PM, Yifeng Sun wrote:
Hi Greg,

I tried 4.4 and 4.16 both with ip_gre module loaded and didn't trigger this error.

I will try more, thanks!

Yifeng

Try CentOS 7 or RHEL 7.  I think those systems will be the ones most likely to exhibit the problem.

Thanks,

- Greg


On Fri, Jun 22, 2018 at 5:17 PM, Gregory Rose <[email protected] <mailto:[email protected]>> wrote:



    On 6/22/2018 4:40 PM, Yifeng Sun wrote:
    Hi Greg,

    I am debugging a GRE related issue. Do you mind telling me which
    kernel version will lead to (err == -EEXIST) here?

        else if (err == -EEXIST)
                    pr_warn("Cannot take GRE protocol entry - The
    ERSPAN feature may not be supported\n");

    Thanks,
    Yifeng


    Yifeng,

    I don't think it is kernel specific unless it is a very new kernel
    (4.16 or newer).

    The -EEXIST comes from ../datapath/linux/compat/gre.c in
    rpl_gre_init()

    int rpl_gre_init(void)
    {
            pr_info("GRE over IPv4 demultiplexor driver\n");

            if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
                    pr_err("can't add protocol\n");
                    return -EEXIST;
            }
            return 0;
    }

    Hope this helps,

    - Greg


    On Tue, Jun 5, 2018 at 10:56 AM, Gregory Rose
    <[email protected] <mailto:[email protected]>> wrote:

        On 6/5/2018 10:39 AM, Ben Pfaff wrote:

            On Tue, Jun 05, 2018 at 09:34:10AM -0700, Gregory Rose wrote:

                On 6/5/2018 9:07 AM, William Tu wrote:

                    On Mon, Jun 4, 2018 at 1:14 PM, Greg Rose
                    <[email protected]
                    <mailto:[email protected]>> wrote:

                        The ERSPAN feature depends on the gre kernel
                        module so on systems where
                        the ERSPAN feature isn't supported the
                        openvswitch kernel module would
                        attempt to grab the ipv4 GRE protocol entry
                        point and would fail to load
                        if it could not.

                        This patch modifies openvswitch to not fail
                        to load when the gre kernel
                        module is loaded and instead it will print a
                        warning message to the
                        kernel system log indicating that the ERSPAN
                        feature may not be
                        available.

                        We need this patch because users are
                        experiencing failures due to the
                        conflicts and high priority bugs are resulting.

                        Signed-off-by: Greg Rose
                        <[email protected]
                        <mailto:[email protected]>>
                        ---

                    I read through the patch and look good to me.
                    Acked-by: William Tu <[email protected]
                    <mailto:[email protected]>>

                Thanks William.

                After loading the ip_gre and gre kernel modules you
                can run a 'make
                check-kmod' test with those modules
                loaded and the results look good as well.

            I applied this series to master.  I added a reference to
            the thread
            where Jiri nacked the previous solution.


        Thank you!

        - Greg

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