[ovs-dev] [PATCH 3/3] datapath: Do not fail to load on gre protocol conflict

[Gregory Rose]

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 <gvrose8192 at gmail.com 
> <mailto:gvrose8192 at gmail.com>> 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
>                 <gvrose8192 at gmail.com <mailto:gvrose8192 at gmail.com>>
>                 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 <gvrose8192 at gmail.com
>                     <mailto:gvrose8192 at gmail.com>>
>                     ---
>
>                 I read through the patch and look good to me.
>                 Acked-by: William Tu <u9012063 at gmail.com
>                 <mailto:u9012063 at gmail.com>>
>
>             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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