[ovs-dev] [PATCH] compat: Allow IPv6 GRE/ERSPAN Tx when ip6_gre is loaded

[William Tu]

On Thu, Jul 26, 2018 at 9:11 AM, Greg Rose <gvrose8192 at gmail.com> wrote:

> When for some reason the built-in kernel ip6_gre module is loaded that
> would prevent the openvswitch kernel driver from loading.  Even when
> the built-in kernel ip6_gre module is loaded we can still perform
> port mirroring via Tx.  Adjust the error handling and detect when
> the ip6_gre kernel module is loaded and in that case still enable
> IPv6 GRE/ERSPAN Tx.
>
> Signed-off-by: Greg Rose <gvrose8192 at gmail.com>
> ---
>  datapath/linux/compat/ip6_gre.c | 39 ++++++++++++++++++++++++++++++
> +++------
>  datapath/vport.c                | 17 +++++++++++++++--
>  2 files changed, 48 insertions(+), 8 deletions(-)
>
> diff --git a/datapath/linux/compat/ip6_gre.c b/datapath/linux/compat/ip6_
> gre.c
> index 0c88547..f532f21 100644
> --- a/datapath/linux/compat/ip6_gre.c
> +++ b/datapath/linux/compat/ip6_gre.c
> @@ -65,6 +65,7 @@
>  #define IP6_GRE_HASH_SIZE (1 << IP6_GRE_HASH_SIZE_SHIFT)
>
>  static unsigned int ip6gre_net_id __read_mostly;
> +static bool ip6_gre_loaded = false;
>  struct ip6gre_net {
>         struct ip6_tnl __rcu *tunnels[4][IP6_GRE_HASH_SIZE];
>
> @@ -2792,19 +2793,43 @@ int rpl_ip6gre_init(void)
>         int err;
>
>         err = register_pernet_device(&ip6gre_net_ops);
> -       if (err < 0)
> -               return err;
> +       if (err < 0) {
> +               if (err == -EEXIST)
> +                       goto ip6_gre_loaded;
> +               else
> +                       goto out;
> +       }
>
>         err = inet6_add_protocol(&ip6gre_protocol, IPPROTO_GRE);
>         if (err < 0) {
>                 pr_info("%s: can't add protocol\n", __func__);
> -               goto add_proto_failed;
> +               if (err == -EBUSY) {
>

inet6_add_protocol returns -1 when there already a protocol registered.

+                       goto ip6_gre_loaded;
> +               } else {
> +                       goto add_proto_failed;
> +               }
>         }
>
>         pr_info("GRE over IPv6 tunneling driver\n");
>         ovs_vport_ops_register(&ovs_ip6gre_vport_ops);
>         ovs_vport_ops_register(&ovs_erspan6_vport_ops);
> -       return 0;
> +       return err;
> +
> +ip6_gre_loaded:
> +       /* Since GRE only allows single receiver to be registerd,
> +        * we skip here so only gre transmit works, see:
> +        *
> +        * commit 9f57c67c379d88a10e8ad676426fee5ae7341b14
>

This commit is for ipv4 gre.
IPv6 gre is commit f9242b6b28d61
(David S. Miller  2012-06-19 18:56:21 -0700 34)     return !cmpxchg((const
struct inet6_protocol **)&inet6_protos[protocol],


> +        * Author: Pravin B Shelar <pshelar at nicira.com>
> +        * Date:   Fri Aug 7 23:51:52 2015 -0700
> +        *     gre: Remove support for sharing GRE protocol hook
> +        *
> +        * OVS GRE receive part is disabled.
> +        */
>

Others look good to me!
Thanks for the patch

William