Re: [PATCH net-next v5 2/5] net: vxlan: add netlink option to bind vxlan sockets to local addresses

[Ido Schimmel <idosch@nvidia.com>]

On Tue, Aug 12, 2025 at 02:51:52PM +0200, Richard Gobert wrote:
> Currently, VXLAN sockets always bind to 0.0.0.0, even when a local
> address is defined. This commit adds a netlink option to change
> this behavior.
> 
> If two VXLAN endpoints are connected through two separate subnets,
> they are each able to receive traffic through both subnets, regardless
> of the local address. The new option will break this behavior.
> 
> Disable the option by default.
> 
> Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
> ---
>  drivers/net/vxlan/vxlan_core.c     | 43 +++++++++++++++++++++++++++---
>  include/net/vxlan.h                |  1 +
>  include/uapi/linux/if_link.h       |  1 +
>  tools/include/uapi/linux/if_link.h |  1 +
>  4 files changed, 43 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
> index f32be2e301f2..15fe9d83c724 100644
> --- a/drivers/net/vxlan/vxlan_core.c
> +++ b/drivers/net/vxlan/vxlan_core.c
> @@ -3406,6 +3406,7 @@ static const struct nla_policy vxlan_policy[IFLA_VXLAN_MAX + 1] = {
>  	[IFLA_VXLAN_LABEL_POLICY]       = NLA_POLICY_MAX(NLA_U32, VXLAN_LABEL_MAX),
>  	[IFLA_VXLAN_RESERVED_BITS] = NLA_POLICY_EXACT_LEN(sizeof(struct vxlanhdr)),
>  	[IFLA_VXLAN_MC_ROUTE]		= NLA_POLICY_MAX(NLA_U8, 1),
> +	[IFLA_VXLAN_LOCALBIND]	= NLA_POLICY_MAX(NLA_U8, 1),

You should only expose the option to user space when it's fully
supported by the kernel, which is not the case here.

>  };

[...]

> diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> index 784ace3a519c..7350129b1444 100644
> --- a/include/uapi/linux/if_link.h
> +++ b/include/uapi/linux/if_link.h
> @@ -1399,6 +1399,7 @@ enum {
>  	IFLA_VXLAN_LABEL_POLICY, /* IPv6 flow label policy; ifla_vxlan_label_policy */
>  	IFLA_VXLAN_RESERVED_BITS,
>  	IFLA_VXLAN_MC_ROUTE,
> +	IFLA_VXLAN_LOCALBIND,
>  	__IFLA_VXLAN_MAX
>  };
>  #define IFLA_VXLAN_MAX	(__IFLA_VXLAN_MAX - 1)
> diff --git a/tools/include/uapi/linux/if_link.h b/tools/include/uapi/linux/if_link.h
> index 7e46ca4cd31b..eee934cc2cf4 100644
> --- a/tools/include/uapi/linux/if_link.h
> +++ b/tools/include/uapi/linux/if_link.h
> @@ -1396,6 +1396,7 @@ enum {
>  	IFLA_VXLAN_VNIFILTER, /* only applicable with COLLECT_METADATA mode */
>  	IFLA_VXLAN_LOCALBYPASS,
>  	IFLA_VXLAN_LABEL_POLICY, /* IPv6 flow label policy; ifla_vxlan_label_policy */
> +	IFLA_VXLAN_LOCALBIND,

As you can see, the file was not updated in a while and will result in
different values for IFLA_VXLAN_LOCALBIND. I would just drop this hunk
unless you need it for some reason, in which case you can sync the file
in a separate commit.

>  	__IFLA_VXLAN_MAX
>  };
>  #define IFLA_VXLAN_MAX	(__IFLA_VXLAN_MAX - 1)
> -- 
> 2.36.1
>