Re: [PATCH net-next v1 3/3] net/mlx5e: TC, Add support for VxLAN GBP encap/decap flows offload

[Alexander Lobakin <aleksander.lobakin@intel.com>]

From: Gavin Li <gavinl@nvidia.com>
Date: Wed, 15 Feb 2023 16:30:04 +0800

> 
> On 2/15/2023 11:36 AM, Gavin Li wrote:
>> External email: Use caution opening links or attachments
>>
>>
>> On 2/14/2023 11:26 PM, Alexander Lobakin wrote:
>>> External email: Use caution opening links or attachments
>>>
>>>
>>> From: Gavin Li <gavinl@nvidia.com>
>>> Date: Tue, 14 Feb 2023 15:41:37 +0200

[...]

>>>> @@ -96,6 +99,70 @@ static int mlx5e_gen_ip_tunnel_header_vxlan(char
>>>> buf[],
>>>>        udp->dest = tun_key->tp_dst;
>>>>        vxh->vx_flags = VXLAN_HF_VNI;
>>>>        vxh->vx_vni = vxlan_vni_field(tun_id);
>>>> +     if (tun_key->tun_flags & TUNNEL_VXLAN_OPT) {
>>>> +             md = ip_tunnel_info_opts((struct ip_tunnel_info
>>>> *)e->tun_info);
>>>> +             vxlan_build_gbp_hdr(vxh, tun_key->tun_flags,
>>>> +                                 (struct vxlan_metadata *)md);
>>> Maybe constify both ip_tunnel_info_opts() and vxlan_build_gbp_hdr()
>>> arguments instead of working around by casting away?
>> ACK. Sorry for the confusion---I misunderstood the comment.
> This ip_tunnel_info_opts is tricky to use const to annotate the arg
> because it will have to cast from const to non-const again upon returning.

It's okay to cast away for the `void *` returned.
Alternatively, use can convert it to a macro and use
__builtin_choose_expr() or _Generic to return const or non-const
depending on whether the argument is constant. That's what was recently
done for container_of() IIRC.

>>>
>>>> +     }
>>>> +
>>>> +     return 0;
>>>> +}
[...]

Thanks,
Olek