netdev - Re: [PATCHv2 net-next 2/2] openvswitch: add erspan version II support

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Date:   Wed, 10 Jan 2018 22:35:14 +0100
From:   Jiri Benc <jbenc@...hat.com>
To:     William Tu <u9012063@...il.com>
Cc:     netdev@...r.kernel.org, Pravin B Shelar <pshelar@....org>
Subject: Re: [PATCHv2 net-next 2/2] openvswitch: add erspan version II
 support

On Tue,  9 Jan 2018 17:51:22 -0800, William Tu wrote:
> -	[OVS_TUNNEL_KEY_ATTR_ERSPAN_OPTS]   = { .len = sizeof(u32) },
> +	[OVS_TUNNEL_KEY_ATTR_ERSPAN_OPTSV1] = { .len = sizeof(u32) },
> +	[OVS_TUNNEL_KEY_ATTR_ERSPAN_OPTS]   = { .len = OVS_ATTR_NESTED,
> +						.next = ovs_erspan_opt_lens },

Ouch. It's actually much worse than that, you're redefining the meaning of
the field. That's complete no-go.

> +		case OVS_TUNNEL_KEY_ATTR_ERSPAN_OPTSV1:
> +			OVS_NLERR(log, "ERSPAN attribute %d is deprecated.",
> +				  type);
> +			return -EINVAL;

As is this.

> @@ -906,8 +1017,8 @@ static int __ip_tun_to_nlattr(struct sk_buff *skb,
>  			 vxlan_opt_to_nlattr(skb, tun_opts, swkey_tun_opts_len))
>  			return -EMSGSIZE;
>  		else if (output->tun_flags & TUNNEL_ERSPAN_OPT &&
> -			 nla_put_be32(skb, OVS_TUNNEL_KEY_ATTR_ERSPAN_OPTS,
> -				      ((struct erspan_metadata *)tun_opts)->u.index))
> +			 erspan_opt_to_nlattr(skb, tun_opts,
> +					      swkey_tun_opts_len))

And this.

The existing field must continue to work in the same way as before. It must
be accepted and *returned* by the kernel. You may add an additional field
but the existing behavior must be 100% preserved, both uABI and uAPI wise.

 Jiri