linux-kernel - Re: [PATCHv4 net-next 09/10] openvswitch: Allow matching on conntrack label

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Date:	Thu, 20 Aug 2015 08:45:12 -0700
From:	Pravin Shelar <pshelar@...ira.com>
To:	Joe Stringer <joestringer@...ira.com>
Cc:	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, pablo <pablo@...filter.org>,
	Florian Westphal <fwestpha@...hat.com>,
	Hannes Sowa <hannes@...hat.com>, Thomas Graf <tgraf@...g.ch>,
	Justin Pettit <jpettit@...ira.com>,
	Jesse Gross <jesse@...ira.com>
Subject: Re: [PATCHv4 net-next 09/10] openvswitch: Allow matching on conntrack label

On Wed, Aug 19, 2015 at 4:04 PM, Joe Stringer <joestringer@...ira.com> wrote:
> Thanks for the review,
>
> On 19 August 2015 at 14:24, Pravin Shelar <pshelar@...ira.com> wrote:
>> On Tue, Aug 18, 2015 at 4:39 PM, Joe Stringer <joestringer@...ira.com> wrote:
>>> Allow matching and setting the conntrack label field. As with ct_mark,
>>> this is populated by executing the CT action, and is a writable field.
>>> Specifying a label and optional mask allows the label to be modified,
>>> which takes effect on the entry found by the lookup of the CT action.
>>>
>>> E.g.: actions:ct(zone=1,label=1)
>>>
>>> This will perform conntrack lookup in zone 1, then modify the label for
>>> that entry. The conntrack entry itself must be committed using the
>>> "commit" flag in the conntrack action flags for this change to persist.
>>>

>
>>>         return false;
>>>  }
>>> @@ -508,8 +601,12 @@ void ovs_ct_free_action(const struct nlattr *a)
>>>
>>>  void ovs_ct_init(struct net *net, struct ovs_ct_perdp_data *data)
>>>  {
>>> +       unsigned int n_bits = sizeof(struct ovs_key_ct_label) * BITS_PER_BYTE;
>>> +
>>>         data->xt_v4 = !nf_ct_l3proto_try_module_get(PF_INET);
>>>         data->xt_v6 = !nf_ct_l3proto_try_module_get(PF_INET6);
>>> +       if (nf_connlabels_get(net, n_bits);
>>> +               OVS_NLERR(true, "Failed to set connlabel length");
>>>  }
>>>
>> In case of error should we reject conntrack label actions? Otherwise
>> user will never see any error. But action could drop packets.
>
> I suspect that currently errors would be seen from ovs_ct_set_label():
>
>>.......if (!cl || cl->words * sizeof(long) < OVS_CT_LABEL_LEN)
>>.......>.......return -ENOSPC;
>
> So, for cmd_execute, userspace would see this. For regular handling,
> pipeline processing would stop (so, drop).
>
> However, I agree it would be more friendly to have the attribute
> rejected up-front. Just means we'll pass the datapath all the way
> down:
> ovs_nla_get_match()
> --> ovs_key_from_nlattrs()
> --> metadata_from_nlattrs()
> --> ovs_ct_verify()
>
> And rather than simply reporting the error in ovs_ct_init() there,
> we'll store the success condition something like:
>
> @@ -721,8 +721,12 @@ void ovs_ct_init(struct net *net, struct
> ovs_ct_perdp_data *data)
>
>         data->xt_v4 = !nf_ct_l3proto_try_module_get(PF_INET);
>         data->xt_v6 = !nf_ct_l3proto_try_module_get(PF_INET6);
> -       if (nf_connlabels_get(net, n_bits));
> +       if (nf_connlabels_get(net, n_bits)) {
> +               data->xt_label = false;
>                 OVS_NLERR(true, "Failed to set connlabel length");
> +       } else {
> +               data->xt_label = true;
> +       }
>  }
>
>  void ovs_ct_exit(struct net *net, struct ovs_ct_perdp_data *data)
>
> ovs_ct_exit() also needs to be updated to ensure that if this fails,
> we don't try to put the connlabel use back.

Looks good.
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