linux-kernel - Re: [PATCHv4 net-next 10/10] openvswitch: Allow attaching helpers to ct action

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Date:	Thu, 20 Aug 2015 17:47:14 -0700
From:	Joe Stringer <joestringer@...ira.com>
To:	Pravin Shelar <pshelar@...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 10/10] openvswitch: Allow attaching helpers to
 ct action

On 19 August 2015 at 15:57, Pravin Shelar <pshelar@...ira.com> wrote:
> On Tue, Aug 18, 2015 at 4:39 PM, Joe Stringer <joestringer@...ira.com> wrote:
>> Add support for using conntrack helpers to assist protocol detection.
>> The new OVS_CT_ATTR_HELPER attribute of the ct action specifies a helper
>> to be used for this connection.
>>
>> Example ODP flows allowing FTP connections from ports 1->2:
>> in_port=1,tcp,action=ct(helper=ftp,commit),2
>> in_port=2,tcp,ct_state=-trk,action=ct(),recirc(1)
>> recirc_id=1,in_port=2,tcp,ct_state=+trk-new+est,action=1
>> recirc_id=1,in_port=2,tcp,ct_state=+trk+rel,action=1
>>
>> Signed-off-by: Joe Stringer <joestringer@...ira.com>
>> ---
>> v2-v3: No change.
>> v4: Change error code for unknown helper ENOENT->EINVAL.
>
> I got following compilation warning :
>
> net/openvswitch/conntrack.c:352:42: error: incompatible types in
> comparison expression (different address spaces)

Is this made available via another sparse flag? It looks like it's
related to the __rcu as you've mentioned below, but I'm not seeing
this (latest sparse, gcc-4.9.2)

>> +static int ovs_ct_add_helper(struct ovs_conntrack_info *info, const char *name,
>> +                            const struct sw_flow_key *key, bool log)
>> +{
>> +       struct nf_conntrack_helper *helper;
>> +       struct nf_conn_help *help;
>> +
>> +       helper = nf_conntrack_helper_try_module_get(name, info->family,
>> +                                                   key->ip.proto);
>> +       if (!helper) {
>> +               OVS_NLERR(log, "Unknown helper \"%s\"", name);
>> +               return -EINVAL;
>> +       }
>> +
>> +       help = nf_ct_helper_ext_add(info->ct, helper, GFP_KERNEL);
>> +       if (!help) {
>> +               module_put(helper->me);
>> +               return -ENOMEM;
>> +       }
>> +
>> +       help->helper = helper;
> helper is rcu pointer so need to use rcu API to set the value. I know
> it is not required here, but it is still cleaner to use the API.

Will update, thanks.
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