netdev - Re: [PATCHv10 ovs 12/15] datapath: Add support for unique flow identifiers.

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Message-ID: <CANr6G5zoe=vAme08cHzdM76iYCjMYPz-mcbw236mk1-dVqxLdQ@mail.gmail.com>
Date:	Thu, 20 Nov 2014 16:33:47 -0800
From:	Joe Stringer <joestringer@...ira.com>
To:	Pravin Shelar <pshelar@...ira.com>
Cc:	"dev@...nvswitch.org" <dev@...nvswitch.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCHv10 ovs 12/15] datapath: Add support for unique flow identifiers.

On 19 November 2014 15:34, Pravin Shelar <pshelar@...ira.com> wrote:
> On Thu, Nov 13, 2014 at 11:17 AM, Joe Stringer <joestringer@...ira.com> wrote:
>> @@ -684,33 +691,43 @@ static size_t ovs_flow_cmd_msg_size(const struct sw_flow_actions *acts)
>>
>>  /* Called with ovs_mutex or RCU read lock. */
>>  static int ovs_flow_cmd_fill_match(const struct sw_flow *flow,
>> -                                  struct sk_buff *skb)
>> +                                  struct sk_buff *skb, u32 ufid_flags)
>>  {
>>         struct nlattr *nla;
>>         int err;
>>
>> -       /* Fill flow key. */
>> -       nla = nla_nest_start(skb, OVS_FLOW_ATTR_KEY);
>> -       if (!nla)
>> -               return -EMSGSIZE;
>> -
>> -       err = ovs_nla_put_flow(&flow->unmasked_key, &flow->unmasked_key, skb,
>> -                              false);
>> -       if (err)
>> -               return err;
>> -
>> -       nla_nest_end(skb, nla);
>> +       /* Fill flow key. If userspace didn't specify a UFID, then ignore the
>> +        * OMIT_KEY flag. */
>> +       if (!(ufid_flags & OVS_UFID_F_OMIT_KEY) ||
>> +           !flow->index_by_ufid) {
>
> I am not sure about this check, userspace needs to send atleast ufid
> or the unmasked key as id for flow. otherwise we shld flag error. Here
> we can serialize flow->key.
> There could be another function which takes care of flow-id
> serialization where we serialize use ufid or unmasked key as flow id.
> Lets group ufid and unmasked key together rather than masked key and
> unmasked key which are not related.

Let me start from scratch and see if this is what you're saying.

fill_id() would serialize the UFID or unmasked key if UFID is not available.
fill_key() would serialize the masked key if !(ufid_flags &
OVS_UFID_F_OMIT_KEY) and UFID was provided (but not when the UFID is
missing).
fill_mask() would serialize the mask if !(ufid_flags & OVS_UFID_F_OMIT_MASK).

I see key and id as related, because the flow_key serves as both the
"match" and the "id" in the non-ufid case, so we need to know the same
piece of information in both functions to ensure we don't serialize
the key twice.
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