netdev - Re: [PATCH v3 net-next 7/8] geneve: Consolidate Geneve functionality in single module.

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Date:	Tue, 25 Aug 2015 14:35:53 -0700
From:	Jesse Gross <jesse@...ira.com>
To:	Pravin Shelar <pshelar@...ira.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v3 net-next 7/8] geneve: Consolidate Geneve functionality
 in single module.

On Tue, Aug 25, 2015 at 1:54 PM, Pravin Shelar <pshelar@...ira.com> wrote:
> On Tue, Aug 25, 2015 at 12:03 PM, Jesse Gross <jesse@...ira.com> wrote:
>> On Mon, Aug 24, 2015 at 10:43 AM, Pravin B Shelar <pshelar@...ira.com> wrote:
>>> diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
>>> index c05bc13..8eb875d 100644
>>> --- a/drivers/net/geneve.c
>>> +++ b/drivers/net/geneve.c
>>> @@ -492,36 +813,36 @@ static int geneve_configure(struct net *net, struct net_device *dev,
>> [...]
>>> +       gs = geneve_find_sock(gn, geneve->dst_port);
>>> +       if (gs) {
>>> +               if (metadata) {
>>> +                       if (gs->collect_md)
>>> +                               return -EEXIST;
>>> +                       else
>>> +                               return -EPERM;
>>> +               } else {
>>> +                       if (gs->collect_md)
>>> +                               return -EPERM;
>>> +
>>> +                       t = geneve_lookup(gn, htons(dst_port),
>>> +                                         rem_addr, geneve->vni);
>>> +                       if (t)
>>> +                               return -EBUSY;
>>> +               }
>>> +       }
>>
>> I like the new structure but unfortunately, I think there is a race.
>> If two devices are created with conflicting configurations but neither
>> is brought up then creation of both devices will succeed. However,
>> when the second one is brought up, it will silently collide with the
>> first.
>
> geneve tunnel is added to hash table during configure time. So the
> lookup does not have any dependency on device up or down state. The
> Lookup and hash table updates are done under rtnl lock.

But the check for duplicates is contingent on finding a socket. If we
configure two devices before calling geneve_open(), then there won't
be a socket yet and therefore no check.
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