netdev - Re: [PATCH net-next v5 1/7] vxlan: Restructure vxlan socket apis.

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Date:	Wed, 31 Jul 2013 20:00:12 -0700
From:	Pravin Shelar <pshelar@...ira.com>
To:	Stephen Hemminger <stephen@...workplumber.org>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next v5 1/7] vxlan: Restructure vxlan socket apis.

On Wed, Jul 31, 2013 at 4:45 PM, Stephen Hemminger
<stephen@...workplumber.org> wrote:
> On Wed, 31 Jul 2013 16:14:23 -0700
> Pravin B Shelar <pshelar@...ira.com> wrote:
>
>>       /* Disable multicast loopback */
>>       inet_sk(sk)->mc_loop = 0;
>> +     spin_lock(&vn->sock_lock);
>> +     hlist_add_head_rcu(&vs->hlist, vs_head(net, port));
>> +     spin_unlock(&vn->sock_lock);
>>
>
> This change could potentially put two of the sockets with the
> same port in the list.
>
> There is an existing check in vxlan_sock_work to handle this
> now. It does:
>   create new socket (no locks)
>
>   spin_lock
>   if (udp_socket with that port exists)
>       drop new socket
>   else
>       add to list
>   spin_unlock
>
> Your code seems to immediately put it on the list which
> will cause duplicates if race occurs.

I do not think it is possible.
Create new socket does bind which shld fail on same port. So there
would be only one vxlan-sock entry in socket table.
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