[PATCH v01] net/af_packet: don't specify protocol on socket create

[Ferruh Yigit]

On 10/17/2024 2:38 AM, Stephen Hemminger wrote:
> On Sun, 13 Oct 2024 16:59:47 +0300
> Gur Stavi <gur.stavi at huawei.com> wrote:
> 
>> When creating AF_PACKET socket with specified protocol it is
>> immediately implicitly bound to any existing interface and
>> becomes RUNNING. Calling bind on such socket is affectively unbind
>> from "any interface", then bind to the specific interface.
>>
>> When creating socket with 0 as protocol, it is created in non-RUNNING
>> state, then it can be bound to interface and protocol in a single bind
>> call and switch to RUNNING state.
>>
>> Especially with ETH_P_ALL, binding to any interface is not a good idea.
>> It is safer and faster to use the 2nd approach.
>>
>> This patch replaces protocol in socket creation from ETH_P_ALL to 0.
>>
>> Signed-off-by: Gur Stavi <gur.stavi at huawei.com>
> 
> This makes sense see packet(7) man page:
> 
>        By default, all packets of the specified protocol type are passed  to  a
>        packet  socket.   To  get  packets  only  from  a specific interface use
>        bind(2) specifying an address in a struct sockaddr_ll to bind the packet
>        socket to an interface.  Fields used for binding are sll_family  (should
>        be AF_PACKET), sll_protocol, and sll_ifindex.
> 
> So there is a small window where the packet socket could pick up junk before
> the bind from other interfaces.
>

Thanks, this answers some of my questions in this thread, also I did
some experiment and verified the same.

I agree this change is more close the intention of the driver (driver is
not to get packets from all interfaces), hence:

Acked-by: Ferruh Yigit <ferruh.yigit at amd.com>