Gilles Chanteperdrix authored Sep 29, 2015 and Philippe Gerum committed Oct 01, 2015

With socket pools allocations locking sockets, when a received packet
switches from the device pool to the socket pool and is queued in a
socket incoming queue, the socket is locked preventing its destruction
until all packets have been received. This is probably the reason for
this bug report:
http://xenomai.org/pipermail/xenomai/2015-June/034345.html

Furthermore, when looking at the code in af_packet.c when a packet has
been acquired by the socket pool, but is not yet queued, the socket is
locked, so, the socket can not disappear and the packet leak, so the
locking is redundant. The case of ip_input.c is a bit different as there
is a small window where a packet is in flight and a socket can be
closed, but this can been fixed.

What can happen however, is that a module can be removed in the middle
of the packet reception, causing all sorts of trouble.

So, this commit:
- suppresses the locking of sockets by the socket pool allocation;
- gets sockets creation to lock the module in which they are created;
- fixes packet delivery in ip_input.c to lock the destination socket as
long as the packet has not been delivered.