* Fix a bitmask in PPPoPNS and rename constants in PPPoPNS and PPPoLAC.
* Fix a potential deadlock while releasing PPPoLAC/PPPoPNS socket.
PPP driver guarantees that no thread will be executing start_xmit() after
returning from ppp_unregister_channel(). To achieve this, a spinlock (downl)
is used. In pppolac_release(), ppp_unregister_channel() is called after sk_udp
is locked. At the same time, another thread might be running in pppolac_xmit()
with downl. Thus a deadlock will occur if the thread tries to lock sk_udp.
The same situation might happen on sk_raw in pppopns_release().
* Force PPPoLAC and PPPoPNS to bind an interface before creating PPP channel.
It is common to manipulate the routing table after configuring PPP device.
Since both PPPoLAC and PPPoPNS run over IP, care must be taken to make sure
that there is no loop in the routing table.
Although this can be done by adding a host route, it might still cause
problems when the interface is down for some reason.
To solve this, this patch forces both drivers to bind an interface before
creating PPP channel, so the system will not re-route the tunneling sockets
to another interface when the original one is down. Another benefit is that
now the host route is no longer required, so there is no need to remove it
when PPP channel is closed.
* Avoid sleep-inside-spinlock in PPPoLAC and PPPoPNS.
Since recv() and xmit() are called with a spinlock held, routines which might
sleep cannot be used. This issue is solved by following changes:
Incoming packets are now processed in backlog handler, recv_core(), instead of
recv(). Since backlog handler is always executed with socket spinlock held, the
requirement of ppp_input() is still satisfied.
Outgoing packets are now processed in workqueue handler, xmit_core(), instead of
xmit(). Note that kernel_sendmsg() is no longer used to prevent touching dead
sockets.
In release(), lock_sock() and pppox_unbind_sock() ensure that no thread is in
recv_core() or xmit(). Then socket handlers are restored before release_sock(),
so no packets will leak in backlog queue.
* Fix msg_iovlen in PPPoLAC and PPPoPNS.
Although any positive value should work (which is always true in both drivers),
the correct value should be 1.
Signed-off-by: Chia-chi Yeh <chiachi@android.com>