rxrpc: Allow list of in-use local UDP endpoints to be viewed in /proc

[ Upstream commit 33912c26 ]

Allow the list of in-use local UDP endpoints in the current network
namespace to be viewed in /proc.

To aid with this, the endpoint list is converted to an hlist and RCU-safe
manipulation is used so that the list can be read with only the RCU
read lock held.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: 3bcd6c7e ("rxrpc: Fix race between conn bundle lookup and bundle removal [ZDI-CAN-15975]")
Signed-off-by: Sasha Levin <sashal@kernel.org>