Merge branch 'l2tp_seq'

James Chapman says:

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L2TP data sequence numbers, if enabled, ensure in-order delivery. A
receiver may reorder data packets, or simply drop out-of-sequence
packets. If reordering is not enabled, the current implementation does
not handle data packet loss correctly, which can result in a stalled
L2TP session datapath as soon as the first packet is lost. Most L2TP
users either disable sequence numbers or enable data packet reordering
when sequence numbers are used to circumvent the issue. This patch
series fixes the problem, and makes the L2TP sequence number handling
RFC-compliant.

v2 incorporates string format changes requested by sergei.shtylyov@cogentembedded.com.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>