Use memcpy() instead of strcpy() for copying the syn filter instance
arg, as it may be used to convey binary data.
Fixed lock-order reversal between sock lock and inp lock when setting
l2info on a socket.

The sock lock was being held by sosetopt() across the call to
ip_ctloutput(), which acquires the inp lock, now out-of-order.  This
tends to show up when the l2info is being set on a freshly accepted
socket while segments for that socket are being processed by
tcp_input() - when tcp_input() tries to acquire the receive sockbuf
lock while holding the inp lock, deadlock ensues, as the sock lock and
the receive sockbuf lock are currently one and the same.
Merge branch 'master' into passive_to_active