Inpcb table mutex protects addr and port during bind(2) and connect(2).

Inpcb table mutex protects addr and port during bind(2) and connect(2).

in_pcbbind(), in_pcbconnect(), and in6_pcbconnect() have to set
addresses and ports within the same critical section as the inpcb
hash table calculation.  Also lookup and address selection have to
be protected to avoid bindings and connections that are not unique.

For that in_pcbpickport() and in_pcbbind_locked() expect that the
table mutex is already taken.  The functions in_pcblookup_lock(),
in_pcblookup_local_lock(), and in_pcbaddrisavail_lock() grab the
mutex iff the lock parameter is IN_PCBLOCK_GRAB.  Otherwise the
parameter is IN_PCBLOCK_HOLD has the lock has to be taken already.
Note that in_pcblookup_lock() and in_pcblookup_local() return an
inp with increased reference iff they take and release the lock.
Otherwise the caller protects the life time of the inp.

This gives enough flexibility that in_pcbbind() and in_pcbconnect()
can hold the table mutex when they need it.  The public inpcb API
does not change.

OK sashan@ mvs@