MFC r271073:
  Do not blindly announce 1000baseT half-duplex capability in
  autonegotiation.  Some controllers like cgem(4) do not support
  half-duplex at gigabit speeds.
MFC r271395 (by trasz):
Make sure we handle less than zero timeouts in iSCSI initiator and target
in a reasonable way.

Sponsored by:	The FreeBSD Foundation
MFC r271718 (by bdrewery): Correct a comment
MFC r272597: Fix length of Extended INQUIRY Data VPD page.
MFC r272613:
Add support for MaxBurstLength and Expected Data transfer Length parameters.

Before this change target could send R2T request for write transfer of any
size, that could violate iSCSI RFC, which allows initiator to limit maximum
R2T size by negotiating MaxBurstLength connection parameter.

Also report an error in case of write underflow, when initiator provides
less data than initiator expects.  Previously in such case our target
sent R2T request for non-existing data, violating the RFC, and confusing
some initiators.  SCSI specs don't explicitly define how write underflows
should be handled and there are different oppinions, but reporting error
is hopefully better then violating iSCSI RFC with unpredictable results.
MFC r272734:
Add support for WRITE ATOMIC (16) command and report SBC-4 compliance.

Atomic writes are only supported for ZVOLs in "dev" mode.  In other cases
atomicity can not be guarantied and so the command is blocked.
MFC r272748:
Implement software (mode page) and hardware (config) write protection.
MFC r272812: Make iSCSI connection close somewhat less aggressive.

It allows to push out some final data from the send queue to the socket
before its close.  In particular, it increases chances for logout response
to be delivered to the initiator.
MFC r272893:
Store persistent reservation keys as uint64_t instead of uint8_t[8].

This allows to simplify the code and save 512KB of RAM per LUN (8%)
by removing no longer needed "registered" keys flags.