Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Improve compatibility with old flex and fix build with GCC.

- Add support for 'memsync' mode. This is the fastest replication mode that's
why it will now be the default.
- Bump protocol version to 2 and add backward compatibility for version 1.
- Allow to specify hosts by kern.hostid as well (in addition to hostname and
kern.hostuuid) in configuration file.

Sponsored by: Panzura
Tested by: trociny

Fix socket calls on error post-r243965.

Submitted by: Garrett Cooper

Fix world after byacc import:
- old yacc(1) use to magicially append stdlib.h, while new one don't
- new yacc(1) do declare yyparse by itself, fix redundant declaration of
'yyparse'

Approved by: des (mentor)

Fix typo in comment.

MFC after: 3 days

Fix minor memory leak.

MFC after: 3 days

Remove another unused token.

MFC after: 3 days

Remove unused token 'port'.

MFC after: 3 days

Implement 'async' mode for HAST.

MFC after: 3 days

Allow to specify pidfile in HAST configuration file.

MFC after: 1 week

If the underlying provider doesn't support BIO_FLUSH, log it only once
and don't bother trying in the future.

MFC after: 3 days

After every activemap change flush disk's write cache, so that write
reordering won't make the actual write to be committed before marking
the coresponding extent as dirty.

It can be disabled in configuration file.

If BIO_FLUSH is not supported by the underlying file system we log a warning
and never send BIO_FLUSH again to that GEOM provider.

MFC after: 3 days

- Convert some impossible conditions into assertions.
- Add missing 'if' in comment.

MFC after: 3 days

Prefer PJDLOG_ASSERT() and PJDLOG_ABORT() over assert() and abort().
pjdlog versions will log problem to syslog when application is running in
background.

MFC after: 3 days

If no listen address is specified, bind by default to:

tcp4://0.0.0.0:8457
tcp6://[::]:8457

MFC after: 3 weeks

Rename ipv4/ipv6 to tcp4/tcp6.

MFC after: 3 weeks

In preparation for IPv6 support allow to specify multiple addresses to
listen on.

MFC after: 3 weeks

Allow to specify remote as 'none' again which was broken by r219351, where
'none' was defined as a value for checksum.

Reported by: trasz
MFC after: 1 week

Fix isitme(), which is used to check if node-specific configuration
belongs to our node, and was returning false positive if the first
part of a node name matches short hostname.

Approved by: pjd (mentor)

Timeout must be positive.

MFC after: 1 week

The replication mode that is currently support is fullsync, not memsync.
Correct this and print a warning if different replication mode is
configured.

MFC after: 1 week

In hast.conf we define the other node's address in 'remote' variable.
This way we know how to connect to secondary node when we are primary.
The same variable is used by the secondary node - it only accepts
connections from the address stored in 'remote' variable.
In cluster configurations it is common that each node has its individual
IP address and there is one addtional shared IP address which is assigned
to primary node. It seems it is possible that if the shared IP address is
from the same network as the individual IP address it might be choosen by
the kernel as a source address for connection with the secondary node.
Such connection will be rejected by secondary, as it doesn't come from
primary node individual IP.

Add 'source' variable that allows to specify source IP address we want to
bind to before connecting to the secondary node.

MFC after: 1 week

Allow to compress on-the-wire data using two algorithms:
- HOLE - it simply turns all-zero blocks into few bytes header;
it is extremely fast, so it is turned on by default;
it is mostly intended to speed up initial synchronization
where we expect many zeros;
- LZF - very fast algorithm by Marc Alexander Lehmann, which shows
very decent compression ratio and has BSD license.

MFC after: 2 weeks

Allow to checksum on-the-wire data using either CRC32 or SHA256.

MFC after: 2 weeks

Detect when resource is configured more than once.

MFC after: 3 days

When node-specific configuration is missing in resource section, provide
more useful information. Instead of:

hastd: remote address not configured for resource foo

Print the following:

No resource foo configuration for this node (acceptable node names: freefall, freefall.freebsd.org, 44333332-4c44-4e31-4a30-313920202020).

MFC after: 3 days

Plug memory leaks.

Found with: valgrind
MFC after: 3 days

Allow to execute specified program on various HAST events.

MFC after: 2 weeks
Obtained from: Wheel Systems Sp. z o.o. http://www.wheelsystems.com

Reduce indent where possible.

MFC after: 2 weeks
Obtained from: Wheel Systems Sp. z o.o. http://www.wheelsystems.com

Prepare configuration parsing code to be called multiple times:
- Don't exit on errors if not requested.
- Don't keep configuration in global variable, but allocate memory for
configuration.
- Call yyrestart() before yyparse() so that on error in configuration file
we will start from the begining next time and not from the place we left of.

MFC after: 1 month

Fix a problem where hastd will stuck in recv(2) after sending request to
secondary, which died between send(2) and recv(2). Do it by adding timeout
to recv(2) for primary incoming and outgoing sockets and secondary outgoing
socket.

Reported by: Mikolaj Golub <to.my.trociny@gmail.com>
Tested by: Mikolaj Golub <to.my.trociny@gmail.com>
MFC after: 3 days

Please welcome HAST - Highly Avalable Storage.

HAST allows to transparently store data on two physically separated machines
connected over the TCP/IP network. HAST works in Primary-Secondary
(Master-Backup, Master-Slave) configuration, which means that only one of the
cluster nodes can be active at any given time. Only Primary node is able to
handle I/O requests to HAST-managed devices. Currently HAST is limited to two
cluster nodes in total.

HAST operates on block level - it provides disk-like devices in /dev/hast/
directory for use by file systems and/or applications. Working on block level
makes it transparent for file systems and applications. There in no difference
between using HAST-provided device and raw disk, partition, etc. All of them
are just regular GEOM providers in FreeBSD.

For more information please consult hastd(8), hastctl(8) and hast.conf(5)
manual pages, as well as http://wiki.FreeBSD.org/HAST.

Sponsored by: FreeBSD Foundation
Sponsored by: OMCnet Internet Service GmbH
Sponsored by: TransIP BV