Simpler alternative to #4348.

The current setup with closesocket() is strange. It poses
as a compatibility wrapper but adds functionality.

Rename it and make it a documented utility function in netbase.

Code movement only, zero effect on the functionality.

Bugfix: strerror_r can return an error, and if it does, POSIX does not specify the content of the buffer

Problem introduced in caf6150e. Thanks to @drak for noticing. Fixes #4473.

- now we support SOCKS5 only

In the LookupIntern(), things changed are:

  1. Call getaddrinfo_a() instead of getaddrinfo() if available, the former is a sync version of the latter;
  2. Try using inet_pton()/inet_addr() to convert the input text to a network addr structure at first, if success the extra name resolving thread inside getaddrinfo_a() could be avoided;
  3.  An interruption point added in the waiting loop for return from getaddrinfo_a(), which completes the improve for thread responsiveness.

A easy way to see the effect is to kick off a 'bitcoind stop' immediately after 'bitcoind -daemon', before the change it would take several, or even tens of, minutes on a bad network situation to wait for the running bitcoind to exit, now it costs only seconds.
Signed-off-by: Huang Le <4tarhl@gmail.com>

Log the name of the error as well as the error code if a network problem
happens. This makes network troubleshooting more convenient.

Use thread-safe strerror_r and the WIN32 equivalent FormatMessage.

Use the new function parseint32 in SplitHostPort instead of calling
strtol directly.

The year is 2014. All supported operating systems have IPv6 support,
most certainly at build time (this doesn't mean that IPv6 is configured,
of course).

If noone is exercising the functionality to disable it, that means it
doesn't get tested, and IMO it's better to get rid of it.

(it's also not used consistently in RPC/boost and Net code...)

contrib/devtools/fix-copyright-headers.py script to be able to perform this maintenance task with ease during the rest of the year, every year. Modifications to contrib/devtools/README.md to document what fix-copyright-headers.py does.

After the tinyformat switch sprintf() family functions support passing
actual std::string objects.

Remove unnecessary c_str calls (236 of them) in logging and formatting.

- example: if util.h includes stdint.h, remove it from util.cpp, as
  util.h is the first header included in util.cpp

Use misc methods of avoiding unnecesary header includes.
Replace int typedefs with int##_t from stdint.h.
Replace PRI64[xdu] with PRI[xdu]64 from inttypes.h.
Normalize QT_VERSION ifs where possible.
Resolve some indirect dependencies as direct ones.
Remove extern declarations from .cpp files.

Using ! on a non-zero value will always return 0.

Also remove some duplicate and superfluous code in other places.

As memset() can be optimized out by a compiler it should not be used in
privacy/security relevant code parts. OpenSSL provides the safe
OPENSSL_cleanse() function in crypto.h, which perfectly does the job of
clean and overwrite data.

For details see: http://www.viva64.com/en/b/0178/

- change memset() to OPENSSL_cleanse() where appropriate
- change a hard-coded number from netbase.cpp into a sizeof()

I2P apparently needs 256 bits to store a fully routable address. Garlicat
requires a centralized lookup service to map the 80-bit addresses to fully
routable ones (as far as I understood), so that's not really usable in our
situation.

To support I2P routing and peer exchange for it, another solution is needed.
This will most likely imply a network protocol change, and extension of the
'addr' message.

Don't use hand-rolled string manipulation routine with a fixed
buffer in the bitcoin core, instead make use of c++ strings and boost.

- fix #1560 by properly locking proxy related data-structures
- update GetProxy() and introduce GetNameProxy() to be able to use a
  thread-safe local copy from proxyInfo and nameproxyInfo
- update usage of GetProxy() all over the source to match the new
  behaviour, as it now fills a full proxyType object
- rename GetNameProxy() into HaveNameProxy() to be more clear

- I checked every occurance of strprintf() in the code and used %u, where
  unsigned vars are used
- the change to GetByte() was made, as ip is an unsigned char

Fix OBO in socks5 auth proposal. This fixes compatibility with openssh's socks5 proxy and tor's .2.3.x branch.

Add support for Tor/I2P networks, and make code more readable.

This commit adds support for .onion addresses (mapped into the IPv6
by using OnionCat's range and encoding), and the ability to connect
to them via a SOCKS5 proxy.

* Do not rely on "a.b.c" being interpreted as "a.0.b.c"
* Parse numeric addresses for address families for which no device is configured

Implement the following rules:
* Interpret [X]:Y as host=X port=Y, if Y is an integer
* Interpret X:Y as host=X port=Y, if Y is an integer and X contains no colon
* Interpret X:Y as host=X:Y port=default otherwise

I originally created a pull to replace the "COPYING" in crypter.cpp and
crypter.h, but it turned out that COPYING was actually the correct
file.