The ability to do HTTP requests over a UNIX domain socket has been
requested before, in Apr 2008 [0][1] and Sep 2010 [2]. While a
discussion happened, no patch seems to get through. I decided to give it
a go since I need to test a nginx HTTP server which listens on a UNIX
domain socket.

One patch [3] seems to make it possible to use the
CURLOPT_OPENSOCKETFUNCTION function to gain a UNIX domain socket.
Another person wrote a Go program which can do HTTP over a UNIX socket
for Docker[4] which uses a special URL scheme (though the name contains
cURL, it has no relation to the cURL library).

This patch considers support for UNIX domain sockets at the same level
as HTTP proxies / IPv6, it acts as an intermediate socket provider and
not as a separate protocol. Since this feature affects network
operations, a new feature flag was added ("unix-sockets") with a
corresponding CURL_VERSION_UNIX_SOCKETS macro.

A new CURLOPT_UNIX_SOCKET_PATH option is added and documented. This
option enables UNIX domain sockets support for all requests on the
handle (replacing IP sockets and skipping proxies).

A new configure option (--enable-unix-sockets) and CMake option
(ENABLE_UNIX_SOCKETS) can disable this optional feature. Note that I
deliberately did not mark this feature as advanced, this is a
feature/component that should easily be available.

 [0]: http://curl.haxx.se/mail/lib-2008-04/0279.html
 [1]: http://daniel.haxx.se/blog/2008/04/14/http-over-unix-domain-sockets/
 [2]: http://sourceforge.net/p/curl/feature-requests/53/
 [3]: http://curl.haxx.se/mail/lib-2008-04/0361.html
 [4]: https://github.com/Soulou/curl-unix-socket



Signed-off-by: Peter Wu <peter@lekensteyn.nl>

Added helper function for returning a GSS-API compatible SPN.

Bug: http://curl.haxx.se/bug/view.cgi?id=1457
Patch-by: Tomasz Kojm

Made log_gss_error() a common function so that it can be used in both
the http_negotiate code as well as the curl_sasl_gssapi code.

Added the initial version of curl_sasl_gssapi.c and updated the project
files in preparation for adding GSS-API based Kerberos V5 support.

On some platforms curl would crash if no credentials were used. As such
added detection of such a use case to prevent this from happening.

Reported-by: Gisle Vanem

This patch prepares for adding UNIX domain sockets support.

TCP_NODELAY and TCP_KEEPALIVE are specific to TCP/IP sockets, so do not
apply these to other socket types. bindlocal only works for IP sockets
(independent of TCP/UDP), so filter that out too for other types.

Signed-off-by: Peter Wu <peter@lekensteyn.nl>

This fixes warnings about conversions to int

smb.c:398: warning: comparison of integers of different signs:
           'ssize_t' (aka 'long') and 'unsigned long'
smb.c:443: warning: comparison of integers of different signs:
           'ssize_t' (aka 'long') and 'unsigned long'

As local files could be accessed through \\localhost\c$.

This patch enables SMB/CIFS support in libcurl.

smb.c:322: warning: conversion to 'short unsigned int' from 'unsigned
           int' may alter its value
smb.c:323: warning: conversion to 'short unsigned int' from 'unsigned
           int' may alter its value
smb.c:482: warning: conversion to 'short unsigned int' from 'int' may
           alter its value
smb.c:521: warning: conversion to 'unsigned int' from 'curl_off_t' may
           alter its value
smb.c:549: warning: conversion to 'unsigned int' from 'curl_off_t' may
           alter its value
smb.c:550: warning: conversion to 'short unsigned int' from 'int' may
           alter its value

smb.c:489: warning: declaration of 'close' shadows a global declaration
smb.c:511: warning: declaration of 'read' shadows a global declaration
smb.c:528: warning: declaration of 'write' shadows a global declaration

smb.c:212: warning: unused parameter 'done'
smb.c:380: warning: ISO C does not allow extra ';' outside of a function
smb.c:812: warning: unused parameter 'premature'
smb.c:822: warning: unused parameter 'dead'

smb.c:311: warning: conversion from 'unsigned __int64' to 'u_short',
           possible loss of data
smb.c:425: warning: conversion from '__int64' to 'unsigned short',
           possible loss of data
smb.c:452: warning: conversion from '__int64' to 'unsigned short',
           possible loss of data

smb.c:162: error: comma at end of enumerator list
smb.c:469: warning: conversion from 'size_t' to 'unsigned short',
           possible loss of data
smb.c:517: warning: conversion from 'curl_off_t' to 'unsigned int',
           possible loss of data
smb.c:545: warning: conversion from 'curl_off_t' to 'unsigned int',
           possible loss of data

Initial implementation of the SMB/CIFS protocol.

Added the SMB and SMBS handler interface structures and associated
functions required for SMB/CIFS operation.

Prefer ! rather than NULL in if statements, added comments and updated
function spacing, argument spacing and line spacing to be more readble.

If the scratch buffer already existed when the CRLF conversion was
performed then the buffer pointer would be checked twice for NULL. This
second check is only necessary if the call to malloc() was performed by
the first check.

Whilst I had moved the dot stuffing code from being performed before
CRLF conversion takes place to after it, in commit 4bd860a0, I had
moved it outside the 'when something read' block of code when meant
it could perform the dot stuffing twice on partial send if nread
happened to contain the right values. It also meant the function could
potentially read past the end of buffer. This was highlighted by the
following warning:

warning: `nread' might be used uninitialized in this function

smb.h:30:16: error: comma at end of enumerator list [-Werror=pedantic]

Added the necessary protocol and port definitions in order to support
SMB/CIFS.

Added the internal definitions and structures necessary for SMB/CIFS
support.

Added the connection structure that will be required in urldata.h for
SMB/CIFS based connections.

Added the initial source files and updated the relevant project files in
order to support SMB/CIFS.

warning: unused variable 'data'
warning: variable 'addcookies' set but not used

...and some very minor coding style policing.

...and some comment typos!

Added support for the automatic conversion of Unix newlines to CRLF
during mail uploads.

Feature: http://curl.haxx.se/bug/view.cgi?id=1456

Reported-by: Brian
Bug: http://curl.haxx.se/bug/view.cgi?id=1455

warning: variable 'connection_id' set but not used
warning: unused parameter 'lineno'