This patch invokes two socket connect()s nearly simultaneously, and
the socket that is first connected "wins" and is subsequently used for
the connection. The other is terminated.

There is a very slight IPv4 preference, in that if both sockets connect
simultaneously IPv4 is checked first and thus will win.

This is a regression since the switch to always-multi internally
c4312741.

Test 1316 was modified since we now clearly call the Curl_client_write()
function when doing the LIST transfer part and then the
handler->protocol says FTP and ftpc.transfertype is 'A' which implies
text converting even though that the response is initially a HTTP
CONNECT response in this case.

As a remedy to the problem when a socket gets closed and a new one is
opened with the same file descriptor number and as a result
multi.c:singlesocket() doesn't detect the difference, the new function
Curl_multi_closed() gets told when a socket is closed so that it can be
removed from the socket hash. When the old one has been removed, a new
socket should be detected fine by the singlesocket() on next invoke.

Bug: http://curl.haxx.se/bug/view.cgi?id=1248
Reported-by: Erik Johansson

The code within #ifdef HAVE_SOCKADDR_IN6_SIN6_SCOPE_ID wrongly had two
closing braces when it should only have one, so builds without that
define would fail.

Bug: http://curl.haxx.se/mail/lib-2013-05/0000.html

MacOS X doesn't have TCP_KEEPIDLE/TCP_KEEPINTVL but only a single
TCP_KEEPALIVE (see
http://developer.apple.com/library/mac/#DOCUMENTATION/Darwin/Reference/ManPages/man4/tcp.4.html).
Here is a patch for CURLOPT_TCP_KEEPIDLE on OSX platforms.

I am using curl_easy_setopt(CURLOPT_INTERFACE, "if!something") to force
transfers to use a particular interface but the transfer fails with
CURLE_INTERFACE_FAILED, "Failed binding local connection end" if the
interface I specify has no IPv6 address. The cause is as follows:

The remote hostname resolves successfully and has an IPv6 address and an
IPv4 address.

cURL attempts to connect to the IPv6 address first.

bindlocal (in lib/connect.c) fails because Curl_if2ip cannot find an
IPv6 address on the interface.

This is a fatal error in singleipconnect()

This change will make cURL try the next IP address in the list.

Also included are two changes related to IPv6 address scope:

- Filter the choice of address in Curl_if2ip to only consider addresses
with the same scope ID as the connection address (mismatched scope for
local and remote address does not result in a working connection).

- bindlocal was ignoring the scope ID of addresses returned by
Curl_if2ip . Now it uses them.

Bug: http://curl.haxx.se/bug/view.cgi?id=1189

The Microsoft knowledge-base article
http://support.microsoft.com/kb/823764 describes how to use SNDBUF to
overcome a performance shortcoming in winsock, but it doesn't apply to
Windows Vista and later versions. If the described SNDBUF magic is
applied when running on those more recent Windows versions, it seems to
instead have the reversed effect in many cases and thus make libcurl
perform less good on those systems.

This fix thus adds a run-time version-check that does the SNDBUF magic
conditionally depending if it is deemed necessary or not.

Bug: http://curl.haxx.se/bug/view.cgi?id=1188
Reported by: Andrew Kurushin
Tested by: Christian Hägele

Patch by: Robert Wruck
Bug: http://curl.haxx.se/bug/view.cgi?id=1209

The 56b7c87c change left a case where a good sockfd was not copied to
*sockp before returning with CURLE_OK

pointed out by clang-analyzer

Remove timeout argument that's never used.

Make the actual connection get detected on a single spot to reduce code
duplication.

Store the IPv6 state already when the connection is attempted.

Remove internal separated behavior of the easy vs multi intercace.
curl_easy_perform() is now using the multi interface itself.

Several minor multi interface quirks and bugs have been fixed in the
process.

Much help with debugging this has been provided by: Yang Tse

This commit renames lib/setup.h to lib/curl_setup.h and
renames lib/setup_once.h to lib/curl_setup_once.h.

Removes the need and usage of a header inclusion guard foreign
to libcurl. [1]

Removes the need and presence of an alarming notice we carried
in old setup_once.h [2]

----------------------------------------

1 - lib/setup_once.h used __SETUP_ONCE_H macro as header inclusion guard
    up to commit ec691ca3 which changed this to HEADER_CURL_SETUP_ONCE_H,
    this single inclusion guard is enough to ensure that inclusion of
    lib/setup_once.h done from lib/setup.h is only done once.

    Additionally lib/setup.h has always used __SETUP_ONCE_H macro to
    protect inclusion of setup_once.h even after commit ec691ca3, this
    was to avoid a circular header inclusion triggered when building a
    c-ares enabled version with c-ares sources available which also has
    a setup_once.h header. Commit ec691ca3 exposes the real nature of
    __SETUP_ONCE_H usage in lib/setup.h, it is a header inclusion guard
    foreign to libcurl belonging to c-ares's setup_once.h

    The renaming this commit does, fixes the circular header inclusion,
    and as such removes the need and usage of a header inclusion guard
    foreign to libcurl. Macro __SETUP_ONCE_H no longer used in libcurl.

2 - Due to the circular interdependency of old lib/setup_once.h and the
    c-ares setup_once.h header, old file lib/setup_once.h has carried
    back from 2006 up to now days an alarming and prominent notice about
    the need of keeping libcurl's and c-ares's setup_once.h in sync.

    Given that this commit fixes the circular interdependency, the need
    and presence of mentioned notice is removed.

    All mentioned interdependencies come back from now old days when
    the c-ares project lived inside a curl subdirectory. This commit
    removes last traces of such fact.

This reverts renaming and usage of lib/*.h header files done
28-12-2012, reverting 2 commits:

  f871de00... build: make use of 76 lib/*.h renamed files
  ffd8e127... build: rename 76 lib/*.h files

This also reverts removal of redundant include guard (redundant thanks
to changes in above commits) done 2-12-2013, reverting 1 commit:

  c087374c... curl_setup.h: remove redundant include guard

This also reverts renaming and usage of lib/*.c source files done
3-12-2013, reverting 3 commits:

  13606bbf... build: make use of 93 lib/*.c renamed files
  5b6e7927... build: rename 93 lib/*.c files
  7d83dfff... build: commit 13606bbf follow-up 1

Start of related discussion thread:

  http://curl.haxx.se/mail/lib-2013-01/0012.html

Asking for confirmation on pushing this revertion commit:

  http://curl.haxx.se/mail/lib-2013-01/0048.html

Confirmation summary:

  http://curl.haxx.se/mail/lib-2013-01/0079.html

NOTICE: The list of 2 files that have been modified by other
intermixed commits, while renamed, and also by at least one
of the 6 commits this one reverts follows below. These 2 files
will exhibit a hole in history unless git's '--follow' option
is used when viewing logs.

  lib/curl_imap.h
  lib/curl_smtp.h

93 lib/*.c source files renamed to use our standard naming scheme.

This commit only does the file renaming.

----------------------------------------

  renamed:    lib/amigaos.c -> lib/curl_amigaos.c
  renamed:    lib/asyn-ares.c -> lib/curl_asyn_ares.c
  renamed:    lib/asyn-thread.c -> lib/curl_asyn_thread.c
  renamed:    lib/axtls.c -> lib/curl_axtls.c
  renamed:    lib/base64.c -> lib/curl_base64.c
  renamed:    lib/bundles.c -> lib/curl_bundles.c
  renamed:    lib/conncache.c -> lib/curl_conncache.c
  renamed:    lib/connect.c -> lib/curl_connect.c
  renamed:    lib/content_encoding.c -> lib/curl_content_encoding.c
  renamed:    lib/cookie.c -> lib/curl_cookie.c
  renamed:    lib/cyassl.c -> lib/curl_cyassl.c
  renamed:    lib/dict.c -> lib/curl_dict.c
  renamed:    lib/easy.c -> lib/curl_easy.c
  renamed:    lib/escape.c -> lib/curl_escape.c
  renamed:    lib/file.c -> lib/curl_file.c
  renamed:    lib/fileinfo.c -> lib/curl_fileinfo.c
  renamed:    lib/formdata.c -> lib/curl_formdata.c
  renamed:    lib/ftp.c -> lib/curl_ftp.c
  renamed:    lib/ftplistparser.c -> lib/curl_ftplistparser.c
  renamed:    lib/getenv.c -> lib/curl_getenv.c
  renamed:    lib/getinfo.c -> lib/curl_getinfo.c
  renamed:    lib/gopher.c -> lib/curl_gopher.c
  renamed:    lib/gtls.c -> lib/curl_gtls.c
  renamed:    lib/hash.c -> lib/curl_hash.c
  renamed:    lib/hmac.c -> lib/curl_hmac.c
  renamed:    lib/hostasyn.c -> lib/curl_hostasyn.c
  renamed:    lib/hostcheck.c -> lib/curl_hostcheck.c
  renamed:    lib/hostip.c -> lib/curl_hostip.c
  renamed:    lib/hostip4.c -> lib/curl_hostip4.c
  renamed:    lib/hostip6.c -> lib/curl_hostip6.c
  renamed:    lib/hostsyn.c -> lib/curl_hostsyn.c
  renamed:    lib/http.c -> lib/curl_http.c
  renamed:    lib/http_chunks.c -> lib/curl_http_chunks.c
  renamed:    lib/http_digest.c -> lib/curl_http_digest.c
  renamed:    lib/http_negotiate.c -> lib/curl_http_negotiate.c
  renamed:    lib/http_negotiate_sspi.c -> lib/curl_http_negotiate_sspi.c
  renamed:    lib/http_proxy.c -> lib/curl_http_proxy.c
  renamed:    lib/idn_win32.c -> lib/curl_idn_win32.c
  renamed:    lib/if2ip.c -> lib/curl_if2ip.c
  renamed:    lib/imap.c -> lib/curl_imap.c
  renamed:    lib/inet_ntop.c -> lib/curl_inet_ntop.c
  renamed:    lib/inet_pton.c -> lib/curl_inet_pton.c
  renamed:    lib/krb4.c -> lib/curl_krb4.c
  renamed:    lib/krb5.c -> lib/curl_krb5.c
  renamed:    lib/ldap.c -> lib/curl_ldap.c
  renamed:    lib/llist.c -> lib/curl_llist.c
  renamed:    lib/md4.c -> lib/curl_md4.c
  renamed:    lib/md5.c -> lib/curl_md5.c
  renamed:    lib/memdebug.c -> lib/curl_memdebug.c
  renamed:    lib/mprintf.c -> lib/curl_mprintf.c
  renamed:    lib/multi.c -> lib/curl_multi.c
  renamed:    lib/netrc.c -> lib/curl_netrc.c
  renamed:    lib/non-ascii.c -> lib/curl_non_ascii.c
  renamed:    lib/curl_non-ascii.h -> lib/curl_non_ascii.h
  renamed:    lib/nonblock.c -> lib/curl_nonblock.c
  renamed:    lib/nss.c -> lib/curl_nss.c
  renamed:    lib/nwlib.c -> lib/curl_nwlib.c
  renamed:    lib/nwos.c -> lib/curl_nwos.c
  renamed:    lib/openldap.c -> lib/curl_openldap.c
  renamed:    lib/parsedate.c -> lib/curl_parsedate.c
  renamed:    lib/pingpong.c -> lib/curl_pingpong.c
  renamed:    lib/polarssl.c -> lib/curl_polarssl.c
  renamed:    lib/pop3.c -> lib/curl_pop3.c
  renamed:    lib/progress.c -> lib/curl_progress.c
  renamed:    lib/qssl.c -> lib/curl_qssl.c
  renamed:    lib/rawstr.c -> lib/curl_rawstr.c
  renamed:    lib/rtsp.c -> lib/curl_rtsp.c
  renamed:    lib/security.c -> lib/curl_security.c
  renamed:    lib/select.c -> lib/curl_select.c
  renamed:    lib/sendf.c -> lib/curl_sendf.c
  renamed:    lib/share.c -> lib/curl_share.c
  renamed:    lib/slist.c -> lib/curl_slist.c
  renamed:    lib/smtp.c -> lib/curl_smtp.c
  renamed:    lib/socks.c -> lib/curl_socks.c
  renamed:    lib/socks_gssapi.c -> lib/curl_socks_gssapi.c
  renamed:    lib/socks_sspi.c -> lib/curl_socks_sspi.c
  renamed:    lib/speedcheck.c -> lib/curl_speedcheck.c
  renamed:    lib/splay.c -> lib/curl_splay.c
  renamed:    lib/ssh.c -> lib/curl_ssh.c
  renamed:    lib/sslgen.c -> lib/curl_sslgen.c
  renamed:    lib/ssluse.c -> lib/curl_ssluse.c
  renamed:    lib/strdup.c -> lib/curl_strdup.c
  renamed:    lib/strequal.c -> lib/curl_strequal.c
  renamed:    lib/strerror.c -> lib/curl_strerror.c
  renamed:    lib/strtok.c -> lib/curl_strtok.c
  renamed:    lib/strtoofft.c -> lib/curl_strtoofft.c
  renamed:    lib/telnet.c -> lib/curl_telnet.c
  renamed:    lib/tftp.c -> lib/curl_tftp.c
  renamed:    lib/timeval.c -> lib/curl_timeval.c
  renamed:    lib/transfer.c -> lib/curl_transfer.c
  renamed:    lib/url.c -> lib/curl_url.c
  renamed:    lib/version.c -> lib/curl_version.c
  renamed:    lib/warnless.c -> lib/curl_warnless.c
  renamed:    lib/wildcard.c -> lib/curl_wildcard.c

----------------------------------------

76 private header files renamed to use our standard naming scheme.

This change affects 322 files in libcurl's source tree.

Inclusion of top two most included header files now done in setup_once.h

A bundle is a list of all persistent connections to the same host.
The connection cache consists of a hash of bundles, with the
hostname as the key.
The benefits may not be obvious, but they are two:

1) Faster search for connections to reuse, since the hash
   lookup only finds connections to the host in question.
2) It lays out the groundworks for an upcoming patch,
   which will introduce multiple HTTP pipelines.

This patch also removes the awkward list of "closure handles",
which were needed to send QUIT commands to the FTP server
when closing a connection.
Now we allocate a separate closure handle and use that
one to close all connections.

This has been tested in a live system for a few weeks, and of
course passes the test suite.

DragonFly uses milliseconds, while our API and Linux use full seconds.

Reported by: John Marino
Bug: http://curl.haxx.se/bug/view.cgi?id=3546257

This reverts commit 9c94236e.

It didn't server its purpose, so lets go back to long-time working code.

Fixed warning: dereferencing pointer does break strict-aliasing rules
by using a union instead of separate pointer variables.
Internal union sockaddr_u could probably be moved to generic header.
Thanks to Paul Howarth for the hint about using unions for this.

Important for winbuild: Separate declaration of sockaddr_u pointer.
The pointer variable *sock cannot be declared and initialized right
after the union declaration. Therefore it has to be a separate statement.

Commit 9109cdec brought this regression (shipped since 7.24.0).

The singleipconnect() function must not return an error if Curl_socket()
returns an error. It should then simply return OK and pass a SOCKET_BAD
back simply because that is how the user of this function expects it to
work and something else is not fine.

Reported by: Blaise Potard
Bug: http://curl.haxx.se/bug/view.cgi?id=3516508

Curl_socket returns CURLE_COULDNT_CONNECT when the opensocket callback
returns CURL_SOCKET_BAD. Previous return value CURLE_FAILED_INIT
conveys incorrect information to the user.

This adds three new options to control the behavior of TCP keepalives:

- CURLOPT_TCP_KEEPALIVE: enable/disable probes
- CURLOPT_TCP_KEEPIDLE: idle time before sending first probe
- CURLOPT_TCP_KEEPINTVL: delay between successive probes

While not all operating systems support the TCP_KEEPIDLE and
TCP_KEEPINTVL knobs, the library will still allow these options to be
set by clients, silently ignoring the values.

When connecting to a domain with multiple IP addresses, allow different,
decreasing connection timeout values. This should guarantee some
connections attempts with sufficiently long timeouts, while still
providing fallback.

First off the timeout for accepting a server connect back must of course
respect a global timeout. Then the timeleft function is only used by ftp
code so it was moved to ftp.c and made static.

1- Two new error codes are introduced.

CURLE_FTP_ACCEPT_FAILED to be set whenever ACCEPTing fails because of
FTP server connected.

CURLE_FTP_ACCEPT_TIMEOUT to be set whenever ACCEPTing timeouts.

Neither of these errors are considered fatal and control connection
remains OK because it could just be a firewall blocking server to
connect to the client.

2- One new setopt option was introduced.

CURLOPT_ACCEPTTIMEOUT_MS

It sets the maximum amount of time FTP client is going to wait for a
server to connect. Internal default accept timeout is 60 seconds.

Do not try to resolve interfaces names via DNS by recognizing interface
names in a few ways.  If the interface option argument has a prefix of
"if!" then treat the argument as only an interface.  Similarly, if the
interface argument is the name of an interface (even if it does not have
an IP address assigned), treat it as an interface name.  Finally, if the
interface argument is prefixed by "host!" treat it as a hostname that
must be resolved by /etc/hosts or DNS.

These changes allow a client using the multi interfaces to avoid
blocking on name resolution if the interface loses its IP address or
disappears.

As a follow-up from commit d5b5f64b, clear the sock_accepted status
when such a socket is closed to avoid a re-used connection to retain the
state wrongly.

Bug: http://curl.haxx.se/mail/lib-2011-12/0079.html

Keep track of which sockets that are the result of accept() calls and
refuse to call the closesocket callback for those sockets. Test case 596
now verifies that the open socket callback is called the same number of
times as the closed socket callback for active FTP connections.

Bug: http://curl.haxx.se/mail/lib-2011-12/0018.html
Reported by: Gokhan Sengun

When the new socket is created for an active connection, it is now done
using the open socket callback.

Test case 596 was modified to run fine, although it hides the fact that
the close callback is still called too many times, as it also gets
called for closing sockets that were created with accept().