cpool: rename "connection cache/conncache" to "Connection Pools/cpool"

This is a better match for what they do and the general "cpool"
var/function prefix works well.

The pool n

cpool: rename "connection cache/conncache" to "Connection Pools/cpool"

This is a better match for what they do and the general "cpool"
var/function prefix works well.

The pool now handles very long hostnames correctly.

The following changes have been made:

* 'struct connectdata', e.g. connections, keep new members
named `destination` and ' destination_len' that fully specifies
interface+port+hostname of where the connection is going to.
This is used in the pool for "bundling" of connections with
the same destination. There is no limit on the length any more.
* Locking: all locks are done inside conncache.c when calling
into the pool and released on return. This eliminates hazards
of the callers keeping track.
* 'struct connectbundle' is now internal to the pool. It is no
longer referenced by a connection.
* 'bundle->multiuse' no longer exists. HTTP/2 and 3 and TLS filters
no longer need to set it. Instead, the multi checks on leaving
MSTATE_CONNECT or MSTATE_CONNECTING if the connection is now
multiplexed and new, e.g. not conn->bits.reuse. In that case
the processing of pending handles is triggered.
* The pool's init is provided with a callback to invoke on all
connections being discarded. This allows the cleanups in
`Curl_disconnect` to run, wherever it is decided to retire
a connection.
* Several pool operations can now be fully done with one call.
Pruning dead connections, upkeep and checks on pool limits
can now directly discard connections and need no longer return
those to the caller for doing that (as we have now the callback
described above).
* Finding a connection for reuse is now done via `Curl_cpool_find()`
and the caller provides callbacks to evaluate the connection
candidates.
* The 'Curl_cpool_check_limits()' now directly uses the max values
that may be set in the transfer's multi. No need to pass them
around. Curl_multi_max_host_connections() and
Curl_multi_max_total_connections() are gone.
* Add method 'Curl_node_llist()' to get the llist a node is in.
Used in cpool to verify connection are indeed in the list (or
not in any list) as they need to.

I left the conncache.[ch] as is for now and also did not touch the
documentation. If we update that outside the feature window, we can
do this in a separate PR.

Multi-thread safety is not achieved by this PR, but since more details
on how pools operate are now "internal" it is a better starting
point to go for this in the future.

Closes #14662

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transfer: Curl_sendrecv() and event related improvements

- Renames Curl_readwrite() to Curl_sendrecv() to reflect that it
is mainly about talking to the server, not reads or writes to

transfer: Curl_sendrecv() and event related improvements

- Renames Curl_readwrite() to Curl_sendrecv() to reflect that it
is mainly about talking to the server, not reads or writes to the
client. Add a `nowp` parameter since the single caller already
has this.
- Curl_sendrecv() now runs all possible operations whenever it is
called and either it had been polling sockets or the 'select_bits'
are set.
POLL_IN/POLL_OUT are not always directly related to send/recv
operations. Filters like HTTP/2, QUIC or TLS may monitor reverse
directions. If a transfer does not want to send (KEEP_SEND), it
will not do so, as before. Same for receives.
- Curl_update_timer() now checks the absolute timestamp of an expiry
and the last/new timeout to determine if the application needs
to stop/start/restart its timer. This fixes edge cases where
updates did not happen as they should have.
- improved --test-event curl_easy_perform() simulation to handle
situations where no sockets are registered but a timeout is
in place.
- fixed bug in events_socket() that complained about removing
a socket that was unknown, when indeed it had removed the socket
just before, only it was the last in the list
- fixed conncache's internal handle to carry the multi instance
(where the cache has one) so that operations on the closure handle
trigger event callbacks correctly.
- fixed conncache to not POLL_REMOVE a socket twice when a conneciton
was closed.

Closes #14561

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urldata: introduce `data->mid`, a unique identifier inside a multi

`data->id` is unique in *most* situations, but not in all. If a libcurl
application uses more than one connection cache

urldata: introduce `data->mid`, a unique identifier inside a multi

`data->id` is unique in *most* situations, but not in all. If a libcurl
application uses more than one connection cache, they will overlap. This
is a rare situations, but libcurl apps do crazy things. However, for
informative things, like tracing, `data->id` is superior, since it
assigns new ids in curl's serial curl_easy_perform() use.

Introduce `data->mid` which is a unique identifer inside one multi
instance, assigned on multi_add_handle() and cleared on
multi_remove_handle().

Use the `mid` in DoH operations and also in h2/h3 stream hashes.

Reported-by: 罗朝辉
Fixes #14414
Closes #14499

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llist: remove direct struct accesses, use only functions

- Turned them all into functions to also do asserts etc.

- The llist related structs got all their fields renamed in order t

llist: remove direct struct accesses, use only functions

- Turned them all into functions to also do asserts etc.

- The llist related structs got all their fields renamed in order to make
sure no existing code remains using direct access.

- Each list node struct now points back to the list it "lives in", so
Curl_node_remove() no longer needs the list pointer.

- Rename the node struct and some of the access functions.

- Added lots of ASSERTs to verify API being used correctly

- Fix some cases of API misuse

Add docs/LLIST.md documenting the internal linked list API.

Closes #14485

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multi: make the "general" list of easy handles a Curl_llist

Instead of having an especially "unique" linked list handler for the
main list of easy handles within the multi handle, this n

multi: make the "general" list of easy handles a Curl_llist

Instead of having an especially "unique" linked list handler for the
main list of easy handles within the multi handle, this now uses a
regular Curl_llist for this as well.

With this change, it is also clearer that every easy handle added to a
multi handle belongs to one and only one out of three different lists:

process - the general one for normal transfer processing

pending - queued up waiting to get a connection (MSTATE_PENDING)

msgsent - transfer completed (MSTATE_MSGSENT)

An easy handle must therefore be removed from the current list before it
gets added to another.

Closes #14474

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tidy-up: OS names

Use these words and casing more consistently across text, comments and
one curl tool output:
AIX, ALPN, ANSI, BSD, Cygwin, Darwin, FreeBSD, GitHub, HP-UX, Linux,

tidy-up: OS names

Use these words and casing more consistently across text, comments and
one curl tool output:
AIX, ALPN, ANSI, BSD, Cygwin, Darwin, FreeBSD, GitHub, HP-UX, Linux,
macOS, MS-DOS, MSYS, MinGW, NTLM, POSIX, Solaris, UNIX, Unix, Unicode,
WINE, WebDAV, Win32, winbind, WinIDN, Windows, Windows CE, Winsock.

Mostly OS names and a few more.

Also a couple of other minor text fixups.

Closes #14360

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code: language cleanup in comments

Based on the standards and guidelines we use for our documentation.

- expand contractions (they're => they are etc)
- host name = > hostname

code: language cleanup in comments

Based on the standards and guidelines we use for our documentation.

- expand contractions (they're => they are etc)
- host name = > hostname
- file name => filename
- user name = username
- man page => manpage
- run-time => runtime
- set-up => setup
- back-end => backend
- a HTTP => an HTTP
- Two spaces after a period => one space after period

Closes #14073

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lib: graceful connection shutdown

When libcurl discards a connection there are two phases this may go
through: "shutdown" and "closing". If a connection is aborted, the
shutdown phas

lib: graceful connection shutdown

When libcurl discards a connection there are two phases this may go
through: "shutdown" and "closing". If a connection is aborted, the
shutdown phase is skipped and it is closed right away.

The connection filters attached to the connection implement the phases
in their `do_shutdown()` and `do_close()` callbacks. Filters carry now a
`shutdown` flags next to `connected` to keep track of the shutdown
operation.

Filters are shut down from top to bottom. If a filter is not connected,
its shutdown is skipped. Notable filters that *do* something during
shutdown are HTTP/2 and TLS. HTTP/2 sends the GOAWAY frame. TLS sends
its close notify and expects to receive a close notify from the server.

As sends and receives may EAGAIN on the network, a shutdown is often not
successful right away and needs to poll the connection's socket(s). To
facilitate this, such connections are placed on a new shutdown list
inside the connection cache.

Since managing this list requires the cooperation of a multi handle,
only the connection cache belonging to a multi handle is used. If a
connection was in another cache when being discarded, it is removed
there and added to the multi's cache. If no multi handle is available at
that time, the connection is shutdown and closed in a one-time,
best-effort attempt.

When a multi handle is destroyed, all connection still on the shutdown
list are discarded with a final shutdown attempt and close. In curl
debug builds, the environment variable `CURL_GRACEFUL_SHUTDOWN` can be
set to make this graceful with a timeout in milliseconds given by the
variable.

The shutdown list is limited to the max number of connections configured
for a multi cache. Set via CURLMOPT_MAX_TOTAL_CONNECTIONS. When the
limit is reached, the oldest connection on the shutdown list is
discarded.

- In multi_wait() and multi_waitfds(), collect all connection caches
involved (each transfer might carry its own) into a temporary list.
Let each connection cache on the list contribute sockets and
POLLIN/OUT events it's connections are waiting for.

- in multi_perform() collect the connection caches the same way and let
them peform their maintenance. This will make another non-blocking
attempt to shutdown all connections on its shutdown list.

- for event based multis (multi->socket_cb set), add the sockets and
their poll events via the callback. When `multi_socket()` is invoked
for a socket not known by an active transfer, forward this to the
multi's cache for processing. On closing a connection, remove its
socket(s) via the callback.

TLS connection filters MUST NOT send close nofity messages in their
`do_close()` implementation. The reason is that a TLS close notify
signals a success. When a connection is aborted and skips its shutdown
phase, the server needs to see a missing close notify to detect
something has gone wrong.

A graceful shutdown of FTP's data connection is performed implicitly
before regarding the upload/download as complete and continuing on the
control connection. For FTP without TLS, there is just the socket close
happening. But with TLS, the sent/received close notify signals that the
transfer is complete and healthy. Servers like `vsftpd` verify that and
reject uploads without a TLS close notify.

- added test_19_* for shutdown related tests
- test_19_01 and test_19_02 test for TCP RST packets
which happen without a graceful shutdown and should
no longer appear otherwise.
- add test_19_03 for handling shutdowns by the server
- add test_19_04 for handling shutdowns by curl
- add test_19_05 for event based shutdowny by server
- add test_30_06/07 and test_31_06/07 for shutdown checks
on FTP up- and downloads.

Closes #13976

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socketpair: add `eventfd` and use `SOCK_NONBLOCK` for `socketpair()`

Currently, we use `pipe` for `wakeup_create`, which requires ***two***
file descriptors. Furthermore, given its compl

socketpair: add `eventfd` and use `SOCK_NONBLOCK` for `socketpair()`

Currently, we use `pipe` for `wakeup_create`, which requires ***two***
file descriptors. Furthermore, given its complexity inside, `pipe` is a
bit heavyweight for just a simple event wait/notify mechanism.

`eventfd` would be a more suitable solution for this kind of scenario,
kernel also advocates for developers to use `eventfd` instead of `pipe`
in some simple use cases:

Applications can use an eventfd file descriptor instead of a pipe
(see pipe(2) in all cases where a pipe is used simply to signal
events. The kernel overhead of an eventfd file descriptor is much
lower than that of a pipe, and only one file descriptor is required
(versus the two required for a pipe).

This change adds the new backend of `eventfd` for `wakeup_create` and
uses it where available, eliminating the overhead of `pipe`. Also, it
optimizes the `wakeup_create` to eliminate the system calls that make
file descriptors non-blocking by moving the logic of setting
non-blocking flags on file descriptors to `socketpair.c` and using
`SOCK_NONBLOCK` for `socketpair(2)`, `EFD_NONBLOCK` for `eventfd(2)`.

Ref:
https://man7.org/linux/man-pages/man7/pipe.7.html
https://man7.org/linux/man-pages/man2/eventfd.2.html
https://man7.org/linux/man-pages/man2/socketpair.2.html
https://www.gnu.org/software/gnulib/manual/html_node/eventfd.html

Closes #13874

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multi: add multi->proto_hash, a key-value store for protocol data

- add `Curl_hash_add2()` that passes a destructor function for
the element added. Call element destructor instead of h

multi: add multi->proto_hash, a key-value store for protocol data

- add `Curl_hash_add2()` that passes a destructor function for
the element added. Call element destructor instead of hash
destructor if present.
- multi: add `proto_hash` for protocol related information,
remove `struct multi_ssl_backend_data`.
- openssl: use multi->proto_hash to keep x509 shared store
- schannel: use multi->proto_hash to keep x509 shared store
- vtls: remove Curl_free_multi_ssl_backend_data() and its
equivalents in the TLS backends

Closes #13345

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wakeup_create: use FD_CLOEXEC/SOCK_CLOEXEC

for `pipe()`/`socketpair()`

Fixes #13618
Closes #13625

multi: introduce SETUP state for better timeouts

Since we can go to the CONNECT state from PENDING, potentially multiple
times for a single transfer, this change introdues a SETUP state

multi: introduce SETUP state for better timeouts

Since we can go to the CONNECT state from PENDING, potentially multiple
times for a single transfer, this change introdues a SETUP state that
happens before CONNECT when doing a new transfer.

Now, doing a redirect on a handle goes back to SETUP (not CONNECT like
before) and we initilize the connect timeout etc in SETUP. Previously,
we would do it in CONNECT but that would make it unreliable in cases
where a transfer goes in and out between CONNECT and PENDING multiple
times.

SETUP is transient, so the handle never actually stays in that state.

Additionally: take care of timeouts of PENDING transfers in
curl_multi_perform()

Ref: #13227
Closes #13371

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llist: add Curl_llist_append()

- use for better readability in all places where the "insert_next"
actually performs an append to the list
- add some tests in unit1300

Clos

llist: add Curl_llist_append()

- use for better readability in all places where the "insert_next"
actually performs an append to the list
- add some tests in unit1300

Closes #13336

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lib: further send/upload handling polish

- Move all the "upload_done" handling to request.c

- add possibility to abort sending of a request
- add `Curl_req_done_sending()` f

lib: further send/upload handling polish

- Move all the "upload_done" handling to request.c

- add possibility to abort sending of a request
- add `Curl_req_done_sending()` for checks
- transfer.c: readwrite_upload() now clean

- removing data->state.ulbuf and data->req.upload_fromhere

- as well as data->req.upload_present
- set data->req.upload_done on having read all from
the client and completely flushed the send buffer

- tftp, remove setting of data->req.upload_fromhere

- serves no purpose as `upload_present` is not set
and the data itself is directly `sendto()` anyway

- smtp, make upload EOB conversion a client reader
- xfer_ulbuf addition

- add xfer_ulbuf for borrowing, similar to xfer_buf
- use in file upload
- use in c-hyper body sending

- h1-proxy, remove init of data->state.uilbuf that is never used
- smb, add own send_buf instead of using data->state.ulbuf

Closes #13010

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multi: add xfer_buf to multi handle

- can be borrowed by transfer during recv-write operation
- needs to be released before borrowing again
- adjustis size to `data->set.buffer_size`

multi: add xfer_buf to multi handle

- can be borrowed by transfer during recv-write operation
- needs to be released before borrowing again
- adjustis size to `data->set.buffer_size`
- used in transfer.c readwrite_data()

Closes #12805

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urldata: make maxconnects a 32 bit value

"2^32 idle connections ought to be enough for anybody"

Closes #12375

multi: remove PENDING + MSGSENT handles from the main linked list

As they are not driving transfers or any socket activity, the main loop
does not need to iterate over these handles. A p

multi: remove PENDING + MSGSENT handles from the main linked list

As they are not driving transfers or any socket activity, the main loop
does not need to iterate over these handles. A performance improvement.

They are instead only held in their own separate lists.

'data->multi' is kept a pointer to the multi handle as long as the easy
handle is actually part of it even when the handle is moved to the
pending/msgsent lists. It needs to know which multi handle it belongs
to, if for example curl_easy_cleanup() is called before the handle is
removed from the multi handle.

Alll 'data->multi' pointers of handles still part of the multi handle
gets cleared by curl_multi_cleanup() which "orphans" all previously
attached easy handles.

This is take 2. The first version was reverted for the 8.0.1 release.

Assisted-by: Stefan Eissing
Closes #10801

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Revert "multi: remove PENDING + MSGSENT handles from the main linked list"

This reverts commit f6d6f3ce01e377932f1ce7c24ee34d45a36950b8.

The commits caused issues in the 8.0.0 relea

Revert "multi: remove PENDING + MSGSENT handles from the main linked list"

This reverts commit f6d6f3ce01e377932f1ce7c24ee34d45a36950b8.

The commits caused issues in the 8.0.0 release. Needs a retake.

Reported-by: Kamil Dudka
Closes #10795

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multi: remove PENDING + MSGSENT handles from the main linked list

As they are not driving transfers or any socket activity, the main loop
does not need to iterate over these handles. A p

multi: remove PENDING + MSGSENT handles from the main linked list

As they are not driving transfers or any socket activity, the main loop
does not need to iterate over these handles. A performance improvement.

They are instead only held in their own separate lists.

Assisted-by: Stefan Eissing
Ref: #10743
Closes #10762

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curl: output warning at --verbose output for debug-enabled version

+ a libcurl warning in the debug output

Assisted-by: Jay Satiro

Ref: https://curl.se/mail/lib-2023-01/003

curl: output warning at --verbose output for debug-enabled version

+ a libcurl warning in the debug output

Assisted-by: Jay Satiro

Ref: https://curl.se/mail/lib-2023-01/0039.html
Closes #10278

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copyright: update all copyright lines and remove year ranges

- they are mostly pointless in all major jurisdictions
- many big corporations and projects already don't use them
- save

copyright: update all copyright lines and remove year ranges

- they are mostly pointless in all major jurisdictions
- many big corporations and projects already don't use them
- saves us from pointless churn
- git keeps history for us
- the year range is kept in COPYING

checksrc is updated to allow non-year using copyright statements

Closes #10205

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multihandle: turn bool struct fields into bits

Closes #10179

openssl: reduce CA certificate bundle reparsing by caching

Closes #9620

hostip: lazily wait to figure out if IPv6 works until needed

The check may take many milliseconds, so now it is performed once the
value is first needed. Also, this change makes sure tha

hostip: lazily wait to figure out if IPv6 works until needed

The check may take many milliseconds, so now it is performed once the
value is first needed. Also, this change makes sure that the value is
not used if the resolve is set to be IPv4-only.

Closes #9553

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copyright: make repository REUSE compliant

Add licensing and copyright information for all files in this repository. This
either happens in the file itself as a comment header or in the

copyright: make repository REUSE compliant

Add licensing and copyright information for all files in this repository. This
either happens in the file itself as a comment header or in the file
`.reuse/dep5`.

This commit also adds a Github workflow to check pull requests and adapts
copyright.pl to the changes.

Closes #8869

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