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curl/docs/TODO
Daniel Stenberg b790bdf46b TODO: consider supporting STAT
2014-10-28 22:31:48 +01:00

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Things that could be nice to do in the future
Things to do in project cURL. Please tell us what you think, contribute and
send us patches that improve things!
All bugs documented in the KNOWN_BUGS document are subject for fixing!
1. libcurl
1.2 More data sharing
1.3 struct lifreq
1.4 signal-based resolver timeouts
1.5 get rid of PATH_MAX
1.6 Modified buffer size approach
1.7 Detect when called from within callbacks
1.8 Allow SSL (HTTPS) to proxy
2. libcurl - multi interface
2.1 More non-blocking
2.2 Fix HTTP Pipelining for PUT
3. Documentation
3.1 Update date and version in man pages
4. FTP
4.1 HOST
4.2 Alter passive/active on failure and retry
4.3 Earlier bad letter detection
4.4 REST for large files
4.5 ASCII support
4.6 GSSAPI via Windows SSPI
4.7 STAT for LIST without data connection
5. HTTP
5.1 Better persistency for HTTP 1.0
5.2 support FF3 sqlite cookie files
5.3 Rearrange request header order
5.4 SPDY
5.5 auth= in URLs
5.6 Digest via Windows SSPI
6. TELNET
6.1 ditch stdin
6.2 ditch telnet-specific select
6.3 feature negotiation debug data
6.4 send data in chunks
7. SMTP
7.1 Pipelining
7.2 Enhanced capability support
8. POP3
8.1 Pipelining
8.2 Enhanced capability support
9. IMAP
9.1 Enhanced capability support
10. LDAP
10.1 SASL based authentication mechanisms
11. New protocols
11.1 RSYNC
12. SSL
12.1 Disable specific versions
12.2 Provide mutex locking API
12.3 Evaluate SSL patches
12.4 Cache OpenSSL contexts
12.5 Export session ids
12.6 Provide callback for cert verification
12.7 improve configure --with-ssl
12.8 Support DANE
13. GnuTLS
13.1 SSL engine stuff
13.2 check connection
14. SASL
14.1 Other authentication mechanisms
14.2 GSSAPI via GSS-API libraries
15. Client
15.1 sync
15.2 glob posts
15.3 prevent file overwriting
15.4 simultaneous parallel transfers
15.5 provide formpost headers
15.6 warning when setting an option
16. Build
16.1 roffit
17. Test suite
17.1 SSL tunnel
17.2 nicer lacking perl message
17.3 more protocols supported
17.4 more platforms supported
17.5 Add support for concurrent connections
18. Next SONAME bump
18.1 http-style HEAD output for FTP
18.2 combine error codes
18.3 extend CURLOPT_SOCKOPTFUNCTION prototype
19. Next major release
19.1 cleanup return codes
19.2 remove obsolete defines
19.3 size_t
19.4 remove several functions
19.5 remove CURLOPT_FAILONERROR
19.6 remove CURLOPT_DNS_USE_GLOBAL_CACHE
19.7 remove progress meter from libcurl
19.8 remove 'curl_httppost' from public
19.9 have form functions use CURL handle argument
19.10 Add CURLOPT_MAIL_CLIENT option
==============================================================================
1. libcurl
1.2 More data sharing
curl_share_* functions already exist and work, and they can be extended to
share more. For example, enable sharing of the ares channel and the
connection cache.
1.3 struct lifreq
Use 'struct lifreq' and SIOCGLIFADDR instead of 'struct ifreq' and
SIOCGIFADDR on newer Solaris versions as they claim the latter is obsolete.
To support ipv6 interface addresses for network interfaces properly.
1.4 signal-based resolver timeouts
libcurl built without an asynchronous resolver library uses alarm() to time
out DNS lookups. When a timeout occurs, this causes libcurl to jump from the
signal handler back into the library with a sigsetjmp, which effectively
causes libcurl to continue running within the signal handler. This is
non-portable and could cause problems on some platforms. A discussion on the
problem is available at http://curl.haxx.se/mail/lib-2008-09/0197.html
Also, alarm() provides timeout resolution only to the nearest second. alarm
ought to be replaced by setitimer on systems that support it.
1.5 get rid of PATH_MAX
Having code use and rely on PATH_MAX is not nice:
http://insanecoding.blogspot.com/2007/11/pathmax-simply-isnt.html
Currently the SSH based code uses it a bit, but to remove PATH_MAX from there
we need libssh2 to properly tell us when we pass in a too small buffer and
its current API (as of libssh2 1.2.7) doesn't.
1.6 Modified buffer size approach
Current libcurl allocates a fixed 16K size buffer for download and an
additional 16K for upload. They are always unconditionally part of the easy
handle. If CRLF translations are requested, an additional 32K "scratch
buffer" is allocated. A total of 64K transfer buffers in the worst case.
First, while the handles are not actually in use these buffers could be freed
so that lingering handles just kept in queues or whatever waste less memory.
Secondly, SFTP is a protocol that needs to handle many ~30K blocks at once
since each need to be individually acked and therefore libssh2 must be
allowed to send (or receive) many separate ones in parallel to achieve high
transfer speeds. A current libcurl build with a 16K buffer makes that
impossible, but one with a 512K buffer will reach MUCH faster transfers. But
allocating 512K unconditionally for all buffers just in case they would like
to do fast SFTP transfers at some point is not a good solution either.
Dynamically allocate buffer size depending on protocol in use in combination
with freeing it after each individual transfer? Other suggestions?
1.7 Detect when called from within callbacks
We should set a state variable before calling callbacks, so that we
subsequently can add code within libcurl that returns error if called within
callbacks for when that's not supported.
1.8 Allow SSL (HTTPS) to proxy
To prevent local users from snooping on your traffic to the proxy. Supported
by Chrome already:
http://www.chromium.org/developers/design-documents/secure-web-proxy
...and by Firefox soon:
https://bugzilla.mozilla.org/show_bug.cgi?id=378637
2. libcurl - multi interface
2.1 More non-blocking
Make sure we don't ever loop because of non-blocking sockets returning
EWOULDBLOCK or similar. Blocking cases include:
- Name resolves on non-windows unless c-ares is used
- NSS SSL connections
- HTTP proxy CONNECT operations
- SOCKS proxy handshakes
- file:// transfers
- TELNET transfers
- The "DONE" operation (post transfer protocol-specific actions) for the
protocols SFTP, SMTP, FTP. Fixing Curl_done() for this is a worthy task.
2.2 Fix HTTP Pipelining for PUT
HTTP Pipelining can be a way to greatly enhance performance for multiple
serial requests and currently libcurl only supports that for HEAD and GET
requests but it should also be possible for PUT.
3. Documentation
3.1 Update date and version in man pages
'maketgz' or another suitable script could update the .TH sections of the man
pages at release time to use the current date and curl/libcurl version
number.
4. FTP
4.1 HOST
HOST is a command for a client to tell which host name to use, to offer FTP
servers named-based virtual hosting:
http://tools.ietf.org/html/rfc7151
4.2 Alter passive/active on failure and retry
When trying to connect passively to a server which only supports active
connections, libcurl returns CURLE_FTP_WEIRD_PASV_REPLY and closes the
connection. There could be a way to fallback to an active connection (and
vice versa). http://curl.haxx.se/bug/feature.cgi?id=1754793
4.3 Earlier bad letter detection
Make the detection of (bad) %0d and %0a codes in FTP URL parts earlier in the
process to avoid doing a resolve and connect in vain.
4.4 REST for large files
REST fix for servers not behaving well on >2GB requests. This should fail if
the server doesn't set the pointer to the requested index. The tricky
(impossible?) part is to figure out if the server did the right thing or not.
4.5 ASCII support
FTP ASCII transfers do not follow RFC959. They don't convert the data
accordingly.
4.6 GSSAPI via Windows SSPI
In addition to currently supporting the SASL GSSAPI mechanism (Kerberos V5)
via third-party GSS-API libraries, such as Heimdal or MIT Kerberos, also add
support for GSSAPI authentication via Windows SSPI.
4.7 STAT for LIST without data connection
Some FTP servers allow STAT for listing directories instead of using LIST, and
the response is then sent over the control connection instead of as the
otherwise usedw data connection: http://www.nsftools.com/tips/RawFTP.htm#STAT
This is not detailed in any FTP specification.
5. HTTP
5.1 Better persistency for HTTP 1.0
"Better" support for persistent connections over HTTP 1.0
http://curl.haxx.se/bug/feature.cgi?id=1089001
5.2 support FF3 sqlite cookie files
Firefox 3 is changing from its former format to a a sqlite database instead.
We should consider how (lib)curl can/should support this.
http://curl.haxx.se/bug/feature.cgi?id=1871388
5.3 Rearrange request header order
Server implementors often make an effort to detect browser and to reject
clients it can detect to not match. One of the last details we cannot yet
control in libcurl's HTTP requests, which also can be exploited to detect
that libcurl is in fact used even when it tries to impersonate a browser, is
the order of the request headers. I propose that we introduce a new option in
which you give headers a value, and then when the HTTP request is built it
sorts the headers based on that number. We could then have internally created
headers use a default value so only headers that need to be moved have to be
specified.
5.4 SPDY
Chrome and Firefox already support SPDY and lots of web services do. There's
a library for us to use for this (spdylay) that has a similar API and the
same author as nghttp2.
spdylay: https://github.com/tatsuhiro-t/spdylay
5.5 auth= in URLs
Add the ability to specify the preferred authentication mechanism to use by
using ;auth=<mech> in the login part of the URL.
For example:
http://test:pass;auth=NTLM@example.com would be equivalent to specifying --user
test:pass;auth=NTLM or --user test:pass --ntlm from the command line.
Additionally this should be implemented for proxy base URLs as well.
5.6 Digest via Windows SSPI
libcurl already supports HTTP Digest Authentication via native routines as well
as SASL Digest via both Windows SSPI and native routines. In addition to this
libcurl should also support HTTP Digest Authentication via Windows SSPI.
6. TELNET
6.1 ditch stdin
Reading input (to send to the remote server) on stdin is a crappy solution for
library purposes. We need to invent a good way for the application to be able
to provide the data to send.
6.2 ditch telnet-specific select
Move the telnet support's network select() loop go away and merge the code
into the main transfer loop. Until this is done, the multi interface won't
work for telnet.
6.3 feature negotiation debug data
Add telnet feature negotiation data to the debug callback as header data.
6.4 send data in chunks
Currently, telnet sends data one byte at a time. This is fine for interactive
use, but inefficient for any other. Sent data should be sent in larger
chunks.
7. SMTP
7.1 Pipelining
Add support for pipelining emails.
7.2 Enhanced capability support
Add the ability, for an application that uses libcurl, to obtain the list of
capabilities returned from the EHLO command.
8. POP3
8.1 Pipelining
Add support for pipelining commands.
8.2 Enhanced capability support
Add the ability, for an application that uses libcurl, to obtain the list of
capabilities returned from the CAPA command.
9. IMAP
9.1 Enhanced capability support
Add the ability, for an application that uses libcurl, to obtain the list of
capabilities returned from the CAPABILITY command.
10. LDAP
10.1 SASL based authentication mechanisms
Currently the LDAP module only supports ldap_simple_bind_s() in order to bind
to an LDAP server. However, this function sends username and password details
using the simple authentication mechanism (as clear text). However, it should
be possible to use ldap_bind_s() instead specifying the security context
information ourselves.
11. New protocols
11.1 RSYNC
There's no RFC for the protocol or an URI/URL format. An implementation
should most probably use an existing rsync library, such as librsync.
12. SSL
12.1 Disable specific versions
Provide an option that allows for disabling specific SSL versions, such as
SSLv2 http://curl.haxx.se/bug/feature.cgi?id=1767276
12.2 Provide mutex locking API
Provide a libcurl API for setting mutex callbacks in the underlying SSL
library, so that the same application code can use mutex-locking
independently of OpenSSL or GnutTLS being used.
12.3 Evaluate SSL patches
Evaluate/apply Gertjan van Wingerde's SSL patches:
http://curl.haxx.se/mail/lib-2004-03/0087.html
12.4 Cache OpenSSL contexts
"Look at SSL cafile - quick traces look to me like these are done on every
request as well, when they should only be necessary once per SSL context (or
once per handle)". The major improvement we can rather easily do is to make
sure we don't create and kill a new SSL "context" for every request, but
instead make one for every connection and re-use that SSL context in the same
style connections are re-used. It will make us use slightly more memory but
it will libcurl do less creations and deletions of SSL contexts.
12.5 Export session ids
Add an interface to libcurl that enables "session IDs" to get
exported/imported. Cris Bailiff said: "OpenSSL has functions which can
serialise the current SSL state to a buffer of your choice, and recover/reset
the state from such a buffer at a later date - this is used by mod_ssl for
apache to implement and SSL session ID cache".
12.6 Provide callback for cert verification
OpenSSL supports a callback for customised verification of the peer
certificate, but this doesn't seem to be exposed in the libcurl APIs. Could
it be? There's so much that could be done if it were!
12.7 improve configure --with-ssl
make the configure --with-ssl option first check for OpenSSL, then GnuTLS,
then NSS...
12.8 Support DANE
DNS-Based Authentication of Named Entities (DANE) is a way to provide SSL
keys and certs over DNS using DNSSEC as an alternative to the CA model.
http://www.rfc-editor.org/rfc/rfc6698.txt
An initial patch was posted by Suresh Krishnaswamy on March 7th 2013
(http://curl.haxx.se/mail/lib-2013-03/0075.html) but it was a too simple
approach. See Daniel's comments:
http://curl.haxx.se/mail/lib-2013-03/0103.html . libunbound may be the
correct library to base this development on.
13. GnuTLS
13.1 SSL engine stuff
Is this even possible?
13.2 check connection
Add a way to check if the connection seems to be alive, to correspond to the
SSL_peak() way we use with OpenSSL.
14. SASL
14.1 Other authentication mechanisms
Add support for other authentication mechanisms such as EXTERNAL, OLP,
GSS-SPNEGO and others.
14.2 GSSAPI via GSS-API libraries
Add support for GSSAPI authentication via third-party GSS-API libraries, such
as Heimdal and MIT Kerberos.
15. Client
15.1 sync
"curl --sync http://example.com/feed[1-100].rss" or
"curl --sync http://example.net/{index,calendar,history}.html"
Downloads a range or set of URLs using the remote name, but only if the
remote file is newer than the local file. A Last-Modified HTTP date header
should also be used to set the mod date on the downloaded file.
15.2 glob posts
Globbing support for -d and -F, as in 'curl -d "name=foo[0-9]" URL'.
This is easily scripted though.
15.3 prevent file overwriting
Add an option that prevents cURL from overwriting existing local files. When
used, and there already is an existing file with the target file name
(either -O or -o), a number should be appended (and increased if already
existing). So that index.html becomes first index.html.1 and then
index.html.2 etc.
15.4 simultaneous parallel transfers
The client could be told to use maximum N simultaneous parallel transfers and
then just make sure that happens. It should of course not make more than one
connection to the same remote host. This would require the client to use the
multi interface. http://curl.haxx.se/bug/feature.cgi?id=1558595
15.5 provide formpost headers
Extending the capabilities of the multipart formposting. How about leaving
the ';type=foo' syntax as it is and adding an extra tag (headers) which
works like this: curl -F "coolfiles=@fil1.txt;headers=@fil1.hdr" where
fil1.hdr contains extra headers like
Content-Type: text/plain; charset=KOI8-R"
Content-Transfer-Encoding: base64
X-User-Comment: Please don't use browser specific HTML code
which should overwrite the program reasonable defaults (plain/text,
8bit...)
15.6 warning when setting an option
Display a warning when libcurl returns an error when setting an option.
This can be useful to tell when support for a particular feature hasn't been
compiled into the library.
16. Build
16.1 roffit
Consider extending 'roffit' to produce decent ASCII output, and use that
instead of (g)nroff when building src/tool_hugehelp.c
17. Test suite
17.1 SSL tunnel
Make our own version of stunnel for simple port forwarding to enable HTTPS
and FTP-SSL tests without the stunnel dependency, and it could allow us to
provide test tools built with either OpenSSL or GnuTLS
17.2 nicer lacking perl message
If perl wasn't found by the configure script, don't attempt to run the tests
but explain something nice why it doesn't.
17.3 more protocols supported
Extend the test suite to include more protocols. The telnet could just do FTP
or http operations (for which we have test servers).
17.4 more platforms supported
Make the test suite work on more platforms. OpenBSD and Mac OS. Remove
fork()s and it should become even more portable.
17.5 Add support for concurrent connections
Tests 836, 882 and 938 were designed to verify that separate connections aren't
used when using different login credentials in protocols that shouldn't re-use
a connection under such circumstances.
Unfortunately, ftpserver.pl doesn't appear to support multiple concurrent
connections. The read while() loop seems to loop until it receives a disconnect
from the client, where it then enters the waiting for connections loop. When
the client opens a second connection to the server, the first connection hasn't
been dropped (unless it has been forced - which we shouldn't do in these tests)
and thus the wait for connections loop is never entered to receive the second
connection.
18. Next SONAME bump
18.1 http-style HEAD output for FTP
#undef CURL_FTP_HTTPSTYLE_HEAD in lib/ftp.c to remove the HTTP-style headers
from being output in NOBODY requests over FTP
18.2 combine error codes
Combine some of the error codes to remove duplicates. The original
numbering should not be changed, and the old identifiers would be
macroed to the new ones in an CURL_NO_OLDIES section to help with
backward compatibility.
Candidates for removal and their replacements:
CURLE_FILE_COULDNT_READ_FILE => CURLE_REMOTE_FILE_NOT_FOUND
CURLE_FTP_COULDNT_RETR_FILE => CURLE_REMOTE_FILE_NOT_FOUND
CURLE_FTP_COULDNT_USE_REST => CURLE_RANGE_ERROR
CURLE_FUNCTION_NOT_FOUND => CURLE_FAILED_INIT
CURLE_LDAP_INVALID_URL => CURLE_URL_MALFORMAT
CURLE_TFTP_NOSUCHUSER => CURLE_TFTP_ILLEGAL
CURLE_TFTP_NOTFOUND => CURLE_REMOTE_FILE_NOT_FOUND
CURLE_TFTP_PERM => CURLE_REMOTE_ACCESS_DENIED
18.3 extend CURLOPT_SOCKOPTFUNCTION prototype
The current prototype only provides 'purpose' that tells what the
connection/socket is for, but not any protocol or similar. It makes it hard
for applications to differentiate on TCP vs UDP and even HTTP vs FTP and
similar.
19. Next major release
19.1 cleanup return codes
curl_easy_cleanup() returns void, but curl_multi_cleanup() returns a
CURLMcode. These should be changed to be the same.
19.2 remove obsolete defines
remove obsolete defines from curl/curl.h
19.3 size_t
make several functions use size_t instead of int in their APIs
19.4 remove several functions
remove the following functions from the public API:
curl_getenv
curl_mprintf (and variations)
curl_strequal
curl_strnequal
They will instead become curlx_ - alternatives. That makes the curl app
still capable of using them, by building with them from source.
These functions have no purpose anymore:
curl_multi_socket
curl_multi_socket_all
19.5 remove CURLOPT_FAILONERROR
Remove support for CURLOPT_FAILONERROR, it has gotten too kludgy and weird
internally. Let the app judge success or not for itself.
19.6 remove CURLOPT_DNS_USE_GLOBAL_CACHE
Remove support for a global DNS cache. Anything global is silly, and we
already offer the share interface for the same functionality but done
"right".
19.7 remove progress meter from libcurl
The internally provided progress meter output doesn't belong in the library.
Basically no application wants it (apart from curl) but instead applications
can and should do their own progress meters using the progress callback.
The progress callback should then be bumped as well to get proper 64bit
variable types passed to it instead of doubles so that big files work
correctly.
19.8 remove 'curl_httppost' from public
curl_formadd() was made to fill in a public struct, but the fact that the
struct is public is never really used by application for their own advantage
but instead often restricts how the form functions can or can't be modified.
Changing them to return a private handle will benefit the implementation and
allow us much greater freedoms while still maintaining a solid API and ABI.
19.9 have form functions use CURL handle argument
curl_formadd() and curl_formget() both currently have no CURL handle
argument, but both can use a callback that is set in the easy handle, and
thus curl_formget() with callback cannot function without first having
curl_easy_perform() (or similar) called - which is hard to grasp and a design
mistake.
19.10 Add CURLOPT_MAIL_CLIENT option
Rather than use the URL to specify the mail client string to present in the
HELO and EHLO commands, libcurl should support a new CURLOPT specifically for
specifying this data as the URL is non-standard and to be honest a bit of a
hack ;-)
Please see the following thread for more information:
http://curl.haxx.se/mail/lib-2012-05/0178.html
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