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cURL > Docs > TODO

TODO -- what to expect of the curl future

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

libcurl - multi interface

2.1 More non-blocking
2.2 Fix HTTP Pipelining for PUT

Documentation

3.1 Update date and version in man pages

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

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

TELNET

6.1 ditch stdin
6.2 ditch telnet-specific select
6.3 feature negotiation debug data
6.4 send data in chunks

SMTP

7.1 Pipelining
7.2 Enhanced capability support

POP3

8.1 Pipelining
8.2 Enhanced capability support

IMAP

9.1 Enhanced capability support

LDAP

10.1 SASL based authentication mechanisms

New protocols

11.1 RSYNC

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

GnuTLS

13.1 SSL engine stuff
13.2 check connection

SASL

14.1 Other authentication mechanisms

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

Build

16.1 roffit

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

Next SONAME bump

18.1 http-style HEAD output for FTP
18.2 combine error codes
18.3 extend CURLOPT_SOCKOPTFUNCTION prototype

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.

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.

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 GSSAPI to SMTP, POP3 and IMAP.

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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