curl / Docs / Project / Known Bugs

Known Bugs

This is the document 'docs/KNOWN_BUGS' from the curl release archive.

HTTP

1.2 Multiple methods in a single WWW-Authenticate: header
1.3 STARTTRANSFER time is wrong for HTTP POSTs
1.4 multipart formposts file name encoding
1.5 Expect-100 meets 417
1.6 Unnecessary close when 401 received waiting for 100
1.7 Deflate error after all content was received
1.8 DoH isn't used for all name resolves when enabled
1.9 HTTP/2 frames while in the connection pool kill reuse
1.11 CURLOPT_SEEKFUNCTION not called with CURLFORM_STREAM

TLS

2.1 CURLINFO_SSL_VERIFYRESULT has limited support
2.2 DER in keychain
2.3 Unable to use PKCS12 certificate with Secure Transport
2.4 Secure Transport won't import PKCS#12 client certificates without a password
2.5 Client cert handling with Issuer DN differs between backends
2.6 CURL_GLOBAL_SSL
2.7 Client cert (MTLS) issues with Schannel
2.8 Schannel disable CURLOPT_SSL_VERIFYPEER and verify hostname
2.9 TLS session cache doesn't work with TFO
2.10 Store TLS context per transfer instead of per connection
2.11 Schannel TLS 1.2 handshake bug in old Windows versions
2.12 FTPS with Schannel times out file list operation
2.13 curl with wolfSSL lacks support for renegotiation

Email protocols

3.1 IMAP SEARCH ALL truncated response
3.2 No disconnect command
3.3 POP3 expects "CRLF.CRLF" eob for some single-line responses
3.4 AUTH PLAIN for SMTP is not working on all servers

Command line

4.1 -J and -O with %-encoded file names
4.2 -J with -C - fails
4.3 --retry and transfer timeouts
4.4 Improve --data-urlencode space encoding

Build and portability issues

5.1 OS400 port requires deprecated IBM library
5.2 curl-config --libs contains private details
5.3 curl compiled on OSX 10.13 failed to run on OSX 10.10
5.4 Build with statically built dependency
5.5 can't handle Unicode arguments in non-Unicode builds on Windows
5.7 Visual Studio project gaps
5.8 configure finding libs in wrong directory
5.9 Utilize Requires.private directives in libcurl.pc
5.10 SMB tests fail with Python 2
5.11 configure --with-gssapi with Heimdal is ignored on macOS

Authentication

6.1 NTLM authentication and unicode
6.2 MIT Kerberos for Windows build
6.3 NTLM in system context uses wrong name
6.4 Negotiate and Kerberos V5 need a fake user name
6.5 NTLM doesn't support password with § character
6.6 libcurl can fail to try alternatives with --proxy-any
6.7 Don't clear digest for single realm
6.8 RTSP authentication breaks without redirect support

FTP

7.1 FTP without or slow 220 response
7.2 FTP with CONNECT and slow server
7.3 FTP with NOBODY and FAILONERROR
7.4 FTP with ACCT
7.5 ASCII FTP
7.6 FTP with NULs in URL parts
7.7 FTP and empty path parts in the URL
7.8 Premature transfer end but healthy control channel
7.9 Passive transfer tries only one IP address
7.10 FTPS needs session reuse

TELNET

8.1 TELNET and time limitations don't work
8.2 Microsoft telnet server

SFTP and SCP

9.1 SFTP doesn't do CURLOPT_POSTQUOTE correct
9.2 wolfssh: publickey auth doesn't work

SOCKS

10.3 FTPS over SOCKS
10.4 active FTP over a SOCKS

Internals

11.1 Curl leaks .onion hostnames in DNS
11.2 error buffer not set if connection to multiple addresses fails
11.3 c-ares deviates from stock resolver on http://1346569778
11.4 HTTP test server 'connection-monitor' problems
11.5 Connection information when using TCP Fast Open
11.6 slow connect to localhost on Windows
11.7 signal-based resolver timeouts
11.8 DoH leaks memory after followlocation
11.9 DoH doesn't inherit all transfer options
11.10 Blocking socket operations in non-blocking API
11.11 A shared connection cache is not thread-safe
11.12 'no_proxy' string-matches IPv6 numerical addresses
11.13 wakeup socket disconnect causes havoc

LDAP

12.1 OpenLDAP hangs after returning results
12.2 LDAP on Windows does authentication wrong?
12.3 LDAP on Windows doesn't work
12.4 LDAPS with NSS is slow

TCP/IP

13.1 --interface for ipv6 binds to unusable IP address

DICT

14.1 DICT responses show the underlying protocol

CMake

15.1 use correct SONAME
15.2 support build with GnuTLS
15.3 unusable tool_hugehelp.c with MinGW
15.4 build docs/curl.1
15.5 build on Linux links libcurl to libdl
15.6 uses -lpthread instead of Threads::Threads
15.7 generated .pc file contains strange entries
15.8 libcurl.pc uses absolute library paths
15.9 cert paths autodetected when cross-compiling
15.10 libspsl is not supported


1. HTTP

1.2 Multiple methods in a single WWW-Authenticate: header

The HTTP responses headers WWW-Authenticate: can provide information about multiple authentication methods as multiple headers or as several methods within a single header. The latter way, several methods in the same physical line, is not supported by libcurl's parser. (For no good reason.)

1.3 STARTTRANSFER time is wrong for HTTP POSTs

Wrong STARTTRANSFER timer accounting for POST requests Timer works fine with GET requests, but while using POST the time for CURLINFO_STARTTRANSFER_TIME is wrong. While using POST CURLINFO_STARTTRANSFER_TIME minus CURLINFO_PRETRANSFER_TIME is near to zero every time.

https://github.com/curl/curl/issues/218 https://curl.se/bug/view.cgi?id=1213

1.4 multipart formposts file name encoding

When creating multipart formposts. The file name part can be encoded with something beyond ascii but currently libcurl will only pass in the verbatim string the app provides. There are several browsers that already do this encoding. The key seems to be the updated draft to RFC2231: https://tools.ietf.org/html/draft-reschke-rfc2231-in-http-02

1.5 Expect-100 meets 417

If an upload using Expect: 100-continue receives an HTTP 417 response, it ought to be automatically resent without the Expect:. A workaround is for the client application to redo the transfer after disabling Expect:. https://curl.se/mail/archive-2008-02/0043.html

1.6 Unnecessary close when 401 received waiting for 100

libcurl closes the connection if an HTTP 401 reply is received while it is waiting for the 100-continue response. https://curl.se/mail/lib-2008-08/0462.html

1.7 Deflate error after all content was received

There's a situation where we can get an error in a HTTP response that is compressed, when that error is detected after all the actual body contents have been received and delivered to the application. This is tricky, but is ultimately a broken server.

See https://github.com/curl/curl/issues/2719

1.8 DoH isn't used for all name resolves when enabled

Even if DoH is specified to be used, there are some name resolves that are done without it. This should be fixed. When the internal function `Curl_resolver_wait_resolv()` is called, it doesn't use DoH to complete the resolve as it otherwise should.

See https://github.com/curl/curl/pull/3857 and https://github.com/curl/curl/pull/3850

1.9 HTTP/2 frames while in the connection pool kill reuse

If the server sends HTTP/2 frames (like for example an HTTP/2 PING frame) to curl while the connection is held in curl's connection pool, the socket will be found readable when considered for reuse and that makes curl think it is dead and then it will be closed and a new connection gets created instead.

This is *best* fixed by adding monitoring to connections while they are kept in the pool so that pings can be responded to appropriately.

1.11 CURLOPT_SEEKFUNCTION not called with CURLFORM_STREAM

I'm using libcurl to POST form data using a FILE* with the CURLFORM_STREAM option of curl_formadd(). I've noticed that if the connection drops at just the right time, the POST is reattempted without the data from the file. It seems like the file stream position isn't getting reset to the beginning of the file. I found the CURLOPT_SEEKFUNCTION option and set that with a function that performs an fseek() on the FILE*. However, setting that didn't seem to fix the issue or even get called. See https://github.com/curl/curl/issues/768

2. TLS

2.1 CURLINFO_SSL_VERIFYRESULT has limited support

CURLINFO_SSL_VERIFYRESULT is only implemented for the OpenSSL, NSS and GnuTLS backends, so relying on this information in a generic app is flaky.

2.2 DER in keychain

Curl doesn't recognize certificates in DER format in keychain, but it works with PEM. https://curl.se/bug/view.cgi?id=1065

2.3 Unable to use PKCS12 certificate with Secure Transport

See https://github.com/curl/curl/issues/5403

2.4 Secure Transport won't import PKCS#12 client certificates without a password

libcurl calls SecPKCS12Import with the PKCS#12 client certificate, but that function rejects certificates that do not have a password. https://github.com/curl/curl/issues/1308

2.5 Client cert handling with Issuer DN differs between backends

When the specified client certificate doesn't match any of the server-specified DNs, the OpenSSL and GnuTLS backends behave differently. The github discussion may contain a solution.

See https://github.com/curl/curl/issues/1411

2.6 CURL_GLOBAL_SSL

Since libcurl 7.57.0, the flag CURL_GLOBAL_SSL is a no-op. The change was merged in https://github.com/curl/curl/commit/d661b0afb571a

It was removed since it was

A) never clear for applications on how to deal with init in the light of

different SSL backends (the option was added back in the days when life was simpler)

B) multissl introduced dynamic switching between SSL backends which

emphasized (A) even more

C) libcurl uses some TLS backend functionality even for non-TLS functions (to

get "good" random) so applications trying to avoid the init for performance reasons would do wrong anyway

D) never very carefully documented so all this mostly just happened to work

for some users

However, in spite of the problems with the feature, there were some users who apparently depended on this feature and who now claim libcurl is broken for them. The fix for this situation is not obvious as a downright revert of the patch is totally ruled out due to those reasons above.

https://github.com/curl/curl/issues/2276

2.7 Client cert (MTLS) issues with Schannel

See https://github.com/curl/curl/issues/3145

2.8 Schannel disable CURLOPT_SSL_VERIFYPEER and verify hostname

This seems to be a limitation in the underlying Schannel API.

https://github.com/curl/curl/issues/3284

2.9 TLS session cache doesn't work with TFO

See https://github.com/curl/curl/issues/4301

2.10 Store TLS context per transfer instead of per connection

The GnuTLS `backend->cred` and the OpenSSL `backend->ctx` data and their proxy versions (and possibly other TLS backends), could be better moved to be stored in the Curl_easy handle instead of in per connection so that a single transfer that makes multiple connections can reuse the context and reduce memory consumption.

https://github.com/curl/curl/issues/5102

2.11 Schannel TLS 1.2 handshake bug in old Windows versions

In old versions of Windows such as 7 and 8.1 the Schannel TLS 1.2 handshake implementation likely has a bug that can rarely cause the key exchange to fail, resulting in error SEC_E_BUFFER_TOO_SMALL or SEC_E_MESSAGE_ALTERED.

https://github.com/curl/curl/issues/5488

2.12 FTPS with Schannel times out file list operation

"Instead of the command completing, it just sits there until the timeout expires." - the same command line seems to work with other TLS backends and other operating systems. See https://github.com/curl/curl/issues/5284.

2.13 curl with wolfSSL lacks support for renegotiation

I am using curl (with wolfSSL) to connect https endpoint, but connection with this https endpoint gets terminated because server initiates the renegotiation and client does not handle renegotiation.

See https://github.com/curl/curl/issues/5839

3. Email protocols

3.1 IMAP SEARCH ALL truncated response

IMAP "SEARCH ALL" truncates output on large boxes. "A quick search of the code reveals that pingpong.c contains some truncation code, at line 408, when it deems the server response to be too large truncating it to 40 characters" https://curl.se/bug/view.cgi?id=1366

3.2 No disconnect command

The disconnect commands (LOGOUT and QUIT) may not be sent by IMAP, POP3 and SMTP if a failure occurs during the authentication phase of a connection.

3.3 POP3 expects "CRLF.CRLF" eob for some single-line responses

You have to tell libcurl not to expect a body, when dealing with one line response commands. Please see the POP3 examples and test cases which show this for the NOOP and DELE commands. https://curl.se/bug/?i=740

3.4 AUTH PLAIN for SMTP is not working on all servers

Specifying "--login-options AUTH=PLAIN" on the command line doesn't seem to work correctly.

See https://github.com/curl/curl/issues/4080

4. Command line

4.1 -J and -O with %-encoded file names

-J/--remote-header-name doesn't decode %-encoded file names. RFC6266 details how it should be done. The can of worm is basically that we have no charset handling in curl and ascii >=128 is a challenge for us. Not to mention that decoding also means that we need to check for nastiness that is attempted, like "../" sequences and the like. Probably everything to the left of any embedded slashes should be cut off. https://curl.se/bug/view.cgi?id=1294

-O also doesn't decode %-encoded names, and while it has even less information about the charset involved the process is similar to the -J case.

Note that we won't add decoding to -O without the user asking for it with some other means as well, since -O has always been documented to use the name exactly as specified in the URL.

4.2 -J with -C - fails

When using -J (with -O), automatically resumed downloading together with "-C -" fails. Without -J the same command line works! This happens because the resume logic is worked out before the target file name (and thus its pre-transfer size) has been figured out! https://curl.se/bug/view.cgi?id=1169

4.3 --retry and transfer timeouts

If using --retry and the transfer timeouts (possibly due to using -m or -y/-Y) the next attempt doesn't resume the transfer properly from what was downloaded in the previous attempt but will truncate and restart at the original position where it was at before the previous failed attempt. See https://curl.se/mail/lib-2008-01/0080.html and Mandriva bug report https://qa.mandriva.com/show_bug.cgi?id=22565

4.4 Improve --data-urlencode space encoding

ASCII space characters in --data-urlencode are currently encoded as %20 rather than +, which RFC 1866 says should be used.

See https://github.com/curl/curl/issues/3229

5. Build and portability issues

5.1 OS400 port requires deprecated IBM library

curl for OS400 requires QADRT to build, which provides ASCII wrappers for libc/POSIX functions in the ILE, but IBM no longer supports or even offers this library to download.

See https://github.com/curl/curl/issues/5176

5.2 curl-config --libs contains private details

"curl-config --libs" will include details set in LDFLAGS when configure is run that might be needed only for building libcurl. Further, curl-config --cflags suffers from the same effects with CFLAGS/CPPFLAGS.

5.3 curl compiled on OSX 10.13 failed to run on OSX 10.10

See https://github.com/curl/curl/issues/2905

5.4 Build with statically built dependency

The build scripts in curl (autotools, cmake and others) are primarily done to work with shared/dynamic third party dependencies. When linking with shared libraries, the dependency "chain" is handled automatically by the library loader - on all modern systems.

If you instead link with a static library, we need to provide all the dependency libraries already at the link command line.

Figuring out all the dependency libraries for a given library is hard, as it might also involve figuring out the dependencies of the dependencies and they may vary between platforms and even change between versions.

When using static dependencies, the build scripts will mostly assume that you, the user, will provide all the necessary additional dependency libraries as additional arguments in the build. With configure, by setting LIBS/LDFLAGS on the command line.

We welcome help to improve curl's ability to link with static libraries, but it is likely a task that we can never fully support.

5.5 can't handle Unicode arguments in non-Unicode builds on Windows

If a URL or filename can't be encoded using the user's current codepage then it can only be encoded properly in the Unicode character set. Windows uses UTF-16 encoding for Unicode and stores it in wide characters, however curl and libcurl are not equipped for that at the moment except when built with _UNICODE and UNICODE defined. And, except for Cygwin, Windows can't use UTF-8 as a locale.

https://curl.se/bug/?i=345 https://curl.se/bug/?i=731 https://curl.se/bug/?i=3747

5.7 Visual Studio project gaps

The Visual Studio projects lack some features that the autoconf and nmake builds offer, such as the following:

- support for zlib and nghttp2 - use of static runtime libraries - add the test suite components

In addition to this the following could be implemented:

- support for other development IDEs - add PATH environment variables for third-party DLLs

5.8 configure finding libs in wrong directory

When the configure script checks for third-party libraries, it adds those directories to the LDFLAGS variable and then tries linking to see if it works. When successful, the found directory is kept in the LDFLAGS variable when the script continues to execute and do more tests and possibly check for more libraries.

This can make subsequent checks for libraries wrongly detect another installation in a directory that was previously added to LDFLAGS by another library check!

A possibly better way to do these checks would be to keep the pristine LDFLAGS even after successful checks and instead add those verified paths to a separate variable that only after all library checks have been performed gets appended to LDFLAGS.

5.9 Utilize Requires.private directives in libcurl.pc

https://github.com/curl/curl/issues/864

5.10 SMB tests fail with Python 2

The error message says "TreeConnectAndX not found".

See https://github.com/curl/curl/issues/5983

5.11 configure --with-gssapi with Heimdal is ignored on macOS

... unless you also pass --with-gssapi-libs

https://github.com/curl/curl/issues/3841

6. Authentication

6.1 NTLM authentication and unicode

NTLM authentication involving unicode user name or password only works properly if built with UNICODE defined together with the Schannel backend. The original problem was mentioned in: https://curl.se/mail/lib-2009-10/0024.html https://curl.se/bug/view.cgi?id=896

The Schannel version verified to work as mentioned in https://curl.se/mail/lib-2012-07/0073.html

6.2 MIT Kerberos for Windows build

libcurl fails to build with MIT Kerberos for Windows (KfW) due to KfW's library header files exporting symbols/macros that should be kept private to the KfW library. See ticket #5601 at https://krbdev.mit.edu/rt/

6.3 NTLM in system context uses wrong name

NTLM authentication using SSPI (on Windows) when (lib)curl is running in "system context" will make it use wrong(?) user name - at least when compared to what winhttp does. See https://curl.se/bug/view.cgi?id=535

6.4 Negotiate and Kerberos V5 need a fake user name

In order to get Negotiate (SPNEGO) authentication to work in HTTP or Kerberos V5 in the e-mail protocols, you need to provide a (fake) user name (this concerns both curl and the lib) because the code wrongly only considers authentication if there's a user name provided by setting conn->bits.user_passwd in url.c https://curl.se/bug/view.cgi?id=440 How? https://curl.se/mail/lib-2004-08/0182.html A possible solution is to either modify this variable to be set or introduce a variable such as new conn->bits.want_authentication which is set when any of the authentication options are set.

6.5 NTLM doesn't support password with § character

https://github.com/curl/curl/issues/2120

6.6 libcurl can fail to try alternatives with --proxy-any

When connecting via a proxy using --proxy-any, a failure to establish an authentication will cause libcurl to abort trying other options if the failed method has a higher preference than the alternatives. As an example, --proxy-any against a proxy which advertise Negotiate and NTLM, but which fails to set up Kerberos authentication won't proceed to try authentication using NTLM.

https://github.com/curl/curl/issues/876

6.7 Don't clear digest for single realm

https://github.com/curl/curl/issues/3267

6.8 RTSP authentication breaks without redirect support

RTSP authentication broke in 7.66.0. A work-around is to enable RTSP in CURLOPT_REDIR_PROTOCOLS. Authentication should however not be considered an actual redirect so a "proper" fix needs to be different and not require users to allow redirects to RTSP to work.

See https://github.com/curl/curl/pull/4750

7. FTP

7.1 FTP without or slow 220 response

If a connection is made to a FTP server but the server then just never sends the 220 response or otherwise is dead slow, libcurl will not acknowledge the connection timeout during that phase but only the "real" timeout - which may surprise users as it is probably considered to be the connect phase to most people. Brought up (and is being misunderstood) in: https://curl.se/bug/view.cgi?id=856

7.2 FTP with CONNECT and slow server

When doing FTP over a socks proxy or CONNECT through HTTP proxy and the multi interface is used, libcurl will fail if the (passive) TCP connection for the data transfer isn't more or less instant as the code does not properly wait for the connect to be confirmed. See test case 564 for a first shot at a test case.

7.3 FTP with NOBODY and FAILONERROR

It seems sensible to be able to use CURLOPT_NOBODY and CURLOPT_FAILONERROR with FTP to detect if a file exists or not, but it is not working: https://curl.se/mail/lib-2008-07/0295.html

7.4 FTP with ACCT

When doing an operation over FTP that requires the ACCT command (but not when logging in), the operation will fail since libcurl doesn't detect this and thus fails to issue the correct command: https://curl.se/bug/view.cgi?id=635

7.5 ASCII FTP

FTP ASCII transfers do not follow RFC959. They don't convert the data accordingly (not for sending nor for receiving). RFC 959 section 3.1.1.1 clearly describes how this should be done:

The sender converts the data from an internal character representation to the standard 8-bit NVT-ASCII representation (see the Telnet specification). The receiver will convert the data from the standard form to his own internal form.

Since 7.15.4 at least line endings are converted.

7.6 FTP with NULs in URL parts

FTP URLs passed to curl may contain NUL (0x00) in the RFC 1738 <user>, <password>, and <fpath> components, encoded as "%00". The problem is that curl_unescape does not detect this, but instead returns a shortened C string. From a strict FTP protocol standpoint, NUL is a valid character within RFC 959 <string>, so the way to handle this correctly in curl would be to use a data structure other than a plain C string, one that can handle embedded NUL characters. From a practical standpoint, most FTP servers would not meaningfully support NUL characters within RFC 959 <string>, anyway (e.g., Unix pathnames may not contain NUL).

7.7 FTP and empty path parts in the URL

libcurl ignores empty path parts in FTP URLs, whereas RFC1738 states that such parts should be sent to the server as 'CWD ' (without an argument). The only exception to this rule, is that we knowingly break this if the empty part is first in the path, as then we use the double slashes to indicate that the user wants to reach the root dir (this exception SHALL remain even when this bug is fixed).

7.8 Premature transfer end but healthy control channel

When 'multi_done' is called before the transfer has been completed the normal way, it is considered a "premature" transfer end. In this situation, libcurl closes the connection assuming it doesn't know the state of the connection so it can't be reused for subsequent requests.

With FTP however, this isn't necessarily true but there are a bunch of situations (listed in the ftp_done code) where it *could* keep the connection alive even in this situation - but the current code doesn't. Fixing this would allow libcurl to reuse FTP connections better.

7.9 Passive transfer tries only one IP address

When doing FTP operations through a proxy at localhost, the reported spotted that curl only tried to connect once to the proxy, while it had multiple addresses and a failed connect on one address should make it try the next.

After switching to passive mode (EPSV), curl should try all IP addresses for "localhost". Currently it tries ::1, but it should also try 127.0.0.1.

See https://github.com/curl/curl/issues/1508

7.10 FTPS needs session reuse

When the control connection is reused for a subsequent transfer, some FTPS servers complain about "missing session reuse" for the data channel for the second transfer.

https://github.com/curl/curl/issues/4654

8. TELNET

8.1 TELNET and time limitations don't work

When using telnet, the time limitation options don't work. https://curl.se/bug/view.cgi?id=846

8.2 Microsoft telnet server

There seems to be a problem when connecting to the Microsoft telnet server. https://curl.se/bug/view.cgi?id=649

9. SFTP and SCP

9.1 SFTP doesn't do CURLOPT_POSTQUOTE correct

When libcurl sends CURLOPT_POSTQUOTE commands when connected to a SFTP server using the multi interface, the commands are not being sent correctly and instead the connection is "cancelled" (the operation is considered done) prematurely. There is a half-baked (busy-looping) patch provided in the bug report but it cannot be accepted as-is. See https://curl.se/bug/view.cgi?id=748

9.2 wolfssh: publickey auth doesn't work

When building curl to use the wolfSSH backend for SFTP, the publickey authentication doesn't work. This is simply functionality not written for curl yet, the necessary API for make this work is provided by wolfSSH.

See https://github.com/curl/curl/issues/4820

10. SOCKS

10.3 FTPS over SOCKS

libcurl doesn't support FTPS over a SOCKS proxy.

10.4 active FTP over a SOCKS

libcurl doesn't support active FTP over a SOCKS proxy

11. Internals

11.1 Curl leaks .onion hostnames in DNS

Curl sends DNS requests for hostnames with a .onion TLD. This leaks information about what the user is attempting to access, and violates this requirement of RFC7686: https://tools.ietf.org/html/rfc7686

Issue: https://github.com/curl/curl/issues/543

11.2 error buffer not set if connection to multiple addresses fails

If you ask libcurl to resolve a hostname like example.com to IPv6 addresses only. But you only have IPv4 connectivity. libcurl will correctly fail with CURLE_COULDNT_CONNECT. But the error buffer set by CURLOPT_ERRORBUFFER remains empty. Issue: https://github.com/curl/curl/issues/544

11.3 c-ares deviates from stock resolver on http://1346569778

When using the socket resolvers, that URL becomes:

 * Rebuilt URL to: http://1346569778/
 * Trying 80.67.6.50...

but with c-ares it instead says "Could not resolve: 1346569778 (Domain name not found)"

See https://github.com/curl/curl/issues/893

11.4 HTTP test server 'connection-monitor' problems

The 'connection-monitor' feature of the sws HTTP test server doesn't work properly if some tests are run in unexpected order. Like 1509 and then 1525.

See https://github.com/curl/curl/issues/868

11.5 Connection information when using TCP Fast Open

CURLINFO_LOCAL_PORT (and possibly a few other) fails when TCP Fast Open is enabled.

See https://github.com/curl/curl/issues/1332 and https://github.com/curl/curl/issues/4296

11.6 slow connect to localhost on Windows

When connecting to "localhost" on Windows, curl will resolve the name for both ipv4 and ipv6 and try to connect to both happy eyeballs-style. Something in there does however make it take 200 milliseconds to succeed - which is the HAPPY_EYEBALLS_TIMEOUT define exactly. Lowering that define speeds up the connection, suggesting a problem in the HE handling.

If we can *know* that we're talking to a local host, we should lower the happy eyeballs delay timeout for IPv6 (related: hardcode the "localhost" addresses, mentioned in TODO). Possibly we should reduce that delay for all.

https://github.com/curl/curl/issues/2281

11.7 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 https://curl.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.

11.8 DoH leaks memory after followlocation

https://github.com/curl/curl/issues/4592

11.9 DoH doesn't inherit all transfer options

https://github.com/curl/curl/issues/4578

11.10 Blocking socket operations in non-blocking API

The list of blocking socket operations is in TODO section "More non-blocking".

11.11 A shared connection cache is not thread-safe

The share interface offers CURL_LOCK_DATA_CONNECT to have multiple easy handle share a connection cache, but due to how connections are used they are still not thread-safe when used shared.

See https://github.com/curl/curl/issues/4915 and lib1541.c

11.12 'no_proxy' string-matches IPv6 numerical addresses

This has the downside that "::1" for example doesn't match "::0:1" even though they are in fact the same address.

See https://github.com/curl/curl/issues/5745

11.13 wakeup socket disconnect causes havoc

waking an iPad breaks the wakeup socket pair, triggering a POLLIN event and resulting in SOCKERRNO being set to ENOTCONN.

This condition, and other possible error conditions on the wakeup socket, are not handled, so the condition remains on the FD and curl_multi_poll will never block again.

See https://github.com/curl/curl/issues/6132 and https://github.com/curl/curl/pull/6133

12. LDAP

12.1 OpenLDAP hangs after returning results

By configuration defaults, openldap automatically chase referrals on secondary socket descriptors. The OpenLDAP backend is asynchronous and thus should monitor all socket descriptors involved. Currently, these secondary descriptors are not monitored, causing openldap library to never receive data from them.

As a temporary workaround, disable referrals chasing by configuration.

The fix is not easy: proper automatic referrals chasing requires a synchronous bind callback and monitoring an arbitrary number of socket descriptors for a single easy handle (currently limited to 5).

Generic LDAP is synchronous: OK.

See https://github.com/curl/curl/issues/622 and

 https://curl.se/mail/lib-2016-01/0101.html

12.2 LDAP on Windows does authentication wrong?

https://github.com/curl/curl/issues/3116

12.3 LDAP on Windows doesn't work

A simple curl command line getting "ldap://ldap.forumsys.com" returns an error that says "no memory" !

https://github.com/curl/curl/issues/4261

12.4 LDAPS with NSS is slow

See https://github.com/curl/curl/issues/5874

13. TCP/IP

13.1 --interface for ipv6 binds to unusable IP address

Since IPv6 provides a lot of addresses with different scope, binding to an IPv6 address needs to take the proper care so that it doesn't bind to a locally scoped address as that is bound to fail.

https://github.com/curl/curl/issues/686

14. DICT

14.1 DICT responses show the underlying protocol

When getting a DICT response, the protocol parts of DICT aren't stripped off from the output.

https://github.com/curl/curl/issues/1809

15. CMake

15.1 use correct SONAME

The autotools build sets the SONAME properly according to VERSIONINFO in lib/Makefile.am and so should cmake to make comparable build.

See https://github.com/curl/curl/pull/5935

15.2 support build with GnuTLS

15.3 unusable tool_hugehelp.c with MinGW

see https://github.com/curl/curl/issues/3125

15.4 build docs/curl.1

The cmake build doesn't create the docs/curl.1 file and therefor must rely on it being there already. This makes the --manual option not work and test cases like 1139 can't function.

15.5 build on Linux links libcurl to libdl

... which it shouldn't need to!

See https://github.com/curl/curl/issues/6165

15.6 uses -lpthread instead of Threads::Threads

See https://github.com/curl/curl/issues/6166

15.7 generated .pc file contains strange entries

The Libs.private field of the generated .pc file contains -lgcc -lgcc_s -lc -lgcc -lgcc_s

See https://github.com/curl/curl/issues/6167

15.8 libcurl.pc uses absolute library paths

The libcurl.pc file generated by cmake contains things like Libs.private: /usr/lib64/libssl.so /usr/lib64/libcrypto.so /usr/lib64/libz.so. The autotools equivalent would say Libs.private: -lssl -lcrypto -lz

See https://github.com/curl/curl/issues/6169

15.9 cert paths autodetected when cross-compiling

The autotools build disables the ca_path/ca_bundle detection when cross-compiling. The cmake build keeps doing the detection.

See https://github.com/curl/curl/issues/6178

15.10 libspsl is not supported

See https://github.com/curl/curl/issues/6214