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4f99efb192
- Detach and disconnect an attached connection before performing. Prior to this change it was not possible to safely reuse an easy handle with an attached connection in a second call to curl_easy_perform. The only known case of this is a connect-only type handle where the connection was detached when curl_easy_perform returned, only to be reattached by either curl_easy_send/recv. This commit effectively reverts2f8ecd5dandbe82a360, the latter of which treated the reuse as an error. Prior to that change undefined behavior may occur in such a case. Bug: https://curl.se/mail/lib-2025-01/0044.html Reported-by: Aleksander Mazur Closes https://github.com/curl/curl/pull/16008
89 lines
2.1 KiB
Markdown
89 lines
2.1 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLOPT_CONNECT_ONLY
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Section: 3
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Source: libcurl
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See-also:
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- CURLOPT_HTTPPROXYTUNNEL (3)
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- CURLOPT_VERBOSE (3)
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- curl_easy_recv (3)
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- curl_easy_send (3)
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Protocol:
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- All
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Added-in: 7.15.2
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---
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# NAME
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CURLOPT_CONNECT_ONLY - stop when connected to target server
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CONNECT_ONLY, long only);
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~~~
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# DESCRIPTION
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Pass a long. If the parameter equals 1, it tells the library to perform all
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the required proxy authentication and connection setup, but no data transfer,
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and then return.
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The option can be used to simply test a connection to a server, but is more
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useful when used with the CURLINFO_ACTIVESOCKET(3) option to
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curl_easy_getinfo(3) as the library can set up the connection and then
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the application can obtain the most recently used socket for special data
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transfers.
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Since 7.86.0, this option can be set to '2' and if HTTP or WebSocket are used,
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libcurl performs the request and reads all response headers before handing
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over control to the application.
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Transfers marked connect only do not reuse any existing connections and
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connections marked connect only are not allowed to get reused.
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If the connect only transfer is done using the multi interface, the particular
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easy handle must remain added to the multi handle for as long as the
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application wants to use it. Once it has been removed with
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curl_multi_remove_handle(3), curl_easy_send(3) and
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curl_easy_recv(3) do not function.
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# DEFAULT
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0
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# %PROTOCOLS%
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# EXAMPLE
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~~~c
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int main(void)
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{
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CURL *curl = curl_easy_init();
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if(curl) {
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CURLcode ret;
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
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curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
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ret = curl_easy_perform(curl);
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if(ret == CURLE_OK) {
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/* only connected */
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}
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}
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}
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~~~
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# HISTORY
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WS and WSS support added in 7.86.0.
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# %AVAILABILITY%
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# RETURN VALUE
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curl_easy_setopt(3) returns a CURLcode indicating success or error.
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CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
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libcurl-errors(3).
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