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https://github.com/moparisthebest/curl
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84d2839740
In some situations, it was possible that a transfer was setup to use an specific IP version, but due do DNS caching or connection reuse, it ended up using a different IP version from requested. This commit changes the effect of CURLOPT_IPRESOLVE from simply restricting address resolution to preventing the wrong connection type being used, when choosing a connection from the pool, and to restricting what addresses could be used when establishing a new connection. It is important that all addresses versions are resolved, even if not used in that transfer in particular, because the result is cached, and could be useful for a different transfer with a different CURLOPT_IPRESOLVE setting. Closes #6853
103 lines
4.1 KiB
Groff
103 lines
4.1 KiB
Groff
.\" **************************************************************************
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.\" * _ _ ____ _
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.\" * Project ___| | | | _ \| |
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.\" * / __| | | | |_) | |
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.\" * | (__| |_| | _ <| |___
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.\" * \___|\___/|_| \_\_____|
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.\" *
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.\" * Copyright (C) 1998 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
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.\" *
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.\" * This software is licensed as described in the file COPYING, which
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.\" * you should have received as part of this distribution. The terms
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.\" * are also available at https://curl.se/docs/copyright.html.
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.\" *
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.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
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.\" * copies of the Software, and permit persons to whom the Software is
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.\" * furnished to do so, under the terms of the COPYING file.
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.\" *
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.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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.\" * KIND, either express or implied.
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.\" *
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.\" **************************************************************************
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.\"
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.TH CURLOPT_RESOLVE 3 "19 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options"
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.SH NAME
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CURLOPT_RESOLVE \- provide custom host name to IP address resolves
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_RESOLVE,
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struct curl_slist *hosts);
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.SH DESCRIPTION
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Pass a pointer to a linked list of strings with host name resolve information
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to use for requests with this handle. The linked list should be a fully valid
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list of \fBstruct curl_slist\fP structs properly filled in. Use
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\fIcurl_slist_append(3)\fP to create the list and \fIcurl_slist_free_all(3)\fP
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to clean up an entire list.
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Each single name resolve string should be written using the format
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[+]HOST:PORT:ADDRESS[,ADDRESS]... where HOST is the name libcurl will try
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to resolve, PORT is the port number of the service where libcurl wants
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to connect to the HOST and ADDRESS is one or more numerical IP
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addresses. If you specify multiple ip addresses they need to be
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separated by comma. If libcurl is built to support IPv6, each of the
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ADDRESS entries can of course be either IPv4 or IPv6 style addressing.
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This option effectively pre-populates the DNS cache with entries for the
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host+port pair so redirects and everything that operations against the
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HOST+PORT will instead use your provided ADDRESS.
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The optional leading "+" signifies whether the new entry should time-out or
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not. Entries added with "HOST:..." will never time-out whereas entries added
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with "+HOST:..." will time-out just like ordinary DNS cache entries.
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If the DNS cache already has an entry for the given host+port pair, then
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this entry will be removed and a new entry will be created. This is because
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the old entry may have have different addresses or a different time-out
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setting.
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An ADDRESS provided by this option will only be use if not restricted by
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the setting of \fICURLOPT_IPRESOLVE(3)\fP to a different IP version.
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Remove names from the DNS cache again, to stop providing these fake resolves,
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by including a string in the linked list that uses the format
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\&"-HOST:PORT". The host name must be prefixed with a dash, and the host name
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and port number must exactly match what was already added previously.
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Support for providing the ADDRESS within [brackets] was added in 7.57.0.
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Support for providing multiple IP addresses per entry was added in 7.59.0.
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Support for adding non-permanent entries by using the "+" prefix was added in
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7.75.0.
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.SH DEFAULT
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NULL
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.SH PROTOCOLS
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All
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.SH EXAMPLE
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.nf
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CURL *curl;
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struct curl_slist *host = NULL;
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host = curl_slist_append(NULL, "example.com:80:127.0.0.1");
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curl = curl_easy_init();
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if(curl) {
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curl_easy_setopt(curl, CURLOPT_RESOLVE, host);
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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curl_easy_perform(curl);
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/* always cleanup */
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curl_easy_cleanup(curl);
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}
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curl_slist_free_all(host);
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.fi
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.SH AVAILABILITY
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Added in 7.21.3. Removal support added in 7.42.0.
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.SH RETURN VALUE
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Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
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.SH "SEE ALSO"
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.BR CURLOPT_IPRESOLVE "(3), " CURLOPT_DNS_CACHE_TIMEOUT "(3), " CURLOPT_CONNECT_TO "(3), "
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