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d95f3dc0b1
This patch adds CURLOPT_DNS_SHUFFLE_ADDRESSES to explicitly request shuffling of IP addresses returned for a hostname when there is more than one. This is useful when the application knows that a round robin approach is appropriate and is willing to accept the consequences of potentially discarding some preference order returned by the system's implementation. Closes #1694
70 lines
2.7 KiB
Groff
70 lines
2.7 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 - 2018, 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.haxx.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_DNS_SHUFFLE_ADDRESSES 3 "3 March 2018" "libcurl 7.60.0" "curl_easy_setopt options"
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.SH NAME
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CURLOPT_DNS_SHUFFLE_ADDRESSES \- Shuffle addresses when a hostname returns more than one
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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_DNS_SHUFFLE_ADDRESSES, long onoff);
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.fi
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.SH DESCRIPTION
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When a name is resolved and more than one IP address is returned, shuffle the
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order of all returned addresses so that they will be used in a random order.
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This is similar to the ordering behavior of gethostbyname which is no longer
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used on most platforms.
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Addresses will not be reshuffled if a name resolution is completed using the
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DNS cache. \fICURLOPT_DNS_CACHE_TIMEOUT(3)\fP can be used together with this
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option to reduce DNS cache timeout or disable caching entirely if frequent
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reshuffling is needed.
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Since the addresses returned will be reordered randomly, their order will not
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be in accordance with RFC 3484 or any other deterministic order that may be
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generated by the system's name resolution implementation. This may have
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performance impacts and may cause IPv4 to be used before IPv6 or vice versa.
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.SH DEFAULT
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0 (disabled)
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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 = curl_easy_init();
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if(curl) {
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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curl_easy_setopt(curl, CURLOPT_DNS_SHUFFLE_ADDRESSES, 1L);
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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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.fi
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.SH AVAILABILITY
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Added in 7.60.0
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.SH RETURN VALUE
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CURLE_OK or an error such as CURLE_UNKNOWN_OPTION.
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.SH "SEE ALSO"
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.BR CURLOPT_DNS_CACHE_TIMEOUT "(3), " CURLOPT_IPRESOLVE "(3), "
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