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resolve: add CURLOPT_DNS_SHUFFLE_ADDRESSES

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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
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Rick Deist 2018-03-17 20:10:04 +01:00 • committed by Daniel Stenberg
parent fb4f568b1e
commit d95f3dc0b1
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14 changed files with 270 additions and 3 deletions
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2
docs/libcurl/curl_easy_setopt.3
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@ -468,6 +468,8 @@ Bind name resolves to this IP4 address. See \fICURLOPT_DNS_LOCAL_IP4(3)\fP
Bind name resolves to this IP6 address. See \fICURLOPT_DNS_LOCAL_IP6(3)\fP
.IP CURLOPT_DNS_SERVERS
Preferred DNS servers. See \fICURLOPT_DNS_SERVERS(3)\fP
.IP CURLOPT_DNS_SHUFFLE_ADDRESSES
Shuffle addresses before use. See \fICURLOPT_DNS_SHUFFLE_ADDRESSES(3)\fP
.IP CURLOPT_ACCEPTTIMEOUT_MS
Timeout for waiting for the server's connect back to be accepted. See \fICURLOPT_ACCEPTTIMEOUT_MS(3)\fP
.IP CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS

69
docs/libcurl/opts/CURLOPT_DNS_SHUFFLE_ADDRESSES.3 Normal file
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@ -0,0 +1,69 @@
.\" **************************************************************************
.\" * _ _ ____ _
.\" * Project ___| | | | _ \| |
.\" * / __| | | | |_) | |
.\" * | (__| |_| | _ <| |___
.\" * \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" *
.\" * This software is licensed as described in the file COPYING, which
.\" * you should have received as part of this distribution. The terms
.\" * are also available at https://curl.haxx.se/docs/copyright.html.
.\" *
.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
.\" * copies of the Software, and permit persons to whom the Software is
.\" * furnished to do so, under the terms of the COPYING file.
.\" *
.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
.\" * KIND, either express or implied.
.\" *
.\" **************************************************************************
.\"
.TH CURLOPT_DNS_SHUFFLE_ADDRESSES 3 "3 March 2018" "libcurl 7.60.0" "curl_easy_setopt options"
.SH NAME
CURLOPT_DNS_SHUFFLE_ADDRESSES \- Shuffle addresses when a hostname returns more than one
.SH SYNOPSIS
.nf
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_SHUFFLE_ADDRESSES, long onoff);
.fi
.SH DESCRIPTION
When a name is resolved and more than one IP address is returned, shuffle the
order of all returned addresses so that they will be used in a random order.
This is similar to the ordering behavior of gethostbyname which is no longer
used on most platforms.
Addresses will not be reshuffled if a name resolution is completed using the
DNS cache. \fICURLOPT_DNS_CACHE_TIMEOUT(3)\fP can be used together with this
option to reduce DNS cache timeout or disable caching entirely if frequent
reshuffling is needed.
Since the addresses returned will be reordered randomly, their order will not
be in accordance with RFC 3484 or any other deterministic order that may be
generated by the system's name resolution implementation. This may have
performance impacts and may cause IPv4 to be used before IPv6 or vice versa.
.SH DEFAULT
0 (disabled)
.SH PROTOCOLS
All
.SH EXAMPLE
.nf
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
curl_easy_setopt(curl, CURLOPT_DNS_SHUFFLE_ADDRESSES, 1L);
curl_easy_perform(curl);
/* always cleanup */
curl_easy_cleanup(curl);
}
.fi
.SH AVAILABILITY
Added in 7.60.0
.SH RETURN VALUE
CURLE_OK or an error such as CURLE_UNKNOWN_OPTION.
.SH "SEE ALSO"
.BR CURLOPT_DNS_CACHE_TIMEOUT "(3), " CURLOPT_IPRESOLVE "(3), "

1
docs/libcurl/opts/Makefile.inc
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@ -112,6 +112,7 @@ man_MANS = \
CURLOPT_DNS_LOCAL_IP4.3 \
CURLOPT_DNS_LOCAL_IP6.3 \
CURLOPT_DNS_SERVERS.3 \
CURLOPT_DNS_SHUFFLE_ADDRESSES.3 \
CURLOPT_DNS_USE_GLOBAL_CACHE.3 \
CURLOPT_EGDSOCKET.3 \
CURLOPT_ERRORBUFFER.3 \

1
docs/libcurl/symbols-in-versions
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@ -373,6 +373,7 @@ CURLOPT_DNS_INTERFACE 7.33.0
CURLOPT_DNS_LOCAL_IP4 7.33.0
CURLOPT_DNS_LOCAL_IP6 7.33.0
CURLOPT_DNS_SERVERS 7.24.0
CURLOPT_DNS_SHUFFLE_ADDRESSES 7.60.0
CURLOPT_DNS_USE_GLOBAL_CACHE 7.9.3 7.11.1
CURLOPT_EGDSOCKET 7.7
CURLOPT_ENCODING 7.10