CURLOPT_DNS_SHUFFLE_ADDRESSES.md (1781B)
1 --- 2 c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. 3 SPDX-License-Identifier: curl 4 Title: CURLOPT_DNS_SHUFFLE_ADDRESSES 5 Section: 3 6 Source: libcurl 7 See-also: 8 - CURLOPT_DNS_CACHE_TIMEOUT (3) 9 - CURLOPT_IPRESOLVE (3) 10 Protocol: 11 - All 12 Added-in: 7.60.0 13 --- 14 15 # NAME 16 17 CURLOPT_DNS_SHUFFLE_ADDRESSES - shuffle IP addresses for hostname 18 19 # SYNOPSIS 20 21 ~~~c 22 #include <curl/curl.h> 23 24 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_SHUFFLE_ADDRESSES, long onoff); 25 ~~~ 26 27 # DESCRIPTION 28 29 Pass a long set to 1 to enable this option. 30 31 When a name is resolved and more than one IP address is returned, this 32 function shuffles the order of all returned addresses so that they are used in 33 a random order. This is similar to the ordering behavior of the legacy 34 gethostbyname function which is no longer used on most platforms. 35 36 Addresses are not reshuffled if name resolution is completed using the DNS 37 cache. CURLOPT_DNS_CACHE_TIMEOUT(3) can be used together with this 38 option to reduce DNS cache timeout or disable caching entirely if frequent 39 reshuffling is needed. 40 41 Since the addresses returned are randomly reordered, the order is not in 42 accordance with RFC 3484 or any other deterministic order that may be 43 generated by the system's name resolution implementation. This may have 44 performance impacts and may cause IPv4 to be used before IPv6 or vice versa. 45 46 # DEFAULT 47 48 0 (disabled) 49 50 # %PROTOCOLS% 51 52 # EXAMPLE 53 54 ~~~c 55 int main(void) 56 { 57 CURL *curl = curl_easy_init(); 58 if(curl) { 59 curl_easy_setopt(curl, CURLOPT_URL, "https://example.com"); 60 curl_easy_setopt(curl, CURLOPT_DNS_SHUFFLE_ADDRESSES, 1L); 61 62 curl_easy_perform(curl); 63 64 /* always cleanup */ 65 curl_easy_cleanup(curl); 66 } 67 } 68 ~~~ 69 70 # %AVAILABILITY% 71 72 # RETURN VALUE 73 74 CURLE_OK or an error such as CURLE_UNKNOWN_OPTION.