116 lines
3 KiB
Markdown
116 lines
3 KiB
Markdown
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---
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c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLOPT_RESOLVE
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Section: 3
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Source: libcurl
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See-also:
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- CURLOPT_CONNECT_TO (3)
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- CURLOPT_DNS_CACHE_TIMEOUT (3)
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- CURLOPT_IPRESOLVE (3)
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---
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# NAME
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CURLOPT_RESOLVE - provide custom hostname to IP address resolves
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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_RESOLVE,
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struct curl_slist *hosts);
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~~~
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# DESCRIPTION
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Pass a pointer to a linked list of strings with hostname 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 **struct curl_slist** structs properly filled in. Use
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curl_slist_append(3) to create the list and curl_slist_free_all(3) to clean up
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an entire list.
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Each resolve rule to add should be written using the format
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~~~c
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[+]HOST:PORT:ADDRESS[,ADDRESS]
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~~~
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HOST is the name libcurl wants to resolve, PORT is the port number of the
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service where libcurl wants to connect to the HOST and ADDRESS is one or more
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numerical IP 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 ADDRESS
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entries can of course be either IPv4 or IPv6 style addressing.
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This option effectively populates the DNS cache with entries for the host+port
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pair so redirects and everything that operations against the HOST+PORT instead
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use your provided ADDRESS.
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The optional leading "+" specifies that the new entry should time-out. Entries
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added without the leading plus character never times out whereas entries added
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with "+HOST:..." times 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, the new
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entry overrides the former one.
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An ADDRESS provided by this option is only used if not restricted by the
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setting of CURLOPT_IPRESOLVE(3) to a different IP version.
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To remove names from the DNS cache again, to stop providing these fake
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resolves, include a string in the linked list that uses the format
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~~~c
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-HOST:PORT
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~~~
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The entry to remove must be prefixed with a dash, and the hostname and port
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number must exactly match what was added previously.
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# DEFAULT
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NULL
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# PROTOCOLS
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All
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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;
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struct curl_slist *host = NULL;
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host = curl_slist_append(NULL, "example.com:443:127.0.0.1");
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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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}
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~~~
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# AVAILABILITY
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Added in 7.21.3. Removal support added in 7.42.0.
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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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# RETURN VALUE
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Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
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