126 lines
3.3 KiB
Markdown
126 lines
3.3 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLOPT_PREREQFUNCTION
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Section: 3
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Source: libcurl
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See-also:
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- CURLINFO_PRIMARY_IP (3)
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- CURLINFO_PRIMARY_PORT (3)
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- CURLOPT_PREREQDATA (3)
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---
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# NAME
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CURLOPT_PREREQFUNCTION - user callback called when a connection has been
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established, but before a request has been made.
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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/* These are the return codes for the pre-request callback. */
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#define CURL_PREREQFUNC_OK 0
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#define CURL_PREREQFUNC_ABORT 1 /* fail the entire transfer */
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int prereq_callback(void *clientp,
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char *conn_primary_ip,
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char *conn_local_ip,
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int conn_primary_port,
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int conn_local_port);
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PREREQFUNCTION, prereq_callback);
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~~~
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# DESCRIPTION
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Pass a pointer to your callback function, which should match the prototype
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shown above.
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This function gets called by libcurl after a connection has been established
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or a connection has been reused (including any SSL handshaking), but before any
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request is actually made on the connection. For example, for HTTP, this
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callback is called once a connection has been established to the server, but
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before a GET/HEAD/POST/etc request has been sent.
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This function may be called multiple times if redirections are enabled and are
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being followed (see CURLOPT_FOLLOWLOCATION(3)).
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The callback function must return *CURL_PREREQFUNC_OK* on success, or
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*CURL_PREREQFUNC_ABORT* to cause the transfer to fail.
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This function is passed the following arguments:
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## `conn_primary_ip`
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A null-terminated pointer to a C string containing the primary IP of the
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remote server established with this connection. For FTP, this is the IP for
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the control connection. IPv6 addresses are represented without surrounding
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brackets.
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## `conn_local_ip`
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A null-terminated pointer to a C string containing the originating IP for this
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connection. IPv6 addresses are represented without surrounding brackets.
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## `conn_primary_port`
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The primary port number on the remote server established with this connection.
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For FTP, this is the port for the control connection. This can be a TCP or a
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UDP port number depending on the protocol.
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## `conn_local_port`
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The originating port number for this connection. This can be a TCP or a UDP
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port number depending on the protocol.
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## `clientp`
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The pointer you set with CURLOPT_PREREQDATA(3).
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# DEFAULT
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By default, this is NULL and unused.
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# PROTOCOLS
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ALL
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# EXAMPLE
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~~~c
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struct priv {
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void *custom;
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};
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static int prereq_callback(void *clientp,
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char *conn_primary_ip,
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char *conn_local_ip,
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int conn_primary_port,
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int conn_local_port)
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{
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printf("Connection made to %s:%d\n", conn_primary_ip, conn_primary_port);
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return CURL_PREREQFUNC_OK;
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}
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int main(void)
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{
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struct priv prereq_data;
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CURL *curl = curl_easy_init();
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if(curl) {
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curl_easy_setopt(curl, CURLOPT_PREREQFUNCTION, prereq_callback);
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curl_easy_setopt(curl, CURLOPT_PREREQDATA, &prereq_data);
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curl_easy_perform(curl);
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}
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}
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~~~
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# AVAILABILITY
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Added in 7.80.0
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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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