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134 lines
5.0 KiB
Groff
134 lines
5.0 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) 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.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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.\" * SPDX-License-Identifier: curl
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.\" *
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.\" **************************************************************************
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.\"
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.TH CURLOPT_SOCKOPTFUNCTION 3 "16 Jun 2014" libcurl libcurl
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.SH NAME
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CURLOPT_SOCKOPTFUNCTION \- callback for setting socket options
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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typedef enum {
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CURLSOCKTYPE_IPCXN, /* socket created for a specific IP connection */
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CURLSOCKTYPE_ACCEPT, /* socket created by accept() call */
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CURLSOCKTYPE_LAST /* never use */
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} curlsocktype;
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#define CURL_SOCKOPT_OK 0
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#define CURL_SOCKOPT_ERROR 1 /* causes libcurl to abort and return
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CURLE_ABORTED_BY_CALLBACK */
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#define CURL_SOCKOPT_ALREADY_CONNECTED 2
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int sockopt_callback(void *clientp,
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curl_socket_t curlfd,
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curlsocktype purpose);
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
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.SH 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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When set, this callback function gets called by libcurl when the socket has
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been created, but before the connect call to allow applications to change
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specific socket options. The callback's \fIpurpose\fP argument identifies the
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exact purpose for this particular socket:
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\fICURLSOCKTYPE_IPCXN\fP for actively created connections or since 7.28.0
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\fICURLSOCKTYPE_ACCEPT\fP for FTP when the connection was setup with PORT/EPSV
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(in earlier versions these sockets were not passed to this callback).
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Future versions of libcurl may support more purposes. libcurl passes the newly
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created socket descriptor to the callback in the \fIcurlfd\fP parameter so
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additional setsockopt() calls can be done at the user's discretion.
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The \fIclientp\fP pointer contains whatever user-defined value set using the
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\fICURLOPT_SOCKOPTDATA(3)\fP function.
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Return \fICURL_SOCKOPT_OK\fP from the callback on success. Return
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\fICURL_SOCKOPT_ERROR\fP from the callback function to signal an unrecoverable
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error to the library and it closes the socket and returns
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\fICURLE_COULDNT_CONNECT\fP. Alternatively, the callback function can return
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\fICURL_SOCKOPT_ALREADY_CONNECTED\fP, to tell libcurl that the socket is
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already connected and then libcurl does no attempt to connect. This allows an
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application to pass in an already connected socket with
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\fICURLOPT_OPENSOCKETFUNCTION(3)\fP and then have this function make libcurl
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not attempt to connect (again).
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.SH DEFAULT
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By default, this callback is NULL and unused.
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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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/* make libcurl use the already established socket 'sockfd' */
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static curl_socket_t opensocket(void *clientp,
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curlsocktype purpose,
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struct curl_sockaddr *address)
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{
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curl_socket_t sockfd;
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sockfd = *(curl_socket_t *)clientp;
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/* the actual externally set socket is passed in via the OPENSOCKETDATA
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option */
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return sockfd;
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}
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static int sockopt_callback(void *clientp, curl_socket_t curlfd,
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curlsocktype purpose)
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{
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/* This return code was added in libcurl 7.21.5 */
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return CURL_SOCKOPT_ALREADY_CONNECTED;
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}
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int main(void)
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{
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CURL *curl = curl_easy_init();
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if(curl) {
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CURLcode res;
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int sockfd; /* our custom file descriptor */
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/* libcurl thinks that you connect to the host
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* and port that you specify in the URL option. */
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curl_easy_setopt(curl, CURLOPT_URL, "http://99.99.99.99:9999");
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/* call this function to get a socket */
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curl_easy_setopt(curl, CURLOPT_OPENSOCKETFUNCTION, opensocket);
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curl_easy_setopt(curl, CURLOPT_OPENSOCKETDATA, &sockfd);
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/* call this function to set options for the socket */
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curl_easy_setopt(curl, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
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res = curl_easy_perform(curl);
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curl_easy_cleanup(curl);
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}
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}
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.fi
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.SH AVAILABILITY
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Added in 7.16.0. The \fICURL_SOCKOPT_ALREADY_CONNECTED\fP return code was
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added in 7.21.5.
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.SH RETURN VALUE
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Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
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.SH "SEE ALSO"
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.BR CURLOPT_OPENSOCKETFUNCTION (3),
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.BR CURLOPT_SEEKFUNCTION (3),
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.BR CURLOPT_SOCKOPTDATA (3)
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