129 lines
4.7 KiB
Groff
129 lines
4.7 KiB
Groff
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.\" **************************************************************************
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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_OPENSOCKETFUNCTION 3 "August 22, 2023" "ibcurl 8.3.0" libcurl
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.SH NAME
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CURLOPT_OPENSOCKETFUNCTION \- callback for opening socket
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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;
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struct curl_sockaddr {
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int family;
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int socktype;
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int protocol;
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unsigned int addrlen;
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struct sockaddr addr;
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};
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curl_socket_t opensocket_callback(void *clientp,
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curlsocktype purpose,
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struct curl_sockaddr *address);
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_OPENSOCKETFUNCTION, opensocket_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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This callback function gets called by libcurl instead of the \fIsocket(2)\fP
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call. The callback's \fIpurpose\fP argument identifies the exact purpose for
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this particular socket. \fICURLSOCKTYPE_IPCXN\fP is for IP based connections
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and is the only purpose currently used in libcurl. Future versions of libcurl
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may support more purposes.
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The \fIclientp\fP pointer contains whatever user-defined value set using the
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\fICURLOPT_OPENSOCKETDATA(3)\fP function.
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The callback gets the resolved peer address as the \fIaddress\fP argument and
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is allowed to modify the address or refuse to connect completely. The callback
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function should return the newly created socket or \fICURL_SOCKET_BAD\fP in
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case no connection could be established or another error was detected. Any
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additional \fIsetsockopt(2)\fP calls can of course be done on the socket at
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the user's discretion. A \fICURL_SOCKET_BAD\fP return value from the callback
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function signals an unrecoverable error to libcurl and it returns
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\fICURLE_COULDNT_CONNECT\fP from the function that triggered this callback.
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This return code can be used for IP address block listing.
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If you want to pass in a socket with an already established connection, pass
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the socket back with this callback and then use
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\fICURLOPT_SOCKOPTFUNCTION(3)\fP to signal that it already is connected.
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.SH DEFAULT
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The default behavior is the equivalent of this:
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.nf
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return socket(addr->family, addr->socktype, addr->protocol);
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.fi
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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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curl = curl_easy_init();
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if(curl) {
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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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.fi
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.SH AVAILABILITY
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Added in 7.17.1.
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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_OPENSOCKETDATA "(3), " CURLOPT_SOCKOPTFUNCTION "(3), "
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.BR CURLOPT_CLOSESOCKETFUNCTION "(3), "
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