133 lines
4 KiB
Markdown
133 lines
4 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_SOCKOPTFUNCTION
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Section: 3
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Source: libcurl
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See-also:
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- CURLOPT_OPENSOCKETFUNCTION (3)
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- CURLOPT_SEEKFUNCTION (3)
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- CURLOPT_SOCKOPTDATA (3)
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---
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# NAME
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CURLOPT_SOCKOPTFUNCTION - callback for setting socket options
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# SYNOPSIS
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~~~c
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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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~~~
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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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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 *purpose* argument identifies the
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exact purpose for this particular socket:
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*CURLSOCKTYPE_IPCXN* for actively created connections or since 7.28.0
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*CURLSOCKTYPE_ACCEPT* 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 *curlfd* parameter so
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additional setsockopt() calls can be done at the user's discretion.
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The *clientp* pointer contains whatever user-defined value set using the
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CURLOPT_SOCKOPTDATA(3) function.
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Return *CURL_SOCKOPT_OK* from the callback on success. Return
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*CURL_SOCKOPT_ERROR* 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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*CURLE_COULDNT_CONNECT*. Alternatively, the callback function can return
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*CURL_SOCKOPT_ALREADY_CONNECTED*, 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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CURLOPT_OPENSOCKETFUNCTION(3) and then have this function make libcurl
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not attempt to connect (again).
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# DEFAULT
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By default, this callback 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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/* 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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~~~
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# AVAILABILITY
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Added in 7.16.0. The *CURL_SOCKOPT_ALREADY_CONNECTED* return code was
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added in 7.21.5.
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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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