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e3fe020089
Remove the PROTOCOLS section from the source files completely and instead generate them based on the header data in the curldown files. It also generates TLS backend information for options marked for TLS as protocol. Closes #13175
130 lines
3.8 KiB
Markdown
130 lines
3.8 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_OPENSOCKETFUNCTION
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Section: 3
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Source: libcurl
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See-also:
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- CURLOPT_CLOSESOCKETFUNCTION (3)
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- CURLOPT_OPENSOCKETFUNCTION (3)
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- CURLOPT_SOCKOPTFUNCTION (3)
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Protocol:
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- All
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---
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# NAME
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CURLOPT_OPENSOCKETFUNCTION - callback for opening socket
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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;
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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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~~~
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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 callback function gets called by libcurl instead of the *socket(2)*
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call. The callback's *purpose* argument identifies the exact purpose for
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this particular socket. *CURLSOCKTYPE_IPCXN* 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 *clientp* pointer contains whatever user-defined value set using the
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CURLOPT_OPENSOCKETDATA(3) function.
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The callback gets the resolved peer address as the *address* 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 *CURL_SOCKET_BAD* in
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case no connection could be established or another error was detected. Any
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additional *setsockopt(2)* calls can of course be done on the socket at
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the user's discretion. A *CURL_SOCKET_BAD* return value from the callback
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function signals an unrecoverable error to libcurl and it returns
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*CURLE_COULDNT_CONNECT* 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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CURLOPT_SOCKOPTFUNCTION(3) to signal that it already is connected.
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# DEFAULT
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The default behavior is the equivalent of this:
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~~~c
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return socket(addr->family, addr->socktype, addr->protocol);
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~~~
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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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extern int sockfd; /* the already connected one */
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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 7.17.1.
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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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