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.\" * Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al.
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.TH CURLOPT_OPENSOCKETFUNCTION 3 "16 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options"
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CURLOPT_OPENSOCKETFUNCTION \- set callback for opening sockets
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#include <curl/curl.h>
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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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struct curl_sockaddr {
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curl_socket_t opensocket_callback(void *clientp,
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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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Pass a pointer to your callback function, which should match the prototype
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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 \fICURLSOCKTYPE_ACCEPT\fP is for sockets created after accept() - such as
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when doing active FTP. Future versions of libcurl may support more
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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 will signal an unrecoverable error to libcurl and it will return
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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 blacklisting.
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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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The default behavior is the equivalent of this:
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return socket(addr->family, addr->socktype, addr->protocol);
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Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
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.BR CURLOPT_OPENSOCKETDATA "(3), " CURLOPT_SOCKOPTFUNCTION "(3), "
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.BR CURLOPT_CLOSESOCKETFUNCTION "(3), "
added
removed
docs/libcurl/opts/CURLOPT_OPENSOCKETFUNCTION.3
