Annotation of embedaddon/curl/docs/libcurl/opts/CURLOPT_OPENSOCKETFUNCTION.3, revision 1.1.1.1
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23: .TH CURLOPT_OPENSOCKETFUNCTION 3 "December 03, 2019" "libcurl 7.70.0" "curl_easy_setopt options"
24:
25: .SH NAME
26: CURLOPT_OPENSOCKETFUNCTION \- set callback for opening sockets
27: .SH SYNOPSIS
28: .nf
29: #include <curl/curl.h>
30:
31: typedef enum {
32: CURLSOCKTYPE_IPCXN, /* socket created for a specific IP connection */
33: } curlsocktype;
34:
35: struct curl_sockaddr {
36: int family;
37: int socktype;
38: int protocol;
39: unsigned int addrlen;
40: struct sockaddr addr;
41: };
42:
43: curl_socket_t opensocket_callback(void *clientp,
44: curlsocktype purpose,
45: struct curl_sockaddr *address);
46:
47: CURLcode curl_easy_setopt(CURL *handle, CURLOPT_OPENSOCKETFUNCTION, opensocket_callback);
48: .SH DESCRIPTION
49: Pass a pointer to your callback function, which should match the prototype
50: shown above.
51:
52: This callback function gets called by libcurl instead of the \fIsocket(2)\fP
53: call. The callback's \fIpurpose\fP argument identifies the exact purpose for
54: this particular socket. \fICURLSOCKTYPE_IPCXN\fP is for IP based connections
55: and is the only purpose currently used in libcurl. Future versions of libcurl
56: may support more purposes.
57:
58: The \fIclientp\fP pointer contains whatever user-defined value set using the
59: \fICURLOPT_OPENSOCKETDATA(3)\fP function.
60:
61: The callback gets the resolved peer address as the \fIaddress\fP argument and
62: is allowed to modify the address or refuse to connect completely. The callback
63: function should return the newly created socket or \fICURL_SOCKET_BAD\fP in
64: case no connection could be established or another error was detected. Any
65: additional \fIsetsockopt(2)\fP calls can of course be done on the socket at
66: the user's discretion. A \fICURL_SOCKET_BAD\fP return value from the callback
67: function will signal an unrecoverable error to libcurl and it will return
68: \fICURLE_COULDNT_CONNECT\fP from the function that triggered this callback.
69: This return code can be used for IP address blacklisting.
70:
71: If you want to pass in a socket with an already established connection, pass
72: the socket back with this callback and then use
73: \fICURLOPT_SOCKOPTFUNCTION(3)\fP to signal that it already is connected.
74: .SH DEFAULT
75: The default behavior is the equivalent of this:
76: .nf
77: return socket(addr->family, addr->socktype, addr->protocol);
78: .fi
79: .SH PROTOCOLS
80: All
81: .SH EXAMPLE
82: .nf
83: /* make libcurl use the already established socket 'sockfd' */
84:
85: static curl_socket_t opensocket(void *clientp,
86: curlsocktype purpose,
87: struct curl_sockaddr *address)
88: {
89: curl_socket_t sockfd;
90: sockfd = *(curl_socket_t *)clientp;
91: /* the actual externally set socket is passed in via the OPENSOCKETDATA
92: option */
93: return sockfd;
94: }
95:
96: static int sockopt_callback(void *clientp, curl_socket_t curlfd,
97: curlsocktype purpose)
98: {
99: /* This return code was added in libcurl 7.21.5 */
100: return CURL_SOCKOPT_ALREADY_CONNECTED;
101: }
102:
103: curl = curl_easy_init();
104: if(curl) {
105: /* libcurl will internally think that you connect to the host
106: * and port that you specify in the URL option. */
107: curl_easy_setopt(curl, CURLOPT_URL, "http://99.99.99.99:9999");
108: /* call this function to get a socket */
109: curl_easy_setopt(curl, CURLOPT_OPENSOCKETFUNCTION, opensocket);
110: curl_easy_setopt(curl, CURLOPT_OPENSOCKETDATA, &sockfd);
111:
112: /* call this function to set options for the socket */
113: curl_easy_setopt(curl, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
114:
115: res = curl_easy_perform(curl);
116:
117: curl_easy_cleanup(curl);
118: }
119: .fi
120: .SH AVAILABILITY
121: Added in 7.17.1.
122: .SH RETURN VALUE
123: Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
124: .SH "SEE ALSO"
125: .BR CURLOPT_OPENSOCKETDATA "(3), " CURLOPT_SOCKOPTFUNCTION "(3), "
126: .BR CURLOPT_CLOSESOCKETFUNCTION "(3), "
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