man pages section 3: Library Interfaces and Headers

CURLOPT_OPENSOCKETFUNCTION (3)

Name

CURLOPT_OPENSOCKETFUNCTION - callback for opening socket

Synopsis

#include <curl/curl.h>

typedef enum  {
CURLSOCKTYPE_IPCXN,  /* socket created for a specific IP connection */
} curlsocktype;

struct curl_sockaddr {
int family;
int socktype;
int protocol;
unsigned int addrlen;
struct sockaddr addr;
};

curl_socket_t opensocket_callback(void *clientp,
curlsocktype purpose,
struct curl_sockaddr *address);

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_OPENSOCKETFUNCTION, opensocket_callback);

Description

curl_easy_setopt options                         CURLOPT_OPENSOCKETFUNCTION(3)



NAME
       CURLOPT_OPENSOCKETFUNCTION - callback for opening socket

SYNOPSIS
       #include <curl/curl.h>

       typedef enum  {
         CURLSOCKTYPE_IPCXN,  /* socket created for a specific IP connection */
       } curlsocktype;

       struct curl_sockaddr {
         int family;
         int socktype;
         int protocol;
         unsigned int addrlen;
         struct sockaddr addr;
       };

       curl_socket_t opensocket_callback(void *clientp,
                                         curlsocktype purpose,
                                         struct curl_sockaddr *address);

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_OPENSOCKETFUNCTION, opensocket_callback);

DESCRIPTION
       Pass a pointer to your callback function, which should match the proto-
       type shown above.

       This callback function gets called by libcurl instead of the  socket(2)
       call.  The callback's purpose argument identifies the exact purpose for
       this particular socket. CURLSOCKTYPE_IPCXN is for IP based  connections
       and  is  the only purpose currently used in libcurl. Future versions of
       libcurl may support more purposes.

       The clientp pointer contains whatever user-defined value set using  the
       CURLOPT_OPENSOCKETDATA(3) function.

       The callback gets the resolved peer address as the address argument and
       is allowed to modify the address or refuse to connect  completely.  The
       callback   function   should   return   the  newly  created  socket  or
       CURL_SOCKET_BAD in case no connection could be established  or  another
       error was detected. Any additional setsockopt(2) calls can of course be
       done on the socket at the user's discretion.  A CURL_SOCKET_BAD  return
       value  from the callback function will signal an unrecoverable error to
       libcurl and it will return CURLE_COULDNT_CONNECT from the function that
       triggered  this  callback.  This return code can be used for IP address
       block listing.

       If you want to pass in a socket with an already established connection,
       pass  the  socket back with this callback and then use CURLOPT_SOCKOPT-
       FUNCTION(3) to signal that it already is connected.

DEFAULT
       The default behavior is the equivalent of this:
          return socket(addr->family, addr->socktype, addr->protocol);

PROTOCOLS
       All

EXAMPLE
       /* make libcurl use the already established socket 'sockfd' */

       static curl_socket_t opensocket(void *clientp,
                                       curlsocktype purpose,
                                       struct curl_sockaddr *address)
       {
         curl_socket_t sockfd;
         sockfd = *(curl_socket_t *)clientp;
         /* the actual externally set socket is passed in via the OPENSOCKETDATA
            option */
         return sockfd;
       }

       static int sockopt_callback(void *clientp, curl_socket_t curlfd,
                                   curlsocktype purpose)
       {
         /* This return code was added in libcurl 7.21.5 */
         return CURL_SOCKOPT_ALREADY_CONNECTED;
       }

       curl = curl_easy_init();
       if(curl) {
         /* libcurl will internally think that you connect to the host
          * and port that you specify in the URL option. */
         curl_easy_setopt(curl, CURLOPT_URL, "http://99.99.99.99:9999");
         /* call this function to get a socket */
         curl_easy_setopt(curl, CURLOPT_OPENSOCKETFUNCTION, opensocket);
         curl_easy_setopt(curl, CURLOPT_OPENSOCKETDATA, &sockfd);

         /* call this function to set options for the socket */
         curl_easy_setopt(curl, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);

         res = curl_easy_perform(curl);

         curl_easy_cleanup(curl);
       }

AVAILABILITY
       Added in 7.17.1.

RETURN VALUE
       Returns CURLE_OK if the option is supported,  and  CURLE_UNKNOWN_OPTION
       if not.


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+------------------+
       |ATTRIBUTE TYPE | ATTRIBUTE VALUE  |
       +---------------+------------------+
       |Availability   | web/curl         |
       +---------------+------------------+
       |Stability      | Uncommitted      |
       +---------------+------------------+

SEE ALSO
       CURLOPT_OPENSOCKETDATA(3),   CURLOPT_SOCKOPTFUNCTION(3),  CURLOPT_CLOS-
       ESOCKETFUNCTION(3),



NOTES
       Source code for open source software components in Oracle  Solaris  can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-
       code-downloads.html.

       This    software    was    built    from    source     available     at
       https://github.com/oracle/solaris-userland.    The  original  community
       source      was      downloaded       from        https://curl.se/down-
       load/curl-7.83.1.tar.bz2.

       Further information about this software can be found on the open source
       community website at http://curl.haxx.se/.



libcurl 7.83.1                September 08, 2021
                                                 CURLOPT_OPENSOCKETFUNCTION(3)