CURLOPT_PREREQFUNCTION(3) curl_easy_setopt options CURLOPT_PREREQFUNCTION(3)
NAME
CURLOPT_PREREQFUNCTION - user callback called when a connection has
been established, but before a request has been made.
SYNOPSIS
#include <curl/curl.h>
/* These are the return codes for the pre-request callback. */
#define CURL_PREREQFUNC_OK 0
#define CURL_PREREQFUNC_ABORT 1 /* fail the entire transfer */
int prereq_callback(void *clientp,
char *conn_primary_ip,
char *conn_local_ip,
int conn_primary_port,
int conn_local_port);
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PREREQFUNCTION, prereq_callback);
DESCRIPTION
Pass a pointer to your callback function, which should match the proto-
type shown above.
This function gets called by libcurl after a connection has been estab-
lished or a connection has been reused (including any SSL handshaking),
but before any request is actually made on the connection. For example,
for HTTP, this callback is called once a connection has been estab-
lished to the server, but before a GET/HEAD/POST/etc request has been
sent.
This function may be called multiple times if redirections are enabled
and are being followed (see CURLOPT_FOLLOWLOCATION(3)).
This function is passed the following information:
conn_primary_ip
A nul-terminated pointer to a C string containing the primary IP
of the remote server established with this connection. For FTP,
this is the IP for the control connection. IPv6 addresses are
represented without surrounding brackets.
conn_local_ip
A nul-terminated pointer to a C string containing the originat-
ing IP for this connection. IPv6 addresses are represented with-
out surrounding brackets.
conn_primary_port
The primary port number on the remote server established with
this connection. For FTP, this is the port for the control con-
nection. This can be a TCP or a UDP port number dependending on
the protocol.
conn_local_port
The originating port number for this connection. This can be a
TCP or a UDP port number dependending on the protocol.
clientp is the pointer you set with CURLOPT_PREREQDATA(3).
The callback function must return CURL_PREREQFUNC_OK on success, or
CURL_PREREQFUNC_ABORT to cause the transfer to fail.
DEFAULT
By default, this is NULL and unused.
PROTOCOLS
ALL
EXAMPLE
static int prereq_callback(void *clientp,
char *conn_primary_ip,
char *conn_local_ip,
int conn_primary_port,
int conn_local_port)
{
printf("Connection made to %s:%s\n", conn_primary_ip, conn_primary_port);
return CURL_PREREQFUNC_OK;
}
{
struct data prereq_data;
curl_easy_setopt(CURL *handle, CURLOPT_PREREQFUNCTION, prereq_callback);
curl_easy_setopt(CURL *handle, CURLOPT_PREREQDATA, &prereq_data);
}
AVAILABILITY
Added in 7.80.0
RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION
if not.
SEE ALSO
CURLOPT_PREREQDATA(3)
libcurl 7.81.0 November 04, 2021 CURLOPT_PREREQFUNCTION(3)
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