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/**
@file rexmpp_tcp.h
@brief TCP connection establishment.
@author defanor <defanor@uberspace.net>
@date 2020
@copyright MIT license.
This module tries to establish a TCP connection to a given host
and port.
A connection establishment procedure begins with
::rexmpp_tcp_conn_init, followed by repeated calls to
::rexmpp_tcp_conn_proceed while the return code is
::REXMPP_CONN_IN_PROGRESS, at the times suggested by
::rexmpp_tcp_conn_timeout and on events suggested by
::rexmpp_tcp_conn_fds, and ends with ::rexmpp_tcp_conn_finish.
*/
#ifndef REXMPP_TCP_H
#define REXMPP_TCP_H
#include <sys/time.h>
#include "rexmpp.h"
#include "rexmpp_dns.h"
#define REXMPP_TCP_MAX_CONNECTION_ATTEMPTS 20
#define REXMPP_TCP_IPV6_DELAY_MS 50
#define REXMPP_TCP_CONN_DELAY_MS 250
/**
@brief Resolution status.
*/
enum rexmpp_tcp_conn_resolution_status {
/** The resolution is not active. */
REXMPP_CONN_RESOLUTION_INACTIVE,
/** Waiting for resolution. */
REXMPP_CONN_RESOLUTION_WAITING,
/** Resolved successfully. */
REXMPP_CONN_RESOLUTION_SUCCESS,
/** Failed to resolve. */
REXMPP_CONN_RESOLUTION_FAILURE
};
typedef enum rexmpp_tcp_conn_resolution_status
rexmpp_tcp_conn_resolution_status_t;
/**
@brief Connection errors.
*/
enum rexmpp_tcp_conn_error {
/** Connected, no error. */
REXMPP_CONN_DONE,
/** Resolver error occurred. The exact error code can be read from
the connection structure. */
REXMPP_CONN_RESOLVER_ERROR,
/** Connection in progress, no error yet. */
REXMPP_CONN_IN_PROGRESS,
/** All the connection attempts failed. */
REXMPP_CONN_FAILURE,
/** An unexpected error during connection. */
REXMPP_CONN_ERROR
};
typedef enum rexmpp_tcp_conn_error rexmpp_tcp_conn_error_t;
typedef struct rexmpp_tcp_connection rexmpp_tcp_conn_t;
/** @brief A connection establishment structure. */
struct rexmpp_tcp_connection {
/** @brief A host we are connecting to. */
const char *host;
/** @brief A port we are connecting to. */
uint16_t port;
/** @brief State of A record resolution. */
enum rexmpp_tcp_conn_resolution_status resolution_v4;
/** @brief Status of A record resolution, as returned by the
resolver. */
int resolver_status_v4;
/** @brief Resolved A records. */
rexmpp_dns_result_t *resolved_v4;
/** @brief The AF_INET address number we are currently at. */
int addr_cur_v4;
/** @brief State of AAAA record resolution. */
enum rexmpp_tcp_conn_resolution_status resolution_v6;
/** @brief Status of AAAA record resolution, as returned by the
resolver. */
int resolver_status_v6;
/** @brief Resolved AAAA records. */
rexmpp_dns_result_t *resolved_v6;
/** @brief The AF_INET6 address number we are currently at. */
int addr_cur_v6;
/** @brief Socket array, one for each connection attempt. */
int sockets[REXMPP_TCP_MAX_CONNECTION_ATTEMPTS];
/** @brief The number of connection attempts so far. */
int connection_attempts;
/** @brief Next scheduled connection time. */
struct timeval next_connection_time;
/** @brief File descriptor of a connected socket. */
int fd;
/** @brief Whether the A or AAAA records used to establish the final
connection were verified with DNSSEC. */
int dns_secure;
};
/**
@brief Initiates a connection.
@param[in] s ::rexmpp
@param[out] conn An allocated connection structure.
@param[in] host A host to connect to. This could be a domain name,
or a textual representation of an IPv4 or an IPv6 address.
@param[in] port A port to connect to.
@returns A ::rexmpp_tcp_conn_error state.
*/
rexmpp_tcp_conn_error_t
rexmpp_tcp_conn_init (rexmpp_t *s,
rexmpp_tcp_conn_t *conn,
const char *host,
uint16_t port);
/**
@brief Continues a connection process.
@param[in] s ::rexmpp
@param[in,out] conn An active connection structure.
@param[in] read_fds File descriptors available for reading from.
@param[in] write_fds File descriptors available for writing to.
@returns A ::rexmpp_tcp_conn_error state.
*/
rexmpp_tcp_conn_error_t
rexmpp_tcp_conn_proceed (rexmpp_t *s,
rexmpp_tcp_conn_t *conn,
fd_set *read_fds,
fd_set *write_fds);
/**
@brief Finalises a connection process.
Closes pending connections except for the established one, frees
additionally allocated resources.
Normally must be called on any state other than
::REXMPP_CONN_IN_PROGRESS. The connection structure can be freed
after this.
@param[in,out] conn An active connection structure.
@returns A connected socket's file descriptor, or -1.
*/
int rexmpp_tcp_conn_finish (rexmpp_tcp_conn_t *conn);
/**
@brief Reports file descriptors a connection process is interested in.
File descriptors are only added to an @c fd_set, so the ones it
already contains will not be lost.
@param[in] s ::rexmpp
@param[in] conn An active connection structure.
@param[out] read_fds File descriptors a connection process is
interested in reading from.
@param[out] write_fds File descriptors a connection process is
interested in writing to.
@returns Maximum file descriptor number, plus 1.
*/
int rexmpp_tcp_conn_fds (rexmpp_t *s,
rexmpp_tcp_conn_t *conn,
fd_set *read_fds,
fd_set *write_fds);
/**
@brief Reports timeouts.
@param[in] s ::rexmpp
@param[in] conn An active connection structure.
@param[in] max_tv An existing maximum timeout.
@param[out] tv A timeval structure to store a new timeout in.
@returns A pointer to either max_tv or tv, depending on which one
is smaller.
*/
struct timeval *rexmpp_tcp_conn_timeout (rexmpp_t *s,
rexmpp_tcp_conn_t *conn,
struct timeval *max_tv,
struct timeval *tv);
#endif
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