include/types/connection.h

/*
 * include/types/connection.h
 * This file describes the connection struct and associated constants.
 *
 * Copyright (C) 2000-2012 Willy Tarreau - w@1wt.eu
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation, version 2.1
 * exclusively.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

#ifndef _TYPES_CONNECTION_H
#define _TYPES_CONNECTION_H

#include <stdlib.h>
#include <sys/socket.h>

#include <common/config.h>

/* referenced below */
struct protocol;
struct connection;
struct buffer;
struct pipe;
struct server;
struct proxy;
struct si_applet;
struct task;
struct listener;

/* Polling flags that are manipulated by I/O callbacks and handshake callbacks
 * indicate what they expect from a file descriptor at each layer. For each
 * direction, we have 2 bits, one stating whether any suspected activity on the
 * FD induce a call to the iocb, and another one indicating that the FD has
 * already returned EAGAIN and that polling on it is essential before calling
 * the iocb again :
 *   POL ENA  state
 *    0   0   STOPPED : any activity on this FD is ignored
 *    0   1   ENABLED : any (suspected) activity may call the iocb
 *    1   0   STOPPED : as above
 *    1   1   POLLED  : the FD is being polled for activity
 *
 * - Enabling an I/O event consists in ORing with 1.
 * - Stopping an I/O event consists in ANDing with ~1.
 * - Polling for an I/O event consists in ORing with ~3.
 *
 * The last computed state is remembered in CO_FL_CURR_* so that differential
 * changes can be applied. After bits are applied, the POLL status bits are
 * cleared so that it is possible to detect when an EAGAIN was encountered. For
 * pollers that do not support speculative I/O, POLLED is the same as ENABLED
 * and the POL flag can safely be ignored. However it makes a difference for
 * the connection handler.
 *
 * The ENA flags are per-layer (one pair for SOCK, another one for DATA).
 * The POL flags are only for the socket layer since they indicate that EAGAIN
 * was encountered. Thus, the DATA layer uses its own ENA flag and the socket
 * layer's POL flag.
 */

/* flags for use in connection->flags */
enum {
	CO_FL_NONE          = 0x00000000,
	CO_FL_ERROR         = 0x00000001,  /* a fatal error was reported     */
	CO_FL_CONNECTED     = 0x00000002,  /* the connection is now established */
	CO_FL_WAIT_L4_CONN  = 0x00000004,  /* waiting for L4 to be connected */
	CO_FL_WAIT_L6_CONN  = 0x00000008,  /* waiting for L6 to be connected (eg: SSL) */

	CO_FL_NOTIFY_SI     = 0x00000010,  /* notify stream interface about changes */

	/* flags below are used for connection handshakes */
	CO_FL_SI_SEND_PROXY = 0x00000020,  /* send a valid PROXY protocol header */
	CO_FL_ACCEPT_PROXY  = 0x00000080,  /* send a valid PROXY protocol header */

	/* below we have all handshake flags grouped into one */
	CO_FL_HANDSHAKE     = CO_FL_SI_SEND_PROXY | CO_FL_ACCEPT_PROXY,

	CO_FL_INIT_SESS     = 0x00000800,  /* initialize a session before using data */

	/* when any of these flags is set, polling is defined by socket-layer
	 * operations, as opposed to data-layer.
	 */
	CO_FL_POLL_SOCK     = CO_FL_HANDSHAKE | CO_FL_WAIT_L4_CONN | CO_FL_WAIT_L6_CONN,

	/* These flags are used to report whether the from/to addresses are set or not */
	CO_FL_ADDR_FROM_SET = 0x00004000,  /* addr.from is set */
	CO_FL_ADDR_TO_SET   = 0x00008000,  /* addr.to is set */

	/* flags used to remember what shutdown have been performed/reported */
	CO_FL_DATA_RD_SH    = 0x00010000,  /* DATA layer was notified about shutr/read0 */
	CO_FL_DATA_WR_SH    = 0x00020000,  /* DATA layer asked for shutw */
	CO_FL_SOCK_RD_SH    = 0x00040000,  /* SOCK layer was notified about shutr/read0 */
	CO_FL_SOCK_WR_SH    = 0x00080000,  /* SOCK layer asked for shutw */

	/* NOTE: do not change the values of any of the flags below, they're
	 * used with masks and bit shifts to quickly detect multiple changes.
	 */

	/* These flags are used by data layers to indicate to indicate they had
	 * to stop sending data because a buffer was empty (WAIT_DATA) or stop
	 * receiving data because a buffer was full (WAIT_ROOM). The connection
	 * handler clears them before first calling the I/O and data callbacks.
	 */
	CO_FL_WAIT_DATA     = 0x00100000,  /* data source is empty */
	CO_FL_WAIT_ROOM     = 0x00200000,  /* data sink is full */

	/* These flags are used by both socket-level and data-level callbacks
	 * to indicate that they had to stop receiving or sending because a
	 * socket-level operation returned EAGAIN. While setting these flags
	 * is not always absolutely mandatory (eg: when a reader estimates that
	 * trying again soon without polling is OK), it is however forbidden to
	 * set them without really attempting the I/O operation.
	 */
	CO_FL_WAIT_RD       = 0x00400000,  /* receiving needs to poll first */
	CO_FL_WAIT_WR       = 0x00800000,  /* sending needs to poll first */

	/* flags describing the DATA layer expectations regarding polling */
	CO_FL_DATA_RD_ENA   = 0x01000000,  /* receiving is allowed */
	CO_FL_DATA_WR_ENA   = 0x02000000,  /* sending is desired */

	/* flags describing the SOCK layer expectations regarding polling */
	CO_FL_SOCK_RD_ENA   = 0x04000000,  /* receiving is allowed */
	CO_FL_SOCK_WR_ENA   = 0x08000000,  /* sending is desired */

	/* flags storing the current polling state */
	CO_FL_CURR_RD_ENA   = 0x10000000,  /* receiving is allowed */
	CO_FL_CURR_WR_ENA   = 0x20000000,  /* sending is desired */
	CO_FL_CURR_RD_POL   = 0x40000000,  /* receiving needs to poll first */
	CO_FL_CURR_WR_POL   = 0x80000000,  /* sending needs to poll first */
};

/* target types */
enum {
	TARG_TYPE_NONE = 0,         /* no target set, pointer is NULL by definition */
	TARG_TYPE_CLIENT,           /* target is a client, pointer is NULL by definition */
	TARG_TYPE_PROXY,            /* target is a proxy   ; use address with the proxy's settings */
	TARG_TYPE_SERVER,           /* target is a server  ; use address with server's and its proxy's settings */
	TARG_TYPE_APPLET,           /* target is an applet ; use only the applet */
	TARG_TYPE_TASK,             /* target is a task running an external applet */
};


/* data_ops describes data-layer operations for a connection. They generally
 * run over a socket-based control layer, but not always.
 */
struct data_ops {
	int  (*rcv_buf)(struct connection *conn, struct buffer *buf, int count); /* recv callback */
	int  (*snd_buf)(struct connection *conn, struct buffer *buf, int flags); /* send callback */
	int  (*rcv_pipe)(struct connection *conn, struct pipe *pipe, unsigned int count); /* recv-to-pipe callback */
	int  (*snd_pipe)(struct connection *conn, struct pipe *pipe); /* send-to-pipe callback */
	void (*shutr)(struct connection *, int);    /* shutr function */
	void (*shutw)(struct connection *, int);    /* shutw function */
	void (*close)(struct connection *);         /* close the data channel on the connection */
	int  (*init)(struct connection *conn);      /* initialize the data layer */
};

/* app_cb describes read and write callbacks which are called upon detected I/O
 * activity at the data layer. These callbacks are supposed to make use of the
 * data_ops above to exchange data from/to buffers and pipes.
 */
struct app_cb {
	void (*recv)(struct connection *conn);  /* application-layer recv callback */
	void (*send)(struct connection *conn);  /* application-layer send callback */
};

/* a target describes what is on the remote side of the connection. */
struct target {
	int type;
	union {
		void *v;              /* pointer value, for any type */
		struct proxy *p;      /* when type is TARG_TYPE_PROXY  */
		struct server *s;     /* when type is TARG_TYPE_SERVER */
		struct si_applet *a;  /* when type is TARG_TYPE_APPLET */
		struct task *t;       /* when type is TARG_TYPE_TASK */
		struct listener *l;   /* when type is TARG_TYPE_CLIENT */
	} ptr;
};

/* This structure describes a connection with its methods and data.
 * A connection may be performed to proxy or server via a local or remote
 * socket, and can also be made to an internal applet. It can support
 * several data schemes (applet, raw, ssl, ...). It can support several
 * connection control schemes, generally a protocol for socket-oriented
 * connections, but other methods for applets.
 */
struct connection {
	const struct data_ops *data;  /* operations at the data layer */
	const struct protocol *ctrl;  /* operations at the socket layer */
	const struct app_cb *app_cb;  /* application layer callbacks */
	union {                       /* definitions which depend on connection type */
		struct {              /*** information used by socket-based connections ***/
			int fd;       /* file descriptor for a stream driver when known */
		} sock;
	} t;
	unsigned int flags;           /* CO_F_* */
	int data_st;                  /* data layer state, initialized to zero */
	void *data_ctx;               /* general purpose pointer, initialized to NULL */
	struct target target;         /* the target to connect to (server, proxy, applet, ...) */
	struct {
		struct sockaddr_storage from;	/* client address, or address to spoof when connecting to the server */
		struct sockaddr_storage to;	/* address reached by the client if SN_FRT_ADDR_SET is set, or address to connect to */
	} addr; /* addresses of the remote side, client for producer and server for consumer */
};

#endif /* _TYPES_CONNECTION_H */

/*
 * Local variables:
 *  c-indent-level: 8
 *  c-basic-offset: 8
 * End:
 */