/*++
 * NAME
 *	auto_clnt 3
 * SUMMARY
 *	client endpoint maintenance
 * SYNOPSIS
 *	#include <auto_clnt.h>
 *
 *	AUTO_CLNT *auto_clnt_create(service, timeout, max_idle, max_ttl)
 *	const char *service;
 *	int	timeout;
 *	int	max_idle;
 *	int	max_ttl;
 *
 *	ACL_VSTREAM	*auto_clnt_access(auto_clnt)
 *	AUTO_CLNT *auto_clnt;
 *
 *	void	auto_clnt_recover(auto_clnt)
 *	AUTO_CLNT *auto_clnt;
 *
 *	const char *auto_clnt_name(auto_clnt)
 *	AUTO_CLNT *auto_clnt;
 *
 *	void	auto_clnt_free(auto_clnt)
 *	AUTO_CLNT *auto_clnt;
 * DESCRIPTION
 *	This module maintains IPC client endpoints that automatically
 *	disconnect after a being idle for a configurable amount of time,
 *	that disconnect after a configurable time to live,
 *	and that transparently handle most server-initiated disconnects.
 *
 *	This module tries each operation only a limited number of
 *	times and then reports an error.  This is unlike the
 *	clnt_stream(3) module which will retry forever, so that
 *	the application never experiences an error.
 *
 *	auto_clnt_create() instantiates a client endpoint.
 *
 *	auto_clnt_access() returns an open stream to the service specified
 *	to auto_clnt_create(). The stream instance may change between calls.
 *	The result is a null pointer in case of failure.
 *
 *	auto_clnt_recover() recovers from a server-initiated disconnect
 *	that happened in the middle of an I/O operation.
 *
 *	auto_clnt_name() returns the name of the specified client endpoint.
 *
 *	auto_clnt_free() destroys of the specified client endpoint.
 *
 *	Arguments:
 * .IP service
 *	The service argument specifies "transport:servername" where
 *	transport is currently limited to one of the following:
 * .RS
 * .IP inet
 *	servername has the form "inet:host:port".
 * .IP local
 *	servername has the form "local:private/servicename" or
 *	"local:public/servicename". This is the preferred way to
 *	specify Postfix daemons that are configured as "unix" in
 *	master.cf.
 * .IP unix
 *	servername has the form "unix:private/servicename" or
 *	"unix:public/servicename". This does not work on Solaris,
 *	where Postfix uses STREAMS instead of UNIX-domain sockets.
 * .RE
 * .IP timeout
 *	The time limit for sending, receiving, or for connecting
 *	to a server. Specify a value <=0 to disable the time limit.
 * .IP max_idle
 *	Idle time after which the client disconnects. Specify 0 to
 *	disable the limit.
 * .IP max_ttl
 *	Upper bound on the time that a connection is allowed to persist.
 *	Specify 0 to disable the limit.
 * .IP open_action
 *	Application call-back routine that opens a stream or returns a
 *	null pointer upon failure. In case of success, the call-back routine
 *	is expected to set the stream pathname to the server endpoint name.
 * .IP context
 *	Application context that is passed to the open_action routine.
 * DIAGNOSTICS
 *	Warnings: communication failure. Fatal error: out of memory.
 * LICENSE
 * .ad
 * .fi
 *	The Secure Mailer license must be distributed with this software.
 * AUTHOR(S)
 *	Wietse Venema
 *	IBM T.J. Watson Research
 *	P.O. Box 704
 *	Yorktown Heights, NY 10598, USA
 *--*/

#include "StdAfx.h"
#include <string.h>

#include "auto_clnt.h"

/* Application-specific. */

 /*
  * AUTO_CLNT is an opaque structure. None of the access methods can easily
  * be implemented as a macro, and access is not performance critical anyway.
  */
struct AUTO_CLNT {
    ACL_EVENT *event;			/* event handle */
    ACL_VSTREAM *vstream;		/* buffered I/O */
    char   *endpoint;			/* host:port or pathname */
    int     timeout;			/* I/O time limit */
    int     max_idle;			/* time before client disconnect */
    int     max_ttl;			/* time before client disconnect */
    ACL_SOCKET     (*connect) (const char *, int, int);	/* unix, local, inet */
};

static void auto_clnt_close(AUTO_CLNT *);

/* auto_clnt_event - server-initiated disconnect or client-side max_idle */

static void auto_clnt_event(int event_type acl_unused,
	ACL_EVENT *event acl_unused, void *context)
{
    AUTO_CLNT *auto_clnt = (AUTO_CLNT *) context;

    /*
     * Sanity check. This routine causes the stream to be closed, so it
     * cannot be called when the stream is already closed.
     */
    if (auto_clnt->vstream == 0)
	acl_msg_panic("auto_clnt_event: stream is closed");

    auto_clnt_close(auto_clnt);
}

static void auto_clnt_event_read(int event_type, ACL_EVENT *event,
	ACL_VSTREAM *stream acl_unused, void *context)
{
	auto_clnt_event(event_type, event, context);
}

/* auto_clnt_ttl_event - client-side expiration */

static void auto_clnt_ttl_event(int event_type, ACL_EVENT *event, void *context)
{

    /*
     * XXX This function is needed only because event_request_timer() cannot
     * distinguish between requests that specify the same call-back routine
     * and call-back context. The fix is obvious: specify a request ID along
     * with the call-back routine, but there is too much code that would have
     * to be changed.
     * 
     * XXX Should we be concerned that an overly agressive optimizer will
     * eliminate this function and replace calls to auto_clnt_ttl_event() by
     * direct calls to auto_clnt_event()? It should not, because there exists
     * code that takes the address of both functions.
     */
    auto_clnt_event(event_type, event, context);
}

/* auto_clnt_open - connect to service */

static void auto_clnt_open(AUTO_CLNT *auto_clnt)
{
    const char *myname = "auto_clnt_open";
    ACL_SOCKET     fd;

    /*
     * Sanity check.
     */
    if (auto_clnt->vstream)
	acl_msg_panic("auto_clnt_open: stream is open");

    /*
     * Schedule a read event so that we can clean up when the remote side
     * disconnects, and schedule a timer event so that we can cleanup an idle
     * connection. Note that both events are handled by the same routine.
     * 
     * Finally, schedule an event to force disconnection even when the
     * connection is not idle. This is to prevent one client from clinging on
     * to a server forever.
     */
    fd = auto_clnt->connect(auto_clnt->endpoint, ACL_BLOCKING, auto_clnt->timeout);
    if (fd < 0) {
	acl_msg_warn("%s: connect to %s: %s", myname, auto_clnt->endpoint, acl_last_serror());
    } else {
	if (acl_msg_verbose)
	    acl_msg_info("%s: connected to %s", myname, auto_clnt->endpoint);
	auto_clnt->vstream = acl_vstream_fdopen(fd, O_RDWR, 4096,
			auto_clnt->timeout, ACL_VSTREAM_TYPE_SOCK);
	acl_vstream_ctl(auto_clnt->vstream,
			ACL_VSTREAM_CTL_PATH, auto_clnt->endpoint,
			/* ACL_VSTREAM_CTL_TIMEOUT, auto_clnt->timeout, */
			ACL_VSTREAM_CTL_END);
    }

    if (auto_clnt->vstream != 0) {
#ifdef	ACL_UNIX
	acl_close_on_exec(ACL_VSTREAM_SOCK(auto_clnt->vstream), ACL_CLOSE_ON_EXEC);
#endif
	acl_event_enable_read(auto_clnt->event, auto_clnt->vstream, 0,
		auto_clnt_event_read, (char *) auto_clnt);
	if (auto_clnt->max_idle > 0)
	    acl_event_request_timer(auto_clnt->event, auto_clnt_event,
		    (char *) auto_clnt, auto_clnt->max_idle, 0);
	if (auto_clnt->max_ttl > 0)
	    acl_event_request_timer(auto_clnt->event, auto_clnt_ttl_event,
		    (char *) auto_clnt, auto_clnt->max_ttl, 0);
    }
}

/* auto_clnt_close - disconnect from service */

static void auto_clnt_close(AUTO_CLNT *auto_clnt)
{
    const char *myname = "auto_clnt_close";

    /*
     * Sanity check.
     */
    if (auto_clnt->vstream == 0)
	acl_msg_panic("%s: stream is closed", myname);

    /*
     * Be sure to disable read and timer events.
     */
    if (acl_msg_verbose)
	acl_msg_info("%s: disconnect %s stream",
		 myname, ACL_VSTREAM_PATH(auto_clnt->vstream));
    acl_event_disable_readwrite(auto_clnt->event, auto_clnt->vstream);
    acl_event_cancel_timer(auto_clnt->event, auto_clnt_event, (char *) auto_clnt);
    acl_event_cancel_timer(auto_clnt->event, auto_clnt_ttl_event, (char *) auto_clnt);
    (void) acl_vstream_fclose(auto_clnt->vstream);
    auto_clnt->vstream = 0;
}

/* auto_clnt_recover - recover from server-initiated disconnect */

void    auto_clnt_recover(AUTO_CLNT *auto_clnt)
{
    /*
     * Clean up. Don't re-connect until the caller needs it.
     */
    if (auto_clnt->vstream)
	auto_clnt_close(auto_clnt);
}

/* auto_clnt_access - access a client stream */

ACL_VSTREAM *auto_clnt_access(AUTO_CLNT *auto_clnt)
{
    /*
     * Open a stream or restart the idle timer.
     * 
     * Important! Do not restart the TTL timer!
     */
    if (auto_clnt->vstream == 0) {
	auto_clnt_open(auto_clnt);
    } else if (auto_clnt->max_idle > 0) {
	acl_event_request_timer(auto_clnt->event, auto_clnt_event,
		(char *) auto_clnt, auto_clnt->max_idle, 0);
    }
    return (auto_clnt->vstream);
}

/* auto_clnt_create - create client stream object */

AUTO_CLNT *auto_clnt_create(ACL_EVENT *eventp, const char *service,
	int timeout, int max_idle, int max_ttl)
{
    const char *myname = "auto_clnt_create";
    char   *transport = acl_mystrdup(service);
    char   *endpoint;
    AUTO_CLNT *auto_clnt;

    if (eventp == 0)
	acl_msg_fatal("%s(%d): evenpt null", myname, __LINE__);

    /*
     * Don't open the stream until the caller needs it.
     */
    if ((endpoint = acl_split_at(transport, ':')) == 0
	|| *endpoint == 0 || *transport == 0)
	acl_msg_fatal("%s: need service transport:endpoint instead of \"%s\"",
		myname, service);
    if (acl_msg_verbose)
	acl_msg_info("%s: transport=%s endpoint=%s", myname, transport, endpoint);
    auto_clnt = (AUTO_CLNT *) acl_mymalloc(sizeof(*auto_clnt));
    auto_clnt->event = eventp;
    auto_clnt->vstream = 0;
    auto_clnt->endpoint = acl_mystrdup(endpoint);
    auto_clnt->timeout = timeout;
    auto_clnt->max_idle = max_idle;
    auto_clnt->max_ttl = max_ttl;
    if (strcmp(transport, "inet") == 0) {
	auto_clnt->connect = acl_inet_connect;
    }
#ifdef	ACL_UNIX
	else if (strcmp(transport, "local") == 0) {
	auto_clnt->connect = LOCAL_CONNECT;
    } else if (strcmp(transport, "unix") == 0) {
	auto_clnt->connect = acl_unix_connect;
    }
#endif
	else {
	acl_msg_fatal("%s: invalid transport name: %s in service: %s",
		  myname, transport, service);
    }
    acl_myfree(transport);
    return (auto_clnt);
}

/* auto_clnt_name - return client stream name */

const char *auto_clnt_name(AUTO_CLNT *auto_clnt)
{
    return (auto_clnt->endpoint);
}

/* auto_clnt_free - destroy client stream instance */

void    auto_clnt_free(AUTO_CLNT *auto_clnt)
{
    if (auto_clnt->vstream)
	auto_clnt_close(auto_clnt);
    acl_myfree(auto_clnt->endpoint);
    acl_myfree(auto_clnt);
}