/* timer event handling
 * Copyright (C) 1997 Angelos D. Keromytis.
 * Copyright (C) 1998-2001  D. Hugh Redelmeier.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * This program 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 General Public License
 * for more details.
 *
 * RCSID $Id: timer.c 3252 2007-10-06 21:24:50Z andreas $
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/queue.h>

#include <freeswan.h>

#include "constants.h"
#include "defs.h"
#include "connections.h"
#include "state.h"
#include "demux.h"
#include "ipsec_doi.h"	/* needs demux.h and state.h */
#include "kernel.h"
#include "server.h"
#include "log.h"
#include "rnd.h"
#include "timer.h"
#include "whack.h"
#include "nat_traversal.h"

/* monotonic version of time(3) */
time_t
now(void)
{
    static time_t delta = 0
	, last_time = 0;
    time_t n = time((time_t)NULL);

    passert(n != (time_t)-1);
    if (last_time > n)
    {
	plog("time moved backwards %ld seconds", (long)(last_time - n));
	delta += last_time - n;
    }
    last_time = n;
    return n + delta;
}

/* This file has the event handling routines. Events are
 * kept as a linked list of event structures. These structures
 * have information like event type, expiration time and a pointer
 * to event specific data (for example, to a state structure).
 */

static struct event *evlist = (struct event *) NULL;

/*
 * This routine places an event in the event list.
 */
void
event_schedule(enum event_type type, time_t tm, struct state *st)
{
    struct event *ev = alloc_thing(struct event, "struct event in event_schedule()");

    ev->ev_type = type;
    ev->ev_time = tm + now();
    ev->ev_state = st;

    /* If the event is associated with a state, put a backpointer to the
     * event in the state object, so we can find and delete the event
     * if we need to (for example, if we receive a reply).
     */
    if (st != NULL)
    {
	if (type == EVENT_DPD || type == EVENT_DPD_TIMEOUT)
	{
	    passert(st->st_dpd_event == NULL);
	    st->st_dpd_event = ev;
	}
	else
	{
	    passert(st->st_event == NULL);
	    st->st_event = ev;
	}
    }

    DBG(DBG_CONTROL,
	if (st == NULL)
	    DBG_log("inserting event %s, timeout in %lu seconds"
		, enum_show(&timer_event_names, type), (unsigned long)tm);
	else
	    DBG_log("inserting event %s, timeout in %lu seconds for #%lu"
		, enum_show(&timer_event_names, type), (unsigned long)tm
		, ev->ev_state->st_serialno));

    if (evlist == (struct event *) NULL
    || evlist->ev_time >= ev->ev_time)
    {
	ev->ev_next = evlist;
	evlist = ev;
    }
    else
    {
	struct event *evt;

	for (evt = evlist; evt->ev_next != NULL; evt = evt->ev_next)
	    if (evt->ev_next->ev_time >= ev->ev_time)
		break;

#ifdef NEVER	/* this seems to be overkill */
	DBG(DBG_CONTROL,
	    if (evt->ev_state == NULL)
		DBG_log("event added after event %s"
		    , enum_show(&timer_event_names, evt->ev_type));
	    else
		DBG_log("event added after event %s for #%lu"
		    , enum_show(&timer_event_names, evt->ev_type)
		    , evt->ev_state->st_serialno));
#endif /* NEVER */

	ev->ev_next = evt->ev_next;
	evt->ev_next = ev;
    }
}

/*
 * Handle the first event on the list.
 */
void
handle_timer_event(void)
{
    time_t tm;
    struct event *ev = evlist;
    int type;
    struct state *st;
    struct connection *c = NULL;
    ip_address peer;

    if (ev == (struct event *) NULL)    /* Just paranoid */
    {
	DBG(DBG_CONTROL, DBG_log("empty event list, yet we're called"));
	return;
    }

    type = ev->ev_type;
    st = ev->ev_state;

    tm = now();

    if (tm < ev->ev_time)
    {
	DBG(DBG_CONTROL, DBG_log("called while no event expired (%lu/%lu, %s)"
	    , (unsigned long)tm, (unsigned long)ev->ev_time
	    , enum_show(&timer_event_names, type)));

	/* This will happen if the most close-to-expire event was
	 * a retransmission or cleanup, and we received a packet
	 * at the same time as the event expired. Due to the processing
	 * order in call_server(), the packet processing will happen first,
	 * and the event will be removed.
	 */
	return;
    }

    evlist = evlist->ev_next;		/* Ok, we'll handle this event */

    DBG(DBG_CONTROL,
	if (evlist != (struct event *) NULL)
	    DBG_log("event after this is %s in %ld seconds"
		, enum_show(&timer_event_names, evlist->ev_type)
		, (long) (evlist->ev_time - tm)));

    /* for state-associated events, pick up the state pointer
     * and remove the backpointer from the state object.
     * We'll eventually either schedule a new event, or delete the state.
     */
    passert(GLOBALS_ARE_RESET());
    if (st != NULL)
    {
	c = st->st_connection;
	if (type  == EVENT_DPD || type == EVENT_DPD_TIMEOUT)
	{
	    passert(st->st_dpd_event == ev);
	    st->st_dpd_event = NULL;
	}
	else 
	{
	    passert(st->st_event == ev);
	    st->st_event = NULL;
	}
	peer = c->spd.that.host_addr;
	set_cur_state(st);
    }

    switch (type)
    {
	case EVENT_REINIT_SECRET:
	    passert(st == NULL);
	    DBG(DBG_CONTROL, DBG_log("event EVENT_REINIT_SECRET handled"));
	    init_secret();
	    break;

#ifdef KLIPS
	case EVENT_SHUNT_SCAN:
	    passert(st == NULL);
	    scan_proc_shunts();
	    break;
#endif

	case EVENT_LOG_DAILY:
	    daily_log_event();
	    break;

	case EVENT_RETRANSMIT:
	    /* Time to retransmit, or give up.
	     *
	     * Generally, we'll only try to send the message
	     * MAXIMUM_RETRANSMISSIONS times.  Each time we double
	     * our patience.
	     *
	     * As a special case, if this is the first initiating message
	     * of a Main Mode exchange, and we have been directed to try
	     * forever, we'll extend the number of retransmissions to
	     * MAXIMUM_RETRANSMISSIONS_INITIAL times, with all these
	     * extended attempts having the same patience.  The intention
	     * is to reduce the bother when nobody is home.
	     */
	    {
		time_t delay = 0;

		DBG(DBG_CONTROL, DBG_log(
		    "handling event EVENT_RETRANSMIT for %s \"%s\" #%lu"
		    , ip_str(&peer), c->name, st->st_serialno));

		if (st->st_retransmit < MAXIMUM_RETRANSMISSIONS)
		    delay = EVENT_RETRANSMIT_DELAY_0 << (st->st_retransmit + 1);
		else if (st->st_state == STATE_MAIN_I1
		&& c->sa_keying_tries == 0
		&& st->st_retransmit < MAXIMUM_RETRANSMISSIONS_INITIAL)
		    delay = EVENT_RETRANSMIT_DELAY_0 << MAXIMUM_RETRANSMISSIONS;

		if (delay != 0)
		{
		    st->st_retransmit++;
		    whack_log(RC_RETRANSMISSION
			, "%s: retransmission; will wait %lus for response"
			, enum_name(&state_names, st->st_state)
			, (unsigned long)delay);
		    send_packet(st, "EVENT_RETRANSMIT");
		    event_schedule(EVENT_RETRANSMIT, delay, st);
		}
		else
		{
		    /* check if we've tried rekeying enough times.
		     * st->st_try == 0 means that this should be the only try.
		     * c->sa_keying_tries == 0 means that there is no limit.
		     */
		    unsigned long try = st->st_try;
		    unsigned long try_limit = c->sa_keying_tries;
		    const char *details = "";

		    switch (st->st_state)
		    {
		    case STATE_MAIN_I3:
			details = ".  Possible authentication failure:"
			    " no acceptable response to our"
			    " first encrypted message";
			break;
		    case STATE_MAIN_I1:
			details = ".  No response (or no acceptable response) to our"
			    " first IKE message";
			break;
		    case STATE_QUICK_I1:
			if (c->newest_ipsec_sa == SOS_NOBODY)
			    details = ".  No acceptable response to our"
				" first Quick Mode message:"
				" perhaps peer likes no proposal";
			break;
		    default:
			break;
		    }
		    loglog(RC_NORETRANSMISSION
			, "max number of retransmissions (%d) reached %s%s"
			, st->st_retransmit
			, enum_show(&state_names, st->st_state), details);
		    if (try != 0 && try != try_limit)
		    {
			/* A lot like EVENT_SA_REPLACE, but over again.
			 * Since we know that st cannot be in use,
			 * we can delete it right away.
			 */
			char story[80];	/* arbitrary limit */

			try++;
			snprintf(story, sizeof(story), try_limit == 0
			    ? "starting keying attempt %ld of an unlimited number"
			    : "starting keying attempt %ld of at most %ld"
			    , try, try_limit);

			if (st->st_whack_sock != NULL_FD)
			{
			    /* Release whack because the observer will get bored. */
			    loglog(RC_COMMENT, "%s, but releasing whack"
				, story);
			    release_pending_whacks(st, story);
			}
			else
			{
			    /* no whack: just log to syslog */
			    plog("%s", story);
			}
			ipsecdoi_replace(st, try);
		    }
		    delete_state(st);
		}
	    }
	    break;

	case EVENT_SA_REPLACE:
	case EVENT_SA_REPLACE_IF_USED:
	    {
		so_serial_t newest = IS_PHASE1(st->st_state)
		    ? c->newest_isakmp_sa : c->newest_ipsec_sa;

		if (newest != st->st_serialno
		&& newest != SOS_NOBODY)
		{
		    /* not very interesting: no need to replace */
		    DBG(DBG_LIFECYCLE
			, plog("not replacing stale %s SA: #%lu will do"
			    , IS_PHASE1(st->st_state)? "ISAKMP" : "IPsec"
			    , newest));
		}
		else if (type == EVENT_SA_REPLACE_IF_USED
		&& st->st_outbound_time <= tm - c->sa_rekey_margin)
		{
		    /* we observed no recent use: no need to replace
		     *
		     * The sampling effects mean that st_outbound_time
		     * could be up to SHUNT_SCAN_INTERVAL more recent
		     * than actual traffic because the sampler looks at change
		     * over that interval.
		     * st_outbound_time could also not yet reflect traffic
		     * in the last SHUNT_SCAN_INTERVAL.
		     * We expect that SHUNT_SCAN_INTERVAL is smaller than
		     * c->sa_rekey_margin so that the effects of this will
		     * be unimportant.
		     * This is just an optimization: correctness is not
		     * at stake.
		     *
		     * Note: we are abusing the DBG mechanism to control
		     * normal log output.
		     */
		    DBG(DBG_LIFECYCLE
			, plog("not replacing stale %s SA: inactive for %lus"
			    , IS_PHASE1(st->st_state)? "ISAKMP" : "IPsec"
			    , (unsigned long)(tm - st->st_outbound_time)));
		}
		else
		{
		    DBG(DBG_LIFECYCLE
			, plog("replacing stale %s SA"
			    , IS_PHASE1(st->st_state)? "ISAKMP" : "IPsec"));
		    ipsecdoi_replace(st, 1);
		}
		delete_dpd_event(st);
		event_schedule(EVENT_SA_EXPIRE, st->st_margin, st);
	    }
	    break;

	case EVENT_SA_EXPIRE:
	    {
		const char *satype;
		so_serial_t latest;

		if (IS_PHASE1(st->st_state))
		{
		    satype = "ISAKMP";
		    latest = c->newest_isakmp_sa;
		}
		else
		{
		    satype = "IPsec";
		    latest = c->newest_ipsec_sa;
		}

		if (st->st_serialno != latest)
		{
		    /* not very interesting: already superseded */
		    DBG(DBG_LIFECYCLE
			, plog("%s SA expired (superseded by #%lu)"
			    , satype, latest));
		}
		else
		{
		    plog("%s SA expired (%s)", satype
			, (c->policy & POLICY_DONT_REKEY)
			    ? "--dontrekey"
			    : "LATEST!"
			);
		}
	    }
	    /* FALLTHROUGH */
	case EVENT_SO_DISCARD:
	    /* Delete this state object.  It must be in the hash table. */
	    delete_state(st);
	    break;

	case EVENT_DPD:
	    dpd_outI(st);
	    break;
	case EVENT_DPD_TIMEOUT:
	    dpd_timeout(st);
	    break;
	case EVENT_NAT_T_KEEPALIVE:
	    nat_traversal_ka_event();
	    break;
	default:
	    loglog(RC_LOG_SERIOUS, "INTERNAL ERROR: ignoring unknown expiring event %s"
		, enum_show(&timer_event_names, type));
    }

    pfree(ev);
    reset_cur_state();
}

/*
 * Return the time until the next event in the queue
 * expires (never negative), or -1 if no jobs in queue.
 */
long
next_event(void)
{
    time_t tm;

    if (evlist == (struct event *) NULL)
	return -1;

    tm = now();

    DBG(DBG_CONTROL,
	if (evlist->ev_state == NULL)
	    DBG_log("next event %s in %ld seconds"
		, enum_show(&timer_event_names, evlist->ev_type)
		, (long)evlist->ev_time - (long)tm);
	else
	    DBG_log("next event %s in %ld seconds for #%lu"
		, enum_show(&timer_event_names, evlist->ev_type)
		, (long)evlist->ev_time - (long)tm
		, evlist->ev_state->st_serialno));

    if (evlist->ev_time - tm <= 0)
	return 0;
    else
	return evlist->ev_time - tm;
}

/*
 * Delete an event.
 */
void
delete_event(struct state *st)
{
    if (st->st_event != (struct event *) NULL)
    {
	struct event **ev;

	for (ev = &evlist; ; ev = &(*ev)->ev_next)
	{
	    if (*ev == NULL)
	    {
		DBG(DBG_CONTROL, DBG_log("event %s to be deleted not found",
		    enum_show(&timer_event_names, st->st_event->ev_type)));
		break;
	    }
	    if ((*ev) == st->st_event)
	    {
		*ev = (*ev)->ev_next;

		if (st->st_event->ev_type == EVENT_RETRANSMIT)
		    st->st_retransmit = 0;
		pfree(st->st_event);
		st->st_event = (struct event *) NULL;

		break;
	    }
	}
    }
}

/*
 * Delete a DPD event.
 */
void
delete_dpd_event(struct state *st)
{
    if (st->st_dpd_event != (struct event *) NULL)
    {
        struct event **ev;

        for (ev = &evlist; ; ev = &(*ev)->ev_next)
        {
            if (*ev == NULL)
            {
                DBG(DBG_CONTROL, DBG_log("event %s to be deleted not found",
                    enum_show(&timer_event_names, st->st_dpd_event->ev_type)));
                break;
            }
            if ((*ev) == st->st_dpd_event)
            {
                *ev = (*ev)->ev_next;
                pfree(st->st_dpd_event);
                st->st_dpd_event = (struct event *) NULL;
                break;
            }
        }
    }
}