dpd.c

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/* IPsec IKE Dead Peer Detection code.
 * Copyright (C) 2003 Ken Bantoft        <[e-mail]>
 * Copyright (C) 2004 Michael Richardson <[e-mail]>
 *
 * 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: dpd.c,v 1.29.2.6 2005/12/27 22:30:36 ken Exp $
 */

#include <stdio.h>
#include <string.h>
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <resolv.h>
#include <arpa/nameser.h>	/* missing from <resolv.h> on old systems */
#include <sys/queue.h>
#include <sys/time.h>		/* for gettimeofday */

#include <openswan.h>
#include <openswan/ipsec_policy.h>

#include "constants.h"
#include "defs.h"
#include "state.h"
#include "id.h"
#include "x509.h"
#include "pgp.h"
#include "certs.h"
#include "smartcard.h"
#ifdef XAUTH_USEPAM
#include <security/pam_appl.h>
#endif
#include "connections.h"	/* needs id.h */
#include "keys.h"
#include "packet.h"
#include "demux.h"	/* needs packet.h */
#include "adns.h"	/* needs <resolv.h> */
#include "dnskey.h"	/* needs keys.h and adns.h */
#include "kernel.h"	/* needs connections.h */
#include "log.h"
#include "cookie.h"
#include "server.h"
#include "spdb.h"
#include "timer.h"
#include "rnd.h"
#include "ipsec_doi.h"	/* needs demux.h and state.h */
#include "whack.h"

#include "dpd.h"
#include "x509more.h"

/**
 * Initialize RFC 3706 Dead Peer Detection
 *
 * @param st An initialized state structure
 * @return void
 *
 * How DPD works.
 *
 * There are two kinds of events that can be scheduled.
 * At most one of them is schedule at any given time.
 *
 * The EVENT_DPD_TIMEOUT event, if it ever goes off, means that
 * neither the ISAKMP SA nor the IPsec SA has *RECEIVED* any DPD
 * events lately.
 *
 * 0) So, every time we receive a DPD (R_U_THERE or R_U_ACK), then
 *    we delete any DPD event (EVENT_DPD or EVENT_DPD_TIMEOUT), and
 *    we schedule a new DPD_EVENT (sending) for "delay" in the future.
 *
 * 1) When the DPD_EVENT goes off, we check the phase 2 (if there is one)
 *    SA to see if there was incoming traffic. If there was, then we are happy,
 *    we set a new DPD_EVENT, and we are done.
 *
 * 2) If there was no phase 2 activity, we check if there was a recent enough
 *    DPD activity (st->st_last_dpd). If so, we just reschedule, and do
 *    nothing.
 *
 * 3) Otherwise, we send a DPD R_U_THERE message, and set the
 *    EVENT_DPD_TIMEOUT on the phase 1.
 *
 * One thing to realize when looking at "ipsec whack --listevents" output,
 * is there there will only be DPD_EVENT_TIMEOUT events if there are
 * outstanding R_U_THERE messages.
 *
 * The above is the basic idea, but things are a bit more complicated because
 * multiple phase 2s can share the same phase 1 ISAKMP SA. Each phase 2 state
 * has its own DPD_EVENT. Further, we start a DPD_EVENT for phase 1 when it
 * gets established. This is because the phase 2 may never actually succeed
 * (usually due to authorization issues, which may be DNS or otherwise related)
 * and if the responding end dies (gets restarted, or the conn gets reloaded
 * with the right policy), then we may have a bum phase 1 SA, and we can not
 * re-negotiate. (This happens WAY too often)
 *
 * The phase 2 dpd_init() will attempt to kill the phase 1 DPD_EVENT, if it
 * can, to reduce the amount of work. 
 *
 * The st_last_dpd member which is used is always the one from the phase 1.
 * So, if there are multiple phase 2s, then if any of them receive DPD data
 * they will update the st_last_dpd, so the test in #2 will avoid the traffic
 * for all by one phase 2. 
 * 
 * Note that the EVENT_DPD are attached to phase 2s (typically), while the
 * EVENT_DPD_TIMEOUT are attached to phase 1s only.
 *
 * Finally, if the connection is using NAT-T, then we ignore the phase 2
 * activity check, because in the case of a unidirectional stream (VoIP for
 * a conference call, for instance), we may not send enough traffic to keep
 * the NAT port mapping valid.
 *
 */ 

stf_status
dpd_init(struct state *st)
{
    /**
     * Used to store the 1st state 
     */
    struct state *p1st;

    /* find the related Phase 1 state */
    p1st = find_state(st->st_icookie, st->st_rcookie,
		      &st->st_connection->spd.that.host_addr, 0);

    if (p1st == NULL) {
        loglog(RC_LOG_SERIOUS, "DPD: Serious: could not find phase 1 state for DPD");

	/*
	 * if the phase 1 state has gone away, it really should have
	 * deleted all of its children.
	 * Why would this happen? because a quick mode SA can take
	 * some time to create (DNS lookups for instance), and the phase 1
	 * might have been taken down for some reason in the meantime.
	 * We really can not do anything here --- attempting to invoke
	 * the DPD action would be a good idea, but we really should
	 * do that outside this function.
	 */
	return STF_FAIL;
    }

    /* if it was enabled, and we haven't turned it on already */
    if (p1st->hidden_variables.st_dpd) {
	time_t n = now();
	openswan_log("Dead Peer Detection (RFC 3706): enabled");

	if(st->st_dpd_event == NULL
	   || (st->st_connection->dpd_delay + n) < st->st_dpd_event->ev_time) {
	    delete_dpd_event(st);
	    event_schedule(EVENT_DPD, st->st_connection->dpd_delay, st);
	}

    } else {
      openswan_log("Dead Peer Detection (RFC 3706): not enabled because peer did not advertise it");
    }

    if(p1st != st) {
	/* st was not a phase 1 SA, so kill the DPD_EVENT on the phase 1 */
	if(p1st->st_dpd_event != NULL
	   && p1st->st_dpd_event->ev_type == EVENT_DPD) {
	    delete_dpd_event(p1st);
	}
    }
    return STF_OK;
}

bool was_eroute_idle(struct state *st, time_t since_when);

/*
 * Only schedule a new timeout if there isn't one currently,
 * or if it would be sooner than the current timeout.
 */
static void
dpd_sched_timeout(struct state *p1st, time_t tm, time_t timeout)
{
    passert(timeout > 0);
    if (p1st->st_dpd_event == NULL
	|| p1st->st_dpd_event->ev_time > tm + timeout)
    {
	DBG(DBG_DPD, DBG_log("DPD: Debug: scheduling timeout to %lu"
			     , timeout));
        delete_dpd_event(p1st);
        event_schedule(EVENT_DPD_TIMEOUT, timeout, p1st);
    }   
}

/**
 * DPD Out Initiator
 *
 * @param p2st A state struct that is already in phase2 
 * @return void
 */
static void
dpd_outI(struct state *p1st, struct state *st, bool eroute_care
	 ,time_t delay, time_t timeout)
{
    time_t tm;
    time_t last;
    u_int32_t seqno;
    bool   eroute_idle;
    time_t nextdelay;

    DBG(DBG_DPD, DBG_log("DPD: Debug: processing dpd for state #%lu (\"%s\")"
			 , st->st_serialno
			 , st->st_connection->name));

    /* If no DPD, then get out of here */
    if (!st->hidden_variables.st_dpd)
        return;

    /* If there is no state, there can be no DPD */         
    if (!IS_ISAKMP_SA_ESTABLISHED(p1st->st_state))
        return;
      
    /* find out when now is */
    tm = now();

    /*
     * pick least recent activity value, since with multiple phase 2s,
     * it may well be that one phase 2 is very active, while the other
     * for some reason, gets stomped upon by some network screw up.
     *
     * (this would only happen if the network was sensitive to different
     *  SPI#, since for NAT-T, all traffic should be on the same UDP port.
     *  At worst, this means that we send a bit more traffic then we need
     *  to when there are multiple SAs and one is much less active.
     *
     */
    last = (p1st->st_last_dpd > st->st_last_dpd
	    ? st->st_last_dpd : p1st->st_last_dpd );

    nextdelay = p1st->st_last_dpd + delay - tm;

    /* has there been enough activity of late? */
    if(nextdelay > 0) {
	/* Yes, just reschedule "phase 2" */
	DBG(DBG_DPD, DBG_log("DPD: Debug: not yet time for dpd event: %lu < %lu"
			     , tm, (p1st->st_last_dpd + delay)));
	event_schedule(EVENT_DPD, nextdelay, st);
	return;
    }
      
    /* now plan next check time */
    if(nextdelay < 1) {
	nextdelay = delay;
    }

    /*
     * check the phase 2, if we are supposed to,
     * and return if it is active recently 
     */
    if(eroute_care && !st->hidden_variables.st_nat_traversal) {
      
	eroute_idle = was_eroute_idle(st, delay);
	if(!eroute_idle) {
	    DBG(DBG_DPD, DBG_log("DPD: Debug: out event not sent, phase 2 active"));
	    
	    /* update phase 2 time stamp only */
	    st->st_last_dpd = tm;
	    
	    event_schedule(EVENT_DPD, nextdelay, st);
	    return;
	}
    }

    if(st != p1st) {
	/*
	 * reschedule next event, since we can not do it from the activity
	 * routine.
	 */
	event_schedule(EVENT_DPD, nextdelay, st); 
    }
        
    if (!p1st->st_dpd_seqno)
    {   
        /* Get a non-zero random value that has room to grow */
        get_rnd_bytes((u_char *)&p1st->st_dpd_seqno
		      , sizeof(p1st->st_dpd_seqno));
        p1st->st_dpd_seqno &= 0x7fff;
        p1st->st_dpd_seqno++;