l2tpns/cluster.c

// L2TPNS Clustering Stuff

char const *cvs_id_cluster = "$Id: cluster.c,v 1.6 2004-07-05 06:54:01 bodea Exp $";

#include <stdio.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <string.h>
#include <malloc.h>
#include <errno.h>
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>
#include <stdio.h>
#include <libcli.h>

#include "l2tpns.h"
#include "cluster.h"
#include "util.h"
#include "tbf.h"

#ifdef BGP
#include "bgp.h"
#endif
/*
 * All cluster packets have the same format.
 *
 * One or more instances of
 *	a 32 bit 'type' id.
 *	a 32 bit 'extra' data dependant on the 'type'.
 *	zero or more bytes of structure data, dependant on the type.
 *
 */

// Module variables.
int cluster_sockfd = 0;		// The filedescriptor for the cluster communications port.

ipt my_address = 0;		// The network address of my ethernet port.
static int walk_session_number = 0;	// The next session to send when doing the slow table walk.
static int walk_tunnel_number = 0;	// The next tunnel to send when doing the slow table walk.

static int hsess, fsess;	// Saved copies of the highest used session id, and the first free one.

#define MAX_HEART_SIZE (8192)	// Maximum size of heartbeat packet. Must be less than max IP packet size :)
#define MAX_CHANGES  (MAX_HEART_SIZE/(sizeof(sessiont) + sizeof(int) ) - 2)	// Assumes a session is the biggest type!

static struct {
	int type;
	int id;
} cluster_changes[MAX_CHANGES];	// Queue of changed structures that need to go out when next heartbeat.

static struct {
	int seq;
	int size;
	char data[MAX_HEART_SIZE];
} past_hearts[HB_HISTORY_SIZE];	// Ring buffer of heartbeats that we've recently sent out. Needed so
				// we can re-transmit if needed.

static struct {
	u32 peer;
	time_t	basetime;
	clockt	timestamp;
	int	uptodate;
} peers[CLUSTER_MAX_SIZE];	// List of all the peers we've heard from.
static int num_peers;		// Number of peers in list.
static int have_peers;		// At least one peer

int rle_decompress(u8 ** src_p, int ssize, u8 *dst, int dsize);
int rle_compress(u8 ** src_p, int ssize, u8 *dst, int dsize);

//
// Create a listening socket
//
// This joins the cluster multi-cast group.
//
int cluster_init()
{
    struct sockaddr_in addr;
    struct sockaddr_in interface_addr;
    struct ip_mreq mreq;
    struct ifreq   ifr;
    int opt = 0;

    config->cluster_undefined_sessions = MAXSESSION-1;
    config->cluster_undefined_tunnels = MAXTUNNEL-1;

    if (!config->cluster_address)
	return 0;
    if (!*config->cluster_interface)
	return 0;

    cluster_sockfd = socket(AF_INET, SOCK_DGRAM, UDP);

    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(CLUSTERPORT);
    addr.sin_addr.s_addr = INADDR_ANY;
    setsockopt(cluster_sockfd, SOL_SOCKET, SO_REUSEADDR, &addr, sizeof(addr));

    if (bind(cluster_sockfd, (void *) &addr, sizeof(addr)) < 0)
    {
	log(0, 0, 0, 0, "Failed to bind cluster socket: %s\n", strerror(errno));
	return -1;
    }

    strcpy(ifr.ifr_name, config->cluster_interface);
    if (ioctl(cluster_sockfd, SIOCGIFADDR, &ifr) < 0) {
	log(0, 0, 0, 0, "Failed to get interface address for (%s): %s\n", config->cluster_interface, strerror(errno));
	return -1;
    }

    memcpy(&interface_addr, &ifr.ifr_addr, sizeof(interface_addr) );
    my_address = interface_addr.sin_addr.s_addr;

		// Join multicast group.
    mreq.imr_multiaddr.s_addr = config->cluster_address;
    mreq.imr_interface = interface_addr.sin_addr;


    opt = 0;	// Turn off multicast loopback.
    setsockopt(cluster_sockfd, IPPROTO_IP, IP_MULTICAST_LOOP, &opt, sizeof(opt));

    if (setsockopt(cluster_sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0) {
	log(0, 0, 0, 0, "Failed to setsockopt (join mcast group): %s\n", strerror(errno));
	return -1;
    }

    if (setsockopt (cluster_sockfd, IPPROTO_IP, IP_MULTICAST_IF, &interface_addr, sizeof(interface_addr)) < 0) {
	log(0, 0, 0, 0, "Failed to setsockopt (set mcast interface): %s\n", strerror(errno));
	return -1;
    }

    config->cluster_last_hb = TIME;
    config->cluster_seq_number = -1;

    return cluster_sockfd;
}


//
// Send a chunk of data to the entire cluster (usually via the multicast
// address ).
//

int cluster_send_data(void *data, int datalen)
{
    struct sockaddr_in addr = {0};

    if (!cluster_sockfd) return -1;
    if (!config->cluster_address) return 0;

    addr.sin_addr.s_addr = config->cluster_address;
    addr.sin_port = htons(CLUSTERPORT);
    addr.sin_family = AF_INET;

//    log_hex(4, "Cluster send", data, datalen); // VERY big data packets. How about we don't..

    log(5,0,0,0, "Cluster send data: %d bytes\n", datalen);

    if (sendto(cluster_sockfd, data, datalen, MSG_NOSIGNAL, (void *) &addr, sizeof(addr)) < 0)
    {
	log(0, 0, 0, 0, "sendto: %s\n", strerror(errno));
	return -1;
    }

    return 0;
}

//
// Add a chunk of data to a heartbeat packet.
// Maintains the format. Assumes that the caller
// has passed in a big enough buffer!
//
static void add_type(char ** p, int type, int more, char * data, int size)
{
	* ( (u32*)(*p) ) = type;
	*p += sizeof(u32);

	* ( (u32*)(*p) ) = more;
	*p += sizeof(u32);

	if (data && size > 0) {
		memcpy(*p, data, size);
		(*p) += size;
	}
}

void cluster_uptodate(void)
{
	if (config->cluster_iam_uptodate)
		return;

	if (config->cluster_undefined_sessions || config->cluster_undefined_tunnels)
		return;

	config->cluster_iam_uptodate = 1;

	log(0,0,0,0, "Now uptodate with master.\n");

		// If we're not a master, or if we have no slaves
		// then start taking traffic..
	if (!config->cluster_iam_master || !have_peers)
	{
#ifdef BGP
		if (bgp_configured)
			bgp_enable_routing(1);
		else
#endif /* BGP */
			if (config->send_garp)
				send_garp(config->bind_address);	// Start taking traffic.
	}
}

//
// Send a unicast UDP packet to a peer with 'data' as the
// contents.
//
int peer_send_data(u32 peer, char * data, int size)
{
    struct sockaddr_in addr = {0};

    if (!cluster_sockfd) return -1;
    if (!config->cluster_address) return 0;

    if (!peer)	// Odd??
	return -1;

    addr.sin_addr.s_addr = peer;
    addr.sin_port = htons(CLUSTERPORT);
    addr.sin_family = AF_INET;

    log_hex(5, "Peer send", data, size);

    if (sendto(cluster_sockfd, data, size, MSG_NOSIGNAL, (void *) &addr, sizeof(addr)) < 0)
    {
	log(0, 0, 0, 0, "sendto: %s\n", strerror(errno));
	return -1;
    }

    return 0;
}

//
// Send a structured message to a peer with a single element of type 'type'.
//
int peer_send_message(u32 peer, int type, int more, char * data, int size)
{
	char buf[65536];	// Vast overkill.
	char * p = buf;

	log(4,0,0,0, "Sending message to peer (type %d, more %d, size %d)\n", type, more, size);
	add_type(&p, type, more, data, size);

	return peer_send_data(peer, buf, (p-buf) );
}

//
// Forward a state changing packet to the master.
//
// The master just processes the payload as if it had
// received it off the tap device.
//
int master_forward_packet(char * data, int size, u32 addr, int port)
{
	char buf[65536];	// Vast overkill.
	char * p = buf;

	if (!config->cluster_master_address) // No election has been held yet. Just skip it.
		return -1;

	log(4,0,0,0,	"Forwarding packet from %s to master (size %d)\n", inet_toa(addr), size);

	STAT(c_forwarded);
	add_type(&p, C_FORWARD, addr, (char*) &port, sizeof(port) );
	memcpy(p, data, size);
	p += size;

	return peer_send_data(config->cluster_master_address, buf, (p-buf) );

}

//
// Forward a throttled packet to the master for handling.
//
// The master just drops the packet into the appropriate
// token bucket queue, and lets normal processing take care
// of it.
//
int master_throttle_packet(int tbfid, char * data, int size)
{
	char buf[65536];	// Vast overkill.
	char * p = buf;

	if (!config->cluster_master_address) // No election has been held yet. Just skip it.
		return -1;

	log(4,0,0,0,	"Throttling packet master (size %d, tbfid %d)\n", size, tbfid);

	add_type(&p, C_THROTTLE, tbfid, data, size);

	return peer_send_data(config->cluster_master_address, buf, (p-buf) );

}

//
// Forward a walled garden packet to the master for handling.
//
// The master just writes the packet straight to the tun
// device (where is will normally loop through the
// firewall rules, and come back in on the tun device)
//
// (Note that this must be called with the tun header
// as the start of the data).
int master_garden_packet(sessionidt s, char *data, int size)
{
	char buf[65536];	// Vast overkill.
	char *p = buf;

	if (!config->cluster_master_address) // No election has been held yet. Just skip it.
		return -1;

	log(4,0,0,0,	"Walled garden packet to master (size %d)\n", size);

	add_type(&p, C_GARDEN, s, data, size);

	return peer_send_data(config->cluster_master_address, buf, (p-buf));

}

//
// Send a chunk of data as a heartbeat..
// We save it in the history buffer as we do so.
//
static void send_heartbeat(int seq, char * data, int size)
{
    int i;

    if (size > sizeof(past_hearts[0].data)) {
	log(0,0,0,0, "Tried to heartbeat something larger than the maximum packet!\n");
	kill(0, SIGTERM);
	exit(1);
    }
    i = seq % HB_HISTORY_SIZE;
    past_hearts[i].seq = seq;
    past_hearts[i].size = size;
    memcpy(&past_hearts[i].data, data, size);	// Save it.
    cluster_send_data(data, size);
}

//
// Send an 'i am alive' message to every machine in the cluster.
//
void cluster_send_ping(time_t basetime)
{
	char buff[100 + sizeof(pingt)];
	char *p = buff;
	pingt x;

	if (config->cluster_iam_master && basetime)		// We're heartbeating so no need to ping.
		return;

	log(5,0,0,0, "Sending cluster ping...\n");

	x.ver = 1;
	x.addr = config->bind_address;
	x.undef = config->cluster_undefined_sessions + config->cluster_undefined_tunnels;
	x.basetime = basetime;

	add_type(&p, C_PING, basetime, (char *) &x, sizeof(x));
	cluster_send_data(buff, (p-buff) );
}

//
// Walk the session counters looking for non-zero ones to send
// to the master. We send up to 100 of them at one time.
// We examine a maximum of 2000 sessions.
// (50k max session should mean that we normally
// examine the entire session table every 25 seconds).

#define MAX_B_RECS (400)
void master_update_counts(void)
{
	int i, c;
	bytest b[MAX_B_RECS+1];

	if (config->cluster_iam_master)		// Only happens on the slaves.
		return;

	if (!config->cluster_master_address)		// If we don't have a master, skip it for a while.
		return;

	i = MAX_B_RECS * 5; // Examine max 2000 sessions;
	if (config->cluster_highest_sessionid > i)
		i = config->cluster_highest_sessionid;

	for ( c = 0; i > 0 ; --i) {
			// Next session to look at.
		walk_session_number++;
		if ( walk_session_number > config->cluster_highest_sessionid)
			walk_session_number = 1;

		if (!sess_count[walk_session_number].cin && !sess_count[walk_session_number].cout)
			continue; // Unused. Skip it.

		b[c].sid = walk_session_number;
		b[c].in = sess_count[walk_session_number].cin;
		b[c].out = sess_count[walk_session_number].cout;

		if (++c > MAX_B_RECS)	// Send a max of 400 elements in a packet.
			break;

			// Reset counters.
		sess_count[walk_session_number].cin = sess_count[walk_session_number].cout = 0;
	}

	if (!c)		// Didn't find any that changes. Get out of here!
		return;


			// Forward the data to the master.
	log(4,0,0,0, "Sending byte counters to master (%d elements)\n", c);
	peer_send_message(config->cluster_master_address, C_BYTES, c, (char*) &b, sizeof(b[0]) * c);
	return;
}

//
// Check that we have a master. If it's been too
// long since we heard from a master then hold an election.
//
void cluster_check_master(void)
{
	int i, count, tcount, high_sid = 0;
	int last_free = 0;
	int had_peers = have_peers;
	clockt t = TIME;
	static int probed = 0;

		// Is the master late? If so, try probing it...
	if (TIME > (config->cluster_last_hb + config->cluster_hb_timeout/8 + 11)) {
		if (!probed) {
	   		if (config->cluster_master_address) {
				peer_send_message(config->cluster_master_address,
					C_LASTSEEN, config->cluster_seq_number, NULL, 0);
				probed = 1;
			}
		}
	} else {	// We got a recent heartbeat; reset the probe flag.
		probed = 0;
	}

	if (TIME < (config->cluster_last_hb + config->cluster_hb_timeout) )
		return;		// Everything's ok. return.

	if (!config->cluster_iam_master)
		log(0,0,0,0, "Master timed out! Holding election...\n");

	config->cluster_last_hb = TIME + 1;

	for (i = have_peers = 0; i < num_peers ; ++i) {
		if ((peers[i].timestamp + config->cluster_hb_timeout) < t)
			continue;	// Stale peer! Skip them.

		if (!peers[i].basetime)
			continue;	// Shutdown peer! Skip them.

		have_peers = 1;
		if (peers[i].basetime < basetime) {
			log(1,0,0,0, "Expecting %s to become master\n", inet_toa(peers[i].peer) );
			return;		// They'll win the election. Get out of here.
		}

		if (peers[i].basetime == basetime &&
			peers[i].peer > my_address) {
			log(1,0,0,0, "Expecting %s to become master\n", inet_toa(peers[i].peer) );
			return;		// They'll win the election. Wait for them to come up.
		}
	}

	if (config->cluster_iam_master)		// If we're the master, we've already won
	{
#ifdef BGP
		// master lost all slaves, need to handle traffic ourself
		if (bgp_configured && had_peers && !have_peers)
			bgp_enable_routing(1);
#endif /* BGP */
		return;
	}

		// Wow. it's been ages since I last heard a heartbeat
		// and I'm better than an of my peers so it's time
		// to become a master!!!

	config->cluster_iam_master = 1;
	config->cluster_master_address = 0;

	log(0,0,0,0, "I am declaring myself the master!\n");

#ifdef BGP
	if (bgp_configured && have_peers)
		bgp_enable_routing(0); /* stop handling traffic */
#endif /* BGP */

	if (config->cluster_seq_number == -1)
		config->cluster_seq_number = 0;

		//
		// Go through and mark all the tunnels as defined.
		// Count the highest used tunnel number as well.
		//
	config->cluster_highest_tunnelid = 0;
	for (i = 0, tcount = 0; i < MAXTUNNEL; ++i) {
		if (tunnel[i].state == TUNNELUNDEF)
			tunnel[i].state = TUNNELFREE;

		if (tunnel[i].state != TUNNELFREE && i > config->cluster_highest_tunnelid)
			config->cluster_highest_tunnelid = i;
	}

		//
		// Go through and mark all the sessions as being defined.
		// reset the idle timeouts.
		// add temporary byte counters to permanent ones.
		// Re-string the free list.
		// Find the ID of the highest session.
	last_free = 0;
	high_sid = 0;
	config->cluster_highest_sessionid = 0;
	for (i = 0, count = 0; i < MAXSESSION; ++i) {
		if (session[i].tunnel == T_UNDEF) {
			session[i].tunnel = T_FREE;
			++count;
		}

		if (session[i].tunnel == T_FREE) { // Unused session. Add to free list.
			session[last_free].next = i;
			session[i].next = 0;
			last_free = i;
		}

			// Reset all the idle timeouts..
		session[i].last_packet = time_now;

			// Accumulate un-sent byte counters.
		session[i].cin += sess_count[i].cin;
		session[i].cout += sess_count[i].cout;
		session[i].total_cin += sess_count[i].cin;
		session[i].total_cout += sess_count[i].cout;

		sess_count[i].cin = sess_count[i].cout = 0;

		session[i].radius = 0;	// Reset authentication as the radius blocks aren't up to date.

		if (session[i].sid >= high_sid)	// This is different to the index into the session table!!!
			high_sid = session[i].sid+1;


		session[i].tbf_in = session[i].tbf_out = 0; // Remove stale pointers from old master.
		throttle_session(i, session[i].throttle);

// I'm unsure about this. --mo
// It's potentially a good thing, but it could send a
// LOT of packets.
//		if (session[i].throttle)
//			cluster_send_session(s);	// Tell the slaves about the new tbf indexes.

		if (session[i].tunnel != T_FREE && i > config->cluster_highest_sessionid)
			config->cluster_highest_sessionid = i;

	}

	session[last_free].next = 0;	// End of chain.
	last_sid = high_sid;		// Keep track of the highest used session ID.

	become_master();

	rebuild_address_pool();

		// If we're not the very first master, this is a big issue!
	if(count>0)
		log(0,0,0,0, "Warning: Fixed %d uninitialized sessions in becoming master!\n", count);

	config->cluster_undefined_sessions = 0;
	config->cluster_undefined_tunnels = 0;

		//
		// FIXME. We need to fix up the tunnel control message
		// queue here! There's a number of other variables we
		// should also update.
	cluster_uptodate();
}


//
// Check that our session table is validly matching what the
// master has in mind.
//
// In particular, if we have too many sessions marked 'undefined'
// we fix it up here, and we ensure that the 'first free session'
// pointer is valid.
//
static void cluster_check_sessions(int highsession, int freesession_ptr, int hightunnel)
{
	int i;

	sessionfree = freesession_ptr;	// Keep the freesession ptr valid.

	if (config->cluster_iam_uptodate)
		return;

	if (highsession > config->cluster_undefined_sessions && hightunnel > config->cluster_undefined_tunnels)
		return;

		// Clear out defined sessions, counting the number of
		// undefs remaining.
	config->cluster_undefined_sessions = 0;
	for (i = 1 ; i < MAXSESSION; ++i) {
		if (i > highsession) {
			session[i].tunnel = 0; // Defined.
			continue;
		}
		if (session[i].tunnel != T_UNDEF)
			continue;
		++config->cluster_undefined_sessions;
	}

		// Clear out defined tunnels, counting the number of
		// undefs remaining.
	config->cluster_undefined_tunnels = 0;
	for (i = 1 ; i < MAXTUNNEL; ++i) {
		if (i > hightunnel) {
			tunnel[i].state = TUNNELFREE; // Defined.
			continue;
		}
		if (tunnel[i].state != TUNNELUNDEF)
			continue;
		++config->cluster_undefined_tunnels;
	}


	if (config->cluster_undefined_sessions || config->cluster_undefined_tunnels) {
		log(2,0,0,0, "Cleared undefined sessions/tunnels. %d sess (high %d), %d tunn (high %d)\n",
			config->cluster_undefined_sessions, highsession, config->cluster_undefined_tunnels, hightunnel);
		return;
	}

		// Are we up to date?

	if (!config->cluster_iam_uptodate)
		cluster_uptodate();
}

int hb_add_type(char **p, int type, int id)
{
	switch (type) {
		case C_CSESSION: { // Compressed C_SESSION.
			u8 c[sizeof(sessiont) * 2]; // Bigger than worst case.
			u8 *d = (u8 *) &session[id];
			u8 *orig = d;
			int size;

			size = rle_compress( &d,  sizeof(sessiont), c, sizeof(c) );

				// Did we compress the full structure, and is the size actually
				// reduced??
			if ( (d - orig) == sizeof(sessiont) && size < sizeof(sessiont) ) {
				add_type(p, C_CSESSION, id, (char*) c, size);
				break;
			}
			// Failed to compress : Fall through.
		}
		case C_SESSION: add_type(p, C_SESSION, id,
			(char*) &session[id], sizeof(sessiont));
			break;

		case C_CTUNNEL: { // Compressed C_TUNNEL
			u8 c[sizeof(tunnelt) * 2]; // Bigger than worst case.
			u8 *d = (u8 *) &tunnel[id];
			u8 *orig = d;
			int size;

			size = rle_compress( &d,  sizeof(tunnelt), c, sizeof(c) );

				// Did we compress the full structure, and is the size actually
				// reduced??
			if ( (d - orig) == sizeof(tunnelt) && size < sizeof(tunnelt) ) {
				add_type(p, C_CTUNNEL, id, c, size);
				break;
			}
			// Failed to compress : Fall through.
		}
		case C_TUNNEL: add_type(p, C_TUNNEL, id,
			(char*) &tunnel[id], sizeof(tunnelt));
			break;
		default:
			log(0,0,0,0, "Found an invalid type in heart queue! (%d)\n", type);
			kill(0, SIGTERM);
	}
	return 0;
}

//
// Send a heartbeat, incidently sending out any queued changes..
//
void cluster_heartbeat(int highsession, int freesession, int hightunnel)
{
	int i, count = 0, tcount = 0;
	char buff[MAX_HEART_SIZE + sizeof(heartt) + sizeof(int) ];
	heartt h;
	char * p = buff;

	if (!config->cluster_iam_master)	// Only the master does this.
		return;

	hsess = highsession;
	fsess = freesession;
		// Fill out the heartbeat header.
	h.version = HB_VERSION;
	h.seq = config->cluster_seq_number;
	h.basetime = basetime;
	h.clusterid = config->bind_address;	// Will this do??
	h.basetime = basetime;
	h.highsession = highsession;
	h.freesession = freesession;
	h.hightunnel = hightunnel;
	h.size_sess = sizeof(sessiont);		// Just in case.
	h.size_tunn = sizeof(tunnelt);

	add_type(&p, C_HEARTBEAT, HB_VERSION, (char*) &h, sizeof(h) );

	for (i = 0; i < config->cluster_num_changes; ++i) {
		hb_add_type(&p, cluster_changes[i].type, cluster_changes[i].id);
	}

	if (p > (buff + sizeof(buff))) {	// Did we somehow manage to overun the buffer?
		log(0,0,0,0, "FATAL: Overran the heartbeat buffer! This is fatal. Exiting. (size %d)\n", p - buff);
		kill(0, SIGTERM);
	}

		//
		// Fill out the packet with sessions from the session table...
		// (not forgetting to leave space so we can get some tunnels in too )
	while ( (p + sizeof(u32) * 2 + sizeof(sessiont) * 2 ) < (buff + MAX_HEART_SIZE) ) {

		if (!walk_session_number)	// session #0 isn't valid.
			++walk_session_number;

		if (count >= highsession)	// If we're a small cluster, don't go wild.
			break;

		hb_add_type(&p, C_CSESSION, walk_session_number);
		walk_session_number = (1+walk_session_number)%(highsession+1);	// +1 avoids divide by zero.

		++count;			// Count the number of extra sessions we're sending.
	}

		//
		// Fill out the packet with tunnels from the tunnel table...
		// This effectively means we walk the tunnel table more quickly
		// than the session table. This is good because stuffing up a 
		// tunnel is a much bigger deal than stuffing up a session.
		//
	while ( (p + sizeof(u32) * 2 + sizeof(tunnelt) ) < (buff + MAX_HEART_SIZE) ) {

		if (!walk_tunnel_number)	// tunnel #0 isn't valid.
			++walk_tunnel_number;

		if (tcount >= config->cluster_highest_tunnelid)
			break;

		hb_add_type(&p, C_CTUNNEL, walk_tunnel_number);
		walk_tunnel_number = (1+walk_tunnel_number)%(config->cluster_highest_tunnelid+1);	// +1 avoids divide by zero.

		++tcount;
	}

		//
		// Did we do something wrong?
	if (p > (buff + sizeof(buff))) {	// Did we somehow manage to overun the buffer?
		log(0,0,0,0, "Overran the heartbeat buffer now! This is fatal. Exiting. (size %d)\n", p - buff);
		kill(0, SIGTERM);
	}

	log(3,0,0,0, "Sending heartbeat #%d with %d changes (%d x-sess, %d x-tunnels, %d highsess, %d hightun size %d)\n",
			h.seq, config->cluster_num_changes, count, tcount, config->cluster_highest_sessionid,
			config->cluster_highest_tunnelid, (p-buff));

	config->cluster_num_changes = 0;

	send_heartbeat(h.seq, buff, (p-buff) ); // Send out the heartbeat to the cluster, keeping a copy of it.

	config->cluster_seq_number = (config->cluster_seq_number+1)%HB_MAX_SEQ;	// Next seq number to use.
}

//
// A structure of type 'type' has changed; Add it to the queue to send.
//
int type_changed(int type, int id)
{
	int i;

	for (i = 0 ; i < config->cluster_num_changes ; ++i)
		if ( cluster_changes[i].id == id &&
			cluster_changes[i].type == type)
			return 0;	// Already marked for change.

	cluster_changes[i].type = type;
	cluster_changes[i].id = id;
	++config->cluster_num_changes;

	if (config->cluster_num_changes > MAX_CHANGES)
		cluster_heartbeat(config->cluster_highest_sessionid, fsess, config->cluster_highest_tunnelid);

	return 1;
}


// A particular session has been changed!
int cluster_send_session(int sid)
{
	if (!config->cluster_iam_master) {
		log(0,0,sid,0, "I'm not a master, but I just tried to change a session!\n");
		return -1;
	}

	return type_changed(C_CSESSION, sid);
}

// A particular tunnel has been changed!
int cluster_send_tunnel(int tid)
{
	if (!config->cluster_iam_master) {
		log(0,0,0,tid, "I'm not a master, but I just tried to change a tunnel!\n");
		return -1;
	}

	return type_changed(C_CTUNNEL, tid);
}


//
// We're a master, and a slave has just told us that it's
// missed a packet. We'll resend it every packet since
// the last one it's seen.
//
int cluster_catchup_slave(int seq, u32 slave)
{
	int s;
	int diff;

	log(1,0,0,0, "Slave %s sent LASTSEEN with seq %d\n", inet_toa(slave), seq);

	diff = config->cluster_seq_number - seq;	// How many packet do we need to send?
	if (diff < 0)
		diff += HB_MAX_SEQ;

	if (diff >= HB_HISTORY_SIZE) {	// Ouch. We don't have the packet to send it!
		log(0,0,0,0, "A slaved asked for message %d when our seq number is %d. Killing it.\n",
			seq, config->cluster_seq_number);
		return peer_send_message(slave, C_KILL, seq, NULL, 0);// Kill the slave. Nothing else to do.
	}

		// Now resend every packet that it missed, in order.
	while (seq != config->cluster_seq_number) {
		s = seq%HB_HISTORY_SIZE;
		if (seq != past_hearts[s].seq) {
			log(0,0,0,0, "Tried to re-send heartbeat for %s but %d doesn't match %d! (%d,%d)\n",
				inet_toa(slave), seq, past_hearts[s].seq, s, config->cluster_seq_number);
			return -1;	// What to do here!?
		}
		peer_send_data(slave, past_hearts[s].data, past_hearts[s].size);
		seq = (seq+1)%HB_MAX_SEQ;	// Increment to next seq number.
	}
	return 0; // All good!
}

//
// We've heard from another peer! Add it to the list
// that we select from at election time.
//
int cluster_add_peer(u32 peer, time_t basetime, pingt *p)
{
	int i;
	u32 clusterid;

	clusterid = p->addr;
	if (clusterid != config->bind_address)
	{
		// Is this for us?
		log(4,0,0,0, "Skipping ping from %s (different cluster)\n", inet_toa(peer));
		return 0;
	}

		// Is this the master shutting down??
	if (peer == config->cluster_master_address && !basetime) {
		config->cluster_master_address = 0;
		config->cluster_last_hb = 0; // Force an election.
		cluster_check_master();
		return 0;
	}

	for (i = 0; i < num_peers ; ++i)
	{
		if (peers[i].peer != peer)
			continue;

		// This peer already exists. Just update the timestamp.
		peers[i].basetime = basetime;
		peers[i].timestamp = TIME;
		break;
	}

	if (i >= num_peers)
	{
		log(4,0,0,0, "Adding %s as a peer\n", inet_toa(peer));

		// Not found. Is there a stale slot to re-use?
		for (i = 0; i < num_peers ; ++i)
		{
			if (peers[i].peer != peer)
				continue;
			if ((peers[i].timestamp + config->cluster_hb_timeout * 10) < TIME) // Stale.
				break;
		}

		if (i >= CLUSTER_MAX_SIZE)
		{
			// Too many peers!!
			log(0,0,0,0, "Tried to add %s as a peer, but I already have %d of them!\n", inet_toa(peer), i);
			return -1;
		}

		peers[i].peer = peer;
		peers[i].basetime = basetime;
		peers[i].timestamp = TIME;
		if (i == num_peers)
			++num_peers;

		log(1,0,0,0, "Added %s as a new peer. Now %d peers\n", inet_toa(peer), num_peers);
	}

#ifdef BGP
	/* drop routes if we've now got a peer */
	if (bgp_configured && config->cluster_iam_master && !have_peers)
		bgp_enable_routing(0);
#endif /* BGP */

	have_peers = 1;

	return 1;
}

/* Handle the slave updating the byte counters for the master. */
//
// Note that we don't mark the session as dirty; We rely on
// the slow table walk to propogate this back out to the slaves.
//
int cluster_handle_bytes(char * data, int size)
{
	bytest * b;

	b = (bytest*) data;

	log(3,0,0,0, "Got byte counter update (size %d)\n", size);

				/* Loop around, adding the byte
				counts to each of the sessions. */

	while (size >= sizeof(*b) ) {
		if (b->sid > MAXSESSION) {
			log(0,0,0,0, "Got C_BYTES with session #%d!\n", b->sid);
			return -1; /* Abort processing */
		}

		session[b->sid].total_cin += b->in;
		session[b->sid].total_cout += b->out;

		session[b->sid].cin += b->in;
		session[b->sid].cout += b->out;
		session[b->sid].last_packet = time_now; // Reset idle timer!

		size -= sizeof(*b);
		++b;
	}

	if (size != 0)
		log(0,0,0,0, "Got C_BYTES with %d bytes of trailing junk!\n", size);

	return size;
}

//
// Handle receiving a session structure in a heartbeat packet.
//
static int cluster_recv_session(int more , u8 * p)
{
	if (more >= MAXSESSION) {
		log(0,0,0,0, "DANGER: Received a heartbeat session id > MAXSESSION!\n");
		return -1;
	}

	if (session[more].tunnel == T_UNDEF) {
		if (config->cluster_iam_uptodate) { // Sanity.
			log(0,0,0,0, "I thought I was uptodate but I just found an undefined session!\n");
		} else {
			--config->cluster_undefined_sessions;
		}
	}

	load_session(more, (sessiont*) p);	// Copy session into session table..

	log(5,0,more,0, "Received session update (%d undef)\n", config->cluster_undefined_sessions);

	if (!config->cluster_iam_uptodate)
		cluster_uptodate();	// Check to see if we're up to date.
	return 0;
}

static int cluster_recv_tunnel(int more, u8 *p)
{
	if (more >= MAXTUNNEL) {
		log(0,0,0,0, "DANGER: Received a tunnel session id > MAXTUNNEL!\n");
		return -1;
	}

	if (tunnel[more].state == TUNNELUNDEF) {
		if (config->cluster_iam_uptodate) { // Sanity.
			log(0,0,0,0, "I thought I was uptodate but I just found an undefined tunnel!\n");
		} else {
			--config->cluster_undefined_tunnels;
		}
	}

	memcpy(&tunnel[more], p, sizeof(tunnel[more]) );

		//
		// Clear tunnel control messages. These are dynamically allocated.
		// If we get unlucky, this may cause the tunnel to drop!
		//
	tunnel[more].controls = tunnel[more].controle = NULL;
	tunnel[more].controlc = 0;

	log(5,0,0,more, "Received tunnel update\n");

	if (!config->cluster_iam_uptodate)
		cluster_uptodate();	// Check to see if we're up to date.

	return 0;
}


//
// Process a version one heartbeat..
//
static int cluster_process_heartbeat_v2(u8 * data, int size, int more, u8 * p, u32 addr)
{
	heartt * h;
	int s = size - (p-data);
	int i, type;

	if (more != HB_VERSION) {
		log(0,0,0,0, "Received a heartbeat version that I don't understand!\n");
		return -1; // Ignore it??
	}
		// Ok. It's a heartbeat packet from a cluster master!
	if (s < sizeof(*h))
		goto shortpacket;


	h = (heartt*) p;
	p += sizeof(*h);
	s -= sizeof(*h);

	if (h->clusterid != config->bind_address)
		return -1;	// It's not part of our cluster.

	if (config->cluster_iam_master) {	// Sanity...
				// Note that this MUST match the election process above!

		log(0,0,0,0, "I just got a packet claiming to be from a master but _I_ am the master!\n");
		if (!h->basetime) {
			log(0,0,0,0, "Heartbeat from addr %s with zero basetime!\n", inet_toa(addr) );
			return -1; // Skip it.
		}
		if (basetime > h->basetime) {
			log(0,0,0,0, "They're (%s) an older master than me so I'm gone!\n", inet_toa(addr));
			kill(0, SIGTERM);
			exit(1);
		}
		if (basetime == h->basetime && my_address < addr) { // Tie breaker.
			log(0,0,0,0, "They're a higher IP address than me, so I'm gone!\n");
			kill(0, SIGTERM);
			exit(1);
		}
		return -1; // Skip it.
	}

	if (config->cluster_seq_number == -1)	// Don't have one. Just align to the master...
		config->cluster_seq_number = h->seq;

	config->cluster_last_hb = TIME;	// Reset to ensure that we don't become master!!

	if (config->cluster_seq_number != h->seq) {	// Out of sequence heartbeat!
		log(1,0,0,0, "HB: Got seq# %d but was expecting %d. asking for resend.\n", h->seq, config->cluster_seq_number);

		peer_send_message(addr, C_LASTSEEN, config->cluster_seq_number, NULL, 0);

		config->cluster_last_hb = TIME;	// Reset to ensure that we don't become master!!

			// Just drop the packet. The master will resend it as part of the catchup.

		return 0;
	}
		// Save the packet in our buffer.
		// This is needed in case we become the master.
	config->cluster_seq_number = (h->seq+1)%HB_MAX_SEQ;
	i = h->seq % HB_HISTORY_SIZE;
	past_hearts[i].seq = h->seq;
	past_hearts[i].size = size;
	memcpy(&past_hearts[i].data, data, size);	// Save it.


			// Check that we don't have too many undefined sessions, and
			// that the free session pointer is correct.
	cluster_check_sessions(h->highsession, h->freesession, h->hightunnel);

		// Ok. process the packet...
	while ( s > 0) {

		type = * ((u32*) p);
		p += sizeof(u32);
		s -= sizeof(u32);

		more = * ((u32*) p);
		p += sizeof(u32);
		s -= sizeof(u32);

		switch (type) {
			case C_CSESSION: { // Compressed session structure.
				u8 c [ sizeof(sessiont) + 2];
				int size;
				u8 * orig_p = p;

				size = rle_decompress((u8 **) &p, s, c, sizeof(c) );
				s -= (p - orig_p);

				if (size != sizeof(sessiont) ) { // Ouch! Very very bad!
					log(0,0,0,0, "DANGER: Received a CSESSION that didn't decompress correctly!\n");
						// Now what? Should exit! No-longer up to date!
					break;
				}

				cluster_recv_session(more, c);
				break;
			}
			case C_SESSION:
				if ( s < sizeof(session[more]))
					goto shortpacket;

				cluster_recv_session(more, p);

				p += sizeof(session[more]);
				s -= sizeof(session[more]);
				break;

			case C_CTUNNEL: { // Compressed tunnel structure.
				u8 c [ sizeof(tunnelt) + 2];
				int size;
				u8 * orig_p = p;

				size = rle_decompress( (u8 **) &p, s, c, sizeof(c) );
				s -= (p - orig_p);

				if (size != sizeof(tunnelt) ) { // Ouch! Very very bad!
					log(0,0,0,0, "DANGER: Received a CSESSION that didn't decompress correctly!\n");
						// Now what? Should exit! No-longer up to date!
					break;
				}

				cluster_recv_tunnel(more, c);
				break;

			}
			case C_TUNNEL:
				if ( s < sizeof(tunnel[more]))
					goto shortpacket;

				cluster_recv_tunnel(more, p);

				p += sizeof(tunnel[more]);
				s -= sizeof(tunnel[more]);
				break;
			default:
				log(0,0,0,0, "DANGER: I received a heartbeat element where I didn't understand the type! (%d)\n", type);
				return -1; // can't process any more of the packet!!
		}
	}
	if (config->cluster_master_address != addr)
	{
		char *str;
		str = strdup(inet_toa(config->cluster_master_address));
		log(0,0,0,0, "My master just changed from %s to %s!\n", str, inet_toa(addr));
		if (str) free(str);
	}

	config->cluster_master_address = addr;
	config->cluster_last_hb = TIME;	// Successfully received a heartbeat!
	return 0;

shortpacket:
	log(0,0,0,0, "I got an incomplete heartbeat packet! This means I'm probably out of sync!!\n");
	return -1;
}

//
// We got a packet on the cluster port!
// Handle pings, lastseens, and heartbeats!
//
int processcluster(char * data, int size, u32 addr)
{
	int type, more;
	char * p = data;
	int s = size;

	if (addr == my_address)
		return -1;	// Ignore it. Something looped back the multicast!

	log(5,0,0,0, "Process cluster: %d bytes from %s\n", size, inet_toa(addr));

	if (s <= 0)	// Any data there??
		return -1;

	if (s < 8)
		goto shortpacket;

	type = * ((u32*) p);
	p += sizeof(u32);
	s -= sizeof(u32);

	more = * ((u32*) p);
	p += sizeof(u32);
	s -= sizeof(u32);

	switch (type) {
	case C_PING:	// Update the peers table.
		return cluster_add_peer(addr, more, (pingt*)p);

	case C_LASTSEEN:	// Catch up a slave (slave missed a packet).
		return cluster_catchup_slave(more, addr);

	case C_FORWARD: { // Forwarded control packet. pass off to processudp.
		struct sockaddr_in a;
		a.sin_addr.s_addr = more;

		a.sin_port = * (int*) p;
		s -= sizeof(int);
		p += sizeof(int);

		if (!config->cluster_iam_master) { // huh?
			log(0,0,0,0, "I'm not the master, but I got a C_FORWARD from %s?\n", inet_toa(addr));
			return -1;
		}

		log(4,0,0,0, "Got a forwarded packet... (%s:%d)\n", inet_toa(more), a.sin_port);
		STAT(recv_forward);
		processudp(p, s, &a);
		return 0;
	}
	case C_THROTTLE: {	// Receive a forwarded packet from a slave.
		if (!config->cluster_iam_master) {
			log(0,0,0,0, "I'm not the master, but I got a C_THROTTLE from %s?\n", inet_toa(addr));
			return -1;
		}

		tbf_queue_packet(more, p, s);	// The TBF id tells wether it goes in or out.
		return 0;
	}
	case C_GARDEN:
		// Receive a walled garden packet from a slave.
		if (!config->cluster_iam_master) {
			log(0,0,0,0, "I'm not the master, but I got a C_GARDEN from %s?\n", inet_toa(addr));
			return -1;
		}

		tun_write(p, s);
		return 0;

	case C_BYTES:
		return cluster_handle_bytes(p, s);

	case C_KILL:	// The master asked us to die!? (usually because we're too out of date).
		if (config->cluster_iam_master) {
			log(0,0,0,0, "_I_ am master, but I received a C_KILL from %s! (Seq# %d)\n", inet_toa(addr), more);
			return -1;
		}
		if (more != config->cluster_seq_number) {
			log(0,0,0,0, "The master asked us to die but the seq number didn't match!?\n");
			return -1;
		}

		if (addr != config->cluster_master_address) {
			log(0,0,0,0, "Received a C_KILL from %s which doesn't match config->cluster_master_address (%x)\n",
				inet_toa(addr), config->cluster_master_address);
			// We can only warn about it. The master might really have switched!
		}

		log(0,0,0,0, "Received a valid C_KILL: I'm going to die now.\n");
		kill(0, SIGTERM);
		exit(0);	// Lets be paranoid;
		return -1;		// Just signalling the compiler.

	case C_HEARTBEAT:
		log(4,0,0,0, "Got a heartbeat from %s\n", inet_toa(addr));

		return cluster_process_heartbeat_v2(data, size, more, p, addr);

	default:
		log(0,0,0,0, "Strange type packet received on cluster socket (%d)\n", type);
		return -1;
	}
	return 0;
shortpacket:
	log(0,0,0,0, "I got an cluster heartbeat packet! This means I'm probably out of sync!!\n");
	return -1;
}

//====================================================================================================

int cmd_show_cluster(struct cli_def *cli, char *command, char **argv, int argc)
{
	int i;

	if (CLI_HELP_REQUESTED)
		return CLI_HELP_NO_ARGS;

        cli_print(cli, "Cluster status   : %s", config->cluster_iam_master ? "Master" : "Slave" );
	cli_print(cli, "My address       : %s", inet_toa(my_address));
	cli_print(cli, "VIP address      : %s", inet_toa(config->bind_address));
	cli_print(cli, "Multicast address: %s", inet_toa(config->cluster_address));
	cli_print(cli, "Multicast i'face : %s", config->cluster_interface);

        if (!config->cluster_iam_master) {
		cli_print(cli, "My master        : %s (last heartbeat %.1f seconds old)",
			config->cluster_master_address ? inet_toa(config->cluster_master_address) : "Not defined",
			0.1 * (TIME - config->cluster_last_hb));
                cli_print(cli, "Uptodate         : %s", config->cluster_iam_uptodate ? "Yes" : "No");
		cli_print(cli, "Next sequence number expected: %d", config->cluster_seq_number);
		cli_print(cli, "%d sessions undefined of %d", config->cluster_undefined_sessions, config->cluster_highest_sessionid);
		cli_print(cli, "%d tunnels undefined of %d", config->cluster_undefined_tunnels, config->cluster_highest_tunnelid);
	} else {
		cli_print(cli, "Next heartbeat # : %d", config->cluster_seq_number);
		cli_print(cli, "Highest session  : %d", config->cluster_highest_sessionid);
		cli_print(cli, "Highest tunnel   : %d", config->cluster_highest_tunnelid);
		cli_print(cli, "%d changes queued for sending", config->cluster_num_changes);
	}
	cli_print(cli, "%d peers.", num_peers);

	if (num_peers)
		cli_print(cli, "%20s  %10s %8s", "Address", "Basetime", "Age");
	for (i = 0; i < num_peers; ++i) {
		cli_print(cli, "%20s  %10d %8d", inet_toa(peers[i].peer),
			peers[i].basetime, TIME - peers[i].timestamp);
	}
	return CLI_OK;
}

//
// Simple run-length-encoding compression.
// Format is
//	1 byte < 128 = count of non-zero bytes following.	// Not legal to be zero.
//	n non-zero bytes;
// or
//	1 byte > 128 = (count - 128) run of zero bytes.		//
//   repeat.
//   count == 0 indicates end of compressed stream.
//
// Compress from 'src' into 'dst'. return number of bytes
// used from 'dst'.
// Updates *src_p to indicate 1 past last bytes used.
//
// We could get an extra byte in the zero runs by storing (count-1)
// but I'm playing it safe.
//
// Worst case is a 50% expansion in space required (trying to
// compress { 0x00, 0x01 } * N )
int rle_compress(u8 ** src_p, int ssize, u8 *dst, int dsize)
{
	int count;
	int orig_dsize = dsize;
	u8 * x,*src;
	src = *src_p;

	while (ssize > 0 && dsize > 2) {
		count = 0;
		x = dst++; --dsize;	// Reserve space for count byte..

		if (*src) {		// Copy a run of non-zero bytes.
			while (*src && count < 127 && ssize > 0 && dsize > 1) { // Count number of non-zero bytes.
				*dst++ = *src++;
				--dsize; --ssize;
				++count;
			}
			*x = count;	// Store number of non-zero bytes. Guarenteed to be non-zero!

		} else {		// Compress a run of zero bytes.
			while (*src == 0 && count < 127 && ssize > 0) {
				++src;
				--ssize;
				++count;
			}
			*x = count | 0x80 ;
		}
	}

	*dst++ = 0x0; // Add Stop byte.
	--dsize;

	*src_p = src;
	return (orig_dsize - dsize);
}

//
// Decompress the buffer into **p.
// 'psize' is the size of the decompression buffer available.
//
// Returns the number of bytes decompressed.
//
// Decompresses from '*src_p' into 'dst'.
// Return the number of dst bytes used.
// Updates the 'src_p' pointer to point to the
// first un-used byte.
int rle_decompress(u8 ** src_p, int ssize, u8 *dst, int dsize)
{
	int count;
	int orig_dsize = dsize;
	char * src = *src_p;

	while (ssize >0 && dsize > 0) {	// While there's more to decompress, and there's room in the decompress buffer...
		count = *src++; --ssize;  // get the count byte from the source.
		if (count == 0x0)	// End marker reached? If so, finish.
			break;

		if (count & 0x80) {	// Decompress a run of zeros
			for (count &= 0x7f ; count > 0 && dsize > 0; --count) {
				*dst++ = 0x0;
				--dsize;
			}
		} else { 		// Copy run of non-zero bytes.
			for ( ; count > 0 && ssize && dsize; --count) {	// Copy non-zero bytes across.
				*dst++ = *src++;
				--ssize; --dsize;
			}
		}
	}
	*src_p = src;
	return (orig_dsize - dsize);
}