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cluster.c

// L2TPNS Clustering Stuff

char const *cvs_id_cluster = "$Id: cluster.c,v 1.50.2.1 2006/12/02 14:09:14 bodea Exp $";

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>
#include <inttypes.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 <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.
extern int cluster_sockfd;          // The filedescriptor for the cluster communications port.

in_addr_t 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.
int forked = 0;                     // Sanity check: CLI must not diddle with heartbeat table

#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;
      uint8_t 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 {
      in_addr_t peer;
      uint32_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 rle_decompress(uint8_t **src_p, int ssize, uint8_t *dst, int dsize);
static int rle_compress(uint8_t **src_p, int ssize, uint8_t *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;

      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, IPPROTO_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));

      opt = fcntl(cluster_sockfd, F_GETFL, 0);
      fcntl(cluster_sockfd, F_SETFL, opt | O_NONBLOCK);

      if (bind(cluster_sockfd, (void *) &addr, sizeof(addr)) < 0)
      {
            LOG(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, "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 (config->cluster_mcast_ttl != 1)
      {
            uint8_t ttl = 0;
            if (config->cluster_mcast_ttl > 0)
                  ttl = config->cluster_mcast_ttl < 256 ? config->cluster_mcast_ttl : 255;

            setsockopt(cluster_sockfd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl));
      }

      if (setsockopt(cluster_sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
      {
            LOG(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, "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 ).
//

static 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(5, 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, "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(uint8_t **p, int type, int more, uint8_t *data, int size)
{
      *((uint32_t *) (*p)) = type;
      *p += sizeof(uint32_t);

      *((uint32_t *)(*p)) = more;
      *p += sizeof(uint32_t);

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

// advertise our presence via BGP or gratuitous ARP
static void advertise_routes(void)
{
#ifdef BGP
      if (bgp_configured)
            bgp_enable_routing(1);
      else
#endif /* BGP */
            if (config->send_garp)
                  send_garp(config->bind_address);    // Start taking traffic.
}

// withdraw our routes (BGP only)
static void withdraw_routes(void)
{
#ifdef BGP
      if (bgp_configured)
            bgp_enable_routing(0);
#endif /* BGP */
}

static 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, "Now uptodate with master.\n");
      advertise_routes();
}

//
// Send a unicast UDP packet to a peer with 'data' as the
// contents.
//
static int peer_send_data(in_addr_t peer, uint8_t *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, "sendto: %s\n", strerror(errno));
            return -1;
      }

      return 0;
}

//
// Send a structured message to a peer with a single element of type 'type'.
//
static int peer_send_message(in_addr_t peer, int type, int more, uint8_t *data, int size)
{
      uint8_t buf[65536];     // Vast overkill.
      uint8_t *p = buf;

      LOG(4, 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) );
}

// send a packet to the master
static int _forward_packet(uint8_t *data, int size, in_addr_t addr, int port, int type)
{
      uint8_t buf[65536];     // Vast overkill.
      uint8_t *p = buf;

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

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

      STAT(c_forwarded);
      add_type(&p, type, addr, (uint8_t *) &port, sizeof(port)); // ick. should be uint16_t
      memcpy(p, data, size);
      p += size;

      return peer_send_data(config->cluster_master_address, 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 tun device.
//
int master_forward_packet(uint8_t *data, int size, in_addr_t addr, int port)
{
      return _forward_packet(data, size, addr, port, C_FORWARD);
}

// Forward a DAE RADIUS packet to the master.
int master_forward_dae_packet(uint8_t *data, int size, in_addr_t addr, int port)
{
      return _forward_packet(data, size, addr, port, C_FORWARD_DAE);
}

//
// 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, uint8_t *data, int size)
{
      uint8_t buf[65536];     // Vast overkill.
      uint8_t *p = buf;

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

      LOG(4, 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, uint8_t *data, int size)
{
      uint8_t buf[65536];     // Vast overkill.
      uint8_t *p = buf;

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

      LOG(4, 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, uint8_t *data, int size)
{
      int i;

      if (size > sizeof(past_hearts[0].data))
      {
            LOG(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)
{
      uint8_t buff[100 + sizeof(pingt)];
      uint8_t *p = buff;
      pingt x;

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

      LOG(5, 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, (uint8_t *) &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 600 of them at one time.
// We examine a maximum of 3000 sessions.
// (50k max session should mean that we normally
// examine the entire session table every 25 seconds).

#define MAX_B_RECS (600)
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;

      // C_BYTES format changed in 2.1.0 (cluster version 5)
      // during upgrade from previous versions, hang onto our counters
      // for a bit until the new master comes up
      if (config->cluster_last_hb_ver < 5)
            return;

      i = MAX_B_RECS * 5; // Examine max 3000 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_local[walk_session_number].cin && !sess_local[walk_session_number].cout)
                  continue; // Unchanged. Skip it.

            b[c].sid = walk_session_number;
            b[c].pin = sess_local[walk_session_number].pin;
            b[c].pout = sess_local[walk_session_number].pout;
            b[c].cin = sess_local[walk_session_number].cin;
            b[c].cout = sess_local[walk_session_number].cout;

                  // Reset counters.
            sess_local[walk_session_number].pin = sess_local[walk_session_number].pout = 0;
            sess_local[walk_session_number].cin = sess_local[walk_session_number].cout = 0;

            if (++c > MAX_B_RECS)   // Send a max of 600 elements in a packet.
                  break;
      }

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


                  // Forward the data to the master.
      LOG(4, 0, 0, "Sending byte counters to master (%d elements)\n", c);
      peer_send_message(config->cluster_master_address, C_BYTES, c, (uint8_t *) &b, sizeof(b[0]) * c);
      return;
}

//
// On the master, check how our slaves are going. If
// one of them's not up-to-date we'll heartbeat faster.
// If we don't have any of them, then we need to turn
// on our own packet handling!
//
void cluster_check_slaves(void)
{
      int i;
      static int have_peers = 0;
      int had_peers = have_peers;
      clockt t = TIME;

      if (!config->cluster_iam_master)
            return;           // Only runs on the master...

      config->cluster_iam_uptodate = 1;   // cleared in loop below

      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.

            if (peers[i].uptodate)
                  have_peers++;
            else
                  config->cluster_iam_uptodate = 0; // Start fast heartbeats
      }

      // in a cluster, withdraw/add routes when we get a peer/lose peers
      if (have_peers != had_peers)
      {
            if (had_peers < config->cluster_master_min_adv &&
                have_peers >= config->cluster_master_min_adv)
                  withdraw_routes();

            else if (had_peers >= config->cluster_master_min_adv &&
                have_peers < config->cluster_master_min_adv)
                  advertise_routes();
      }
}

//
// 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_unique_id = 0;
      int last_free = 0;
      clockt t = TIME;
      static int probed = 0;
      int have_peers;

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

      // If the master is late (missed 2 hearbeats by a second and a
      // hair) it may be that the switch has dropped us from the
      // multicast group, try unicasting probes to the master
      // which will hopefully respond with a unicast heartbeat that
      // will allow us to limp along until the querier next runs.
      if (config->cluster_master_address
          && TIME > (config->cluster_last_hb + 2 * config->cluster_hb_interval + 11))
      {
            if (!probed || (TIME > (probed + 2 * config->cluster_hb_interval)))
            {
                  probed = TIME;
                  LOG(1, 0, 0, "Heartbeat from master %.1fs late, probing...\n",
                        0.1 * (TIME - (config->cluster_last_hb + config->cluster_hb_interval)));

                  peer_send_message(config->cluster_master_address,
                        C_LASTSEEN, config->cluster_seq_number, NULL, 0);
            }
      } 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!

      config->cluster_last_hb = TIME + 1; // Just the one election thanks.
      config->cluster_master_address = 0;

      LOG(0, 0, 0, "Master timed out! Holding election...\n");

      // In the process of shutting down, can't be master
      if (main_quit)
            return;

      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.

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

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

            if (peers[i].uptodate)
                  have_peers++;
      }

            // 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;

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

      if (have_peers < config->cluster_master_min_adv)
            advertise_routes();
      else
            withdraw_routes();

      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_unique_id = 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].opened) { // Unused session. Add to free list.
                  memset(&session[i], 0, sizeof(session[i]));
                  session[i].tunnel = T_FREE;
                  session[last_free].next = i;
                  session[i].next = 0;
                  last_free = i;
                  continue;
            }

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

                  // Reset die relative to our uptime rather than the old master's
            if (session[i].die) session[i].die = TIME;

                  // Accumulate un-sent byte/packet counters.
            increment_counter(&session[i].cin, &session[i].cin_wrap, sess_local[i].cin);
            increment_counter(&session[i].cout, &session[i].cout_wrap, sess_local[i].cout);
            session[i].cin_delta += sess_local[i].cin;
            session[i].cout_delta += sess_local[i].cout;

            session[i].pin += sess_local[i].pin;
            session[i].pout += sess_local[i].pout;

            sess_local[i].cin = sess_local[i].cout = 0;
            sess_local[i].pin = sess_local[i].pout = 0;

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

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

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

            config->cluster_highest_sessionid = i;
      }

      session[last_free].next = 0;  // End of chain.
      last_id = high_unique_id;     // 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, "Warning: Fixed %d uninitialized sessions in becoming master!\n", count);

      config->cluster_undefined_sessions = 0;
      config->cluster_undefined_tunnels = 0;
      config->cluster_iam_uptodate = 1; // assume all peers are up-to-date

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


//
// 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) {
                  if (session[i].tunnel == T_UNDEF) session[i].tunnel = T_FREE; // Defined.
                  continue;
            }

            if (session[i].tunnel == T_UNDEF)
                  ++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) {
                  if (tunnel[i].state == TUNNELUNDEF) tunnel[i].state = TUNNELFREE; // Defined.
                  continue;
            }

            if (tunnel[i].state == TUNNELUNDEF)
                  ++config->cluster_undefined_tunnels;
      }


      if (config->cluster_undefined_sessions || config->cluster_undefined_tunnels) {
            LOG(2, 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();
}

static int hb_add_type(uint8_t **p, int type, int id)
{
      switch (type) {
            case C_CSESSION: { // Compressed C_SESSION.
                  uint8_t c[sizeof(sessiont) * 2]; // Bigger than worst case.
                  uint8_t *d = (uint8_t *) &session[id];
                  uint8_t *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, c, size);
                        break;
                  }
                  // Failed to compress : Fall through.
            }
            case C_SESSION:
                  add_type(p, C_SESSION, id, (uint8_t *) &session[id], sizeof(sessiont));
                  break;

            case C_CTUNNEL: { // Compressed C_TUNNEL
                  uint8_t c[sizeof(tunnelt) * 2]; // Bigger than worst case.
                  uint8_t *d = (uint8_t *) &tunnel[id];
                  uint8_t *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, (uint8_t *) &tunnel[id], sizeof(tunnelt));
                  break;
            default:
                  LOG(0, 0, 0, "Found an invalid type in heart queue! (%d)\n", type);
                  kill(0, SIGTERM);
                  exit(1);
      }
      return 0;
}

//
// Send a heartbeat, incidently sending out any queued changes..
//
void cluster_heartbeat()
{
      int i, count = 0, tcount = 0;
      uint8_t buff[MAX_HEART_SIZE + sizeof(heartt) + sizeof(int) ];
      heartt h;
      uint8_t *p = buff;

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

      config->cluster_table_version += config->cluster_num_changes;

      // Fill out the heartbeat header.
      memset(&h, 0, sizeof(h));

      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 = config->cluster_highest_sessionid;
      h.freesession = sessionfree;
      h.hightunnel = config->cluster_highest_tunnelid;
      h.size_sess = sizeof(sessiont);           // Just in case.
      h.size_tunn = sizeof(tunnelt);
      h.interval = config->cluster_hb_interval;
      h.timeout  = config->cluster_hb_timeout;
      h.table_version = config->cluster_table_version;

      add_type(&p, C_HEARTBEAT, HB_VERSION, (uint8_t *) &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, "FATAL: Overran the heartbeat buffer! This is fatal. Exiting. (size %d)\n", (int) (p - buff));
            kill(0, SIGTERM);
            exit(1);
      }

            //
            // 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(uint32_t) * 2 + sizeof(sessiont) * 2 ) < (buff + MAX_HEART_SIZE) ) {

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

            if (count >= config->cluster_highest_sessionid) // 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)%(config->cluster_highest_sessionid+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(uint32_t) * 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, "Overran the heartbeat buffer now! This is fatal. Exiting. (size %d)\n", (int) (p - buff));
            kill(0, SIGTERM);
            exit(1);
      }

      LOG(3, 0, 0, "Sending v%d heartbeat #%d, change #%" PRIu64 " with %d changes "
                 "(%d x-sess, %d x-tunnels, %d highsess, %d hightun, size %d)\n",
          HB_VERSION, h.seq, h.table_version, config->cluster_num_changes,
          count, tcount, config->cluster_highest_sessionid,
          config->cluster_highest_tunnelid, (int) (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.
//
static 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(); // flush now

      return 1;
}


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

      if (forked) {
            LOG(0, sid, 0, "cluster_send_session called from child process!\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, 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.
//
static int cluster_catchup_slave(int seq, in_addr_t slave)
{
      int s;
      int diff;

      LOG(1, 0, 0, "Slave %s sent LASTSEEN with seq %d\n", fmtaddr(slave, 0), seq);
      if (!config->cluster_iam_master) {
            LOG(1, 0, 0, "Got LASTSEEN but I'm not a master! Redirecting it to %s.\n",
                  fmtaddr(config->cluster_master_address, 0));

            peer_send_message(slave, C_MASTER, config->cluster_master_address, NULL, 0);
            return 0;
      }

      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, "A slave 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.
      }

      LOG(1, 0, 0, "Sending %d catchup packets to slave %s\n", diff, fmtaddr(slave, 0) );

            // 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, "Tried to re-send heartbeat for %s but %d doesn't match %d! (%d,%d)\n",
                        fmtaddr(slave, 0), 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.
//
static int cluster_add_peer(in_addr_t peer, time_t basetime, pingt *pp, int size)
{
      int i;
      in_addr_t clusterid;
      pingt p;

      // Allow for backward compatability.
      // Just the ping packet into a new structure to allow
      // for the possibility that we might have received
      // more or fewer elements than we were expecting.
      if (size > sizeof(p))
            size = sizeof(p);

      memset( (void *) &p, 0, sizeof(p) );
      memcpy( (void *) &p, (void *) pp, size);

      clusterid = p.addr;
      if (clusterid != config->bind_address)
      {
            // Is this for us?
            LOG(4, 0, 0, "Skipping ping from %s (different cluster)\n", fmtaddr(peer, 0));
            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;
            peers[i].uptodate = !p.undef;
            break;
      }

      // Is this the master shutting down??
      if (peer == config->cluster_master_address) {
            LOG(3, 0, 0, "Master %s %s\n", fmtaddr(config->cluster_master_address, 0),
                  basetime ? "has restarted!" : "shutting down...");

            config->cluster_master_address = 0;
            config->cluster_last_hb = 0; // Force an election.
            cluster_check_master();
      }

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

            // Not found. Is there a stale slot to re-use?
            for (i = 0; i < num_peers ; ++i)
            {
                  if (!peers[i].basetime) // Shutdown
                        break;

                  if ((peers[i].timestamp + config->cluster_hb_timeout * 10) < TIME) // Stale.
                        break;
            }

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

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

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

      return 1;
}

// A slave responds with C_MASTER when it gets a message which should have gone to a master.
static int cluster_set_master(in_addr_t peer, in_addr_t master)
{
      if (config->cluster_iam_master)     // Sanity...
            return 0;

      LOG(3, 0, 0, "Peer %s set the master to %s...\n", fmtaddr(peer, 0),
            fmtaddr(master, 1));

      config->cluster_master_address = master;
      if (master)
      {
            // catchup with new master
            peer_send_message(master, C_LASTSEEN, config->cluster_seq_number, NULL, 0);

            // delay next election
            config->cluster_last_hb = TIME;
      }

      // run election (or reset "probed" if master was set)
      cluster_check_master();
      return 0;
}

/* 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.
//
static int cluster_handle_bytes(uint8_t *data, int size)
{
      bytest *b;

      b = (bytest *) data;

      LOG(3, 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, "Got C_BYTES with session #%d!\n", b->sid);
                  return -1; /* Abort processing */
            }

            session[b->sid].pin += b->pin;
            session[b->sid].pout += b->pout;

            increment_counter(&session[b->sid].cin, &session[b->sid].cin_wrap, b->cin);
            increment_counter(&session[b->sid].cout, &session[b->sid].cout_wrap, b->cout);

            session[b->sid].cin_delta += b->cin;
            session[b->sid].cout_delta += b->cout;

            if (b->cin)
                  session[b->sid].last_packet = time_now; // Reset idle timer!

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

      if (size != 0)
            LOG(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, uint8_t *p)
{
      if (more >= MAXSESSION) {
            LOG(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, "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, 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, uint8_t *p)
{
      if (more >= MAXTUNNEL) {
            LOG(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, "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, more, "Received tunnel update\n");

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

      return 0;
}


// pre v5 heartbeat session structure
struct oldsession {
      sessionidt next;
      sessionidt far;
      tunnelidt tunnel;
      in_addr_t ip;
      int ip_pool_index;
      unsigned long unique_id;
      uint16_t nr;
      uint16_t ns;
      uint32_t magic;
      uint32_t cin, cout;
      uint32_t pin, pout;
      uint32_t total_cin;
      uint32_t total_cout;
      uint32_t id;
      uint16_t throttle_in;
      uint16_t throttle_out;
      clockt opened;
      clockt die;
      time_t last_packet;
      in_addr_t dns1, dns2;
      routet route[MAXROUTE];
      uint16_t radius;
      uint16_t mru;
      uint16_t tbf_in;
      uint16_t tbf_out;
      uint8_t l2tp_flags;
      uint8_t reserved_old_snoop;
      uint8_t walled_garden;
      uint8_t flags1;
      char random_vector[MAXTEL];
      int random_vector_length;
      char user[129];
      char called[MAXTEL];
      char calling[MAXTEL];
      uint32_t tx_connect_speed;
      uint32_t rx_connect_speed;
      uint32_t flags;
#define SF_IPCP_ACKED   1     // Has this session seen an IPCP Ack?
#define SF_LCP_ACKED    2     // LCP negotiated
#define SF_CCP_ACKED    4     // CCP negotiated
      in_addr_t snoop_ip;
      uint16_t snoop_port;
      uint16_t sid;
      uint8_t filter_in;
      uint8_t filter_out;
      char reserved[18];
};

static uint8_t *convert_session(struct oldsession *old)
{
      static sessiont new;
      int i;

      memset(&new, 0, sizeof(new));

      new.next = old->next;
      new.far = old->far;
      new.tunnel = old->tunnel;
      new.flags = old->l2tp_flags;
      new.ip = old->ip;
      new.ip_pool_index = old->ip_pool_index;
      new.unique_id = old->unique_id;
      new.magic = old->magic;
      new.pin = old->pin;
      new.pout = old->pout;
      new.cin = old->total_cin;
      new.cout = old->total_cout;
      new.cin_delta = old->cin;
      new.cout_delta = old->cout;
      new.throttle_in = old->throttle_in;
      new.throttle_out = old->throttle_out;
      new.filter_in = old->filter_in;
      new.filter_out = old->filter_out;
      new.mru = old->mru;
      new.opened = old->opened;
      new.die = old->die;
      new.last_packet = old->last_packet;
      new.dns1 = old->dns1;
      new.dns2 = old->dns2;
      new.tbf_in = old->tbf_in;
      new.tbf_out = old->tbf_out;
      new.random_vector_length = old->random_vector_length;
      new.tx_connect_speed = old->tx_connect_speed;
      new.rx_connect_speed = old->rx_connect_speed;
      new.snoop_ip = old->snoop_ip;
      new.snoop_port = old->snoop_port;
      new.walled_garden = old->walled_garden;

      memcpy(new.random_vector, old->random_vector, sizeof(new.random_vector));
      memcpy(new.user, old->user, sizeof(new.user));
      memcpy(new.called, old->called, sizeof(new.called));
      memcpy(new.calling, old->calling, sizeof(new.calling));

      for (i = 0; i < MAXROUTE; i++)
            memcpy(&new.route[i], &old->route[i], sizeof(new.route[i]));

      if (new.opened)
      {
            new.ppp.phase = Establish;
            if (old->flags & (SF_IPCP_ACKED|SF_LCP_ACKED))
            {
                  new.ppp.phase = Network;
                  new.ppp.lcp   = Opened;
                  new.ppp.ipcp  = (old->flags & SF_IPCP_ACKED) ? Opened : Starting;
                  new.ppp.ccp   = (old->flags & SF_CCP_ACKED)  ? Opened : Stopped;
            }

            // no PPPv6 in old session
            new.ppp.ipv6cp = Stopped;
      }

      return (uint8_t *) &new;
}

//
// Process a heartbeat..
//
// v3: added interval, timeout
// v4: added table_version
// v5: added ipv6, re-ordered session structure
static int cluster_process_heartbeat(uint8_t *data, int size, int more, uint8_t *p, in_addr_t addr)
{
      heartt *h;
      int s = size - (p-data);
      int i, type;
      int hb_ver = more;

#if HB_VERSION != 5
# error "need to update cluster_process_heartbeat()"
#endif

      // we handle versions 3 through 5
      if (hb_ver < 3 || hb_ver > HB_VERSION) {
            LOG(0, 0, 0, "Received a heartbeat version that I don't support (%d)!\n", hb_ver);
            return -1; // Ignore it??
      }

      if (size > sizeof(past_hearts[0].data)) {
            LOG(0, 0, 0, "Received an oversize heartbeat from %s (%d)!\n", fmtaddr(addr, 0), size);
            return -1;
      }

      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, "I just got a heartbeat from master %s, but _I_ am the master!\n", fmtaddr(addr, 0));
            if (!h->basetime) {
                  LOG(0, 0, 0, "Heartbeat with zero basetime!  Ignoring\n");
                  return -1; // Skip it.
            }

            if (hb_ver >= 4) {
                  if (h->table_version > config->cluster_table_version) {
                        LOG(0, 0, 0, "They've seen more state changes (%" PRIu64 " vs my %" PRIu64 ") so I'm gone!\n",
                              h->table_version, config->cluster_table_version);

                        kill(0, SIGTERM);
                        exit(1);
                  }
                  if (h->table_version < config->cluster_table_version)
                        return -1;
            }

            if (basetime > h->basetime) {
                  LOG(0, 0, 0, "They're an older master than me so I'm gone!\n");
                  kill(0, SIGTERM);
                  exit(1);
            }

            if (basetime < h->basetime)
                  return -1;

            if (my_address < addr) { // Tie breaker.
                  LOG(0, 0, 0, "They're a higher IP address than me, so I'm gone!\n");
                  kill(0, SIGTERM);
                  exit(1);
            }

                  //
                  // Send it a unicast heartbeat to see give it a chance to die.
                  // NOTE: It's actually safe to do seq-number - 1 without checking
                  // for wrap around.
                  //
            cluster_catchup_slave(config->cluster_seq_number - 1, addr);

            return -1; // Skip it.
      }

            //
            // Try and guard against a stray master appearing.
            //
            // Ignore heartbeats received from another master before the
            // timeout (less a smidgen) for the old master has elapsed.
            //
            // Note that after a clean failover, the cluster_master_address
            // is cleared, so this doesn't run. 
            //
      if (config->cluster_master_address && addr != config->cluster_master_address) {
                LOG(0, 0, 0, "Ignoring stray heartbeat from %s, current master %s has not yet timed out (last heartbeat %.1f seconds ago).\n",
                      fmtaddr(addr, 0), fmtaddr(config->cluster_master_address, 1),
                      0.1 * (TIME - config->cluster_last_hb));
                return -1; // ignore
      }

      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!!
      config->cluster_last_hb_ver = hb_ver; // remember what cluster version the master is using

      if (config->cluster_seq_number != h->seq) {     // Out of sequence heartbeat!
            static int lastseen_seq = 0;
            static time_t lastseen_time = 0;

            // limit to once per second for a particular seq#
            int ask = (config->cluster_seq_number != lastseen_seq || time_now != lastseen_time);

            LOG(1, 0, 0, "HB: Got seq# %d but was expecting %d.  %s.\n",
                  h->seq, config->cluster_seq_number,
                  ask ? "Asking for resend" : "Ignoring");

            if (ask)
            {
                  lastseen_seq = config->cluster_seq_number;
                  lastseen_time = time_now;
                  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);

      if (h->interval != config->cluster_hb_interval)
      {
            LOG(2, 0, 0, "Master set ping/heartbeat interval to %u (was %u)\n",
                  h->interval, config->cluster_hb_interval);

            config->cluster_hb_interval = h->interval;
      }

      if (h->timeout != config->cluster_hb_timeout)
      {
            LOG(2, 0, 0, "Master set heartbeat timeout to %u (was %u)\n",
                  h->timeout, config->cluster_hb_timeout);

            config->cluster_hb_timeout = h->timeout;
      }

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

            type = *((uint32_t *) p);
            p += sizeof(uint32_t);
            s -= sizeof(uint32_t);

            more = *((uint32_t *) p);
            p += sizeof(uint32_t);
            s -= sizeof(uint32_t);

            switch (type) {
                  case C_CSESSION: { // Compressed session structure.
                        uint8_t c[ sizeof(sessiont) + 2];
                        int size;
                        uint8_t *orig_p = p;

                        size = rle_decompress((uint8_t **) &p, s, c, sizeof(c) );
                        s -= (p - orig_p);

                        // session struct changed with v5
                        if (hb_ver < 5)
                        {
                              if (size != sizeof(struct oldsession)) {
                                    LOG(0, 0, 0, "DANGER: Received a v%d CSESSION that didn't decompress correctly!\n", hb_ver);
                                          // Now what? Should exit! No-longer up to date!
                                    break;
                              }
                              cluster_recv_session(more, convert_session((struct oldsession *) c));
                              break;
                        }

                        if (size != sizeof(sessiont) ) { // Ouch! Very very bad!
                              LOG(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 (hb_ver < 5)
                        {
                              if (s < sizeof(struct oldsession))
                                    goto shortpacket;

                              cluster_recv_session(more, convert_session((struct oldsession *) p));

                              p += sizeof(struct oldsession);
                              s -= sizeof(struct oldsession);
                              break;
                        }

                        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.
                        uint8_t c[ sizeof(tunnelt) + 2];
                        int size;
                        uint8_t *orig_p = p;

                        size = rle_decompress((uint8_t **) &p, s, c, sizeof(c));
                        s -= (p - orig_p);

                        if (size != sizeof(tunnelt) ) { // Ouch! Very very bad!
                              LOG(0, 0, 0, "DANGER: Received a CTUNNEL 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, "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)
      {
            LOG(0, 0, 0, "My master just changed from %s to %s!\n",
                  fmtaddr(config->cluster_master_address, 0), fmtaddr(addr, 1));

            config->cluster_master_address = addr;
      }

      config->cluster_last_hb = TIME;     // Successfully received a heartbeat!
      config->cluster_table_version = h->table_version;
      return 0;

shortpacket:
      LOG(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(uint8_t *data, int size, in_addr_t addr)
{
      int type, more;
      uint8_t *p = data;
      int s = size;

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

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

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

      if (s < 8)
            goto shortpacket;

      type = *((uint32_t *) p);
      p += sizeof(uint32_t);
      s -= sizeof(uint32_t);

      more = *((uint32_t *) p);
      p += sizeof(uint32_t);
      s -= sizeof(uint32_t);

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

      case C_MASTER: // Our master is wrong
            return cluster_set_master(addr, more);

      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.
      case C_FORWARD_DAE: // Forwarded DAE packet. pass off to processdae.
            if (!config->cluster_iam_master)
            {
                  LOG(0, 0, 0, "I'm not the master, but I got a C_FORWARD_%s from %s?\n",
                        type == C_FORWARD_DAE ? "_DAE" : "", fmtaddr(addr, 0));

                  return -1;
            }
            else
            {
                  struct sockaddr_in a;
                  a.sin_addr.s_addr = more;

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

                  LOG(4, 0, 0, "Got a forwarded %spacket... (%s:%d)\n",
                        type == C_FORWARD_DAE ? "DAE " : "", fmtaddr(more, 0), a.sin_port);

                  STAT(recv_forward);
                  if (type == C_FORWARD_DAE)
                  {
                        struct in_addr local;
                        local.s_addr = config->bind_address ? config->bind_address : my_address;
                        processdae(p, s, &a, sizeof(a), &local);
                  }
                  else
                        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, "I'm not the master, but I got a C_THROTTLE from %s?\n", fmtaddr(addr, 0));
                  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, "I'm not the master, but I got a C_GARDEN from %s?\n", fmtaddr(addr, 0));
                  return -1;
            }

            tun_write(p, s);
            return 0;

      case C_BYTES:
            if (!config->cluster_iam_master) {
                  LOG(0, 0, 0, "I'm not the master, but I got a C_BYTES from %s?\n", fmtaddr(addr, 0));
                  return -1;
            }

            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, "_I_ am master, but I received a C_KILL from %s! (Seq# %d)\n", fmtaddr(addr, 0), more);
                  return -1;
            }
            if (more != config->cluster_seq_number) {
                  LOG(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, "Received a C_KILL from %s which doesn't match config->cluster_master_address (%s)\n",
                        fmtaddr(addr, 0), fmtaddr(config->cluster_master_address, 1));
                  // We can only warn about it. The master might really have switched!
            }

            LOG(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, "Got a heartbeat from %s\n", fmtaddr(addr, 0));
            return cluster_process_heartbeat(data, size, more, p, addr);

      default:
            LOG(0, 0, 0, "Strange type packet received on cluster socket (%d)\n", type);
            return -1;
      }
      return 0;

shortpacket:
      LOG(0, 0, 0, "I got a _short_ 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", fmtaddr(my_address, 0));
      cli_print(cli, "VIP address      : %s", fmtaddr(config->bind_address, 0));
      cli_print(cli, "Multicast address: %s", fmtaddr(config->cluster_address, 0));
      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
                        ? fmtaddr(config->cluster_master_address, 0)
                        : "Not defined",
                  0.1 * (TIME - config->cluster_last_hb));
            cli_print(cli, "Uptodate         : %s", config->cluster_iam_uptodate ? "Yes" : "No");
            cli_print(cli, "Table version #  : %" PRIu64, config->cluster_table_version);
            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, "Table version #  : %" PRIu64, config->cluster_table_version);
            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  %10u %8d", fmtaddr(peers[i].peer, 0),
                  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 )
static int rle_compress(uint8_t **src_p, int ssize, uint8_t *dst, int dsize)
{
      int count;
      int orig_dsize = dsize;
      uint8_t *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.
static int rle_decompress(uint8_t **src_p, int ssize, uint8_t *dst, int dsize)
{
      int count;
      int orig_dsize = dsize;
      uint8_t *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);
}

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