n2n/sn.c

/**
 * (C) 2007-18 - ntop.org and contributors
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not see see <http://www.gnu.org/licenses/>
 *
 */

/* Supernode for n2n-2.x */

#include "n2n.h"

#ifdef WIN32
#include <signal.h>
#endif

#define N2N_SN_LPORT_DEFAULT 7654
#define N2N_SN_PKTBUF_SIZE   2048

#define N2N_SN_MGMT_PORT                5645

typedef struct sn_stats {
  size_t errors;              /* Number of errors encountered. */
  size_t reg_super;           /* Number of REGISTER_SUPER requests received. */
  size_t reg_super_nak;       /* Number of REGISTER_SUPER requests declined. */
  size_t fwd;                 /* Number of messages forwarded. */
  size_t broadcast;           /* Number of messages broadcast to a community. */
  time_t last_fwd;            /* Time when last message was forwarded. */
  time_t last_reg_super;      /* Time when last REGISTER_SUPER was received. */
} sn_stats_t;

struct sn_community {
  char community[N2N_COMMUNITY_SIZE];
  struct peer_info *edges;          /* Link list of registered edges. */

  UT_hash_handle   hh; /* makes this structure hashable */
};

typedef struct n2n_sn {
  time_t              start_time;     /* Used to measure uptime. */
  sn_stats_t          stats;
  int                 daemon;         /* If non-zero then daemonise. */
  uint16_t            lport;          /* Local UDP port to bind to. */
  int                 sock;           /* Main socket for UDP traffic with edges. */
  int                 mgmt_sock;      /* management socket. */
  int 	              lock_communities; /* If true, only loaded communities can be used. */
  struct sn_community *communities;
} n2n_sn_t;

#define HASH_FIND_COMMUNITY(head,name,out) HASH_FIND_STR(head,name,out)

static int try_forward(n2n_sn_t * sss,
		       const n2n_common_t * cmn,
		       const n2n_mac_t dstMac,
		       const uint8_t * pktbuf,
		       size_t pktsize);

static int try_broadcast(n2n_sn_t * sss,
			 const n2n_common_t * cmn,
			 const n2n_mac_t srcMac,
			 const uint8_t * pktbuf,
			 size_t pktsize);

static n2n_sn_t sss_node;

/** Initialise the supernode structure */
static int init_sn(n2n_sn_t * sss) {
#ifdef WIN32
  initWin32();
#endif
  memset(sss, 0, sizeof(n2n_sn_t));

  sss->daemon = 1; /* By defult run as a daemon. */
  sss->lport = N2N_SN_LPORT_DEFAULT;
  sss->sock = -1;
  sss->mgmt_sock = -1;

  return 0; /* OK */
}

/** Deinitialise the supernode structure and deallocate any memory owned by
 *  it. */
static void deinit_sn(n2n_sn_t * sss)
{
  struct sn_community *community, *tmp;

  if(sss->sock >= 0)
    {
      closesocket(sss->sock);
    }
  sss->sock=-1;

  if(sss->mgmt_sock >= 0)
    {
      closesocket(sss->mgmt_sock);
    }
  sss->mgmt_sock=-1;

  HASH_ITER(hh, sss->communities, community, tmp) {
    clear_peer_list(&community->edges);
    HASH_DEL(sss->communities, community);
    free(community);
  }
}


/** Determine the appropriate lifetime for new registrations.
 *
 *  If the supernode has been put into a pre-shutdown phase then this lifetime
 *  should not allow registrations to continue beyond the shutdown point.
 */
static uint16_t reg_lifetime(n2n_sn_t * sss) {
  /* NOTE: UDP firewalls usually have a 30 seconds timeout */
  return 15;
}


/** Update the edge table with the details of the edge which contacted the
 *  supernode. */
static int update_edge(n2n_sn_t * sss,
		       const n2n_mac_t edgeMac,
		       struct sn_community *comm,
		       const n2n_sock_t * sender_sock,
		       time_t now) {
  macstr_t            mac_buf;
  n2n_sock_str_t      sockbuf;
  struct peer_info *  scan;

  traceEvent(TRACE_DEBUG, "update_edge for %s [%s]",
	     macaddr_str(mac_buf, edgeMac),
	     sock_to_cstr(sockbuf, sender_sock));

  HASH_FIND_PEER(comm->edges, edgeMac, scan);

  if(NULL == scan) {
      /* Not known */

      scan = (struct peer_info*)calloc(1, sizeof(struct peer_info)); /* deallocated in purge_expired_registrations */

      memcpy(scan->community_name, comm->community, sizeof(n2n_community_t));
      memcpy(&(scan->mac_addr), edgeMac, sizeof(n2n_mac_t));
      memcpy(&(scan->sock), sender_sock, sizeof(n2n_sock_t));

      HASH_ADD_PEER(comm->edges, scan);

      traceEvent(TRACE_INFO, "update_edge created   %s ==> %s",
		 macaddr_str(mac_buf, edgeMac),
		 sock_to_cstr(sockbuf, sender_sock));
    } else  {
      /* Known */
      if((0 != memcmp(comm, scan->community_name, sizeof(n2n_community_t))) ||
	 (!sock_equal(sender_sock, &(scan->sock))))
        {
	  memcpy(scan->community_name, comm, sizeof(n2n_community_t));
	  memcpy(&(scan->sock), sender_sock, sizeof(n2n_sock_t));

	  traceEvent(TRACE_INFO, "update_edge updated   %s ==> %s",
		     macaddr_str(mac_buf, edgeMac),
		     sock_to_cstr(sockbuf, sender_sock));
        }
      else
        {
	  traceEvent(TRACE_DEBUG, "update_edge unchanged %s ==> %s",
		     macaddr_str(mac_buf, edgeMac),
		     sock_to_cstr(sockbuf, sender_sock));
        }

    }

  scan->last_seen = now;
  return 0;
}


/** Send a datagram to the destination embodied in a n2n_sock_t.
 *
 *  @return -1 on error otherwise number of bytes sent
 */
static ssize_t sendto_sock(n2n_sn_t * sss,
                           const n2n_sock_t * sock,
                           const uint8_t * pktbuf,
                           size_t pktsize)
{
  n2n_sock_str_t      sockbuf;

  if(AF_INET == sock->family)
    {
      struct sockaddr_in udpsock;

      udpsock.sin_family = AF_INET;
      udpsock.sin_port = htons(sock->port);
      memcpy(&(udpsock.sin_addr.s_addr), &(sock->addr.v4), IPV4_SIZE);

      traceEvent(TRACE_DEBUG, "sendto_sock %lu to [%s]",
		 pktsize,
		 sock_to_cstr(sockbuf, sock));

      return sendto(sss->sock, pktbuf, pktsize, 0,
		    (const struct sockaddr *)&udpsock, sizeof(struct sockaddr_in));
    }
  else
    {
      /* AF_INET6 not implemented */
      errno = EAFNOSUPPORT;
      return -1;
    }
}

static int try_forward(n2n_sn_t * sss,
		       const n2n_common_t * cmn,
		       const n2n_mac_t dstMac,
		       const uint8_t * pktbuf,
		       size_t pktsize)
{
  struct peer_info *  scan;
  struct sn_community *community;
  macstr_t            mac_buf;
  n2n_sock_str_t      sockbuf;

  HASH_FIND_COMMUNITY(sss->communities, (char*)cmn->community, community);

  if(!community) {
    traceEvent(TRACE_DEBUG, "try_forward unknown community %s", cmn->community);
    return(-1);
  }

  HASH_FIND_PEER(community->edges, dstMac, scan);

  if(NULL != scan)
    {
      int data_sent_len;
      data_sent_len = sendto_sock(sss, &(scan->sock), pktbuf, pktsize);

      if(data_sent_len == pktsize)
        {
	  ++(sss->stats.fwd);
	  traceEvent(TRACE_DEBUG, "unicast %lu to [%s] %s",
		     pktsize,
		     sock_to_cstr(sockbuf, &(scan->sock)),
		     macaddr_str(mac_buf, scan->mac_addr));
        }
      else
        {
	  ++(sss->stats.errors);
	  traceEvent(TRACE_ERROR, "unicast %lu to [%s] %s FAILED (%d: %s)",
		     pktsize,
		     sock_to_cstr(sockbuf, &(scan->sock)),
		     macaddr_str(mac_buf, scan->mac_addr),
		     errno, strerror(errno));
        }
    }
  else
    {
      traceEvent(TRACE_DEBUG, "try_forward unknown MAC");

      /* Not a known MAC so drop. */
      return(-2);
    }

  return(0);
}


/** Try and broadcast a message to all edges in the community.
 *
 *  This will send the exact same datagram to zero or more edges registered to
 *  the supernode.
 */
static int try_broadcast(n2n_sn_t * sss,
			 const n2n_common_t * cmn,
			 const n2n_mac_t srcMac,
			 const uint8_t * pktbuf,
			 size_t pktsize)
{
  struct peer_info *scan, *tmp;
  struct sn_community *community;
  macstr_t            mac_buf;
  n2n_sock_str_t      sockbuf;

  traceEvent(TRACE_DEBUG, "try_broadcast");

  HASH_FIND_COMMUNITY(sss->communities, (char*)cmn->community, community);

  if(community) {
    HASH_ITER(hh, community->edges, scan, tmp) {
      if(memcmp(srcMac, scan->mac_addr, sizeof(n2n_mac_t)) != 0) {
	  /* REVISIT: exclude if the destination socket is where the packet came from. */
	  int data_sent_len;

	  data_sent_len = sendto_sock(sss, &(scan->sock), pktbuf, pktsize);

	  if(data_sent_len != pktsize)
            {
	      ++(sss->stats.errors);
	      traceEvent(TRACE_WARNING, "multicast %lu to [%s] %s failed %s",
			 pktsize,
			 sock_to_cstr(sockbuf, &(scan->sock)),
			 macaddr_str(mac_buf, scan->mac_addr),
			 strerror(errno));
            }
	  else
            {
	      ++(sss->stats.broadcast);
	      traceEvent(TRACE_DEBUG, "multicast %lu to [%s] %s",
			 pktsize,
			 sock_to_cstr(sockbuf, &(scan->sock)),
			 macaddr_str(mac_buf, scan->mac_addr));
            }
      }
    }
  } else
    traceEvent(TRACE_INFO, "ignoring broadcast on unknown community %s\n",
      cmn->community);

  return 0;
}


static int process_mgmt(n2n_sn_t * sss,
			const struct sockaddr_in * sender_sock,
			const uint8_t * mgmt_buf,
			size_t mgmt_size,
			time_t now)
{
  char resbuf[N2N_SN_PKTBUF_SIZE];
  size_t ressize=0;
  uint num_edges=0;
  ssize_t r;
  struct sn_community *community, *tmp;

  traceEvent(TRACE_DEBUG, "process_mgmt");

  ressize += snprintf(resbuf+ressize, N2N_SN_PKTBUF_SIZE-ressize,
		      "----------------\n");

  ressize += snprintf(resbuf+ressize, N2N_SN_PKTBUF_SIZE-ressize,
		      "uptime    %lu\n", (now - sss->start_time));

  HASH_ITER(hh, sss->communities, community, tmp) {
    num_edges += HASH_COUNT(community->edges);
  }

  ressize += snprintf(resbuf+ressize, N2N_SN_PKTBUF_SIZE-ressize,
		      "edges     %u\n",
		      num_edges);

  ressize += snprintf(resbuf+ressize, N2N_SN_PKTBUF_SIZE-ressize,
		      "errors    %u\n",
		      (unsigned int)sss->stats.errors);

  ressize += snprintf(resbuf+ressize, N2N_SN_PKTBUF_SIZE-ressize,
		      "reg_sup   %u\n",
		      (unsigned int)sss->stats.reg_super);

  ressize += snprintf(resbuf+ressize, N2N_SN_PKTBUF_SIZE-ressize,
		      "reg_nak   %u\n",
		      (unsigned int)sss->stats.reg_super_nak);

  ressize += snprintf(resbuf+ressize, N2N_SN_PKTBUF_SIZE-ressize,
		      "fwd       %u\n",
		      (unsigned int) sss->stats.fwd);

  ressize += snprintf(resbuf+ressize, N2N_SN_PKTBUF_SIZE-ressize,
		      "broadcast %u\n",
		      (unsigned int) sss->stats.broadcast);

  ressize += snprintf(resbuf+ressize, N2N_SN_PKTBUF_SIZE-ressize,
		      "last fwd  %lu sec ago\n",
		      (long unsigned int)(now - sss->stats.last_fwd));

  ressize += snprintf(resbuf+ressize, N2N_SN_PKTBUF_SIZE-ressize,
		      "last reg  %lu sec ago\n",
		      (long unsigned int) (now - sss->stats.last_reg_super));


  r = sendto(sss->mgmt_sock, resbuf, ressize, 0/*flags*/,
	     (struct sockaddr *)sender_sock, sizeof(struct sockaddr_in));

  if(r <= 0)
    {
      ++(sss->stats.errors);
      traceEvent(TRACE_ERROR, "process_mgmt : sendto failed. %s", strerror(errno));
    }

  return 0;
}

/** Load the list of allowed communities. Existing/previous ones will be removed
 *
 */
static int load_allowed_sn_community(n2n_sn_t *sss, char *path) {
  char buffer[4096], *line;
  FILE *fd = fopen(path, "r");
  struct sn_community *s, *tmp;
  uint32_t num_communities = 0;

  if(fd == NULL) {
    traceEvent(TRACE_WARNING, "File %s not found", path);
    return -1;
  }

  HASH_ITER(hh, sss->communities, s, tmp) {
    HASH_DEL(sss->communities, s);
    free(s);
  }

  while((line = fgets(buffer, sizeof(buffer), fd)) != NULL) {
    int len = strlen(line);

    if((len < 2) || line[0] == '#')
      continue;

    len--;
    while(len > 0) {
      if((line[len] == '\n') || (line[len] == '\r')) {
	line[len] = '\0';
	len--;
      } else
	break;
    }

    s = (struct sn_community*)calloc(1,sizeof(struct sn_community));

    if(s != NULL) {
      strncpy((char*)s->community, line, N2N_COMMUNITY_SIZE-1);
      s->community[N2N_COMMUNITY_SIZE-1] = '\0';
      HASH_ADD_STR(sss->communities, community, s);
      num_communities++;
      traceEvent(TRACE_INFO, "Added allowed community '%s' [total: %u]",
		 (char*)s->community, num_communities);
    }
  }

  fclose(fd);

  traceEvent(TRACE_NORMAL, "Loaded %u communities from %s",
	     num_communities, path);

  /* No new communities will be allowed */
  sss->lock_communities = 1;

  return(0);
}

/** Examine a datagram and determine what to do with it.
 *
 */
static int process_udp(n2n_sn_t * sss,
		       const struct sockaddr_in * sender_sock,
		       const uint8_t * udp_buf,
		       size_t udp_size,
		       time_t now)
{
  n2n_common_t        cmn; /* common fields in the packet header */
  size_t              rem;
  size_t              idx;
  size_t              msg_type;
  uint8_t             from_supernode;
  macstr_t            mac_buf;
  macstr_t            mac_buf2;
  n2n_sock_str_t      sockbuf;
  char                buf[32];

  traceEvent(TRACE_DEBUG, "Processing incoming UDP packet [len: %lu][sender: %s:%u]",
	     udp_size, intoa(ntohl(sender_sock->sin_addr.s_addr), buf, sizeof(buf)),
	     ntohs(sender_sock->sin_port));

  /* Use decode_common() to determine the kind of packet then process it:
   *
   * REGISTER_SUPER adds an edge and generate a return REGISTER_SUPER_ACK
   *
   * REGISTER, REGISTER_ACK and PACKET messages are forwarded to their
   * destination edge. If the destination is not known then PACKETs are
   * broadcast.
   */

  rem = udp_size; /* Counts down bytes of packet to protect against buffer overruns. */
  idx = 0; /* marches through packet header as parts are decoded. */
  if(decode_common(&cmn, udp_buf, &rem, &idx) < 0) {
    traceEvent(TRACE_ERROR, "Failed to decode common section");
    return -1; /* failed to decode packet */
  }

  msg_type = cmn.pc; /* packet code */
  from_supernode= cmn.flags & N2N_FLAGS_FROM_SUPERNODE;

  if(cmn.ttl < 1) {
    traceEvent(TRACE_WARNING, "Expired TTL");
    return 0; /* Don't process further */
  }

  --(cmn.ttl); /* The value copied into all forwarded packets. */

  switch(msg_type) {
  case MSG_TYPE_PACKET:
  {
    /* PACKET from one edge to another edge via supernode. */

    /* pkt will be modified in place and recoded to an output of potentially
     * different size due to addition of the socket.*/
    n2n_PACKET_t                    pkt;
    n2n_common_t                    cmn2;
    uint8_t                         encbuf[N2N_SN_PKTBUF_SIZE];
    size_t                          encx=0;
    int                             unicast; /* non-zero if unicast */
    const uint8_t *                 rec_buf; /* either udp_buf or encbuf */


    sss->stats.last_fwd=now;
    decode_PACKET(&pkt, &cmn, udp_buf, &rem, &idx);

    unicast = (0 == is_multi_broadcast(pkt.dstMac));

    traceEvent(TRACE_DEBUG, "RX PACKET (%s) %s -> %s %s",
	       (unicast?"unicast":"multicast"),
	       macaddr_str(mac_buf, pkt.srcMac),
	       macaddr_str(mac_buf2, pkt.dstMac),
	       (from_supernode?"from sn":"local"));

    if(!from_supernode) {
      memcpy(&cmn2, &cmn, sizeof(n2n_common_t));

      /* We are going to add socket even if it was not there before */
      cmn2.flags |= N2N_FLAGS_SOCKET | N2N_FLAGS_FROM_SUPERNODE;

      pkt.sock.family = AF_INET;
      pkt.sock.port = ntohs(sender_sock->sin_port);
      memcpy(pkt.sock.addr.v4, &(sender_sock->sin_addr.s_addr), IPV4_SIZE);

      rec_buf = encbuf;

      /* Re-encode the header. */
      encode_PACKET(encbuf, &encx, &cmn2, &pkt);

      /* Copy the original payload unchanged */
      encode_buf(encbuf, &encx, (udp_buf + idx), (udp_size - idx));
    } else {
      /* Already from a supernode. Nothing to modify, just pass to
       * destination. */

      traceEvent(TRACE_DEBUG, "Rx PACKET fwd unmodified");

      rec_buf = udp_buf;
      encx = udp_size;
    }

    /* Common section to forward the final product. */
    if(unicast)
      try_forward(sss, &cmn, pkt.dstMac, rec_buf, encx);
    else
      try_broadcast(sss, &cmn, pkt.srcMac, rec_buf, encx);
    break;
  }
  case MSG_TYPE_REGISTER:
  {
    /* Forwarding a REGISTER from one edge to the next */

    n2n_REGISTER_t                  reg;
    n2n_common_t                    cmn2;
    uint8_t                         encbuf[N2N_SN_PKTBUF_SIZE];
    size_t                          encx=0;
    int                             unicast; /* non-zero if unicast */
    const uint8_t *                 rec_buf; /* either udp_buf or encbuf */

    sss->stats.last_fwd=now;
    decode_REGISTER(&reg, &cmn, udp_buf, &rem, &idx);

    unicast = (0 == is_multi_broadcast(reg.dstMac));

    if(unicast) {
      traceEvent(TRACE_DEBUG, "Rx REGISTER %s -> %s %s",
		 macaddr_str(mac_buf, reg.srcMac),
		 macaddr_str(mac_buf2, reg.dstMac),
		 ((cmn.flags & N2N_FLAGS_FROM_SUPERNODE)?"from sn":"local"));

      if(0 == (cmn.flags & N2N_FLAGS_FROM_SUPERNODE)) {
	memcpy(&cmn2, &cmn, sizeof(n2n_common_t));

	/* We are going to add socket even if it was not there before */
	cmn2.flags |= N2N_FLAGS_SOCKET | N2N_FLAGS_FROM_SUPERNODE;

	reg.sock.family = AF_INET;
	reg.sock.port = ntohs(sender_sock->sin_port);
	memcpy(reg.sock.addr.v4, &(sender_sock->sin_addr.s_addr), IPV4_SIZE);

	rec_buf = encbuf;

	/* Re-encode the header. */
	encode_REGISTER(encbuf, &encx, &cmn2, &reg);

	/* Copy the original payload unchanged */
	encode_buf(encbuf, &encx, (udp_buf + idx), (udp_size - idx));
      } else {
	/* Already from a supernode. Nothing to modify, just pass to
	 * destination. */

	rec_buf = udp_buf;
	encx = udp_size;
      }

      try_forward(sss, &cmn, reg.dstMac, rec_buf, encx); /* unicast only */
    } else
      traceEvent(TRACE_ERROR, "Rx REGISTER with multicast destination");
    break;
  }
  case MSG_TYPE_REGISTER_ACK:
    traceEvent(TRACE_DEBUG, "Rx REGISTER_ACK (NOT IMPLEMENTED) SHould not be via supernode");
    break;
  case MSG_TYPE_REGISTER_SUPER:
  {
    n2n_REGISTER_SUPER_t            reg;
    n2n_REGISTER_SUPER_ACK_t        ack;
    n2n_common_t                    cmn2;
    uint8_t                         ackbuf[N2N_SN_PKTBUF_SIZE];
    size_t                          encx=0;
    struct sn_community          *comm;

    /* Edge requesting registration with us.  */
    sss->stats.last_reg_super=now;
    ++(sss->stats.reg_super);
    decode_REGISTER_SUPER(&reg, &cmn, udp_buf, &rem, &idx);

    HASH_FIND_COMMUNITY(sss->communities, (char*)cmn.community, comm);

    /*
      Before we move any further, we need to check if the requested
      community is allowed by the supernode. In case it is not we do
      not report any message back to the edge to hide the supernode
      existance (better from the security standpoint)
    */
    if(!comm && !sss->lock_communities) {
      comm = calloc(1, sizeof(struct sn_community));

      if(comm) {
	strncpy(comm->community, (char*)cmn.community, N2N_COMMUNITY_SIZE-1);
	comm->community[N2N_COMMUNITY_SIZE-1] = '\0';
	HASH_ADD_STR(sss->communities, community, comm);

	traceEvent(TRACE_INFO, "New community: %s", comm->community);
      }
    }

    if(comm) {
      cmn2.ttl = N2N_DEFAULT_TTL;
      cmn2.pc = n2n_register_super_ack;
      cmn2.flags = N2N_FLAGS_SOCKET | N2N_FLAGS_FROM_SUPERNODE;
      memcpy(cmn2.community, cmn.community, sizeof(n2n_community_t));

      memcpy(&(ack.cookie), &(reg.cookie), sizeof(n2n_cookie_t));
      memcpy(ack.edgeMac, reg.edgeMac, sizeof(n2n_mac_t));
      ack.lifetime = reg_lifetime(sss);

      ack.sock.family = AF_INET;
      ack.sock.port = ntohs(sender_sock->sin_port);
      memcpy(ack.sock.addr.v4, &(sender_sock->sin_addr.s_addr), IPV4_SIZE);

      ack.num_sn=0; /* No backup */
      memset(&(ack.sn_bak), 0, sizeof(n2n_sock_t));

      traceEvent(TRACE_DEBUG, "Rx REGISTER_SUPER for %s [%s]",
		 macaddr_str(mac_buf, reg.edgeMac),
		 sock_to_cstr(sockbuf, &(ack.sock)));

      update_edge(sss, reg.edgeMac, comm, &(ack.sock), now);

      encode_REGISTER_SUPER_ACK(ackbuf, &encx, &cmn2, &ack);

      sendto(sss->sock, ackbuf, encx, 0,
	     (struct sockaddr *)sender_sock, sizeof(struct sockaddr_in));

      traceEvent(TRACE_DEBUG, "Tx REGISTER_SUPER_ACK for %s [%s]",
		 macaddr_str(mac_buf, reg.edgeMac),
		 sock_to_cstr(sockbuf, &(ack.sock)));
    } else
      traceEvent(TRACE_INFO, "Discarded registration: unallowed community '%s'",
		 (char*)cmn.community);
    break;
  } case MSG_TYPE_QUERY_PEER: {
    n2n_QUERY_PEER_t query;
    uint8_t encbuf[N2N_SN_PKTBUF_SIZE];
    size_t encx=0;
    n2n_common_t cmn2;
    n2n_PEER_INFO_t pi;
    struct sn_community *community;

    decode_QUERY_PEER( &query, &cmn, udp_buf, &rem, &idx );

    traceEvent( TRACE_DEBUG, "Rx QUERY_PEER from %s for %s",
                macaddr_str( mac_buf,  query.srcMac ),
                macaddr_str( mac_buf2, query.targetMac ) );

    HASH_FIND_COMMUNITY(sss->communities, (char*)cmn.community, community);

    if(community) {
      struct peer_info *scan;
      HASH_FIND_PEER(community->edges, query.targetMac, scan);

      if (scan) {
	  cmn2.ttl = N2N_DEFAULT_TTL;
	  cmn2.pc = n2n_peer_info;
	  cmn2.flags = N2N_FLAGS_FROM_SUPERNODE;
	  memcpy( cmn2.community, cmn.community, sizeof(n2n_community_t) );

	  pi.aflags = 0;
	  memcpy( pi.mac, query.targetMac, sizeof(n2n_mac_t) );
	  pi.sock = scan->sock;

	  encode_PEER_INFO( encbuf, &encx, &cmn2, &pi );

	  sendto( sss->sock, encbuf, encx, 0,
		  (struct sockaddr *)sender_sock, sizeof(struct sockaddr_in) );

	  traceEvent( TRACE_DEBUG, "Tx PEER_INFO to %s",
		      macaddr_str( mac_buf, query.srcMac ) );
      } else {
	  traceEvent( TRACE_DEBUG, "Ignoring QUERY_PEER for unknown edge %s",
		      macaddr_str( mac_buf, query.targetMac ) );
      }
    }

    break;
  }
  default:
    /* Not a known message type */
    traceEvent(TRACE_WARNING, "Unable to handle packet type %d: ignored", (signed int)msg_type);
  } /* switch(msg_type) */

  return 0;
}

/* *************************************************** */

/** Help message to print if the command line arguments are not valid. */
static void help() {
  print_n2n_version();

  printf("supernode <config file> (see supernode.conf)\n"
	 "or\n"
	 );
  printf("supernode ");
  printf("-l <lport> ");
  printf("-c <path> ");
  printf("[-f] ");
  printf("[-v] ");
  printf("\n\n");

  printf("-l <lport>\tSet UDP main listen port to <lport>\n");
  printf("-c <path>\tFile containing the allowed communities.\n");
#if defined(N2N_HAVE_DAEMON)
  printf("-f        \tRun in foreground.\n");
#endif /* #if defined(N2N_HAVE_DAEMON) */
  printf("-v        \tIncrease verbosity. Can be used multiple times.\n");
  printf("-h        \tThis help message.\n");
  printf("\n");

  exit(1);
}

/* *************************************************** */

static int run_loop(n2n_sn_t * sss);

/* *************************************************** */

static int setOption(int optkey, char *_optarg, n2n_sn_t *sss) {
  //traceEvent(TRACE_NORMAL, "Option %c = %s", optkey, _optarg ? _optarg : "");

  switch(optkey) {
  case 'l': /* local-port */
    sss->lport = atoi(_optarg);
    break;

  case 'c': /* community file */
    load_allowed_sn_community(sss, optarg);
    break;

  case 'f': /* foreground */
    sss->daemon = 0;
    break;

  case 'h': /* help */
    help();
    break;

  case 'v': /* verbose */
    setTraceLevel(4); /* DEBUG */
    break;

  default:
    traceEvent(TRACE_WARNING, "Unknown option -%c: Ignored.", (char)optkey);
    return(-1);
  }

  return(0);
}

/* *********************************************** */

static const struct option long_options[] = {
  { "communities",     required_argument, NULL, 'c' },
  { "foreground",      no_argument,       NULL, 'f' },
  { "local-port",      required_argument, NULL, 'l' },
  { "help"   ,         no_argument,       NULL, 'h' },
  { "verbose",         no_argument,       NULL, 'v' },
  { NULL,              0,                 NULL,  0  }
};

/* *************************************************** */

/* read command line options */
static int loadFromCLI(int argc, char * const argv[], n2n_sn_t *sss) {
  u_char c;

  while((c = getopt_long(argc, argv, "fl:c:vh",
			 long_options, NULL)) != '?') {
    if(c == 255) break;
    setOption(c, optarg, sss);
  }

  return 0;
}

/* *************************************************** */

static char *trim(char *s) {
  char *end;

  while(isspace(s[0]) || (s[0] == '"') || (s[0] == '\''))
    s++;

  if(s[0] == 0) return s;

  end = &s[strlen(s) - 1];
  while(end > s
	&& (isspace(end[0])|| (end[0] == '"') || (end[0] == '\'')))
    end--;
  end[1] = 0;

  return s;
}

/* *************************************************** */

/* parse the configuration file */
static int loadFromFile(const char *path, n2n_sn_t *sss) {
  char buffer[4096], *line, *key, *value;
  u_int line_len, opt_name_len;
  FILE *fd;
  const struct option *opt;

  fd = fopen(path, "r");

  if(fd == NULL) {
    traceEvent(TRACE_WARNING, "Config file %s not found", path);
    return -1;
  }

  while((line = fgets(buffer, sizeof(buffer), fd)) != NULL) {

    line = trim(line);
    value = NULL;

    if((line_len = strlen(line)) < 2 || line[0] == '#')
      continue;

    if(!strncmp(line, "--", 2)) { /* long opt */
      key = &line[2], line_len -= 2;

      opt = long_options;
      while(opt->name != NULL) {
	opt_name_len = strlen(opt->name);

	if(!strncmp(key, opt->name, opt_name_len)
	   && (line_len <= opt_name_len
	       || key[opt_name_len] == '\0'
	       || key[opt_name_len] == ' '
	       || key[opt_name_len] == '=')) {
	  if(line_len > opt_name_len)	  key[opt_name_len] = '\0';
	  if(line_len > opt_name_len + 1) value = trim(&key[opt_name_len + 1]);

	  // traceEvent(TRACE_NORMAL, "long key: %s value: %s", key, value);
	  setOption(opt->val, value, sss);
	  break;
	}

	opt++;
      }
    } else if(line[0] == '-') { /* short opt */
      key = &line[1], line_len--;
      if(line_len > 1) key[1] = '\0';
      if(line_len > 2) value = trim(&key[2]);

      // traceEvent(TRACE_NORMAL, "key: %c value: %s", key[0], value);
      setOption(key[0], value, sss);
    } else {
      traceEvent(TRACE_WARNING, "Skipping unrecognized line: %s", line);
      continue;
    }
  }

  fclose(fd);

  return 0;
}

/* *************************************************** */

static void dump_registrations(int signo) {
  struct sn_community *comm, *ctmp;
  struct peer_info *list, *tmp;
  char buf[32];
  time_t now = time(NULL);
  u_int num = 0;

  traceEvent(TRACE_NORMAL, "====================================");

  HASH_ITER(hh, sss_node.communities, comm, ctmp) {
    HASH_ITER(hh, comm->edges, list, tmp) {
      if(list->sock.family == AF_INET)
	traceEvent(TRACE_NORMAL, "[id: %u][MAC: %s][edge: %u.%u.%u.%u:%u][community: %s][last seen: %u sec ago]",
		   ++num, macaddr_str(buf, list->mac_addr),
		   list->sock.addr.v4[0], list->sock.addr.v4[1], list->sock.addr.v4[2], list->sock.addr.v4[3],
		   list->sock.port,
		   (char*)list->community_name,
		   now-list->last_seen);
      else
	traceEvent(TRACE_NORMAL, "[id: %u][MAC: %s][edge: IPv6:%u][community: %s][last seen: %u sec ago]",
		   ++num, macaddr_str(buf, list->mac_addr), list->sock.port,
		   (char*)list->community_name,
		   now-list->last_seen);
    }
  }

  traceEvent(TRACE_NORMAL, "====================================");
}

/* *************************************************** */

static int keep_running;

#ifdef __linux__

static void term_handler(int sig) {
  static int called = 0;

  if(called) {
    traceEvent(TRACE_NORMAL, "Ok I am leaving now");
    _exit(0);
  } else {
    traceEvent(TRACE_NORMAL, "Shutting down...");
    called = 1;
  }

  keep_running = 0;
}
#endif

/* *************************************************** */

/** Main program entry point from kernel. */
int main(int argc, char * const argv[]) {
  int rc;

  if(argc == 1)
    help();

  init_sn(&sss_node);

#ifndef WIN32
  if((argc >= 2) && (argv[1][0] != '-')) {
    rc = loadFromFile(argv[1], &sss_node);
    if(argc > 2)
      rc = loadFromCLI(argc, argv, &sss_node);
  } else
#endif
    rc = loadFromCLI(argc, argv, &sss_node);

  if(rc < 0)
    return(-1);

#if defined(N2N_HAVE_DAEMON)
  if(sss_node.daemon) {
    useSyslog=1; /* traceEvent output now goes to syslog. */

    if(-1 == daemon(0, 0)) {
      traceEvent(TRACE_ERROR, "Failed to become daemon.");
      exit(-5);
    }
  }
#endif /* #if defined(N2N_HAVE_DAEMON) */

  traceEvent(TRACE_DEBUG, "traceLevel is %d", getTraceLevel());

  sss_node.sock = open_socket(sss_node.lport, 1 /*bind ANY*/);
  if(-1 == sss_node.sock) {
    traceEvent(TRACE_ERROR, "Failed to open main socket. %s", strerror(errno));
    exit(-2);
  } else {
    traceEvent(TRACE_NORMAL, "supernode is listening on UDP %u (main)", sss_node.lport);
  }

  sss_node.mgmt_sock = open_socket(N2N_SN_MGMT_PORT, 0 /* bind LOOPBACK */);
  if(-1 == sss_node.mgmt_sock) {
    traceEvent(TRACE_ERROR, "Failed to open management socket. %s", strerror(errno));
    exit(-2);
  } else
    traceEvent(TRACE_NORMAL, "supernode is listening on UDP %u (management)", N2N_SN_MGMT_PORT);

  traceEvent(TRACE_NORMAL, "supernode started");

#ifdef __linux__
  signal(SIGTERM, term_handler);
  signal(SIGINT, term_handler);
  signal(SIGHUP, dump_registrations);
#endif

  keep_running = 1;
  return run_loop(&sss_node);
}


/** Long lived processing entry point. Split out from main to simply
 *  daemonisation on some platforms. */
static int run_loop(n2n_sn_t * sss) {
  uint8_t pktbuf[N2N_SN_PKTBUF_SIZE];
  time_t last_purge_edges = 0;
  struct sn_community *comm, *tmp;

  sss->start_time = time(NULL);

  while(keep_running) {
    int rc;
    ssize_t bread;
    int max_sock;
    fd_set socket_mask;
    struct timeval wait_time;
    time_t now=0;

    FD_ZERO(&socket_mask);
    max_sock = MAX(sss->sock, sss->mgmt_sock);

    FD_SET(sss->sock, &socket_mask);
    FD_SET(sss->mgmt_sock, &socket_mask);

    wait_time.tv_sec = 10; wait_time.tv_usec = 0;
    rc = select(max_sock+1, &socket_mask, NULL, NULL, &wait_time);

    now = time(NULL);

    if(rc > 0) {
      if(FD_ISSET(sss->sock, &socket_mask)) {
	struct sockaddr_in  sender_sock;
	socklen_t           i;

	i = sizeof(sender_sock);
	bread = recvfrom(sss->sock, pktbuf, N2N_SN_PKTBUF_SIZE, 0/*flags*/,
			 (struct sockaddr *)&sender_sock, (socklen_t*)&i);

	if((bread < 0)
#ifdef WIN32
	   && (WSAGetLastError() != WSAECONNRESET)
#endif
	) {
	  /* For UDP bread of zero just means no data (unlike TCP). */
	  /* The fd is no good now. Maybe we lost our interface. */
	  traceEvent(TRACE_ERROR, "recvfrom() failed %d errno %d (%s)", bread, errno, strerror(errno));
#ifdef WIN32
	  traceEvent(TRACE_ERROR, "WSAGetLastError(): %u", WSAGetLastError());
#endif
	  keep_running=0;
	  break;
	}

	/* We have a datagram to process */
	if(bread > 0) {
	  /* And the datagram has data (not just a header) */
	  process_udp(sss, &sender_sock, pktbuf, bread, now);
	}
      }

      if(FD_ISSET(sss->mgmt_sock, &socket_mask)) {
	struct sockaddr_in  sender_sock;
	size_t              i;

	i = sizeof(sender_sock);
	bread = recvfrom(sss->mgmt_sock, pktbuf, N2N_SN_PKTBUF_SIZE, 0/*flags*/,
			 (struct sockaddr *)&sender_sock, (socklen_t*)&i);

	if(bread <= 0) {
	  traceEvent(TRACE_ERROR, "recvfrom() failed %d errno %d (%s)", bread, errno, strerror(errno));
	  keep_running=0;
	  break;
	}

	/* We have a datagram to process */
	process_mgmt(sss, &sender_sock, pktbuf, bread, now);
      }
    } else {
      traceEvent(TRACE_DEBUG, "timeout");
    }

    HASH_ITER(hh, sss->communities, comm, tmp) {
      purge_expired_registrations( &comm->edges, &last_purge_edges );

      if(comm->edges == NULL) {
	traceEvent(TRACE_INFO, "Purging idle community %s", comm->community);
	HASH_DEL(sss->communities, comm);
	free(comm);
      }
    }

  } /* while */

  deinit_sn(sss);

  return 0;
}