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      Packet::free(p.pkt);  // pkt is a route request we've already processed
      p.pkt = 0;
      return; // drop silently
    }
  
  // we're going to process this request now, so record the req_num
  request_table.insert(p.src, p.src, srh->rtreq_seq());

  /*  - if it's a Ring 0 search, check the rt$ for a reply and use it if
     possible.  There's not much point in doing Ring 0 search if you're 
     not going to check the cache.  See the comment about turning off all
     reply from cache behavior near the definition of d_r_f_c_o_p (if your 
     workload had really good spatial locality, it might still make 
     sense 'cause your target is probably sitting next to you)
      - if reply from cache is on, check the cache and reply if possible
      - otherwise, just propagate if possible. */
  if ((srh->max_propagation() == 0 || dsragent_reply_from_cache_on_propagating)
      && replyFromRouteCache(p))
	  return;			// all done

  // does the orginator want us to propagate?
  if (p.route.length() > srh->max_propagation())
    { 	// no propagation
      if (verbose_srr) 
        trace("SRR %.5f _%s_ dropped %s #%d (prop limit exceeded)",
              Scheduler::instance().clock(), net_id.dump(), p.src.dump(),
              srh->rtreq_seq());
      Packet::free(p.pkt); // pkt isn't for us, and isn't data carrying
      p.pkt = 0;
      return;		
    }

  // can we propagate?
  if (p.route.full())
    { 	// no propagation
      trace("SRR %.5f _%s_ dropped %s #%d (SR full)",
            Scheduler::instance().clock(), net_id.dump(), p.src.dump(),
	    srh->rtreq_seq());
      /* pkt is a rt req, even if data carrying, we don't want to log 
	 the drop using drop() since many nodes could be dropping the 
	 packet in this fashion */
      Packet::free(p.pkt);
      p.pkt = 0;
      return;		
    }

  // add ourselves to the source route
  p.route.appendToPath(net_id);

  if (verbose_srr)
    trace("SRR %.5f _%s_ rebroadcast %s #%d ->%s %s",
          Scheduler::instance().clock(), net_id.dump(), p.src.dump(),
          srh->rtreq_seq(), p.dest.dump(), p.route.dump());

  sendOutPacketWithRoute(p, false);
  return;      
}

/*===========================================================================
  Helpers
---------------------------------------------------------------------------*/
bool
DSRAgent::ignoreRouteRequestp(SRPacket &p)
// should we ignore this route request?
{
  hdr_sr *srh =  (hdr_sr*)p.pkt->access(off_sr_);

  if (request_table.get(p.src) >= srh->rtreq_seq())
    { // we've already processed a copy of this reqest so
      // we should drop the request silently
      return true;
    }
  if (p.route.member(net_id,MAC_id))
    { // we're already on the route, drop silently
      return true;
    }

  if (p.route.full())
    { // there won't be room for us to put our address into
      // the route
      // so drop silently - sigh, so close, and yet so far...
      // Note that since we don't record the req_id of this message yet,
      // we'll process the request if it gets to us on a shorter path
      return true;
    }
  return false;
}


bool
DSRAgent::replyFromRouteCache(SRPacket &p)
  /* - see if can reply to this route request from our cache
     if so, do it and return true, otherwise, return false 
     - frees or hands off p iff returns true */
{
  Path rest_of_route;
  Path complete_route = p.route;

  /* we shouldn't yet be on on the pkt's current source route */
  assert(!p.route.member(net_id, MAC_id));

  // do we have a cached route the target?
  /* XXX what if we have more than 1?  (and one is legal for reply from
     cache and one isn't?) 1/28/97 -dam */
  if (!route_cache->findRoute(p.dest, rest_of_route, 0))
    { // no route => we're done
      return false;
    }

  /* but we should be on on the remainder of the route (and should be at
   the start of the route */
  assert(rest_of_route[0] == net_id || rest_of_route[0] == MAC_id);

  if (rest_of_route.length() + p.route.length() > MAX_SR_LEN)
    return false; // too long to work with...

  // add our suggested completion to the route so far
  complete_route.appendPath(rest_of_route);

  // call compressPath to remove any double backs
  ::compressPath(complete_route);

  if (!complete_route.member(net_id, MAC_id))
    { // we're not on the suggested route, so we can't return it
      return false;
    }

  // if there is any other information piggybacked into the
  // route request pkt, we need to forward it on to the dst
  hdr_cmn *cmh =  (hdr_cmn*)p.pkt->access(off_cmn_);
  hdr_sr *srh =  (hdr_sr*)p.pkt->access(off_sr_);
  int request_seqnum = srh->rtreq_seq();
  
  if (PT_DSR != cmh->ptype()	// there's data
      || srh->route_reply()
      || (srh->route_error() && 
	  srh->down_links()[srh->num_route_errors()-1].tell_addr 
	  != GRAT_ROUTE_ERROR))
    { // must forward the packet on
      SRPacket p_copy = p;
      p.pkt = 0;
      srh->route_request() = 0;

      p_copy.route = complete_route;
      p_copy.route.setIterator(p.route.length());

      assert(p.route[p.route.index()] == net_id);
      
      if (verbose) trace("Sdebug %.9f _%s_ splitting %s to %s",
                         Scheduler::instance().clock(), net_id.dump(),
                         p.route.dump(), p_copy.route.dump());

      sendOutPacketWithRoute(p_copy,false);
    }
  else 
    {
      Packet::free(p.pkt);  // free the rcvd rt req before making rt reply
      p.pkt = 0;
    }

  // make up and send out a route reply
  p.route.appendToPath(net_id);
  p.route.reverseInPlace();
  route_cache->addRoute(p.route, Scheduler::instance().clock(), net_id);
  p.dest = p.src;
  p.src = net_id;
  p.pkt = allocpkt();

  hdr_ip *iph =  (hdr_ip*)p.pkt->access(off_ip_);
  iph->saddr() = Address::instance().create_ipaddr(p.src.addr,RT_PORT);
  iph->sport() = RT_PORT;
  iph->daddr() = Address::instance().create_ipaddr(p.dest.addr,RT_PORT);
  iph->dport() = RT_PORT;
  iph->ttl() = 255;

  srh = (hdr_sr*)p.pkt->access(off_sr_);
  srh->init();
  for (int i = 0 ; i < complete_route.length() ; i++)
    complete_route[i].fillSRAddr(srh->reply_addrs()[i]);
  srh->route_reply_len() = complete_route.length();
  srh->route_reply() = 1;

  // propagate the request sequence number in the reply for analysis purposes
  srh->rtreq_seq() = request_seqnum;

  hdr_cmn *cmnh =  (hdr_cmn*)p.pkt->access(off_cmn_);
  cmnh->ptype() = PT_DSR;
  cmnh->size() = IP_HDR_LEN;

  trace("SRR %.9f _%s_ cache-reply-sent %s -> %s #%d (len %d) %s",
	Scheduler::instance().clock(), net_id.dump(),
	p.src.dump(), p.dest.dump(), request_seqnum, complete_route.length(),
	complete_route.dump());
  sendOutPacketWithRoute(p, true);
  return true;
}


void
DSRAgent::sendOutPacketWithRoute(SRPacket& p, bool fresh, Time delay)
     // take packet and send it out, packet must a have a route in it
     // return value is not very meaningful
     // if fresh is true then reset the path before using it, if fresh
     //  is false then our caller wants us use a path with the index
     //  set as it currently is
{
  hdr_sr *srh =  (hdr_sr*)p.pkt->access(off_sr_);
  hdr_cmn *cmnh = (hdr_cmn*)p.pkt->access(off_cmn_);

  assert(srh->valid());
  assert(cmnh->size() > 0);

  ID dest;
  if (diff_subnet(p.dest,net_id)) {
	  //dest = ID(node_->base_stn()->address(),::IP);
	  dest = ID(node_->base_stn(),::IP);
	  if (dest == net_id) 
		  // Iam the base-station
		  dest = p.dest;
  }
  else
	  dest = p.dest;
  if (dest == net_id)
    { // it doesn't need to go on the wire, 'cause it's for us
      recv(p.pkt, (Handler *) 0);
      p.pkt = 0;
      return;
    }

  if (fresh)
    {
      p.route.resetIterator();
      if (verbose && !srh->route_request())
	{
	  trace("SO %.9f _%s_ originating %s %s", 
		Scheduler::instance().clock(), 
		net_id.dump(), packet_info.name(cmnh->ptype()), p.route.dump());
	}
    }
  p.route.fillSR(srh);
  cmnh->size() += srh->size();
  // set direction of pkt to DOWN , i.e downward
  cmnh->direction() = hdr_cmn::DOWN;
  
  if (srh->route_request())
    { // broadcast forward
      cmnh->xmit_failure_ = 0;
      cmnh->next_hop() = MAC_BROADCAST;
      cmnh->addr_type() = NS_AF_ILINK;
    }
  else
    { // forward according to source route
      cmnh->xmit_failure_ = XmitFailureCallback;
      cmnh->xmit_failure_data_ = (void *) this;
      cmnh->next_hop() = srh->get_next_addr();
      
      cmnh->addr_type() = srh->get_next_type();
      srh->cur_addr() = srh->cur_addr() + 1;
    }

  /* put route errors at the head of the ifq somehow? -dam 4/13/98 */

  // make sure we aren't cycling packets
  //assert(p.pkt->incoming == 0); // this is an outgoing packet
  //assert(cmnh->direction() == hdr_cmn::DOWN);

  if (ifq->length() > 25)
    trace("SIFQ %.5f _%s_ len %d",
          Scheduler::instance().clock(), net_id.dump(), ifq->length());

  // off it goes!
  if (srh->route_request())
    { // route requests need to be jittered a bit
      Scheduler::instance().schedule(ll, p.pkt, 
				     Random::uniform(RREQ_JITTER) + delay);
    }
  else
    { // no jitter required 
      Scheduler::instance().schedule(ll, p.pkt, delay);
    }
  p.pkt = NULL; /* packet sent off */
}

void
DSRAgent::getRouteForPacket(SRPacket &p, ID dest, bool retry)
  /* try to obtain a route for packet
     pkt is freed or handed off as needed, unless retry == true
     in which case it is not touched */
{
  // since we'll commonly be only one hop away, we should
  // arp first before route discovery as an optimization...


  Entry *e = request_table.getEntry(dest);
  Time time = Scheduler::instance().clock();
  
  /* for now, no piggybacking at all, queue all pkts */
  if (!retry) 
    {
      stickPacketInSendBuffer(p);
      p.pkt = 0; // pkt is handled for now (it's in sendbuffer)
    }

#if 0
  /* pre 4/13/98 logic -dam removed b/c it seemed more complicated than
     needed since we're not doing piggybacking and we're returning
     route replies via a reversed route (the copy in this code is
     critical if we need to piggyback route replies on the route request to
     discover the return path) */

  /* make the route request packet */
  SRPacket rrp = p;
  rrp.pkt = p.pkt->copy();
  hdr_sr *srh =  (hdr_sr*)rrp.pkt->access(off_sr_);
  hdr_ip *iph =  (hdr_ip*)rrp.pkt->access(off_ip_);
  hdr_cmn *cmnh =  (hdr_cmn*)rrp.pkt->access(off_cmn_);
  iph->daddr() = Address::instance().create_ipaddr(dest.getNSAddr_t(),RT_PORT);
  iph->dport() = RT_PORT;
  iph->saddr() = Address::instance().create_ipaddr(net_id.getNSAddr_t(),RT_PORT);
  iph->sport() = RT_PORT;
  cmnh->ptype() = PT_DSR;
  cmnh->size() = size_;
  cmnh->num_forwards() = 0;
#endif

  /* make the route request packet */
  SRPacket rrp;
  rrp.dest = dest;
  rrp.src = net_id;
  rrp.pkt = allocpkt();
  hdr_sr *srh =  (hdr_sr*)rrp.pkt->access(off_sr_);
  hdr_ip *iph =  (hdr_ip*)rrp.pkt->access(off_ip_);
  hdr_cmn *cmnh =  (hdr_cmn*)rrp.pkt->access(off_cmn_);
  
  iph->daddr() = Address::instance().create_ipaddr(dest.getNSAddr_t(),RT_PORT);
  
  iph->dport() = RT_PORT;
  iph->saddr() =
	  Address::instance().create_ipaddr(net_id.getNSAddr_t(),RT_PORT); 
  iph->sport() = RT_PORT;
  cmnh->ptype() = PT_DSR;
  cmnh->size() = size_ + IP_HDR_LEN; // add in IP header
  cmnh->num_forwards() = 0;
  
  srh->init();

  if (BackOffTest(e, time))
    { // it's time to start another route request cycle
      if (dsragent_ring_zero_search)
	{ // do a ring zero search
	  e->last_type = LIMIT0;
	  sendOutRtReq(rrp, 0);
	}
      else 
	{ // do a propagating route request right now
	  e->last_type = UNLIMIT;
	  sendOutRtReq(rrp, MAX_SR_LEN);
	}

      e->last_arp = time;
    } 
  else if (LIMIT0 == e->last_type && (time - e->last_arp) > arp_timeout)
   { // try propagating rt req since we haven't heard back from limited one
     e->last_type = UNLIMIT;
     sendOutRtReq(rrp, MAX_SR_LEN);
   }
  else
    { // it's not time to send another route request...
      if (!retry && verbose_srr)
	trace("SRR %.5f _%s_ RR-not-sent %s -> %s", 
	      Scheduler::instance().clock(), 
	      net_id.dump(), rrp.src.dump(), rrp.dest.dump());
      Packet::free(rrp.pkt); // dump the route request packet we made up
      rrp.pkt = 0;
      return;
    }
}

void
DSRAgent::sendOutRtReq(SRPacket &p, int max_prop)
  // turn p into a route request and launch it, max_prop of request is
  // set as specified
  // p.pkt is freed or handed off
{
  hdr_sr *srh =  (hdr_sr*)p.pkt->access(off_sr_);
  assert(srh->valid());

  srh->route_request() = 1;
  srh->rtreq_seq() = route_request_num++;
  srh->max_propagation() = max_prop;
  p.route.reset();
  p.route.appendToPath(net_id);

  if (dsragent_propagate_last_error && route_error_held 
      && Scheduler::instance().clock() - route_error_data_time  < max_err_hold)
    {
      assert(srh->num_route_errors() < MAX_ROUTE_ERRORS);
      srh->route_error() = 1;
      link_down *deadlink = &(srh->down_links()[srh->num_route_errors()]);
      deadlink->addr_type = NS_AF_INET;
      deadlink->from_addr = err_from.getNSAddr_t();
      deadlink->to_addr = err_to.getNSAddr_t();
      deadlink->tell_addr = GRAT_ROUTE_ERROR;