text: /*
   * services/mesh.c - deal with mesh of query states and handle events for that.
   *
   * Copyright (c) 2007, NLnet Labs. All rights reserved.
   *
   * This software is open source.
   * 
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 
   * Redistributions of source code must retain the above copyright notice,
   * this list of conditions and the following disclaimer.
   * 
   * Redistributions in binary form must reproduce the above copyright notice,
   * this list of conditions and the following disclaimer in the documentation
   * and/or other materials provided with the distribution.
   * 
   * Neither the name of the NLNET LABS nor the names of its contributors may
   * be used to endorse or promote products derived from this software without
   * specific prior written permission.
   * 
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
   * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  /**
   * \file
   *
   * This file contains functions to assist in dealing with a mesh of
   * query states. This mesh is supposed to be thread-specific.
   * It consists of query states (per qname, qtype, qclass) and connections
   * between query states and the super and subquery states, and replies to
   * send back to clients.
   */
  #include "config.h"
  #include "services/mesh.h"
  #include "services/outbound_list.h"
  #include "services/cache/dns.h"
  #include "services/cache/rrset.h"
  #include "util/log.h"
  #include "util/net_help.h"
  #include "util/module.h"
  #include "util/regional.h"
  #include "util/data/msgencode.h"
  #include "util/timehist.h"
  #include "util/fptr_wlist.h"
  #include "util/alloc.h"
  #include "util/config_file.h"
  #include "util/edns.h"
  #include "sldns/sbuffer.h"
  #include "sldns/wire2str.h"
  #include "services/localzone.h"
  #include "util/data/dname.h"
  #include "respip/respip.h"
  #include "services/listen_dnsport.h"
  
  /** subtract timers and the values do not overflow or become negative */
  static void
  timeval_subtract(struct timeval* d, const struct timeval* end, const struct timeval* start)
  {
  #ifndef S_SPLINT_S
  	time_t end_usec = end->tv_usec;
  	d->tv_sec = end->tv_sec - start->tv_sec;
  	if(end_usec < start->tv_usec) {
  		end_usec += 1000000;
  		d->tv_sec--;
  	}
  	d->tv_usec = end_usec - start->tv_usec;
  #endif
  }
  
  /** add timers and the values do not overflow or become negative */
  static void
  timeval_add(struct timeval* d, const struct timeval* add)
  {
  #ifndef S_SPLINT_S
  	d->tv_sec += add->tv_sec;
  	d->tv_usec += add->tv_usec;
  	if(d->tv_usec >= 1000000 ) {
  		d->tv_usec -= 1000000;
  		d->tv_sec++;
  	}
  #endif
  }
  
  /** divide sum of timers to get average */
  static void
  timeval_divide(struct timeval* avg, const struct timeval* sum, size_t d)
  {
  #ifndef S_SPLINT_S
  	size_t leftover;
  	if(d == 0) {
  		avg->tv_sec = 0;
  		avg->tv_usec = 0;
  		return;
  	}
  	avg->tv_sec = sum->tv_sec / d;
  	avg->tv_usec = sum->tv_usec / d;
  	/* handle fraction from seconds divide */
  	leftover = sum->tv_sec - avg->tv_sec*d;
  	avg->tv_usec += (leftover*1000000)/d;
  #endif
  }
  
  /** histogram compare of time values */
  static int
  timeval_smaller(const struct timeval* x, const struct timeval* y)
  {
  #ifndef S_SPLINT_S
  	if(x->tv_sec < y->tv_sec)
  		return 1;
  	else if(x->tv_sec == y->tv_sec) {
  		if(x->tv_usec <= y->tv_usec)
  			return 1;
  		else	return 0;
  	}
  	else	return 0;
  #endif
  }
  
  /**
   * Compare two response-ip client info entries for the purpose of mesh state
   * compare.  It returns 0 if ci_a and ci_b are considered equal; otherwise
   * 1 or -1 (they mean 'ci_a is larger/smaller than ci_b', respectively, but
   * in practice it should be only used to mean they are different).
   * We cannot share the mesh state for two queries if different response-ip
   * actions can apply in the end, even if those queries are otherwise identical.
   * For this purpose we compare tag lists and tag action lists; they should be
   * identical to share the same state.
   * For tag data, we don't look into the data content, as it can be
   * expensive; unless tag data are not defined for both or they point to the
   * exact same data in memory (i.e., they come from the same ACL entry), we
   * consider these data different.
   * Likewise, if the client info is associated with views, we don't look into
   * the views.  They are considered different unless they are exactly the same
   * even if the views only differ in the names.
   */
  static int
  client_info_compare(const struct respip_client_info* ci_a,
  	const struct respip_client_info* ci_b)
  {
  	int cmp;
  
  	if(!ci_a && !ci_b)
  		return 0;
  	if(ci_a && !ci_b)
  		return -1;
  	if(!ci_a && ci_b)
  		return 1;
  	if(ci_a->taglen != ci_b->taglen)
  		return (ci_a->taglen < ci_b->taglen) ? -1 : 1;
  	if(ci_a->taglist && !ci_b->taglist)
  		return -1;
  	if(!ci_a->taglist && ci_b->taglist)
  		return 1;
  	if(ci_a->taglist && ci_b->taglist) {
  		cmp = memcmp(ci_a->taglist, ci_b->taglist, ci_a->taglen);
  		if(cmp != 0)
  			return cmp;
  	}
  	if(ci_a->tag_actions_size != ci_b->tag_actions_size)
  		return (ci_a->tag_actions_size < ci_b->tag_actions_size) ?
  			-1 : 1;
  	if(ci_a->tag_actions && !ci_b->tag_actions)
  		return -1;
  	if(!ci_a->tag_actions && ci_b->tag_actions)
  		return 1;
  	if(ci_a->tag_actions && ci_b->tag_actions) {
  		cmp = memcmp(ci_a->tag_actions, ci_b->tag_actions,
  			ci_a->tag_actions_size);
  		if(cmp != 0)
  			return cmp;
  	}
  	if(ci_a->tag_datas != ci_b->tag_datas)
  		return ci_a->tag_datas < ci_b->tag_datas ? -1 : 1;
  	if(ci_a->view != ci_b->view)
  		return ci_a->view < ci_b->view ? -1 : 1;
  	/* For the unbound daemon these should be non-NULL and identical,
  	 * but we check that just in case. */
  	if(ci_a->respip_set != ci_b->respip_set)
  		return ci_a->respip_set < ci_b->respip_set ? -1 : 1;
  	return 0;
  }
  
  int
  mesh_state_compare(const void* ap, const void* bp)
  {
  	struct mesh_state* a = (struct mesh_state*)ap;
  	struct mesh_state* b = (struct mesh_state*)bp;
  	int cmp;
  
  	if(a->unique < b->unique)
  		return -1;
  	if(a->unique > b->unique)
  		return 1;
  
  	if(a->s.is_priming && !b->s.is_priming)
  		return -1;
  	if(!a->s.is_priming && b->s.is_priming)
  		return 1;
  
  	if(a->s.is_valrec && !b->s.is_valrec)
  		return -1;
  	if(!a->s.is_valrec && b->s.is_valrec)
  		return 1;
  
  	if((a->s.query_flags&BIT_RD) && !(b->s.query_flags&BIT_RD))
  		return -1;
  	if(!(a->s.query_flags&BIT_RD) && (b->s.query_flags&BIT_RD))
  		return 1;
  
  	if((a->s.query_flags&BIT_CD) && !(b->s.query_flags&BIT_CD))
  		return -1;
  	if(!(a->s.query_flags&BIT_CD) && (b->s.query_flags&BIT_CD))
  		return 1;
  
  	cmp = query_info_compare(&a->s.qinfo, &b->s.qinfo);
  	if(cmp != 0)
  		return cmp;
  	return client_info_compare(a->s.client_info, b->s.client_info);
  }
  
  int
  mesh_state_ref_compare(const void* ap, const void* bp)
  {
  	struct mesh_state_ref* a = (struct mesh_state_ref*)ap;
  	struct mesh_state_ref* b = (struct mesh_state_ref*)bp;
  	return mesh_state_compare(a->s, b->s);
  }
  
  struct mesh_area* 
  mesh_create(struct module_stack* stack, struct module_env* env)
  {
  	struct mesh_area* mesh = calloc(1, sizeof(struct mesh_area));
  	if(!mesh) {
  		log_err("mesh area alloc: out of memory");
  		return NULL;
  	}
  	mesh->histogram = timehist_setup();
  	mesh->qbuf_bak = sldns_buffer_new(env->cfg->msg_buffer_size);
  	if(!mesh->histogram || !mesh->qbuf_bak) {
  		free(mesh);
  		log_err("mesh area alloc: out of memory");
  		return NULL;
  	}
  	mesh->mods = *stack;
  	mesh->env = env;
  	rbtree_init(&mesh->run, &mesh_state_compare);
  	rbtree_init(&mesh->all, &mesh_state_compare);
  	mesh->num_reply_addrs = 0;
  	mesh->num_reply_states = 0;
  	mesh->num_detached_states = 0;
  	mesh->num_forever_states = 0;
  	mesh->stats_jostled = 0;
  	mesh->stats_dropped = 0;
  	mesh->ans_expired = 0;
  	mesh->max_reply_states = env->cfg->num_queries_per_thread;
  	mesh->max_forever_states = (mesh->max_reply_states+1)/2;
  #ifndef S_SPLINT_S
  	mesh->jostle_max.tv_sec = (time_t)(env->cfg->jostle_time / 1000);
  	mesh->jostle_max.tv_usec = (time_t)((env->cfg->jostle_time % 1000)
  		*1000);
  #endif
  	return mesh;
  }
  
  /** help mesh delete delete mesh states */
  static void
  mesh_delete_helper(rbnode_type* n)
  {
  	struct mesh_state* mstate = (struct mesh_state*)n->key;
  	/* perform a full delete, not only 'cleanup' routine,
  	 * because other callbacks expect a clean state in the mesh.
  	 * For 're-entrant' calls */
  	mesh_state_delete(&mstate->s);
  	/* but because these delete the items from the tree, postorder
  	 * traversal and rbtree rebalancing do not work together */
  }
  
  void 
  mesh_delete(struct mesh_area* mesh)
  {
  	if(!mesh)
  		return;
  	/* free all query states */
  	while(mesh->all.count)
  		mesh_delete_helper(mesh->all.root);
  	timehist_delete(mesh->histogram);
  	sldns_buffer_free(mesh->qbuf_bak);
  	free(mesh);
  }
  
  void
  mesh_delete_all(struct mesh_area* mesh)
  {
  	/* free all query states */
  	while(mesh->all.count)
  		mesh_delete_helper(mesh->all.root);
  	mesh->stats_dropped += mesh->num_reply_addrs;
  	/* clear mesh area references */
  	rbtree_init(&mesh->run, &mesh_state_compare);
  	rbtree_init(&mesh->all, &mesh_state_compare);
  	mesh->num_reply_addrs = 0;
  	mesh->num_reply_states = 0;
  	mesh->num_detached_states = 0;
  	mesh->num_forever_states = 0;
  	mesh->forever_first = NULL;
  	mesh->forever_last = NULL;
  	mesh->jostle_first = NULL;
  	mesh->jostle_last = NULL;
  }
  
  int mesh_make_new_space(struct mesh_area* mesh, sldns_buffer* qbuf)
  {
  	struct mesh_state* m = mesh->jostle_first;
  	/* free space is available */
  	if(mesh->num_reply_states < mesh->max_reply_states)
  		return 1;
  	/* try to kick out a jostle-list item */
  	if(m && m->reply_list && m->list_select == mesh_jostle_list) {
  		/* how old is it? */
  		struct timeval age;
  		timeval_subtract(&age, mesh->env->now_tv, 
  			&m->reply_list->start_time);
  		if(timeval_smaller(&mesh->jostle_max, &age)) {
  			/* its a goner */
  			log_nametypeclass(VERB_ALGO, "query jostled out to "
  				"make space for a new one",
  				m->s.qinfo.qname, m->s.qinfo.qtype,
  				m->s.qinfo.qclass);
  			/* backup the query */
  			if(qbuf) sldns_buffer_copy(mesh->qbuf_bak, qbuf);
  			/* notify supers */
  			if(m->super_set.count > 0) {
  				verbose(VERB_ALGO, "notify supers of failure");
  				m->s.return_msg = NULL;
  				m->s.return_rcode = LDNS_RCODE_SERVFAIL;
  				mesh_walk_supers(mesh, m);
  			}
  			mesh->stats_jostled ++;
  			mesh_state_delete(&m->s);
  			/* restore the query - note that the qinfo ptr to
  			 * the querybuffer is then correct again. */
  			if(qbuf) sldns_buffer_copy(qbuf, mesh->qbuf_bak);
  			return 1;
  		}
  	}
  	/* no space for new item */
  	return 0;
  }
  
  struct dns_msg*
  mesh_serve_expired_lookup(struct module_qstate* qstate,
  	struct query_info* lookup_qinfo)
  {
  	hashvalue_type h;
  	struct lruhash_entry* e;
  	struct dns_msg* msg;
  	struct reply_info* data;
  	struct msgreply_entry* key;
  	time_t timenow = *qstate->env->now;
  	int must_validate = (!(qstate->query_flags&BIT_CD)
  		|| qstate->env->cfg->ignore_cd) && qstate->env->need_to_validate;
  	/* Lookup cache */
  	h = query_info_hash(lookup_qinfo, qstate->query_flags);
  	e = slabhash_lookup(qstate->env->msg_cache, h, lookup_qinfo, 0);
  	if(!e) return NULL;
  
  	key = (struct msgreply_entry*)e->key;
  	data = (struct reply_info*)e->data;
  	msg = tomsg(qstate->env, &key->key, data, qstate->region, timenow,
  		qstate->env->cfg->serve_expired, qstate->env->scratch);
  	if(!msg)
  		goto bail_out;
  
  	/* Check CNAME chain (if any)
  	 * This is part of tomsg above; no need to check now. */
  
  	/* Check security status of the cached answer.
  	 * tomsg above has a subset of these checks, so we are leaving
  	 * these as is.
  	 * In case of bogus or revalidation we don't care to reply here. */
  	if(must_validate && (msg->rep->security == sec_status_bogus ||
  		msg->rep->security == sec_status_secure_sentinel_fail)) {
  		verbose(VERB_ALGO, "Serve expired: bogus answer found in cache");
  		goto bail_out;
  	} else if(msg->rep->security == sec_status_unchecked && must_validate) {
  		verbose(VERB_ALGO, "Serve expired: unchecked entry needs "
  			"validation");
  		goto bail_out; /* need to validate cache entry first */
  	} else if(msg->rep->security == sec_status_secure &&
  		!reply_all_rrsets_secure(msg->rep) && must_validate) {
  			verbose(VERB_ALGO, "Serve expired: secure entry"
  				" changed status");
  			goto bail_out; /* rrset changed, re-verify */
  	}
  
  	lock_rw_unlock(&e->lock);
  	return msg;
  
  bail_out:
  	lock_rw_unlock(&e->lock);
  	return NULL;
  }
  
  
  /** Init the serve expired data structure */
  static int
  mesh_serve_expired_init(struct mesh_state* mstate, int timeout)
  {
  	struct timeval t;
  
  	/* Create serve_expired_data if not there yet */
  	if(!mstate->s.serve_expired_data) {
  		mstate->s.serve_expired_data = (struct serve_expired_data*)
  			regional_alloc_zero(
  				mstate->s.region, sizeof(struct serve_expired_data));
  		if(!mstate->s.serve_expired_data)
  			return 0;
  	}
  
  	/* Don't overwrite the function if already set */
  	mstate->s.serve_expired_data->get_cached_answer =
  		mstate->s.serve_expired_data->get_cached_answer?
  		mstate->s.serve_expired_data->get_cached_answer:
  		mesh_serve_expired_lookup;
  
  	/* In case this timer already popped, start it again */
  	if(!mstate->s.serve_expired_data->timer) {
  		mstate->s.serve_expired_data->timer = comm_timer_create(
  			mstate->s.env->worker_base, mesh_serve_expired_callback, mstate);
  		if(!mstate->s.serve_expired_data->timer)
  			return 0;
  #ifndef S_SPLINT_S
  		t.tv_sec = timeout/1000;
  		t.tv_usec = (timeout%1000)*1000;
  #endif
  		comm_timer_set(mstate->s.serve_expired_data->timer, &t);
  	}
  	return 1;
  }
  
  void mesh_new_client(struct mesh_area* mesh, struct query_info* qinfo,
  	struct respip_client_info* cinfo, uint16_t qflags,
  	struct edns_data* edns, struct comm_reply* rep, uint16_t qid)
  {
  	struct mesh_state* s = NULL;
  	int unique = unique_mesh_state(edns->opt_list, mesh->env);
  	int was_detached = 0;
  	int was_noreply = 0;
  	int added = 0;
  	int timeout = mesh->env->cfg->serve_expired?
  		mesh->env->cfg->serve_expired_client_timeout:0;
  	struct sldns_buffer* r_buffer = rep->c->buffer;
  	if(rep->c->tcp_req_info) {
  		r_buffer = rep->c->tcp_req_info->spool_buffer;
  	}
  	if(!unique)
  		s = mesh_area_find(mesh, cinfo, qinfo, qflags&(BIT_RD|BIT_CD), 0, 0);
  	/* does this create a new reply state? */
  	if(!s || s->list_select == mesh_no_list) {
  		if(!mesh_make_new_space(mesh, rep->c->buffer)) {
  			verbose(VERB_ALGO, "Too many queries. dropping "
  				"incoming query.");
  			comm_point_drop_reply(rep);
  			mesh->stats_dropped++;
  			return;
  		}
  		/* for this new reply state, the reply address is free,
  		 * so the limit of reply addresses does not stop reply states*/
  	} else {
  		/* protect our memory usage from storing reply addresses */
  		if(mesh->num_reply_addrs > mesh->max_reply_states*16) {
  			verbose(VERB_ALGO, "Too many requests queued. "
  				"dropping incoming query.");
  			comm_point_drop_reply(rep);
  			mesh->stats_dropped++;
  			return;
  		}
  	}
  	/* see if it already exists, if not, create one */
  	if(!s) {
  #ifdef UNBOUND_DEBUG
  		struct rbnode_type* n;
  #endif
  		s = mesh_state_create(mesh->env, qinfo, cinfo,
  			qflags&(BIT_RD|BIT_CD), 0, 0);
  		if(!s) {
  			log_err("mesh_state_create: out of memory; SERVFAIL");
  			if(!inplace_cb_reply_servfail_call(mesh->env, qinfo, NULL, NULL,
  				LDNS_RCODE_SERVFAIL, edns, rep, mesh->env->scratch))
  					edns->opt_list = NULL;
  			error_encode(r_buffer, LDNS_RCODE_SERVFAIL,
  				qinfo, qid, qflags, edns);
  			comm_point_send_reply(rep);
  			return;
  		}
  		if(unique)
  			mesh_state_make_unique(s);
  		/* copy the edns options we got from the front */
  		if(edns->opt_list) {
  			s->s.edns_opts_front_in = edns_opt_copy_region(edns->opt_list,
  				s->s.region);
  			if(!s->s.edns_opts_front_in) {
  				log_err("mesh_state_create: out of memory; SERVFAIL");
  				if(!inplace_cb_reply_servfail_call(mesh->env, qinfo, NULL,
  					NULL, LDNS_RCODE_SERVFAIL, edns, rep, mesh->env->scratch))
  						edns->opt_list = NULL;
  				error_encode(r_buffer, LDNS_RCODE_SERVFAIL,
  					qinfo, qid, qflags, edns);
  				comm_point_send_reply(rep);
  				return;
  			}
  		}
  
  #ifdef UNBOUND_DEBUG
  		n =
  #else
  		(void)
  #endif
  		rbtree_insert(&mesh->all, &s->node);
  		log_assert(n != NULL);
  		/* set detached (it is now) */
  		mesh->num_detached_states++;
  		added = 1;
  	}
  	if(!s->reply_list && !s->cb_list) {
  		was_noreply = 1;
  		if(s->super_set.count == 0) {
  			was_detached = 1;
  		}
  	}
  	/* add reply to s */
  	if(!mesh_state_add_reply(s, edns, rep, qid, qflags, qinfo)) {
  		log_err("mesh_new_client: out of memory; SERVFAIL");
  		goto servfail_mem;
  	}
  	if(rep->c->tcp_req_info) {
  		if(!tcp_req_info_add_meshstate(rep->c->tcp_req_info, mesh, s)) {
  			log_err("mesh_new_client: out of memory add tcpreqinfo");
  			goto servfail_mem;
  		}
  	}
  	if(rep->c->use_h2) {
  		http2_stream_add_meshstate(rep->c->h2_stream, mesh, s);
  	}
  	/* add serve expired timer if required and not already there */
  	if(timeout && !mesh_serve_expired_init(s, timeout)) {
  		log_err("mesh_new_client: out of memory initializing serve expired");
  		goto servfail_mem;
  	}
  	/* update statistics */
  	if(was_detached) {
  		log_assert(mesh->num_detached_states > 0);
  		mesh->num_detached_states--;
  	}
  	if(was_noreply) {
  		mesh->num_reply_states ++;
  	}
  	mesh->num_reply_addrs++;
  	if(s->list_select == mesh_no_list) {
  		/* move to either the forever or the jostle_list */
  		if(mesh->num_forever_states < mesh->max_forever_states) {
  			mesh->num_forever_states ++;
  			mesh_list_insert(s, &mesh->forever_first, 
  				&mesh->forever_last);
  			s->list_select = mesh_forever_list;
  		} else {
  			mesh_list_insert(s, &mesh->jostle_first, 
  				&mesh->jostle_last);
  			s->list_select = mesh_jostle_list;
  		}
  	}
  	if(added)
  		mesh_run(mesh, s, module_event_new, NULL);
  	return;
  
  servfail_mem:
  	if(!inplace_cb_reply_servfail_call(mesh->env, qinfo, &s->s,
  		NULL, LDNS_RCODE_SERVFAIL, edns, rep, mesh->env->scratch))
  			edns->opt_list = NULL;
  	error_encode(r_buffer, LDNS_RCODE_SERVFAIL,
  		qinfo, qid, qflags, edns);
  	comm_point_send_reply(rep);
  	if(added)
  		mesh_state_delete(&s->s);
  	return;
  }
  
  int 
  mesh_new_callback(struct mesh_area* mesh, struct query_info* qinfo,
  	uint16_t qflags, struct edns_data* edns, sldns_buffer* buf, 
  	uint16_t qid, mesh_cb_func_type cb, void* cb_arg)
  {
  	struct mesh_state* s = NULL;
  	int unique = unique_mesh_state(edns->opt_list, mesh->env);
  	int timeout = mesh->env->cfg->serve_expired?
  		mesh->env->cfg->serve_expired_client_timeout:0;
  	int was_detached = 0;
  	int was_noreply = 0;
  	int added = 0;
  	if(!unique)
  		s = mesh_area_find(mesh, NULL, qinfo, qflags&(BIT_RD|BIT_CD), 0, 0);
  
  	/* there are no limits on the number of callbacks */
  
  	/* see if it already exists, if not, create one */
  	if(!s) {
  #ifdef UNBOUND_DEBUG
  		struct rbnode_type* n;
  #endif
  		s = mesh_state_create(mesh->env, qinfo, NULL,
  			qflags&(BIT_RD|BIT_CD), 0, 0);
  		if(!s) {
  			return 0;
  		}
  		if(unique)
  			mesh_state_make_unique(s);
  		if(edns->opt_list) {
  			s->s.edns_opts_front_in = edns_opt_copy_region(edns->opt_list,
  				s->s.region);
  			if(!s->s.edns_opts_front_in) {
  				return 0;
  			}
  		}
  #ifdef UNBOUND_DEBUG
  		n =
  #else
  		(void)
  #endif
  		rbtree_insert(&mesh->all, &s->node);
  		log_assert(n != NULL);
  		/* set detached (it is now) */
  		mesh->num_detached_states++;
  		added = 1;
  	}
  	if(!s->reply_list && !s->cb_list) {
  		was_noreply = 1;
  		if(s->super_set.count == 0) {
  			was_detached = 1;
  		}
  	}
  	/* add reply to s */
  	if(!mesh_state_add_cb(s, edns, buf, cb, cb_arg, qid, qflags)) {
  		if(added)
  			mesh_state_delete(&s->s);
  		return 0;
  	}
  	/* add serve expired timer if not already there */
  	if(timeout && !mesh_serve_expired_init(s, timeout)) {
  		return 0;
  	}
  	/* update statistics */
  	if(was_detached) {
  		log_assert(mesh->num_detached_states > 0);
  		mesh->num_detached_states--;
  	}
  	if(was_noreply) {
  		mesh->num_reply_states ++;
  	}
  	mesh->num_reply_addrs++;
  	if(added)
  		mesh_run(mesh, s, module_event_new, NULL);
  	return 1;
  }
  
  /* Internal backend routine of mesh_new_prefetch().  It takes one additional
   * parameter, 'run', which controls whether to run the prefetch state
   * immediately.  When this function is called internally 'run' could be
   * 0 (false), in which case the new state is only made runnable so it
   * will not be run recursively on top of the current state. */
  static void mesh_schedule_prefetch(struct mesh_area* mesh,
  	struct query_info* qinfo, uint16_t qflags, time_t leeway, int run)
  {
  	struct mesh_state* s = mesh_area_find(mesh, NULL, qinfo,
  		qflags&(BIT_RD|BIT_CD), 0, 0);
  #ifdef UNBOUND_DEBUG
  	struct rbnode_type* n;
  #endif
  	/* already exists, and for a different purpose perhaps.
  	 * if mesh_no_list, keep it that way. */
  	if(s) {
  		/* make it ignore the cache from now on */
  		if(!s->s.blacklist)
  			sock_list_insert(&s->s.blacklist, NULL, 0, s->s.region);
  		if(s->s.prefetch_leeway < leeway)
  			s->s.prefetch_leeway = leeway;
  		return;
  	}
  	if(!mesh_make_new_space(mesh, NULL)) {
  		verbose(VERB_ALGO, "Too many queries. dropped prefetch.");
  		mesh->stats_dropped ++;
  		return;
  	}
  
  	s = mesh_state_create(mesh->env, qinfo, NULL,
  		qflags&(BIT_RD|BIT_CD), 0, 0);
  	if(!s) {
  		log_err("prefetch mesh_state_create: out of memory");
  		return;
  	}
  #ifdef UNBOUND_DEBUG
  	n =
  #else
  	(void)
  #endif
  	rbtree_insert(&mesh->all, &s->node);
  	log_assert(n != NULL);
  	/* set detached (it is now) */
  	mesh->num_detached_states++;
  	/* make it ignore the cache */
  	sock_list_insert(&s->s.blacklist, NULL, 0, s->s.region);
  	s->s.prefetch_leeway = leeway;
  
  	if(s->list_select == mesh_no_list) {
  		/* move to either the forever or the jostle_list */
  		if(mesh->num_forever_states < mesh->max_forever_states) {
  			mesh->num_forever_states ++;
  			mesh_list_insert(s, &mesh->forever_first, 
  				&mesh->forever_last);
  			s->list_select = mesh_forever_list;
  		} else {
  			mesh_list_insert(s, &mesh->jostle_first, 
  				&mesh->jostle_last);
  			s->list_select = mesh_jostle_list;
  		}
  	}
  
  	if(!run) {
  #ifdef UNBOUND_DEBUG
  		n =
  #else
  		(void)
  #endif
  		rbtree_insert(&mesh->run, &s->run_node);
  		log_assert(n != NULL);
  		return;
  	}
  
  	mesh_run(mesh, s, module_event_new, NULL);
  }
  
  void mesh_new_prefetch(struct mesh_area* mesh, struct query_info* qinfo,
          uint16_t qflags, time_t leeway)
  {
  	mesh_schedule_prefetch(mesh, qinfo, qflags, leeway, 1);
  }
  
  void mesh_report_reply(struct mesh_area* mesh, struct outbound_entry* e,
          struct comm_reply* reply, int what)
  {
  	enum module_ev event = module_event_reply;
  	e->qstate->reply = reply;
  	if(what != NETEVENT_NOERROR) {
  		event = module_event_noreply;
  		if(what == NETEVENT_CAPSFAIL)
  			event = module_event_capsfail;
  	}
  	mesh_run(mesh, e->qstate->mesh_info, event, e);
  }
  
  struct mesh_state*
  mesh_state_create(struct module_env* env, struct query_info* qinfo,
  	struct respip_client_info* cinfo, uint16_t qflags, int prime,
  	int valrec)
  {
  	struct regional* region = alloc_reg_obtain(env->alloc);
  	struct mesh_state* mstate;
  	int i;
  	if(!region)
  		return NULL;
  	mstate = (struct mesh_state*)regional_alloc(region, 
  		sizeof(struct mesh_state));
  	if(!mstate) {
  		alloc_reg_release(env->alloc, region);
  		return NULL;
  	}
  	memset(mstate, 0, sizeof(*mstate));
  	mstate->node = *RBTREE_NULL;
  	mstate->run_node = *RBTREE_NULL;
  	mstate->node.key = mstate;
  	mstate->run_node.key = mstate;
  	mstate->reply_list = NULL;
  	mstate->list_select = mesh_no_list;
  	mstate->replies_sent = 0;
  	rbtree_init(&mstate->super_set, &mesh_state_ref_compare);
  	rbtree_init(&mstate->sub_set, &mesh_state_ref_compare);
  	mstate->num_activated = 0;
  	mstate->unique = NULL;
  	/* init module qstate */
  	mstate->s.qinfo.qtype = qinfo->qtype;
  	mstate->s.qinfo.qclass = qinfo->qclass;
  	mstate->s.qinfo.local_alias = NULL;
  	mstate->s.qinfo.qname_len = qinfo->qname_len;
  	mstate->s.qinfo.qname = regional_alloc_init(region, qinfo->qname,
  		qinfo->qname_len);
  	if(!mstate->s.qinfo.qname) {
  		alloc_reg_release(env->alloc, region);
  		return NULL;
  	}
  	if(cinfo) {
  		mstate->s.client_info = regional_alloc_init(region, cinfo,
  			sizeof(*cinfo));
  		if(!mstate->s.client_info) {
  			alloc_reg_release(env->alloc, region);
  			return NULL;
  		}
  	}
  	/* remove all weird bits from qflags */
  	mstate->s.query_flags = (qflags & (BIT_RD|BIT_CD));
  	mstate->s.is_priming = prime;
  	mstate->s.is_valrec = valrec;
  	mstate->s.reply = NULL;
  	mstate->s.region = region;
  	mstate->s.curmod = 0;
  	mstate->s.return_msg = 0;
  	mstate->s.return_rcode = LDNS_RCODE_NOERROR;
  	mstate->s.env = env;
  	mstate->s.mesh_info = mstate;
  	mstate->s.prefetch_leeway = 0;
  	mstate->s.serve_expired_data = NULL;
  	mstate->s.no_cache_lookup = 0;
  	mstate->s.no_cache_store = 0;
  	mstate->s.need_refetch = 0;
  	mstate->s.was_ratelimited = 0;
  
  	/* init modules */
  	for(i=0; i<env->mesh->mods.num; i++) {
  		mstate->s.minfo[i] = NULL;
  		mstate->s.ext_state[i] = module_state_initial;
  	}
  	/* init edns option lists */
  	mstate->s.edns_opts_front_in = NULL;
  	mstate->s.edns_opts_back_out = NULL;
  	mstate->s.edns_opts_back_in = NULL;
  	mstate->s.edns_opts_front_out = NULL;
  
  	return mstate;
  }
  
  int
  mesh_state_is_unique(struct mesh_state* mstate)
  {
  	return mstate->unique != NULL;
  }
  
  void
  mesh_state_make_unique(struct mesh_state* mstate)
  {
  	mstate->unique = mstate;
  }
  
  void 
  mesh_state_cleanup(struct mesh_state* mstate)
  {
  	struct mesh_area* mesh;
  	int i;
  	if(!mstate)
  		return;
  	mesh = mstate->s.env->mesh;
  	/* Stop and delete the serve expired timer */
  	if(mstate->s.serve_expired_data && mstate->s.serve_expired_data->timer) {
  		comm_timer_delete(mstate->s.serve_expired_data->timer);
  		mstate->s.serve_expired_data->timer = NULL;
  	}
  	/* drop unsent replies */
  	if(!mstate->replies_sent) {
  		struct mesh_reply* rep = mstate->reply_list;
  		struct mesh_cb* cb;
  		/* in tcp_req_info, the mstates linked are removed, but
  		 * the reply_list is now NULL, so the remove-from-empty-list
  		 * takes no time and also it does not do the mesh accounting */
  		mstate->reply_list = NULL;
  		for(; rep; rep=rep->next) {
  			comm_point_drop_reply(&rep->query_reply);
  			log_assert(mesh->num_reply_addrs > 0);
  			mesh->num_reply_addrs--;
  		}
  		while((cb = mstate->cb_list)!=NULL) {
  			mstate->cb_list = cb->next;
  			fptr_ok(fptr_whitelist_mesh_cb(cb->cb));
  			(*cb->cb)(cb->cb_arg, LDNS_RCODE_SERVFAIL, NULL,
  				sec_status_unchecked, NULL, 0);
  			log_assert(mesh->num_reply_addrs > 0);
  			mesh->num_reply_addrs--;
  		}
  	}
  
  	/* de-init modules */
  	for(i=0; i<mesh->mods.num; i++) {
  		fptr_ok(fptr_whitelist_mod_clear(mesh->mods.mod[i]->clear));
  		(*mesh->mods.mod[i]->clear)(&mstate->s, i);
  		mstate->s.minfo[i] = NULL;
  		mstate->s.ext_state[i] = module_finished;
  	}
  	alloc_reg_release(mstate->s.env->alloc, mstate->s.region);
  }
  
  void 
  mesh_state_delete(struct module_qstate* qstate)
  {
  	struct mesh_area* mesh;
  	struct mesh_state_ref* super, ref;
  	struct mesh_state* mstate;
  	if(!qstate)
  		return;
  	mstate = qstate->mesh_info;
  	mesh = mstate->s.env->mesh;
  	mesh_detach_subs(&mstate->s);
  	if(mstate->list_select == mesh_forever_list) {
  		mesh->num_forever_states --;
  		mesh_list_remove(mstate, &mesh->forever_first, 
  			&mesh->forever_last);
  	} else if(mstate->list_select == mesh_jostle_list) {
  		mesh_list_remove(mstate, &mesh->jostle_first, 
  			&mesh->jostle_last);
  	}
  	if(!mstate->reply_list && !mstate->cb_list
  		&& mstate->super_set.count == 0) {
  		log_assert(mesh->num_detached_states > 0);
  		mesh->num_detached_states--;
  	}
  	if(mstate->reply_list || mstate->cb_list) {
  		log_assert(mesh->num_reply_states > 0);
  		mesh->num_reply_states--;
  	}
  	ref.node.key = &ref;
  	ref.s = mstate;
  	RBTREE_FOR(super, struct mesh_state_ref*, &mstate->super_set) {
  		(void)rbtree_delete(&super->s->sub_set, &ref);
  	}
  	(void)rbtree_delete(&mesh->run, mstate);
  	(void)rbtree_delete(&mesh->all, mstate);
  	mesh_state_cleanup(mstate);
  }
  
  /** helper recursive rbtree find routine */
  static int
  find_in_subsub(struct mesh_state* m, struct mesh_state* tofind, size_t *c)
  {
  	struct mesh_state_ref* r;
  	if((*c)++ > MESH_MAX_SUBSUB)
  		return 1;
  	RBTREE_FOR(r, struct mesh_state_ref*, &m->sub_set) {
  		if(r->s == tofind || find_in_subsub(r->s, tofind, c))
  			return 1;
  	}
  	return 0;
  }
  
  /** find cycle for already looked up mesh_state */
  static int
  mesh_detect_cycle_found(struct module_qstate* qstate, struct mesh_state* dep_m)
  {
  	struct mesh_state* cyc_m = qstate->mesh_info;
  	size_t counter = 0;
  	if(!dep_m)
  		return 0;
  	if(dep_m == cyc_m || find_in_subsub(dep_m, cyc_m, &counter)) {
  		if(counter > MESH_MAX_SUBSUB)
  			return 2;
  		return 1;
  	}
  	return 0;
  }
  
  void mesh_detach_subs(struct module_qstate* qstate)
  {
  	struct mesh_area* mesh = qstate->env->mesh;
  	struct mesh_state_ref* ref, lookup;
  #ifdef UNBOUND_DEBUG
  	struct rbnode_type* n;
  #endif
  	lookup.node.key = &lookup;
  	lookup.s = qstate->mesh_info;
  	RBTREE_FOR(ref, struct mesh_state_ref*, &qstate->mesh_info->sub_set) {
  #ifdef UNBOUND_DEBUG
  		n =
  #else
  		(void)
  #endif
  		rbtree_delete(&ref->s->super_set, &lookup);
  		log_assert(n != NULL); /* must have been present */
  		if(!ref->s->reply_list && !ref->s->cb_list
  			&& ref->s->super_set.count == 0) {
  			mesh->num_detached_states++;
  			log_assert(mesh->num_detached_states + 
  				mesh->num_reply_states <= mesh->all.count);
  		}
  	}
  	rbtree_init(&qstate->mesh_info->sub_set, &mesh_state_ref_compare);
  }
  
  int mesh_add_sub(struct module_qstate* qstate, struct query_info* qinfo,
          uint16_t qflags, int prime, int valrec, struct module_qstate** newq,
  	struct mesh_state** sub)
  {
  	/* find it, if not, create it */
  	struct mesh_area* mesh = qstate->env->mesh;
  	*sub = mesh_area_find(mesh, NULL, qinfo, qflags,
  		prime, valrec);
  	if(mesh_detect_cycle_found(qstate, *sub)) {
  		verbose(VERB_ALGO, "attach failed, cycle detected");
  		return 0;
  	}
  	if(!*sub) {
  #ifdef UNBOUND_DEBUG
  		struct rbnode_type* n;
  #endif
  		/* create a new one */
  		*sub = mesh_state_create(qstate->env, qinfo, NULL, qflags, prime,
  			valrec);
  		if(!*sub) {
  			log_err("mesh_attach_sub: out of memory");
  			return 0;
  		}
  #ifdef UNBOUND_DEBUG
  		n =
  #else
  		(void)
  #endif
  		rbtree_insert(&mesh->all, &(*sub)->node);
  		log_assert(n != NULL);
  		/* set detached (it is now) */
  		mesh->num_detached_states++;
  		/* set new query state to run */
  #ifdef UNBOUND_DEBUG
  		n =
  #else
  		(void)
  #endif
  		rbtree_insert(&mesh->run, &(*sub)->run_node);
  		log_assert(n != NULL);
  		*newq = &(*sub)->s;
  	} else
  		*newq = NULL;
  	return 1;
  }
  
  int mesh_attach_sub(struct module_qstate* qstate, struct query_info* qinfo,
          uint16_t qflags, int prime, int valrec, struct module_qstate** newq)
  {
  	struct mesh_area* mesh = qstate->env->mesh;
  	struct mesh_state* sub = NULL;
  	int was_detached;
  	if(!mesh_add_sub(qstate, qinfo, qflags, prime, valrec, newq, &sub))
  		return 0;
  	was_detached = (sub->super_set.count == 0);
  	if(!mesh_state_attachment(qstate->mesh_info, sub))
  		return 0;
  	/* if it was a duplicate  attachment, the count was not zero before */
  	if(!sub->reply_list && !sub->cb_list && was_detached && 
  		sub->super_set.count == 1) {
  		/* it used to be detached, before this one got added */
  		log_assert(mesh->num_detached_states > 0);
  		mesh->num_detached_states--;
  	}
  	/* *newq will be run when inited after the current module stops */
  	return 1;
  }
  
  int mesh_state_attachment(struct mesh_state* super, struct mesh_state* sub)
  {
  #ifdef UNBOUND_DEBUG
  	struct rbnode_type* n;
  #endif
  	struct mesh_state_ref* subref; /* points to sub, inserted in super */
  	struct mesh_state_ref* superref; /* points to super, inserted in sub */
  	if( !(subref = regional_alloc(super->s.region,
  		sizeof(struct mesh_state_ref))) ||
  		!(superref = regional_alloc(sub->s.region,
  		sizeof(struct mesh_state_ref))) ) {
  		log_err("mesh_state_attachment: out of memory");
  		return 0;
  	}
  	superref->node.key = superref;
  	superref->s = super;
  	subref->node.key = subref;
  	subref->s = sub;
  	if(!rbtree_insert(&sub->super_set, &superref->node)) {
  		/* this should not happen, iterator and validator do not
  		 * attach subqueries that are identical. */
  		/* already attached, we are done, nothing todo.
  		 * since superref and subref already allocated in region,
  		 * we cannot free them */
  		return 1;
  	}
  #ifdef UNBOUND_DEBUG
  	n =
  #else
  	(void)
  #endif
  	rbtree_insert(&super->sub_set, &subref->node);
  	log_assert(n != NULL); /* we checked above if statement, the reverse
  	  administration should not fail now, unless they are out of sync */
  	return 1;
  }
  
  /**
   * callback results to mesh cb entry
   * @param m: mesh state to send it for.
   * @param rcode: if not 0, error code.
   * @param rep: reply to send (or NULL if rcode is set).
   * @param r: callback entry
   */
  static void
  mesh_do_callback(struct mesh_state* m, int rcode, struct reply_info* rep,
  	struct mesh_cb* r)
  {
  	int secure;
  	char* reason = NULL;
  	int was_ratelimited = m->s.was_ratelimited;
  	/* bogus messages are not made into servfail, sec_status passed
  	 * to the callback function */
  	if(rep && rep->security == sec_status_secure)
  		secure = 1;
  	else	secure = 0;
  	if(!rep && rcode == LDNS_RCODE_NOERROR)
  		rcode = LDNS_RCODE_SERVFAIL;
  	if(!rcode && (rep->security == sec_status_bogus ||
  		rep->security == sec_status_secure_sentinel_fail)) {
  		if(!(reason = errinf_to_str_bogus(&m->s)))
  			rcode = LDNS_RCODE_SERVFAIL;
  	}
  	/* send the reply */
  	if(rcode) {
  		if(rcode == LDNS_RCODE_SERVFAIL) {
  			if(!inplace_cb_reply_servfail_call(m->s.env, &m->s.qinfo, &m->s,
  				rep, rcode, &r->edns, NULL, m->s.region))
  					r->edns.opt_list = NULL;
  		} else {
  			if(!inplace_cb_reply_call(m->s.env, &m->s.qinfo, &m->s, rep, rcode,
  				&r->edns, NULL, m->s.region))
  					r->edns.opt_list = NULL;
  		}
  		fptr_ok(fptr_whitelist_mesh_cb(r->cb));
  		(*r->cb)(r->cb_arg, rcode, r->buf, sec_status_unchecked, NULL,
  			was_ratelimited);
  	} else {
  		size_t udp_size = r->edns.udp_size;
  		sldns_buffer_clear(r->buf);
  		r->edns.edns_version = EDNS_ADVERTISED_VERSION;
  		r->edns.udp_size = EDNS_ADVERTISED_SIZE;
  		r->edns.ext_rcode = 0;
  		r->edns.bits &= EDNS_DO;
  
  		if(!inplace_cb_reply_call(m->s.env, &m->s.qinfo, &m->s, rep,
  			LDNS_RCODE_NOERROR, &r->edns, NULL, m->s.region) ||
  			!reply_info_answer_encode(&m->s.qinfo, rep, r->qid, 
  			r->qflags, r->buf, 0, 1, 
  			m->s.env->scratch, udp_size, &r->edns, 
  			(int)(r->edns.bits & EDNS_DO), secure)) 
  		{
  			fptr_ok(fptr_whitelist_mesh_cb(r->cb));
  			(*r->cb)(r->cb_arg, LDNS_RCODE_SERVFAIL, r->buf,
  				sec_status_unchecked, NULL, 0);
  		} else {
  			fptr_ok(fptr_whitelist_mesh_cb(r->cb));
  			(*r->cb)(r->cb_arg, LDNS_RCODE_NOERROR, r->buf,
  				rep->security, reason, was_ratelimited);
  		}
  	}
  	free(reason);
  	log_assert(m->s.env->mesh->num_reply_addrs > 0);
  	m->s.env->mesh->num_reply_addrs--;
  }
  
  /**
   * Send reply to mesh reply entry
   * @param m: mesh state to send it for.
   * @param rcode: if not 0, error code.
   * @param rep: reply to send (or NULL if rcode is set).
   * @param r: reply entry
   * @param r_buffer: buffer to use for reply entry.
   * @param prev: previous reply, already has its answer encoded in buffer.
   * @param prev_buffer: buffer for previous reply.
   */
  static void
  mesh_send_reply(struct mesh_state* m, int rcode, struct reply_info* rep,
  	struct mesh_reply* r, struct sldns_buffer* r_buffer,
  	struct mesh_reply* prev, struct sldns_buffer* prev_buffer)
  {
  	struct timeval end_time;
  	struct timeval duration;
  	int secure;
  	/* Copy the client's EDNS for later restore, to make sure the edns
  	 * compare is with the correct edns options. */
  	struct edns_data edns_bak = r->edns;
  	/* briefly set the replylist to null in case the
  	 * meshsendreply calls tcpreqinfo sendreply that
  	 * comm_point_drops because of size, and then the
  	 * null stops the mesh state remove and thus
  	 * reply_list modification and accounting */
  	struct mesh_reply* rlist = m->reply_list;
  	/* examine security status */
  	if(m->s.env->need_to_validate && (!(r->qflags&BIT_CD) ||
  		m->s.env->cfg->ignore_cd) && rep && 
  		(rep->security <= sec_status_bogus ||
  		rep->security == sec_status_secure_sentinel_fail)) {
  		rcode = LDNS_RCODE_SERVFAIL;
  		if(m->s.env->cfg->stat_extended) 
  			m->s.env->mesh->ans_bogus++;
  	}
  	if(rep && rep->security == sec_status_secure)
  		secure = 1;
  	else	secure = 0;
  	if(!rep && rcode == LDNS_RCODE_NOERROR)
  		rcode = LDNS_RCODE_SERVFAIL;
  	if(r->query_reply.c->use_h2) {
  		r->query_reply.c->h2_stream = r->h2_stream;
  		/* Mesh reply won't exist for long anymore. Make it impossible
  		 * for HTTP/2 stream to refer to mesh state, in case
  		 * connection gets cleanup before HTTP/2 stream close. */
  		r->h2_stream->mesh_state = NULL;
  	}
  	/* send the reply */
  	/* We don't reuse the encoded answer if:
  	 * - either the previous or current response has a local alias.  We could
  	 *   compare the alias records and still reuse the previous answer if they
  	 *   are the same, but that would be complicated and error prone for the
  	 *   relatively minor case. So we err on the side of safety.
  	 * - there are registered callback functions for the given rcode, as these
  	 *   need to be called for each reply. */
  	if(((rcode != LDNS_RCODE_SERVFAIL &&
  			!m->s.env->inplace_cb_lists[inplace_cb_reply]) ||
  		(rcode == LDNS_RCODE_SERVFAIL &&
  			!m->s.env->inplace_cb_lists[inplace_cb_reply_servfail])) &&
  		prev && prev_buffer && prev->qflags == r->qflags &&
  		!prev->local_alias && !r->local_alias &&
  		prev->edns.edns_present == r->edns.edns_present &&
  		prev->edns.bits == r->edns.bits &&
  		prev->edns.udp_size == r->edns.udp_size &&
  		edns_opt_list_compare(prev->edns.opt_list, r->edns.opt_list)
  		== 0) {
  		/* if the previous reply is identical to this one, fix ID */
  		if(prev_buffer != r_buffer)
  			sldns_buffer_copy(r_buffer, prev_buffer);
  		sldns_buffer_write_at(r_buffer, 0, &r->qid, sizeof(uint16_t));
  		sldns_buffer_write_at(r_buffer, 12, r->qname,
  			m->s.qinfo.qname_len);
  		m->reply_list = NULL;
  		comm_point_send_reply(&r->query_reply);
  		m->reply_list = rlist;
  	} else if(rcode) {
  		m->s.qinfo.qname = r->qname;
  		m->s.qinfo.local_alias = r->local_alias;
  		if(rcode == LDNS_RCODE_SERVFAIL) {
  			if(!inplace_cb_reply_servfail_call(m->s.env, &m->s.qinfo, &m->s,
  				rep, rcode, &r->edns, &r->query_reply, m->s.region))
  					r->edns.opt_list = NULL;
  		} else { 
  			if(!inplace_cb_reply_call(m->s.env, &m->s.qinfo, &m->s, rep, rcode,
  				&r->edns, &r->query_reply, m->s.region))
  					r->edns.opt_list = NULL;
  		}
  		error_encode(r_buffer, rcode, &m->s.qinfo, r->qid,
  			r->qflags, &r->edns);
  		m->reply_list = NULL;
  		comm_point_send_reply(&r->query_reply);
  		m->reply_list = rlist;
  	} else {
  		size_t udp_size = r->edns.udp_size;
  		r->edns.edns_version = EDNS_ADVERTISED_VERSION;
  		r->edns.udp_size = EDNS_ADVERTISED_SIZE;
  		r->edns.ext_rcode = 0;
  		r->edns.bits &= EDNS_DO;
  		m->s.qinfo.qname = r->qname;
  		m->s.qinfo.local_alias = r->local_alias;
  		if(!inplace_cb_reply_call(m->s.env, &m->s.qinfo, &m->s, rep,
  			LDNS_RCODE_NOERROR, &r->edns, &r->query_reply, m->s.region) ||
  			!apply_edns_options(&r->edns, &edns_bak,
  				m->s.env->cfg, r->query_reply.c,
  				m->s.region) ||
  			!reply_info_answer_encode(&m->s.qinfo, rep, r->qid, 
  			r->qflags, r_buffer, 0, 1, m->s.env->scratch,
  			udp_size, &r->edns, (int)(r->edns.bits & EDNS_DO),
  			secure)) 
  		{
  			if(!inplace_cb_reply_servfail_call(m->s.env, &m->s.qinfo, &m->s,
  			rep, LDNS_RCODE_SERVFAIL, &r->edns, &r->query_reply, m->s.region))
  				r->edns.opt_list = NULL;
  			error_encode(r_buffer, LDNS_RCODE_SERVFAIL,
  				&m->s.qinfo, r->qid, r->qflags, &r->edns);
  		}
  		r->edns = edns_bak;
  		m->reply_list = NULL;
  		comm_point_send_reply(&r->query_reply);
  		m->reply_list = rlist;
  	}
  	/* account */
  	log_assert(m->s.env->mesh->num_reply_addrs > 0);
  	m->s.env->mesh->num_reply_addrs--;
  	end_time = *m->s.env->now_tv;
  	timeval_subtract(&duration, &end_time, &r->start_time);
  	verbose(VERB_ALGO, "query took " ARG_LL "d.%6.6d sec",
  		(long long)duration.tv_sec, (int)duration.tv_usec);
  	m->s.env->mesh->replies_sent++;
  	timeval_add(&m->s.env->mesh->replies_sum_wait, &duration);
  	timehist_insert(m->s.env->mesh->histogram, &duration);
  	if(m->s.env->cfg->stat_extended) {
  		uint16_t rc = FLAGS_GET_RCODE(sldns_buffer_read_u16_at(
  			r_buffer, 2));
  		if(secure) m->s.env->mesh->ans_secure++;
  		m->s.env->mesh->ans_rcode[ rc ] ++;
  		if(rc == 0 && LDNS_ANCOUNT(sldns_buffer_begin(r_buffer)) == 0)
  			m->s.env->mesh->ans_nodata++;
  	}
  	/* Log reply sent */
  	if(m->s.env->cfg->log_replies) {
  		log_reply_info(NO_VERBOSE, &m->s.qinfo, &r->query_reply.addr,
  			r->query_reply.addrlen, duration, 0, r_buffer);
  	}
  }
  
  void mesh_query_done(struct mesh_state* mstate)
  {
  	struct mesh_reply* r;
  	struct mesh_reply* prev = NULL;
  	struct sldns_buffer* prev_buffer = NULL;
  	struct mesh_cb* c;
  	struct reply_info* rep = (mstate->s.return_msg?
  		mstate->s.return_msg->rep:NULL);
  	/* No need for the serve expired timer anymore; we are going to reply. */
  	if(mstate->s.serve_expired_data) {
  		comm_timer_delete(mstate->s.serve_expired_data->timer);
  		mstate->s.serve_expired_data->timer = NULL;
  	}
  	if(mstate->s.return_rcode == LDNS_RCODE_SERVFAIL ||
  		(rep && FLAGS_GET_RCODE(rep->flags) == LDNS_RCODE_SERVFAIL)) {
  		/* we are SERVFAILing; check for expired asnwer here */
  		mesh_serve_expired_callback(mstate);
  		if((mstate->reply_list || mstate->cb_list)
  		&& mstate->s.env->cfg->log_servfail
  		&& !mstate->s.env->cfg->val_log_squelch) {
  			char* err = errinf_to_str_servfail(&mstate->s);
  			if(err)
  				log_err("%s", err);
  			free(err);
  		}
  	}
  	for(r = mstate->reply_list; r; r = r->next) {
  		/* if a response-ip address block has been stored the
  		 *  information should be logged for each client. */
  		if(mstate->s.respip_action_info &&
  			mstate->s.respip_action_info->addrinfo) {
  			respip_inform_print(mstate->s.respip_action_info,
  				r->qname, mstate->s.qinfo.qtype,
  				mstate->s.qinfo.qclass, r->local_alias,
  				&r->query_reply);
  			if(mstate->s.env->cfg->stat_extended &&
  				mstate->s.respip_action_info->rpz_used) {
  				if(mstate->s.respip_action_info->rpz_disabled)
  					mstate->s.env->mesh->rpz_action[RPZ_DISABLED_ACTION]++;
  				if(mstate->s.respip_action_info->rpz_cname_override)
  					mstate->s.env->mesh->rpz_action[RPZ_CNAME_OVERRIDE_ACTION]++;
  				else
  					mstate->s.env->mesh->rpz_action[respip_action_to_rpz_action(
  						mstate->s.respip_action_info->action)]++;
  			}
  		}
  
  		/* if this query is determined to be dropped during the
  		 * mesh processing, this is the point to take that action. */
  		if(mstate->s.is_drop) {
  			/* briefly set the reply_list to NULL, so that the
  			 * tcp req info cleanup routine that calls the mesh
  			 * to deregister the meshstate for it is not done
  			 * because the list is NULL and also accounting is not
  			 * done there, but instead we do that here. */
  			struct mesh_reply* reply_list = mstate->reply_list;
  			mstate->reply_list = NULL;
  			comm_point_drop_reply(&r->query_reply);
  			mstate->reply_list = reply_list;
  		} else {
  			struct sldns_buffer* r_buffer = r->query_reply.c->buffer;
  			if(r->query_reply.c->tcp_req_info) {
  				r_buffer = r->query_reply.c->tcp_req_info->spool_buffer;
  				prev_buffer = NULL;
  			}
  			mesh_send_reply(mstate, mstate->s.return_rcode, rep,
  				r, r_buffer, prev, prev_buffer);
  			if(r->query_reply.c->tcp_req_info) {
  				tcp_req_info_remove_mesh_state(r->query_reply.c->tcp_req_info, mstate);
  				r_buffer = NULL;
  			}
  			prev = r;
  			prev_buffer = r_buffer;
  		}
  	}
  	if(mstate->reply_list) {
  		mstate->reply_list = NULL;
  		if(!mstate->reply_list && !mstate->cb_list) {
  			/* was a reply state, not anymore */
  			log_assert(mstate->s.env->mesh->num_reply_states > 0);
  			mstate->s.env->mesh->num_reply_states--;
  		}
  		if(!mstate->reply_list && !mstate->cb_list &&
  			mstate->super_set.count == 0)
  			mstate->s.env->mesh->num_detached_states++;
  	}
  	mstate->replies_sent = 1;
  	while((c = mstate->cb_list) != NULL) {
  		/* take this cb off the list; so that the list can be
  		 * changed, eg. by adds from the callback routine */
  		if(!mstate->reply_list && mstate->cb_list && !c->next) {
  			/* was a reply state, not anymore */
  			log_assert(mstate->s.env->mesh->num_reply_states > 0);
  			mstate->s.env->mesh->num_reply_states--;
  		}
  		mstate->cb_list = c->next;
  		if(!mstate->reply_list && !mstate->cb_list &&
  			mstate->super_set.count == 0)
  			mstate->s.env->mesh->num_detached_states++;
  		mesh_do_callback(mstate, mstate->s.return_rcode, rep, c);
  	}
  }
  
  void mesh_walk_supers(struct mesh_area* mesh, struct mesh_state* mstate)
  {
  	struct mesh_state_ref* ref;
  	RBTREE_FOR(ref, struct mesh_state_ref*, &mstate->super_set)
  	{
  		/* make super runnable */
  		(void)rbtree_insert(&mesh->run, &ref->s->run_node);
  		/* callback the function to inform super of result */
  		fptr_ok(fptr_whitelist_mod_inform_super(
  			mesh->mods.mod[ref->s->s.curmod]->inform_super));
  		(*mesh->mods.mod[ref->s->s.curmod]->inform_super)(&mstate->s, 
  			ref->s->s.curmod, &ref->s->s);
  		/* copy state that is always relevant to super */
  		copy_state_to_super(&mstate->s, ref->s->s.curmod, &ref->s->s);
  	}
  }
  
  struct mesh_state* mesh_area_find(struct mesh_area* mesh,
  	struct respip_client_info* cinfo, struct query_info* qinfo,
  	uint16_t qflags, int prime, int valrec)
  {
  	struct mesh_state key;
  	struct mesh_state* result;
  
  	key.node.key = &key;
  	key.s.is_priming = prime;
  	key.s.is_valrec = valrec;
  	key.s.qinfo = *qinfo;
  	key.s.query_flags = qflags;
  	/* We are searching for a similar mesh state when we DO want to
  	 * aggregate the state. Thus unique is set to NULL. (default when we
  	 * desire aggregation).*/
  	key.unique = NULL;
  	key.s.client_info = cinfo;
  	
  	result = (struct mesh_state*)rbtree_search(&mesh->all, &key);
  	return result;
  }
  
  int mesh_state_add_cb(struct mesh_state* s, struct edns_data* edns,
          sldns_buffer* buf, mesh_cb_func_type cb, void* cb_arg,
  	uint16_t qid, uint16_t qflags)
  {
  	struct mesh_cb* r = regional_alloc(s->s.region, 
  		sizeof(struct mesh_cb));
  	if(!r)
  		return 0;
  	r->buf = buf;
  	log_assert(fptr_whitelist_mesh_cb(cb)); /* early failure ifmissing*/
  	r->cb = cb;
  	r->cb_arg = cb_arg;
  	r->edns = *edns;
  	if(edns->opt_list) {
  		r->edns.opt_list = edns_opt_copy_region(edns->opt_list,
  			s->s.region);
  		if(!r->edns.opt_list)
  			return 0;
  	}
  	r->qid = qid;
  	r->qflags = qflags;
  	r->next = s->cb_list;
  	s->cb_list = r;
  	return 1;
  
  }
  
  int mesh_state_add_reply(struct mesh_state* s, struct edns_data* edns,
          struct comm_reply* rep, uint16_t qid, uint16_t qflags,
          const struct query_info* qinfo)
  {
  	struct mesh_reply* r = regional_alloc(s->s.region, 
  		sizeof(struct mesh_reply));
  	if(!r)
  		return 0;
  	r->query_reply = *rep;
  	r->edns = *edns;
  	if(edns->opt_list) {
  		r->edns.opt_list = edns_opt_copy_region(edns->opt_list,
  			s->s.region);
  		if(!r->edns.opt_list)
  			return 0;
  	}
  	r->qid = qid;
  	r->qflags = qflags;
  	r->start_time = *s->s.env->now_tv;
  	r->next = s->reply_list;
  	r->qname = regional_alloc_init(s->s.region, qinfo->qname,
  		s->s.qinfo.qname_len);
  	if(!r->qname)
  		return 0;
  	if(rep->c->use_h2)
  		r->h2_stream = rep->c->h2_stream;
  
  	/* Data related to local alias stored in 'qinfo' (if any) is ephemeral
  	 * and can be different for different original queries (even if the
  	 * replaced query name is the same).  So we need to make a deep copy
  	 * and store the copy for each reply info. */
  	if(qinfo->local_alias) {
  		struct packed_rrset_data* d;
  		struct packed_rrset_data* dsrc;
  		r->local_alias = regional_alloc_zero(s->s.region,
  			sizeof(*qinfo->local_alias));
  		if(!r->local_alias)
  			return 0;
  		r->local_alias->rrset = regional_alloc_init(s->s.region,
  			qinfo->local_alias->rrset,
  			sizeof(*qinfo->local_alias->rrset));
  		if(!r->local_alias->rrset)
  			return 0;
  		dsrc = qinfo->local_alias->rrset->entry.data;
  
  		/* In the current implementation, a local alias must be
  		 * a single CNAME RR (see worker_handle_request()). */
  		log_assert(!qinfo->local_alias->next && dsrc->count == 1 &&
  			qinfo->local_alias->rrset->rk.type ==
  			htons(LDNS_RR_TYPE_CNAME));
  		/* we should make a local copy for the owner name of
  		 * the RRset */
  		r->local_alias->rrset->rk.dname_len =
  			qinfo->local_alias->rrset->rk.dname_len;
  		r->local_alias->rrset->rk.dname = regional_alloc_init(
  			s->s.region, qinfo->local_alias->rrset->rk.dname,
  			qinfo->local_alias->rrset->rk.dname_len);
  		if(!r->local_alias->rrset->rk.dname)
  			return 0;
  
  		/* the rrset is not packed, like in the cache, but it is
  		 * individualy allocated with an allocator from localzone. */
  		d = regional_alloc_zero(s->s.region, sizeof(*d));
  		if(!d)
  			return 0;
  		r->local_alias->rrset->entry.data = d;
  		if(!rrset_insert_rr(s->s.region, d, dsrc->rr_data[0],
  			dsrc->rr_len[0], dsrc->rr_ttl[0], "CNAME local alias"))
  			return 0;
  	} else
  		r->local_alias = NULL;
  
  	s->reply_list = r;
  	return 1;
  }
  
  /* Extract the query info and flags from 'mstate' into '*qinfop' and '*qflags'.
   * Since this is only used for internal refetch of otherwise-expired answer,
   * we simply ignore the rare failure mode when memory allocation fails. */
  static void
  mesh_copy_qinfo(struct mesh_state* mstate, struct query_info** qinfop,
  	uint16_t* qflags)
  {
  	struct regional* region = mstate->s.env->scratch;
  	struct query_info* qinfo;
  
  	qinfo = regional_alloc_init(region, &mstate->s.qinfo, sizeof(*qinfo));
  	if(!qinfo)
  		return;
  	qinfo->qname = regional_alloc_init(region, qinfo->qname,
  		qinfo->qname_len);
  	if(!qinfo->qname)
  		return;
  	*qinfop = qinfo;
  	*qflags = mstate->s.query_flags;
  }
  
  /**
   * Continue processing the mesh state at another module.
   * Handles module to modules transfer of control.
   * Handles module finished.
   * @param mesh: the mesh area.
   * @param mstate: currently active mesh state.
   * 	Deleted if finished, calls _done and _supers to 
   * 	send replies to clients and inform other mesh states.
   * 	This in turn may create additional runnable mesh states.
   * @param s: state at which the current module exited.
   * @param ev: the event sent to the module.
   * 	returned is the event to send to the next module.
   * @return true if continue processing at the new module.
   * 	false if not continued processing is needed.
   */
  static int
  mesh_continue(struct mesh_area* mesh, struct mesh_state* mstate,
  	enum module_ext_state s, enum module_ev* ev)
  {
  	mstate->num_activated++;
  	if(mstate->num_activated > MESH_MAX_ACTIVATION) {
  		/* module is looping. Stop it. */
  		log_err("internal error: looping module (%s) stopped",
  			mesh->mods.mod[mstate->s.curmod]->name);
  		log_query_info(NO_VERBOSE, "pass error for qstate",
  			&mstate->s.qinfo);
  		s = module_error;
  	}
  	if(s == module_wait_module || s == module_restart_next) {
  		/* start next module */
  		mstate->s.curmod++;
  		if(mesh->mods.num == mstate->s.curmod) {
  			log_err("Cannot pass to next module; at last module");
  			log_query_info(VERB_QUERY, "pass error for qstate",
  				&mstate->s.qinfo);
  			mstate->s.curmod--;
  			return mesh_continue(mesh, mstate, module_error, ev);
  		}
  		if(s == module_restart_next) {
  			int curmod = mstate->s.curmod;
  			for(; mstate->s.curmod < mesh->mods.num; 
  				mstate->s.curmod++) {
  				fptr_ok(fptr_whitelist_mod_clear(
  					mesh->mods.mod[mstate->s.curmod]->clear));
  				(*mesh->mods.mod[mstate->s.curmod]->clear)
  					(&mstate->s, mstate->s.curmod);
  				mstate->s.minfo[mstate->s.curmod] = NULL;
  			}
  			mstate->s.curmod = curmod;
  		}
  		*ev = module_event_pass;
  		return 1;
  	}
  	if(s == module_wait_subquery && mstate->sub_set.count == 0) {
  		log_err("module cannot wait for subquery, subquery list empty");
  		log_query_info(VERB_QUERY, "pass error for qstate",
  			&mstate->s.qinfo);
  		s = module_error;
  	}
  	if(s == module_error && mstate->s.return_rcode == LDNS_RCODE_NOERROR) {
  		/* error is bad, handle pass back up below */
  		mstate->s.return_rcode = LDNS_RCODE_SERVFAIL;
  	}
  	if(s == module_error) {
  		mesh_query_done(mstate);
  		mesh_walk_supers(mesh, mstate);
  		mesh_state_delete(&mstate->s);
  		return 0;
  	}
  	if(s == module_finished) {
  		if(mstate->s.curmod == 0) {
  			struct query_info* qinfo = NULL;
  			uint16_t qflags;
  
  			mesh_query_done(mstate);
  			mesh_walk_supers(mesh, mstate);
  
  			/* If the answer to the query needs to be refetched
  			 * from an external DNS server, we'll need to schedule
  			 * a prefetch after removing the current state, so
  			 * we need to make a copy of the query info here. */
  			if(mstate->s.need_refetch)
  				mesh_copy_qinfo(mstate, &qinfo, &qflags);
  
  			mesh_state_delete(&mstate->s);
  			if(qinfo) {
  				mesh_schedule_prefetch(mesh, qinfo, qflags,
  					0, 1);
  			}
  			return 0;
  		}
  		/* pass along the locus of control */
  		mstate->s.curmod --;
  		*ev = module_event_moddone;
  		return 1;
  	}
  	return 0;
  }
  
  void mesh_run(struct mesh_area* mesh, struct mesh_state* mstate,
  	enum module_ev ev, struct outbound_entry* e)
  {
  	enum module_ext_state s;
  	verbose(VERB_ALGO, "mesh_run: start");
  	while(mstate) {
  		/* run the module */
  		fptr_ok(fptr_whitelist_mod_operate(
  			mesh->mods.mod[mstate->s.curmod]->operate));
  		(*mesh->mods.mod[mstate->s.curmod]->operate)
  			(&mstate->s, ev, mstate->s.curmod, e);
  
  		/* examine results */
  		mstate->s.reply = NULL;
  		regional_free_all(mstate->s.env->scratch);
  		s = mstate->s.ext_state[mstate->s.curmod];
  		verbose(VERB_ALGO, "mesh_run: %s module exit state is %s", 
  			mesh->mods.mod[mstate->s.curmod]->name, strextstate(s));
  		e = NULL;
  		if(mesh_continue(mesh, mstate, s, &ev))
  			continue;
  
  		/* run more modules */
  		ev = module_event_pass;
  		if(mesh->run.count > 0) {
  			/* pop random element off the runnable tree */
  			mstate = (struct mesh_state*)mesh->run.root->key;
  			(void)rbtree_delete(&mesh->run, mstate);
  		} else mstate = NULL;
  	}
  	if(verbosity >= VERB_ALGO) {
  		mesh_stats(mesh, "mesh_run: end");
  		mesh_log_list(mesh);
  	}
  }
  
  void 
  mesh_log_list(struct mesh_area* mesh)
  {
  	char buf[30];
  	struct mesh_state* m;
  	int num = 0;
  	RBTREE_FOR(m, struct mesh_state*, &mesh->all) {
  		snprintf(buf, sizeof(buf), "%d%s%s%s%s%s%s mod%d %s%s", 
  			num++, (m->s.is_priming)?"p":"",  /* prime */
  			(m->s.is_valrec)?"v":"",  /* prime */
  			(m->s.query_flags&BIT_RD)?"RD":"",
  			(m->s.query_flags&BIT_CD)?"CD":"",
  			(m->super_set.count==0)?"d":"", /* detached */
  			(m->sub_set.count!=0)?"c":"",  /* children */
  			m->s.curmod, (m->reply_list)?"rep":"", /*hasreply*/
  			(m->cb_list)?"cb":"" /* callbacks */
  			); 
  		log_query_info(VERB_ALGO, buf, &m->s.qinfo);
  	}
  }
  
  void 
  mesh_stats(struct mesh_area* mesh, const char* str)
  {
  	verbose(VERB_DETAIL, "%s %u recursion states (%u with reply, "
  		"%u detached), %u waiting replies, %u recursion replies "
  		"sent, %d replies dropped, %d states jostled out", 
  		str, (unsigned)mesh->all.count, 
  		(unsigned)mesh->num_reply_states,
  		(unsigned)mesh->num_detached_states,
  		(unsigned)mesh->num_reply_addrs,
  		(unsigned)mesh->replies_sent,
  		(unsigned)mesh->stats_dropped,
  		(unsigned)mesh->stats_jostled);
  	if(mesh->replies_sent > 0) {
  		struct timeval avg;
  		timeval_divide(&avg, &mesh->replies_sum_wait, 
  			mesh->replies_sent);
  		log_info("average recursion processing time "
  			ARG_LL "d.%6.6d sec",
  			(long long)avg.tv_sec, (int)avg.tv_usec);
  		log_info("histogram of recursion processing times");
  		timehist_log(mesh->histogram, "recursions");
  	}
  }
  
  void 
  mesh_stats_clear(struct mesh_area* mesh)
  {
  	if(!mesh)
  		return;
  	mesh->replies_sent = 0;
  	mesh->replies_sum_wait.tv_sec = 0;
  	mesh->replies_sum_wait.tv_usec = 0;
  	mesh->stats_jostled = 0;
  	mesh->stats_dropped = 0;
  	timehist_clear(mesh->histogram);
  	mesh->ans_secure = 0;
  	mesh->ans_bogus = 0;
  	mesh->ans_expired = 0;
  	memset(&mesh->ans_rcode[0], 0, sizeof(size_t)*UB_STATS_RCODE_NUM);
  	memset(&mesh->rpz_action[0], 0, sizeof(size_t)*UB_STATS_RPZ_ACTION_NUM);
  	mesh->ans_nodata = 0;
  }
  
  size_t 
  mesh_get_mem(struct mesh_area* mesh)
  {
  	struct mesh_state* m;
  	size_t s = sizeof(*mesh) + sizeof(struct timehist) +
  		sizeof(struct th_buck)*mesh->histogram->num +
  		sizeof(sldns_buffer) + sldns_buffer_capacity(mesh->qbuf_bak);
  	RBTREE_FOR(m, struct mesh_state*, &mesh->all) {
  		/* all, including m itself allocated in qstate region */
  		s += regional_get_mem(m->s.region);
  	}
  	return s;
  }
  
  int 
  mesh_detect_cycle(struct module_qstate* qstate, struct query_info* qinfo,
  	uint16_t flags, int prime, int valrec)
  {
  	struct mesh_area* mesh = qstate->env->mesh;
  	struct mesh_state* dep_m = NULL;
  	if(!mesh_state_is_unique(qstate->mesh_info))
  		dep_m = mesh_area_find(mesh, NULL, qinfo, flags, prime, valrec);
  	return mesh_detect_cycle_found(qstate, dep_m);
  }
  
  void mesh_list_insert(struct mesh_state* m, struct mesh_state** fp,
          struct mesh_state** lp)
  {
  	/* insert as last element */
  	m->prev = *lp;
  	m->next = NULL;
  	if(*lp)
  		(*lp)->next = m;
  	else	*fp = m;
  	*lp = m;
  }
  
  void mesh_list_remove(struct mesh_state* m, struct mesh_state** fp,
          struct mesh_state** lp)
  {
  	if(m->next)
  		m->next->prev = m->prev;
  	else	*lp = m->prev;
  	if(m->prev)
  		m->prev->next = m->next;
  	else	*fp = m->next;
  }
  
  void mesh_state_remove_reply(struct mesh_area* mesh, struct mesh_state* m,
  	struct comm_point* cp)
  {
  	struct mesh_reply* n, *prev = NULL;
  	n = m->reply_list;
  	/* when in mesh_cleanup, it sets the reply_list to NULL, so that
  	 * there is no accounting twice */
  	if(!n) return; /* nothing to remove, also no accounting needed */
  	while(n) {
  		if(n->query_reply.c == cp) {
  			/* unlink it */
  			if(prev) prev->next = n->next;
  			else m->reply_list = n->next;
  			/* delete it, but allocated in m region */
  			log_assert(mesh->num_reply_addrs > 0);
  			mesh->num_reply_addrs--;
  
  			/* prev = prev; */
  			n = n->next;
  			continue;
  		}
  		prev = n;
  		n = n->next;
  	}
  	/* it was not detached (because it had a reply list), could be now */
  	if(!m->reply_list && !m->cb_list
  		&& m->super_set.count == 0) {
  		mesh->num_detached_states++;
  	}
  	/* if not replies any more in mstate, it is no longer a reply_state */
  	if(!m->reply_list && !m->cb_list) {
  		log_assert(mesh->num_reply_states > 0);
  		mesh->num_reply_states--;
  	}
  }
  
  
  static int
  apply_respip_action(struct module_qstate* qstate,
  	const struct query_info* qinfo, struct respip_client_info* cinfo,
  	struct respip_action_info* actinfo, struct reply_info* rep,
  	struct ub_packed_rrset_key** alias_rrset,
  	struct reply_info** encode_repp, struct auth_zones* az)
  {
  	if(qinfo->qtype != LDNS_RR_TYPE_A &&
  		qinfo->qtype != LDNS_RR_TYPE_AAAA &&
  		qinfo->qtype != LDNS_RR_TYPE_ANY)
  		return 1;
  
  	if(!respip_rewrite_reply(qinfo, cinfo, rep, encode_repp, actinfo,
  		alias_rrset, 0, qstate->region, az))
  		return 0;
  
  	/* xxx_deny actions mean dropping the reply, unless the original reply
  	 * was redirected to response-ip data. */
  	if((actinfo->action == respip_deny ||
  		actinfo->action == respip_inform_deny) &&
  		*encode_repp == rep)
  		*encode_repp = NULL;
  
  	return 1;
  }
  
  void
  mesh_serve_expired_callback(void* arg)
  {
  	struct mesh_state* mstate = (struct mesh_state*) arg;
  	struct module_qstate* qstate = &mstate->s;
  	struct mesh_reply* r;
  	struct mesh_area* mesh = qstate->env->mesh;
  	struct dns_msg* msg;
  	struct mesh_cb* c;
  	struct mesh_reply* prev = NULL;
  	struct sldns_buffer* prev_buffer = NULL;
  	struct sldns_buffer* r_buffer = NULL;
  	struct reply_info* partial_rep = NULL;
  	struct ub_packed_rrset_key* alias_rrset = NULL;
  	struct reply_info* encode_rep = NULL;
  	struct respip_action_info actinfo;
  	struct query_info* lookup_qinfo = &qstate->qinfo;
  	struct query_info qinfo_tmp;
  	int must_validate = (!(qstate->query_flags&BIT_CD)
  		|| qstate->env->cfg->ignore_cd) && qstate->env->need_to_validate;
  	if(!qstate->serve_expired_data) return;
  	verbose(VERB_ALGO, "Serve expired: Trying to reply with expired data");
  	comm_timer_delete(qstate->serve_expired_data->timer);
  	qstate->serve_expired_data->timer = NULL;
  	if(qstate->blacklist || qstate->no_cache_lookup || qstate->is_drop) {
  		verbose(VERB_ALGO,
  			"Serve expired: Not allowed to look into cache for stale");
  		return;
  	}
  	/* The following while is used instead of the `goto lookup_cache`
  	 * like in the worker. */
  	while(1) {
  		fptr_ok(fptr_whitelist_serve_expired_lookup(
  			qstate->serve_expired_data->get_cached_answer));
  		msg = qstate->serve_expired_data->get_cached_answer(qstate,
  			lookup_qinfo);
  		if(!msg)
  			return;
  		/* Reset these in case we pass a second time from here. */
  		encode_rep = msg->rep;
  		memset(&actinfo, 0, sizeof(actinfo));
  		actinfo.action = respip_none;
  		alias_rrset = NULL;
  		if((mesh->use_response_ip || mesh->use_rpz) &&
  			!partial_rep && !apply_respip_action(qstate, &qstate->qinfo,
  			qstate->client_info, &actinfo, msg->rep, &alias_rrset, &encode_rep,
  			qstate->env->auth_zones)) {
  			return;
  		} else if(partial_rep &&
  			!respip_merge_cname(partial_rep, &qstate->qinfo, msg->rep,
  			qstate->client_info, must_validate, &encode_rep, qstate->region,
  			qstate->env->auth_zones)) {
  			return;
  		}
  		if(!encode_rep || alias_rrset) {
  			if(!encode_rep) {
  				/* Needs drop */
  				return;
  			} else {
  				/* A partial CNAME chain is found. */
  				partial_rep = encode_rep;
  			}
  		}
  		/* We've found a partial reply ending with an
  		* alias.  Replace the lookup qinfo for the
  		* alias target and lookup the cache again to
  		* (possibly) complete the reply.  As we're
  		* passing the "base" reply, there will be no
  		* more alias chasing. */
  		if(partial_rep) {
  			memset(&qinfo_tmp, 0, sizeof(qinfo_tmp));
  			get_cname_target(alias_rrset, &qinfo_tmp.qname,
  				&qinfo_tmp.qname_len);
  			if(!qinfo_tmp.qname) {
  				log_err("Serve expired: unexpected: invalid answer alias");
  				return;
  			}
  			qinfo_tmp.qtype = qstate->qinfo.qtype;
  			qinfo_tmp.qclass = qstate->qinfo.qclass;
  			lookup_qinfo = &qinfo_tmp;
  			continue;
  		}
  		break;
  	}
  
  	if(verbosity >= VERB_ALGO)
  		log_dns_msg("Serve expired lookup", &qstate->qinfo, msg->rep);
  
  	for(r = mstate->reply_list; r; r = r->next) {
  		/* If address info is returned, it means the action should be an
  		* 'inform' variant and the information should be logged. */
  		if(actinfo.addrinfo) {
  			respip_inform_print(&actinfo, r->qname,
  				qstate->qinfo.qtype, qstate->qinfo.qclass,
  				r->local_alias, &r->query_reply);
  
  			if(qstate->env->cfg->stat_extended && actinfo.rpz_used) {
  				if(actinfo.rpz_disabled)
  					qstate->env->mesh->rpz_action[RPZ_DISABLED_ACTION]++;
  				if(actinfo.rpz_cname_override)
  					qstate->env->mesh->rpz_action[RPZ_CNAME_OVERRIDE_ACTION]++;
  				else
  					qstate->env->mesh->rpz_action[
  						respip_action_to_rpz_action(actinfo.action)]++;
  			}
  		}
  
  		r_buffer = r->query_reply.c->buffer;
  		if(r->query_reply.c->tcp_req_info)
  			r_buffer = r->query_reply.c->tcp_req_info->spool_buffer;
  		mesh_send_reply(mstate, LDNS_RCODE_NOERROR, msg->rep,
  			r, r_buffer, prev, prev_buffer);
  		if(r->query_reply.c->tcp_req_info)
  			tcp_req_info_remove_mesh_state(r->query_reply.c->tcp_req_info, mstate);
  		prev = r;
  		prev_buffer = r_buffer;
  
  		/* Account for each reply sent. */
  		mesh->ans_expired++;
  
  	}
  	if(mstate->reply_list) {
  		mstate->reply_list = NULL;
  		if(!mstate->reply_list && !mstate->cb_list) {
  			log_assert(mesh->num_reply_states > 0);
  			mesh->num_reply_states--;
  			if(mstate->super_set.count == 0) {
  				mesh->num_detached_states++;
  			}
  		}
  	}
  	while((c = mstate->cb_list) != NULL) {
  		/* take this cb off the list; so that the list can be
  		 * changed, eg. by adds from the callback routine */
  		if(!mstate->reply_list && mstate->cb_list && !c->next) {
  			/* was a reply state, not anymore */
  			log_assert(qstate->env->mesh->num_reply_states > 0);
  			qstate->env->mesh->num_reply_states--;
  		}
  		mstate->cb_list = c->next;
  		if(!mstate->reply_list && !mstate->cb_list &&
  			mstate->super_set.count == 0)
  			qstate->env->mesh->num_detached_states++;
  		mesh_do_callback(mstate, LDNS_RCODE_NOERROR, msg->rep, c);
  	}
  }
  