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iterator.c

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/*
 * iterator/iterator.c - iterative resolver DNS query response module
 *
 * 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 REGENTS 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 a module that performs recusive iterative DNS query
 * processing.
 */

#include "config.h"
#include "iterator/iterator.h"
#include "iterator/iter_utils.h"
#include "iterator/iter_hints.h"
#include "iterator/iter_fwd.h"
#include "iterator/iter_donotq.h"
#include "iterator/iter_delegpt.h"
#include "iterator/iter_resptype.h"
#include "iterator/iter_scrub.h"
#include "services/cache/dns.h"
#include "services/cache/infra.h"
#include "util/module.h"
#include "util/netevent.h"
#include "util/net_help.h"
#include "util/regional.h"
#include "util/data/dname.h"
#include "util/data/msgencode.h"
#include "util/fptr_wlist.h"

int 
00063 iter_init(struct module_env* env, int id)
{
      struct iter_env* iter_env = (struct iter_env*)calloc(1,
            sizeof(struct iter_env));
      if(!iter_env) {
            log_err("malloc failure");
            return 0;
      }
      env->modinfo[id] = (void*)iter_env;
      if(!iter_apply_cfg(iter_env, env->cfg)) {
            log_err("iterator: could not apply configuration settings.");
            return 0;
      }
      return 1;
}

void 
00080 iter_deinit(struct module_env* env, int id)
{
      struct iter_env* iter_env;
      if(!env || !env->modinfo[id])
            return;
      iter_env = (struct iter_env*)env->modinfo[id];
      free(iter_env->target_fetch_policy);
      hints_delete(iter_env->hints);
      forwards_delete(iter_env->fwds);
      donotq_delete(iter_env->donotq);
      free(iter_env);
      env->modinfo[id] = NULL;
}

/** new query for iterator */
static int
00096 iter_new(struct module_qstate* qstate, int id)
{
      struct iter_qstate* iq = (struct iter_qstate*)regional_alloc(
            qstate->region, sizeof(struct iter_qstate));
      qstate->minfo[id] = iq;
      if(!iq) 
            return 0;
      memset(iq, 0, sizeof(*iq));
      iq->state = INIT_REQUEST_STATE;
      iq->final_state = FINISHED_STATE;
      iq->an_prepend_list = NULL;
      iq->an_prepend_last = NULL;
      iq->ns_prepend_list = NULL;
      iq->ns_prepend_last = NULL;
      iq->dp = NULL;
      iq->depth = 0;
      iq->num_target_queries = 0;
      iq->num_current_queries = 0;
      iq->query_restart_count = 0;
      iq->referral_count = 0;
      iq->wait_priming_stub = 0;
      iq->refetch_glue = 0;
      iq->dnssec_expected = 0;
      iq->chase_flags = qstate->query_flags;
      /* Start with the (current) qname. */
      iq->qchase = qstate->qinfo;
      outbound_list_init(&iq->outlist);
      return 1;
}

/**
 * Transition to the next state. This can be used to advance a currently
 * processing event. It cannot be used to reactivate a forEvent.
 *
 * @param iq: iterator query state
 * @param nextstate The state to transition to.
 * @return true. This is so this can be called as the return value for the
 *         actual process*State() methods. (Transitioning to the next state
 *         implies further processing).
 */
static int
00137 next_state(struct iter_qstate* iq, enum iter_state nextstate)
{
      /* If transitioning to a "response" state, make sure that there is a
       * response */
      if(iter_state_is_responsestate(nextstate)) {
            if(iq->response == NULL) {
                  log_err("transitioning to response state sans "
                        "response.");
            }
      }
      iq->state = nextstate;
      return 1;
}

/**
 * Transition an event to its final state. Final states always either return
 * a result up the module chain, or reactivate a dependent event. Which
 * final state to transtion to is set in the module state for the event when
 * it was created, and depends on the original purpose of the event.
 *
 * The response is stored in the qstate->buf buffer.
 *
 * @param iq: iterator query state
 * @return false. This is so this method can be used as the return value for
 *         the processState methods. (Transitioning to the final state
 */
static int
00164 final_state(struct iter_qstate* iq)
{
      return next_state(iq, iq->final_state);
}

/**
 * Callback routine to handle errors in parent query states
 * @param qstate: query state that failed.
 * @param id: module id.
 * @param super: super state.
 */
static void
00176 error_supers(struct module_qstate* qstate, int id, struct module_qstate* super)
{
      struct iter_qstate* super_iq = (struct iter_qstate*)super->minfo[id];

      if(qstate->qinfo.qtype == LDNS_RR_TYPE_A ||
            qstate->qinfo.qtype == LDNS_RR_TYPE_AAAA) {
            /* mark address as failed. */
            struct delegpt_ns* dpns = NULL;
            if(super_iq->dp)
                  dpns = delegpt_find_ns(super_iq->dp, 
                        qstate->qinfo.qname, qstate->qinfo.qname_len);
            if(!dpns) {
                  /* not interested */
                  verbose(VERB_ALGO, "subq error, but not interested");
                  log_query_info(VERB_ALGO, "superq", &super->qinfo);
                  if(super_iq->dp)
                        delegpt_log(VERB_ALGO, super_iq->dp);
                  log_assert(0);
                  return;
            }
            dpns->resolved = 1; /* mark as failed */
            super_iq->num_target_queries--; 
      }
      if(qstate->qinfo.qtype == LDNS_RR_TYPE_NS) {
            /* prime failed to get delegation */
            super_iq->dp = NULL;
      }
      /* evaluate targets again */
      super_iq->state = QUERYTARGETS_STATE; 
      /* super becomes runnable, and will process this change */
}

/**
 * Return an error to the client
 * @param qstate: our query state
 * @param id: module id
 * @param rcode: error code (DNS errcode).
 * @return: 0 for use by caller, to make notation easy, like:
 *    return error_response(..). 
 */
static int
00217 error_response(struct module_qstate* qstate, int id, int rcode)
{
      verbose(VERB_QUERY, "return error response %s", 
            ldns_lookup_by_id(ldns_rcodes, rcode)?
            ldns_lookup_by_id(ldns_rcodes, rcode)->name:"??");
      qstate->return_rcode = rcode;
      qstate->return_msg = NULL;
      qstate->ext_state[id] = module_finished;
      return 0;
}

/** check if prepend item is duplicate item */
static int
00230 prepend_is_duplicate(struct ub_packed_rrset_key** sets, size_t to,
      struct ub_packed_rrset_key* dup)
{
      size_t i;
      for(i=0; i<to; i++) {
            if(sets[i]->rk.type == dup->rk.type &&
                  sets[i]->rk.rrset_class == dup->rk.rrset_class &&
                  sets[i]->rk.dname_len == dup->rk.dname_len &&
                  query_dname_compare(sets[i]->rk.dname, dup->rk.dname)
                  == 0)
                  return 1;
      }
      return 0;
}

/** prepend the prepend list in the answer and authority section of dns_msg */
static int
00247 iter_prepend(struct iter_qstate* iq, struct dns_msg* msg, 
      struct regional* region)
{
      struct iter_prep_list* p;
      struct ub_packed_rrset_key** sets;
      size_t num_an = 0, num_ns = 0;;
      for(p = iq->an_prepend_list; p; p = p->next)
            num_an++;
      for(p = iq->ns_prepend_list; p; p = p->next)
            num_ns++;
      if(num_an + num_ns == 0)
            return 1;
      verbose(VERB_ALGO, "prepending %d rrsets", (int)num_an + (int)num_ns);
      sets = regional_alloc(region, (num_an+num_ns+msg->rep->rrset_count) *
            sizeof(struct ub_packed_rrset_key*));
      if(!sets) 
            return 0;
      /* ANSWER section */
      num_an = 0;
      for(p = iq->an_prepend_list; p; p = p->next) {
            sets[num_an++] = p->rrset;
      }
      memcpy(sets+num_an, msg->rep->rrsets, msg->rep->an_numrrsets *
            sizeof(struct ub_packed_rrset_key*));
      /* AUTH section */
      num_ns = 0;
      for(p = iq->ns_prepend_list; p; p = p->next) {
            if(prepend_is_duplicate(sets+msg->rep->an_numrrsets+num_an,
                  num_ns, p->rrset) || prepend_is_duplicate(
                  msg->rep->rrsets+msg->rep->an_numrrsets, 
                  msg->rep->ns_numrrsets, p->rrset))
                  continue;
            sets[msg->rep->an_numrrsets + num_an + num_ns++] = p->rrset;
      }
      memcpy(sets + num_an + msg->rep->an_numrrsets + num_ns, 
            msg->rep->rrsets + msg->rep->an_numrrsets, 
            (msg->rep->ns_numrrsets + msg->rep->ar_numrrsets) *
            sizeof(struct ub_packed_rrset_key*));

      /* if the rcode was NXDOMAIN, and we prepended DNAME/CNAMEs, then
       * it should now be NOERROR. */
      if(FLAGS_GET_RCODE(msg->rep->flags) == LDNS_RCODE_NXDOMAIN) {
            FLAGS_SET_RCODE(msg->rep->flags, LDNS_RCODE_NOERROR);
      }
      msg->rep->rrset_count += num_an + num_ns;
      msg->rep->an_numrrsets += num_an;
      msg->rep->ns_numrrsets += num_ns;
      msg->rep->rrsets = sets;
      return 1;
}

/**
 * Add rrset to ANSWER prepend list
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param rrset: rrset to add.
 * @return false on failure (malloc).
 */
static int
00306 iter_add_prepend_answer(struct module_qstate* qstate, struct iter_qstate* iq,
      struct ub_packed_rrset_key* rrset)
{
      struct iter_prep_list* p = (struct iter_prep_list*)regional_alloc(
            qstate->region, sizeof(struct iter_prep_list));
      if(!p)
            return 0;
      p->rrset = rrset;
      p->next = NULL;
      /* add at end */
      if(iq->an_prepend_last)
            iq->an_prepend_last->next = p;
      else  iq->an_prepend_list = p;
      iq->an_prepend_last = p;
      return 1;
}

/**
 * Add rrset to AUTHORITY prepend list
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param rrset: rrset to add.
 * @return false on failure (malloc).
 */
static int
00331 iter_add_prepend_auth(struct module_qstate* qstate, struct iter_qstate* iq,
      struct ub_packed_rrset_key* rrset)
{
      struct iter_prep_list* p = (struct iter_prep_list*)regional_alloc(
            qstate->region, sizeof(struct iter_prep_list));
      if(!p)
            return 0;
      p->rrset = rrset;
      p->next = NULL;
      /* add at end */
      if(iq->ns_prepend_last)
            iq->ns_prepend_last->next = p;
      else  iq->ns_prepend_list = p;
      iq->ns_prepend_last = p;
      return 1;
}

/**
 * Given a CNAME response (defined as a response containing a CNAME or DNAME
 * that does not answer the request), process the response, modifying the
 * state as necessary. This follows the CNAME/DNAME chain and returns the
 * final query name.
 *
 * sets the new query name, after following the CNAME/DNAME chain.
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param msg: the response.
 * @param mname: returned target new query name.
 * @param mname_len: length of mname.
 * @return false on (malloc) error.
 */
static int
00363 handle_cname_response(struct module_qstate* qstate, struct iter_qstate* iq,
        struct dns_msg* msg, uint8_t** mname, size_t* mname_len)
{
      size_t i;
      /* Start with the (current) qname. */
      *mname = iq->qchase.qname;
      *mname_len = iq->qchase.qname_len;

      /* Iterate over the ANSWER rrsets in order, looking for CNAMEs and 
       * DNAMES. */
      for(i=0; i<msg->rep->an_numrrsets; i++) {
            struct ub_packed_rrset_key* r = msg->rep->rrsets[i];
            /* If there is a (relevant) DNAME, add it to the list.
             * We always expect there to be CNAME that was generated 
             * by this DNAME following, so we don't process the DNAME 
             * directly.  */
            if(ntohs(r->rk.type) == LDNS_RR_TYPE_DNAME &&
                  dname_strict_subdomain_c(*mname, r->rk.dname)) {
                  if(!iter_add_prepend_answer(qstate, iq, r))
                        return 0;
                  continue;
            }

            if(ntohs(r->rk.type) == LDNS_RR_TYPE_CNAME &&
                  query_dname_compare(*mname, r->rk.dname) == 0) {
                  /* Add this relevant CNAME rrset to the prepend list.*/
                  if(!iter_add_prepend_answer(qstate, iq, r))
                        return 0;
                  get_cname_target(r, mname, mname_len);
            }

            /* Other rrsets in the section are ignored. */
      }
      /* add authority rrsets to authority prepend, for wildcarded CNAMEs */
      for(i=msg->rep->an_numrrsets; i<msg->rep->an_numrrsets +
            msg->rep->ns_numrrsets; i++) {
            struct ub_packed_rrset_key* r = msg->rep->rrsets[i];
            /* only add NSEC/NSEC3, as they may be needed for validation */
            if(ntohs(r->rk.type) == LDNS_RR_TYPE_NSEC ||
                  ntohs(r->rk.type) == LDNS_RR_TYPE_NSEC3) {
                  if(!iter_add_prepend_auth(qstate, iq, r))
                        return 0;
            }
      }
      return 1;
}

/**
 * Generate a subrequest.
 * Generate a local request event. Local events are tied to this module, and
 * have a correponding (first tier) event that is waiting for this event to
 * resolve to continue.
 *
 * @param qname The query name for this request.
 * @param qnamelen length of qname
 * @param qtype The query type for this request.
 * @param qclass The query class for this request.
 * @param qstate The event that is generating this event.
 * @param id: module id.
 * @param iq: The iterator state that is generating this event.
 * @param initial_state The initial response state (normally this
 *          is QUERY_RESP_STATE, unless it is known that the request won't
 *          need iterative processing
 * @param final_state The final state for the response to this
 *          request.
 * @param subq_ret: if newly allocated, the subquerystate, or NULL if it does
 *    not need initialisation.
 * @return false on error (malloc).
 */
static int
00433 generate_sub_request(uint8_t* qname, size_t qnamelen, uint16_t qtype, 
      uint16_t qclass, struct module_qstate* qstate, int id,
      struct iter_qstate* iq, enum iter_state initial_state, 
      enum iter_state final_state, struct module_qstate** subq_ret)
{
      struct module_qstate* subq = NULL;
      struct iter_qstate* subiq = NULL;
      uint16_t qflags = 0; /* OPCODE QUERY, no flags */
      struct query_info qinf;
      int prime = (final_state == PRIME_RESP_STATE)?1:0;
      qinf.qname = qname;
      qinf.qname_len = qnamelen;
      qinf.qtype = qtype;
      qinf.qclass = qclass;

      /* RD should be set only when sending the query back through the INIT
       * state. */
      if(initial_state == INIT_REQUEST_STATE)
            qflags |= BIT_RD;
      /* We set the CD flag so we can send this through the "head" of 
       * the resolution chain, which might have a validator. We are 
       * uninterested in validating things not on the direct resolution 
       * path.  */
      qflags |= BIT_CD;

      /* attach subquery, lookup existing or make a new one */
      fptr_ok(fptr_whitelist_modenv_attach_sub(qstate->env->attach_sub));
      if(!(*qstate->env->attach_sub)(qstate, &qinf, qflags, prime, &subq)) {
            return 0;
      }
      *subq_ret = subq;
      if(subq) {
            /* initialise the new subquery */
            subq->curmod = id;
            subq->ext_state[id] = module_state_initial;
            subq->minfo[id] = regional_alloc(subq->region, 
                  sizeof(struct iter_qstate));
            if(!subq->minfo[id]) {
                  log_err("init subq: out of memory");
                  fptr_ok(fptr_whitelist_modenv_kill_sub(
                        qstate->env->kill_sub));
                  (*qstate->env->kill_sub)(subq);
                  return 0;
            }
            subiq = (struct iter_qstate*)subq->minfo[id];
            memset(subiq, 0, sizeof(*subiq));
            subiq->num_target_queries = 0;
            subiq->num_current_queries = 0;
            subiq->depth = iq->depth+1;
            outbound_list_init(&subiq->outlist);
            subiq->state = initial_state;
            subiq->final_state = final_state;
            subiq->qchase = subq->qinfo;
            subiq->chase_flags = subq->query_flags;
            subiq->refetch_glue = 0;
      }
      return 1;
}

/**
 * Generate and send a root priming request.
 * @param qstate: the qtstate that triggered the need to prime.
 * @param iq: iterator query state.
 * @param ie: iterator global state.
 * @param id: module id.
 * @param qclass: the class to prime.
 */
static int
00501 prime_root(struct module_qstate* qstate, struct iter_qstate* iq, 
      struct iter_env* ie, int id, uint16_t qclass)
{
      struct delegpt* dp;
      struct module_qstate* subq;
      verbose(VERB_DETAIL, "priming . %s NS", 
            ldns_lookup_by_id(ldns_rr_classes, (int)qclass)?
            ldns_lookup_by_id(ldns_rr_classes, (int)qclass)->name:"??");
      dp = hints_lookup_root(ie->hints, qclass);
      if(!dp) {
            verbose(VERB_ALGO, "Cannot prime due to lack of hints");
            return 0;
      }
      /* copy dp; to avoid messing up available list for other thr/queries */
      dp = delegpt_copy(dp, qstate->region);
      if(!dp) {
            log_err("out of memory priming root, copydp");
            return 0;
      }
      /* Priming requests start at the QUERYTARGETS state, skipping 
       * the normal INIT state logic (which would cause an infloop). */
      if(!generate_sub_request((uint8_t*)"\000", 1, LDNS_RR_TYPE_NS, 
            qclass, qstate, id, iq, QUERYTARGETS_STATE, PRIME_RESP_STATE,
            &subq)) {
            log_err("out of memory priming root");
            return 0;
      }
      if(subq) {
            struct iter_qstate* subiq = 
                  (struct iter_qstate*)subq->minfo[id];
            /* Set the initial delegation point to the hint. */
            subiq->dp = dp;
            /* there should not be any target queries. */
            subiq->num_target_queries = 0; 
      }
      
      /* this module stops, our submodule starts, and does the query. */
      qstate->ext_state[id] = module_wait_subquery;
      return 1;
}

/**
 * Generate and process a stub priming request. This method tests for the
 * need to prime a stub zone, so it is safe to call for every request.
 *
 * @param qstate: the qtstate that triggered the need to prime.
 * @param iq: iterator query state.
 * @param ie: iterator global state.
 * @param id: module id.
 * @param qname: request name.
 * @param qclass: the class to prime.
 * @return true if a priming subrequest was made, false if not. The will only
 *         issue a priming request if it detects an unprimed stub.
 */
static int
00556 prime_stub(struct module_qstate* qstate, struct iter_qstate* iq, 
      struct iter_env* ie, int id, uint8_t* qname, uint16_t qclass)
{
      /* Lookup the stub hint. This will return null if the stub doesn't 
       * need to be re-primed. */
      struct delegpt* stub_dp = hints_lookup_stub(ie->hints, qname, qclass, 
            iq->dp);
      struct module_qstate* subq;
      /* The stub (if there is one) does not need priming. */
      if(!stub_dp)
            return 0;

      /* Otherwise, we need to (re)prime the stub. */
      log_nametypeclass(VERB_DETAIL, "priming stub", stub_dp->name, 
            LDNS_RR_TYPE_NS, qclass);

      /* Stub priming events start at the QUERYTARGETS state to avoid the
       * redundant INIT state processing. */
      if(!generate_sub_request(stub_dp->name, stub_dp->namelen, 
            LDNS_RR_TYPE_NS, qclass, qstate, id, iq,
            QUERYTARGETS_STATE, PRIME_RESP_STATE, &subq)) {
            log_err("out of memory priming stub");
            (void)error_response(qstate, id, LDNS_RCODE_SERVFAIL);
            return 1; /* return 1 to make module stop, with error */
      }
      if(subq) {
            struct iter_qstate* subiq = 
                  (struct iter_qstate*)subq->minfo[id];

            /* Set the initial delegation point to the hint. */
            /* make copy to avoid use of stub dp by different qs/threads */
            subiq->dp = delegpt_copy(stub_dp, subq->region);
            if(!subiq->dp) {
                  log_err("out of memory priming stub, copydp");
                  fptr_ok(fptr_whitelist_modenv_kill_sub(
                        qstate->env->kill_sub));
                  (*qstate->env->kill_sub)(subq);
                  (void)error_response(qstate, id, LDNS_RCODE_SERVFAIL);
                  return 1; /* return 1 to make module stop, with error */
            }
            /* there should not be any target queries -- although there 
             * wouldn't be anyway, since stub hints never have 
             * missing targets. */
            subiq->num_target_queries = 0; 
            subiq->wait_priming_stub = 1;
      }
      
      /* this module stops, our submodule starts, and does the query. */
      qstate->ext_state[id] = module_wait_subquery;
      return 1;
}

/**
 * See if the query needs forwarding.
 * 
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param ie: iterator shared global environment.
 * @return true if the request is forwarded, false if not.
 *    If returns true but, iq->dp is NULL then a malloc failure occurred.
 */
static int
00618 forward_request(struct module_qstate* qstate, struct iter_qstate* iq,
      struct iter_env* ie)
{
      struct delegpt* dp = forwards_lookup(ie->fwds, iq->qchase.qname,
            iq->qchase.qclass);
      if(!dp) 
            return 0;
      /* send recursion desired to forward addr */
      iq->chase_flags |= BIT_RD; 
      iq->dp = delegpt_copy(dp, qstate->region);
      /* iq->dp checked by caller */
      verbose(VERB_ALGO, "forwarding request");
      return 1;
}

/** 
 * Process the initial part of the request handling. This state roughly
 * corresponds to resolver algorithms steps 1 (find answer in cache) and 2
 * (find the best servers to ask).
 *
 * Note that all requests start here, and query restarts revisit this state.
 *
 * This state either generates: 1) a response, from cache or error, 2) a
 * priming event, or 3) forwards the request to the next state (init2,
 * generally).
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param ie: iterator shared global environment.
 * @param id: module id.
 * @return true if the event needs more request processing immediately,
 *         false if not.
 */
static int
00652 processInitRequest(struct module_qstate* qstate, struct iter_qstate* iq,
      struct iter_env* ie, int id)
{
      uint8_t* delname;
      size_t delnamelen;
      struct dns_msg* msg;

      log_query_info(VERB_DETAIL, "resolving", &qstate->qinfo);
      /* check effort */

      /* We enforce a maximum number of query restarts. This is primarily a
       * cheap way to prevent CNAME loops. */
      if(iq->query_restart_count > MAX_RESTART_COUNT) {
            verbose(VERB_QUERY, "request has exceeded the maximum number"
                  " of query restarts with %d", iq->query_restart_count);
            return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
      }

      /* We enforce a maximum recursion/dependency depth -- in general, 
       * this is unnecessary for dependency loops (although it will 
       * catch those), but it provides a sensible limit to the amount 
       * of work required to answer a given query. */
      verbose(VERB_ALGO, "request has dependency depth of %d", iq->depth);
      if(iq->depth > ie->max_dependency_depth) {
            verbose(VERB_QUERY, "request has exceeded the maximum "
                  "dependency depth with depth of %d", iq->depth);
            return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
      }

      /* Resolver Algorithm Step 1 -- Look for the answer in local data. */

      /* This either results in a query restart (CNAME cache response), a
       * terminating response (ANSWER), or a cache miss (null). */
      
      msg = dns_cache_lookup(qstate->env, iq->qchase.qname, 
            iq->qchase.qname_len, iq->qchase.qtype, 
            iq->qchase.qclass, qstate->region, qstate->env->scratch);
      if(msg) {
            /* handle positive cache response */
            enum response_type type = response_type_from_cache(msg, 
                  &iq->qchase);
            if(verbosity >= VERB_ALGO)
                  log_dns_msg("msg from cache lookup", &msg->qinfo, 
                        msg->rep);

            if(type == RESPONSE_TYPE_CNAME) {
                  uint8_t* sname = 0;
                  size_t slen = 0;
                  verbose(VERB_ALGO, "returning CNAME response from "
                        "cache");
                  if(!handle_cname_response(qstate, iq, msg, 
                        &sname, &slen))
                        return error_response(qstate, id, 
                              LDNS_RCODE_SERVFAIL);
                  iq->qchase.qname = sname;
                  iq->qchase.qname_len = slen;
                  /* This *is* a query restart, even if it is a cheap 
                   * one. */
                  iq->query_restart_count++;
                  return next_state(iq, INIT_REQUEST_STATE);
            }

            /* it is an answer, response, to final state */
            verbose(VERB_ALGO, "returning answer from cache.");
            iq->response = msg;
            return final_state(iq);
      }
      
      /* attempt to forward the request */
      if(forward_request(qstate, iq, ie))
      {
            if(!iq->dp) {
                  log_err("alloc failure for forward dp");
                  return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
            }
            /* the request has been forwarded.
             * forwarded requests need to be immediately sent to the 
             * next state, QUERYTARGETS. */
            return next_state(iq, QUERYTARGETS_STATE);
      }

      /* Resolver Algorithm Step 2 -- find the "best" servers. */

      /* first, adjust for DS queries. To avoid the grandparent problem, 
       * we just look for the closest set of server to the parent of qname.
       * When re-fetching glue we also need to ask the parent.
       */
      if(iq->refetch_glue) {
            if(!iq->dp) {
                  log_err("internal or malloc fail: no dp for refetch");
                  return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
            }
            delname = iq->dp->name;
            delnamelen = iq->dp->namelen;
      } else {
            delname = iq->qchase.qname;
            delnamelen = iq->qchase.qname_len;
      }
      if((iq->qchase.qtype == LDNS_RR_TYPE_DS || iq->refetch_glue)
            && !dname_is_root(delname)) {
            /* do not adjust root label, remove first label from delname */
            dname_remove_label(&delname, &delnamelen);
            iq->refetch_glue = 0; /* if CNAME causes restart, no refetch */
      }
      while(1) {
            
            /* Lookup the delegation in the cache. If null, then the 
             * cache needs to be primed for the qclass. */
            iq->dp = dns_cache_find_delegation(qstate->env, delname, 
                  delnamelen, iq->qchase.qtype, iq->qchase.qclass, 
                  qstate->region, &iq->deleg_msg, *qstate->env->now);

            /* If the cache has returned nothing, then we have a 
             * root priming situation. */
            if(iq->dp == NULL) {
                  /* Note that the result of this will set a new
                   * DelegationPoint based on the result of priming. */
                  if(!prime_root(qstate, iq, ie, id, iq->qchase.qclass))
                        return error_response(qstate, id, 
                              LDNS_RCODE_REFUSED);

                  /* priming creates and sends a subordinate query, with 
                   * this query as the parent. So further processing for 
                   * this event will stop until reactivated by the 
                   * results of priming. */
                  return 0;
            }

            /* see if this dp not useless.
             * It is useless if:
             *    o all NS items are required glue. 
             *      or the query is for NS item that is required glue.
             *    o no addresses are provided.
             *    o RD qflag is on.
             * Instead, go up one level, and try to get even further
             * If the root was useless, use safety belt information. 
             * Only check cache returns, because replies for servers
             * could be useless but lead to loops (bumping into the
             * same server reply) if useless-checked.
             */
            if(iter_dp_is_useless(qstate, iq->dp)) {
                  if(dname_is_root(iq->dp->name)) {
                        /* use safety belt */
                        verbose(VERB_QUERY, "Cache has root NS but "
                        "no addresses. Fallback to the safety belt.");
                        iq->dp = hints_lookup_root(ie->hints, 
                              iq->qchase.qclass);
                        /* note deleg_msg is from previous lookup,
                         * but RD is on, so it is not used */
                        if(!iq->dp) {
                              log_err("internal error: no hints dp");
                              return error_response(qstate, id, 
                                    LDNS_RCODE_REFUSED);
                        }
                        iq->dp = delegpt_copy(iq->dp, qstate->region);
                        if(!iq->dp) {
                              log_err("out of memory in safety belt");
                              return error_response(qstate, id, 
                                    LDNS_RCODE_SERVFAIL);
                        }
                        break;
                  } else {
                        verbose(VERB_ALGO, 
                              "cache delegation was useless:");
                        delegpt_log(VERB_ALGO, iq->dp);
                        /* go up */
                        delname = iq->dp->name;
                        delnamelen = iq->dp->namelen;
                        dname_remove_label(&delname, &delnamelen);
                  }
            } else break;
      }

      verbose(VERB_ALGO, "cache delegation returns delegpt");
      delegpt_log(VERB_ALGO, iq->dp);

      /* Otherwise, set the current delegation point and move on to the 
       * next state. */
      return next_state(iq, INIT_REQUEST_2_STATE);
}

/** 
 * Process the second part of the initial request handling. This state
 * basically exists so that queries that generate root priming events have
 * the same init processing as ones that do not. Request events that reach
 * this state must have a valid currentDelegationPoint set.
 *
 * This part is primarly handling stub zone priming. Events that reach this
 * state must have a current delegation point.
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param ie: iterator shared global environment.
 * @param id: module id.
 * @return true if the event needs more request processing immediately,
 *         false if not.
 */
static int
00850 processInitRequest2(struct module_qstate* qstate, struct iter_qstate* iq,
      struct iter_env* ie, int id)
{
      log_query_info(VERB_QUERY, "resolving (init part 2): ", 
            &qstate->qinfo);

      /* Check to see if we need to prime a stub zone. */
      if(prime_stub(qstate, iq, ie, id, iq->qchase.qname, 
            iq->qchase.qclass)) {
            /* A priming sub request was made */
            return 0;
      }

      /* most events just get forwarded to the next state. */
      return next_state(iq, INIT_REQUEST_3_STATE);
}

/** 
 * Process the third part of the initial request handling. This state exists
 * as a separate state so that queries that generate stub priming events
 * will get the tail end of the init process but not repeat the stub priming
 * check.
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @return true, advancing the event to the QUERYTARGETS_STATE.
 */
static int
00878 processInitRequest3(struct module_qstate* qstate, struct iter_qstate* iq)
{
      log_query_info(VERB_QUERY, "resolving (init part 3): ", 
            &qstate->qinfo);
      /* if the cache reply dp equals a validation anchor or msg has DS,
       * then DNSSEC RRSIGs are expected in the reply */
      iq->dnssec_expected = iter_indicates_dnssec(qstate->env, iq->dp, 
            iq->deleg_msg, iq->qchase.qclass);

      /* If the RD flag wasn't set, then we just finish with the 
       * cached referral as the response. */
      if(!(qstate->query_flags & BIT_RD)) {
            iq->response = iq->deleg_msg;
            if(verbosity >= VERB_ALGO)
                  log_dns_msg("no RD requested, using delegation msg", 
                        &iq->response->qinfo, iq->response->rep);
            return final_state(iq);
      }

      /* After this point, unset the RD flag -- this query is going to 
       * be sent to an auth. server. */
      iq->chase_flags &= ~BIT_RD;

      /* Jump to the next state. */
      return next_state(iq, QUERYTARGETS_STATE);
}

/**
 * Given a basic query, generate a "target" query. These are subordinate
 * queries for missing delegation point target addresses.
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param id: module id.
 * @param name: target qname.
 * @param namelen: target qname length.
 * @param qtype: target qtype (either A or AAAA).
 * @param qclass: target qclass.
 * @return true on success, false on failure.
 */
static int
00919 generate_target_query(struct module_qstate* qstate, struct iter_qstate* iq,
        int id, uint8_t* name, size_t namelen, uint16_t qtype, uint16_t qclass)
{
      struct module_qstate* subq;
      if(!generate_sub_request(name, namelen, qtype, qclass, qstate, 
            id, iq, INIT_REQUEST_STATE, FINISHED_STATE, &subq))
            return 0;
      if(subq) {
            struct iter_qstate* subiq = 
                  (struct iter_qstate*)subq->minfo[id];
            if(dname_subdomain_c(name, iq->dp->name)) {
                  verbose(VERB_ALGO, "refetch of target glue");
                  subiq->refetch_glue = 1;
                  subiq->dp = delegpt_copy(iq->dp, subq->region);
            }
      }
      log_nametypeclass(VERB_QUERY, "new target", name, qtype, qclass);
      return 1;
}

/**
 * Given an event at a certain state, generate zero or more target queries
 * for it's current delegation point.
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param ie: iterator shared global environment.
 * @param id: module id.
 * @param maxtargets: The maximum number of targets to query for.
 *    if it is negative, there is no maximum number of targets.
 * @param num: returns the number of queries generated and processed, 
 *    which may be zero if there were no missing targets.
 * @return false on error.
 */
static int
00954 query_for_targets(struct module_qstate* qstate, struct iter_qstate* iq,
        struct iter_env* ie, int id, int maxtargets, int* num)
{
      int query_count = 0;
      struct delegpt_ns* ns = iq->dp->nslist;
      int missing;
      int toget = 0;

      iter_mark_cycle_targets(qstate, iq->dp);
      missing = (int)delegpt_count_missing_targets(iq->dp);
      log_assert(maxtargets != 0); /* that would not be useful */

      /* Generate target requests. Basically, any missing targets 
       * are queried for here, regardless if it is necessary to do 
       * so to continue processing. */
      if(maxtargets < 0 || maxtargets > missing)
            toget = missing;
      else  toget = maxtargets;
      if(toget == 0) {
            *num = 0;
            return 1;
      }
      /* select 'toget' items from the total of 'missing' items */
      log_assert(toget <= missing);

      /* loop over missing targets */
      for(ns = iq->dp->nslist; ns; ns = ns->next) {
            if(ns->resolved)
                  continue;

            /* randomly select this item with probability toget/missing */
            if(!iter_ns_probability(qstate->env->rnd, toget, missing)) {
                  /* do not select this one, next; select toget number
                   * of items from a list one less in size */
                  missing --;
                  continue;
            }

            if(ie->supports_ipv6) {
                  /* Send the AAAA request. */
                  if(!generate_target_query(qstate, iq, id, 
                        ns->name, ns->namelen,
                        LDNS_RR_TYPE_AAAA, iq->qchase.qclass))
                        return 0;
                  query_count++;
            }
            /* Send the A request. */
            if(!generate_target_query(qstate, iq, id, 
                  ns->name, ns->namelen, 
                  LDNS_RR_TYPE_A, iq->qchase.qclass))
                  return 0;
            query_count++;

            /* mark this target as in progress. */
            ns->resolved = 1;
            missing--;
            toget--;
            if(toget == 0)
                  break;
      }
      *num = query_count;
      if(query_count > 0)
            qstate->ext_state[id] = module_wait_subquery;

      return 1;
}

/** 
 * This is the request event state where the request will be sent to one of
 * its current query targets. This state also handles issuing target lookup
 * queries for missing target IP addresses. Queries typically iterate on
 * this state, both when they are just trying different targets for a given
 * delegation point, and when they change delegation points. This state
 * roughly corresponds to RFC 1034 algorithm steps 3 and 4.
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param ie: iterator shared global environment.
 * @param id: module id.
 * @return true if the event requires more request processing immediately,
 *         false if not. This state only returns true when it is generating
 *         a SERVFAIL response because the query has hit a dead end.
 */
static int
01038 processQueryTargets(struct module_qstate* qstate, struct iter_qstate* iq,
      struct iter_env* ie, int id)
{
      int tf_policy;
      struct delegpt_addr* target;
      struct outbound_entry* outq;

      /* NOTE: a request will encounter this state for each target it 
       * needs to send a query to. That is, at least one per referral, 
       * more if some targets timeout or return throwaway answers. */

      log_query_info(VERB_QUERY, "processQueryTargets:", &qstate->qinfo);
      verbose(VERB_ALGO, "processQueryTargets: targetqueries %d, "
            "currentqueries %d", iq->num_target_queries, 
            iq->num_current_queries);
      qstate->ext_state[id] = module_wait_reply;

      /* Make sure that we haven't run away */
      /* FIXME: is this check even necessary? */
      if(iq->referral_count > MAX_REFERRAL_COUNT) {
            verbose(VERB_QUERY, "request has exceeded the maximum "
                  "number of referrrals with %d", iq->referral_count);
            return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
      }
      
      /* Make sure we have a delegation point, otherwise priming failed
       * or another failure occurred */
      if(!iq->dp) {
            verbose(VERB_QUERY, "Failed to get a delegation, giving up");
            return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
      }
      delegpt_log(VERB_ALGO, iq->dp);

      if(iq->num_current_queries>0) {
            /* already busy answering a query, this restart is because
             * more delegpt addrs became available, wait for existing
             * query. */
            verbose(VERB_ALGO, "woke up, but wait for outstanding query");
            return 0;
      }

      tf_policy = 0;
      if(iq->depth <= ie->max_dependency_depth) {
            tf_policy = ie->target_fetch_policy[iq->depth];
      }

      /* if there is a policy to fetch missing targets 
       * opportunistically, do it. we rely on the fact that once a 
       * query (or queries) for a missing name have been issued, 
       * they will not be show up again. */
      if(tf_policy != 0) {
            int extra = 0;
            verbose(VERB_ALGO, "attempt to get extra %d targets", 
                  tf_policy);
            if(!query_for_targets(qstate, iq, ie, id, tf_policy, &extra)) {
                  return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
            }
            iq->num_target_queries += extra;
      }

      /* Add the current set of unused targets to our queue. */
      delegpt_add_unused_targets(iq->dp);

      /* Select the next usable target, filtering out unsuitable targets. */
      target = iter_server_selection(ie, qstate->env, iq->dp, 
            iq->dp->name, iq->dp->namelen, &iq->dnssec_expected);

      /* If no usable target was selected... */
      if(!target) {
            /* Here we distinguish between three states: generate a new 
             * target query, just wait, or quit (with a SERVFAIL).
             * We have the following information: number of active 
             * target queries, number of active current queries, 
             * the presence of missing targets at this delegation 
             * point, and the given query target policy. */
            
            /* Check for the wait condition. If this is true, then 
             * an action must be taken. */
            if(iq->num_target_queries==0 && iq->num_current_queries==0) {
                  /* If there is nothing to wait for, then we need 
                   * to distinguish between generating (a) new target 
                   * query, or failing. */
                  if(delegpt_count_missing_targets(iq->dp) > 0) {
                        int qs = 0;
                        verbose(VERB_ALGO, "querying for next "
                              "missing target");
                        if(!query_for_targets(qstate, iq, ie, id, 
                              1, &qs)) {
                              return error_response(qstate, id,
                                    LDNS_RCODE_SERVFAIL);
                        }
                        iq->num_target_queries += qs;
                  }
                  /* Since a target query might have been made, we 
                   * need to check again. */
                  if(iq->num_target_queries == 0) {
                        verbose(VERB_QUERY, "out of query targets -- "
                              "returning SERVFAIL");
                        /* fail -- no more targets, no more hope 
                         * of targets, no hope of a response. */
                        return error_response(qstate, id,
                              LDNS_RCODE_SERVFAIL);
                  }
            }

            /* otherwise, we have no current targets, so submerge 
             * until one of the target or direct queries return. */
            if(iq->num_target_queries>0 && iq->num_current_queries>0)
                  verbose(VERB_ALGO, "no current targets -- waiting "
                        "for %d targets to resolve or %d outstanding"
                        " queries to respond", iq->num_target_queries, 
                        iq->num_current_queries);
            else if(iq->num_target_queries>0)
                  verbose(VERB_ALGO, "no current targets -- waiting "
                        "for %d targets to resolve.",
                        iq->num_target_queries);
            else  verbose(VERB_ALGO, "no current targets -- waiting "
                        "for %d outstanding queries to respond.",
                        iq->num_current_queries);
            return 0;
      }

      /* We have a valid target. */
      log_query_info(VERB_QUERY, "sending query:", &iq->qchase);
      log_name_addr(VERB_QUERY, "sending to target:", iq->dp->name, 
            &target->addr, target->addrlen);
      fptr_ok(fptr_whitelist_modenv_send_query(qstate->env->send_query));
      outq = (*qstate->env->send_query)(
            iq->qchase.qname, iq->qchase.qname_len, 
            iq->qchase.qtype, iq->qchase.qclass, 
            iq->chase_flags, EDNS_DO|BIT_CD, 
            &target->addr, target->addrlen, qstate);
      if(!outq) {
            verbose(VERB_OPS, "error sending query to auth server; "
                  "skip this address");
            log_addr(VERB_OPS, "error for address:", 
                  &target->addr, target->addrlen);
            return next_state(iq, QUERYTARGETS_STATE);
      }
      outbound_list_insert(&iq->outlist, outq);
      iq->num_current_queries++;
      qstate->ext_state[id] = module_wait_reply;

      return 0;
}

/** 
 * Process the query response. All queries end up at this state first. This
 * process generally consists of analyzing the response and routing the
 * event to the next state (either bouncing it back to a request state, or
 * terminating the processing for this event).
 * 
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param id: module id.
 * @return true if the event requires more immediate processing, false if
 *         not. This is generally only true when forwarding the request to
 *         the final state (i.e., on answer).
 */
static int
01198 processQueryResponse(struct module_qstate* qstate, struct iter_qstate* iq,
      int id)
{
      int dnsseclame = 0;
      enum response_type type;
      iq->num_current_queries--;
      if(iq->response == NULL) {
            verbose(VERB_ALGO, "query response was timeout");
            return next_state(iq, QUERYTARGETS_STATE);
      }
      type = response_type_from_server((int)(iq->chase_flags&BIT_RD),
            iq->response, &iq->qchase, iq->dp);
      if(type == RESPONSE_TYPE_REFERRAL && (iq->chase_flags&BIT_RD)) {
            /* When forwarding (RD bit is set), we handle referrals 
             * differently. No queries should be sent elsewhere */
            type = RESPONSE_TYPE_ANSWER;
      }
      if(iq->dnssec_expected && !(iq->chase_flags&BIT_RD) 
            && type != RESPONSE_TYPE_LAME 
            && type != RESPONSE_TYPE_THROWAWAY 
            && type != RESPONSE_TYPE_UNTYPED) {
            /* a possible answer, see if it is missing DNSSEC */
            /* but not when forwarding, so we dont mark fwder lame */
            /* also make sure the answer is from the zone we expected,
             * otherwise, (due to parent,child on same server), we
             * might mark the server,zone lame inappropriately */
            if(!iter_msg_has_dnssec(iq->response) &&
                  iter_msg_from_zone(iq->response, iq->dp, type,
                        iq->qchase.qclass)) {
                  type = RESPONSE_TYPE_LAME;
                  dnsseclame = 1;
            }
      }

      /* handle each of the type cases */
      if(type == RESPONSE_TYPE_ANSWER) {
            /* ANSWER type responses terminate the query algorithm, 
             * so they sent on their */
            verbose(VERB_DETAIL, "query response was ANSWER");
            if(!iter_dns_store(qstate->env, &iq->response->qinfo,
                  iq->response->rep, 0))
                  return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
            /* close down outstanding requests to be discarded */
            outbound_list_clear(&iq->outlist);
            iq->num_current_queries = 0;
            fptr_ok(fptr_whitelist_modenv_detach_subs(
                  qstate->env->detach_subs));
            (*qstate->env->detach_subs)(qstate);
            iq->num_target_queries = 0;
            return final_state(iq);
      } else if(type == RESPONSE_TYPE_REFERRAL) {
            /* REFERRAL type responses get a reset of the 
             * delegation point, and back to the QUERYTARGETS_STATE. */
            verbose(VERB_DETAIL, "query response was REFERRAL");

            /* Store the referral under the current query */
            if(!iter_dns_store(qstate->env, &iq->response->qinfo,
                  iq->response->rep, 1))
                  return error_response(qstate, id, LDNS_RCODE_SERVFAIL);

            /* Reset the event state, setting the current delegation 
             * point to the referral. */
            iq->deleg_msg = iq->response;
            iq->dp = delegpt_from_message(iq->response, qstate->region);
            if(!iq->dp)
                  return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
            if(!cache_fill_missing(qstate->env, iq->qchase.qclass, 
                  qstate->region, iq->dp))
                  return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
            delegpt_log(VERB_ALGO, iq->dp);
            /* Count this as a referral. */
            iq->referral_count++;
            /* see if the next dp is a trust anchor, or a DS was sent
             * along, indicating dnssec is expected for next zone */
            iq->dnssec_expected = iter_indicates_dnssec(qstate->env, 
                  iq->dp, iq->response, iq->qchase.qclass);

            /* stop current outstanding queries. 
             * FIXME: should the outstanding queries be waited for and
             * handled? Say by a subquery that inherits the outbound_entry.
             */
            outbound_list_clear(&iq->outlist);
            iq->num_current_queries = 0;
            fptr_ok(fptr_whitelist_modenv_detach_subs(
                  qstate->env->detach_subs));
            (*qstate->env->detach_subs)(qstate);
            iq->num_target_queries = 0;
            verbose(VERB_ALGO, "cleared outbound list for next round");
            return next_state(iq, QUERYTARGETS_STATE);
      } else if(type == RESPONSE_TYPE_CNAME) {
            uint8_t* sname = NULL;
            size_t snamelen = 0;
            /* CNAME type responses get a query restart (i.e., get a 
             * reset of the query state and go back to INIT_REQUEST_STATE).
             */
            verbose(VERB_DETAIL, "query response was CNAME");
            if(verbosity >= VERB_ALGO)
                  log_dns_msg("cname msg", &iq->response->qinfo, 
                        iq->response->rep);
            /* Process the CNAME response. */
            if(!handle_cname_response(qstate, iq, iq->response, 
                  &sname, &snamelen))
                  return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
            /* cache the CNAME response under the current query */
            /* NOTE : set referral=1, so that rrsets get stored but not 
             * the partial query answer (CNAME only). */
            if(!iter_dns_store(qstate->env, &iq->response->qinfo,
                  iq->response->rep, 1))
                  return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
            /* set the current request's qname to the new value. */
            iq->qchase.qname = sname;
            iq->qchase.qname_len = snamelen;
            /* Clear the query state, since this is a query restart. */
            iq->deleg_msg = NULL;
            iq->dp = NULL;
            iq->dnssec_expected = 0;
            /* Note the query restart. */
            iq->query_restart_count++;

            /* stop current outstanding queries. 
             * FIXME: should the outstanding queries be waited for and
             * handled? Say by a subquery that inherits the outbound_entry.
             */
            outbound_list_clear(&iq->outlist);
            iq->num_current_queries = 0;
            fptr_ok(fptr_whitelist_modenv_detach_subs(
                  qstate->env->detach_subs));
            (*qstate->env->detach_subs)(qstate);
            iq->num_target_queries = 0;
            verbose(VERB_ALGO, "cleared outbound list for query restart");
            /* go to INIT_REQUEST_STATE for new qname. */
            return next_state(iq, INIT_REQUEST_STATE);
      } else if(type == RESPONSE_TYPE_LAME) {
            /* Cache the LAMEness. */
            verbose(VERB_DETAIL, "query response was %sLAME",
                  dnsseclame?"DNSSEC ":"");
            if(qstate->reply) {
                  /* need addr for lameness cache, but we may have
                   * gotten this from cache, so test to be sure */
                  if(!infra_set_lame(qstate->env->infra_cache, 
                        &qstate->reply->addr, qstate->reply->addrlen, 
                        iq->dp->name, iq->dp->namelen, 
                        *qstate->env->now, dnsseclame))
                        log_err("mark host lame: out of memory");
            } else log_err("%slame response from cache",
                  dnsseclame?"DNSSEC ":"");
      } else if(type == RESPONSE_TYPE_THROWAWAY) {
            /* LAME and THROWAWAY responses are handled the same way. 
             * In this case, the event is just sent directly back to 
             * the QUERYTARGETS_STATE without resetting anything, 
             * because, clearly, the next target must be tried. */
            verbose(VERB_DETAIL, "query response was THROWAWAY");
      } else {
            log_warn("A query response came back with an unknown type: %d",
                  (int)type);
      }

      /* LAME, THROWAWAY and "unknown" all end up here.
       * Recycle to the QUERYTARGETS state to hopefully try a 
       * different target. */
      return next_state(iq, QUERYTARGETS_STATE);
}

/**
 * Return priming query results to interestes super querystates.
 * 
 * Sets the delegation point and delegation message (not nonRD queries).
 * This is a callback from walk_supers.
 *
 * @param qstate: priming query state that finished.
 * @param id: module id.
 * @param forq: the qstate for which priming has been done.
 */
static void
01372 prime_supers(struct module_qstate* qstate, int id, struct module_qstate* forq)
{
      struct iter_qstate* foriq = (struct iter_qstate*)forq->minfo[id];
      struct delegpt* dp = NULL;

      log_assert(qstate->is_priming || foriq->wait_priming_stub);
      log_assert(qstate->return_rcode == LDNS_RCODE_NOERROR);
      /* Convert our response to a delegation point */
      dp = delegpt_from_message(qstate->return_msg, forq->region);
      if(!dp) {
            /* if there is no convertable delegation point, then 
             * the ANSWER type was (presumably) a negative answer. */
            verbose(VERB_ALGO, "prime response was not a positive "
                  "ANSWER; failing");
            foriq->dp = NULL;
            foriq->state = QUERYTARGETS_STATE;
            return;
      }

      log_query_info(VERB_DETAIL, "priming successful for", &qstate->qinfo);
      delegpt_log(VERB_ALGO, dp);
      foriq->dp = dp;
      foriq->deleg_msg = dns_copy_msg(qstate->return_msg, forq->region);
      if(!foriq->deleg_msg) {
            log_err("copy prime response: out of memory");
            foriq->dp = NULL;
            foriq->state = QUERYTARGETS_STATE;
            return;
      }

      /* root priming responses go to init stage 2, priming stub 
       * responses to to stage 3. */
      if(foriq->wait_priming_stub) {
            foriq->state = INIT_REQUEST_3_STATE;
            foriq->wait_priming_stub = 0;
      } else      foriq->state = INIT_REQUEST_2_STATE;
      /* because we are finished, the parent will be reactivated */
}

/** 
 * This handles the response to a priming query. This is used to handle both
 * root and stub priming responses. This is basically the equivalent of the
 * QUERY_RESP_STATE, but will not handle CNAME responses and will treat
 * REFERRALs as ANSWERS. It will also update and reactivate the originating
 * event.
 *
 * @param qstate: query state.
 * @param id: module id.
 * @return true if the event needs more immediate processing, false if not.
 *         This state always returns false.
 */
static int
01424 processPrimeResponse(struct module_qstate* qstate, int id)
{
      struct iter_qstate* iq = (struct iter_qstate*)qstate->minfo[id];
      enum response_type type = response_type_from_server(0, iq->response, 
            &iq->qchase, iq->dp);
      if(type == RESPONSE_TYPE_ANSWER) {
            qstate->return_rcode = LDNS_RCODE_NOERROR;
            qstate->return_msg = iq->response;
      } else {
            qstate->return_rcode = LDNS_RCODE_SERVFAIL;
            qstate->return_msg = NULL;
      }

      /* This event is finished. */
      qstate->ext_state[id] = module_finished;
      return 0;
}

/** 
 * Do final processing on responses to target queries. Events reach this
 * state after the iterative resolution algorithm terminates. This state is
 * responsible for reactiving the original event, and housekeeping related
 * to received target responses (caching, updating the current delegation
 * point, etc).
 * Callback from walk_supers for every super state that is interested in 
 * the results from this query.
 *
 * @param qstate: query state.
 * @param id: module id.
 * @param forq: super query state.
 */
static void
01456 processTargetResponse(struct module_qstate* qstate, int id,
      struct module_qstate* forq)
{
      struct iter_qstate* iq = (struct iter_qstate*)qstate->minfo[id];
      struct iter_qstate* foriq = (struct iter_qstate*)forq->minfo[id];
      struct ub_packed_rrset_key* rrset;
      struct delegpt_ns* dpns;
      log_assert(qstate->return_rcode == LDNS_RCODE_NOERROR);

      foriq->state = QUERYTARGETS_STATE;
      log_query_info(VERB_ALGO, "processTargetResponse", &qstate->qinfo);
      log_query_info(VERB_ALGO, "processTargetResponse super", &forq->qinfo);

      /* check to see if parent event is still interested (in orig name).  */
      dpns = delegpt_find_ns(foriq->dp, qstate->qinfo.qname,
                  qstate->qinfo.qname_len);
      if(!dpns) {
            /* FIXME: maybe store this nameserver address in the cache
             * anyways? */
            /* If not, just stop processing this event */
            verbose(VERB_ALGO, "subq: parent not interested anymore");
            /* this is an error, and will cause parent to be reactivated
             * even though nothing has happened */
            log_assert(0);
            return;
      }

      /* Tell the originating event that this target query has finished
       * (regardless if it succeeded or not). */
      foriq->num_target_queries--;

      /* This response is relevant to the current query, so we 
       * add (attempt to add, anyway) this target(s) and reactivate 
       * the original event. 
       * NOTE: we could only look for the AnswerRRset if the 
       * response type was ANSWER. */
      rrset = reply_find_answer_rrset(&iq->qchase, qstate->return_msg->rep);
      if(rrset) {
            /* if CNAMEs have been followed - add new NS to delegpt. */
            /* BTW. RFC 1918 says NS should not have got CNAMEs. Robust. */
            if(!delegpt_find_ns(foriq->dp, rrset->rk.dname, 
                  rrset->rk.dname_len)) {
                  if(!delegpt_add_ns(foriq->dp, forq->region, 
                        rrset->rk.dname))
                        log_err("out of memory adding cnamed-ns");
            }
            if(!delegpt_add_rrset(foriq->dp, forq->region, rrset))
                  log_err("out of memory adding targets");
            verbose(VERB_ALGO, "added target response");
            delegpt_log(VERB_ALGO, foriq->dp);
      } else {
            verbose(VERB_ALGO, "iterator TargetResponse failed");
            dpns->resolved = 1; /* fail the target */
      }
}

/** 
 * This handles the final state for first-tier responses (i.e., responses to
 * externally generated queries).
 *
 * @param qstate: query state.
 * @param iq: iterator query state.
 * @param id: module id.
 * @return true if the event needs more processing, false if not. Since this
 *         is the final state for an event, it always returns false.
 */
static int
01523 processFinished(struct module_qstate* qstate, struct iter_qstate* iq,
      int id)
{
      log_query_info(VERB_QUERY, "finishing processing for", 
            &qstate->qinfo);

      if(!iq->response) {
            verbose(VERB_ALGO, "No response is set, servfail");
            return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
      }

      /* Make sure that the RA flag is set (since the presence of 
       * this module means that recursion is available) */
      iq->response->rep->flags |= BIT_RA;

      /* Clear the AA flag */
      /* FIXME: does this action go here or in some other module? */
      iq->response->rep->flags &= ~BIT_AA;

      /* make sure QR flag is on */
      iq->response->rep->flags |= BIT_QR;

      /* we have finished processing this query */
      qstate->ext_state[id] = module_finished;

      /* TODO:  we are using a private TTL, trim the response. */
      /* if (mPrivateTTL > 0){IterUtils.setPrivateTTL(resp, mPrivateTTL); } */

      /* prepend any items we have accumulated */
      if(iq->an_prepend_list || iq->ns_prepend_list) {
            if(!iter_prepend(iq, iq->response, qstate->region)) {
                  log_err("prepend rrsets: out of memory");
                  return error_response(qstate, id, LDNS_RCODE_SERVFAIL);
            }
            /* reset the query name back */
            iq->response->qinfo = qstate->qinfo;
            /* store message with the finished prepended items,
             * but only if we did recursion. The nonrecursion referral
             * from cache does not need to be stored in the msg cache. */
            if(qstate->query_flags&BIT_RD) {
                  if(!iter_dns_store(qstate->env, &qstate->qinfo, 
                        iq->response->rep, 0))
                        return error_response(qstate, id, 
                              LDNS_RCODE_SERVFAIL);
            }
      }
      qstate->return_rcode = LDNS_RCODE_NOERROR;
      qstate->return_msg = iq->response;
      return 0;
}

/*
 * Return priming query results to interestes super querystates.
 * 
 * Sets the delegation point and delegation message (not nonRD queries).
 * This is a callback from walk_supers.
 *
 * @param qstate: query state that finished.
 * @param id: module id.
 * @param super: the qstate to inform.
 */
void
01585 iter_inform_super(struct module_qstate* qstate, int id, 
      struct module_qstate* super)
{
      if(qstate->return_rcode != LDNS_RCODE_NOERROR)
            error_supers(qstate, id, super);
      else if(qstate->is_priming)
            prime_supers(qstate, id, super);
      else  processTargetResponse(qstate, id, super);
}

/**
 * Handle iterator state.
 * Handle events. This is the real processing loop for events, responsible
 * for moving events through the various states. If a processing method
 * returns true, then it will be advanced to the next state. If false, then
 * processing will stop.
 *
 * @param qstate: query state.
 * @param ie: iterator shared global environment.
 * @param iq: iterator query state.
 * @param id: module id.
 */
static void
01608 iter_handle(struct module_qstate* qstate, struct iter_qstate* iq,
      struct iter_env* ie, int id)
{
      int cont = 1;
      while(cont) {
            verbose(VERB_ALGO, "iter_handle processing q with state %s",
                  iter_state_to_string(iq->state));
            switch(iq->state) {
                  case INIT_REQUEST_STATE:
                        cont = processInitRequest(qstate, iq, ie, id);
                        break;
                  case INIT_REQUEST_2_STATE:
                        cont = processInitRequest2(qstate, iq, ie, id);
                        break;
                  case INIT_REQUEST_3_STATE:
                        cont = processInitRequest3(qstate, iq);
                        break;
                  case QUERYTARGETS_STATE:
                        cont = processQueryTargets(qstate, iq, ie, id);
                        break;
                  case QUERY_RESP_STATE:
                        cont = processQueryResponse(qstate, iq, id);
                        break;
                  case PRIME_RESP_STATE:
                        cont = processPrimeResponse(qstate, id);
                        break;
                  case FINISHED_STATE:
                        cont = processFinished(qstate, iq, id);
                        break;
                  default:
                        log_warn("iterator: invalid state: %d",
                              iq->state);
                        cont = 0;
                        break;
            }
      }
}

/** 
 * This is the primary entry point for processing request events. Note that
 * this method should only be used by external modules.
 * @param qstate: query state.
 * @param ie: iterator shared global environment.
 * @param iq: iterator query state.
 * @param id: module id.
 */
static void
01655 process_request(struct module_qstate* qstate, struct iter_qstate* iq,
      struct iter_env* ie, int id)
{
      /* external requests start in the INIT state, and finish using the
       * FINISHED state. */
      iq->state = INIT_REQUEST_STATE;
      iq->final_state = FINISHED_STATE;
      verbose(VERB_ALGO, "process_request: new external request event");
      iter_handle(qstate, iq, ie, id);
}

/** process authoritative server reply */
static void
01668 process_response(struct module_qstate* qstate, struct iter_qstate* iq, 
      struct iter_env* ie, int id, struct outbound_entry* outbound,
      enum module_ev event)
{
      struct msg_parse* prs;
      struct edns_data edns;
      ldns_buffer* pkt;

      verbose(VERB_ALGO, "process_response: new external response event");
      iq->response = NULL;
      iq->state = QUERY_RESP_STATE;
      if(event == module_event_noreply || event == module_event_error) {
            goto handle_it;
      }
      if(event != module_event_reply || !qstate->reply) {
            log_err("Bad event combined with response");
            outbound_list_remove(&iq->outlist, outbound);
            (void)error_response(qstate, id, LDNS_RCODE_SERVFAIL);
            return;
      }

      /* parse message */
      prs = (struct msg_parse*)regional_alloc(qstate->env->scratch, 
            sizeof(struct msg_parse));
      if(!prs) {
            log_err("out of memory on incoming message");
            /* like packet got dropped */
            goto handle_it;
      }
      memset(prs, 0, sizeof(*prs));
      memset(&edns, 0, sizeof(edns));
      pkt = qstate->reply->c->buffer;
      ldns_buffer_set_position(pkt, 0);
      if(parse_packet(pkt, prs, qstate->env->scratch) != LDNS_RCODE_NOERROR) {
            verbose(VERB_ALGO, "parse error on reply packet");
            goto handle_it;
      }
      /* edns is not examined, but removed from message to help cache */
      if(parse_extract_edns(prs, &edns) != LDNS_RCODE_NOERROR)
            goto handle_it;
      /* remove CD-bit, we asked for in case we handle validation ourself */
      prs->flags &= ~BIT_CD;

      /* normalize and sanitize: easy to delete items from linked lists */
      if(!scrub_message(pkt, prs, &iq->qchase, iq->dp->name, 
            qstate->env->scratch, qstate->env))
            goto handle_it;

      /* allocate response dns_msg in region */
      iq->response = dns_alloc_msg(pkt, prs, qstate->region);
      if(!iq->response)
            goto handle_it;
      log_query_info(VERB_DETAIL, "response for", &qstate->qinfo);
      log_name_addr(VERB_DETAIL, "reply from", iq->dp->name, 
            &qstate->reply->addr, qstate->reply->addrlen);
      if(verbosity >= VERB_ALGO)
            log_dns_msg("incoming scrubbed packet:", &iq->response->qinfo, 
                  iq->response->rep);

handle_it:
      outbound_list_remove(&iq->outlist, outbound);
      iter_handle(qstate, iq, ie, id);
}

void 
01733 iter_operate(struct module_qstate* qstate, enum module_ev event, int id,
      struct outbound_entry* outbound)
{
      struct iter_env* ie = (struct iter_env*)qstate->env->modinfo[id];
      struct iter_qstate* iq = (struct iter_qstate*)qstate->minfo[id];
      verbose(VERB_QUERY, "iterator[module %d] operate: extstate:%s event:%s", 
            id, strextstate(qstate->ext_state[id]), strmodulevent(event));
      if(iq) log_query_info(VERB_QUERY, "iterator operate: query", 
            &qstate->qinfo);
      if(iq && qstate->qinfo.qname != iq->qchase.qname)
            log_query_info(VERB_QUERY, "iterator operate: chased to", 
                  &iq->qchase);

      /* perform iterator state machine */
      if((event == module_event_new || event == module_event_pass) && 
            iq == NULL) {
            if(!iter_new(qstate, id)) {
                  (void)error_response(qstate, id, LDNS_RCODE_SERVFAIL);
                  return;
            }
            iq = (struct iter_qstate*)qstate->minfo[id];
            process_request(qstate, iq, ie, id);
            return;
      }
      if(iq && event == module_event_pass) {
            iter_handle(qstate, iq, ie, id);
            return;
      }
      if(iq && outbound) {
            process_response(qstate, iq, ie, id, outbound, event);
            return;
      }
      if(event == module_event_error) {
            verbose(VERB_ALGO, "got called with event error, giving up");
            (void)error_response(qstate, id, LDNS_RCODE_SERVFAIL);
            return;
      }

      log_err("bad event for iterator");
      (void)error_response(qstate, id, LDNS_RCODE_SERVFAIL);
}

void 
01776 iter_clear(struct module_qstate* qstate, int id)
{
      struct iter_qstate* iq;
      if(!qstate)
            return;
      iq = (struct iter_qstate*)qstate->minfo[id];
      if(iq) {
            outbound_list_clear(&iq->outlist);
            iq->num_current_queries = 0;
      }
      qstate->minfo[id] = NULL;
}

size_t 
01790 iter_get_mem(struct module_env* env, int id)
{
      struct iter_env* ie = (struct iter_env*)env->modinfo[id];
      if(!ie)
            return 0;
      return sizeof(*ie) + sizeof(int)*((size_t)ie->max_dependency_depth+1)
            + hints_get_mem(ie->hints) + forwards_get_mem(ie->fwds)
            + donotq_get_mem(ie->donotq);
}

/**
 * The iterator function block 
 */
01803 static struct module_func_block iter_block = {
      "iterator",
      &iter_init, &iter_deinit, &iter_operate, &iter_inform_super, 
      &iter_clear, &iter_get_mem
};

struct module_func_block* 
01810 iter_get_funcblock()
{
      return &iter_block;
}

const char* 
01816 iter_state_to_string(enum iter_state state)
{
      switch (state)
      {
      case INIT_REQUEST_STATE :
            return "INIT REQUEST STATE";
      case INIT_REQUEST_2_STATE :
            return "INIT REQUEST STATE (stage 2)";
      case INIT_REQUEST_3_STATE:
            return "INIT REQUEST STATE (stage 3)";
      case QUERYTARGETS_STATE :
            return "QUERY TARGETS STATE";
      case PRIME_RESP_STATE :
            return "PRIME RESPONSE STATE";
      case QUERY_RESP_STATE :
            return "QUERY RESPONSE STATE";
      case FINISHED_STATE :
            return "FINISHED RESPONSE STATE";
      default :
            return "UNKNOWN ITER STATE";
      }
}

int 
01840 iter_state_is_responsestate(enum iter_state s)
{
      switch(s) {
            case INIT_REQUEST_STATE :
            case INIT_REQUEST_2_STATE :
            case INIT_REQUEST_3_STATE :
            case QUERYTARGETS_STATE :
                  return 0;
            default:
                  break;
      }
      return 1;
}

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