/*
 * iterator/iter_utils.c - iterative resolver module utility functions.
 *
 * 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 the iterator module.
 * Configuration options. Forward zones.
 */
#include "config.h"
#include "iterator/iter_utils.h"
#include "iterator/iterator.h"
#include "iterator/iter_hints.h"
#include "iterator/iter_fwd.h"
#include "iterator/iter_donotq.h"
#include "iterator/iter_delegpt.h"
#include "iterator/iter_priv.h"
#include "services/cache/infra.h"
#include "services/cache/dns.h"
#include "services/cache/rrset.h"
#include "services/outside_network.h"
#include "util/net_help.h"
#include "util/module.h"
#include "util/log.h"
#include "util/config_file.h"
#include "util/regional.h"
#include "util/data/msgparse.h"
#include "util/data/dname.h"
#include "util/random.h"
#include "util/fptr_wlist.h"
#include "validator/val_anchor.h"
#include "validator/val_kcache.h"
#include "validator/val_kentry.h"
#include "validator/val_utils.h"
#include "validator/val_sigcrypt.h"
#include "sldns/sbuffer.h"
#include "sldns/str2wire.h"

/** time when nameserver glue is said to be 'recent' */
#define SUSPICION_RECENT_EXPIRY 86400

/** if NAT64 is enabled and no NAT64 prefix is configured, first fall back to
 * DNS64 prefix.  If that is not configured, fall back to this default value.
 */
static const char DEFAULT_NAT64_PREFIX[] = "64:ff9b::/96";

/** fillup fetch policy array */
static int
fetch_fill(int* target_fetch_policy, int max_dependency_depth, const char* str)
{
        char* s = (char*)str, *e;
        int i;
        for(i=0; i<max_dependency_depth+1; i++) {
                target_fetch_policy[i] = strtol(s, &e, 10);
                if(s == e) {
                        log_err("cannot parse fetch policy number %s", s);
                        return 0;
                }
                s = e;
        }
        return 1;
}

/** Read config string that represents the target fetch policy */
int
read_fetch_policy(int** target_fetch_policy, int* max_dependency_depth,
        const char* str)
{
        int count = cfg_count_numbers(str);
        if(count < 1) {
                log_err("Cannot parse target fetch policy: \"%s\"", str);
                return 0;
        }
        *max_dependency_depth = count - 1;
        *target_fetch_policy = (int*)calloc(
                (size_t)(*max_dependency_depth)+1, sizeof(int));
        if(!*target_fetch_policy) {
                log_err("alloc fetch policy: out of memory");
                return 0;
        }
        if(!fetch_fill(*target_fetch_policy, *max_dependency_depth, str))
                return 0;
        return 1;
}

struct rbtree_type*
caps_white_create(void)
{
        struct rbtree_type* caps_white = rbtree_create(name_tree_compare);
        if(!caps_white)
                log_err("out of memory");
        return caps_white;
}

/** delete caps_whitelist element */
static void
caps_free(struct rbnode_type* n, void* ATTR_UNUSED(d))
{
        if(n) {
                free(((struct name_tree_node*)n)->name);
                free(n);
        }
}

void
caps_white_delete(struct rbtree_type* caps_white)
{
        if(!caps_white)
                return;
        traverse_postorder(caps_white, caps_free, NULL);
        free(caps_white);
}

int
caps_white_apply_cfg(rbtree_type* ntree, struct config_file* cfg)
{
        struct config_strlist* p;
        for(p=cfg->caps_whitelist; p; p=p->next) {
                struct name_tree_node* n;
                size_t len;
                uint8_t* nm = sldns_str2wire_dname(p->str, &len);
                if(!nm) {
                        log_err("could not parse %s", p->str);
                        return 0;
                }
                n = (struct name_tree_node*)calloc(1, sizeof(*n));
                if(!n) {
                        log_err("out of memory");
                        free(nm);
                        return 0;
                }
                n->node.key = n;
                n->name = nm;
                n->len = len;
                n->labs = dname_count_labels(nm);
                n->dclass = LDNS_RR_CLASS_IN;
                if(!name_tree_insert(ntree, n, nm, len, n->labs, n->dclass)) {
                        /* duplicate element ignored, idempotent */
                        free(n->name);
                        free(n);
                }
        }
        name_tree_init_parents(ntree);
        return 1;
}

int
nat64_apply_cfg(struct iter_nat64* nat64, struct config_file* cfg)
{
        const char *nat64_prefix;

        nat64_prefix = cfg->nat64_prefix;
        if(!nat64_prefix)
                nat64_prefix = cfg->dns64_prefix;
        if(!nat64_prefix)
                nat64_prefix = DEFAULT_NAT64_PREFIX;
        if(!netblockstrtoaddr(nat64_prefix, 0, &nat64->nat64_prefix_addr,
                &nat64->nat64_prefix_addrlen, &nat64->nat64_prefix_net)) {
                log_err("cannot parse nat64-prefix netblock: %s", nat64_prefix);
                return 0;
        }
        if(!addr_is_ip6(&nat64->nat64_prefix_addr,
                nat64->nat64_prefix_addrlen)) {
                log_err("nat64-prefix is not IPv6: %s", cfg->nat64_prefix);
                return 0;
        }
        if(!prefixnet_is_nat64(nat64->nat64_prefix_net)) {
                log_err("nat64-prefix length it not 32, 40, 48, 56, 64 or 96: %s",
                        nat64_prefix);
                return 0;
        }
        nat64->use_nat64 = cfg->do_nat64;
        return 1;
}

int
iter_apply_cfg(struct iter_env* iter_env, struct config_file* cfg)
{
        int i;
        /* target fetch policy */
        if(!read_fetch_policy(&iter_env->target_fetch_policy,
                &iter_env->max_dependency_depth, cfg->target_fetch_policy))
                return 0;
        for(i=0; i<iter_env->max_dependency_depth+1; i++)
                verbose(VERB_QUERY, "target fetch policy for level %d is %d",
                        i, iter_env->target_fetch_policy[i]);

        if(!iter_env->donotq)
                iter_env->donotq = donotq_create();
        if(!iter_env->donotq || !donotq_apply_cfg(iter_env->donotq, cfg)) {
                log_err("Could not set donotqueryaddresses");
                return 0;
        }
        if(!iter_env->priv)
                iter_env->priv = priv_create();
        if(!iter_env->priv || !priv_apply_cfg(iter_env->priv, cfg)) {
                log_err("Could not set private addresses");
                return 0;
        }
        if(cfg->caps_whitelist) {
                if(!iter_env->caps_white)
                        iter_env->caps_white = caps_white_create();
                if(!iter_env->caps_white || !caps_white_apply_cfg(
                        iter_env->caps_white, cfg)) {
                        log_err("Could not set capsforid whitelist");
                        return 0;
                }

        }

        if(!nat64_apply_cfg(&iter_env->nat64, cfg)) {
                log_err("Could not setup nat64");
                return 0;
        }

        iter_env->supports_ipv6 = cfg->do_ip6;
        iter_env->supports_ipv4 = cfg->do_ip4;
        iter_env->outbound_msg_retry = cfg->outbound_msg_retry;
        iter_env->max_sent_count = cfg->max_sent_count;
        iter_env->max_query_restarts = cfg->max_query_restarts;
        return 1;
}

/** filter out unsuitable targets
 * @param iter_env: iterator environment with ipv6-support flag.
 * @param env: module environment with infra cache.
 * @param name: zone name
 * @param namelen: length of name
 * @param qtype: query type (host order).
 * @param now: current time
 * @param a: address in delegation point we are examining.
 * @return an integer that signals the target suitability.
 *      as follows:
 *      -1: The address should be omitted from the list.
 *          Because:
 *              o The address is bogus (DNSSEC validation failure).
 *              o Listed as donotquery
 *              o is ipv6 but no ipv6 support (in operating system).
 *              o is ipv4 but no ipv4 support (in operating system).
 *              o is lame
 *      Otherwise, an rtt in milliseconds.
 *      0 .. USEFUL_SERVER_TOP_TIMEOUT-1
 *              The roundtrip time timeout estimate. less than 2 minutes.
 *              Note that util/rtt.c has a MIN_TIMEOUT of 50 msec, thus
 *              values 0 .. 49 are not used, unless that is changed.
 *      USEFUL_SERVER_TOP_TIMEOUT
 *              This value exactly is given for unresponsive blacklisted.
 *      USEFUL_SERVER_TOP_TIMEOUT+1
 *              For non-blacklisted servers: huge timeout, but has traffic.
 *      USEFUL_SERVER_TOP_TIMEOUT*1 ..
 *              parent-side lame servers get this penalty. A dispreferential
 *              server. (lame in delegpt).
 *      USEFUL_SERVER_TOP_TIMEOUT*2 ..
 *              dnsseclame servers get penalty
 *      USEFUL_SERVER_TOP_TIMEOUT*3 ..
 *              recursion lame servers get penalty
 *      UNKNOWN_SERVER_NICENESS
 *              If no information is known about the server, this is
 *              returned. 376 msec or so.
 *      +BLACKLIST_PENALTY (of USEFUL_TOP_TIMEOUT*4) for dnssec failed IPs.
 *
 * When a final value is chosen that is dnsseclame ; dnsseclameness checking
 * is turned off (so we do not discard the reply).
 * When a final value is chosen that is recursionlame; RD bit is set on query.
 * Because of the numbers this means recursionlame also have dnssec lameness
 * checking turned off.
 */
static int
iter_filter_unsuitable(struct iter_env* iter_env, struct module_env* env,
        uint8_t* name, size_t namelen, uint16_t qtype, time_t now,
        struct delegpt_addr* a)
{
        int rtt, lame, reclame, dnsseclame;
        if(a->bogus)
                return -1; /* address of server is bogus */
        if(donotq_lookup(iter_env->donotq, &a->addr, a->addrlen)) {
                log_addr(VERB_ALGO, "skip addr on the donotquery list",
                        &a->addr, a->addrlen);
                return -1; /* server is on the donotquery list */
        }
        if(!iter_env->supports_ipv6 && addr_is_ip6(&a->addr, a->addrlen)) {
                return -1; /* there is no ip6 available */
        }
        if(!iter_env->supports_ipv4 && !iter_env->nat64.use_nat64 &&
           !addr_is_ip6(&a->addr, a->addrlen)) {
                return -1; /* there is no ip4 available */
        }
        /* check lameness - need zone , class info */
        if(infra_get_lame_rtt(env->infra_cache, &a->addr, a->addrlen,
                name, namelen, qtype, &lame, &dnsseclame, &reclame,
                &rtt, now)) {
                log_addr(VERB_ALGO, "servselect", &a->addr, a->addrlen);
                verbose(VERB_ALGO, "   rtt=%d%s%s%s%s%s", rtt,
                        lame?" LAME":"",
                        dnsseclame?" DNSSEC_LAME":"",
                        a->dnsseclame?" ADDR_DNSSEC_LAME":"",
                        reclame?" REC_LAME":"",
                        a->lame?" ADDR_LAME":"");
                if(lame)
                        return -1; /* server is lame */
                else if(rtt >= USEFUL_SERVER_TOP_TIMEOUT)
                        /* server is unresponsive,
                         * we used to return TOP_TIMEOUT, but fairly useless,
                         * because if == TOP_TIMEOUT is dropped because
                         * blacklisted later, instead, remove it here, so
                         * other choices (that are not blacklisted) can be
                         * tried */
                        return -1;
                /* select remainder from worst to best */
                else if(reclame)
                        return rtt+USEFUL_SERVER_TOP_TIMEOUT*3; /* nonpref */
                else if(dnsseclame || a->dnsseclame)
                        return rtt+USEFUL_SERVER_TOP_TIMEOUT*2; /* nonpref */
                else if(a->lame)
                        return rtt+USEFUL_SERVER_TOP_TIMEOUT+1; /* nonpref */
                else    return rtt;
        }
        /* no server information present */
        if(a->dnsseclame)
                return UNKNOWN_SERVER_NICENESS+USEFUL_SERVER_TOP_TIMEOUT*2; /* nonpref */
        else if(a->lame)
                return USEFUL_SERVER_TOP_TIMEOUT+1+UNKNOWN_SERVER_NICENESS; /* nonpref */
        return UNKNOWN_SERVER_NICENESS;
}

/** lookup RTT information, and also store fastest rtt (if any) */
static int
iter_fill_rtt(struct iter_env* iter_env, struct module_env* env,
        uint8_t* name, size_t namelen, uint16_t qtype, time_t now,
        struct delegpt* dp, int* best_rtt, struct sock_list* blacklist,
        size_t* num_suitable_results)
{
        int got_it = 0;
        struct delegpt_addr* a;
        *num_suitable_results = 0;

        if(dp->bogus)
                return 0; /* NS bogus, all bogus, nothing found */
        for(a=dp->result_list; a; a = a->next_result) {
                a->sel_rtt = iter_filter_unsuitable(iter_env, env,
                        name, namelen, qtype, now, a);
                if(a->sel_rtt != -1) {
                        if(sock_list_find(blacklist, &a->addr, a->addrlen))
                                a->sel_rtt += BLACKLIST_PENALTY;

                        if(!got_it) {
                                *best_rtt = a->sel_rtt;
                                got_it = 1;
                        } else if(a->sel_rtt < *best_rtt) {
                                *best_rtt = a->sel_rtt;
                        }
                        (*num_suitable_results)++;
                }
        }
        return got_it;
}

/** compare two rtts, return -1, 0 or 1 */
static int
rtt_compare(const void* x, const void* y)
{
        if(*(int*)x == *(int*)y)
                return 0;
        if(*(int*)x > *(int*)y)
                return 1;
        return -1;
}

/** get RTT for the Nth fastest server */
static int
nth_rtt(struct delegpt_addr* result_list, size_t num_results, size_t n)
{
        int rtt_band;
        size_t i;
        int* rtt_list, *rtt_index;

        if(num_results < 1 || n >= num_results) {
                return -1;
        }

        rtt_list = calloc(num_results, sizeof(int));
        if(!rtt_list) {
                log_err("malloc failure: allocating rtt_list");
                return -1;
        }
        rtt_index = rtt_list;

        for(i=0; i<num_results && result_list; i++) {
                if(result_list->sel_rtt != -1) {
                        *rtt_index = result_list->sel_rtt;
                        rtt_index++;
                }
                result_list=result_list->next_result;
        }
        qsort(rtt_list, num_results, sizeof(*rtt_list), rtt_compare);

        log_assert(n > 0);
        rtt_band = rtt_list[n-1];
        free(rtt_list);

        return rtt_band;
}

/** filter the address list, putting best targets at front,
 * returns number of best targets (or 0, no suitable targets) */
static int
iter_filter_order(struct iter_env* iter_env, struct module_env* env,
        uint8_t* name, size_t namelen, uint16_t qtype, time_t now,
        struct delegpt* dp, int* selected_rtt, int open_target,
        struct sock_list* blacklist, time_t prefetch)
{
        int got_num = 0, low_rtt = 0, swap_to_front, rtt_band = RTT_BAND, nth;
        int alllame = 0;
        size_t num_results;
        struct delegpt_addr* a, *n, *prev=NULL;

        /* fillup sel_rtt and find best rtt in the bunch */
        got_num = iter_fill_rtt(iter_env, env, name, namelen, qtype, now, dp,
                &low_rtt, blacklist, &num_results);
        if(got_num == 0)
                return 0;
        if(low_rtt >= USEFUL_SERVER_TOP_TIMEOUT &&
                /* If all missing (or not fully resolved) targets are lame,
                 * then use the remaining lame address. */
                ((delegpt_count_missing_targets(dp, &alllame) > 0 && !alllame) ||
                open_target > 0)) {
                verbose(VERB_ALGO, "Bad choices, trying to get more choice");
                return 0; /* we want more choice. The best choice is a bad one.
                             return 0 to force the caller to fetch more */
        }

        if(env->cfg->fast_server_permil != 0 && prefetch == 0 &&
                num_results > env->cfg->fast_server_num &&
                ub_random_max(env->rnd, 1000) < env->cfg->fast_server_permil) {
                /* the query is not prefetch, but for a downstream client,
                 * there are more servers available then the fastest N we want
                 * to choose from. Limit our choice to the fastest servers. */
                nth = nth_rtt(dp->result_list, num_results,
                        env->cfg->fast_server_num);
                if(nth > 0) {
                        rtt_band = nth - low_rtt;
                        if(rtt_band > RTT_BAND)
                                rtt_band = RTT_BAND;
                }
        }

        got_num = 0;
        a = dp->result_list;
        while(a) {
                /* skip unsuitable targets */
                if(a->sel_rtt == -1) {
                        prev = a;
                        a = a->next_result;
                        continue;
                }
                /* classify the server address and determine what to do */
                swap_to_front = 0;
                if(a->sel_rtt >= low_rtt && a->sel_rtt - low_rtt <= rtt_band) {
                        got_num++;
                        swap_to_front = 1;
                } else if(a->sel_rtt<low_rtt && low_rtt-a->sel_rtt<=rtt_band) {
                        got_num++;
                        swap_to_front = 1;
                }
                /* swap to front if necessary, or move to next result */
                if(swap_to_front && prev) {
                        n = a->next_result;
                        prev->next_result = n;
                        a->next_result = dp->result_list;
                        dp->result_list = a;
                        a = n;
                } else {
                        prev = a;
                        a = a->next_result;
                }
        }
        *selected_rtt = low_rtt;

        if (env->cfg->prefer_ip6) {
                int got_num6 = 0;
                int low_rtt6 = 0;
                int i;
                int attempt = -1; /* filter to make sure addresses have
                  less attempts on them than the first, to force round
                  robin when all the IPv6 addresses fail */
                int num4ok = 0; /* number ip4 at low attempt count */
                int num4_lowrtt = 0;
                prev = NULL;
                a = dp->result_list;
                for(i = 0; i < got_num; i++) {
                        if(!a) break; /* robustness */
                        swap_to_front = 0;
                        if(a->addr.ss_family != AF_INET6 && attempt == -1) {
                                /* if we only have ip4 at low attempt count,
                                 * then ip6 is failing, and we need to
                                 * select one of the remaining IPv4 addrs */
                                attempt = a->attempts;
                                num4ok++;
                                num4_lowrtt = a->sel_rtt;
                        } else if(a->addr.ss_family != AF_INET6 && attempt == a->attempts) {
                                num4ok++;
                                if(num4_lowrtt == 0 || a->sel_rtt < num4_lowrtt) {
                                        num4_lowrtt = a->sel_rtt;
                                }
                        }
                        if(a->addr.ss_family == AF_INET6) {
                                if(attempt == -1) {
                                        attempt = a->attempts;
                                } else if(a->attempts > attempt) {
                                        break;
                                }
                                got_num6++;
                                swap_to_front = 1;
                                if(low_rtt6 == 0 || a->sel_rtt < low_rtt6) {
                                        low_rtt6 = a->sel_rtt;
                                }
                        }
                        /* swap to front if IPv6, or move to next result */
                        if(swap_to_front && prev) {
                                n = a->next_result;
                                prev->next_result = n;
                                a->next_result = dp->result_list;
                                dp->result_list = a;
                                a = n;
                        } else {
                                prev = a;
                                a = a->next_result;
                        }
                }
                if(got_num6 > 0) {
                        got_num = got_num6;
                        *selected_rtt = low_rtt6;
                } else if(num4ok > 0) {
                        got_num = num4ok;
                        *selected_rtt = num4_lowrtt;
                }
        } else if (env->cfg->prefer_ip4) {
                int got_num4 = 0;
                int low_rtt4 = 0;
                int i;
                int attempt = -1; /* filter to make sure addresses have
                  less attempts on them than the first, to force round
                  robin when all the IPv4 addresses fail */
                int num6ok = 0; /* number ip6 at low attempt count */
                int num6_lowrtt = 0;
                prev = NULL;
                a = dp->result_list;
                for(i = 0; i < got_num; i++) {
                        if(!a) break; /* robustness */
                        swap_to_front = 0;
                        if(a->addr.ss_family != AF_INET && attempt == -1) {
                                /* if we only have ip6 at low attempt count,
                                 * then ip4 is failing, and we need to
                                 * select one of the remaining IPv6 addrs */
                                attempt = a->attempts;
                                num6ok++;
                                num6_lowrtt = a->sel_rtt;
                        } else if(a->addr.ss_family != AF_INET && attempt == a->attempts) {
                                num6ok++;
                                if(num6_lowrtt == 0 || a->sel_rtt < num6_lowrtt) {
                                        num6_lowrtt = a->sel_rtt;
                                }
                        }
                        if(a->addr.ss_family == AF_INET) {
                                if(attempt == -1) {
                                        attempt = a->attempts;
                                } else if(a->attempts > attempt) {
                                        break;
                                }
                                got_num4++;
                                swap_to_front = 1;
                                if(low_rtt4 == 0 || a->sel_rtt < low_rtt4) {
                                        low_rtt4 = a->sel_rtt;
                                }
                        }
                        /* swap to front if IPv4, or move to next result */
                        if(swap_to_front && prev) {
                                n = a->next_result;
                                prev->next_result = n;
                                a->next_result = dp->result_list;
                                dp->result_list = a;
                                a = n;
                        } else {
                                prev = a;
                                a = a->next_result;
                        }
                }
                if(got_num4 > 0) {
                        got_num = got_num4;
                        *selected_rtt = low_rtt4;
                } else if(num6ok > 0) {
                        got_num = num6ok;
                        *selected_rtt = num6_lowrtt;
                }
        }
        return got_num;
}

struct delegpt_addr*
iter_server_selection(struct iter_env* iter_env,
        struct module_env* env, struct delegpt* dp,
        uint8_t* name, size_t namelen, uint16_t qtype, int* dnssec_lame,
        int* chase_to_rd, int open_target, struct sock_list* blacklist,
        time_t prefetch)
{
        int sel;
        int selrtt;
        struct delegpt_addr* a, *prev;
        int num = iter_filter_order(iter_env, env, name, namelen, qtype,
                *env->now, dp, &selrtt, open_target, blacklist, prefetch);

        if(num == 0)
                return NULL;
        verbose(VERB_ALGO, "selrtt %d", selrtt);
        if(selrtt > BLACKLIST_PENALTY) {
                if(selrtt-BLACKLIST_PENALTY > USEFUL_SERVER_TOP_TIMEOUT*3) {
                        verbose(VERB_ALGO, "chase to "
                                "blacklisted recursion lame server");
                        *chase_to_rd = 1;
                }
                if(selrtt-BLACKLIST_PENALTY > USEFUL_SERVER_TOP_TIMEOUT*2) {
                        verbose(VERB_ALGO, "chase to "
                                "blacklisted dnssec lame server");
                        *dnssec_lame = 1;
                }
        } else {
                if(selrtt > USEFUL_SERVER_TOP_TIMEOUT*3) {
                        verbose(VERB_ALGO, "chase to recursion lame server");
                        *chase_to_rd = 1;
                }
                if(selrtt > USEFUL_SERVER_TOP_TIMEOUT*2) {
                        verbose(VERB_ALGO, "chase to dnssec lame server");
                        *dnssec_lame = 1;
                }
                if(selrtt == USEFUL_SERVER_TOP_TIMEOUT) {
                        verbose(VERB_ALGO, "chase to blacklisted lame server");
                        return NULL;
                }
        }

        if(num == 1) {
                a = dp->result_list;
                if(++a->attempts < iter_env->outbound_msg_retry)
                        return a;
                dp->result_list = a->next_result;
                return a;
        }

        /* randomly select a target from the list */
        log_assert(num > 1);
        /* grab secure random number, to pick unexpected server.
         * also we need it to be threadsafe. */
        sel = ub_random_max(env->rnd, num);
        a = dp->result_list;
        prev = NULL;
        while(sel > 0 && a) {
                prev = a;
                a = a->next_result;
                sel--;
        }
        if(!a)  /* robustness */
                return NULL;
        if(++a->attempts < iter_env->outbound_msg_retry)
                return a;
        /* remove it from the delegation point result list */
        if(prev)
                prev->next_result = a->next_result;
        else    dp->result_list = a->next_result;
        return a;
}

struct dns_msg*
dns_alloc_msg(sldns_buffer* pkt, struct msg_parse* msg,
        struct regional* region)
{
        struct dns_msg* m = (struct dns_msg*)regional_alloc(region,
                sizeof(struct dns_msg));
        if(!m)
                return NULL;
        memset(m, 0, sizeof(*m));
        if(!parse_create_msg(pkt, msg, NULL, &m->qinfo, &m->rep, region)) {
                log_err("malloc failure: allocating incoming dns_msg");
                return NULL;
        }
        return m;
}

struct dns_msg*
dns_copy_msg(struct dns_msg* from, struct regional* region)
{
        struct dns_msg* m = (struct dns_msg*)regional_alloc(region,
                sizeof(struct dns_msg));
        if(!m)
                return NULL;
        m->qinfo = from->qinfo;
        if(!(m->qinfo.qname = regional_alloc_init(region, from->qinfo.qname,
                from->qinfo.qname_len)))
                return NULL;
        if(!(m->rep = reply_info_copy(from->rep, NULL, region)))
                return NULL;
        return m;
}

void
iter_dns_store(struct module_env* env, struct query_info* msgqinf,
        struct reply_info* msgrep, int is_referral, time_t leeway, int pside,
        struct regional* region, uint16_t flags, time_t qstarttime,
        int is_valrec)
{
        if(!dns_cache_store(env, msgqinf, msgrep, is_referral, leeway,
                pside, region, flags, qstarttime, is_valrec))
                log_err("out of memory: cannot store data in cache");
}

int
iter_ns_probability(struct ub_randstate* rnd, int n, int m)
{
        int sel;
        if(n == m) /* 100% chance */
                return 1;
        /* we do not need secure random numbers here, but
         * we do need it to be threadsafe, so we use this */
        sel = ub_random_max(rnd, m);
        return (sel < n);
}

/** detect dependency cycle for query and target */
static int
causes_cycle(struct module_qstate* qstate, uint8_t* name, size_t namelen,
        uint16_t t, uint16_t c)
{
        struct query_info qinf;
        qinf.qname = name;
        qinf.qname_len = namelen;
        qinf.qtype = t;
        qinf.qclass = c;
        qinf.local_alias = NULL;
        fptr_ok(fptr_whitelist_modenv_detect_cycle(
                qstate->env->detect_cycle));
        return (*qstate->env->detect_cycle)(qstate, &qinf,
                (uint16_t)(BIT_RD|BIT_CD), qstate->is_priming,
                qstate->is_valrec);
}

void
iter_mark_cycle_targets(struct module_qstate* qstate, struct delegpt* dp)
{
        struct delegpt_ns* ns;
        for(ns = dp->nslist; ns; ns = ns->next) {
                if(ns->resolved)
                        continue;
                /* see if this ns as target causes dependency cycle */
                if(causes_cycle(qstate, ns->name, ns->namelen,
                        LDNS_RR_TYPE_AAAA, qstate->qinfo.qclass) ||
                   causes_cycle(qstate, ns->name, ns->namelen,
                        LDNS_RR_TYPE_A, qstate->qinfo.qclass)) {
                        log_nametypeclass(VERB_QUERY, "skipping target due "
                                "to dependency cycle (harden-glue: no may "
                                "fix some of the cycles)",
                                ns->name, LDNS_RR_TYPE_A,
                                qstate->qinfo.qclass);
                        ns->resolved = 1;
                }
        }
}

void
iter_mark_pside_cycle_targets(struct module_qstate* qstate, struct delegpt* dp)
{
        struct delegpt_ns* ns;
        for(ns = dp->nslist; ns; ns = ns->next) {
                if(ns->done_pside4 && ns->done_pside6)
                        continue;
                /* see if this ns as target causes dependency cycle */
                if(causes_cycle(qstate, ns->name, ns->namelen,
                        LDNS_RR_TYPE_A, qstate->qinfo.qclass)) {
                        log_nametypeclass(VERB_QUERY, "skipping target due "
                                "to dependency cycle", ns->name,
                                LDNS_RR_TYPE_A, qstate->qinfo.qclass);
                        ns->done_pside4 = 1;
                }
                if(causes_cycle(qstate, ns->name, ns->namelen,
                        LDNS_RR_TYPE_AAAA, qstate->qinfo.qclass)) {
                        log_nametypeclass(VERB_QUERY, "skipping target due "
                                "to dependency cycle", ns->name,
                                LDNS_RR_TYPE_AAAA, qstate->qinfo.qclass);
                        ns->done_pside6 = 1;
                }
        }
}

int
iter_dp_is_useless(struct query_info* qinfo, uint16_t qflags,
        struct delegpt* dp, int supports_ipv4, int supports_ipv6,
        int use_nat64)
{
        struct delegpt_ns* ns;
        struct delegpt_addr* a;

        if(supports_ipv6 && use_nat64)
                supports_ipv4 = 1;

        /* check:
         *      o RD qflag is on.
         *      o no addresses are provided.
         *      o all NS items are required glue.
         * OR
         *      o RD qflag is on.
         *      o no addresses are provided.
         *      o the query is for one of the nameservers in dp,
         *        and that nameserver is a glue-name for this dp.
         */
        if(!(qflags&BIT_RD))
                return 0;
        /* either available or unused targets,
         * if they exist, the dp is not useless. */
        for(a = dp->usable_list; a; a = a->next_usable) {
                if(!addr_is_ip6(&a->addr, a->addrlen) && supports_ipv4)
                        return 0;
                else if(addr_is_ip6(&a->addr, a->addrlen) && supports_ipv6)
                        return 0;
        }
        for(a = dp->result_list; a; a = a->next_result) {
                if(!addr_is_ip6(&a->addr, a->addrlen) && supports_ipv4)
                        return 0;
                else if(addr_is_ip6(&a->addr, a->addrlen) && supports_ipv6)
                        return 0;
        }

        /* see if query is for one of the nameservers, which is glue */
        if( ((qinfo->qtype == LDNS_RR_TYPE_A && supports_ipv4) ||
                (qinfo->qtype == LDNS_RR_TYPE_AAAA && supports_ipv6)) &&
                dname_subdomain_c(qinfo->qname, dp->name) &&
                delegpt_find_ns(dp, qinfo->qname, qinfo->qname_len))
                return 1;

        for(ns = dp->nslist; ns; ns = ns->next) {
                if(ns->resolved) /* skip failed targets */
                        continue;
                if(!dname_subdomain_c(ns->name, dp->name))
                        return 0; /* one address is not required glue */
        }
        return 1;
}

int
iter_qname_indicates_dnssec(struct module_env* env, struct query_info *qinfo)
{
        struct trust_anchor* a;
        if(!env || !env->anchors || !qinfo || !qinfo->qname)
                return 0;
        /* a trust anchor exists above the name? */
        if((a=anchors_lookup(env->anchors, qinfo->qname, qinfo->qname_len,
                qinfo->qclass))) {
                if(a->numDS == 0 && a->numDNSKEY == 0) {
                        /* insecure trust point */
                        lock_basic_unlock(&a->lock);
                        return 0;
                }
                lock_basic_unlock(&a->lock);
                return 1;
        }
        /* no trust anchor above it. */
        return 0;
}

int
iter_indicates_dnssec(struct module_env* env, struct delegpt* dp,
        struct dns_msg* msg, uint16_t dclass)
{
        struct trust_anchor* a;
        /* information not available, !env->anchors can be common */
        if(!env || !env->anchors || !dp || !dp->name)
                return 0;
        /* a trust anchor exists with this name, RRSIGs expected */
        if((a=anchor_find(env->anchors, dp->name, dp->namelabs, dp->namelen,
                dclass))) {
                if(a->numDS == 0 && a->numDNSKEY == 0) {
                        /* insecure trust point */
                        lock_basic_unlock(&a->lock);
                        return 0;
                }
                lock_basic_unlock(&a->lock);
                return 1;
        }
        /* see if DS rrset was given, in AUTH section */
        if(msg && msg->rep &&
                reply_find_rrset_section_ns(msg->rep, dp->name, dp->namelen,
                LDNS_RR_TYPE_DS, dclass))
                return 1;
        /* look in key cache */
        if(env->key_cache) {
                struct key_entry_key* kk = key_cache_obtain(env->key_cache,
                        dp->name, dp->namelen, dclass, env->scratch, *env->now);
                if(kk) {
                        if(query_dname_compare(kk->name, dp->name) == 0) {
                          if(key_entry_isgood(kk) || key_entry_isbad(kk)) {
                                regional_free_all(env->scratch);
                                return 1;
                          } else if(key_entry_isnull(kk)) {
                                regional_free_all(env->scratch);
                                return 0;
                          }
                        }
                        regional_free_all(env->scratch);
                }
        }
        return 0;
}

int
iter_msg_has_dnssec(struct dns_msg* msg)
{
        size_t i;
        if(!msg || !msg->rep)
                return 0;
        for(i=0; i<msg->rep->an_numrrsets + msg->rep->ns_numrrsets; i++) {
                if(((struct packed_rrset_data*)msg->rep->rrsets[i]->
                        entry.data)->rrsig_count > 0)
                        return 1;
        }
        /* empty message has no DNSSEC info, with DNSSEC the reply is
         * not empty (NSEC) */
        return 0;
}

int iter_msg_from_zone(struct dns_msg* msg, struct delegpt* dp,
        enum response_type type, uint16_t dclass)
{
        if(!msg || !dp || !msg->rep || !dp->name)
                return 0;
        /* SOA RRset - always from reply zone */
        if(reply_find_rrset_section_an(msg->rep, dp->name, dp->namelen,
                LDNS_RR_TYPE_SOA, dclass) ||
           reply_find_rrset_section_ns(msg->rep, dp->name, dp->namelen,
                LDNS_RR_TYPE_SOA, dclass))
                return 1;
        if(type == RESPONSE_TYPE_REFERRAL) {
                size_t i;
                /* if it adds a single label, i.e. we expect .com,
                 * and referral to example.com. NS ... , then origin zone
                 * is .com. For a referral to sub.example.com. NS ... then
                 * we do not know, since example.com. may be in between. */
                for(i=0; i<msg->rep->an_numrrsets+msg->rep->ns_numrrsets;
                        i++) {
                        struct ub_packed_rrset_key* s = msg->rep->rrsets[i];
                        if(ntohs(s->rk.type) == LDNS_RR_TYPE_NS &&
                                ntohs(s->rk.rrset_class) == dclass) {
                                int l = dname_count_labels(s->rk.dname);
                                if(l == dp->namelabs + 1 &&
                                        dname_strict_subdomain(s->rk.dname,
                                        l, dp->name, dp->namelabs))
                                        return 1;
                        }
                }
                return 0;
        }
        log_assert(type==RESPONSE_TYPE_ANSWER || type==RESPONSE_TYPE_CNAME);
        /* not a referral, and not lame delegation (upwards), so,
         * any NS rrset must be from the zone itself */
        if(reply_find_rrset_section_an(msg->rep, dp->name, dp->namelen,
                LDNS_RR_TYPE_NS, dclass) ||
           reply_find_rrset_section_ns(msg->rep, dp->name, dp->namelen,
                LDNS_RR_TYPE_NS, dclass))
                return 1;
        /* a DNSKEY set is expected at the zone apex as well */
        /* this is for 'minimal responses' for DNSKEYs */
        if(reply_find_rrset_section_an(msg->rep, dp->name, dp->namelen,
                LDNS_RR_TYPE_DNSKEY, dclass))
                return 1;
        return 0;
}

/**
 * check equality of two rrsets
 * @param k1: rrset
 * @param k2: rrset
 * @return true if equal
 */
static int
rrset_equal(struct ub_packed_rrset_key* k1, struct ub_packed_rrset_key* k2)
{
        struct packed_rrset_data* d1 = (struct packed_rrset_data*)
                k1->entry.data;
        struct packed_rrset_data* d2 = (struct packed_rrset_data*)
                k2->entry.data;
        size_t i, t;
        if(k1->rk.dname_len != k2->rk.dname_len ||
                k1->rk.flags != k2->rk.flags ||
                k1->rk.type != k2->rk.type ||
                k1->rk.rrset_class != k2->rk.rrset_class ||
                query_dname_compare(k1->rk.dname, k2->rk.dname) != 0)
                return 0;
        if(     /* do not check ttl: d1->ttl != d2->ttl || */
                d1->count != d2->count ||
                d1->rrsig_count != d2->rrsig_count ||
                d1->trust != d2->trust ||
                d1->security != d2->security)
                return 0;
        t = d1->count + d1->rrsig_count;
        for(i=0; i<t; i++) {
                if(d1->rr_len[i] != d2->rr_len[i] ||
                        /* no ttl check: d1->rr_ttl[i] != d2->rr_ttl[i] ||*/
                        memcmp(d1->rr_data[i], d2->rr_data[i],
                                d1->rr_len[i]) != 0)
                        return 0;
        }
        return 1;
}

/** compare rrsets and sort canonically.  Compares rrset name, type, class.
 * return 0 if equal, +1 if x > y, and -1 if x < y.
 */
static int
rrset_canonical_sort_cmp(const void* x, const void* y)
{
        struct ub_packed_rrset_key* rrx = *(struct ub_packed_rrset_key**)x;
        struct ub_packed_rrset_key* rry = *(struct ub_packed_rrset_key**)y;
        int r = dname_canonical_compare(rrx->rk.dname, rry->rk.dname);
        if(r != 0)
                return r;
        if(rrx->rk.type != rry->rk.type) {
                if(ntohs(rrx->rk.type) > ntohs(rry->rk.type))
                        return 1;
                else    return -1;
        }
        if(rrx->rk.rrset_class != rry->rk.rrset_class) {
                if(ntohs(rrx->rk.rrset_class) > ntohs(rry->rk.rrset_class))
                        return 1;
                else    return -1;
        }
        return 0;
}

int
reply_equal(struct reply_info* p, struct reply_info* q, struct regional* region)
{
        size_t i;
        struct ub_packed_rrset_key** sorted_p, **sorted_q;
        if(p->flags != q->flags ||
                p->qdcount != q->qdcount ||
                /* do not check TTL, this may differ */
                /*
                p->ttl != q->ttl ||
                p->prefetch_ttl != q->prefetch_ttl ||
                */
                p->security != q->security ||
                p->an_numrrsets != q->an_numrrsets ||
                p->ns_numrrsets != q->ns_numrrsets ||
                p->ar_numrrsets != q->ar_numrrsets ||
                p->rrset_count != q->rrset_count)
                return 0;
        /* sort the rrsets in the authority and additional sections before
         * compare, the query and answer sections are ordered in the sequence
         * they should have (eg. one after the other for aliases). */
        sorted_p = (struct ub_packed_rrset_key**)regional_alloc_init(
                region, p->rrsets, sizeof(*sorted_p)*p->rrset_count);
        if(!sorted_p) return 0;
        log_assert(p->an_numrrsets + p->ns_numrrsets + p->ar_numrrsets <=
                p->rrset_count);
        qsort(sorted_p + p->an_numrrsets, p->ns_numrrsets,
                sizeof(*sorted_p), rrset_canonical_sort_cmp);
        qsort(sorted_p + p->an_numrrsets + p->ns_numrrsets, p->ar_numrrsets,
                sizeof(*sorted_p), rrset_canonical_sort_cmp);

        sorted_q = (struct ub_packed_rrset_key**)regional_alloc_init(
                region, q->rrsets, sizeof(*sorted_q)*q->rrset_count);
        if(!sorted_q) {
                regional_free_all(region);
                return 0;
        }
        log_assert(q->an_numrrsets + q->ns_numrrsets + q->ar_numrrsets <=
                q->rrset_count);
        qsort(sorted_q + q->an_numrrsets, q->ns_numrrsets,
                sizeof(*sorted_q), rrset_canonical_sort_cmp);
        qsort(sorted_q + q->an_numrrsets + q->ns_numrrsets, q->ar_numrrsets,
                sizeof(*sorted_q), rrset_canonical_sort_cmp);

        /* compare the rrsets */
        for(i=0; i<p->rrset_count; i++) {
                if(!rrset_equal(sorted_p[i], sorted_q[i])) {
                        if(!rrset_canonical_equal(region, sorted_p[i],
                                sorted_q[i])) {
                                regional_free_all(region);
                                return 0;
                        }
                }
        }
        regional_free_all(region);
        return 1;
}

void
caps_strip_reply(struct reply_info* rep)
{
        size_t i;
        if(!rep) return;
        /* see if message is a referral, in which case the additional and
         * NS record cannot be removed */
        /* referrals have the AA flag unset (strict check, not elsewhere in
         * unbound, but for 0x20 this is very convenient). */
        if(!(rep->flags&BIT_AA))
                return;
        /* remove the additional section from the reply */
        if(rep->ar_numrrsets != 0) {
                verbose(VERB_ALGO, "caps fallback: removing additional section");
                rep->rrset_count -= rep->ar_numrrsets;
                rep->ar_numrrsets = 0;
        }
        /* is there an NS set in the authority section to remove? */
        /* the failure case (Cisco firewalls) only has one rrset in authsec */
        for(i=rep->an_numrrsets; i<rep->an_numrrsets+rep->ns_numrrsets; i++) {
                struct ub_packed_rrset_key* s = rep->rrsets[i];
                if(ntohs(s->rk.type) == LDNS_RR_TYPE_NS) {
                        /* remove NS rrset and break from loop (loop limits
                         * have changed) */
                        /* move last rrset into this position (there is no
                         * additional section any more) */
                        verbose(VERB_ALGO, "caps fallback: removing NS rrset");
                        if(i < rep->rrset_count-1)
                                rep->rrsets[i]=rep->rrsets[rep->rrset_count-1];
                        rep->rrset_count --;
                        rep->ns_numrrsets --;
                        break;
                }
        }
}

int caps_failed_rcode(struct reply_info* rep)
{
        return !(FLAGS_GET_RCODE(rep->flags) == LDNS_RCODE_NOERROR ||
                FLAGS_GET_RCODE(rep->flags) == LDNS_RCODE_NXDOMAIN);
}

void
iter_store_parentside_rrset(struct module_env* env,
        struct ub_packed_rrset_key* rrset)
{
        struct rrset_ref ref;
        rrset = packed_rrset_copy_alloc(rrset, env->alloc, *env->now);
        if(!rrset) {
                log_err("malloc failure in store_parentside_rrset");
                return;
        }
        rrset->rk.flags |= PACKED_RRSET_PARENT_SIDE;
        rrset->entry.hash = rrset_key_hash(&rrset->rk);
        ref.key = rrset;
        ref.id = rrset->id;
        /* ignore ret: if it was in the cache, ref updated */
        (void)rrset_cache_update(env->rrset_cache, &ref, env->alloc, *env->now);
}

/** fetch NS record from reply, if any */
static struct ub_packed_rrset_key*
reply_get_NS_rrset(struct reply_info* rep)
{
        size_t i;
        for(i=0; i<rep->rrset_count; i++) {
                if(rep->rrsets[i]->rk.type == htons(LDNS_RR_TYPE_NS)) {
                        return rep->rrsets[i];
                }
        }
        return NULL;
}

void
iter_store_parentside_NS(struct module_env* env, struct reply_info* rep)
{
        struct ub_packed_rrset_key* rrset = reply_get_NS_rrset(rep);
        if(rrset) {
                log_rrset_key(VERB_ALGO, "store parent-side NS", rrset);
                iter_store_parentside_rrset(env, rrset);
        }
}

void iter_store_parentside_neg(struct module_env* env,
        struct query_info* qinfo, struct reply_info* rep)
{
        /* TTL: NS from referral in iq->deleg_msg,
         *      or first RR from iq->response,
         *      or servfail5secs if !iq->response */
        time_t ttl = NORR_TTL;
        struct ub_packed_rrset_key* neg;
        struct packed_rrset_data* newd;
        if(rep) {
                struct ub_packed_rrset_key* rrset = reply_get_NS_rrset(rep);
                if(!rrset && rep->rrset_count != 0) rrset = rep->rrsets[0];
                if(rrset) ttl = ub_packed_rrset_ttl(rrset);
        }
        /* create empty rrset to store */
        neg = (struct ub_packed_rrset_key*)regional_alloc(env->scratch,
                        sizeof(struct ub_packed_rrset_key));
        if(!neg) {
                log_err("out of memory in store_parentside_neg");
                return;
        }
        memset(&neg->entry, 0, sizeof(neg->entry));
        neg->entry.key = neg;
        neg->rk.type = htons(qinfo->qtype);
        neg->rk.rrset_class = htons(qinfo->qclass);
        neg->rk.flags = 0;
        neg->rk.dname = regional_alloc_init(env->scratch, qinfo->qname,
                qinfo->qname_len);
        if(!neg->rk.dname) {
                log_err("out of memory in store_parentside_neg");
                return;
        }
        neg->rk.dname_len = qinfo->qname_len;
        neg->entry.hash = rrset_key_hash(&neg->rk);
        newd = (struct packed_rrset_data*)regional_alloc_zero(env->scratch,
                sizeof(struct packed_rrset_data) + sizeof(size_t) +
                sizeof(uint8_t*) + sizeof(time_t) + sizeof(uint16_t));
        if(!newd) {
                log_err("out of memory in store_parentside_neg");
                return;
        }
        neg->entry.data = newd;
        newd->ttl = ttl;
        /* entry must have one RR, otherwise not valid in cache.
         * put in one RR with empty rdata: those are ignored as nameserver */
        newd->count = 1;
        newd->rrsig_count = 0;
        newd->trust = rrset_trust_ans_noAA;
        newd->rr_len = (size_t*)((uint8_t*)newd +
                sizeof(struct packed_rrset_data));
        newd->rr_len[0] = 0 /* zero len rdata */ + sizeof(uint16_t);
        packed_rrset_ptr_fixup(newd);
        newd->rr_ttl[0] = newd->ttl;
        sldns_write_uint16(newd->rr_data[0], 0 /* zero len rdata */);
        /* store it */
        log_rrset_key(VERB_ALGO, "store parent-side negative", neg);
        iter_store_parentside_rrset(env, neg);
}

int
iter_lookup_parent_NS_from_cache(struct module_env* env, struct delegpt* dp,
        struct regional* region, struct query_info* qinfo)
{
        struct ub_packed_rrset_key* akey;
        akey = rrset_cache_lookup(env->rrset_cache, dp->name,
                dp->namelen, LDNS_RR_TYPE_NS, qinfo->qclass,
                PACKED_RRSET_PARENT_SIDE, *env->now, 0);
        if(akey) {
                log_rrset_key(VERB_ALGO, "found parent-side NS in cache", akey);
                dp->has_parent_side_NS = 1;
                /* and mark the new names as lame */
                if(!delegpt_rrset_add_ns(dp, region, akey, 1)) {
                        lock_rw_unlock(&akey->entry.lock);
                        return 0;
                }
                lock_rw_unlock(&akey->entry.lock);
        }
        return 1;
}

int iter_lookup_parent_glue_from_cache(struct module_env* env,
        struct delegpt* dp, struct regional* region, struct query_info* qinfo)
{
        struct ub_packed_rrset_key* akey;
        struct delegpt_ns* ns;
        size_t num = delegpt_count_targets(dp);
        for(ns = dp->nslist; ns; ns = ns->next) {
                if(ns->cache_lookup_count > ITERATOR_NAME_CACHELOOKUP_MAX_PSIDE)
                        continue;
                ns->cache_lookup_count++;
                /* get cached parentside A */
                akey = rrset_cache_lookup(env->rrset_cache, ns->name,
                        ns->namelen, LDNS_RR_TYPE_A, qinfo->qclass,
                        PACKED_RRSET_PARENT_SIDE, *env->now, 0);
                if(akey) {
                        log_rrset_key(VERB_ALGO, "found parent-side", akey);
                        ns->done_pside4 = 1;
                        /* a negative-cache-element has no addresses it adds */
                        if(!delegpt_add_rrset_A(dp, region, akey, 1, NULL))
                                log_err("malloc failure in lookup_parent_glue");
                        lock_rw_unlock(&akey->entry.lock);
                }
                /* get cached parentside AAAA */
                akey = rrset_cache_lookup(env->rrset_cache, ns->name,
                        ns->namelen, LDNS_RR_TYPE_AAAA, qinfo->qclass,
                        PACKED_RRSET_PARENT_SIDE, *env->now, 0);
                if(akey) {
                        log_rrset_key(VERB_ALGO, "found parent-side", akey);
                        ns->done_pside6 = 1;
                        /* a negative-cache-element has no addresses it adds */
                        if(!delegpt_add_rrset_AAAA(dp, region, akey, 1, NULL))
                                log_err("malloc failure in lookup_parent_glue");
                        lock_rw_unlock(&akey->entry.lock);
                }
        }
        /* see if new (but lame) addresses have become available */
        return delegpt_count_targets(dp) != num;
}

int
iter_get_next_root(struct iter_hints* hints, struct iter_forwards* fwd,
        uint16_t* c)
{
        uint16_t c1 = *c, c2 = *c;
        int r1, r2;
        int nolock = 1;

        /* prelock both forwards and hints for atomic read. */
        lock_rw_rdlock(&fwd->lock);
        lock_rw_rdlock(&hints->lock);
        r1 = hints_next_root(hints, &c1, nolock);
        r2 = forwards_next_root(fwd, &c2, nolock);
        lock_rw_unlock(&fwd->lock);
        lock_rw_unlock(&hints->lock);

        if(!r1 && !r2) /* got none, end of list */
                return 0;
        else if(!r1) /* got one, return that */
                *c = c2;
        else if(!r2)
                *c = c1;
        else if(c1 < c2) /* got both take smallest */
                *c = c1;
        else    *c = c2;
        return 1;
}

void
iter_scrub_ds(struct dns_msg* msg, struct ub_packed_rrset_key* ns, uint8_t* z)
{
        /* Only the DS record for the delegation itself is expected.
         * We allow DS for everything between the bailiwick and the
         * zonecut, thus DS records must be at or above the zonecut.
         * And the DS records must be below the server authority zone.
         * The answer section is already scrubbed. */
        size_t i = msg->rep->an_numrrsets;
        while(i < (msg->rep->an_numrrsets + msg->rep->ns_numrrsets)) {
                struct ub_packed_rrset_key* s = msg->rep->rrsets[i];
                if(ntohs(s->rk.type) == LDNS_RR_TYPE_DS &&
                        (!ns || !dname_subdomain_c(ns->rk.dname, s->rk.dname)
                        || query_dname_compare(z, s->rk.dname) == 0)) {
                        log_nametypeclass(VERB_ALGO, "removing irrelevant DS",
                                s->rk.dname, ntohs(s->rk.type),
                                ntohs(s->rk.rrset_class));
                        memmove(msg->rep->rrsets+i, msg->rep->rrsets+i+1,
                                sizeof(struct ub_packed_rrset_key*) *
                                (msg->rep->rrset_count-i-1));
                        msg->rep->ns_numrrsets--;
                        msg->rep->rrset_count--;
                        /* stay at same i, but new record */
                        continue;
                }
                i++;
        }
}

void
iter_scrub_nxdomain(struct dns_msg* msg)
{
        if(msg->rep->an_numrrsets == 0)
                return;

        memmove(msg->rep->rrsets, msg->rep->rrsets+msg->rep->an_numrrsets,
                sizeof(struct ub_packed_rrset_key*) *
                (msg->rep->rrset_count-msg->rep->an_numrrsets));
        msg->rep->rrset_count -= msg->rep->an_numrrsets;
        msg->rep->an_numrrsets = 0;
}

void iter_dec_attempts(struct delegpt* dp, int d, int outbound_msg_retry)
{
        struct delegpt_addr* a;
        for(a=dp->target_list; a; a = a->next_target) {
                if(a->attempts >= outbound_msg_retry) {
                        /* add back to result list */
                        delegpt_add_to_result_list(dp, a);
                }
                if(a->attempts > d)
                        a->attempts -= d;
                else a->attempts = 0;
        }
}

void iter_merge_retry_counts(struct delegpt* dp, struct delegpt* old,
        int outbound_msg_retry)
{
        struct delegpt_addr* a, *o, *prev;
        for(a=dp->target_list; a; a = a->next_target) {
                o = delegpt_find_addr(old, &a->addr, a->addrlen);
                if(o) {
                        log_addr(VERB_ALGO, "copy attempt count previous dp",
                                &a->addr, a->addrlen);
                        a->attempts = o->attempts;
                }
        }
        prev = NULL;
        a = dp->usable_list;
        while(a) {
                if(a->attempts >= outbound_msg_retry) {
                        log_addr(VERB_ALGO, "remove from usable list dp",
                                &a->addr, a->addrlen);
                        /* remove from result list */
                        if(prev)
                                prev->next_usable = a->next_usable;
                        else    dp->usable_list = a->next_usable;
                        /* prev stays the same */
                        a = a->next_usable;
                        continue;
                }
                prev = a;
                a = a->next_usable;
        }
}

int
iter_ds_toolow(struct dns_msg* msg, struct delegpt* dp)
{
        /* if for query example.com, there is example.com SOA or a subdomain
         * of example.com, then we are too low and need to fetch NS. */
        size_t i;
        /* if we have a DNAME or CNAME we are probably wrong */
        /* if we have a qtype DS in the answer section, its fine */
        for(i=0; i < msg->rep->an_numrrsets; i++) {
                struct ub_packed_rrset_key* s = msg->rep->rrsets[i];
                if(ntohs(s->rk.type) == LDNS_RR_TYPE_DNAME ||
                        ntohs(s->rk.type) == LDNS_RR_TYPE_CNAME) {
                        /* not the right answer, maybe too low, check the
                         * RRSIG signer name (if there is any) for a hint
                         * that it is from the dp zone anyway */
                        uint8_t* sname;
                        size_t slen;
                        val_find_rrset_signer(s, &sname, &slen);
                        if(sname && query_dname_compare(dp->name, sname)==0)
                                return 0; /* it is fine, from the right dp */
                        return 1;
                }
                if(ntohs(s->rk.type) == LDNS_RR_TYPE_DS)
                        return 0; /* fine, we have a DS record */
        }
        for(i=msg->rep->an_numrrsets;
                i < msg->rep->an_numrrsets + msg->rep->ns_numrrsets; i++) {
                struct ub_packed_rrset_key* s = msg->rep->rrsets[i];
                if(ntohs(s->rk.type) == LDNS_RR_TYPE_SOA) {
                        if(dname_subdomain_c(s->rk.dname, msg->qinfo.qname))
                                return 1; /* point is too low */
                        if(query_dname_compare(s->rk.dname, dp->name)==0)
                                return 0; /* right dp */
                }
                if(ntohs(s->rk.type) == LDNS_RR_TYPE_NSEC ||
                        ntohs(s->rk.type) == LDNS_RR_TYPE_NSEC3) {
                        uint8_t* sname;
                        size_t slen;
                        val_find_rrset_signer(s, &sname, &slen);
                        if(sname && query_dname_compare(dp->name, sname)==0)
                                return 0; /* it is fine, from the right dp */
                        return 1;
                }
        }
        /* we do not know */
        return 1;
}

int iter_dp_cangodown(struct query_info* qinfo, struct delegpt* dp)
{
        /* no delegation point, do not see how we can go down,
         * robust check, it should really exist */
        if(!dp) return 0;

        /* see if dp equals the qname, then we cannot go down further */
        if(query_dname_compare(qinfo->qname, dp->name) == 0)
                return 0;
        /* if dp is one label above the name we also cannot go down further */
        if(dname_count_labels(qinfo->qname) == dp->namelabs+1)
                return 0;
        return 1;
}

int
iter_stub_fwd_no_cache(struct module_qstate *qstate, struct query_info *qinf,
        uint8_t** retdpname, size_t* retdpnamelen, uint8_t* dpname_storage,
        size_t dpname_storage_len)
{
        struct iter_hints_stub *stub;
        struct delegpt *dp;
        int nolock = 1;

        /* Check for stub. */
        /* Lock both forwards and hints for atomic read. */
        lock_rw_rdlock(&qstate->env->fwds->lock);
        lock_rw_rdlock(&qstate->env->hints->lock);
        stub = hints_lookup_stub(qstate->env->hints, qinf->qname,
            qinf->qclass, NULL, nolock);
        dp = forwards_lookup(qstate->env->fwds, qinf->qname, qinf->qclass,
                nolock);

        /* see if forward or stub is more pertinent */
        if(stub && stub->dp && dp) {
                if(dname_strict_subdomain(dp->name, dp->namelabs,
                        stub->dp->name, stub->dp->namelabs)) {
                        stub = NULL; /* ignore stub, forward is lower */
                } else {
                        dp = NULL; /* ignore forward, stub is lower */
                }
        }

        /* check stub */
        if (stub != NULL && stub->dp != NULL) {
                enum verbosity_value level = VERB_ALGO;
                int stub_no_cache = stub->dp->no_cache;
                lock_rw_unlock(&qstate->env->fwds->lock);
                if(verbosity >= level && stub_no_cache) {
                        char qname[LDNS_MAX_DOMAINLEN];
                        char dpname[LDNS_MAX_DOMAINLEN];
                        dname_str(qinf->qname, qname);
                        dname_str(stub->dp->name, dpname);
                        verbose(level, "stub for %s %s has no_cache", qname, dpname);
                }
                if(retdpname) {
                        if(stub->dp->namelen > dpname_storage_len) {
                                verbose(VERB_ALGO, "no cache stub dpname too long");
                                lock_rw_unlock(&qstate->env->hints->lock);
                                *retdpname = NULL;
                                *retdpnamelen = 0;
                                return stub_no_cache;
                        }
                        memmove(dpname_storage, stub->dp->name,
                                stub->dp->namelen);
                        *retdpname = dpname_storage;
                        *retdpnamelen = stub->dp->namelen;
                }
                lock_rw_unlock(&qstate->env->hints->lock);
                return stub_no_cache;
        }

        /* Check for forward. */
        if (dp) {
                enum verbosity_value level = VERB_ALGO;
                int dp_no_cache = dp->no_cache;
                lock_rw_unlock(&qstate->env->hints->lock);
                if(verbosity >= level && dp_no_cache) {
                        char qname[LDNS_MAX_DOMAINLEN];
                        char dpname[LDNS_MAX_DOMAINLEN];
                        dname_str(qinf->qname, qname);
                        dname_str(dp->name, dpname);
                        verbose(level, "forward for %s %s has no_cache", qname, dpname);
                }
                if(retdpname) {
                        if(dp->namelen > dpname_storage_len) {
                                verbose(VERB_ALGO, "no cache dpname too long");
                                lock_rw_unlock(&qstate->env->fwds->lock);
                                *retdpname = NULL;
                                *retdpnamelen = 0;
                                return dp_no_cache;
                        }
                        memmove(dpname_storage, dp->name, dp->namelen);
                        *retdpname = dpname_storage;
                        *retdpnamelen = dp->namelen;
                }
                lock_rw_unlock(&qstate->env->fwds->lock);
                return dp_no_cache;
        }
        lock_rw_unlock(&qstate->env->fwds->lock);
        lock_rw_unlock(&qstate->env->hints->lock);
        if(retdpname) {
                *retdpname = NULL;
                *retdpnamelen = 0;
        }
        return 0;
}

void iterator_set_ip46_support(struct module_stack* mods,
        struct module_env* env, struct outside_network* outnet)
{
        int m = modstack_find(mods, "iterator");
        struct iter_env* ie = NULL;
        if(m == -1)
                return;
        ie = (struct iter_env*)env->modinfo[m];
        if(outnet->pending == NULL)
                return; /* we are in testbound, no rbtree for UDP */
        if(outnet->num_ip4 == 0)
                ie->supports_ipv4 = 0;
        if(outnet->num_ip6 == 0)
                ie->supports_ipv6 = 0;
}

void
limit_nsec_ttl(struct dns_msg* msg)
{
        /* Limit NSEC and NSEC3 TTL in response, RFC9077 */
        size_t i;
        int found = 0;
        time_t soa_ttl = 0;
        /* Limit the NSEC and NSEC3 TTL values to the SOA TTL and SOA minimum
         * TTL. That has already been applied to the SOA record ttl. */
        for(i=0; i<msg->rep->rrset_count; i++) {
                struct ub_packed_rrset_key* s = msg->rep->rrsets[i];
                if(ntohs(s->rk.type) == LDNS_RR_TYPE_SOA) {
                        struct packed_rrset_data* soadata = (struct packed_rrset_data*)s->entry.data;
                        found = 1;
                        soa_ttl = soadata->ttl;
                        break;
                }
        }
        if(!found)
                return;
        for(i=0; i<msg->rep->rrset_count; i++) {
                struct ub_packed_rrset_key* s = msg->rep->rrsets[i];
                if(ntohs(s->rk.type) == LDNS_RR_TYPE_NSEC ||
                        ntohs(s->rk.type) == LDNS_RR_TYPE_NSEC3) {
                        struct packed_rrset_data* data = (struct packed_rrset_data*)s->entry.data;
                        /* Limit the negative TTL. */
                        if(data->ttl > soa_ttl) {
                                if(verbosity >= VERB_ALGO) {
                                        char buf[256];
                                        snprintf(buf, sizeof(buf),
                                                "limiting TTL %d of %s record to the SOA TTL of %d for",
                                                (int)data->ttl, ((ntohs(s->rk.type) == LDNS_RR_TYPE_NSEC)?"NSEC":"NSEC3"), (int)soa_ttl);
                                        log_nametypeclass(VERB_ALGO, buf,
                                                s->rk.dname, ntohs(s->rk.type),
                                                ntohs(s->rk.rrset_class));
                                }
                                data->ttl = soa_ttl;
                        }
                }
        }
}

void
iter_make_minimal(struct reply_info* rep)
{
        size_t rem = rep->ns_numrrsets + rep->ar_numrrsets;
        rep->ns_numrrsets = 0;
        rep->ar_numrrsets = 0;
        rep->rrset_count -= rem;
}