mDNSResponder/mDNSCore/mDNS.c

/* -*- Mode: C; tab-width: 4; c-file-style: "bsd"; c-basic-offset: 4; fill-column: 108; indent-tabs-mode: nil; -*-
 *
 * Copyright (c) 2002-2020 Apple Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * This code is completely 100% portable C. It does not depend on any external header files
 * from outside the mDNS project -- all the types it expects to find are defined right here.
 *
 * The previous point is very important: This file does not depend on any external
 * header files. It should compile on *any* platform that has a C compiler, without
 * making *any* assumptions about availability of so-called "standard" C functions,
 * routines, or types (which may or may not be present on any given platform).
 */

#include "DNSCommon.h"                  // Defines general DNS utility routines
#include "uDNS.h"                       // Defines entry points into unicast-specific routines

#if MDNSRESPONDER_SUPPORTS(APPLE, D2D)
#include "D2D.h"
#endif

#if MDNSRESPONDER_SUPPORTS(APPLE, AUDIT_TOKEN)
#include <bsm/libbsm.h>
#endif

#if MDNSRESPONDER_SUPPORTS(APPLE, CACHE_ANALYTICS)
#include "dnssd_analytics.h"
#endif

#if MDNSRESPONDER_SUPPORTS(APPLE, QUERIER)
#include "QuerierSupport.h"
#endif

// Disable certain benign warnings with Microsoft compilers
#if (defined(_MSC_VER))
// Disable "conditional expression is constant" warning for debug macros.
// Otherwise, this generates warnings for the perfectly natural construct "while(1)"
// If someone knows a variant way of writing "while(1)" that doesn't generate warning messages, please let us know
    #pragma warning(disable:4127)

// Disable "assignment within conditional expression".
// Other compilers understand the convention that if you place the assignment expression within an extra pair
// of parentheses, this signals to the compiler that you really intended an assignment and no warning is necessary.
// The Microsoft compiler doesn't understand this convention, so in the absense of any other way to signal
// to the compiler that the assignment is intentional, we have to just turn this warning off completely.
    #pragma warning(disable:4706)
#endif

#include "dns_sd.h" // for kDNSServiceFlags* definitions
#include "dns_sd_internal.h"

#if APPLE_OSX_mDNSResponder
// Delay in seconds before disabling multicast after there are no active queries or registrations.
#define BONJOUR_DISABLE_DELAY 60
#endif

#if MDNSRESPONDER_SUPPORTS(APPLE, WEB_CONTENT_FILTER)
#include <WebFilterDNS/WebFilterDNS.h>

WCFConnection *WCFConnectionNew(void) __attribute__((weak_import));
void WCFConnectionDealloc(WCFConnection* c) __attribute__((weak_import));
#endif

#if MDNSRESPONDER_SUPPORTS(APPLE, METRICS)
#include "Metrics.h"
#endif

#if MDNSRESPONDER_SUPPORTS(APPLE, DNS64)
#include "DNS64.h"
#endif

#if MDNSRESPONDER_SUPPORTS(APPLE, DNSSECv2)
#include "dnssec_v2.h"
#endif // MDNSRESPONDER_SUPPORTS(APPLE, DNSSECv2)

// Forward declarations
mDNSlocal void BeginSleepProcessing(mDNS *const m);
mDNSlocal void RetrySPSRegistrations(mDNS *const m);
mDNSlocal void SendWakeup(mDNS *const m, mDNSInterfaceID InterfaceID, mDNSEthAddr *EthAddr, mDNSOpaque48 *password, mDNSBool unicastOnly);
#if !MDNSRESPONDER_SUPPORTS(APPLE, QUERIER)
mDNSlocal mDNSBool LocalRecordRmvEventsForQuestion(mDNS *const m, DNSQuestion *q);
#endif
mDNSlocal void mDNS_PurgeBeforeResolve(mDNS *const m, DNSQuestion *q);
mDNSlocal void mDNS_SendKeepalives(mDNS *const m);
mDNSlocal void mDNS_ExtractKeepaliveInfo(AuthRecord *ar, mDNSu32 *timeout, mDNSAddr *laddr, mDNSAddr *raddr, mDNSEthAddr *eth,
                                         mDNSu32 *seq, mDNSu32 *ack, mDNSIPPort *lport, mDNSIPPort *rport, mDNSu16 *win);

typedef mDNSu32 DeadvertiseFlags;
#define kDeadvertiseFlag_NormalHostname (1U << 0)
#define kDeadvertiseFlag_RandHostname   (1U << 1)
#define kDeadvertiseFlag_All            (kDeadvertiseFlag_NormalHostname | kDeadvertiseFlag_RandHostname)

mDNSlocal void DeadvertiseInterface(mDNS *const m, NetworkInterfaceInfo *set, DeadvertiseFlags flags);
mDNSlocal void AdvertiseInterfaceIfNeeded(mDNS *const m, NetworkInterfaceInfo *set);
mDNSlocal mDNSu8 *GetValueForMACAddr(mDNSu8 *ptr, mDNSu8 *limit, mDNSEthAddr *eth);

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark - Program Constants
#endif

// To Turn OFF mDNS_Tracer set MDNS_TRACER to 0 or undef it
#define MDNS_TRACER 1

// Any records bigger than this are considered 'large' records
#define SmallRecordLimit 1024

#define kMaxUpdateCredits 10
#define kUpdateCreditRefreshInterval (mDNSPlatformOneSecond * 6)

// define special NR_AnswerTo values
#define NR_AnswerMulticast  (mDNSu8*)~0
#define NR_AnswerUnicast    (mDNSu8*)~1

// Question default timeout values
#define DEFAULT_MCAST_TIMEOUT       5
#define DEFAULT_LO_OR_P2P_TIMEOUT   5

// The code (see SendQueries() and BuildQuestion()) needs to have the
// RequestUnicast value set to a value one greater than the number of times you want the query
// sent with the "request unicast response" (QU) bit set.
#define SET_QU_IN_FIRST_QUERY   2
#define kDefaultRequestUnicastCount SET_QU_IN_FIRST_QUERY

// The time needed to offload records to a sleep proxy after powerd sends the kIOMessageSystemWillSleep notification
#define DARK_WAKE_DELAY_SLEEP  5
#define kDarkWakeDelaySleep    (mDNSPlatformOneSecond * DARK_WAKE_DELAY_SLEEP)

// The maximum number of times we delay probing to prevent spurious conflicts due to stale packets
#define MAX_CONFLICT_PROCESSING_DELAYS 3

// RFC 6762 defines Passive Observation Of Failures (POOF)
//
//    A host observes the multicast queries issued by the other hosts on
//    the network.  One of the major benefits of also sending responses
//    using multicast is that it allows all hosts to see the responses
//    (or lack thereof) to those queries.
//
//    If a host sees queries, for which a record in its cache would be
//    expected to be given as an answer in a multicast response, but no
//    such answer is seen, then the host may take this as an indication
//    that the record may no longer be valid.
//
//    After seeing two or more of these queries, and seeing no multicast
//    response containing the expected answer within ten seconds, then even
//    though its TTL may indicate that it is not yet due to expire, that
//    record SHOULD be flushed from the cache.
//
// <https://tools.ietf.org/html/rfc6762#section-10.5>

#define POOF_ENABLED 1

mDNSexport const char *const mDNS_DomainTypeNames[] =
{
    "b._dns-sd._udp.",      // Browse
    "db._dns-sd._udp.",     // Default Browse
    "lb._dns-sd._udp.",     // Automatic Browse
    "r._dns-sd._udp.",      // Registration
    "dr._dns-sd._udp."      // Default Registration
};

#ifdef UNICAST_DISABLED
#define uDNS_IsActiveQuery(q, u) mDNSfalse
#endif

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark -
#pragma mark - General Utility Functions
#endif

#if MDNS_MALLOC_DEBUGGING
// When doing memory allocation debugging, this function traverses all lists in the mDNS query
// structures and caches and checks each entry in the list to make sure it's still good.
mDNSlocal void mDNS_ValidateLists(void *context)
{
    mDNS *m = context;
#if MDNSRESPONDER_SUPPORTS(APPLE, BONJOUR_ON_DEMAND)
    mDNSu32 NumAllInterfaceRecords   = 0;
    mDNSu32 NumAllInterfaceQuestions = 0;
#endif

    // Check core mDNS lists
    AuthRecord                  *rr;
    for (rr = m->ResourceRecords; rr; rr=rr->next)
    {
        if (rr->next == (AuthRecord *)~0 || rr->resrec.RecordType == 0 || rr->resrec.RecordType == 0xFF)
            LogMemCorruption("ResourceRecords list: %p is garbage (%X)", rr, rr->resrec.RecordType);
        if (rr->resrec.name != &rr->namestorage)
            LogMemCorruption("ResourceRecords list: %p name %p does not point to namestorage %p %##s",
                             rr, rr->resrec.name->c, rr->namestorage.c, rr->namestorage.c);
#if MDNSRESPONDER_SUPPORTS(APPLE, BONJOUR_ON_DEMAND)
        if (!AuthRecord_uDNS(rr) && !RRLocalOnly(rr)) NumAllInterfaceRecords++;
#endif
    }

    for (rr = m->DuplicateRecords; rr; rr=rr->next)
    {
        if (rr->next == (AuthRecord *)~0 || rr->resrec.RecordType == 0 || rr->resrec.RecordType == 0xFF)
            LogMemCorruption("DuplicateRecords list: %p is garbage (%X)", rr, rr->resrec.RecordType);
#if MDNSRESPONDER_SUPPORTS(APPLE, BONJOUR_ON_DEMAND)
        if (!AuthRecord_uDNS(rr) && !RRLocalOnly(rr)) NumAllInterfaceRecords++;
#endif
    }

    rr = m->NewLocalRecords;
    if (rr)
        if (rr->next == (AuthRecord *)~0 || rr->resrec.RecordType == 0 || rr->resrec.RecordType == 0xFF)
            LogMemCorruption("NewLocalRecords: %p is garbage (%X)", rr, rr->resrec.RecordType);

    rr = m->CurrentRecord;
    if (rr)
        if (rr->next == (AuthRecord *)~0 || rr->resrec.RecordType == 0 || rr->resrec.RecordType == 0xFF)
            LogMemCorruption("CurrentRecord: %p is garbage (%X)", rr, rr->resrec.RecordType);

    DNSQuestion                 *q;
    for (q = m->Questions; q; q=q->next)
    {
        if (q->next == (DNSQuestion*)~0 || q->ThisQInterval == (mDNSs32) ~0)
            LogMemCorruption("Questions list: %p is garbage (%lX %p)", q, q->ThisQInterval, q->next);
        if (q->DuplicateOf && q->LocalSocket)
            LogMemCorruption("Questions list: Duplicate Question %p should not have LocalSocket set %##s (%s)", q, q->qname.c, DNSTypeName(q->qtype));
#if MDNSRESPONDER_SUPPORTS(APPLE, BONJOUR_ON_DEMAND)
        if (!LocalOnlyOrP2PInterface(q->InterfaceID) && mDNSOpaque16IsZero(q->TargetQID))
            NumAllInterfaceQuestions++;
#endif
    }

    CacheGroup                  *cg;
    CacheRecord                 *cr;
    mDNSu32 slot;
    FORALL_CACHERECORDS(slot, cg, cr)
    {
        if (cr->resrec.RecordType == 0 || cr->resrec.RecordType == 0xFF)
            LogMemCorruption("Cache slot %lu: %p is garbage (%X)", slot, cr, cr->resrec.RecordType);
        if (cr->CRActiveQuestion)
        {
            for (q = m->Questions; q; q=q->next) if (q == cr->CRActiveQuestion) break;
            if (!q) LogMemCorruption("Cache slot %lu: CRActiveQuestion %p not in m->Questions list %s", slot, cr->CRActiveQuestion, CRDisplayString(m, cr));
        }
    }

#if MDNSRESPONDER_SUPPORTS(APPLE, BONJOUR_ON_DEMAND)
    if (m->NumAllInterfaceRecords != NumAllInterfaceRecords)
    	LogMemCorruption("NumAllInterfaceRecords is %d should be %d", m->NumAllInterfaceRecords, NumAllInterfaceRecords);

    if (m->NumAllInterfaceQuestions != NumAllInterfaceQuestions)
    	LogMemCorruption("NumAllInterfaceQuestions is %d should be %d", m->NumAllInterfaceQuestions, NumAllInterfaceQuestions);
#endif // MDNSRESPONDER_SUPPORTS(APPLE, BONJOUR_ON_DEMAND)
}
#endif // MDNS_MALLOC_DEBUGGING

// Returns true if this is a  unique, authoritative LocalOnly record that answers questions of type
// A, AAAA , CNAME, or PTR.  The caller should answer the question with this record and not send out
// the question on the wire if LocalOnlyRecordAnswersQuestion() also returns true.
// Main use is to handle /etc/hosts records and the LocalOnly PTR records created for localhost.
#define UniqueLocalOnlyRecord(rr) ((rr)->ARType == AuthRecordLocalOnly && \
                                        (rr)->resrec.RecordType & kDNSRecordTypeUniqueMask && \
                                        ((rr)->resrec.rrtype == kDNSType_A || (rr)->resrec.rrtype == kDNSType_AAAA || \
                                         (rr)->resrec.rrtype == kDNSType_CNAME || \
                                         (rr)->resrec.rrtype == kDNSType_PTR))

mDNSlocal void SetNextQueryStopTime(mDNS *const m, const DNSQuestion *const q)
{
    mDNS_CheckLock(m);

    if (m->NextScheduledStopTime - q->StopTime > 0)
        m->NextScheduledStopTime = q->StopTime;
}

mDNSexport void SetNextQueryTime(mDNS *const m, const DNSQuestion *const q)
{
    mDNS_CheckLock(m);

    if (ActiveQuestion(q))
    {
        // Depending on whether this is a multicast or unicast question we want to set either:
        // m->NextScheduledQuery = NextQSendTime(q) or
        // m->NextuDNSEvent      = NextQSendTime(q)
        mDNSs32 *const timer = mDNSOpaque16IsZero(q->TargetQID) ? &m->NextScheduledQuery : &m->NextuDNSEvent;
        if (*timer - NextQSendTime(q) > 0)
            *timer = NextQSendTime(q);
    }
}

mDNSlocal void ReleaseAuthEntity(AuthHash *r, AuthEntity *e)
{
#if MDNS_MALLOC_DEBUGGING >= 1
    unsigned int i;
    for (i=0; i<sizeof(*e); i++) ((char*)e)[i] = 0xFF;
#endif
    e->next = r->rrauth_free;
    r->rrauth_free = e;
    r->rrauth_totalused--;
}

mDNSlocal void ReleaseAuthGroup(AuthHash *r, AuthGroup **cp)
{
    AuthEntity *e = (AuthEntity *)(*cp);
    LogMsg("ReleaseAuthGroup:  Releasing AuthGroup %##s", (*cp)->name->c);
    if ((*cp)->rrauth_tail != &(*cp)->members)
        LogMsg("ERROR: (*cp)->members == mDNSNULL but (*cp)->rrauth_tail != &(*cp)->members)");
    if ((*cp)->name != (domainname*)((*cp)->namestorage)) mDNSPlatformMemFree((*cp)->name);
    (*cp)->name = mDNSNULL;
    *cp = (*cp)->next;          // Cut record from list
    ReleaseAuthEntity(r, e);
}

mDNSlocal AuthEntity *GetAuthEntity(AuthHash *r, const AuthGroup *const PreserveAG)
{
    AuthEntity *e = mDNSNULL;

    if (r->rrauth_lock) { LogMsg("GetFreeCacheRR ERROR! Cache already locked!"); return(mDNSNULL); }
    r->rrauth_lock = 1;

    if (!r->rrauth_free)
    {
        // We allocate just one AuthEntity at a time because we need to be able
        // free them all individually which normally happens when we parse /etc/hosts into
        // AuthHash where we add the "new" entries and discard (free) the already added
        // entries. If we allocate as chunks, we can't free them individually.
        AuthEntity *storage = (AuthEntity *) mDNSPlatformMemAllocateClear(sizeof(*storage));
        storage->next = mDNSNULL;
        r->rrauth_free = storage;
    }

    // If we still have no free records, recycle all the records we can.
    // Enumerating the entire auth is moderately expensive, so when we do it, we reclaim all the records we can in one pass.
    if (!r->rrauth_free)
    {
        mDNSu32 oldtotalused = r->rrauth_totalused;
        mDNSu32 slot;
        for (slot = 0; slot < AUTH_HASH_SLOTS; slot++)
        {
            AuthGroup **cp = &r->rrauth_hash[slot];
            while (*cp)
            {
                if ((*cp)->members || (*cp)==PreserveAG) cp=&(*cp)->next;
                else ReleaseAuthGroup(r, cp);
            }
        }
        LogInfo("GetAuthEntity: Recycled %d records to reduce auth cache from %d to %d",
                oldtotalused - r->rrauth_totalused, oldtotalused, r->rrauth_totalused);
    }

    if (r->rrauth_free) // If there are records in the free list, take one
    {
        e = r->rrauth_free;
        r->rrauth_free = e->next;
        if (++r->rrauth_totalused >= r->rrauth_report)
        {
            LogInfo("RR Auth now using %ld objects", r->rrauth_totalused);
            if      (r->rrauth_report <  100) r->rrauth_report += 10;
            else if (r->rrauth_report < 1000) r->rrauth_report += 100;
            else r->rrauth_report += 1000;
        }
        mDNSPlatformMemZero(e, sizeof(*e));
    }

    r->rrauth_lock = 0;

    return(e);
}

mDNSexport AuthGroup *AuthGroupForName(AuthHash *r, const mDNSu32 namehash, const domainname *const name)
{
    AuthGroup *ag;
    const mDNSu32 slot = namehash % AUTH_HASH_SLOTS;

    for (ag = r->rrauth_hash[slot]; ag; ag=ag->next)
        if (ag->namehash == namehash && SameDomainName(ag->name, name))
            break;
    return(ag);
}

mDNSexport AuthGroup *AuthGroupForRecord(AuthHash *r, const ResourceRecord *const rr)
{
    return(AuthGroupForName(r, rr->namehash, rr->name));
}

mDNSlocal AuthGroup *GetAuthGroup(AuthHash *r, const ResourceRecord *const rr)
{
    mDNSu16 namelen = DomainNameLength(rr->name);
    AuthGroup *ag = (AuthGroup*)GetAuthEntity(r, mDNSNULL);
    const mDNSu32 slot = rr->namehash % AUTH_HASH_SLOTS;
    if (!ag) { LogMsg("GetAuthGroup: Failed to allocate memory for %##s", rr->name->c); return(mDNSNULL); }
    ag->next         = r->rrauth_hash[slot];
    ag->namehash     = rr->namehash;
    ag->members      = mDNSNULL;
    ag->rrauth_tail  = &ag->members;
    ag->NewLocalOnlyRecords = mDNSNULL;
    if (namelen > sizeof(ag->namestorage))
        ag->name = (domainname *) mDNSPlatformMemAllocate(namelen);
    else
        ag->name = (domainname*)ag->namestorage;
    if (!ag->name)
    {
        LogMsg("GetAuthGroup: Failed to allocate name storage for %##s", rr->name->c);
        ReleaseAuthEntity(r, (AuthEntity*)ag);
        return(mDNSNULL);
    }
    AssignDomainName(ag->name, rr->name);

    if (AuthGroupForRecord(r, rr)) LogMsg("GetAuthGroup: Already have AuthGroup for %##s", rr->name->c);
    r->rrauth_hash[slot] = ag;
    if (AuthGroupForRecord(r, rr) != ag) LogMsg("GetAuthGroup: Not finding AuthGroup for %##s", rr->name->c);

    return(ag);
}

// Returns the AuthGroup in which the AuthRecord was inserted
mDNSexport AuthGroup *InsertAuthRecord(mDNS *const m, AuthHash *r, AuthRecord *rr)
{
    AuthGroup *ag;

    (void)m;
    ag = AuthGroupForRecord(r, &rr->resrec);
    if (!ag) ag = GetAuthGroup(r, &rr->resrec);   // If we don't have a AuthGroup for this name, make one now
    if (ag)
    {
        *(ag->rrauth_tail) = rr;                // Append this record to tail of cache slot list
        ag->rrauth_tail = &(rr->next);          // Advance tail pointer
    }
    return ag;
}

mDNSexport AuthGroup *RemoveAuthRecord(mDNS *const m, AuthHash *r, AuthRecord *rr)
{
    AuthGroup *a;
    AuthRecord **rp;

    a = AuthGroupForRecord(r, &rr->resrec);
    if (!a) { LogMsg("RemoveAuthRecord: ERROR!! AuthGroup not found for %s", ARDisplayString(m, rr)); return mDNSNULL; }
    rp = &a->members;
    while (*rp)
    {
        if (*rp != rr)
            rp=&(*rp)->next;
        else
        {
            // We don't break here, so that we can set the tail below without tracking "prev" pointers

            LogInfo("RemoveAuthRecord: removing auth record %s from table", ARDisplayString(m, rr));
            *rp = (*rp)->next;          // Cut record from list
        }
    }
    // TBD: If there are no more members, release authgroup ?
    a->rrauth_tail = rp;
    return a;
}

mDNSexport CacheGroup *CacheGroupForName(const mDNS *const m, const mDNSu32 namehash, const domainname *const name)
{
    CacheGroup *cg;
    mDNSu32    slot = HashSlotFromNameHash(namehash);
    for (cg = m->rrcache_hash[slot]; cg; cg=cg->next)
        if (cg->namehash == namehash && SameDomainName(cg->name, name))
            break;
    return(cg);
}

mDNSlocal CacheGroup *CacheGroupForRecord(const mDNS *const m, const ResourceRecord *const rr)
{
    return(CacheGroupForName(m, rr->namehash, rr->name));
}

mDNSexport mDNSBool mDNS_AddressIsLocalSubnet(mDNS *const m, const mDNSInterfaceID InterfaceID, const mDNSAddr *addr)
{
    NetworkInterfaceInfo *intf;

    if (addr->type == mDNSAddrType_IPv4)
    {
        // Normally we resist touching the NotAnInteger fields, but here we're doing tricky bitwise masking so we make an exception
        if (mDNSv4AddressIsLinkLocal(&addr->ip.v4)) return(mDNStrue);
        for (intf = m->HostInterfaces; intf; intf = intf->next)
            if (intf->ip.type == addr->type && intf->InterfaceID == InterfaceID && intf->McastTxRx)
                if (((intf->ip.ip.v4.NotAnInteger ^ addr->ip.v4.NotAnInteger) & intf->mask.ip.v4.NotAnInteger) == 0)
                    return(mDNStrue);
    }

    if (addr->type == mDNSAddrType_IPv6)
    {
        if (mDNSv6AddressIsLinkLocal(&addr->ip.v6)) return(mDNStrue);
        for (intf = m->HostInterfaces; intf; intf = intf->next)
            if (intf->ip.type == addr->type && intf->InterfaceID == InterfaceID && intf->McastTxRx)
                if ((((intf->ip.ip.v6.l[0] ^ addr->ip.v6.l[0]) & intf->mask.ip.v6.l[0]) == 0) &&
                    (((intf->ip.ip.v6.l[1] ^ addr->ip.v6.l[1]) & intf->mask.ip.v6.l[1]) == 0) &&
                    (((intf->ip.ip.v6.l[2] ^ addr->ip.v6.l[2]) & intf->mask.ip.v6.l[2]) == 0) &&
                    (((intf->ip.ip.v6.l[3] ^ addr->ip.v6.l[3]) & intf->mask.ip.v6.l[3]) == 0))
                        return(mDNStrue);
    }

    return(mDNSfalse);
}

mDNSlocal NetworkInterfaceInfo *FirstInterfaceForID(mDNS *const m, const mDNSInterfaceID InterfaceID)
{
    NetworkInterfaceInfo *intf = m->HostInterfaces;
    while (intf && intf->InterfaceID != InterfaceID) intf = intf->next;
    return(intf);
}

mDNSlocal NetworkInterfaceInfo *FirstIPv4LLInterfaceForID(mDNS *const m, const mDNSInterfaceID InterfaceID)
{
    NetworkInterfaceInfo *intf;

    if (!InterfaceID)
        return mDNSNULL;

    // Note: We don't check for InterfaceActive, as the active interface could be IPv6 and
    // we still want to find the first IPv4 Link-Local interface
    for (intf = m->HostInterfaces; intf; intf = intf->next)
    {
        if (intf->InterfaceID == InterfaceID &&
            intf->ip.type == mDNSAddrType_IPv4 && mDNSv4AddressIsLinkLocal(&intf->ip.ip.v4))
        {
            debugf("FirstIPv4LLInterfaceForID: found LL interface with address %.4a", &intf->ip.ip.v4);
            return intf;
        }
    }
    return (mDNSNULL);
}

mDNSexport char *InterfaceNameForID(mDNS *const m, const mDNSInterfaceID InterfaceID)
{
    NetworkInterfaceInfo *intf = FirstInterfaceForID(m, InterfaceID);
    return(intf ? intf->ifname : mDNSNULL);
}

// Caller should hold the lock
mDNSlocal void GenerateNegativeResponseEx(mDNS *const m, mDNSInterfaceID InterfaceID, QC_result qc, mDNSBool noData)
{
    DNSQuestion *q;
    if (!m->CurrentQuestion) { LogMsg("GenerateNegativeResponse: ERROR!! CurrentQuestion not set"); return; }
    q = m->CurrentQuestion;
    LogRedact(MDNS_LOG_CATEGORY_DEFAULT, MDNS_LOG_INFO,
           "[R%d->Q%d] GenerateNegativeResponse: Generating negative response for question " PRI_DM_NAME " (" PUB_S ")",
           q->request_id, mDNSVal16(q->TargetQID), DM_NAME_PARAM(&q->qname), DNSTypeName(q->qtype));

    MakeNegativeCacheRecord(m, &m->rec.r, &q->qname, q->qnamehash, q->qtype, q->qclass, 60, InterfaceID, mDNSNULL);
    m->rec.r.resrec.negativeRecordType = noData ? kNegativeRecordType_NoData : kNegativeRecordType_Unspecified;

    // We need to force the response through in the following cases
    //
    //  a) SuppressUnusable questions that are suppressed
    //  b) Append search domains and retry the question
    //
    // The question may not have set Intermediates in which case we don't deliver negative responses. So, to force
    // through we use "QC_forceresponse".
    AnswerCurrentQuestionWithResourceRecord(m, &m->rec.r, qc);
    if (m->CurrentQuestion == q) { q->ThisQInterval = 0; }              // Deactivate this question
    // Don't touch the question after this
    m->rec.r.resrec.RecordType = 0;     // Clear RecordType to show we're not still using it
}
#define GenerateNegativeResponse(M, INTERFACE_ID, QC) GenerateNegativeResponseEx(M, INTERFACE_ID, QC, mDNSfalse)

mDNSexport void AnswerQuestionByFollowingCNAME(mDNS *const m, DNSQuestion *q, ResourceRecord *rr)
{
    const mDNSBool selfref = SameDomainName(&q->qname, &rr->rdata->u.name);
    if (q->CNAMEReferrals >= 10 || selfref)
    {
        LogRedact(MDNS_LOG_CATEGORY_DEFAULT, MDNS_LOG_INFO,
               "[R%d->Q%d] AnswerQuestionByFollowingCNAME: %p " PRI_DM_NAME " (" PUB_S ")  NOT following CNAME referral %d" PUB_S " for " PRI_S,
               q->request_id, mDNSVal16(q->TargetQID), q, DM_NAME_PARAM(&q->qname), DNSTypeName(q->qtype),
               q->CNAMEReferrals, selfref ? " (Self-Referential)" : "", RRDisplayString(m, rr));

    }
    else
    {
        UDPSocket *sock = q->LocalSocket;
        mDNSOpaque16 id = q->TargetQID;
#if MDNSRESPONDER_SUPPORTS(APPLE, METRICS)
        uDNSMetrics metrics;
#endif

        q->LocalSocket = mDNSNULL;

        // The SameDomainName check above is to ignore bogus CNAME records that point right back at
        // themselves. Without that check we can get into a case where we have two duplicate questions,
        // A and B, and when we stop question A, UpdateQuestionDuplicates copies the value of CNAMEReferrals
        // from A to B, and then A is re-appended to the end of the list as a duplicate of B (because
        // the target name is still the same), and then when we stop question B, UpdateQuestionDuplicates
        // copies the B's value of CNAMEReferrals back to A, and we end up not incrementing CNAMEReferrals
        // for either of them. This is not a problem for CNAME loops of two or more records because in
        // those cases the newly re-appended question A has a different target name and therefore cannot be
        // a duplicate of any other question ('B') which was itself a duplicate of the previous question A.

        // Right now we just stop and re-use the existing query. If we really wanted to be 100% perfect,
        // and track CNAMEs coming and going, we should really create a subordinate query here,
        // which we would subsequently cancel and retract if the CNAME referral record were removed.
        // In reality this is such a corner case we'll ignore it until someone actually needs it.

        LogRedact(MDNS_LOG_CATEGORY_DEFAULT, MDNS_LOG_INFO,
               "[R%d->Q%d] AnswerQuestionByFollowingCNAME: %p " PRI_DM_NAME " (" PUB_S ") following CNAME referral %d for " PRI_S,
               q->request_id, mDNSVal16(q->TargetQID), q, DM_NAME_PARAM(&q->qname), DNSTypeName(q->qtype),
               q->CNAMEReferrals, RRDisplayString(m, rr));

#if MDNSRESPONDER_SUPPORTS(APPLE, QUERIER)
        if (!mDNSOpaque16IsZero(q->TargetQID))
        {
            // Must be called before zeroing out q->metrics below.
            Querier_PrepareQuestionForCNAMERestart(q);
        }
#endif
#if MDNSRESPONDER_SUPPORTS(APPLE, METRICS)
        if ((q->CNAMEReferrals == 0) && !q->metrics.originalQName)
        {
            domainname *    qName;
            mDNSu16         qNameLen;

            qNameLen = DomainNameLength(&q->qname);
            if ((qNameLen > 0) && (qNameLen <= MAX_DOMAIN_NAME))
            {
                qName = (domainname *) mDNSPlatformMemAllocate(qNameLen);
                if (qName)
                {
                    mDNSPlatformMemCopy(qName->c, q->qname.c, qNameLen);
                    q->metrics.originalQName = qName;
                }
            }
        }
        metrics = q->metrics;
        // The metrics will be transplanted to the restarted question, so zero out the old copy instead of using
        // uDNSMetricsClear(), which will free any pointers to allocated memory.
        mDNSPlatformMemZero(&q->metrics, sizeof(q->metrics));
#endif
        mDNS_StopQuery_internal(m, q);                              // Stop old query
        AssignDomainName(&q->qname, &rr->rdata->u.name);            // Update qname
        q->qnamehash = DomainNameHashValue(&q->qname);              // and namehash
        // If a unicast query results in a CNAME that points to a .local, we need to re-try
        // this as unicast. Setting the mDNSInterface_Unicast tells mDNS_StartQuery_internal
        // to try this as unicast query even though it is a .local name
        if (!mDNSOpaque16IsZero(q->TargetQID) && IsLocalDomain(&q->qname))
        {
            LogRedact(MDNS_LOG_CATEGORY_DEFAULT, MDNS_LOG_INFO,
                   "[R%d->Q%d] AnswerQuestionByFollowingCNAME: Resolving a .local CNAME %p " PRI_DM_NAME " (" PUB_S ") Record " PRI_S,
                   q->request_id, mDNSVal16(q->TargetQID), q, DM_NAME_PARAM(&q->qname), DNSTypeName(q->qtype), RRDisplayString(m, rr));
            q->IsUnicastDotLocal = mDNStrue;
        }
        q->CNAMEReferrals += 1;                                     // Increment value before calling mDNS_StartQuery_internal
        const mDNSu32 c = q->CNAMEReferrals;                        // Stash a copy of the new q->CNAMEReferrals value
        mDNS_StartQuery_internal(m, q);                             // start new query
        // Record how many times we've done this. We need to do this *after* mDNS_StartQuery_internal,
        // because mDNS_StartQuery_internal re-initializes CNAMEReferrals to zero
        q->CNAMEReferrals = c;
#if MDNSRESPONDER_SUPPORTS(APPLE, METRICS)
        metrics.expiredAnswerState  = q->metrics.expiredAnswerState; //  We want the newly initialized state for this value
        metrics.dnsOverTCPState     = q->metrics.dnsOverTCPState;    //  We want the newly initialized state for this value
        q->metrics = metrics;
#endif
        if (sock)
        {
            // If our new query is a duplicate, then it can't have a socket of its own, so we have to close the one we saved.
            if (q->DuplicateOf) mDNSPlatformUDPClose(sock);
            else
            {
                // Transplant the old socket into the new question, and copy the query ID across too.
                // No need to close the old q->LocalSocket value because it won't have been created yet (they're made lazily on-demand).
                q->LocalSocket = sock;
                q->TargetQID = id;
            }
        }
    }
}

#ifdef USE_LIBIDN

#include <unicode/uidna.h>

// #define DEBUG_PUNYCODE 1

mDNSlocal mDNSu8 *PunycodeConvert(const mDNSu8 *const src, mDNSu8 *const dst, const mDNSu8 *const end)
{
    UErrorCode errorCode = U_ZERO_ERROR;
    UIDNAInfo info = UIDNA_INFO_INITIALIZER;
    UIDNA *uts46 = uidna_openUTS46(UIDNA_USE_STD3_RULES|UIDNA_NONTRANSITIONAL_TO_UNICODE, &errorCode);
    int32_t len = uidna_nameToASCII_UTF8(uts46, (const char *)src+1, src[0], (char *)dst+1, (int32_t)(end-(dst+1)), &info, &errorCode);
    uidna_close(uts46);
    #if DEBUG_PUNYCODE
    if (errorCode) LogMsg("uidna_nameToASCII_UTF8(%##s) failed errorCode %d", src, errorCode);
    if (info.errors) LogMsg("uidna_nameToASCII_UTF8(%##s) failed info.errors 0x%08X", src, info.errors);
    if (len > MAX_DOMAIN_LABEL) LogMsg("uidna_nameToASCII_UTF8(%##s) result too long %d", src, len);
    #endif
    if (errorCode || info.errors || len > MAX_DOMAIN_LABEL) return mDNSNULL;
    *dst = len;
    return(dst + 1 + len);
}

mDNSlocal mDNSBool IsHighASCIILabel(const mDNSu8 *d)
{
    int i;
    for (i=1; i<=d[0]; i++) if (d[i] & 0x80) return mDNStrue;
    return mDNSfalse;
}

mDNSlocal const mDNSu8 *FindLastHighASCIILabel(const domainname *const d)
{
    const mDNSu8 *ptr = d->c;
    const mDNSu8 *ans = mDNSNULL;
    while (ptr[0])
    {
        const mDNSu8 *const next = ptr + 1 + ptr[0];
        if (ptr[0] > MAX_DOMAIN_LABEL || next >= d->c + MAX_DOMAIN_NAME) return mDNSNULL;
        if (IsHighASCIILabel(ptr)) ans = ptr;
        ptr = next;
    }
    return ans;
}

mDNSlocal mDNSBool PerformNextPunycodeConversion(const DNSQuestion *const q, domainname *const newname)
{
    const mDNSu8 *h = FindLastHighASCIILabel(&q->qname);
    #if DEBUG_PUNYCODE
    LogMsg("PerformNextPunycodeConversion: %##s (%s) Last High-ASCII Label %##s", q->qname.c, DNSTypeName(q->qtype), h);
    #endif
    if (!h) return mDNSfalse;  // There are no high-ascii labels to convert

    mDNSu8 *const dst = PunycodeConvert(h, newname->c + (h - q->qname.c), newname->c + MAX_DOMAIN_NAME);
    if (!dst)
        return mDNSfalse;  // The label was not convertible to Punycode
    else
    {
        // If Punycode conversion of final eligible label was successful, copy the rest of the domainname
        const mDNSu8 *const src = h + 1 + h[0];
        const mDNSu8 remainder  = DomainNameLength((domainname*)src);
        if (dst + remainder > newname->c + MAX_DOMAIN_NAME) return mDNSfalse;  // Name too long -- cannot be converted to Punycode

        mDNSPlatformMemCopy(newname->c, q->qname.c, (mDNSu32)(h - q->qname.c));  // Fill in the leading part
        mDNSPlatformMemCopy(dst, src, remainder);                     // Fill in the trailing part
        #if DEBUG_PUNYCODE
        LogMsg("PerformNextPunycodeConversion: %##s converted to %##s", q->qname.c, newname->c);
        #endif
        return mDNStrue;
    }
}

#endif // USE_LIBIDN

// For a single given DNSQuestion pointed to by CurrentQuestion, deliver an add/remove result for the single given AuthRecord
// Note: All the callers should use the m->CurrentQuestion to see if the question is still valid or not
mDNSlocal void AnswerLocalQuestionWithLocalAuthRecord(mDNS *const m, AuthRecord *rr, QC_result AddRecord)
{
    DNSQuestion *q = m->CurrentQuestion;
    mDNSBool followcname;

    if (!q)
    {
        LogMsg("AnswerLocalQuestionWithLocalAuthRecord: ERROR!! CurrentQuestion NULL while answering with %s", ARDisplayString(m, rr));
        return;
    }

    followcname = FollowCNAME(q, &rr->resrec, AddRecord);

    // We should not be delivering results for record types Unregistered, Deregistering, and (unverified) Unique
    if (!(rr->resrec.RecordType & kDNSRecordTypeActiveMask))
    {
        LogMsg("AnswerLocalQuestionWithLocalAuthRecord: *NOT* delivering %s event for local record type %X %s",
               AddRecord ? "Add" : "Rmv", rr->resrec.RecordType, ARDisplayString(m, rr));
        return;
    }

    // Indicate that we've given at least one positive answer for this record, so we should be prepared to send a goodbye for it
    if (AddRecord) rr->AnsweredLocalQ = mDNStrue;
    mDNS_DropLockBeforeCallback();      // Allow client to legally make mDNS API calls from the callback
    if (q->QuestionCallback && !q->NoAnswer)
    {
        q->CurrentAnswers += AddRecord ? 1 : -1;
        if (UniqueLocalOnlyRecord(rr))
        {
            if (!followcname || q->ReturnIntermed)
            {
                // Don't send this packet on the wire as we answered from /etc/hosts
                q->ThisQInterval = 0;
                q->LOAddressAnswers += AddRecord ? 1 : -1;
                q->QuestionCallback(m, q, &rr->resrec, AddRecord);
            }
            mDNS_ReclaimLockAfterCallback();    // Decrement mDNS_reentrancy to block mDNS API calls again
            // The callback above could have caused the question to stop. Detect that
            // using m->CurrentQuestion
            if (followcname && m->CurrentQuestion == q)
                AnswerQuestionByFollowingCNAME(m, q, &rr->resrec);
            return;
        }
        else
        {
            q->QuestionCallback(m, q, &rr->resrec, AddRecord);
        }
    }
    mDNS_ReclaimLockAfterCallback();    // Decrement mDNS_reentrancy to block mDNS API calls again
}

mDNSlocal void AnswerInterfaceAnyQuestionsWithLocalAuthRecord(mDNS *const m, AuthRecord *ar, QC_result AddRecord)
{
    if (m->CurrentQuestion)
        LogMsg("AnswerInterfaceAnyQuestionsWithLocalAuthRecord: ERROR m->CurrentQuestion already set: %##s (%s)",
               m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));
    m->CurrentQuestion = m->Questions;
    while (m->CurrentQuestion && m->CurrentQuestion != m->NewQuestions)
    {
        mDNSBool answered;
        DNSQuestion *q = m->CurrentQuestion;
        if (RRAny(ar))
            answered = AuthRecordAnswersQuestion(ar, q);
        else
            answered = LocalOnlyRecordAnswersQuestion(ar, q);
        if (answered)
            AnswerLocalQuestionWithLocalAuthRecord(m, ar, AddRecord);       // MUST NOT dereference q again
        if (m->CurrentQuestion == q)    // If m->CurrentQuestion was not auto-advanced, do it ourselves now
            m->CurrentQuestion = q->next;
    }
    m->CurrentQuestion = mDNSNULL;
}

// When a new local AuthRecord is created or deleted, AnswerAllLocalQuestionsWithLocalAuthRecord()
// delivers the appropriate add/remove events to listening questions:
// 1. It runs though all our LocalOnlyQuestions delivering answers as appropriate,
//    stopping if it reaches a NewLocalOnlyQuestion -- brand-new questions are handled by AnswerNewLocalOnlyQuestion().
// 2. If the AuthRecord is marked mDNSInterface_LocalOnly or mDNSInterface_P2P, then it also runs though
//    our main question list, delivering answers to mDNSInterface_Any questions as appropriate,
//    stopping if it reaches a NewQuestion -- brand-new questions are handled by AnswerNewQuestion().
//
// AnswerAllLocalQuestionsWithLocalAuthRecord is used by the m->NewLocalRecords loop in mDNS_Execute(),
// and by mDNS_Deregister_internal()

mDNSlocal void AnswerAllLocalQuestionsWithLocalAuthRecord(mDNS *const m, AuthRecord *ar, QC_result AddRecord)
{
    if (m->CurrentQuestion)
        LogMsg("AnswerAllLocalQuestionsWithLocalAuthRecord ERROR m->CurrentQuestion already set: %##s (%s)",
               m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));

    m->CurrentQuestion = m->LocalOnlyQuestions;
    while (m->CurrentQuestion && m->CurrentQuestion != m->NewLocalOnlyQuestions)
    {
        mDNSBool answered;
        DNSQuestion *q = m->CurrentQuestion;
        // We are called with both LocalOnly/P2P record or a regular AuthRecord
        if (RRAny(ar))
            answered = AuthRecordAnswersQuestion(ar, q);
        else
            answered = LocalOnlyRecordAnswersQuestion(ar, q);
        if (answered)
            AnswerLocalQuestionWithLocalAuthRecord(m, ar, AddRecord);           // MUST NOT dereference q again
        if (m->CurrentQuestion == q)    // If m->CurrentQuestion was not auto-advanced, do it ourselves now
            m->CurrentQuestion = q->next;
    }

    m->CurrentQuestion = mDNSNULL;

    // If this AuthRecord is marked LocalOnly or P2P, then we want to deliver it to all local 'mDNSInterface_Any' questions
    if (ar->ARType == AuthRecordLocalOnly || ar->ARType == AuthRecordP2P)
        AnswerInterfaceAnyQuestionsWithLocalAuthRecord(m, ar, AddRecord);

}

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark -
#pragma mark - Resource Record Utility Functions
#endif

#define RRTypeIsAddressType(T) ((T) == kDNSType_A || (T) == kDNSType_AAAA)

mDNSlocal mDNSBool ResourceRecordIsValidAnswer(const AuthRecord *const rr)
{
    if ((rr->resrec.RecordType & kDNSRecordTypeActiveMask) &&
        ((rr->Additional1 == mDNSNULL) || (rr->Additional1->resrec.RecordType & kDNSRecordTypeActiveMask)) &&
        ((rr->Additional2 == mDNSNULL) || (rr->Additional2->resrec.RecordType & kDNSRecordTypeActiveMask)) &&
        ((rr->DependentOn == mDNSNULL) || (rr->DependentOn->resrec.RecordType & kDNSRecordTypeActiveMask)))
    {
        return mDNStrue;
    }
    else
    {
        return mDNSfalse;
    }
}

mDNSlocal mDNSBool IsInterfaceValidForAuthRecord(const AuthRecord *const rr, const mDNSInterfaceID InterfaceID)
{
    if (rr->resrec.InterfaceID == mDNSInterface_Any)
    {
        return mDNSPlatformValidRecordForInterface(rr, InterfaceID);
    }
    else
    {
        return ((rr->resrec.InterfaceID == InterfaceID) ? mDNStrue : mDNSfalse);
    }
}

mDNSlocal mDNSBool ResourceRecordIsValidInterfaceAnswer(const AuthRecord *const rr, const mDNSInterfaceID interfaceID)
{
    return ((IsInterfaceValidForAuthRecord(rr, interfaceID) && ResourceRecordIsValidAnswer(rr)) ? mDNStrue : mDNSfalse);
}

#define DefaultProbeCountForTypeUnique ((mDNSu8)3)
#define DefaultProbeCountForRecordType(X)      ((X) == kDNSRecordTypeUnique ? DefaultProbeCountForTypeUnique : (mDNSu8)0)

// Parameters for handling probing conflicts
#define kMaxAllowedMCastProbingConflicts 1                     // Maximum number of conflicts to allow from mcast messages.
#define kProbingConflictPauseDuration    mDNSPlatformOneSecond // Duration of probing pause after an allowed mcast conflict.

// See RFC 6762: "8.3 Announcing"
// "The Multicast DNS responder MUST send at least two unsolicited responses, one second apart."
// Send 4, which is really 8 since we send on both IPv4 and IPv6.
#define InitialAnnounceCount ((mDNSu8)4)

// For goodbye packets we set the count to 3, and for wakeups we set it to 18
// (which will be up to 15 wakeup attempts over the course of 30 seconds,
// and then if the machine fails to wake, 3 goodbye packets).
#define GoodbyeCount ((mDNSu8)3)
#define WakeupCount ((mDNSu8)18)
#define MAX_PROBE_RESTARTS ((mDNSu8)20)
#define MAX_GHOST_TIME ((mDNSs32)((60*60*24*7)*mDNSPlatformOneSecond))  //  One week

// Number of wakeups we send if WakeOnResolve is set in the question
#define InitialWakeOnResolveCount ((mDNSu8)3)

// Note that the announce intervals use exponential backoff, doubling each time. The probe intervals do not.
// This means that because the announce interval is doubled after sending the first packet, the first
// observed on-the-wire inter-packet interval between announcements is actually one second.
// The half-second value here may be thought of as a conceptual (non-existent) half-second delay *before* the first packet is sent.
#define DefaultProbeIntervalForTypeUnique (mDNSPlatformOneSecond/4)
#define DefaultAnnounceIntervalForTypeShared (mDNSPlatformOneSecond/2)
#define DefaultAnnounceIntervalForTypeUnique (mDNSPlatformOneSecond/2)

#define DefaultAPIntervalForRecordType(X)  ((X) &kDNSRecordTypeActiveSharedMask ? DefaultAnnounceIntervalForTypeShared : \
                                            (X) &kDNSRecordTypeUnique           ? DefaultProbeIntervalForTypeUnique    : \
                                            (X) &kDNSRecordTypeActiveUniqueMask ? DefaultAnnounceIntervalForTypeUnique : 0)

#define TimeToAnnounceThisRecord(RR,time) ((RR)->AnnounceCount && (time) - ((RR)->LastAPTime + (RR)->ThisAPInterval) >= 0)
#define TicksTTL(RR) ((mDNSs32)(RR)->resrec.rroriginalttl * mDNSPlatformOneSecond)
#define RRExpireTime(RR) ((RR)->TimeRcvd + TicksTTL(RR))

// Adjustment factor to avoid race condition (used for unicast cache entries) :
// Suppose real record has TTL of 3600, and our local caching server has held it for 3500 seconds, so it returns an aged TTL of 100.
// If we do our normal refresh at 80% of the TTL, our local caching server will return 20 seconds, so we'll do another
// 80% refresh after 16 seconds, and then the server will return 4 seconds, and so on, in the fashion of Zeno's paradox.
// To avoid this, we extend the record's effective TTL to give it a little extra grace period.
// We adjust the 100 second TTL to 127. This means that when we do our 80% query after 102 seconds,
// the cached copy at our local caching server will already have expired, so the server will be forced
// to fetch a fresh copy from the authoritative server, and then return a fresh record with the full TTL of 3600 seconds.

#define RRAdjustTTL(ttl) ((ttl) + ((ttl)/4) + 2)
#define RRUnadjustedTTL(ttl) ((((ttl) - 2) * 4) / 5)

#define MaxUnansweredQueries 4

// SameResourceRecordSignature returns true if two resources records have the same name, type, and class, and may be sent
// (or were received) on the same interface (i.e. if *both* records specify an interface, then it has to match).
// TTL and rdata may differ.
// This is used for cache flush management:
// When sending a unique record, all other records matching "SameResourceRecordSignature" must also be sent
// When receiving a unique record, all old cache records matching "SameResourceRecordSignature" are flushed

// SameResourceRecordNameClassInterface is functionally the same as SameResourceRecordSignature, except rrtype does not have to match

#define SameResourceRecordSignature(A,B) (A)->resrec.rrtype == (B)->resrec.rrtype && SameResourceRecordNameClassInterface((A),(B))

mDNSlocal mDNSBool SameResourceRecordNameClassInterface(const AuthRecord *const r1, const AuthRecord *const r2)
{
    if (!r1) { LogMsg("SameResourceRecordSignature ERROR: r1 is NULL"); return(mDNSfalse); }
    if (!r2) { LogMsg("SameResourceRecordSignature ERROR: r2 is NULL"); return(mDNSfalse); }
    if (r1->resrec.InterfaceID &&
        r2->resrec.InterfaceID &&
        r1->resrec.InterfaceID != r2->resrec.InterfaceID) return(mDNSfalse);
    return (mDNSBool)(
               r1->resrec.rrclass  == r2->resrec.rrclass &&
               r1->resrec.namehash == r2->resrec.namehash &&
               SameDomainName(r1->resrec.name, r2->resrec.name));
}

// PacketRRMatchesSignature behaves as SameResourceRecordSignature, except that types may differ if our
// authoratative record is unique (as opposed to shared). For unique records, we are supposed to have
// complete ownership of *all* types for this name, so *any* record type with the same name is a conflict.
// In addition, when probing we send our questions with the wildcard type kDNSQType_ANY,
// so a response of any type should match, even if it is not actually the type the client plans to use.

// For now, to make it easier to avoid false conflicts, we treat SPS Proxy records like shared records,
// and require the rrtypes to match for the rdata to be considered potentially conflicting
mDNSlocal mDNSBool PacketRRMatchesSignature(const CacheRecord *const pktrr, const AuthRecord *const authrr)
{
    if (!pktrr)  { LogMsg("PacketRRMatchesSignature ERROR: pktrr is NULL"); return(mDNSfalse); }
    if (!authrr) { LogMsg("PacketRRMatchesSignature ERROR: authrr is NULL"); return(mDNSfalse); }
    if (pktrr->resrec.InterfaceID &&
        authrr->resrec.InterfaceID &&
        pktrr->resrec.InterfaceID != authrr->resrec.InterfaceID) return(mDNSfalse);
    if (!(authrr->resrec.RecordType & kDNSRecordTypeUniqueMask) || authrr->WakeUp.HMAC.l[0])
        if (pktrr->resrec.rrtype != authrr->resrec.rrtype) return(mDNSfalse);
    if ((authrr->resrec.InterfaceID == mDNSInterface_Any) &&
        !mDNSPlatformValidRecordForInterface(authrr, pktrr->resrec.InterfaceID)) return(mDNSfalse);
    return (mDNSBool)(
               pktrr->resrec.rrclass == authrr->resrec.rrclass &&
               pktrr->resrec.namehash == authrr->resrec.namehash &&
               SameDomainName(pktrr->resrec.name, authrr->resrec.name));
}

// CacheRecord *ka is the CacheRecord from the known answer list in the query.
// This is the information that the requester believes to be correct.
// AuthRecord *rr is the answer we are proposing to give, if not suppressed.
// This is the information that we believe to be correct.
// We've already determined that we plan to give this answer on this interface
// (either the record is non-specific, or it is specific to this interface)
// so now we just need to check the name, type, class, rdata and TTL.
mDNSlocal mDNSBool ShouldSuppressKnownAnswer(const CacheRecord *const ka, const AuthRecord *const rr)
{
    // If RR signature is different, or data is different, then don't suppress our answer
    if (!IdenticalResourceRecord(&ka->resrec, &rr->resrec)) return(mDNSfalse);

    // If the requester's indicated TTL is less than half the real TTL,
    // we need to give our answer before the requester's copy expires.
    // If the requester's indicated TTL is at least half the real TTL,
    // then we can suppress our answer this time.
    // If the requester's indicated TTL is greater than the TTL we believe,
    // then that's okay, and we don't need to do anything about it.
    // (If two responders on the network are offering the same information,
    // that's okay, and if they are offering the information with different TTLs,
    // the one offering the lower TTL should defer to the one offering the higher TTL.)
    return (mDNSBool)(ka->resrec.rroriginalttl >= rr->resrec.rroriginalttl / 2);
}

mDNSlocal void SetNextAnnounceProbeTime(mDNS *const m, const AuthRecord *const rr)
{
    if (rr->resrec.RecordType == kDNSRecordTypeUnique)
    {
        if ((rr->LastAPTime + rr->ThisAPInterval) - m->timenow > mDNSPlatformOneSecond * 10)
        {
            LogMsg("SetNextAnnounceProbeTime: ProbeCount %d Next in %d %s", rr->ProbeCount, (rr->LastAPTime + rr->ThisAPInterval) - m->timenow, ARDisplayString(m, rr));
            LogMsg("SetNextAnnounceProbeTime: m->SuppressProbes %d m->timenow %d diff %d", m->SuppressProbes, m->timenow, m->SuppressProbes - m->timenow);
        }
        if (m->NextScheduledProbe - (rr->LastAPTime + rr->ThisAPInterval) >= 0)
            m->NextScheduledProbe = (rr->LastAPTime + rr->ThisAPInterval);
        // Some defensive code:
        // If (rr->LastAPTime + rr->ThisAPInterval) happens to be far in the past, we don't want to allow
        // NextScheduledProbe to be set excessively in the past, because that can cause bad things to happen.
        // See: <rdar://problem/7795434> mDNS: Sometimes advertising stops working and record interval is set to zero
        if (m->NextScheduledProbe - m->timenow < 0)
            m->NextScheduledProbe = m->timenow;
    }
    else if (rr->AnnounceCount && (ResourceRecordIsValidAnswer(rr) || rr->resrec.RecordType == kDNSRecordTypeDeregistering))
    {
        if (m->NextScheduledResponse - (rr->LastAPTime + rr->ThisAPInterval) >= 0)
            m->NextScheduledResponse = (rr->LastAPTime + rr->ThisAPInterval);
    }
}

mDNSlocal void InitializeLastAPTime(mDNS *const m, AuthRecord *const rr)
{
    // For reverse-mapping Sleep Proxy PTR records, probe interval is one second
    rr->ThisAPInterval = rr->AddressProxy.type ? mDNSPlatformOneSecond : DefaultAPIntervalForRecordType(rr->resrec.RecordType);

    // * If this is a record type that's going to probe, then we use the m->SuppressProbes time.
    // * Otherwise, if it's not going to probe, but m->SuppressProbes is set because we have other
    //   records that are going to probe, then we delay its first announcement so that it will
    //   go out synchronized with the first announcement for the other records that *are* probing.
    //   This is a minor performance tweak that helps keep groups of related records synchronized together.
    //   The addition of "interval / 2" is to make sure that, in the event that any of the probes are
    //   delayed by a few milliseconds, this announcement does not inadvertently go out *before* the probing is complete.
    //   When the probing is complete and those records begin to announce, these records will also be picked up and accelerated,
    //   because they will meet the criterion of being at least half-way to their scheduled announcement time.
    // * If it's not going to probe and m->SuppressProbes is not already set then we should announce immediately.

    if (rr->ProbeCount)
    {
        rr->ProbingConflictCount = 0;
        // If we have no probe suppression time set, or it is in the past, set it now
        if (m->SuppressProbes == 0 || m->SuppressProbes - m->timenow < 0)
        {
            // To allow us to aggregate probes when a group of services are registered together,
            // the first probe is delayed by a random delay in the range 1/8 to 1/4 second.
            // This means the common-case behaviour is:
            // randomized wait; probe
            // 1/4 second wait; probe
            // 1/4 second wait; probe
            // 1/4 second wait; announce (i.e. service is normally announced 7/8 to 1 second after being registered)
            m->SuppressProbes = NonZeroTime(m->timenow + DefaultProbeIntervalForTypeUnique/2 + mDNSRandom(DefaultProbeIntervalForTypeUnique/2));

            // If we already have a *probe* scheduled to go out sooner, then use that time to get better aggregation
            if (m->SuppressProbes - m->NextScheduledProbe >= 0)
                m->SuppressProbes = NonZeroTime(m->NextScheduledProbe);
            if (m->SuppressProbes - m->timenow < 0)     // Make sure we don't set m->SuppressProbes excessively in the past
                m->SuppressProbes = m->timenow;

            // If we already have a *query* scheduled to go out sooner, then use that time to get better aggregation
            if (m->SuppressProbes - m->NextScheduledQuery >= 0)
                m->SuppressProbes = NonZeroTime(m->NextScheduledQuery);
            if (m->SuppressProbes - m->timenow < 0)     // Make sure we don't set m->SuppressProbes excessively in the past
                m->SuppressProbes = m->timenow;

            // except... don't expect to be able to send before the m->SuppressSending timer fires
            if (m->SuppressSending && m->SuppressProbes - m->SuppressSending < 0)
                m->SuppressProbes = NonZeroTime(m->SuppressSending);

            if (m->SuppressProbes - m->timenow > mDNSPlatformOneSecond * 8)
            {
                LogMsg("InitializeLastAPTime ERROR m->SuppressProbes %d m->NextScheduledProbe %d m->NextScheduledQuery %d m->SuppressSending %d %d",
                       m->SuppressProbes     - m->timenow,
                       m->NextScheduledProbe - m->timenow,
                       m->NextScheduledQuery - m->timenow,
                       m->SuppressSending,
                       m->SuppressSending    - m->timenow);
                m->SuppressProbes = NonZeroTime(m->timenow + DefaultProbeIntervalForTypeUnique/2 + mDNSRandom(DefaultProbeIntervalForTypeUnique/2));
            }
        }
        rr->LastAPTime = m->SuppressProbes - rr->ThisAPInterval;
    }
    // Skip kDNSRecordTypeKnownUnique and kDNSRecordTypeShared records here and set their LastAPTime in the "else" block below so
    // that they get announced immediately, otherwise, their announcement would be delayed until the based on the SuppressProbes value.
    else if ((rr->resrec.RecordType != kDNSRecordTypeKnownUnique) && (rr->resrec.RecordType != kDNSRecordTypeShared) && m->SuppressProbes && (m->SuppressProbes - m->timenow >= 0))
        rr->LastAPTime = m->SuppressProbes - rr->ThisAPInterval + DefaultProbeIntervalForTypeUnique * DefaultProbeCountForTypeUnique + rr->ThisAPInterval / 2;
    else
        rr->LastAPTime = m->timenow - rr->ThisAPInterval;

    // For reverse-mapping Sleep Proxy PTR records we don't want to start probing instantly -- we
    // wait one second to give the client a chance to go to sleep, and then start our ARP/NDP probing.
    // After three probes one second apart with no answer, we conclude the client is now sleeping
    // and we can begin broadcasting our announcements to take over ownership of that IP address.
    // If we don't wait for the client to go to sleep, then when the client sees our ARP Announcements there's a risk
    // (depending on the OS and networking stack it's using) that it might interpret it as a conflict and change its IP address.
    if (rr->AddressProxy.type)
        rr->LastAPTime = m->timenow;

    // Set LastMCTime to now, to inhibit multicast responses
    // (no need to send additional multicast responses when we're announcing anyway)
    rr->LastMCTime      = m->timenow;
    rr->LastMCInterface = mDNSInterfaceMark;

    SetNextAnnounceProbeTime(m, rr);
}

mDNSlocal const domainname *SetUnicastTargetToHostName(mDNS *const m, AuthRecord *rr)
{
    const domainname *target;
    if (rr->AutoTarget)
    {
        rr->AutoTarget = Target_AutoHostAndNATMAP;
    }

    target = GetServiceTarget(m, rr);
    if (!target || target->c[0] == 0)
    {
        // defer registration until we've got a target
        LogInfo("SetUnicastTargetToHostName No target for %s", ARDisplayString(m, rr));
        rr->state = regState_NoTarget;
        return mDNSNULL;
    }
    else
    {
        LogInfo("SetUnicastTargetToHostName target %##s for resource record %s", target->c, ARDisplayString(m,rr));
        return target;
    }
}

#if MDNSRESPONDER_SUPPORTS(APPLE, RANDOM_AWDL_HOSTNAME)
mDNSlocal mDNSBool AuthRecordIncludesOrIsAWDL(const AuthRecord *const ar)
{
    return ((AuthRecordIncludesAWDL(ar) || mDNSPlatformInterfaceIsAWDL(ar->resrec.InterfaceID)) ? mDNStrue : mDNSfalse);
}
#endif

// Right now this only applies to mDNS (.local) services where the target host is always m->MulticastHostname
// Eventually we should unify this with GetServiceTarget() in uDNS.c
mDNSlocal void SetTargetToHostName(mDNS *const m, AuthRecord *const rr)
{
    domainname *const target = GetRRDomainNameTarget(&rr->resrec);
    const domainname *newname;

#if MDNSRESPONDER_SUPPORTS(APPLE, RANDOM_AWDL_HOSTNAME)
    if (AuthRecordIncludesOrIsAWDL(rr))
    {
        newname = &m->RandomizedHostname;
    }
    else
#endif
    {
        newname = &m->MulticastHostname;
    }
    if (!target) LogInfo("SetTargetToHostName: Don't know how to set the target of rrtype %s", DNSTypeName(rr->resrec.rrtype));

    if (!(rr->ForceMCast || rr->ARType == AuthRecordLocalOnly || rr->ARType == AuthRecordP2P || IsLocalDomain(&rr->namestorage)))
    {
        const domainname *const n = SetUnicastTargetToHostName(m, rr);
        if (n) newname = n;
        else { if (target) target->c[0] = 0; SetNewRData(&rr->resrec, mDNSNULL, 0); return; }
    }

    if (target && SameDomainName(target, newname))
        debugf("SetTargetToHostName: Target of %##s is already %##s", rr->resrec.name->c, target->c);

    if (target && !SameDomainName(target, newname))
    {
        AssignDomainName(target, newname);
        SetNewRData(&rr->resrec, mDNSNULL, 0);      // Update rdlength, rdestimate, rdatahash

        // If we're in the middle of probing this record, we need to start again,
        // because changing its rdata may change the outcome of the tie-breaker.
        // (If the record type is kDNSRecordTypeUnique (unconfirmed unique) then DefaultProbeCountForRecordType is non-zero.)
        rr->ProbeCount     = DefaultProbeCountForRecordType(rr->resrec.RecordType);

        // If we've announced this record, we really should send a goodbye packet for the old rdata before
        // changing to the new rdata. However, in practice, we only do SetTargetToHostName for unique records,
        // so when we announce them we'll set the kDNSClass_UniqueRRSet and clear any stale data that way.
        if (rr->RequireGoodbye && rr->resrec.RecordType == kDNSRecordTypeShared)
            debugf("Have announced shared record %##s (%s) at least once: should have sent a goodbye packet before updating",
                   rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));

        rr->AnnounceCount  = InitialAnnounceCount;
        rr->RequireGoodbye = mDNSfalse;
        rr->ProbeRestartCount = 0;
        InitializeLastAPTime(m, rr);
    }
}

mDNSlocal void AcknowledgeRecord(mDNS *const m, AuthRecord *const rr)
{
    if (rr->RecordCallback)
    {
        // CAUTION: MUST NOT do anything more with rr after calling rr->Callback(), because the client's callback function
        // is allowed to do anything, including starting/stopping queries, registering/deregistering records, etc.
        rr->Acknowledged = mDNStrue;
        mDNS_DropLockBeforeCallback();      // Allow client to legally make mDNS API calls from the callback
        rr->RecordCallback(m, rr, mStatus_NoError);
        mDNS_ReclaimLockAfterCallback();    // Decrement mDNS_reentrancy to block mDNS API calls again
    }
}

mDNSexport void ActivateUnicastRegistration(mDNS *const m, AuthRecord *const rr)
{
    // Make sure that we don't activate the SRV record and associated service records, if it is in
    // NoTarget state. First time when a service is being instantiated, SRV record may be in NoTarget state.
    // We should not activate any of the other reords (PTR, TXT) that are part of the service. When
    // the target becomes available, the records will be reregistered.
    if (rr->resrec.rrtype != kDNSType_SRV)
    {
        AuthRecord *srvRR = mDNSNULL;
        if (rr->resrec.rrtype == kDNSType_PTR)
            srvRR = rr->Additional1;
        else if (rr->resrec.rrtype == kDNSType_TXT)
            srvRR = rr->DependentOn;
        if (srvRR)
        {
            if (srvRR->resrec.rrtype != kDNSType_SRV)
            {
                LogMsg("ActivateUnicastRegistration: ERROR!! Resource record %s wrong, expecting SRV type", ARDisplayString(m, srvRR));
            }
            else
            {
                LogInfo("ActivateUnicastRegistration: Found Service Record %s in state %d for %##s (%s)",
                        ARDisplayString(m, srvRR), srvRR->state, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
                rr->state = srvRR->state;
            }
        }
    }

    if (rr->state == regState_NoTarget)
    {
        LogInfo("ActivateUnicastRegistration record %s in regState_NoTarget, not activating", ARDisplayString(m, rr));
        return;
    }
    // When we wake up from sleep, we call ActivateUnicastRegistration. It is possible that just before we went to sleep,
    // the service/record was being deregistered. In that case, we should not try to register again. For the cases where
    // the records are deregistered due to e.g., no target for the SRV record, we would have returned from above if it
    // was already in NoTarget state. If it was in the process of deregistration but did not complete fully before we went
    // to sleep, then it is okay to start in Pending state as we will go back to NoTarget state if we don't have a target.
    if (rr->resrec.RecordType == kDNSRecordTypeDeregistering)
    {
        LogInfo("ActivateUnicastRegistration: Resource record %s, current state %d, moving to DeregPending", ARDisplayString(m, rr), rr->state);
        rr->state = regState_DeregPending;
    }
    else
    {
        LogInfo("ActivateUnicastRegistration: Resource record %s, current state %d, moving to Pending", ARDisplayString(m, rr), rr->state);
        rr->state = regState_Pending;
    }
    rr->ProbingConflictCount = 0;
    rr->LastConflictPktNum   = 0;
    rr->ProbeRestartCount    = 0;
    rr->ProbeCount           = 0;
    rr->AnnounceCount        = 0;
    rr->ThisAPInterval       = INIT_RECORD_REG_INTERVAL;
    rr->LastAPTime           = m->timenow - rr->ThisAPInterval;
    rr->expire               = 0; // Forget about all the leases, start fresh
    rr->uselease             = mDNStrue;
    rr->updateid             = zeroID;
    rr->SRVChanged           = mDNSfalse;
    rr->updateError          = mStatus_NoError;
    // RestartRecordGetZoneData calls this function whenever a new interface gets registered with core.
    // The records might already be registered with the server and hence could have NAT state.
    if (rr->NATinfo.clientContext)
    {
        mDNS_StopNATOperation_internal(m, &rr->NATinfo);
        rr->NATinfo.clientContext = mDNSNULL;
    }
    if (rr->nta) { CancelGetZoneData(m, rr->nta); rr->nta = mDNSNULL; }
    if (rr->tcp) { DisposeTCPConn(rr->tcp);       rr->tcp = mDNSNULL; }
    if (m->NextuDNSEvent - (rr->LastAPTime + rr->ThisAPInterval) >= 0)
        m->NextuDNSEvent = (rr->LastAPTime + rr->ThisAPInterval);
}

// Two records qualify to be local duplicates if:
// (a) the RecordTypes are the same, or
// (b) one is Unique and the other Verified
// (c) either is in the process of deregistering
#define RecordLDT(A,B) ((A)->resrec.RecordType == (B)->resrec.RecordType || \
                        ((A)->resrec.RecordType | (B)->resrec.RecordType) == (kDNSRecordTypeUnique | kDNSRecordTypeVerified) || \
                        ((A)->resrec.RecordType == kDNSRecordTypeDeregistering || (B)->resrec.RecordType == kDNSRecordTypeDeregistering))

#define RecordIsLocalDuplicate(A,B) \
    ((A)->resrec.InterfaceID == (B)->resrec.InterfaceID && RecordLDT((A),(B)) && IdenticalResourceRecord(& (A)->resrec, & (B)->resrec))

mDNSlocal AuthRecord *CheckAuthIdenticalRecord(AuthHash *r, AuthRecord *rr)
{
    const AuthGroup *a;
    AuthRecord *rp;

    a = AuthGroupForRecord(r, &rr->resrec);
    if (!a) return mDNSNULL;
    rp = a->members;
    while (rp)
    {
        if (!RecordIsLocalDuplicate(rp, rr))
            rp = rp->next;
        else
        {
            if (rp->resrec.RecordType == kDNSRecordTypeDeregistering)
            {
                rp->AnnounceCount = 0;
                rp = rp->next;
            }
            else return rp;
        }
    }
    return (mDNSNULL);
}

mDNSlocal mDNSBool CheckAuthRecordConflict(AuthHash *r, AuthRecord *rr)
{
    const AuthGroup *a;
    const AuthRecord *rp;

    a = AuthGroupForRecord(r, &rr->resrec);
    if (!a) return mDNSfalse;
    rp = a->members;
    while (rp)
    {
        const AuthRecord *s1 = rr->RRSet ? rr->RRSet : rr;
        const AuthRecord *s2 = rp->RRSet ? rp->RRSet : rp;
        if (s1 != s2 && SameResourceRecordSignature(rp, rr) && !IdenticalSameNameRecord(&rp->resrec, &rr->resrec))
            return mDNStrue;
        else
            rp = rp->next;
    }
    return (mDNSfalse);
}

// checks to see if "rr" is already present
mDNSlocal AuthRecord *CheckAuthSameRecord(AuthHash *r, AuthRecord *rr)
{
    const AuthGroup *a;
    AuthRecord *rp;

    a = AuthGroupForRecord(r, &rr->resrec);
    if (!a) return mDNSNULL;
    rp = a->members;
    while (rp)
    {
        if (rp != rr)
            rp = rp->next;
        else
        {
            return rp;
        }
    }
    return (mDNSNULL);
}

mDNSlocal void DecrementAutoTargetServices(mDNS *const m, AuthRecord *const rr)
{
    if (RRLocalOnly(rr))
    {
        // A sanity check, this should be prevented in calling code.
        LogInfo("DecrementAutoTargetServices: called for RRLocalOnly() record: %s", ARDisplayString(m, rr));
        return;
    }

    if (!AuthRecord_uDNS(rr) && (rr->resrec.rrtype == kDNSType_SRV) && (rr->AutoTarget == Target_AutoHost))
    {
        NetworkInterfaceInfo *intf;
#if MDNSRESPONDER_SUPPORTS(APPLE, RANDOM_AWDL_HOSTNAME)
        DeadvertiseFlags flags     = 0; // DeadvertiseFlags for non-AWDL interfaces.
        DeadvertiseFlags flagsAWDL = 0; // DeadvertiseFlags for AWDL interfaces.
        if (AuthRecordIncludesOrIsAWDL(rr))
        {
            if (AuthRecordIncludesAWDL(rr))
            {
                m->AutoTargetAWDLIncludedCount--;
                LogRedact(MDNS_LOG_CATEGORY_DEFAULT, MDNS_LOG_INFO,
                    "DecrementAutoTargetServices: AutoTargetAWDLIncludedCount %u Record " PRI_S,
                    m->AutoTargetAWDLIncludedCount, ARDisplayString(m, rr));
                if (m->AutoTargetAWDLIncludedCount == 0)
                {
                    flags |= kDeadvertiseFlag_RandHostname;
                    if (m->AutoTargetAWDLOnlyCount == 0) flagsAWDL |= kDeadvertiseFlag_RandHostname;
                }
            }
            else
            {
                m->AutoTargetAWDLOnlyCount--;
                LogRedact(MDNS_LOG_CATEGORY_DEFAULT, MDNS_LOG_INFO,
                    "DecrementAutoTargetServices: AutoTargetAWDLOnlyCount %u Record " PRI_S,
                    m->AutoTargetAWDLOnlyCount, ARDisplayString(m, rr));
                if ((m->AutoTargetAWDLIncludedCount == 0) && (m->AutoTargetAWDLOnlyCount == 0))
                {
                    flagsAWDL |= kDeadvertiseFlag_RandHostname;
                }
            }
            if (flags || flagsAWDL)
            {
                for (intf = m->HostInterfaces; intf; intf = intf->next)
                {
                    if (!intf->Advertise) continue;
                    if (mDNSPlatformInterfaceIsAWDL(intf->InterfaceID))
                    {
                        if (flagsAWDL) DeadvertiseInterface(m, intf, flagsAWDL);
                    }
                    else
                    {
                        if (flags) DeadvertiseInterface(m, intf, flags);
                    }
                }
            }
            if ((m->AutoTargetAWDLIncludedCount == 0) && (m->AutoTargetAWDLOnlyCount == 0))
            {
                GetRandomUUIDLocalHostname(&m->RandomizedHostname);
            }
        }
        else
#endif
        {
            m->AutoTargetServices--;
            LogRedact(MDNS_LOG_CATEGORY_DEFAULT, MDNS_LOG_INFO,
                "DecrementAutoTargetServices: AutoTargetServices %u Record " PRI_S,
                m->AutoTargetServices, ARDisplayString(m, rr));
            if (m->AutoTargetServices == 0)
            {
                for (intf = m->HostInterfaces; intf; intf = intf->next)
                {
                    if (intf->Advertise) DeadvertiseInterface(m, intf, kDeadvertiseFlag_NormalHostname);
                }
            }
        }
    }

#if MDNSRESPONDER_SUPPORTS(APPLE, BONJOUR_ON_DEMAND)
    if (!AuthRecord_uDNS(rr))
    {
        if (m->NumAllInterfaceRecords + m->NumAllInterfaceQuestions == 1)
            m->NextBonjourDisableTime = NonZeroTime(m->timenow + (BONJOUR_DISABLE_DELAY * mDNSPlatformOneSecond));
        m->NumAllInterfaceRecords--;
        LogRedact(MDNS_LOG_CATEGORY_DEFAULT, MDNS_LOG_INFO,
            "DecrementAutoTargetServices: NumAllInterfaceRecords %u NumAllInterfaceQuestions %u " PRI_S,
            m->NumAllInterfaceRecords, m->NumAllInterfaceQuestions, ARDisplayString(m, rr));
    }
#endif
}

mDNSlocal void AdvertiseNecessaryInterfaceRecords(mDNS *const m)
{
    NetworkInterfaceInfo *intf;
    for (intf = m->HostInterfaces; intf; intf = intf->next)
    {
        if (intf->Advertise) AdvertiseInterfaceIfNeeded(m, intf);
    }
}

mDNSlocal void IncrementAutoTargetServices(mDNS *const m, AuthRecord *const rr)
{
    mDNSBool enablingBonjour = mDNSfalse;

    if (RRLocalOnly(rr))
    {
        // A sanity check, this should be prevented in calling code.
        LogInfo("IncrementAutoTargetServices: called for RRLocalOnly() record: %s", ARDisplayString(m, rr));
        return;
    }

#if MDNSRESPONDER_SUPPORTS(APPLE, BONJOUR_ON_DEMAND)
    if (!AuthRecord_uDNS(rr))
    {
        m->NumAllInterfaceRecords++;
        LogRedact(MDNS_LOG_CATEGORY_DEFAULT, MDNS_LOG_INFO,
            "IncrementAutoTargetServices: NumAllInterfaceRecords %u NumAllInterfaceQuestions %u " PRI_S,
            m->NumAllInterfaceRecords, m->NumAllInterfaceQuestions, ARDisplayString(m, rr));
        if (m->NumAllInterfaceRecords + m->NumAllInterfaceQuestions == 1)
        {
            m->NextBonjourDisableTime = 0;
            if (m->BonjourEnabled == 0)
            {
                // Enable Bonjour immediately by scheduling network changed processing where
                // we will join the multicast group on each active interface.
                m->BonjourEnabled = 1;
                enablingBonjour = mDNStrue;
                m->NetworkChanged = m->timenow;
            }
        }
    }
#endif

    if (!AuthRecord_uDNS(rr) && (rr->resrec.rrtype == kDNSType_SRV) && (rr->AutoTarget == Target_AutoHost))
    {
#if MDNSRESPONDER_SUPPORTS(APPLE, RANDOM_AWDL_HOSTNAME)
        if (AuthRecordIncludesAWDL(rr))
        {
            m->AutoTargetAWDLIncludedCount++;
            LogRedact(MDNS_LOG_CATEGORY_DEFAULT, MDNS_LOG_INFO,
                "IncrementAutoTargetServices: AutoTargetAWDLIncludedCount %u Record " PRI_S,
                m->AutoTargetAWDLIncludedCount, ARDisplayString(m, rr));
        }
        else if (mDNSPlatformInterfaceIsAWDL(rr->resrec.InterfaceID))
        {
            m->AutoTargetAWDLOnlyCount++;
            LogRedact(MDNS_LOG_CATEGORY_DEFAULT, MDNS_LOG_INFO,
                "IncrementAutoTargetServices: AutoTargetAWDLOnlyCount %u Record " PRI_S,
                m->AutoTargetAWDLOnlyCount, ARDisplayString(m, rr));
        }
        else
#endif
        {
            m->AutoTargetServices++;
            LogRedact(MDNS_LOG_CATEGORY_DEFAULT, MDNS_LOG_INFO,
                "IncrementAutoTargetServices: AutoTargetServices %u Record " PRI_S,
                m->AutoTargetServices, ARDisplayString(m, rr));
        }
        // If this is the first advertised service and we did not just enable Bonjour above, then
        // advertise all the interface records.  If we did enable Bonjour above, the interface records will
        // be advertised during the network changed processing scheduled above, so no need
        // to do it here.
        if (!enablingBonjour) AdvertiseNecessaryInterfaceRecords(m);
    }
}

mDNSlocal void getKeepaliveRaddr(mDNS *const m, AuthRecord *rr, mDNSAddr *raddr)
{
    mDNSAddr     laddr = zeroAddr;
    mDNSEthAddr  eth = zeroEthAddr;
    mDNSIPPort   lport = zeroIPPort;
    mDNSIPPort   rport = zeroIPPort;
    mDNSu32      timeout = 0;
    mDNSu32      seq = 0;
    mDNSu32      ack = 0;
    mDNSu16      win = 0;

    if (mDNS_KeepaliveRecord(&rr->resrec))
    {
        mDNS_ExtractKeepaliveInfo(rr, &timeout, &laddr, raddr, &eth, &seq, &ack, &lport, &rport, &win);
        if (!timeout || mDNSAddressIsZero(&laddr) || mDNSAddressIsZero(raddr) || mDNSIPPortIsZero(lport) || mDNSIPPortIsZero(rport))
        {
            LogMsg("getKeepaliveRaddr: not a valid record %s for keepalive %#a:%d %#a:%d", ARDisplayString(m, rr), &laddr, lport.NotAnInteger, raddr, rport.NotAnInteger);
            return;
        }
    }
}

// Exported so uDNS.c can call this
mDNSexport mStatus mDNS_Register_internal(mDNS *const m, AuthRecord *const rr)
{
    domainname *target = GetRRDomainNameTarget(&rr->resrec);
    AuthRecord *r;
    AuthRecord **p = &m->ResourceRecords;
    AuthRecord **d = &m->DuplicateRecords;

    if ((mDNSs32)rr->resrec.rroriginalttl <= 0)
    { LogMsg("mDNS_Register_internal: TTL %X should be 1 - 0x7FFFFFFF %s", rr->resrec.rroriginalttl, ARDisplayString(m, rr)); return(mStatus_BadParamErr); }

    if (!rr->resrec.RecordType)
    { LogMsg("mDNS_Register_internal: RecordType must be non-zero %s", ARDisplayString(m, rr)); return(mStatus_BadParamErr); }

    if (m->ShutdownTime)
    { LogMsg("mDNS_Register_internal: Shutting down, can't register %s", ARDisplayString(m, rr)); return(mStatus_ServiceNotRunning); }

    if (m->DivertMulticastAdvertisements && !AuthRecord_uDNS(rr))
    {
        mDNSInterfaceID previousID = rr->resrec.InterfaceID;
        if (rr->resrec.InterfaceID == mDNSInterface_Any || rr->resrec.InterfaceID == mDNSInterface_P2P)
        {
            rr->resrec.InterfaceID = mDNSInterface_LocalOnly;
            rr->ARType = AuthRecordLocalOnly;
        }
        if (rr->resrec.InterfaceID != mDNSInterface_LocalOnly)
        {
            NetworkInterfaceInfo *intf = FirstInterfaceForID(m, rr->resrec.InterfaceID);
            if (intf && !intf->Advertise) { rr->resrec.InterfaceID = mDNSInterface_LocalOnly; rr->ARType = AuthRecordLocalOnly; }
        }
        if (rr->resrec.InterfaceID != previousID)
            LogInfo("mDNS_Register_internal: Diverting record to local-only %s", ARDisplayString(m, rr));
    }

    if (RRLocalOnly(rr))
    {
        if (CheckAuthSameRecord(&m->rrauth, rr))
        {
            LogMsg("mDNS_Register_internal: ERROR!! Tried to register LocalOnly AuthRecord %p %##s (%s) that's already in the list",
                   rr, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
            return(mStatus_AlreadyRegistered);
        }
    }
    else
    {
        while (*p && *p != rr) p=&(*p)->next;
        if (*p)
        {
            LogMsg("mDNS_Register_internal: ERROR!! Tried to register AuthRecord %p %##s (%s) that's already in the list",
                   rr, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
            return(mStatus_AlreadyRegistered);
        }
    }

    while (*d && *d != rr) d=&(*d)->next;
    if (*d)
    {
        LogMsg("mDNS_Register_internal: ERROR!! Tried to register AuthRecord %p %##s (%s) that's already in the Duplicate list",
               rr, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
        return(mStatus_AlreadyRegistered);
    }

    if (rr->DependentOn)
    {
        if (rr->resrec.RecordType == kDNSRecordTypeUnique)
            rr->resrec.RecordType =  kDNSRecordTypeVerified;
        else if (rr->resrec.RecordType != kDNSRecordTypeKnownUnique)
        {
            LogMsg("mDNS_Register_internal: ERROR! %##s (%s): rr->DependentOn && RecordType != kDNSRecordTypeUnique or kDNSRecordTypeKnownUnique",
                   rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
            return(mStatus_Invalid);
        }
        if (!(rr->DependentOn->resrec.RecordType & (kDNSRecordTypeUnique | kDNSRecordTypeVerified | kDNSRecordTypeKnownUnique)))
        {
            LogMsg("mDNS_Register_internal: ERROR! %##s (%s): rr->DependentOn->RecordType bad type %X",
                   rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype), rr->DependentOn->resrec.RecordType);
            return(mStatus_Invalid);
        }
    }

    rr->next = mDNSNULL;

    // Field Group 1: The actual information pertaining to this resource record
    // Set up by client prior to call

    // Field Group 2: Persistent metadata for Authoritative Records
//  rr->Additional1       = set to mDNSNULL  in mDNS_SetupResourceRecord; may be overridden by client
//  rr->Additional2       = set to mDNSNULL  in mDNS_SetupResourceRecord; may be overridden by client
//  rr->DependentOn       = set to mDNSNULL  in mDNS_SetupResourceRecord; may be overridden by client
//  rr->RRSet             = set to mDNSNULL  in mDNS_SetupResourceRecord; may be overridden by client
//  rr->Callback          = already set      in mDNS_SetupResourceRecord
//  rr->Context           = already set      in mDNS_SetupResourceRecord
//  rr->RecordType        = already set      in mDNS_SetupResourceRecord
//  rr->HostTarget        = set to mDNSfalse in mDNS_SetupResourceRecord; may be overridden by client
//  rr->AllowRemoteQuery  = set to mDNSfalse in mDNS_SetupResourceRecord; may be overridden by client
    // Make sure target is not uninitialized data, or we may crash writing debugging log messages
    if (rr->AutoTarget && target) target->c[0] = 0;

    // Field Group 3: Transient state for Authoritative Records
    rr->Acknowledged      = mDNSfalse;
    rr->ProbeCount        = DefaultProbeCountForRecordType(rr->resrec.RecordType);
    rr->ProbeRestartCount = 0;
    rr->AnnounceCount     = InitialAnnounceCount;
    rr->RequireGoodbye    = mDNSfalse;
    rr->AnsweredLocalQ    = mDNSfalse;
    rr->IncludeInProbe    = mDNSfalse;
    rr->ImmedUnicast      = mDNSfalse;
    rr->SendNSECNow       = mDNSNULL;
    rr->ImmedAnswer       = mDNSNULL;
    rr->ImmedAdditional   = mDNSNULL;
    rr->SendRNow          = mDNSNULL;
    rr->v4Requester       = zerov4Addr;
    rr->v6Requester       = zerov6Addr;
    rr->NextResponse      = mDNSNULL;
    rr->NR_AnswerTo       = mDNSNULL;
    rr->NR_AdditionalTo   = mDNSNULL;
    if (!rr->AutoTarget) InitializeLastAPTime(m, rr);
//  rr->LastAPTime        = Set for us in InitializeLastAPTime()
//  rr->LastMCTime        = Set for us in InitializeLastAPTime()
//  rr->LastMCInterface   = Set for us in InitializeLastAPTime()
    rr->NewRData          = mDNSNULL;
    rr->newrdlength       = 0;
    rr->UpdateCallback    = mDNSNULL;
    rr->UpdateCredits     = kMaxUpdateCredits;
    rr->NextUpdateCredit  = 0;
    rr->UpdateBlocked     = 0;

    // For records we're holding as proxy (except reverse-mapping PTR records) two announcements is sufficient
    if (rr->WakeUp.HMAC.l[0] && !rr->AddressProxy.type) rr->AnnounceCount = 2;

    // Field Group 4: Transient uDNS state for Authoritative Records
    rr->state             = regState_Zero;
    rr->uselease          = 0;
    rr->expire            = 0;
    rr->Private           = 0;
    rr->updateid          = zeroID;
    rr->updateIntID       = zeroOpaque64;
    rr->zone              = rr->resrec.name;
    rr->nta               = mDNSNULL;
    rr->tcp               = mDNSNULL;
    rr->OrigRData         = 0;
    rr->OrigRDLen         = 0;
    rr->InFlightRData     = 0;
    rr->InFlightRDLen     = 0;
    rr->QueuedRData       = 0;
    rr->QueuedRDLen       = 0;
    //mDNSPlatformMemZero(&rr->NATinfo, sizeof(rr->NATinfo));
    // We should be recording the actual internal port for this service record here. Once we initiate our NAT mapping
    // request we'll subsequently overwrite srv.port with the allocated external NAT port -- potentially multiple
    // times with different values if the external NAT port changes during the lifetime of the service registration.
    //if (rr->resrec.rrtype == kDNSType_SRV) rr->NATinfo.IntPort = rr->resrec.rdata->u.srv.port;

//  rr->resrec.interface         = already set in mDNS_SetupResourceRecord
//  rr->resrec.name->c           = MUST be set by client
//  rr->resrec.rrtype            = already set in mDNS_SetupResourceRecord
//  rr->resrec.rrclass           = already set in mDNS_SetupResourceRecord
//  rr->resrec.rroriginalttl     = already set in mDNS_SetupResourceRecord
//  rr->resrec.rdata             = MUST be set by client, unless record type is CNAME or PTR and rr->HostTarget is set

    // BIND named (name daemon) doesn't allow TXT records with zero-length rdata. This is strictly speaking correct,
    // since RFC 1035 specifies a TXT record as "One or more <character-string>s", not "Zero or more <character-string>s".
    // Since some legacy apps try to create zero-length TXT records, we'll silently correct it here.
    if (rr->resrec.rrtype == kDNSType_TXT && rr->resrec.rdlength == 0) { rr->resrec.rdlength = 1; rr->resrec.rdata->u.txt.c[0] = 0; }

    if (rr->AutoTarget)
    {
        SetTargetToHostName(m, rr); // Also sets rdlength and rdestimate for us, and calls InitializeLastAPTime();
#ifndef UNICAST_DISABLED
        // If we have no target record yet, SetTargetToHostName will set rr->state == regState_NoTarget
        // In this case we leave the record half-formed in the list, and later we'll remove it from the list and re-add it properly.
        if (rr->state == regState_NoTarget)
        {
            // Initialize the target so that we don't crash while logging etc.
            domainname *tar = GetRRDomainNameTarget(&rr->resrec);
            if (tar) tar->c[0] = 0;
            LogInfo("mDNS_Register_internal: record %s in NoTarget state", ARDisplayString(m, rr));
        }
#endif
    }
    else
    {
        rr->resrec.rdlength   = GetRDLength(&rr->resrec, mDNSfalse);
        rr->resrec.rdestimate = GetRDLength(&rr->resrec, mDNStrue);
    }

    if (!ValidateDomainName(rr->resrec.name))
    { LogMsg("Attempt to register record with invalid name: %s", ARDisplayString(m, rr)); return(mStatus_Invalid); }

    // Don't do this until *after* we've set rr->resrec.rdlength
    if (!ValidateRData(rr->resrec.rrtype, rr->resrec.rdlength, rr->resrec.rdata))
    { LogMsg("Attempt to register record with invalid rdata: %s", ARDisplayString(m, rr)); return(mStatus_Invalid); }

    rr->resrec.namehash   = DomainNameHashValue(rr->resrec.name);
    rr->resrec.rdatahash  = target ? DomainNameHashValue(target) : RDataHashValue(&rr->resrec);

    if (RRLocalOnly(rr))
    {
        // If this is supposed to be unique, make sure we don't have any name conflicts.
        // If we found a conflict, we may still want to insert the record in the list but mark it appropriately
        // (kDNSRecordTypeDeregistering) so that we deliver RMV events to the application. But this causes more
        // complications and not clear whether there are any benefits. See rdar:9304275 for details.
        // Hence, just bail out.
        // This comment is doesn’t make any sense. -- SC
        if (rr->resrec.RecordType & kDNSRecordTypeUniqueMask)
        {
            if (CheckAuthRecordConflict(&m->rrauth, rr))
            {
                LogInfo("mDNS_Register_internal: Name conflict %s (%p), InterfaceID %p", ARDisplayString(m, rr), rr, rr->resrec.InterfaceID);
                return mStatus_NameConflict;
            }
        }
    }

    // For uDNS records, we don't support duplicate checks at this time.
#ifndef UNICAST_DISABLED
    if (AuthRecord_uDNS(rr))
    {
        if (!m->NewLocalRecords) m->NewLocalRecords = rr;
        // When we called SetTargetToHostName, it may have caused mDNS_Register_internal to be re-entered, appending new
        // records to the list, so we now need to update p to advance to the new end to the list before appending our new record.
        while (*p) p=&(*p)->next;
        *p = rr;
        if (rr->resrec.RecordType == kDNSRecordTypeUnique) rr->resrec.RecordType = kDNSRecordTypeVerified;
        rr->ProbeCount    = 0;
        rr->ProbeRestartCount = 0;
        rr->AnnounceCount = 0;
        if (rr->state != regState_NoTarget) ActivateUnicastRegistration(m, rr);
        return(mStatus_NoError);            // <--- Note: For unicast records, code currently bails out at this point
    }
#endif

    // Now that we've finished building our new record, make sure it's not identical to one we already have
    if (RRLocalOnly(rr))
    {
        rr->ProbeCount    = 0;
        rr->ProbeRestartCount = 0;
        rr->AnnounceCount = 0;
        r = CheckAuthIdenticalRecord(&m->rrauth, rr);
    }
    else
    {
        for (r = m->ResourceRecords; r; r=r->next)
            if (RecordIsLocalDuplicate(r, rr))
            {
                if (r->resrec.RecordType == kDNSRecordTypeDeregistering) r->AnnounceCount = 0;
                else break;
            }
    }

    if (r)
    {
        LogInfo("mDNS_Register_internal: Adding to duplicate list %s", ARDisplayString(m,rr));
        *d = rr;
        // If the previous copy of this record is already verified unique,
        // then indicate that we should move this record promptly to kDNSRecordTypeUnique state.
        // Setting ProbeCount to zero will cause SendQueries() to advance this record to
        // kDNSRecordTypeVerified state and call the client callback at the next appropriate time.
        if (rr->resrec.RecordType == kDNSRecordTypeUnique && r->resrec.RecordType == kDNSRecordTypeVerified)
            rr->ProbeCount = 0;
    }
    else
    {
        LogInfo("mDNS_Register_internal: Adding to active record list %s", ARDisplayString(m,rr));
        if (RRLocalOnly(rr))
        {
            AuthGroup *ag;
            ag = InsertAuthRecord(m, &m->rrauth, rr);
            if (ag && !ag->NewLocalOnlyRecords)
            {
                m->NewLocalOnlyRecords = mDNStrue;
                ag->NewLocalOnlyRecords = rr;
            }
            // No probing for LocalOnly records; acknowledge them right away
            if (rr->resrec.RecordType == kDNSRecordTypeUnique) rr->resrec.RecordType = kDNSRecordTypeVerified;
            AcknowledgeRecord(m, rr);
            return(mStatus_NoError);
        }
        else
        {
            if (!m->NewLocalRecords) m->NewLocalRecords = rr;
            *p = rr;
        }
    }

    if (!AuthRecord_uDNS(rr))   // This check is superfluous, given that for unicast records we (currently) bail out above
    {
        // We have inserted the record in the list. See if we have to advertise the A/AAAA, HINFO, PTR records.
        IncrementAutoTargetServices(m, rr);

        // For records that are not going to probe, acknowledge them right away
        if (rr->resrec.RecordType != kDNSRecordTypeUnique && rr->resrec.RecordType != kDNSRecordTypeDeregistering)
            AcknowledgeRecord(m, rr);

        // Adding a record may affect whether or not we should sleep
        mDNS_UpdateAllowSleep(m);
    }

    // If this is a non-sleep proxy keepalive record, fetch the MAC address of the remote host.
    // This is used by the in-NIC proxy to send the keepalive packets.
    if (!rr->WakeUp.HMAC.l[0] && mDNS_KeepaliveRecord(&rr->resrec))
    {
        mDNSAddr raddr;
        // Set the record type to known unique to prevent probing keep alive records.
        // Also make sure we do not announce the keepalive records.
       rr->resrec.RecordType = kDNSRecordTypeKnownUnique;
       rr->AnnounceCount     = 0;
       getKeepaliveRaddr(m, rr, &raddr);
       // This is an asynchronous call. Once the remote MAC address is available, helper will schedule an
       // asynchronous task to update the resource record
       mDNSPlatformGetRemoteMacAddr(&raddr);
    }

    return(mStatus_NoError);
}

mDNSlocal void RecordProbeFailure(mDNS *const m, const AuthRecord *const rr)
{
    m->ProbeFailTime = m->timenow;
    m->NumFailedProbes++;
    // If we've had fifteen or more probe failures, rate-limit to one every five seconds.
    // If a bunch of hosts have all been configured with the same name, then they'll all
    // conflict and run through the same series of names: name-2, name-3, name-4, etc.,
    // up to name-10. After that they'll start adding random increments in the range 1-100,
    // so they're more likely to branch out in the available namespace and settle on a set of
    // unique names quickly. If after five more tries the host is still conflicting, then we
    // may have a serious problem, so we start rate-limiting so we don't melt down the network.
    if (m->NumFailedProbes >= 15)
    {
        m->SuppressProbes = NonZeroTime(m->timenow + mDNSPlatformOneSecond * 5);
        LogMsg("Excessive name conflicts (%lu) for %##s (%s); rate limiting in effect",
               m->NumFailedProbes, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
    }
}

mDNSlocal void CompleteRDataUpdate(mDNS *const m, AuthRecord *const rr)
{
    RData *OldRData = rr->resrec.rdata;
    mDNSu16 OldRDLen = rr->resrec.rdlength;
    SetNewRData(&rr->resrec, rr->NewRData, rr->newrdlength);    // Update our rdata
    rr->NewRData = mDNSNULL;                                    // Clear the NewRData pointer ...
    if (rr->UpdateCallback)
        rr->UpdateCallback(m, rr, OldRData, OldRDLen);          // ... and let the client know
}

// Note: mDNS_Deregister_internal can call a user callback, which may change the record list and/or question list.
// Any code walking either list must use the CurrentQuestion and/or CurrentRecord mechanism to protect against this.
// Exported so uDNS.c can call this
mDNSexport mStatus mDNS_Deregister_internal(mDNS *const m, AuthRecord *const rr, mDNS_Dereg_type drt)
{
    AuthRecord *r2;
    mDNSu8 RecordType = rr->resrec.RecordType;
    AuthRecord **p = &m->ResourceRecords;   // Find this record in our list of active records
    mDNSBool dupList = mDNSfalse;

    if (RRLocalOnly(rr))
    {
        AuthGroup *a;
        AuthRecord **rp;

        a = AuthGroupForRecord(&m->rrauth, &rr->resrec);
        if (!a) return mDNSfalse;
        rp = &a->members;
        while (*rp && *rp != rr) rp=&(*rp)->next;
        p = rp;
    }
    else
    {
        while (*p && *p != rr) p=&(*p)->next;
    }

    if (*p)
    {
        // We found our record on the main list. See if there are any duplicates that need special handling.
        if (drt == mDNS_Dereg_conflict)     // If this was a conflict, see that all duplicates get the same treatment
        {
            // Scan for duplicates of rr, and mark them for deregistration at the end of this routine, after we've finished
            // deregistering rr. We need to do this scan *before* we give the client the chance to free and reuse the rr memory.
            for (r2 = m->DuplicateRecords; r2; r2=r2->next) if (RecordIsLocalDuplicate(r2, rr)) r2->ProbeCount = 0xFF;
        }
        else
        {
            // Before we delete the record (and potentially send a goodbye packet)
            // first see if we have a record on the duplicate list ready to take over from it.
            AuthRecord **d = &m->DuplicateRecords;
            while (*d && !RecordIsLocalDuplicate(*d, rr)) d=&(*d)->next;
            if (*d)
            {
                AuthRecord *dup = *d;
                debugf("mDNS_Register_internal: Duplicate record %p taking over from %p %##s (%s)",
                       dup, rr, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
                *d        = dup->next;      // Cut replacement record from DuplicateRecords list
                if (RRLocalOnly(rr))
                {
                    dup->next = mDNSNULL;
                    if (!InsertAuthRecord(m, &m->rrauth, dup)) LogMsg("mDNS_Deregister_internal: ERROR!! cannot insert %s", ARDisplayString(m, dup));
                }
                else
                {
                    dup->next = rr->next;       // And then...
                    rr->next  = dup;            // ... splice it in right after the record we're about to delete
                }
                dup->resrec.RecordType        = rr->resrec.RecordType;
                dup->ProbeCount      = rr->ProbeCount;
                dup->ProbeRestartCount = rr->ProbeRestartCount;
                dup->AnnounceCount   = rr->AnnounceCount;
                dup->RequireGoodbye  = rr->RequireGoodbye;
                dup->AnsweredLocalQ  = rr->AnsweredLocalQ;
                dup->ImmedAnswer     = rr->ImmedAnswer;
                dup->ImmedUnicast    = rr->ImmedUnicast;
                dup->ImmedAdditional = rr->ImmedAdditional;
                dup->v4Requester     = rr->v4Requester;
                dup->v6Requester     = rr->v6Requester;
                dup->ThisAPInterval  = rr->ThisAPInterval;
                dup->LastAPTime      = rr->LastAPTime;
                dup->LastMCTime      = rr->LastMCTime;
                dup->LastMCInterface = rr->LastMCInterface;
                dup->Private         = rr->Private;
                dup->state           = rr->state;
                rr->RequireGoodbye = mDNSfalse;
                rr->AnsweredLocalQ = mDNSfalse;
            }
        }
    }
    else
    {
        // We didn't find our record on the main list; try the DuplicateRecords list instead.
        p = &m->DuplicateRecords;
        while (*p && *p != rr) p=&(*p)->next;
        // If we found our record on the duplicate list, then make sure we don't send a goodbye for it
        if (*p)
        {
            // Duplicate records are not used for sending wakeups or goodbyes. Hence, deregister them
            // immediately. When there is a conflict, we deregister all the conflicting duplicate records
            // also that have been marked above in this function. In that case, we come here and if we don't
            // deregister (unilink from the DuplicateRecords list), we will be recursing infinitely. Hence,
            // clear the HMAC which will cause it to deregister. See <rdar://problem/10380988> for
            // details.
            rr->WakeUp.HMAC    = zeroEthAddr;
            rr->RequireGoodbye = mDNSfalse;
            rr->resrec.RecordType = kDNSRecordTypeDeregistering;
            dupList = mDNStrue;
        }
        if (*p) debugf("mDNS_Deregister_internal: Deleting DuplicateRecord %p %##s (%s)",
                       rr, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
    }

    if (!*p)
    {
        // No need to log an error message if we already know this is a potentially repeated deregistration
        if (drt != mDNS_Dereg_repeat)
            LogMsg("mDNS_Deregister_internal: Record %p not found in list %s", rr, ARDisplayString(m,rr));
        return(mStatus_BadReferenceErr);
    }

    // If this is a shared record and we've announced it at least once,
    // we need to retract that announcement before we delete the record

    // If this is a record (including mDNSInterface_LocalOnly records) for which we've given local-only answers then
    // it's tempting to just do "AnswerAllLocalQuestionsWithLocalAuthRecord(m, rr, QC_rmv)" here, but that would not not be safe.
    // The AnswerAllLocalQuestionsWithLocalAuthRecord routine walks the question list invoking client callbacks, using the "m->CurrentQuestion"
    // mechanism to cope with the client callback modifying the question list while that's happening.
    // However, mDNS_Deregister could have been called from a client callback (e.g. from the domain enumeration callback FoundDomain)
    // which means that the "m->CurrentQuestion" mechanism is already in use to protect that list, so we can't use it twice.
    // More generally, if we invoke callbacks from within a client callback, then those callbacks could deregister other
    // records, thereby invoking yet more callbacks, without limit.
    // The solution is to defer delivering the "Remove" events until mDNS_Execute time, just like we do for sending
    // actual goodbye packets.

#ifndef UNICAST_DISABLED
    if (AuthRecord_uDNS(rr))
    {
        if (rr->RequireGoodbye)
        {
            if (rr->tcp) { DisposeTCPConn(rr->tcp); rr->tcp = mDNSNULL; }
            rr->resrec.RecordType    = kDNSRecordTypeDeregistering;
            m->LocalRemoveEvents     = mDNStrue;
            uDNS_DeregisterRecord(m, rr);
            // At this point unconditionally we bail out
            // Either uDNS_DeregisterRecord will have completed synchronously, and called CompleteDeregistration,
            // which calls us back here with RequireGoodbye set to false, or it will have initiated the deregistration
            // process and will complete asynchronously. Either way we don't need to do anything more here.
            return(mStatus_NoError);
        }
        // Sometimes the records don't complete proper deregistration i.e., don't wait for a response
        // from the server. In that case, if the records have been part of a group update, clear the
        // state here.
        rr->updateid = zeroID;

        // We defer cleaning up NAT state only after sending goodbyes. This is important because
        // RecordRegistrationGotZoneData guards against creating NAT state if clientContext is non-NULL.
        // This happens today when we turn on/off interface where we get multiple network transitions
        // and RestartRecordGetZoneData triggers re-registration of the resource records even though
        // they may be in Registered state which causes NAT information to be setup multiple times. Defering
        // the cleanup here keeps clientContext non-NULL and hence prevents that. Note that cleaning up
        // NAT state here takes care of the case where we did not send goodbyes at all.
        if (rr->NATinfo.clientContext)
        {
            mDNS_StopNATOperation_internal(m, &rr->NATinfo);
            rr->NATinfo.clientContext = mDNSNULL;
        }
        if (rr->nta) { CancelGetZoneData(m, rr->nta); rr->nta = mDNSNULL; }
        if (rr->tcp) { DisposeTCPConn(rr->tcp);       rr->tcp = mDNSNULL; }
    }
#endif // UNICAST_DISABLED

    if      (RecordType == kDNSRecordTypeUnregistered)
        LogMsg("mDNS_Deregister_internal: %s already marked kDNSRecordTypeUnregistered", ARDisplayString(m, rr));
    else if (RecordType == kDNSRecordTypeDeregistering)
    {
        LogMsg("mDNS_Deregister_internal: %s already marked kDNSRecordTypeDeregistering", ARDisplayString(m, rr));
        return(mStatus_BadReferenceErr);
    }

    if (rr->WakeUp.HMAC.l[0] ||
        (((RecordType == kDNSRecordTypeShared) || (rr->ARType == AuthRecordLocalOnly)) &&
        (rr->RequireGoodbye || rr->AnsweredLocalQ)))
    {
        verbosedebugf("mDNS_Deregister_internal: Starting deregistration for %s", ARDisplayString(m, rr));
        rr->resrec.RecordType    = kDNSRecordTypeDeregistering;
        rr->resrec.rroriginalttl = 0;
        rr->AnnounceCount        = rr->WakeUp.HMAC.l[0] ? WakeupCount : (drt == mDNS_Dereg_rapid) ? 1 : GoodbyeCount;
        rr->ThisAPInterval       = mDNSPlatformOneSecond * 2;
        rr->LastAPTime           = m->timenow - rr->ThisAPInterval;
        m->LocalRemoveEvents     = mDNStrue;
        if (m->NextScheduledResponse - (m->timenow + mDNSPlatformOneSecond/10) >= 0)
            m->NextScheduledResponse = (m->timenow + mDNSPlatformOneSecond/10);
    }
    else
    {
        if (!dupList && RRLocalOnly(rr))
        {
            AuthGroup *ag = RemoveAuthRecord(m, &m->rrauth, rr);
            if (ag->NewLocalOnlyRecords == rr) ag->NewLocalOnlyRecords = rr->next;
        }
        else
        {
            *p = rr->next;                  // Cut this record from the list
            if (m->NewLocalRecords == rr) m->NewLocalRecords = rr->next;
            DecrementAutoTargetServices(m, rr);
        }
        // If someone is about to look at this, bump the pointer forward
        if (m->CurrentRecord   == rr) m->CurrentRecord   = rr->next;
        rr->next = mDNSNULL;

        verbosedebugf("mDNS_Deregister_internal: Deleting record for %s", ARDisplayString(m, rr));
        rr->resrec.RecordType = kDNSRecordTypeUnregistered;

        if ((drt == mDNS_Dereg_conflict || drt == mDNS_Dereg_repeat) && RecordType == kDNSRecordTypeShared)
            debugf("mDNS_Deregister_internal: Cannot have a conflict on a shared record! %##s (%s)",
                   rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));

        // If we have an update queued up which never executed, give the client a chance to free that memory
        if (rr->NewRData) CompleteRDataUpdate(m, rr);   // Update our rdata, clear the NewRData pointer, and return memory to the client


        // CAUTION: MUST NOT do anything more with rr after calling rr->Callback(), because the client's callback function
        // is allowed to do anything, including starting/stopping queries, registering/deregistering records, etc.
        // In this case the likely client action to the mStatus_MemFree message is to free the memory,
        // so any attempt to touch rr after this is likely to lead to a crash.
        if (drt != mDNS_Dereg_conflict)
        {
            mDNS_DropLockBeforeCallback();      // Allow client to legally make mDNS API calls from the callback
            LogInfo("mDNS_Deregister_internal: callback with mStatus_MemFree for %s", ARDisplayString(m, rr));
            if (rr->RecordCallback)
                rr->RecordCallback(m, rr, mStatus_MemFree);         // MUST NOT touch rr after this
            mDNS_ReclaimLockAfterCallback();    // Decrement mDNS_reentrancy to block mDNS API calls again
        }
        else
        {
            RecordProbeFailure(m, rr);
            mDNS_DropLockBeforeCallback();      // Allow client to legally make mDNS API calls from the callback
            if (rr->RecordCallback)
                rr->RecordCallback(m, rr, mStatus_NameConflict);    // MUST NOT touch rr after this
            mDNS_ReclaimLockAfterCallback();    // Decrement mDNS_reentrancy to block mDNS API calls again
            // Now that we've finished deregistering rr, check our DuplicateRecords list for any that we marked previously.
            // Note that with all the client callbacks going on, by the time we get here all the
            // records we marked may have been explicitly deregistered by the client anyway.
            r2 = m->DuplicateRecords;
            while (r2)
            {
                if (r2->ProbeCount != 0xFF)
                {
                    r2 = r2->next;
                }
                else
                {
#if MDNSRESPONDER_SUPPORTS(APPLE, D2D)
                    // See if this record was also registered with any D2D plugins.
                    D2D_stop_advertising_record(r2);
#endif
                    mDNS_Deregister_internal(m, r2, mDNS_Dereg_conflict);
                    // As this is a duplicate record, it will be unlinked from the list
                    // immediately
                    r2 = m->DuplicateRecords;
                }
            }
        }
    }
    mDNS_UpdateAllowSleep(m);
    return(mStatus_NoError);
}

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark -
#pragma mark - Packet Sending Functions
#endif

mDNSlocal void AddRecordToResponseList(AuthRecord ***nrpp, AuthRecord *rr, AuthRecord *add)
{
    if (rr->NextResponse == mDNSNULL && *nrpp != &rr->NextResponse)
    {
        **nrpp = rr;
        // NR_AdditionalTo must point to a record with NR_AnswerTo set (and not NR_AdditionalTo)
        // If 'add' does not meet this requirement, then follow its NR_AdditionalTo pointer to a record that does
        // The referenced record will definitely be acceptable (by recursive application of this rule)
        if (add && add->NR_AdditionalTo) add = add->NR_AdditionalTo;
        rr->NR_AdditionalTo = add;
        *nrpp = &rr->NextResponse;
    }
    debugf("AddRecordToResponseList: %##s (%s) already in list", rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
}

mDNSlocal void AddRRSetAdditionalsToResponseList(mDNS *const m, AuthRecord ***nrpp, AuthRecord *rr, AuthRecord *additional, const mDNSInterfaceID InterfaceID)
{
    AuthRecord *rr2;
    if (additional->resrec.RecordType & kDNSRecordTypeUniqueMask)
    {
        for (rr2 = m->ResourceRecords; rr2; rr2 = rr2->next)
        {
            if ((rr2->resrec.namehash == additional->resrec.namehash) &&
                (rr2->resrec.rrtype   == additional->resrec.rrtype) &&
                (rr2 != additional) &&
                (rr2->resrec.RecordType & kDNSRecordTypeUniqueMask) &&
                (rr2->resrec.rrclass  == additional->resrec.rrclass) &&
                ResourceRecordIsValidInterfaceAnswer(rr2, InterfaceID) &&
                SameDomainName(rr2->resrec.name, additional->resrec.name))
            {
                AddRecordToResponseList(nrpp, rr2, rr);
            }
        }
    }
}

mDNSlocal void AddAdditionalsToResponseList(mDNS *const m, AuthRecord *ResponseRecords, AuthRecord ***nrpp, const mDNSInterfaceID InterfaceID)
{
    AuthRecord  *rr, *rr2;
    for (rr=ResponseRecords; rr; rr=rr->NextResponse)           // For each record we plan to put
    {
        // (Note: This is an "if", not a "while". If we add a record, we'll find it again
        // later in the "for" loop, and we will follow further "additional" links then.)
        if (rr->Additional1 && ResourceRecordIsValidInterfaceAnswer(rr->Additional1, InterfaceID))
        {
            AddRecordToResponseList(nrpp, rr->Additional1, rr);
            AddRRSetAdditionalsToResponseList(m, nrpp, rr, rr->Additional1, InterfaceID);
        }

        if (rr->Additional2 && ResourceRecordIsValidInterfaceAnswer(rr->Additional2, InterfaceID))
        {
            AddRecordToResponseList(nrpp, rr->Additional2, rr);
            AddRRSetAdditionalsToResponseList(m, nrpp, rr, rr->Additional2, InterfaceID);
        }

        // For SRV records, automatically add the Address record(s) for the target host
        if (rr->resrec.rrtype == kDNSType_SRV)
        {
            for (rr2=m->ResourceRecords; rr2; rr2=rr2->next)                    // Scan list of resource records
                if (RRTypeIsAddressType(rr2->resrec.rrtype) &&                  // For all address records (A/AAAA) ...
                    ResourceRecordIsValidInterfaceAnswer(rr2, InterfaceID) &&   // ... which are valid for answer ...
                    rr->resrec.rdatahash == rr2->resrec.namehash &&         // ... whose name is the name of the SRV target
                    SameDomainName(&rr->resrec.rdata->u.srv.target, rr2->resrec.name))
                    AddRecordToResponseList(nrpp, rr2, rr);
        }
        else if (RRTypeIsAddressType(rr->resrec.rrtype))    // For A or AAAA, put counterpart as additional
        {
            for (rr2=m->ResourceRecords; rr2; rr2=rr2->next)                    // Scan list of resource records
                if (RRTypeIsAddressType(rr2->resrec.rrtype) &&                  // For all address records (A/AAAA) ...
                    ResourceRecordIsValidInterfaceAnswer(rr2, InterfaceID) &&   // ... which are valid for answer ...
                    rr->resrec.namehash == rr2->resrec.namehash &&              // ... and have the same name
                    SameDomainName(rr->resrec.name, rr2->resrec.name))
                    AddRecordToResponseList(nrpp, rr2, rr);
        }
        else if (rr->resrec.rrtype == kDNSType_PTR)         // For service PTR, see if we want to add DeviceInfo record
        {
            if (ResourceRecordIsValidInterfaceAnswer(&m->DeviceInfo, InterfaceID) &&
                SameDomainLabel(rr->resrec.rdata->u.name.c, m->DeviceInfo.resrec.name->c))
                AddRecordToResponseList(nrpp, &m->DeviceInfo, rr);
        }
    }
}

mDNSlocal void SendDelayedUnicastResponse(mDNS *const m, const mDNSAddr *const dest, const mDNSInterfaceID InterfaceID)
{
    AuthRecord *rr;
    AuthRecord  *ResponseRecords = mDNSNULL;
    AuthRecord **nrp             = &ResponseRecords;
    NetworkInterfaceInfo *intf = FirstInterfaceForID(m, InterfaceID);

    // Make a list of all our records that need to be unicast to this destination
    for (rr = m->ResourceRecords; rr; rr=rr->next)
    {
        // If we find we can no longer unicast this answer, clear ImmedUnicast
        if (rr->ImmedAnswer == mDNSInterfaceMark               ||
            mDNSSameIPv4Address(rr->v4Requester, onesIPv4Addr) ||
            mDNSSameIPv6Address(rr->v6Requester, onesIPv6Addr)  )
            rr->ImmedUnicast = mDNSfalse;

        if (rr->ImmedUnicast && rr->ImmedAnswer == InterfaceID)
        {
            if ((dest->type == mDNSAddrType_IPv4 && mDNSSameIPv4Address(rr->v4Requester, dest->ip.v4)) ||
                (dest->type == mDNSAddrType_IPv6 && mDNSSameIPv6Address(rr->v6Requester, dest->ip.v6)))
            {
                rr->ImmedAnswer  = mDNSNULL;                // Clear the state fields
                rr->ImmedUnicast = mDNSfalse;
                rr->v4Requester  = zerov4Addr;
                rr->v6Requester  = zerov6Addr;

                // Only sent records registered for P2P over P2P interfaces
                if (intf && !mDNSPlatformValidRecordForInterface(rr, intf->InterfaceID))
                {
                    continue;
                }

                if (rr->NextResponse == mDNSNULL && nrp != &rr->NextResponse)   // rr->NR_AnswerTo
                {
                    rr->NR_AnswerTo = NR_AnswerMulticast;
                    *nrp = rr;
                    nrp = &rr->NextResponse;
                }
            }
        }
    }

    AddAdditionalsToResponseList(m, ResponseRecords, &nrp, InterfaceID);

    while (ResponseRecords)
    {
        mDNSu8 *responseptr = m->omsg.data;
        mDNSu8 *newptr;
        InitializeDNSMessage(&m->omsg.h, zeroID, ResponseFlags);

        // Put answers in the packet
        while (ResponseRecords && ResponseRecords->NR_AnswerTo)
        {
            rr = ResponseRecords;
            if (rr->resrec.RecordType & kDNSRecordTypeUniqueMask)
                rr->resrec.rrclass |= kDNSClass_UniqueRRSet;        // Temporarily set the cache flush bit so PutResourceRecord will set it

            newptr = PutResourceRecord(&m->omsg, responseptr, &m->omsg.h.numAnswers, &rr->resrec);

            rr->resrec.rrclass &= ~kDNSClass_UniqueRRSet;           // Make sure to clear cache flush bit back to normal state
            if (!newptr && m->omsg.h.numAnswers)
            {
                break; // If packet full, send it now
            }
            if (newptr) responseptr = newptr;
            ResponseRecords = rr->NextResponse;
            rr->NextResponse    = mDNSNULL;
            rr->NR_AnswerTo     = mDNSNULL;
            rr->NR_AdditionalTo = mDNSNULL;
            rr->RequireGoodbye  = mDNStrue;
        }

        // Add additionals, if there's space
        while (ResponseRecords && !ResponseRecords->NR_AnswerTo)
        {
            rr = ResponseRecords;
            if (rr->resrec.RecordType & kDNSRecordTypeUniqueMask)
                rr->resrec.rrclass |= kDNSClass_UniqueRRSet;        // Temporarily set the cache flush bit so PutResourceRecord will set it
            newptr = PutResourceRecord(&m->omsg, responseptr, &m->omsg.h.numAdditionals, &rr->resrec);
            rr->resrec.rrclass &= ~kDNSClass_UniqueRRSet;           // Make sure to clear cache flush bit back to normal state

            if (newptr) responseptr = newptr;
            if (newptr && m->omsg.h.numAnswers) rr->RequireGoodbye = mDNStrue;
            else if (rr->resrec.RecordType & kDNSRecordTypeUniqueMask) rr->ImmedAnswer = mDNSInterfaceMark;
            ResponseRecords = rr->NextResponse;
            rr->NextResponse    = mDNSNULL;
            rr->NR_AnswerTo     = mDNSNULL;
            rr->NR_AdditionalTo = mDNSNULL;
        }

        if (m->omsg.h.numAnswers)
            mDNSSendDNSMessage(m, &m->omsg, responseptr, InterfaceID, mDNSNULL, mDNSNULL, dest, MulticastDNSPort, mDNSNULL, mDNSfalse);
    }
}

// CompleteDeregistration guarantees that on exit the record will have been cut from the m->ResourceRecords list
// and the client's mStatus_MemFree callback will have been invoked
mDNSexport void CompleteDeregistration(mDNS *const m, AuthRecord *rr)
{
    LogInfo("CompleteDeregistration: called for Resource record %s", ARDisplayString(m, rr));
    // Clearing rr->RequireGoodbye signals mDNS_Deregister_internal() that
    // it should go ahead and immediately dispose of this registration
    rr->resrec.RecordType = kDNSRecordTypeShared;
    rr->RequireGoodbye    = mDNSfalse;
    rr->WakeUp.HMAC       = zeroEthAddr;
    if (rr->AnsweredLocalQ) { AnswerAllLocalQuestionsWithLocalAuthRecord(m, rr, QC_rmv); rr->AnsweredLocalQ = mDNSfalse; }
    mDNS_Deregister_internal(m, rr, mDNS_Dereg_normal);     // Don't touch rr after this
}

// DiscardDeregistrations is used on shutdown and sleep to discard (forcibly and immediately)
// any deregistering records that remain in the m->ResourceRecords list.
// DiscardDeregistrations calls mDNS_Deregister_internal which can call a user callback,
// which may change the record list and/or question list.
// Any code walking either list must use the CurrentQuestion and/or CurrentRecord mechanism to protect against this.
mDNSlocal void DiscardDeregistrations(mDNS *const m)
{
    if (m->CurrentRecord)
        LogMsg("DiscardDeregistrations ERROR m->CurrentRecord already set %s", ARDisplayString(m, m->CurrentRecord));
    m->CurrentRecord = m->ResourceRecords;

    while (m->CurrentRecord)
    {
        AuthRecord *rr = m->CurrentRecord;
        if (!AuthRecord_uDNS(rr) && rr->resrec.RecordType == kDNSRecordTypeDeregistering)
            CompleteDeregistration(m, rr);      // Don't touch rr after this
        else
            m->CurrentRecord = rr->next;
    }
}

mDNSlocal mStatus GetLabelDecimalValue(const mDNSu8 *const src, mDNSu8 *dst)
{
    int i, val = 0;
    if (src[0] < 1 || src[0] > 3) return(mStatus_Invalid);
    for (i=1; i<=src[0]; i++)
    {
        if (src[i] < '0' || src[i] > '9') return(mStatus_Invalid);
        val = val * 10 + src[i] - '0';
    }
    if (val > 255) return(mStatus_Invalid);
    *dst = (mDNSu8)val;
    return(mStatus_NoError);
}

mDNSlocal mStatus GetIPv4FromName(mDNSAddr *const a, const domainname *const name)
{
    int skip = CountLabels(name) - 6;
    if (skip < 0) { LogMsg("GetIPFromName: Need six labels in IPv4 reverse mapping name %##s", name); return mStatus_Invalid; }
    if (GetLabelDecimalValue(SkipLeadingLabels(name, skip+3)->c, &a->ip.v4.b[0]) ||
        GetLabelDecimalValue(SkipLeadingLabels(name, skip+2)->c, &a->ip.v4.b[1]) ||
        GetLabelDecimalValue(SkipLeadingLabels(name, skip+1)->c, &a->ip.v4.b[2]) ||
        GetLabelDecimalValue(SkipLeadingLabels(name, skip+0)->c, &a->ip.v4.b[3])) return mStatus_Invalid;
    a->type = mDNSAddrType_IPv4;
    return(mStatus_NoError);
}

#define HexVal(X) ( ((X) >= '0' && (X) <= '9') ? ((X) - '0'     ) :   \
                    ((X) >= 'A' && (X) <= 'F') ? ((X) - 'A' + 10) :   \
                    ((X) >= 'a' && (X) <= 'f') ? ((X) - 'a' + 10) : -1)

mDNSlocal mStatus GetIPv6FromName(mDNSAddr *const a, const domainname *const name)
{
    int i, h, l;
    const domainname *n;