/*
 * $Id: neighbors.c,v 1.319.2.8 2008/06/27 21:52:56 hno Exp $
 *
 * DEBUG: section 15    Neighbor Routines
 * AUTHOR: Harvest Derived
 *
 * SQUID Web Proxy Cache          http://www.squid-cache.org/
 * ----------------------------------------------------------
 *
 *  Squid is the result of efforts by numerous individuals from
 *  the Internet community; see the CONTRIBUTORS file for full
 *  details.   Many organizations have provided support for Squid's
 *  development; see the SPONSORS file for full details.  Squid is
 *  Copyrighted (C) 2001 by the Regents of the University of
 *  California; see the COPYRIGHT file for full details.  Squid
 *  incorporates software developed and/or copyrighted by other
 *  sources; see the CREDITS file for full details.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *  
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *  
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
 *
 */

#include "squid.h"

/* count mcast group peers every 15 minutes */
#define MCAST_COUNT_RATE 900

static int peerWouldBePinged(const peer *, request_t *);
static void neighborRemove(peer *);
static void neighborAlive(peer *, const MemObject *, const icp_common_t *);
#if USE_HTCP
static void neighborAliveHtcp(peer *, const MemObject *, const htcpReplyData *);
#endif
static void neighborCountIgnored(peer *);
static void peerRefreshDNS(void *);
static IPH peerDNSConfigure;
static int peerProbeConnect(peer *);
static CNCB peerProbeConnectDone;
static void peerCountMcastPeersDone(void *data);
static void peerCountMcastPeersStart(void *data);
static void peerCountMcastPeersSchedule(peer * p, time_t when);
static IRCB peerCountHandleIcpReply;
static void neighborIgnoreNonPeer(const struct sockaddr_in *, icp_opcode);
static OBJH neighborDumpPeers;
static OBJH neighborDumpNonPeers;
static void dump_peers(StoreEntry * sentry, peer * peers);

static icp_common_t echo_hdr;
static u_short echo_port;

static int NLateReplies = 0;
static peer *first_ping = NULL;

const char *
neighborTypeStr(const peer * p)
{
    if (p->type == PEER_NONE)
	return "Non-Peer";
    if (p->type == PEER_SIBLING)
	return "Sibling";
    if (p->type == PEER_MULTICAST)
	return "Multicast Group";
    return "Parent";
}


peer *
whichPeer(const struct sockaddr_in * from)
{
    int j;
    u_short port = ntohs(from->sin_port);
    struct in_addr ip = from->sin_addr;
    peer *p = NULL;
    debug(15, 3) ("whichPeer: from %s port %d\n", inet_ntoa(ip), port);
    for (p = Config.peers; p; p = p->next) {
	for (j = 0; j < p->n_addresses; j++) {
	    if (ip.s_addr == p->addresses[j].s_addr && port == p->icp.port) {
		return p;
	    }
	}
    }
    return NULL;
}

peer_t
neighborType(const peer * p, const request_t * request)
{
    const struct _domain_type *d = NULL;
    for (d = p->typelist; d; d = d->next) {
	if (0 == matchDomainName(request->host, d->domain))
	    if (d->type != PEER_NONE)
		return d->type;
    }
#if PEER_MULTICAST_SIBLINGS
    if (p->type == PEER_MULTICAST)
	if (p->options.mcast_siblings)
	    return PEER_SIBLING;
#endif
    return p->type;
}

/*
 * peerAllowedToUse
 *
 * this function figures out if it is appropriate to fetch REQUEST
 * from PEER.
 */
int
peerAllowedToUse(const peer * p, request_t * request)
{
    const struct _domain_ping *d = NULL;
    int do_ping = 1;
    assert(request != NULL);
    if (neighborType(p, request) == PEER_SIBLING) {
#if PEER_MULTICAST_SIBLINGS
	if (p->type == PEER_MULTICAST && p->options.mcast_siblings &&
	    (request->flags.nocache || request->flags.refresh || request->flags.loopdetect || request->flags.need_validation))
	    debug(15, 2) ("peerAllowedToUse(%s, %s) : multicast-siblings optimization match\n",
		p->name, request->host);
#endif
	if (request->flags.nocache)
	    return 0;
	if (request->flags.refresh)
	    return 0;
	if (request->flags.loopdetect)
	    return 0;
	if (request->flags.need_validation)
	    return 0;
    }
    if (p->peer_domain == NULL && p->access == NULL)
	return do_ping;
    do_ping = 0;
    for (d = p->peer_domain; d; d = d->next) {
	if (0 == matchDomainName(request->host, d->domain)) {
	    do_ping = d->do_ping;
	    break;
	}
	do_ping = !d->do_ping;
    }
    if (p->peer_domain && 0 == do_ping)
	return do_ping;
    if (p->access == NULL)
	return do_ping;
    return aclCheckFastRequest(p->access, request);
}

/* Return TRUE if it is okay to send an ICP request to this peer.   */
static int
peerWouldBePinged(const peer * p, request_t * request)
{
    if (!peerAllowedToUse(p, request))
	return 0;
    if (p->options.no_query)
	return 0;
    if (p->options.mcast_responder)
	return 0;
    if (p->n_addresses == 0)
	return 0;
    if (p->icp.port == 0)
	return 0;
    /* the case below seems strange, but can happen if the
     * URL host is on the other side of a firewall */
    if (p->type == PEER_SIBLING)
	if (!request->flags.hierarchical)
	    return 0;
    /* Ping dead peers every timeout interval */
    if (squid_curtime - p->stats.last_query > Config.Timeout.deadPeer)
	return 1;
    if (!neighborUp(p))
	return 0;
    return 1;
}

/* Return TRUE if it is okay to send an HTTP request to this peer. */
int
peerHTTPOkay(const peer * p, request_t * request)
{
    if (!peerAllowedToUse(p, request))
	return 0;
    if (!neighborUp(p))
	return 0;
    if (p->max_conn)
	if (p->stats.conn_open >= p->max_conn)
	    return 0;
    return 1;
}

int
neighborsCount(request_t * request)
{
    peer *p = NULL;
    int count = 0;
    for (p = Config.peers; p; p = p->next)
	if (peerWouldBePinged(p, request))
	    count++;
    debug(15, 3) ("neighborsCount: %d\n", count);
    return count;
}

#if UNUSED_CODE
peer *
getSingleParent(request_t * request)
{
    peer *p = NULL;
    peer *q = NULL;
    for (q = Config.peers; q; q = q->next) {
	if (!peerHTTPOkay(q, request))
	    continue;
	if (neighborType(q, request) != PEER_PARENT)
	    return NULL;	/* oops, found SIBLING */
	if (p)
	    return NULL;	/* oops, found second parent */
	p = q;
    }
    if (p != NULL && !p->options.no_query)
	return NULL;
    debug(15, 3) ("getSingleParent: returning %s\n", p ? p->name : "NULL");
    return p;
}
#endif

peer *
getFirstUpParent(request_t * request)
{
    peer *p = NULL;
    for (p = Config.peers; p; p = p->next) {
	if (!neighborUp(p))
	    continue;
	if (neighborType(p, request) != PEER_PARENT)
	    continue;
	if (!peerHTTPOkay(p, request))
	    continue;
	break;
    }
    debug(15, 3) ("getFirstUpParent: returning %s\n", p ? p->name : "NULL");
    return p;
}

peer *
getRoundRobinParent(request_t * request)
{
    peer *p;
    peer *q = NULL;
    for (p = Config.peers; p; p = p->next) {
	if (!p->options.roundrobin)
	    continue;
	if (neighborType(p, request) != PEER_PARENT)
	    continue;
	if (!peerHTTPOkay(p, request))
	    continue;
	if (p->weight == 0)
	    continue;

	if (q) {
	    if (p->weight == q->weight) {
		if (q->rr_count < p->rr_count)
		    continue;
	    } else if ((double) q->rr_count / q->weight < (double) p->rr_count / p->weight) {
		continue;
	    }
	}
	q = p;
    }
    if (q)
	q->rr_count++;
    debug(15, 3) ("getRoundRobinParent: returning %s\n", q ? q->host : "NULL");
    return q;
}

/* This gets called every 5 minutes to clear the round-robin counter. */
static void
peerClearRRLoop(void *data)
{
    peerClearRR();
    eventAdd("peerClearRR", peerClearRRLoop, data, 5 * 60.0, 0);
}

void
peerClearRRStart(void)
{
    static int event_added = 0;
    if (!event_added) {
	peerClearRRLoop(NULL);
    }
}

/* Actually clear the round-robin counter. */
void
peerClearRR(void)
{
    peer *p = NULL;
    for (p = Config.peers; p; p = p->next) {
	p->rr_count = 0;
    }
}

peer *
getDefaultParent(request_t * request)
{
    peer *p = NULL;
    for (p = Config.peers; p; p = p->next) {
	if (neighborType(p, request) != PEER_PARENT)
	    continue;
	if (!p->options.default_parent)
	    continue;
	if (!peerHTTPOkay(p, request))
	    continue;
	debug(15, 3) ("getDefaultParent: returning %s\n", p->name);
	return p;
    }
    debug(15, 3) ("getDefaultParent: returning NULL\n");
    return NULL;
}

/*
 * XXX DW thinks this function is equivalent to/redundant with
 * getFirstUpParent().  peerHTTPOkay() only returns true if the
 * peer is UP anyway, so this function would not return a 
 * DOWN parent.
 */
peer *
getAnyParent(request_t * request)
{
    peer *p = NULL;
    for (p = Config.peers; p; p = p->next) {
	if (neighborType(p, request) != PEER_PARENT)
	    continue;
	if (!peerHTTPOkay(p, request))
	    continue;
	debug(15, 3) ("getAnyParent: returning %s\n", p->name);
	return p;
    }
    debug(15, 3) ("getAnyParent: returning NULL\n");
    return NULL;
}

peer *
getNextPeer(peer * p)
{
    return p->next;
}

peer *
getFirstPeer(void)
{
    return Config.peers;
}

static void
neighborRemove(peer * target)
{
    peer *p = NULL;
    peer **P = NULL;
    p = Config.peers;
    P = &Config.peers;
    while (p) {
	if (target == p)
	    break;
	P = &p->next;
	p = p->next;
    }
    if (p) {
	*P = p->next;
	cbdataFree(p);
	Config.npeers--;
    }
    first_ping = Config.peers;
}

void
neighbors_init(void)
{
    struct sockaddr_in name;
    socklen_t len = sizeof(struct sockaddr_in);
    struct servent *sep = NULL;
    const char *me = getMyHostname();
    peer *this;
    peer *next;
    int fd = theInIcpConnection;
    if (fd >= 0) {
	memset(&name, '\0', sizeof(struct sockaddr_in));
	if (getsockname(fd, (struct sockaddr *) &name, &len) < 0)
	    debug(15, 1) ("getsockname(%d,%p,%p) failed.\n", fd, &name, &len);
	for (this = Config.peers; this; this = next) {
	    http_port_list *s;
	    next = this->next;
	    if (0 != strcmp(this->host, me))
		continue;
	    for (s = Config.Sockaddr.http; s; s = s->next) {
		if (this->http_port != ntohs(s->s.sin_port))
		    continue;
		debug(15, 1) ("WARNING: Peer looks like this host\n");
		debug(15, 1) ("         Ignoring %s %s/%d/%d\n",
		    neighborTypeStr(this), this->host, this->http_port,
		    this->icp.port);
		neighborRemove(this);
	    }
	}
    }
    peerRefreshDNS((void *) 1);
    if (0 == echo_hdr.opcode) {
	echo_hdr.opcode = ICP_SECHO;
	echo_hdr.version = ICP_VERSION_CURRENT;
	echo_hdr.length = 0;
	echo_hdr.reqnum = 0;
	echo_hdr.flags = 0;
	echo_hdr.pad = 0;
	echo_hdr.shostid = name.sin_addr.s_addr;
	sep = getservbyname("echo", "udp");
	echo_port = sep ? ntohs((u_short) sep->s_port) : 7;
    }
    first_ping = Config.peers;
    cachemgrRegister("server_list",
	"Peer Cache Statistics",
	neighborDumpPeers, 0, 1);
    if (theInIcpConnection >= 0) {
	cachemgrRegister("non_peers",
	    "List of Unknown sites sending ICP messages",
	    neighborDumpNonPeers, 0, 1);
    }
}

int
neighborsUdpPing(request_t * request,
    StoreEntry * entry,
    IRCB * callback,
    void *callback_data,
    int *exprep,
    int *timeout)
{
    const char *url = storeUrl(entry);
    MemObject *mem = entry->mem_obj;
    peer *p = NULL;
    int i;
    int reqnum = 0;
    int flags;
    icp_common_t *query;
    int queries_sent = 0;
    int peers_pinged = 0;
    int parent_timeout = 0, parent_exprep = 0;
    int sibling_timeout = 0, sibling_exprep = 0;
    int mcast_timeout = 0, mcast_exprep = 0;

    if (Config.peers == NULL)
	return 0;
    if (theOutIcpConnection < 0)
	fatal("neighborsUdpPing: There is no ICP socket!");
    assert(entry->swap_status == SWAPOUT_NONE);
    mem->start_ping = current_time;
    mem->ping_reply_callback = callback;
    mem->ircb_data = callback_data;
    reqnum = icpSetCacheKey(entry->hash.key);
    for (i = 0, p = first_ping; i++ < Config.npeers; p = p->next) {
	if (p == NULL)
	    p = Config.peers;
	debug(15, 5) ("neighborsUdpPing: Peer %s\n", p->name);
	if (!peerWouldBePinged(p, request))
	    continue;		/* next peer */
	peers_pinged++;
	debug(15, 4) ("neighborsUdpPing: pinging peer %s for '%s'\n",
	    p->name, url);
	if (p->type == PEER_MULTICAST)
	    mcastSetTtl(theOutIcpConnection, p->mcast.ttl);
	debug(15, 3) ("neighborsUdpPing: key = '%s'\n", storeKeyText(entry->hash.key));
	debug(15, 3) ("neighborsUdpPing: reqnum = %d\n", reqnum);

#if USE_HTCP
	if (p->options.htcp) {
	    debug(15, 3) ("neighborsUdpPing: sending HTCP query\n");
	    htcpQuery(entry, request, p);
	} else
#endif
	if (p->icp.port == echo_port) {
	    debug(15, 4) ("neighborsUdpPing: Looks like a dumb cache, send DECHO ping\n");
	    echo_hdr.reqnum = reqnum;
	    query = icpCreateMessage(ICP_DECHO, 0, url, reqnum, 0);
	    icpUdpSend(theOutIcpConnection,
		&p->in_addr,
		query,
		LOG_ICP_QUERY,
		0);
	} else {
	    flags = 0;
	    if (Config.onoff.query_icmp)
		if (p->icp.version == ICP_VERSION_2)
		    flags |= ICP_FLAG_SRC_RTT;
	    query = icpCreateMessage(ICP_QUERY, flags, url, reqnum, 0);
	    icpUdpSend(theOutIcpConnection,
		&p->in_addr,
		query,
		LOG_ICP_QUERY,
		0);
	}
	queries_sent++;

	p->stats.pings_sent++;
	if (p->type == PEER_MULTICAST) {
	    mcast_exprep += p->mcast.n_replies_expected;
	    mcast_timeout += (p->stats.rtt * p->mcast.n_replies_expected);
	} else if (neighborUp(p)) {
	    /* its alive, expect a reply from it */
	    if (neighborType(p, request) == PEER_PARENT) {
		parent_exprep++;
		parent_timeout += p->stats.rtt;
	    } else {
		sibling_exprep++;
		sibling_timeout += p->stats.rtt;
	    }
	} else {
	    /* Neighbor is dead; ping it anyway, but don't expect a reply */
	    /* log it once at the threshold */
	    if (p->stats.logged_state == PEER_ALIVE) {
		debug(15, 1) ("Detected DEAD %s: %s\n",
		    neighborTypeStr(p), p->name);
		p->stats.logged_state = PEER_DEAD;
	    }
	}
	p->stats.last_query = squid_curtime;
	/*
	 * keep probe_start == 0 for a multicast peer,
	 * so neighborUp() never says this peer is dead.
	 */
	if ((p->type != PEER_MULTICAST) && (p->stats.probe_start == 0))
	    p->stats.probe_start = squid_curtime;
    }
    if ((first_ping = first_ping->next) == NULL)
	first_ping = Config.peers;

#if ALLOW_SOURCE_PING
    /* only do source_ping if we have neighbors */
    if (Config.npeers) {
	const ipcache_addrs *ia = NULL;
	struct sockaddr_in to_addr;
	char *host = request->host;
	if (!Config.onoff.source_ping) {
	    debug(15, 6) ("neighborsUdpPing: Source Ping is disabled.\n");
	} else if ((ia = ipcache_gethostbyname(host, 0))) {
	    debug(15, 6) ("neighborsUdpPing: Source Ping: to %s for '%s'\n",
		host, url);
	    echo_hdr.reqnum = reqnum;
	    if (icmp_sock != -1) {
		icmpSourcePing(ia->in_addrs[ia->cur], &echo_hdr, url);
	    } else {
		to_addr.sin_family = AF_INET;
		to_addr.sin_addr = ia->in_addrs[ia->cur];
		to_addr.sin_port = htons(echo_port);
		query = icpCreateMessage(ICP_SECHO, 0, url, reqnum, 0);
		icpUdpSend(theOutIcpConnection,
		    &to_addr,
		    query,
		    LOG_ICP_QUERY,
		    0);
	    }
	} else {
	    debug(15, 6) ("neighborsUdpPing: Source Ping: unknown host: %s\n",
		host);
	}
    }
#endif
    /*
     * How many replies to expect?
     */
    *exprep = parent_exprep + sibling_exprep + mcast_exprep;

    /*
     * If there is a configured timeout, use it
     */
    if (Config.Timeout.icp_query)
	*timeout = Config.Timeout.icp_query;
    else {
	if (*exprep > 0) {
	    if (parent_exprep)
		*timeout = 2 * parent_timeout / parent_exprep;
	    else if (mcast_exprep)
		*timeout = 2 * mcast_timeout / mcast_exprep;
	    else
		*timeout = 2 * sibling_timeout / sibling_exprep;
	} else
	    *timeout = 2000;	/* 2 seconds */
	if (Config.Timeout.icp_query_max)
	    if (*timeout > Config.Timeout.icp_query_max)
		*timeout = Config.Timeout.icp_query_max;

	if (*timeout < Config.Timeout.icp_query_min)
	    *timeout = Config.Timeout.icp_query_min;
    }
    return peers_pinged;
}

/* lookup the digest of a given peer */
lookup_t
peerDigestLookup(peer * p, request_t * request)
{
#if USE_CACHE_DIGESTS
    const cache_key *key = request ? storeKeyPublicByRequest(request) : NULL;
    assert(p);
    assert(request);
    debug(15, 5) ("peerDigestLookup: peer %s\n", p->name);
    /* does the peeer have a valid digest? */
    if (!p->digest) {
	debug(15, 5) ("peerDigestLookup: gone!\n");
	return LOOKUP_NONE;
    } else if (!peerHTTPOkay(p, request)) {
	debug(15, 5) ("peerDigestLookup: !peerHTTPOkay\n");
	return LOOKUP_NONE;
    } else if (!p->digest->flags.needed) {
	debug(15, 5) ("peerDigestLookup: note need\n");
	peerDigestNeeded(p->digest);
	return LOOKUP_NONE;
    } else if (!p->digest->flags.usable) {
	debug(15, 5) ("peerDigestLookup: !ready && %srequested\n",
	    p->digest->flags.requested ? "" : "!");
	return LOOKUP_NONE;
    }
    debug(15, 5) ("peerDigestLookup: OK to lookup peer %s\n", p->name);
    assert(p->digest->cd);
    /* does digest predict a hit? */
    if (!cacheDigestTest(p->digest->cd, key))
	return LOOKUP_MISS;
    debug(15, 5) ("peerDigestLookup: peer %s says HIT!\n", p->name);
    return LOOKUP_HIT;
#endif
    return LOOKUP_NONE;
}

/* select best peer based on cache digests */
peer *
neighborsDigestSelect(request_t * request)
{
    peer *best_p = NULL;
#if USE_CACHE_DIGESTS
    const cache_key *key;
    int best_rtt = 0;
    int choice_count = 0;
    int ichoice_count = 0;
    peer *p;
    int p_rtt;
    int i;
    if (!request->flags.hierarchical)
	return NULL;
    key = storeKeyPublicByRequest(request);
    for (i = 0, p = first_ping; i++ < Config.npeers; p = p->next) {
	lookup_t lookup;
	if (!p)
	    p = Config.peers;
	if (i == 1)
	    first_ping = p;
	lookup = peerDigestLookup(p, request);
	if (lookup == LOOKUP_NONE)
	    continue;
	choice_count++;
	if (lookup == LOOKUP_MISS)
	    continue;
	p_rtt = netdbHostRtt(p->host);
	debug(15, 5) ("neighborsDigestSelect: peer %s rtt: %d\n",
	    p->name, p_rtt);
	/* is this peer better than others in terms of rtt ? */
	if (!best_p || (p_rtt && p_rtt < best_rtt)) {
	    best_p = p;
	    best_rtt = p_rtt;
	    if (p_rtt)		/* informative choice (aka educated guess) */
		ichoice_count++;
	    debug(15, 4) ("neighborsDigestSelect: peer %s leads with rtt %d\n",
		p->name, best_rtt);
	}
    }
    debug(15, 4) ("neighborsDigestSelect: choices: %d (%d)\n",
	choice_count, ichoice_count);
    peerNoteDigestLookup(request, best_p,
	best_p ? LOOKUP_HIT : (choice_count ? LOOKUP_MISS : LOOKUP_NONE));
    request->hier.n_choices = choice_count;
    request->hier.n_ichoices = ichoice_count;
#endif
    return best_p;
}

void
peerNoteDigestLookup(request_t * request, peer * p, lookup_t lookup)
{
#if USE_CACHE_DIGESTS
    if (p)
	strncpy(request->hier.cd_host, p->host, sizeof(request->hier.cd_host));
    else
	*request->hier.cd_host = '\0';
    request->hier.cd_lookup = lookup;
    debug(15, 4) ("peerNoteDigestLookup: peer %s, lookup: %s\n",
	p ? p->name : "<none>", lookup_t_str[lookup]);
#endif
}

static void
neighborAlive(peer * p, const MemObject * mem, const icp_common_t * header)
{
    if (p->stats.logged_state == PEER_DEAD && p->tcp_up) {
	debug(15, 1) ("Detected REVIVED %s: %s\n",
	    neighborTypeStr(p), p->name);
	p->stats.logged_state = PEER_ALIVE;
	peerClearRR();
    }
    p->stats.last_reply = squid_curtime;
    p->stats.probe_start = 0;
    p->stats.pings_acked++;
    if ((icp_opcode) header->opcode <= ICP_END)
	p->icp.counts[header->opcode]++;
    p->icp.version = (int) header->version;
}

static void
neighborUpdateRtt(peer * p, MemObject * mem)
{
    int rtt;
    if (!mem)
	return;
    if (!mem->start_ping.tv_sec)
	return;
    rtt = tvSubMsec(mem->start_ping, current_time);
    if (rtt < 1 || rtt > 10000)
	return;
    p->stats.rtt = intAverage(p->stats.rtt, rtt,
	p->stats.pings_acked, RTT_AV_FACTOR);
}

#if USE_HTCP
static void
neighborAliveHtcp(peer * p, const MemObject * mem, const htcpReplyData * htcp)
{
    if (p->stats.logged_state == PEER_DEAD && p->tcp_up) {
	debug(15, 1) ("Detected REVIVED %s: %s\n",
	    neighborTypeStr(p), p->name);
	p->stats.logged_state = PEER_ALIVE;
	peerClearRR();
    }
    p->stats.last_reply = squid_curtime;
    p->stats.probe_start = 0;
    p->stats.pings_acked++;
    p->htcp.counts[htcp->hit ? 1 : 0]++;
    p->htcp.version = htcp->version;
}
#endif

static void
neighborCountIgnored(peer * p)
{
    if (p == NULL)
	return;
    p->stats.ignored_replies++;
    NLateReplies++;
}

static peer *non_peers = NULL;

static void
neighborIgnoreNonPeer(const struct sockaddr_in *from, icp_opcode opcode)
{
    peer *np;
    for (np = non_peers; np; np = np->next) {
	if (np->in_addr.sin_addr.s_addr != from->sin_addr.s_addr)
	    continue;
	if (np->in_addr.sin_port != from->sin_port)
	    continue;
	break;
    }
    if (np == NULL) {
	np = xcalloc(1, sizeof(peer));
	np->in_addr.sin_addr = from->sin_addr;
	np->in_addr.sin_port = from->sin_port;
	np->icp.port = ntohl(from->sin_port);
	np->type = PEER_NONE;
	np->host = xstrdup(inet_ntoa(from->sin_addr));
	np->next = non_peers;
	non_peers = np;
    }
    np->icp.counts[opcode]++;
    if (isPowTen(++np->stats.ignored_replies))
	debug(15, 1) ("WARNING: Ignored %d replies from non-peer %s\n",
	    np->stats.ignored_replies, np->host);
}

/* ignoreMulticastReply
 * 
 * * We want to ignore replies from multicast peers if the
 * * cache_host_domain rules would normally prevent the peer
 * * from being used
 */
static int
ignoreMulticastReply(peer * p, MemObject * mem)
{
    if (p == NULL)
	return 0;
    if (!p->options.mcast_responder)
	return 0;
    if (peerHTTPOkay(p, mem->request))
	return 0;
    return 1;
}

/* I should attach these records to the entry.  We take the first
 * hit we get our wait until everyone misses.  The timeout handler
 * call needs to nip this shopping list or call one of the misses.
 * 
 * If a hit process is already started, then sobeit
 */
void
neighborsUdpAck(const cache_key * key, icp_common_t * header, const struct sockaddr_in *from)
{
    peer *p = NULL;
    StoreEntry *entry;
    MemObject *mem = NULL;
    peer_t ntype = PEER_NONE;
    const char *opcode_d;
    icp_opcode opcode = (icp_opcode) header->opcode;

    debug(15, 6) ("neighborsUdpAck: opcode %d '%s'\n",
	(int) opcode, storeKeyText(key));
    if (NULL != (entry = storeGet(key)))
	mem = entry->mem_obj;
    if ((p = whichPeer(from)))
	neighborAlive(p, mem, header);
    if (opcode > ICP_END)
	return;
    opcode_d = icp_opcode_str[opcode];
    if (p)
	neighborUpdateRtt(p, mem);
    /* Does the entry exist? */
    if (NULL == entry) {
	debug(12, 3) ("neighborsUdpAck: Cache key '%s' not found\n",
	    storeKeyText(key));
	neighborCountIgnored(p);
	return;
    }
    /* check if someone is already fetching it */
    if (EBIT_TEST(entry->flags, ENTRY_DISPATCHED)) {
	debug(15, 3) ("neighborsUdpAck: '%s' already being fetched.\n",
	    storeKeyText(key));
	neighborCountIgnored(p);
	return;
    }
    if (mem == NULL) {
	debug(15, 2) ("Ignoring %s for missing mem_obj: %s\n",
	    opcode_d, storeKeyText(key));
	neighborCountIgnored(p);
	return;
    }
    if (entry->ping_status != PING_WAITING) {
	debug(15, 2) ("neighborsUdpAck: Late %s for %s\n",
	    opcode_d, storeKeyText(key));
	neighborCountIgnored(p);
	return;
    }
    if (entry->lock_count == 0) {
	debug(12, 1) ("neighborsUdpAck: '%s' has no locks\n",
	    storeKeyText(key));
	neighborCountIgnored(p);
	return;
    }
    debug(15, 3) ("neighborsUdpAck: %s for '%s' from %s \n",
	opcode_d, storeKeyText(key), p ? p->name : "source");
    if (p) {
	ntype = neighborType(p, mem->request);
    }
    if (ignoreMulticastReply(p, mem)) {
	neighborCountIgnored(p);
    } else if (opcode == ICP_MISS) {
	if (p == NULL) {
	    neighborIgnoreNonPeer(from, opcode);
	} else {
	    mem->ping_reply_callback(p, ntype, PROTO_ICP, header, mem->ircb_data);
	}
    } else if (opcode == ICP_HIT) {
	if (p == NULL) {
	    neighborIgnoreNonPeer(from, opcode);
	} else {
	    header->opcode = ICP_HIT;
	    mem->ping_reply_callback(p, ntype, PROTO_ICP, header, mem->ircb_data);
	}
    } else if (opcode == ICP_DECHO) {
	if (p == NULL) {
	    neighborIgnoreNonPeer(from, opcode);
	} else if (ntype == PEER_SIBLING) {
	    debug_trap("neighborsUdpAck: Found non-ICP cache as SIBLING\n");
	    debug_trap("neighborsUdpAck: non-ICP neighbors must be a PARENT\n");
	} else {
	    mem->ping_reply_callback(p, ntype, PROTO_ICP, header, mem->ircb_data);
	}
    } else if (opcode == ICP_SECHO) {
	if (p) {
	    debug(15, 1) ("Ignoring SECHO from neighbor %s\n", p->name);
	    neighborCountIgnored(p);
#if ALLOW_SOURCE_PING
	} else if (Config.onoff.source_ping) {
	    mem->ping_reply_callback(NULL, ntype, PROTO_ICP, header, mem->ircb_data);
#endif
	} else {
	    debug(15, 1) ("Unsolicited SECHO from %s\n", inet_ntoa(from->sin_addr));
	}
    } else if (opcode == ICP_DENIED) {
	if (p == NULL) {
	    neighborIgnoreNonPeer(from, opcode);
	} else if (p->stats.pings_acked > 100) {
	    if (100 * p->icp.counts[ICP_DENIED] / p->stats.pings_acked > 95) {
		debug(15, 0) ("95%% of replies from '%s' are UDP_DENIED\n", p->name);
		debug(15, 0) ("Disabling '%s', please check your configuration.\n", p->name);
		neighborRemove(p);
		p = NULL;
	    } else {
		neighborCountIgnored(p);
	    }
	}
    } else if (opcode == ICP_MISS_NOFETCH) {
	mem->ping_reply_callback(p, ntype, PROTO_ICP, header, mem->ircb_data);
    } else {
	debug(15, 0) ("neighborsUdpAck: Unexpected ICP reply: %s\n", opcode_d);
    }
}

peer *
peerFindByName(const char *name)
{
    peer *p = NULL;
    for (p = Config.peers; p; p = p->next) {
	if (!strcasecmp(name, p->name))
	    break;
    }
    return p;
}

peer *
peerFindByNameAndPort(const char *name, unsigned short port)
{
    peer *p = NULL;
    for (p = Config.peers; p; p = p->next) {
	if (strcasecmp(name, p->name))
	    continue;
	if (port != p->http_port)
	    continue;
	break;
    }
    return p;
}

int
neighborUp(const peer * p)
{
    if (!p->tcp_up) {
	if (!peerProbeConnect((peer *) p))
	    return 0;
    }
    if (p->stats.logged_state != PEER_ALIVE)
	return 0;
    if (p->monitor.state != PEER_ALIVE)
	return 0;
    /*
     * The peer can not be UP if we don't have any IP addresses
     * for it. 
     */
    if (0 == p->n_addresses)
	return 0;
    if (p->options.no_query)
	return 1;
    if (p->stats.probe_start != 0 &&
	squid_curtime - p->stats.probe_start > Config.Timeout.deadPeer)
	return 0;
    return 1;
}

void
peerDestroy(void *data)
{
    peer *p = data;
    struct _domain_ping *l = NULL;
    struct _domain_ping *nl = NULL;
    if (p == NULL)
	return;
    for (l = p->peer_domain; l; l = nl) {
	nl = l->next;
	safe_free(l->domain);
	safe_free(l);
    }
    aclDestroyAccessList(&p->access);
    safe_free(p->host);
    safe_free(p->name);
    safe_free(p->domain);
    safe_free(p->login);
#if USE_CACHE_DIGESTS
    if (p->digest) {
	PeerDigest *pd = p->digest;
	p->digest = NULL;
	cbdataUnlock(pd);
    }
    safe_free(p->digest_url);
#endif
    safe_free(p->monitor.url)
#if USE_SSL
	safe_free(p->sslcert);
    safe_free(p->sslkey);
    safe_free(p->ssloptions);
    safe_free(p->sslcipher);
    safe_free(p->sslcafile);
    safe_free(p->sslcapath);
    safe_free(p->sslcrlfile);
    safe_free(p->sslflags);
    safe_free(p->ssldomain);
    if (p->sslContext) {
	SSL_CTX_free(p->sslContext);
	p->sslContext = NULL;
    }
    if (p->sslSession) {
	SSL_SESSION_free(p->sslSession);
	p->sslSession = NULL;
    }
#endif
}

void
peerNoteDigestGone(peer * p)
{
#if USE_CACHE_DIGESTS
    if (p->digest) {
	PeerDigest *pd = p->digest;
	p->digest = NULL;
	cbdataUnlock(pd);
    }
#endif
}

static void
peerDNSConfigure(const ipcache_addrs * ia, void *data)
{
    peer *p = data;
    struct sockaddr_in *ap;
    int j;
    if (p->n_addresses == 0) {
	debug(15, 1) ("Configuring %s %s %s/%d/%d\n", p->name, neighborTypeStr(p),
	    p->name, p->http_port, p->icp.port);
	if (p->type == PEER_MULTICAST)
	    debug(15, 1) ("    Multicast TTL = %d\n", p->mcast.ttl);
    }
    p->n_addresses = 0;
    if (ia == NULL) {
	debug(0, 0) ("WARNING: DNS lookup of '%s' failed!\n", p->host);
	return;
    }
    if ((int) ia->count < 1) {
	debug(0, 0) ("WARNING: No IP address found for '%s'!\n", p->host);
	return;
    }
    for (j = 0; j < (int) ia->count && j < PEER_MAX_ADDRESSES; j++) {
	p->addresses[j] = ia->in_addrs[j];
	debug(15, 2) ("--> IP address #%d: %s\n", j, inet_ntoa(p->addresses[j]));
	p->n_addresses++;
    }
    if (!p->tcp_up)
	peerProbeConnect((peer *) p);
    ap = &p->in_addr;
    memset(ap, '\0', sizeof(struct sockaddr_in));
    ap->sin_family = AF_INET;
    ap->sin_addr = p->addresses[0];
    ap->sin_port = htons(p->icp.port);
    if (p->type == PEER_MULTICAST)
	peerCountMcastPeersSchedule(p, 10);
    if (p->type != PEER_MULTICAST)
	if (!p->options.no_netdb_exchange)
	    eventAddIsh("netdbExchangeStart", netdbExchangeStart, p, 30.0, 1);
}

static void
peerRefreshDNS(void *data)
{
    peer *p = NULL;
    if (eventFind(peerRefreshDNS, NULL))
	eventDelete(peerRefreshDNS, NULL);
    if (!data && 0 == stat5minClientRequests()) {
	/* no recent client traffic, wait a bit */
	eventAddIsh("peerRefreshDNS", peerRefreshDNS, NULL, 180.0, 1);
	return;
    }
    for (p = Config.peers; p; p = p->next) {
	ipcache_nbgethostbyname(p->host, peerDNSConfigure, p);
    }
    /* Reconfigure the peers every hour */
    eventAddIsh("peerRefreshDNS", peerRefreshDNS, NULL, 3600.0, 1);
}

static void
peerConnectFailedSilent(peer * p)
{
    p->stats.last_connect_failure = squid_curtime;
    if (!p->tcp_up) {
	debug(15, 2) ("TCP connection to %s (%s:%d) dead\n", p->name, p->host, p->http_port);
	return;
    }
    p->tcp_up--;
    if (!p->tcp_up) {
	debug(15, 1) ("Detected DEAD %s: %s\n",
	    neighborTypeStr(p), p->name);
	p->stats.logged_state = PEER_DEAD;
    }
}

void
peerConnectFailed(peer * p)
{
    debug(15, 1) ("TCP connection to %s (%s:%d) failed\n", p->name, p->host, p->http_port);
    peerConnectFailedSilent(p);
}

void
peerConnectSucceded(peer * p)
{
    if (!p->tcp_up) {
	debug(15, 2) ("TCP connection to %s (%s:%d) succeded\n", p->name, p->host, p->http_port);
	debug(15, 1) ("Detected REVIVED %s: %s\n",
	    neighborTypeStr(p), p->name);
	peerMonitorNow(p);
	p->stats.logged_state = PEER_ALIVE;
	peerClearRR();
	if (!p->n_addresses)
	    ipcache_nbgethostbyname(p->host, peerDNSConfigure, p);
    }
    p->tcp_up = PEER_TCP_MAGIC_COUNT;
}

static void
peerProbeConnectTimeout(int fd, void *data)
{
    peer *p = data;
    comm_close(fd);
    p->test_fd = -1;
    peerConnectFailedSilent(p);
}

/*
 * peerProbeConnect will be called on dead peers by neighborUp 
 */
static int
peerProbeConnect(peer * p)
{
    int fd;
    time_t ctimeout = p->connect_timeout > 0 ? p->connect_timeout
    : Config.Timeout.peer_connect;
    int ret = squid_curtime - p->stats.last_connect_failure > ctimeout * 10;
    if (p->test_fd != -1)
	return ret;		/* probe already running */
    if (squid_curtime - p->stats.last_connect_probe == 0)
	return ret;		/* don't probe to often */
    fd = comm_open(SOCK_STREAM, IPPROTO_TCP, getOutgoingAddr(NULL),
	0, COMM_NONBLOCKING, p->name);
    if (fd < 0)
	return ret;
    commSetTimeout(fd, ctimeout, peerProbeConnectTimeout, p);
    p->test_fd = fd;
    p->stats.last_connect_probe = squid_curtime;
    commConnectStart(p->test_fd,
	p->host,
	p->http_port,
	peerProbeConnectDone,
	p);
    return ret;
}

static void
peerProbeConnectDone(int fd, int status, void *data)
{
    peer *p = data;
    if (status == COMM_OK) {
	peerConnectSucceded(p);
    } else {
	peerConnectFailedSilent(p);
    }
    comm_close(fd);
    p->test_fd = -1;
    return;
}

static void
peerCountMcastPeersSchedule(peer * p, time_t when)
{
    if (p->mcast.flags.count_event_pending)
	return;
    eventAdd("peerCountMcastPeersStart",
	peerCountMcastPeersStart,
	p,
	(double) when, 1);
    p->mcast.flags.count_event_pending = 1;
}

static void
peerCountMcastPeersStart(void *data)
{
    peer *p = data;
    ps_state *psstate;
    StoreEntry *fake;
    MemObject *mem;
    icp_common_t *query;
    int reqnum;
    LOCAL_ARRAY(char, url, MAX_URL);
    assert(p->type == PEER_MULTICAST);
    p->mcast.flags.count_event_pending = 0;
    snprintf(url, MAX_URL, "http://%s/", inet_ntoa(p->in_addr.sin_addr));
    fake = storeCreateEntry(url, null_request_flags, METHOD_GET);
    psstate = cbdataAlloc(ps_state);
    psstate->request = requestLink(urlParse(METHOD_GET, url));
    psstate->entry = fake;
    psstate->callback = NULL;
    psstate->callback_data = p;
    cbdataLock(psstate->callback_data);
    psstate->ping.start = current_time;
    mem = fake->mem_obj;
    mem->request = requestLink(psstate->request);
    mem->start_ping = current_time;
    mem->ping_reply_callback = peerCountHandleIcpReply;
    mem->ircb_data = psstate;
    mcastSetTtl(theOutIcpConnection, p->mcast.ttl);
    p->mcast.id = mem->id;
    reqnum = icpSetCacheKey(fake->hash.key);
    query = icpCreateMessage(ICP_QUERY, 0, url, reqnum, 0);
    icpUdpSend(theOutIcpConnection,
	&p->in_addr,
	query,
	LOG_ICP_QUERY,
	0);
    fake->ping_status = PING_WAITING;
    eventAdd("peerCountMcastPeersDone",
	peerCountMcastPeersDone,
	psstate,
	Config.Timeout.mcast_icp_query / 1000.0, 1);
    p->mcast.flags.counting = 1;
    peerCountMcastPeersSchedule(p, MCAST_COUNT_RATE);
}

static void
peerCountMcastPeersDone(void *data)
{
    ps_state *psstate = data;
    peer *p = psstate->callback_data;
    StoreEntry *fake = psstate->entry;
    if (cbdataValid(p)) {
	p->mcast.flags.counting = 0;
	p->mcast.avg_n_members = doubleAverage(p->mcast.avg_n_members,
	    (double) psstate->ping.n_recv,
	    ++p->mcast.n_times_counted,
	    10);
	debug(15, 1) ("Group %s: %d replies, %4.1f average, RTT %d\n",
	    p->host,
	    psstate->ping.n_recv,
	    p->mcast.avg_n_members,
	    p->stats.rtt);
	p->mcast.n_replies_expected = (int) p->mcast.avg_n_members;
    }
    cbdataUnlock(p);
    EBIT_SET(fake->flags, ENTRY_ABORTED);
    requestUnlink(fake->mem_obj->request);
    fake->mem_obj->request = NULL;
    storeReleaseRequest(fake);
    storeUnlockObject(fake);
    requestUnlink(psstate->request);
    cbdataFree(psstate);
}

static void
peerCountHandleIcpReply(peer * p, peer_t type, protocol_t proto, void *hdrnotused, void *data)
{
    ps_state *psstate = data;
    StoreEntry *fake = psstate->entry;
    MemObject *mem = fake->mem_obj;
    int rtt = tvSubMsec(mem->start_ping, current_time);
    assert(proto == PROTO_ICP);
    assert(fake);
    assert(mem);
    psstate->ping.n_recv++;
    p->stats.rtt = intAverage(p->stats.rtt, rtt, psstate->ping.n_recv, RTT_AV_FACTOR);
}

static void
neighborDumpPeers(StoreEntry * sentry)
{
    dump_peers(sentry, Config.peers);
}

static void
neighborDumpNonPeers(StoreEntry * sentry)
{
    dump_peers(sentry, non_peers);
}

void
dump_peer_options(StoreEntry * sentry, peer * p)
{
    if (p->options.proxy_only)
	storeAppendPrintf(sentry, " proxy-only");
    if (p->options.no_query)
	storeAppendPrintf(sentry, " no-query");
    if (p->options.no_digest)
	storeAppendPrintf(sentry, " no-digest");
    if (p->options.default_parent)
	storeAppendPrintf(sentry, " default");
    if (p->options.roundrobin)
	storeAppendPrintf(sentry, " round-robin");
    if (p->options.mcast_responder)
	storeAppendPrintf(sentry, " multicast-responder");
#if PEER_MULTICAST_SIBLINGS
    if (p->options.mcast_siblings)
	storeAppendPrintf(sentry, " multicast-siblings");
#endif
    if (p->weight != 1)
	storeAppendPrintf(sentry, " weight=%d", p->weight);
    if (p->options.closest_only)
	storeAppendPrintf(sentry, " closest-only");
    if (p->options.userhash)
	storeAppendPrintf(sentry, " userhash");
    if (p->options.sourcehash)
	storeAppendPrintf(sentry, " sourcehash");
#if USE_HTCP
    if (p->options.htcp)
	storeAppendPrintf(sentry, " htcp");
#endif
    if (p->options.no_netdb_exchange)
	storeAppendPrintf(sentry, " no-netdb-exchange");
#if DELAY_POOLS
    if (p->options.no_delay)
	storeAppendPrintf(sentry, " no-delay");
#endif
    if (p->login)
	storeAppendPrintf(sentry, " login=%s", p->login);
    if (p->mcast.ttl > 0)
	storeAppendPrintf(sentry, " ttl=%d", p->mcast.ttl);
    if (p->connect_timeout > 0)
	storeAppendPrintf(sentry, " connect-timeout=%d", (int) p->connect_timeout);
#if USE_CACHE_DIGESTS
    if (p->digest_url)
	storeAppendPrintf(sentry, " digest-url=%s", p->digest_url);
#endif
    if (p->options.allow_miss)
	storeAppendPrintf(sentry, " allow-miss");
    if (p->max_conn > 0)
	storeAppendPrintf(sentry, " max-conn=%d", p->max_conn);
    if (p->options.originserver)
	storeAppendPrintf(sentry, " originserver");
    /* name is used in the heading */
    if (p->monitor.url)
	storeAppendPrintf(sentry, " monitorurl=%s", p->monitor.url);
    if (p->monitor.min > 0 || p->monitor.max > 0) {
	if (p->monitor.max > 0)
	    storeAppendPrintf(sentry, " monitorsize=%d:%d", p->monitor.min, p->monitor.max);
	else
	    storeAppendPrintf(sentry, " monitorsize=%d", p->monitor.min);
    }
    if (p->domain)
	storeAppendPrintf(sentry, " forceddomain=%s", p->domain);
    storeAppendPrintf(sentry, "\n");
}

static void
dump_peers(StoreEntry * sentry, peer * peers)
{
    peer *e = NULL;
    struct _domain_ping *d = NULL;
    icp_opcode op;
    int i;
    if (peers == NULL)
	storeAppendPrintf(sentry, "There are no neighbors installed.\n");
    for (e = peers; e; e = e->next) {
	assert(e->host != NULL);
	storeAppendPrintf(sentry, "\n%-11.11s: %s\n",
	    neighborTypeStr(e),
	    e->name);
	storeAppendPrintf(sentry, "Host       : %s/%d/%d\n",
	    e->host,
	    e->http_port,
	    e->icp.port);
	storeAppendPrintf(sentry, "Flags      :");
	dump_peer_options(sentry, e);
	for (i = 0; i < e->n_addresses; i++) {
	    storeAppendPrintf(sentry, "Address[%d] : %s\n", i,
		inet_ntoa(e->addresses[i]));
	}
	storeAppendPrintf(sentry, "Status     : %s\n",
	    neighborUp(e) ? "Up" : "Down");
	storeAppendPrintf(sentry, "AVG RTT    : %d msec\n", e->stats.rtt);
	storeAppendPrintf(sentry, "OPEN CONNS : %d\n", e->stats.conn_open);
	if (!e->options.no_query) {
	    storeAppendPrintf(sentry, "LAST QUERY : %8d seconds ago\n",
		(int) (squid_curtime - e->stats.last_query));
	    if (e->stats.last_reply > 0)
		storeAppendPrintf(sentry, "LAST REPLY : %8d seconds ago\n",
		    (int) (squid_curtime - e->stats.last_reply));
	    else
		storeAppendPrintf(sentry, "LAST REPLY : none received\n");
	    storeAppendPrintf(sentry, "PINGS SENT : %8d\n", e->stats.pings_sent);
	    storeAppendPrintf(sentry, "PINGS ACKED: %8d %3d%%\n",
		e->stats.pings_acked,
		percent(e->stats.pings_acked, e->stats.pings_sent));
	}
	storeAppendPrintf(sentry, "FETCHES    : %8d %3d%%\n",
	    e->stats.fetches,
	    percent(e->stats.fetches, e->stats.pings_acked));
	storeAppendPrintf(sentry, "IGNORED    : %8d %3d%%\n",
	    e->stats.ignored_replies,
	    percent(e->stats.ignored_replies, e->stats.pings_acked));
	if (!e->options.no_query) {
	    storeAppendPrintf(sentry, "Histogram of PINGS ACKED:\n");
#if USE_HTCP
	    if (e->options.htcp) {
		storeAppendPrintf(sentry, "\tMisses\t%8d %3d%%\n",
		    e->htcp.counts[0],
		    percent(e->htcp.counts[0], e->stats.pings_acked));
		storeAppendPrintf(sentry, "\tHits\t%8d %3d%%\n",
		    e->htcp.counts[1],
		    percent(e->htcp.counts[1], e->stats.pings_acked));
	    } else {
#endif
		for (op = ICP_INVALID; op < ICP_END; op++) {
		    if (e->icp.counts[op] == 0)
			continue;
		    storeAppendPrintf(sentry, "    %12.12s : %8d %3d%%\n",
			icp_opcode_str[op],
			e->icp.counts[op],
			percent(e->icp.counts[op], e->stats.pings_acked));
		}
#if USE_HTCP
	    }
#endif
	}
	if (e->stats.last_connect_failure) {
	    storeAppendPrintf(sentry, "Last failed connect() at: %s\n",
		mkhttpdlogtime(&(e->stats.last_connect_failure)));
	}
	if (e->peer_domain != NULL) {
	    storeAppendPrintf(sentry, "DOMAIN LIST: ");
	    for (d = e->peer_domain; d; d = d->next) {
		storeAppendPrintf(sentry, "%s%s ",
		    d->do_ping ? null_string : "!", d->domain);
	    }
	    storeAppendPrintf(sentry, "\n");
	}
	storeAppendPrintf(sentry, "keep-alive ratio: %d%%\n",
	    percent(e->stats.n_keepalives_recv, e->stats.n_keepalives_sent));
    }
}

#if USE_HTCP
void
neighborsHtcpReply(const cache_key * key, htcpReplyData * htcp, const struct sockaddr_in *from)
{
    StoreEntry *e = storeGet(key);
    MemObject *mem = NULL;
    peer *p;
    peer_t ntype = PEER_NONE;
    debug(15, 6) ("neighborsHtcpReply: %s %s\n",
	htcp->hit ? "HIT" : "MISS", storeKeyText(key));
    if (NULL != (e = storeGet(key)))
	mem = e->mem_obj;
    if ((p = whichPeer(from)))
	neighborAliveHtcp(p, mem, htcp);
    /* Does the entry exist? */
    if (NULL == e) {
	debug(12, 3) ("neighborsHtcpReply: Cache key '%s' not found\n",
	    storeKeyText(key));
	neighborCountIgnored(p);
	return;
    }
    /* check if someone is already fetching it */
    if (EBIT_TEST(e->flags, ENTRY_DISPATCHED)) {
	debug(15, 3) ("neighborsHtcpReply: '%s' already being fetched.\n",
	    storeKeyText(key));
	neighborCountIgnored(p);
	return;
    }
    if (mem == NULL) {
	debug(15, 2) ("Ignoring reply for missing mem_obj: %s\n",
	    storeKeyText(key));
	neighborCountIgnored(p);
	return;
    }
    if (e->ping_status != PING_WAITING) {
	debug(15, 2) ("neighborsHtcpReply: Entry %s is not PING_WAITING\n",
	    storeKeyText(key));
	neighborCountIgnored(p);
	return;
    }
    if (e->lock_count == 0) {
	debug(12, 1) ("neighborsHtcpReply: '%s' has no locks\n",
	    storeKeyText(key));
	neighborCountIgnored(p);
	return;
    }
    if (p) {
	ntype = neighborType(p, mem->request);
	neighborUpdateRtt(p, mem);
    }
    if (ignoreMulticastReply(p, mem)) {
	neighborCountIgnored(p);
	return;
    }
    debug(15, 3) ("neighborsHtcpReply: e = %p\n", e);
    mem->ping_reply_callback(p, ntype, PROTO_HTCP, htcp, mem->ircb_data);
}
#endif