src/parsec/disk-image/parsec/parsec-benchmark/pkgs/libs/uptcpip/src/freebsd.netinet/tcp_hostcache.c - public/gem5-resources - Git at Google

 /*-
  * Copyright (c) 2002 Andre Oppermann, Internet Business Solutions AG
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. The name of the author may not be used to endorse or promote
  *    products derived from this software without specific prior written
  *    permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */

 /*
  * The tcp_hostcache moves the tcp-specific cached metrics from the routing
  * table to a dedicated structure indexed by the remote IP address.  It keeps
  * information on the measured TCP parameters of past TCP sessions to allow
  * better initial start values to be used with later connections to/from the
  * same source.  Depending on the network parameters (delay, bandwidth, max
  * MTU, congestion window) between local and remote sites, this can lead to
  * significant speed-ups for new TCP connections after the first one.
  *
  * Due to the tcp_hostcache, all TCP-specific metrics information in the
  * routing table have been removed.  The inpcb no longer keeps a pointer to
  * the routing entry, and protocol-initiated route cloning has been removed
  * as well.  With these changes, the routing table has gone back to being
  * more lightwight and only carries information related to packet forwarding.
  *
  * tcp_hostcache is designed for multiple concurrent access in SMP
  * environments and high contention.  All bucket rows have their own lock and
  * thus multiple lookups and modifies can be done at the same time as long as
  * they are in different bucket rows.  If a request for insertion of a new
  * record can't be satisfied, it simply returns an empty structure.  Nobody
  * and nothing outside of tcp_hostcache.c will ever point directly to any
  * entry in the tcp_hostcache.  All communication is done in an
  * object-oriented way and only functions of tcp_hostcache will manipulate
  * hostcache entries.  Otherwise, we are unable to achieve good behaviour in
  * concurrent access situations.  Since tcp_hostcache is only caching
  * information, there are no fatal consequences if we either can't satisfy
  * any particular request or have to drop/overwrite an existing entry because
  * of bucket limit memory constrains.
  */

 /*
  * Many thanks to jlemon for basic structure of tcp_syncache which is being
  * followed here.
  */

 #include <sys/bsd_cdefs.h>
 //__FBSDID("$FreeBSD$");

 #include "bsd_opt_inet6.h"

 #include <sys/bsd_param.h>
 #include <sys/bsd_systm.h>
 #include <sys/bsd_kernel.h>
 #include <sys/bsd_lock.h>
 #include <sys/bsd_mutex.h>
 #include <sys/bsd_malloc.h>
 #include <sys/bsd_socket.h>
 #include <sys/bsd_socketvar.h>
 //baoyg//#include <sys/bsd_sysctl.h>

 #include <net/bsd_if.h>
 #include <net/bsd_route.h>
 #include <net/bsd_vnet.h>

 #include <netinet/bsd_in.h>
 #include <netinet/bsd_in_systm.h>
 #include <netinet/bsd_ip.h>
 #include <netinet/bsd_in_var.h>
 #include <netinet/bsd_in_pcb.h>
 #include <netinet/bsd_ip_var.h>
 #ifdef INET6
 #include <netinet/bsd_ip6.h>
 #include <netinet6/bsd_ip6_var.h>
 #endif
 #include <netinet/bsd_tcp.h>
 #include <netinet/bsd_tcp_var.h>
 #include <netinet/bsd_tcp_hostcache.h>
 #ifdef INET6
 #include <netinet6/bsd_tcp6_var.h>
 #endif

 #include <vm/bsd_uma.h>
 extern int bsd_hz;

 /* Arbitrary values */
 #define TCP_HOSTCACHE_HASHSIZE		512
 #define TCP_HOSTCACHE_BUCKETLIMIT	30
 #define TCP_HOSTCACHE_EXPIRE		60*60	/* one hour */
 #define TCP_HOSTCACHE_PRUNE		5*60	/* every 5 minutes */

 static VNET_DEFINE(struct tcp_hostcache, tcp_hostcache);
 static VNET_DEFINE(struct callout, tcp_hc_callout);

 #define	V_tcp_hostcache		VNET(tcp_hostcache)
 #define	V_tcp_hc_callout	VNET(tcp_hc_callout)

 static struct hc_metrics *tcp_hc_lookup(struct in_conninfo *);
 static struct hc_metrics *tcp_hc_insert(struct in_conninfo *);
 //baoygstatic int sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS);
 static void tcp_hc_purge(void *);
 /*
 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, hostcache, CTLFLAG_RW, 0,
     "TCP Host cache");

 SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, cachelimit, CTLFLAG_RDTUN,
     &VNET_NAME(tcp_hostcache.cache_limit), 0,
     "Overall entry limit for hostcache");

 SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, hashsize, CTLFLAG_RDTUN,
     &VNET_NAME(tcp_hostcache.hashsize), 0,
     "Size of TCP hostcache hashtable");

 SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, bucketlimit,
     CTLFLAG_RDTUN, &VNET_NAME(tcp_hostcache.bucket_limit), 0,
     "Per-bucket hash limit for hostcache");

 SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, count, CTLFLAG_RD,
      &VNET_NAME(tcp_hostcache.cache_count), 0,
     "Current number of entries in hostcache");

 SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, expire, CTLFLAG_RW,
     &VNET_NAME(tcp_hostcache.expire), 0,
     "Expire time of TCP hostcache entries");

 SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, prune, CTLFLAG_RW,
     &VNET_NAME(tcp_hostcache.prune), 0,
     "Time between purge runs");

 SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, purge, CTLFLAG_RW,
     &VNET_NAME(tcp_hostcache.purgeall), 0,
     "Expire all entires on next purge run");

 SYSCTL_PROC(_net_inet_tcp_hostcache, OID_AUTO, list,
     CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_SKIP, 0, 0,
     sysctl_tcp_hc_list, "A", "List of all hostcache entries");
 */

 static MALLOC_DEFINE(M_HOSTCACHE, "hostcache", "TCP hostcache");

 #define HOSTCACHE_HASH(ip) \
 	(((ip)->s_addr ^ ((ip)->s_addr >> 7) ^ ((ip)->s_addr >> 17)) &	\
 	  V_tcp_hostcache.hashmask)

 /* XXX: What is the recommended hash to get good entropy for IPv6 addresses? */
 #define HOSTCACHE_HASH6(ip6)				\
 	(((ip6)->s6_addr32[0] ^				\
 	  (ip6)->s6_addr32[1] ^				\
 	  (ip6)->s6_addr32[2] ^				\
 	  (ip6)->s6_addr32[3]) &			\
 	 V_tcp_hostcache.hashmask)

 #define THC_LOCK(lp)		mtx_lock(lp)
 #define THC_UNLOCK(lp)		mtx_unlock(lp)

 void
 tcp_hc_init(void)
 {
 	int i;

 	/*
 	 * Initialize hostcache structures.
 	 */
 	V_tcp_hostcache.cache_count = 0;
 	V_tcp_hostcache.hashsize = TCP_HOSTCACHE_HASHSIZE;
 	V_tcp_hostcache.bucket_limit = TCP_HOSTCACHE_BUCKETLIMIT;
 	V_tcp_hostcache.cache_limit =
 	    V_tcp_hostcache.hashsize * V_tcp_hostcache.bucket_limit;
 	V_tcp_hostcache.expire = TCP_HOSTCACHE_EXPIRE;
 	V_tcp_hostcache.prune = TCP_HOSTCACHE_PRUNE;

 /*	TUNABLE_INT_FETCH("net.inet.tcp.hostcache.hashsize",
 	    &V_tcp_hostcache.hashsize);
 	TUNABLE_INT_FETCH("net.inet.tcp.hostcache.cachelimit",
 	    &V_tcp_hostcache.cache_limit);
 	TUNABLE_INT_FETCH("net.inet.tcp.hostcache.bucketlimit",
 	    &V_tcp_hostcache.bucket_limit);*/
 	if (!powerof2(V_tcp_hostcache.hashsize)) {
 		printf("WARNING: hostcache hash size is not a power of 2.\n");
 		V_tcp_hostcache.hashsize = TCP_HOSTCACHE_HASHSIZE; /* default */
 	}
 	V_tcp_hostcache.hashmask = V_tcp_hostcache.hashsize - 1;

 	/*
 	 * Allocate the hash table.
 	 */
 	V_tcp_hostcache.hashbase = (struct hc_head *)
 	    bsd_malloc(V_tcp_hostcache.hashsize * sizeof(struct hc_head),  M_HOSTCACHE, M_WAITOK | M_ZERO);

 	/*
 	 * Initialize the hash buckets.
 	 */
 	for (i = 0; i < V_tcp_hostcache.hashsize; i++) {
 		TAILQ_INIT(&V_tcp_hostcache.hashbase[i].hch_bucket);
 		V_tcp_hostcache.hashbase[i].hch_length = 0;
 		mtx_init(&V_tcp_hostcache.hashbase[i].hch_mtx, "tcp_hc_entry",
 			  NULL, MTX_DEF);
 	}

 	/*
 	 * Allocate the hostcache entries.
 	 */
 	V_tcp_hostcache.zone =
 	    uma_zcreate("hostcache", sizeof(struct hc_metrics),
 	    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
 	uma_zone_set_max(V_tcp_hostcache.zone, V_tcp_hostcache.cache_limit);

 	/*
 	 * Set up periodic cache cleanup.
 	 */
 	callout_init(&V_tcp_hc_callout, CALLOUT_MPSAFE);
 	callout_reset(&V_tcp_hc_callout, V_tcp_hostcache.prune * bsd_hz,
 	    tcp_hc_purge, curvnet);
 }

 #ifdef VIMAGE
 void
 tcp_hc_destroy(void)
 {

 	/* XXX TODO walk the hashtable and free all entries  */

 	callout_drain(&V_tcp_hc_callout);
 }
 #endif

 /*
  * Internal function: look up an entry in the hostcache or return NULL.
  *
  * If an entry has been returned, the caller becomes responsible for
  * unlocking the bucket row after he is done reading/modifying the entry.
  */
 static struct hc_metrics *
 tcp_hc_lookup(struct in_conninfo *inc)
 {
 	int hash;
 	struct hc_head *hc_head;
 	struct hc_metrics *hc_entry;

 	KASSERT(inc != NULL, ("tcp_hc_lookup with NULL in_conninfo pointer"));

 	/*
 	 * Hash the foreign ip address.
 	 */
 	if (inc->inc_flags & INC_ISIPV6)
 		hash = HOSTCACHE_HASH6(&inc->inc6_faddr);
 	else
 		hash = HOSTCACHE_HASH(&inc->inc_faddr);

 	hc_head = &V_tcp_hostcache.hashbase[hash];

 	/*
 	 * Acquire lock for this bucket row; we release the lock if we don't
 	 * find an entry, otherwise the caller has to unlock after he is
 	 * done.
 	 */
 	THC_LOCK(&hc_head->hch_mtx);

 	/*
 	 * Iterate through entries in bucket row looking for a match.
 	 */
 	TAILQ_FOREACH(hc_entry, &hc_head->hch_bucket, rmx_q) {
 		if (inc->inc_flags & INC_ISIPV6) {
 			if (memcmp(&inc->inc6_faddr, &hc_entry->ip6,
 			    sizeof(inc->inc6_faddr)) == 0)
 				return hc_entry;
 		} else {
 			if (memcmp(&inc->inc_faddr, &hc_entry->ip4,
 			    sizeof(inc->inc_faddr)) == 0)
 				return hc_entry;
 		}
 	}

 	/*
 	 * We were unsuccessful and didn't find anything.
 	 */
 	THC_UNLOCK(&hc_head->hch_mtx);
 	return NULL;
 }

 /*
  * Internal function: insert an entry into the hostcache or return NULL if
  * unable to allocate a new one.
  *
  * If an entry has been returned, the caller becomes responsible for
  * unlocking the bucket row after he is done reading/modifying the entry.
  */
 static struct hc_metrics *
 tcp_hc_insert(struct in_conninfo *inc)
 {
 	int hash;
 	struct hc_head *hc_head;
 	struct hc_metrics *hc_entry;

 	KASSERT(inc != NULL, ("tcp_hc_insert with NULL in_conninfo pointer"));

 	/*
 	 * Hash the foreign ip address.
 	 */
 	if (inc->inc_flags & INC_ISIPV6)
 		hash = HOSTCACHE_HASH6(&inc->inc6_faddr);
 	else
 		hash = HOSTCACHE_HASH(&inc->inc_faddr);

 	hc_head = &V_tcp_hostcache.hashbase[hash];

 	/*
 	 * Acquire lock for this bucket row; we release the lock if we don't
 	 * find an entry, otherwise the caller has to unlock after he is
 	 * done.
 	 */
 	THC_LOCK(&hc_head->hch_mtx);

 	/*
 	 * If the bucket limit is reached, reuse the least-used element.
 	 */
 	if (hc_head->hch_length >= V_tcp_hostcache.bucket_limit ||
 	    V_tcp_hostcache.cache_count >= V_tcp_hostcache.cache_limit) {
 		hc_entry = TAILQ_LAST(&hc_head->hch_bucket, hc_qhead);
 		/*
 		 * At first we were dropping the last element, just to
 		 * reacquire it in the next two lines again, which isn't very
 		 * efficient.  Instead just reuse the least used element.
 		 * We may drop something that is still "in-use" but we can be
 		 * "lossy".
 		 * Just give up if this bucket row is empty and we don't have
 		 * anything to replace.
 		 */
 		if (hc_entry == NULL) {
 			THC_UNLOCK(&hc_head->hch_mtx);
 			return NULL;
 		}
 		TAILQ_REMOVE(&hc_head->hch_bucket, hc_entry, rmx_q);
 		V_tcp_hostcache.hashbase[hash].hch_length--;
 		V_tcp_hostcache.cache_count--;
 		TCPSTAT_INC(tcps_hc_bucketoverflow);
 #if 0
 		uma_zfree(V_tcp_hostcache.zone, hc_entry);
 #endif
 	} else {
 		/*
 		 * Allocate a new entry, or balk if not possible.
 		 */
 		hc_entry = uma_zalloc(V_tcp_hostcache.zone, M_NOWAIT);
 		if (hc_entry == NULL) {
 			THC_UNLOCK(&hc_head->hch_mtx);
 			return NULL;
 		}
 	}

 	/*
 	 * Initialize basic information of hostcache entry.
 	 */
 	bzero(hc_entry, sizeof(*hc_entry));
 	if (inc->inc_flags & INC_ISIPV6)
 		bcopy(&inc->inc6_faddr, &hc_entry->ip6, sizeof(hc_entry->ip6));
 	else
 		hc_entry->ip4 = inc->inc_faddr;
 	hc_entry->rmx_head = hc_head;
 	hc_entry->rmx_expire = V_tcp_hostcache.expire;

 	/*
 	 * Put it upfront.
 	 */
 	TAILQ_INSERT_HEAD(&hc_head->hch_bucket, hc_entry, rmx_q);
 	V_tcp_hostcache.hashbase[hash].hch_length++;
 	V_tcp_hostcache.cache_count++;
 	TCPSTAT_INC(tcps_hc_added);

 	return hc_entry;
 }

 /*
  * External function: look up an entry in the hostcache and fill out the
  * supplied TCP metrics structure.  Fills in NULL when no entry was found or
  * a value is not set.
  */
 void
 tcp_hc_get(struct in_conninfo *inc, struct hc_metrics_lite *hc_metrics_lite)
 {
 	struct hc_metrics *hc_entry;

 	/*
 	 * Find the right bucket.
 	 */
 	hc_entry = tcp_hc_lookup(inc);

 	/*
 	 * If we don't have an existing object.
 	 */
 	if (hc_entry == NULL) {
 		bzero(hc_metrics_lite, sizeof(*hc_metrics_lite));
 		return;
 	}
 	hc_entry->rmx_hits++;
 	hc_entry->rmx_expire = V_tcp_hostcache.expire; /* start over again */

 	hc_metrics_lite->rmx_mtu = hc_entry->rmx_mtu;
 	hc_metrics_lite->rmx_ssthresh = hc_entry->rmx_ssthresh;
 	hc_metrics_lite->rmx_rtt = hc_entry->rmx_rtt;
 	hc_metrics_lite->rmx_rttvar = hc_entry->rmx_rttvar;
 	hc_metrics_lite->rmx_bandwidth = hc_entry->rmx_bandwidth;
 	hc_metrics_lite->rmx_cwnd = hc_entry->rmx_cwnd;
 	hc_metrics_lite->rmx_sendpipe = hc_entry->rmx_sendpipe;
 	hc_metrics_lite->rmx_recvpipe = hc_entry->rmx_recvpipe;

 	/*
 	 * Unlock bucket row.
 	 */
 	THC_UNLOCK(&hc_entry->rmx_head->hch_mtx);
 }

 /*
  * External function: look up an entry in the hostcache and return the
  * discovered path MTU.  Returns NULL if no entry is found or value is not
  * set.
  */
 u_long
 tcp_hc_getmtu(struct in_conninfo *inc)
 {
 	struct hc_metrics *hc_entry;
 	u_long mtu;

 	hc_entry = tcp_hc_lookup(inc);
 	if (hc_entry == NULL) {
 		return 0;
 	}
 	hc_entry->rmx_hits++;
 	hc_entry->rmx_expire = V_tcp_hostcache.expire; /* start over again */

 	mtu = hc_entry->rmx_mtu;
 	THC_UNLOCK(&hc_entry->rmx_head->hch_mtx);
 	return mtu;
 }

 /*
  * External function: update the MTU value of an entry in the hostcache.
  * Creates a new entry if none was found.
  */
 void
 tcp_hc_updatemtu(struct in_conninfo *inc, u_long mtu)
 {
 	struct hc_metrics *hc_entry;

 	/*
 	 * Find the right bucket.
 	 */
 	hc_entry = tcp_hc_lookup(inc);

 	/*
 	 * If we don't have an existing object, try to insert a new one.
 	 */
 	if (hc_entry == NULL) {
 		hc_entry = tcp_hc_insert(inc);
 		if (hc_entry == NULL)
 			return;
 	}
 	hc_entry->rmx_updates++;
 	hc_entry->rmx_expire = V_tcp_hostcache.expire; /* start over again */

 	hc_entry->rmx_mtu = mtu;

 	/*
 	 * Put it upfront so we find it faster next time.
 	 */
 	TAILQ_REMOVE(&hc_entry->rmx_head->hch_bucket, hc_entry, rmx_q);
 	TAILQ_INSERT_HEAD(&hc_entry->rmx_head->hch_bucket, hc_entry, rmx_q);

 	/*
 	 * Unlock bucket row.
 	 */
 	THC_UNLOCK(&hc_entry->rmx_head->hch_mtx);
 }

 /*
  * External function: update the TCP metrics of an entry in the hostcache.
  * Creates a new entry if none was found.
  */
 void
 tcp_hc_update(struct in_conninfo *inc, struct hc_metrics_lite *hcml)
 {
 	struct hc_metrics *hc_entry;

 	hc_entry = tcp_hc_lookup(inc);
 	if (hc_entry == NULL) {
 		hc_entry = tcp_hc_insert(inc);
 		if (hc_entry == NULL)
 			return;
 	}
 	hc_entry->rmx_updates++;
 	hc_entry->rmx_expire = V_tcp_hostcache.expire; /* start over again */

 	if (hcml->rmx_rtt != 0) {
 		if (hc_entry->rmx_rtt == 0)
 			hc_entry->rmx_rtt = hcml->rmx_rtt;
 		else
 			hc_entry->rmx_rtt =
 			    (hc_entry->rmx_rtt + hcml->rmx_rtt) / 2;
 		TCPSTAT_INC(tcps_cachedrtt);
 	}
 	if (hcml->rmx_rttvar != 0) {
 	        if (hc_entry->rmx_rttvar == 0)
 			hc_entry->rmx_rttvar = hcml->rmx_rttvar;
 		else
 			hc_entry->rmx_rttvar =
 			    (hc_entry->rmx_rttvar + hcml->rmx_rttvar) / 2;
 		TCPSTAT_INC(tcps_cachedrttvar);
 	}
 	if (hcml->rmx_ssthresh != 0) {
 		if (hc_entry->rmx_ssthresh == 0)
 			hc_entry->rmx_ssthresh = hcml->rmx_ssthresh;
 		else
 			hc_entry->rmx_ssthresh =
 			    (hc_entry->rmx_ssthresh + hcml->rmx_ssthresh) / 2;
 		TCPSTAT_INC(tcps_cachedssthresh);
 	}
 	if (hcml->rmx_bandwidth != 0) {
 		if (hc_entry->rmx_bandwidth == 0)
 			hc_entry->rmx_bandwidth = hcml->rmx_bandwidth;
 		else
 			hc_entry->rmx_bandwidth =
 			    (hc_entry->rmx_bandwidth + hcml->rmx_bandwidth) / 2;
 		/* TCPSTAT_INC(tcps_cachedbandwidth); */
 	}
 	if (hcml->rmx_cwnd != 0) {
 		if (hc_entry->rmx_cwnd == 0)
 			hc_entry->rmx_cwnd = hcml->rmx_cwnd;
 		else
 			hc_entry->rmx_cwnd =
 			    (hc_entry->rmx_cwnd + hcml->rmx_cwnd) / 2;
 		/* TCPSTAT_INC(tcps_cachedcwnd); */
 	}
 	if (hcml->rmx_sendpipe != 0) {
 		if (hc_entry->rmx_sendpipe == 0)
 			hc_entry->rmx_sendpipe = hcml->rmx_sendpipe;
 		else
 			hc_entry->rmx_sendpipe =
 			    (hc_entry->rmx_sendpipe + hcml->rmx_sendpipe) /2;
 		/* TCPSTAT_INC(tcps_cachedsendpipe); */
 	}
 	if (hcml->rmx_recvpipe != 0) {
 		if (hc_entry->rmx_recvpipe == 0)
 			hc_entry->rmx_recvpipe = hcml->rmx_recvpipe;
 		else
 			hc_entry->rmx_recvpipe =
 			    (hc_entry->rmx_recvpipe + hcml->rmx_recvpipe) /2;
 		/* TCPSTAT_INC(tcps_cachedrecvpipe); */
 	}

 	TAILQ_REMOVE(&hc_entry->rmx_head->hch_bucket, hc_entry, rmx_q);
 	TAILQ_INSERT_HEAD(&hc_entry->rmx_head->hch_bucket, hc_entry, rmx_q);
 	THC_UNLOCK(&hc_entry->rmx_head->hch_mtx);
 }

 /*
  * Sysctl function: prints the list and values of all hostcache entries in
  * unsorted order.
  */
 /*
 static int
 sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS)
 {
 	int bufsize;
 	int linesize = 128;
 	char *p, *buf;
 	int len, i, error;
 	struct hc_metrics *hc_entry;
 #ifdef INET6
 	char ip6buf[INET6_ADDRSTRLEN];
 #endif

 	bufsize = linesize * (V_tcp_hostcache.cache_count + 1);

 	p = buf = (char *)bsd_malloc(bufsize, M_TEMP, M_WAITOK|M_ZERO);

 	len = snprintf(p, linesize,
 		"\nIP address        MTU  SSTRESH      RTT   RTTVAR BANDWIDTH "
 		"    CWND SENDPIPE RECVPIPE HITS  UPD  EXP\n");
 	p += len;

 #define msec(u) (((u) + 500) / 1000)
 	for (i = 0; i < V_tcp_hostcache.hashsize; i++) {
 		THC_LOCK(&V_tcp_hostcache.hashbase[i].hch_mtx);
 		TAILQ_FOREACH(hc_entry, &V_tcp_hostcache.hashbase[i].hch_bucket,
 			      rmx_q) {
 			len = snprintf(p, linesize,
 			    "%-15s %5lu %8lu %6lums %6lums %9lu %8lu %8lu %8lu "
 			    "%4lu %4lu %4i\n",
 			    hc_entry->ip4.s_addr ? inet_ntoa(hc_entry->ip4) :
 #ifdef INET6
 				ip6_sprintf(ip6buf, &hc_entry->ip6),
 #else
 				"IPv6?",
 #endif
 			    hc_entry->rmx_mtu,
 			    hc_entry->rmx_ssthresh,
 			    msec(hc_entry->rmx_rtt *
 				(RTM_RTTUNIT / (bsd_hz * TCP_RTT_SCALE))),
 			    msec(hc_entry->rmx_rttvar *
 				(RTM_RTTUNIT / (bsd_hz * TCP_RTT_SCALE))),
 			    hc_entry->rmx_bandwidth * 8,
 			    hc_entry->rmx_cwnd,
 			    hc_entry->rmx_sendpipe,
 			    hc_entry->rmx_recvpipe,
 			    hc_entry->rmx_hits,
 			    hc_entry->rmx_updates,
 			    hc_entry->rmx_expire);
 			p += len;
 		}
 		THC_UNLOCK(&V_tcp_hostcache.hashbase[i].hch_mtx);
 	}
 #undef msec
 	error = SYSCTL_OUT(req, buf, p - buf);
 	free(buf, M_TEMP);
 	return(error);
 }
 */
 /*
  * Expire and purge (old|all) entries in the tcp_hostcache.  Runs
  * periodically from the callout.
  */
 static void
 tcp_hc_purge(void *arg)
 {
 	CURVNET_SET((struct vnet *) arg);
 	struct hc_metrics *hc_entry, *hc_next;
 	int all = 0;
 	int i;

 	if (V_tcp_hostcache.purgeall) {
 		all = 1;
 		V_tcp_hostcache.purgeall = 0;
 	}

 	for (i = 0; i < V_tcp_hostcache.hashsize; i++) {
 		THC_LOCK(&V_tcp_hostcache.hashbase[i].hch_mtx);
 		TAILQ_FOREACH_SAFE(hc_entry,
 		    &V_tcp_hostcache.hashbase[i].hch_bucket, rmx_q, hc_next) {
 			if (all || hc_entry->rmx_expire <= 0) {
 				TAILQ_REMOVE(&V_tcp_hostcache.hashbase[i].hch_bucket,
 					      hc_entry, rmx_q);
 				uma_zfree(V_tcp_hostcache.zone, hc_entry);
 				V_tcp_hostcache.hashbase[i].hch_length--;
 				V_tcp_hostcache.cache_count--;
 			} else
 				hc_entry->rmx_expire -= V_tcp_hostcache.prune;
 		}
 		THC_UNLOCK(&V_tcp_hostcache.hashbase[i].hch_mtx);
 	}

 	callout_reset(&V_tcp_hc_callout, V_tcp_hostcache.prune * bsd_hz,
 	    tcp_hc_purge, arg);
 	CURVNET_RESTORE();
 }
	/*-
	* Copyright (c) 2002 Andre Oppermann, Internet Business Solutions AG
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 3. The name of the author may not be used to endorse or promote
	* products derived from this software without specific prior written
	* permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	* SUCH DAMAGE.
	*/

	/*
	* The tcp_hostcache moves the tcp-specific cached metrics from the routing
	* table to a dedicated structure indexed by the remote IP address. It keeps
	* information on the measured TCP parameters of past TCP sessions to allow
	* better initial start values to be used with later connections to/from the
	* same source. Depending on the network parameters (delay, bandwidth, max
	* MTU, congestion window) between local and remote sites, this can lead to
	* significant speed-ups for new TCP connections after the first one.
	*
	* Due to the tcp_hostcache, all TCP-specific metrics information in the
	* routing table have been removed. The inpcb no longer keeps a pointer to
	* the routing entry, and protocol-initiated route cloning has been removed
	* as well. With these changes, the routing table has gone back to being
	* more lightwight and only carries information related to packet forwarding.
	*
	* tcp_hostcache is designed for multiple concurrent access in SMP
	* environments and high contention. All bucket rows have their own lock and
	* thus multiple lookups and modifies can be done at the same time as long as
	* they are in different bucket rows. If a request for insertion of a new
	* record can't be satisfied, it simply returns an empty structure. Nobody
	* and nothing outside of tcp_hostcache.c will ever point directly to any
	* entry in the tcp_hostcache. All communication is done in an
	* object-oriented way and only functions of tcp_hostcache will manipulate
	* hostcache entries. Otherwise, we are unable to achieve good behaviour in
	* concurrent access situations. Since tcp_hostcache is only caching
	* information, there are no fatal consequences if we either can't satisfy
	* any particular request or have to drop/overwrite an existing entry because
	* of bucket limit memory constrains.
	*/

	/*
	* Many thanks to jlemon for basic structure of tcp_syncache which is being
	* followed here.
	*/

	#include <sys/bsd_cdefs.h>
	//__FBSDID("$FreeBSD$");

	#include "bsd_opt_inet6.h"

	#include <sys/bsd_param.h>
	#include <sys/bsd_systm.h>
	#include <sys/bsd_kernel.h>
	#include <sys/bsd_lock.h>
	#include <sys/bsd_mutex.h>
	#include <sys/bsd_malloc.h>
	#include <sys/bsd_socket.h>
	#include <sys/bsd_socketvar.h>
	//baoyg//#include <sys/bsd_sysctl.h>

	#include <net/bsd_if.h>
	#include <net/bsd_route.h>
	#include <net/bsd_vnet.h>

	#include <netinet/bsd_in.h>
	#include <netinet/bsd_in_systm.h>
	#include <netinet/bsd_ip.h>
	#include <netinet/bsd_in_var.h>
	#include <netinet/bsd_in_pcb.h>
	#include <netinet/bsd_ip_var.h>
	#ifdef INET6
	#include <netinet/bsd_ip6.h>
	#include <netinet6/bsd_ip6_var.h>
	#endif
	#include <netinet/bsd_tcp.h>
	#include <netinet/bsd_tcp_var.h>
	#include <netinet/bsd_tcp_hostcache.h>
	#ifdef INET6
	#include <netinet6/bsd_tcp6_var.h>
	#endif

	#include <vm/bsd_uma.h>
	extern int bsd_hz;

	/* Arbitrary values */
	#define TCP_HOSTCACHE_HASHSIZE 512
	#define TCP_HOSTCACHE_BUCKETLIMIT 30
	#define TCP_HOSTCACHE_EXPIRE 6060 / one hour */
	#define TCP_HOSTCACHE_PRUNE 560 / every 5 minutes */

	static VNET_DEFINE(struct tcp_hostcache, tcp_hostcache);
	static VNET_DEFINE(struct callout, tcp_hc_callout);

	#define V_tcp_hostcache VNET(tcp_hostcache)
	#define V_tcp_hc_callout VNET(tcp_hc_callout)

	static struct hc_metrics tcp_hc_lookup(struct in_conninfo );
	static struct hc_metrics tcp_hc_insert(struct in_conninfo );
	//baoygstatic int sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS);
	static void tcp_hc_purge(void *);
	/*
	SYSCTL_NODE(_net_inet_tcp, OID_AUTO, hostcache, CTLFLAG_RW, 0,
	"TCP Host cache");

	SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, cachelimit, CTLFLAG_RDTUN,
	&VNET_NAME(tcp_hostcache.cache_limit), 0,
	"Overall entry limit for hostcache");

	SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, hashsize, CTLFLAG_RDTUN,
	&VNET_NAME(tcp_hostcache.hashsize), 0,
	"Size of TCP hostcache hashtable");

	SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, bucketlimit,
	CTLFLAG_RDTUN, &VNET_NAME(tcp_hostcache.bucket_limit), 0,
	"Per-bucket hash limit for hostcache");

	SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, count, CTLFLAG_RD,
	&VNET_NAME(tcp_hostcache.cache_count), 0,
	"Current number of entries in hostcache");

	SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, expire, CTLFLAG_RW,
	&VNET_NAME(tcp_hostcache.expire), 0,
	"Expire time of TCP hostcache entries");

	SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, prune, CTLFLAG_RW,
	&VNET_NAME(tcp_hostcache.prune), 0,
	"Time between purge runs");

	SYSCTL_VNET_INT(_net_inet_tcp_hostcache, OID_AUTO, purge, CTLFLAG_RW,
	&VNET_NAME(tcp_hostcache.purgeall), 0,
	"Expire all entires on next purge run");

	SYSCTL_PROC(_net_inet_tcp_hostcache, OID_AUTO, list,
	CTLTYPE_STRING \| CTLFLAG_RD \| CTLFLAG_SKIP, 0, 0,
	sysctl_tcp_hc_list, "A", "List of all hostcache entries");
	*/

	static MALLOC_DEFINE(M_HOSTCACHE, "hostcache", "TCP hostcache");

	#define HOSTCACHE_HASH(ip) \
	(((ip)->s_addr ^ ((ip)->s_addr >> 7) ^ ((ip)->s_addr >> 17)) & \
	V_tcp_hostcache.hashmask)

	/* XXX: What is the recommended hash to get good entropy for IPv6 addresses? */
	#define HOSTCACHE_HASH6(ip6) \
	(((ip6)->s6_addr32[0] ^ \
	(ip6)->s6_addr32[1] ^ \
	(ip6)->s6_addr32[2] ^ \
	(ip6)->s6_addr32[3]) & \
	V_tcp_hostcache.hashmask)

	#define THC_LOCK(lp) mtx_lock(lp)
	#define THC_UNLOCK(lp) mtx_unlock(lp)

	void
	tcp_hc_init(void)
	{
	int i;

	/*
	* Initialize hostcache structures.
	*/
	V_tcp_hostcache.cache_count = 0;
	V_tcp_hostcache.hashsize = TCP_HOSTCACHE_HASHSIZE;
	V_tcp_hostcache.bucket_limit = TCP_HOSTCACHE_BUCKETLIMIT;
	V_tcp_hostcache.cache_limit =
	V_tcp_hostcache.hashsize * V_tcp_hostcache.bucket_limit;
	V_tcp_hostcache.expire = TCP_HOSTCACHE_EXPIRE;
	V_tcp_hostcache.prune = TCP_HOSTCACHE_PRUNE;

	/* TUNABLE_INT_FETCH("net.inet.tcp.hostcache.hashsize",
	&V_tcp_hostcache.hashsize);
	TUNABLE_INT_FETCH("net.inet.tcp.hostcache.cachelimit",
	&V_tcp_hostcache.cache_limit);
	TUNABLE_INT_FETCH("net.inet.tcp.hostcache.bucketlimit",
	&V_tcp_hostcache.bucket_limit);*/
	if (!powerof2(V_tcp_hostcache.hashsize)) {
	printf("WARNING: hostcache hash size is not a power of 2.\n");
	V_tcp_hostcache.hashsize = TCP_HOSTCACHE_HASHSIZE; /* default */
	}
	V_tcp_hostcache.hashmask = V_tcp_hostcache.hashsize - 1;

	/*
	* Allocate the hash table.
	*/
	V_tcp_hostcache.hashbase = (struct hc_head *)
	bsd_malloc(V_tcp_hostcache.hashsize * sizeof(struct hc_head), M_HOSTCACHE, M_WAITOK \| M_ZERO);

	/*
	* Initialize the hash buckets.
	*/
	for (i = 0; i < V_tcp_hostcache.hashsize; i++) {
	TAILQ_INIT(&V_tcp_hostcache.hashbase[i].hch_bucket);
	V_tcp_hostcache.hashbase[i].hch_length = 0;
	mtx_init(&V_tcp_hostcache.hashbase[i].hch_mtx, "tcp_hc_entry",
	NULL, MTX_DEF);
	}

	/*
	* Allocate the hostcache entries.
	*/
	V_tcp_hostcache.zone =
	uma_zcreate("hostcache", sizeof(struct hc_metrics),
	NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
	uma_zone_set_max(V_tcp_hostcache.zone, V_tcp_hostcache.cache_limit);

	/*
	* Set up periodic cache cleanup.
	*/
	callout_init(&V_tcp_hc_callout, CALLOUT_MPSAFE);
	callout_reset(&V_tcp_hc_callout, V_tcp_hostcache.prune * bsd_hz,
	tcp_hc_purge, curvnet);
	}

	#ifdef VIMAGE
	void
	tcp_hc_destroy(void)
	{

	/* XXX TODO walk the hashtable and free all entries */

	callout_drain(&V_tcp_hc_callout);
	}
	#endif

	/*
	* Internal function: look up an entry in the hostcache or return NULL.
	*
	* If an entry has been returned, the caller becomes responsible for
	* unlocking the bucket row after he is done reading/modifying the entry.
	*/
	static struct hc_metrics *
	tcp_hc_lookup(struct in_conninfo *inc)
	{
	int hash;
	struct hc_head *hc_head;
	struct hc_metrics *hc_entry;

	KASSERT(inc != NULL, ("tcp_hc_lookup with NULL in_conninfo pointer"));

	/*
	* Hash the foreign ip address.
	*/
	if (inc->inc_flags & INC_ISIPV6)
	hash = HOSTCACHE_HASH6(&inc->inc6_faddr);
	else
	hash = HOSTCACHE_HASH(&inc->inc_faddr);

	hc_head = &V_tcp_hostcache.hashbase[hash];

	/*
	* Acquire lock for this bucket row; we release the lock if we don't
	* find an entry, otherwise the caller has to unlock after he is
	* done.
	*/
	THC_LOCK(&hc_head->hch_mtx);

	/*
	* Iterate through entries in bucket row looking for a match.
	*/
	TAILQ_FOREACH(hc_entry, &hc_head->hch_bucket, rmx_q) {
	if (inc->inc_flags & INC_ISIPV6) {
	if (memcmp(&inc->inc6_faddr, &hc_entry->ip6,
	sizeof(inc->inc6_faddr)) == 0)
	return hc_entry;
	} else {
	if (memcmp(&inc->inc_faddr, &hc_entry->ip4,
	sizeof(inc->inc_faddr)) == 0)
	return hc_entry;
	}
	}

	/*
	* We were unsuccessful and didn't find anything.
	*/
	THC_UNLOCK(&hc_head->hch_mtx);
	return NULL;
	}

	/*
	* Internal function: insert an entry into the hostcache or return NULL if
	* unable to allocate a new one.
	*
	* If an entry has been returned, the caller becomes responsible for
	* unlocking the bucket row after he is done reading/modifying the entry.
	*/
	static struct hc_metrics *
	tcp_hc_insert(struct in_conninfo *inc)
	{
	int hash;
	struct hc_head *hc_head;
	struct hc_metrics *hc_entry;

	KASSERT(inc != NULL, ("tcp_hc_insert with NULL in_conninfo pointer"));

	/*
	* Hash the foreign ip address.
	*/
	if (inc->inc_flags & INC_ISIPV6)
	hash = HOSTCACHE_HASH6(&inc->inc6_faddr);
	else
	hash = HOSTCACHE_HASH(&inc->inc_faddr);

	hc_head = &V_tcp_hostcache.hashbase[hash];

	/*
	* Acquire lock for this bucket row; we release the lock if we don't
	* find an entry, otherwise the caller has to unlock after he is
	* done.
	*/
	THC_LOCK(&hc_head->hch_mtx);

	/*
	* If the bucket limit is reached, reuse the least-used element.
	*/
	if (hc_head->hch_length >= V_tcp_hostcache.bucket_limit \|\|
	V_tcp_hostcache.cache_count >= V_tcp_hostcache.cache_limit) {
	hc_entry = TAILQ_LAST(&hc_head->hch_bucket, hc_qhead);
	/*
	* At first we were dropping the last element, just to
	* reacquire it in the next two lines again, which isn't very
	* efficient. Instead just reuse the least used element.
	* We may drop something that is still "in-use" but we can be
	* "lossy".
	* Just give up if this bucket row is empty and we don't have
	* anything to replace.
	*/
	if (hc_entry == NULL) {
	THC_UNLOCK(&hc_head->hch_mtx);
	return NULL;
	}
	TAILQ_REMOVE(&hc_head->hch_bucket, hc_entry, rmx_q);
	V_tcp_hostcache.hashbase[hash].hch_length--;
	V_tcp_hostcache.cache_count--;
	TCPSTAT_INC(tcps_hc_bucketoverflow);
	#if 0
	uma_zfree(V_tcp_hostcache.zone, hc_entry);
	#endif
	} else {
	/*
	* Allocate a new entry, or balk if not possible.
	*/
	hc_entry = uma_zalloc(V_tcp_hostcache.zone, M_NOWAIT);
	if (hc_entry == NULL) {
	THC_UNLOCK(&hc_head->hch_mtx);
	return NULL;
	}
	}

	/*
	* Initialize basic information of hostcache entry.
	*/
	bzero(hc_entry, sizeof(*hc_entry));
	if (inc->inc_flags & INC_ISIPV6)
	bcopy(&inc->inc6_faddr, &hc_entry->ip6, sizeof(hc_entry->ip6));
	else
	hc_entry->ip4 = inc->inc_faddr;
	hc_entry->rmx_head = hc_head;
	hc_entry->rmx_expire = V_tcp_hostcache.expire;

	/*
	* Put it upfront.
	*/
	TAILQ_INSERT_HEAD(&hc_head->hch_bucket, hc_entry, rmx_q);
	V_tcp_hostcache.hashbase[hash].hch_length++;
	V_tcp_hostcache.cache_count++;
	TCPSTAT_INC(tcps_hc_added);

	return hc_entry;
	}

	/*
	* External function: look up an entry in the hostcache and fill out the
	* supplied TCP metrics structure. Fills in NULL when no entry was found or
	* a value is not set.
	*/
	void
	tcp_hc_get(struct in_conninfo inc, struct hc_metrics_lite hc_metrics_lite)
	{
	struct hc_metrics *hc_entry;

	/*
	* Find the right bucket.
	*/
	hc_entry = tcp_hc_lookup(inc);

	/*
	* If we don't have an existing object.
	*/
	if (hc_entry == NULL) {
	bzero(hc_metrics_lite, sizeof(*hc_metrics_lite));
	return;
	}
	hc_entry->rmx_hits++;
	hc_entry->rmx_expire = V_tcp_hostcache.expire; /* start over again */

	hc_metrics_lite->rmx_mtu = hc_entry->rmx_mtu;
	hc_metrics_lite->rmx_ssthresh = hc_entry->rmx_ssthresh;
	hc_metrics_lite->rmx_rtt = hc_entry->rmx_rtt;
	hc_metrics_lite->rmx_rttvar = hc_entry->rmx_rttvar;
	hc_metrics_lite->rmx_bandwidth = hc_entry->rmx_bandwidth;
	hc_metrics_lite->rmx_cwnd = hc_entry->rmx_cwnd;
	hc_metrics_lite->rmx_sendpipe = hc_entry->rmx_sendpipe;
	hc_metrics_lite->rmx_recvpipe = hc_entry->rmx_recvpipe;

	/*
	* Unlock bucket row.
	*/
	THC_UNLOCK(&hc_entry->rmx_head->hch_mtx);
	}

	/*
	* External function: look up an entry in the hostcache and return the
	* discovered path MTU. Returns NULL if no entry is found or value is not
	* set.
	*/
	u_long
	tcp_hc_getmtu(struct in_conninfo *inc)
	{
	struct hc_metrics *hc_entry;
	u_long mtu;

	hc_entry = tcp_hc_lookup(inc);
	if (hc_entry == NULL) {
	return 0;
	}
	hc_entry->rmx_hits++;
	hc_entry->rmx_expire = V_tcp_hostcache.expire; /* start over again */

	mtu = hc_entry->rmx_mtu;
	THC_UNLOCK(&hc_entry->rmx_head->hch_mtx);
	return mtu;
	}

	/*
	* External function: update the MTU value of an entry in the hostcache.
	* Creates a new entry if none was found.
	*/
	void
	tcp_hc_updatemtu(struct in_conninfo *inc, u_long mtu)
	{
	struct hc_metrics *hc_entry;

	/*
	* Find the right bucket.
	*/
	hc_entry = tcp_hc_lookup(inc);

	/*
	* If we don't have an existing object, try to insert a new one.
	*/
	if (hc_entry == NULL) {
	hc_entry = tcp_hc_insert(inc);
	if (hc_entry == NULL)
	return;
	}
	hc_entry->rmx_updates++;
	hc_entry->rmx_expire = V_tcp_hostcache.expire; /* start over again */

	hc_entry->rmx_mtu = mtu;

	/*
	* Put it upfront so we find it faster next time.
	*/
	TAILQ_REMOVE(&hc_entry->rmx_head->hch_bucket, hc_entry, rmx_q);
	TAILQ_INSERT_HEAD(&hc_entry->rmx_head->hch_bucket, hc_entry, rmx_q);

	/*
	* Unlock bucket row.
	*/
	THC_UNLOCK(&hc_entry->rmx_head->hch_mtx);
	}

	/*
	* External function: update the TCP metrics of an entry in the hostcache.
	* Creates a new entry if none was found.
	*/
	void
	tcp_hc_update(struct in_conninfo inc, struct hc_metrics_lite hcml)
	{
	struct hc_metrics *hc_entry;

	hc_entry = tcp_hc_lookup(inc);
	if (hc_entry == NULL) {
	hc_entry = tcp_hc_insert(inc);
	if (hc_entry == NULL)
	return;
	}
	hc_entry->rmx_updates++;
	hc_entry->rmx_expire = V_tcp_hostcache.expire; /* start over again */

	if (hcml->rmx_rtt != 0) {
	if (hc_entry->rmx_rtt == 0)
	hc_entry->rmx_rtt = hcml->rmx_rtt;
	else
	hc_entry->rmx_rtt =
	(hc_entry->rmx_rtt + hcml->rmx_rtt) / 2;
	TCPSTAT_INC(tcps_cachedrtt);
	}
	if (hcml->rmx_rttvar != 0) {
	if (hc_entry->rmx_rttvar == 0)
	hc_entry->rmx_rttvar = hcml->rmx_rttvar;
	else
	hc_entry->rmx_rttvar =
	(hc_entry->rmx_rttvar + hcml->rmx_rttvar) / 2;
	TCPSTAT_INC(tcps_cachedrttvar);
	}
	if (hcml->rmx_ssthresh != 0) {
	if (hc_entry->rmx_ssthresh == 0)
	hc_entry->rmx_ssthresh = hcml->rmx_ssthresh;
	else
	hc_entry->rmx_ssthresh =
	(hc_entry->rmx_ssthresh + hcml->rmx_ssthresh) / 2;
	TCPSTAT_INC(tcps_cachedssthresh);
	}
	if (hcml->rmx_bandwidth != 0) {
	if (hc_entry->rmx_bandwidth == 0)
	hc_entry->rmx_bandwidth = hcml->rmx_bandwidth;
	else
	hc_entry->rmx_bandwidth =
	(hc_entry->rmx_bandwidth + hcml->rmx_bandwidth) / 2;
	/* TCPSTAT_INC(tcps_cachedbandwidth); */
	}
	if (hcml->rmx_cwnd != 0) {
	if (hc_entry->rmx_cwnd == 0)
	hc_entry->rmx_cwnd = hcml->rmx_cwnd;
	else
	hc_entry->rmx_cwnd =
	(hc_entry->rmx_cwnd + hcml->rmx_cwnd) / 2;
	/* TCPSTAT_INC(tcps_cachedcwnd); */
	}
	if (hcml->rmx_sendpipe != 0) {
	if (hc_entry->rmx_sendpipe == 0)
	hc_entry->rmx_sendpipe = hcml->rmx_sendpipe;
	else
	hc_entry->rmx_sendpipe =
	(hc_entry->rmx_sendpipe + hcml->rmx_sendpipe) /2;
	/* TCPSTAT_INC(tcps_cachedsendpipe); */
	}
	if (hcml->rmx_recvpipe != 0) {
	if (hc_entry->rmx_recvpipe == 0)
	hc_entry->rmx_recvpipe = hcml->rmx_recvpipe;
	else
	hc_entry->rmx_recvpipe =
	(hc_entry->rmx_recvpipe + hcml->rmx_recvpipe) /2;
	/* TCPSTAT_INC(tcps_cachedrecvpipe); */
	}

	TAILQ_REMOVE(&hc_entry->rmx_head->hch_bucket, hc_entry, rmx_q);
	TAILQ_INSERT_HEAD(&hc_entry->rmx_head->hch_bucket, hc_entry, rmx_q);
	THC_UNLOCK(&hc_entry->rmx_head->hch_mtx);
	}

	/*
	* Sysctl function: prints the list and values of all hostcache entries in
	* unsorted order.
	*/
	/*
	static int
	sysctl_tcp_hc_list(SYSCTL_HANDLER_ARGS)
	{
	int bufsize;
	int linesize = 128;
	char p, buf;
	int len, i, error;
	struct hc_metrics *hc_entry;
	#ifdef INET6
	char ip6buf[INET6_ADDRSTRLEN];
	#endif

	bufsize = linesize * (V_tcp_hostcache.cache_count + 1);

	p = buf = (char *)bsd_malloc(bufsize, M_TEMP, M_WAITOK\|M_ZERO);

	len = snprintf(p, linesize,
	"\nIP address MTU SSTRESH RTT RTTVAR BANDWIDTH "
	" CWND SENDPIPE RECVPIPE HITS UPD EXP\n");
	p += len;

	#define msec(u) (((u) + 500) / 1000)
	for (i = 0; i < V_tcp_hostcache.hashsize; i++) {
	THC_LOCK(&V_tcp_hostcache.hashbase[i].hch_mtx);
	TAILQ_FOREACH(hc_entry, &V_tcp_hostcache.hashbase[i].hch_bucket,
	rmx_q) {
	len = snprintf(p, linesize,
	"%-15s %5lu %8lu %6lums %6lums %9lu %8lu %8lu %8lu "
	"%4lu %4lu %4i\n",
	hc_entry->ip4.s_addr ? inet_ntoa(hc_entry->ip4) :
	#ifdef INET6
	ip6_sprintf(ip6buf, &hc_entry->ip6),
	#else
	"IPv6?",
	#endif
	hc_entry->rmx_mtu,
	hc_entry->rmx_ssthresh,
	msec(hc_entry->rmx_rtt *
	(RTM_RTTUNIT / (bsd_hz * TCP_RTT_SCALE))),
	msec(hc_entry->rmx_rttvar *
	(RTM_RTTUNIT / (bsd_hz * TCP_RTT_SCALE))),
	hc_entry->rmx_bandwidth * 8,
	hc_entry->rmx_cwnd,
	hc_entry->rmx_sendpipe,
	hc_entry->rmx_recvpipe,
	hc_entry->rmx_hits,
	hc_entry->rmx_updates,
	hc_entry->rmx_expire);
	p += len;
	}
	THC_UNLOCK(&V_tcp_hostcache.hashbase[i].hch_mtx);
	}
	#undef msec
	error = SYSCTL_OUT(req, buf, p - buf);
	free(buf, M_TEMP);
	return(error);
	}
	*/
	/*
	* Expire and purge (old\|all) entries in the tcp_hostcache. Runs
	* periodically from the callout.
	*/
	static void
	tcp_hc_purge(void *arg)
	{
	CURVNET_SET((struct vnet *) arg);
	struct hc_metrics hc_entry, hc_next;
	int all = 0;
	int i;

	if (V_tcp_hostcache.purgeall) {
	all = 1;
	V_tcp_hostcache.purgeall = 0;
	}

	for (i = 0; i < V_tcp_hostcache.hashsize; i++) {
	THC_LOCK(&V_tcp_hostcache.hashbase[i].hch_mtx);
	TAILQ_FOREACH_SAFE(hc_entry,
	&V_tcp_hostcache.hashbase[i].hch_bucket, rmx_q, hc_next) {
	if (all \|\| hc_entry->rmx_expire <= 0) {
	TAILQ_REMOVE(&V_tcp_hostcache.hashbase[i].hch_bucket,
	hc_entry, rmx_q);
	uma_zfree(V_tcp_hostcache.zone, hc_entry);
	V_tcp_hostcache.hashbase[i].hch_length--;
	V_tcp_hostcache.cache_count--;
	} else
	hc_entry->rmx_expire -= V_tcp_hostcache.prune;
	}
	THC_UNLOCK(&V_tcp_hostcache.hashbase[i].hch_mtx);
	}

	callout_reset(&V_tcp_hc_callout, V_tcp_hostcache.prune * bsd_hz,
	tcp_hc_purge, arg);
	CURVNET_RESTORE();
	}