path: root/sys/netinet/in_pcb.c

/*	$OpenBSD: in_pcb.c,v 1.17 1997/07/27 08:11:10 deraadt Exp $	*/
/*	$NetBSD: in_pcb.c,v 1.25 1996/02/13 23:41:53 christos Exp $	*/

/*
 * Copyright (c) 1982, 1986, 1991, 1993
 *	The Regents of the University of California.  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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)in_pcb.c	8.2 (Berkeley) 1/4/94
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/ioctl.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/proc.h>

#include <net/if.h>
#include <net/route.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/in_var.h>
#include <netinet/ip_var.h>
#include <dev/rndvar.h>

struct	in_addr zeroin_addr;

extern u_char ipsec_auth_default_level;
extern u_char ipsec_esp_trans_default_level;
extern u_char ipsec_esp_network_default_level;

/*
 * These configure the range of local port addresses assigned to
 * "unspecified" outgoing connections/packets/whatever.
 */
int ipport_firstauto = IPPORT_RESERVED;		/* 1024 */
int ipport_lastauto = IPPORT_USERRESERVED;	/* 5000 */
int ipport_hifirstauto = IPPORT_HIFIRSTAUTO;	/* 40000 */
int ipport_hilastauto = IPPORT_HILASTAUTO;	/* 44999 */

#define	INPCBHASH(table, faddr, fport, laddr, lport) \
	&(table)->inpt_hashtbl[(ntohl((faddr)->s_addr) + ntohs((fport)) + ntohs((lport))) & (table->inpt_hash)]

static int baddynamic __P((u_int16_t));

void
in_pcbinit(table, hashsize)
	struct inpcbtable *table;
	int hashsize;
{

	CIRCLEQ_INIT(&table->inpt_queue);
	table->inpt_hashtbl = hashinit(hashsize, M_PCB, &table->inpt_hash);
	table->inpt_lastport = 0;
}

/*
 * List of standard locked-down reserved ports.
 * XXX need to be able to modify this from userland. 
 */
static u_int16_t baddynamicports[] = {
	765, 749, 750, 751, 760, 761, 871,
	0	/* terminator */
};

/*
 * Check if the specified port is invalid for dynamic allocation.
 */
static int
baddynamic(port)
	u_int16_t port;
{
	int i;

	for (i = 0; baddynamicports[i] != 0; i++)
		if (baddynamicports[i] == port)
			return (1);
	return (0);
}

int
in_pcballoc(so, v)
	struct socket *so;
	void *v;
{
	struct inpcbtable *table = v;
	register struct inpcb *inp;
	int s;

	MALLOC(inp, struct inpcb *, sizeof(*inp), M_PCB, M_NOWAIT);
	if (inp == NULL)
		return (ENOBUFS);
	bzero((caddr_t)inp, sizeof(*inp));
	inp->inp_table = table;
	inp->inp_socket = so;
	inp->inp_seclevel[SL_AUTH] = ipsec_auth_default_level;
	inp->inp_seclevel[SL_ESP_TRANS] = ipsec_esp_trans_default_level;
	inp->inp_seclevel[SL_ESP_NETWORK] = ipsec_esp_network_default_level;
	s = splnet();
	CIRCLEQ_INSERT_HEAD(&table->inpt_queue, inp, inp_queue);
	LIST_INSERT_HEAD(INPCBHASH(table, &inp->inp_faddr, inp->inp_fport,
	    &inp->inp_laddr, inp->inp_lport), inp, inp_hash);
	splx(s);
	so->so_pcb = inp;
	return (0);
}

int
in_pcbbind(v, nam)
	register void *v;
	struct mbuf *nam;
{
	register struct inpcb *inp = v;
	register struct socket *so = inp->inp_socket;
	register struct inpcbtable *table = inp->inp_table;
	u_int16_t *lastport = &inp->inp_table->inpt_lastport;
	register struct sockaddr_in *sin;
	struct proc *p = curproc;		/* XXX */
	u_int16_t lport = 0;
	int wild = 0, reuseport = (so->so_options & SO_REUSEPORT);
	int error;

	if (in_ifaddr.tqh_first == 0)
		return (EADDRNOTAVAIL);
	if (inp->inp_lport || inp->inp_laddr.s_addr != INADDR_ANY)
		return (EINVAL);
	if ((so->so_options & (SO_REUSEADDR|SO_REUSEPORT)) == 0 &&
	    ((so->so_proto->pr_flags & PR_CONNREQUIRED) == 0 ||
	     (so->so_options & SO_ACCEPTCONN) == 0))
		wild = INPLOOKUP_WILDCARD;
	if (nam) {
		sin = mtod(nam, struct sockaddr_in *);
		if (nam->m_len != sizeof (*sin))
			return (EINVAL);
#ifdef notdef
		/*
		 * We should check the family, but old programs
		 * incorrectly fail to initialize it.
		 */
		if (sin->sin_family != AF_INET)
			return (EAFNOSUPPORT);
#endif
		lport = sin->sin_port;
		if (IN_MULTICAST(sin->sin_addr.s_addr)) {
			/*
			 * Treat SO_REUSEADDR as SO_REUSEPORT for multicast;
			 * allow complete duplication of binding if
			 * SO_REUSEPORT is set, or if SO_REUSEADDR is set
			 * and a multicast address is bound on both
			 * new and duplicated sockets.
			 */
			if (so->so_options & SO_REUSEADDR)
				reuseport = SO_REUSEADDR|SO_REUSEPORT;
		} else if (sin->sin_addr.s_addr != INADDR_ANY) {
			sin->sin_port = 0;		/* yech... */
			if (ifa_ifwithaddr(sintosa(sin)) == 0)
				return (EADDRNOTAVAIL);
		}
		if (lport) {
			struct inpcb *t;

			/* GROSS */
			if (ntohs(lport) < IPPORT_RESERVED &&
			    (error = suser(p->p_ucred, &p->p_acflag)))
				return (EACCES);
			if (so->so_uid) {
				t = in_pcblookup(table, zeroin_addr, 0,
				    sin->sin_addr, lport, INPLOOKUP_WILDCARD);
				if (t && (so->so_uid != t->inp_socket->so_uid))
					return (EADDRINUSE);
			}
			t = in_pcblookup(table, zeroin_addr, 0,
			    sin->sin_addr, lport, wild);
			if (t && (reuseport & t->inp_socket->so_options) == 0)
				return (EADDRINUSE);
		}
		inp->inp_laddr = sin->sin_addr;
	}
	if (lport == 0) {
		u_int16_t first, last, old = 0;
		int count;
		int loopcount = 0;

		if (inp->inp_flags & INP_HIGHPORT) {
			first = ipport_hifirstauto;	/* sysctl */
			last = ipport_hilastauto;
		} else if (inp->inp_flags & INP_LOWPORT) {
			if ((error = suser(p->p_ucred, &p->p_acflag)))
				return (EACCES);
			first = IPPORT_RESERVED-1; /* 1023 */
			last = 600;		   /* not IPPORT_RESERVED/2 */
		} else {
			first = ipport_firstauto;	/* sysctl */
			last  = ipport_lastauto;
		}

		/*
		 * Simple check to ensure all ports are not used up causing
		 * a deadlock here.
		 *
		 * We split the two cases (up and down) so that the direction
		 * is not being tested on each round of the loop.
		 */

portloop:
		if (first > last) {
			/*
			 * counting down
			 */
			if (loopcount == 0) {	/* only do this once. */
				old = first;
				first -= (arc4random() % (first - last));
			}
			count = first - last;
			*lastport = first;		/* restart each time */

			do {
				if (count-- <= 0) {	/* completely used? */
					if (loopcount == 0) {
						last = old;
						loopcount++;
						goto portloop;
					}
					return (EADDRNOTAVAIL);
				}
				--*lastport;
				if (*lastport > first || *lastport < last)
					*lastport = first;
				lport = htons(*lastport);
			} while (baddynamic(*lastport) ||
			    in_pcblookup(table, zeroin_addr, 0,
			    inp->inp_laddr, lport, wild));
		} else {
			/*
			 * counting up
			 */
			if (loopcount == 0) {	/* only do this once. */
				old = first;
				first += (arc4random() % (last - first));
			}
			count = last - first;
			*lastport = first;		/* restart each time */

			do {
				if (count-- <= 0) {	/* completely used? */
					if (loopcount == 0) {
						first = old;
						loopcount++;
						goto portloop;
					}
					return (EADDRNOTAVAIL);
				}
				++*lastport;
				if (*lastport < first || *lastport > last)
					*lastport = first;
				lport = htons(*lastport);
			} while (baddynamic(*lastport) ||
			    in_pcblookup(table, zeroin_addr, 0,
			    inp->inp_laddr, lport, wild));
		}
	}
	inp->inp_lport = lport;
	in_pcbrehash(inp);
	return (0);
}

/*
 * Connect from a socket to a specified address.
 * Both address and port must be specified in argument sin.
 * If don't have a local address for this socket yet,
 * then pick one.
 */
int
in_pcbconnect(v, nam)
	register void *v;
	struct mbuf *nam;
{
	register struct inpcb *inp = v;
	struct in_ifaddr *ia;
	struct sockaddr_in *ifaddr = NULL;
	register struct sockaddr_in *sin = mtod(nam, struct sockaddr_in *);

	if (nam->m_len != sizeof (*sin))
		return (EINVAL);
	if (sin->sin_family != AF_INET)
		return (EAFNOSUPPORT);
	if (sin->sin_port == 0)
		return (EADDRNOTAVAIL);
	if (in_ifaddr.tqh_first != 0) {
		/*
		 * If the destination address is INADDR_ANY,
		 * use the primary local address.
		 * If the supplied address is INADDR_BROADCAST,
		 * and the primary interface supports broadcast,
		 * choose the broadcast address for that interface.
		 */
		if (sin->sin_addr.s_addr == INADDR_ANY)
			sin->sin_addr = in_ifaddr.tqh_first->ia_addr.sin_addr;
		else if (sin->sin_addr.s_addr == INADDR_BROADCAST &&
		  (in_ifaddr.tqh_first->ia_ifp->if_flags & IFF_BROADCAST))
			sin->sin_addr = in_ifaddr.tqh_first->ia_broadaddr.sin_addr;
	}
	if (inp->inp_laddr.s_addr == INADDR_ANY) {
		register struct route *ro;

		ia = (struct in_ifaddr *)0;
		/* 
		 * If route is known or can be allocated now,
		 * our src addr is taken from the i/f, else punt.
		 */
		ro = &inp->inp_route;
		if (ro->ro_rt &&
		    (satosin(&ro->ro_dst)->sin_addr.s_addr !=
			sin->sin_addr.s_addr || 
		    inp->inp_socket->so_options & SO_DONTROUTE)) {
			RTFREE(ro->ro_rt);
			ro->ro_rt = (struct rtentry *)0;
		}
		if ((inp->inp_socket->so_options & SO_DONTROUTE) == 0 && /*XXX*/
		    (ro->ro_rt == (struct rtentry *)0 ||
		    ro->ro_rt->rt_ifp == (struct ifnet *)0)) {
			/* No route yet, so try to acquire one */
			ro->ro_dst.sa_family = AF_INET;
			ro->ro_dst.sa_len = sizeof(struct sockaddr_in);
			satosin(&ro->ro_dst)->sin_addr = sin->sin_addr;
			rtalloc(ro);
		}
		/*
		 * If we found a route, use the address
		 * corresponding to the outgoing interface
		 * unless it is the loopback (in case a route
		 * to our address on another net goes to loopback).
		 */
		if (ro->ro_rt && !(ro->ro_rt->rt_ifp->if_flags & IFF_LOOPBACK))
			ia = ifatoia(ro->ro_rt->rt_ifa);
		if (ia == 0) {
			u_int16_t fport = sin->sin_port;

			sin->sin_port = 0;
			ia = ifatoia(ifa_ifwithdstaddr(sintosa(sin)));
			if (ia == 0)
				ia = ifatoia(ifa_ifwithnet(sintosa(sin)));
			sin->sin_port = fport;
			if (ia == 0)
				ia = in_ifaddr.tqh_first;
			if (ia == 0)
				return (EADDRNOTAVAIL);
		}
		/*
		 * If the destination address is multicast and an outgoing
		 * interface has been set as a multicast option, use the
		 * address of that interface as our source address.
		 */
		if (IN_MULTICAST(sin->sin_addr.s_addr) &&
		    inp->inp_moptions != NULL) {
			struct ip_moptions *imo;
			struct ifnet *ifp;

			imo = inp->inp_moptions;
			if (imo->imo_multicast_ifp != NULL) {
				ifp = imo->imo_multicast_ifp;
				for (ia = in_ifaddr.tqh_first; ia != 0;
				    ia = ia->ia_list.tqe_next)
					if (ia->ia_ifp == ifp)
						break;
				if (ia == 0)
					return (EADDRNOTAVAIL);
			}
		}
		ifaddr = satosin(&ia->ia_addr);
	}
	if (in_pcbhashlookup(inp->inp_table, sin->sin_addr, sin->sin_port,
	    inp->inp_laddr.s_addr ? inp->inp_laddr : ifaddr->sin_addr,
	    inp->inp_lport) != 0)
		return (EADDRINUSE);
	if (inp->inp_laddr.s_addr == INADDR_ANY) {
		if (inp->inp_lport == 0)
			(void)in_pcbbind(inp, (struct mbuf *)0);
		inp->inp_laddr = ifaddr->sin_addr;
	}
	inp->inp_faddr = sin->sin_addr;
	inp->inp_fport = sin->sin_port;
	in_pcbrehash(inp);
	return (0);
}

void
in_pcbdisconnect(v)
	void *v;
{
	struct inpcb *inp = v;

	inp->inp_faddr.s_addr = INADDR_ANY;
	inp->inp_fport = 0;
	in_pcbrehash(inp);
	if (inp->inp_socket->so_state & SS_NOFDREF)
		in_pcbdetach(inp);
}

void
in_pcbdetach(v)
	void *v;
{
	struct inpcb *inp = v;
	struct socket *so = inp->inp_socket;
	int s;

	so->so_pcb = 0;
	sofree(so);
	if (inp->inp_options)
		(void)m_free(inp->inp_options);
	if (inp->inp_route.ro_rt)
		rtfree(inp->inp_route.ro_rt);
	ip_freemoptions(inp->inp_moptions);
#ifdef IPSEC
	/* XXX IPsec cleanup here */
#endif
	s = splnet();
	LIST_REMOVE(inp, inp_hash);
	CIRCLEQ_REMOVE(&inp->inp_table->inpt_queue, inp, inp_queue);
	splx(s);
	FREE(inp, M_PCB);
}

void
in_setsockaddr(inp, nam)
	register struct inpcb *inp;
	struct mbuf *nam;
{
	register struct sockaddr_in *sin;
	
	nam->m_len = sizeof (*sin);
	sin = mtod(nam, struct sockaddr_in *);
	bzero((caddr_t)sin, sizeof (*sin));
	sin->sin_family = AF_INET;
	sin->sin_len = sizeof(*sin);
	sin->sin_port = inp->inp_lport;
	sin->sin_addr = inp->inp_laddr;
}

void
in_setpeeraddr(inp, nam)
	struct inpcb *inp;
	struct mbuf *nam;
{
	register struct sockaddr_in *sin;
	
	nam->m_len = sizeof (*sin);
	sin = mtod(nam, struct sockaddr_in *);
	bzero((caddr_t)sin, sizeof (*sin));
	sin->sin_family = AF_INET;
	sin->sin_len = sizeof(*sin);
	sin->sin_port = inp->inp_fport;
	sin->sin_addr = inp->inp_faddr;
}

/*
 * Pass some notification to all connections of a protocol
 * associated with address dst.  The local address and/or port numbers
 * may be specified to limit the search.  The "usual action" will be
 * taken, depending on the ctlinput cmd.  The caller must filter any
 * cmds that are uninteresting (e.g., no error in the map).
 * Call the protocol specific routine (if any) to report
 * any errors for each matching socket.
 *
 * Must be called at splsoftnet.
 */
void
in_pcbnotify(table, dst, fport_arg, laddr, lport_arg, errno, notify)
	struct inpcbtable *table;
	struct sockaddr *dst;
	u_int fport_arg, lport_arg;
	struct in_addr laddr;
	int errno;
	void (*notify) __P((struct inpcb *, int));
{
	register struct inpcb *inp, *oinp;
	struct in_addr faddr;
	u_int16_t fport = fport_arg, lport = lport_arg;

	if (dst->sa_family != AF_INET)
		return;
	faddr = satosin(dst)->sin_addr;
	if (faddr.s_addr == INADDR_ANY)
		return;

	for (inp = table->inpt_queue.cqh_first;
	    inp != (struct inpcb *)&table->inpt_queue;) {
		if (inp->inp_faddr.s_addr != faddr.s_addr ||
		    inp->inp_socket == 0 ||
		    inp->inp_fport != fport ||
		    inp->inp_lport != lport ||
		    inp->inp_laddr.s_addr != laddr.s_addr) {
			inp = inp->inp_queue.cqe_next;
			continue;
		}
		oinp = inp;
		inp = inp->inp_queue.cqe_next;
		if (notify)
			(*notify)(oinp, errno);
	}
}

void
in_pcbnotifyall(table, dst, errno, notify)
	struct inpcbtable *table;
	struct sockaddr *dst;
	int errno;
	void (*notify) __P((struct inpcb *, int));
{
	register struct inpcb *inp, *oinp;
	struct in_addr faddr;

	if (dst->sa_family != AF_INET)
		return;
	faddr = satosin(dst)->sin_addr;
	if (faddr.s_addr == INADDR_ANY)
		return;

	for (inp = table->inpt_queue.cqh_first;
	    inp != (struct inpcb *)&table->inpt_queue;) {
		if (inp->inp_faddr.s_addr != faddr.s_addr ||
		    inp->inp_socket == 0) {
			inp = inp->inp_queue.cqe_next;
			continue;
		}
		oinp = inp;
		inp = inp->inp_queue.cqe_next;
		if (notify)
			(*notify)(oinp, errno);
	}
}

/*
 * Check for alternatives when higher level complains
 * about service problems.  For now, invalidate cached
 * routing information.  If the route was created dynamically
 * (by a redirect), time to try a default gateway again.
 */
void
in_losing(inp)
	struct inpcb *inp;
{
	register struct rtentry *rt;
	struct rt_addrinfo info;

	if ((rt = inp->inp_route.ro_rt)) {
		inp->inp_route.ro_rt = 0;
		bzero((caddr_t)&info, sizeof(info));
		info.rti_info[RTAX_DST] = &inp->inp_route.ro_dst;
		info.rti_info[RTAX_GATEWAY] = rt->rt_gateway;
		info.rti_info[RTAX_NETMASK] = rt_mask(rt);
		rt_missmsg(RTM_LOSING, &info, rt->rt_flags, 0);
		if (rt->rt_flags & RTF_DYNAMIC)
			(void) rtrequest(RTM_DELETE, rt_key(rt),
				rt->rt_gateway, rt_mask(rt), rt->rt_flags, 
				(struct rtentry **)0);
		else 
		/*
		 * A new route can be allocated
		 * the next time output is attempted.
		 */
			rtfree(rt);
	}
}

/*
 * After a routing change, flush old routing
 * and allocate a (hopefully) better one.
 */
void
in_rtchange(inp, errno)
	register struct inpcb *inp;
	int errno;
{
	if (inp->inp_route.ro_rt) {
		rtfree(inp->inp_route.ro_rt);
		inp->inp_route.ro_rt = 0;
		/*
		 * A new route can be allocated the next time
		 * output is attempted.
		 */
	}
}

struct inpcb *
in_pcblookup(table, faddr, fport_arg, laddr, lport_arg, flags)
	struct inpcbtable *table;
	struct in_addr faddr, laddr;
	u_int fport_arg, lport_arg;
	int flags;
{
	register struct inpcb *inp, *match = 0;
	int matchwild = 3, wildcard;
	u_int16_t fport = fport_arg, lport = lport_arg;

	for (inp = table->inpt_queue.cqh_first;
	    inp != (struct inpcb *)&table->inpt_queue;
	    inp = inp->inp_queue.cqe_next) {
		if (inp->inp_lport != lport)
			continue;
		wildcard = 0;
		if (inp->inp_faddr.s_addr != INADDR_ANY) {
			if (faddr.s_addr == INADDR_ANY)
				wildcard++;
			else if (inp->inp_faddr.s_addr != faddr.s_addr ||
			    inp->inp_fport != fport)
				continue;
		} else {
			if (faddr.s_addr != INADDR_ANY)
				wildcard++;
		}
		if (inp->inp_laddr.s_addr != INADDR_ANY) {
			if (laddr.s_addr == INADDR_ANY)
				wildcard++;
			else if (inp->inp_laddr.s_addr != laddr.s_addr)
				continue;
		} else {
			if (laddr.s_addr != INADDR_ANY)
				wildcard++;
		}
		if (wildcard && (flags & INPLOOKUP_WILDCARD) == 0)
			continue;
		if (wildcard < matchwild) {
			match = inp;
			matchwild = wildcard;
			if (matchwild == 0)
				break;
		}
	}
	return (match);
}

void
in_pcbrehash(inp)
	struct inpcb *inp;
{
	struct inpcbtable *table = inp->inp_table;
	int s;

	s = splnet();
	LIST_REMOVE(inp, inp_hash);
	LIST_INSERT_HEAD(INPCBHASH(table, &inp->inp_faddr, inp->inp_fport,
	    &inp->inp_laddr, inp->inp_lport), inp, inp_hash);
	splx(s);
}

#ifdef DIAGNOSTIC
int	in_pcbnotifymiss = 0;
#endif

struct inpcb *
in_pcbhashlookup(table, faddr, fport_arg, laddr, lport_arg)
	struct inpcbtable *table;
	struct in_addr faddr, laddr;
	u_int fport_arg, lport_arg;
{
	struct inpcbhead *head;
	register struct inpcb *inp;
	u_int16_t fport = fport_arg, lport = lport_arg;

	head = INPCBHASH(table, &faddr, fport, &laddr, lport);
	for (inp = head->lh_first; inp != NULL; inp = inp->inp_hash.le_next) {
		if (inp->inp_faddr.s_addr == faddr.s_addr &&
		    inp->inp_fport == fport &&
		    inp->inp_lport == lport &&
		    inp->inp_laddr.s_addr == laddr.s_addr) {
			/*
			 * Move this PCB to the head of hash chain so that
			 * repeated accesses are quicker.  This is analogous to
			 * the historic single-entry PCB cache.
			 */
			if (inp != head->lh_first) {
				LIST_REMOVE(inp, inp_hash);
				LIST_INSERT_HEAD(head, inp, inp_hash);
			}
			break;
		}
	}
#ifdef DIAGNOSTIC
	if (inp == NULL && in_pcbnotifymiss) {
		printf("in_pcbhashlookup: faddr=%08x fport=%d laddr=%08x lport=%d\n",
		    ntohl(faddr.s_addr), ntohs(fport),
		    ntohl(laddr.s_addr), ntohs(lport));
	}
#endif
	return (inp);
}