BSD 4.4 Lite usr.sbin Sources

4 files changed, 778 insertions, 0 deletions

diff --git a/usr.sbin/arp/Makefile b/usr.sbin/arp/Makefile
new file mode 100644
index 0000000..f69a430
--- /dev/null
+++ b/usr.sbin/arp/Makefile
@@ -0,0 +1,13 @@
+#	@(#)Makefile	8.2 (Berkeley) 4/18/94
+
+PROG=	arp
+MAN8=	arp.0
+CLEANFILES=arp4.0
+
+all: ${PROG} arp4.0 ${MAN8}
+
+beforeinstall:
+	install -c -o ${MANOWN} -g ${MANGRP} -m ${MANMODE} arp4.0 \
+	    ${DESTDIR}${MANDIR}4/arp.0
+
+.include <bsd.prog.mk>
diff --git a/usr.sbin/arp/arp.8 b/usr.sbin/arp/arp.8
new file mode 100644
index 0000000..27252dd
--- /dev/null
+++ b/usr.sbin/arp/arp.8
@@ -0,0 +1,127 @@
+.\" Copyright (c) 1985, 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.
+.\"
+.\"     @(#)arp.8	8.1 (Berkeley) 6/6/93
+.\"
+.Dd June 6, 1993
+.Dt ARP 8
+.Os BSD 4.3
+.Sh NAME
+.Nm arp
+.Nd address resolution display and control
+.Sh SYNOPSIS
+.Nm arp
+.Ar hostname
+.Nm arp
+.Fl a
+.Nm arp
+.Fl d Ar hostname
+.Nm arp
+.Fl s Ar hostname ether_addr
+.Op Ar temp
+.Op Ar pub
+.Op Ar trail
+.Nm arp
+.Fl f Ar filename
+.Sh DESCRIPTION
+The
+.Nm arp
+program displays and modifies the Internet-to-Ethernet address translation
+tables used by the address resolution protocol
+.Pq Xr arp 4 .
+With no flags, the program displays the current
+.Tn ARP
+entry for
+.Ar hostname .
+The host may be specified by name or by number,
+using Internet dot notation.
+.Pp
+Available options:
+.Bl -tag -width Ds
+.It Fl a
+The program displays all of the current
+.Tn ARP
+entries.
+.It Fl d
+A super-user may delete an entry for the host called
+.Ar hostname
+with the
+.Fl d
+flag.
+.It Fl s Ar hostname ether_addr
+Create an
+.Tn ARP
+entry for the host called
+.Ar hostname
+with the Ethernet address 
+.Ar ether_addr .
+The Ethernet address is given as six hex bytes separated by colons.
+The entry will be permanent unless the word
+.Ar temp
+is given in the command. 
+If the word
+.Ar pub
+is given, the entry will be "published"; i.e., this system will
+act as an
+.Tn ARP
+server,
+responding to requests for 
+.Ar hostname
+even though the host address is not its own.
+The word
+.Ar trail
+indicates that trailer encapsulations may be sent to this host.
+.It Fl f
+Causes the file
+.Ar filename
+to be read and multiple entries to be set in the
+.Tn ARP
+tables.  Entries
+in the file should be of the form
+.Pp
+.Bd -filled -offset indent -compact
+.Ar hostname ether_addr
+.Op Ar temp
+.Op Ar pub
+.Op Ar trail
+.Ed
+.Pp
+with argument meanings as given above.
+.El
+.Sh SEE ALSO
+.Xr inet 3 ,
+.Xr arp 4 ,
+.Xr ifconfig 8
+.Sh HISTORY
+The
+.Nm
+command appeared in
+.Bx 4.3 .
diff --git a/usr.sbin/arp/arp.c b/usr.sbin/arp/arp.c
new file mode 100644
index 0000000..2182dc8
--- /dev/null
+++ b/usr.sbin/arp/arp.c
@@ -0,0 +1,514 @@
+/*
+ * Copyright (c) 1984, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Sun Microsystems, Inc.
+ *
+ * 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.
+ */
+
+#ifndef lint
+static char copyright[] =
+"@(#) Copyright (c) 1984, 1993\n\
+	The Regents of the University of California.  All rights reserved.\n";
+#endif /* not lint */
+
+#ifndef lint
+static char sccsid[] = "@(#)arp.c	8.2 (Berkeley) 1/2/94";
+#endif /* not lint */
+
+/*
+ * arp - display, set, and delete arp table entries
+ */
+
+
+#include <sys/param.h>
+#include <sys/file.h>
+#include <sys/socket.h>
+#include <sys/sysctl.h>
+
+#include <net/if.h>
+#include <net/if_dl.h>
+#include <net/if_types.h>
+#include <net/route.h>
+
+#include <netinet/in.h>
+#include <netinet/if_ether.h>
+
+#include <arpa/inet.h>
+
+#include <netdb.h>
+#include <errno.h>
+#include <nlist.h>
+#include <stdio.h>
+#include <paths.h>
+
+extern int errno;
+static int pid;
+static int kflag;
+static int nflag;
+static int s = -1;
+
+main(argc, argv)
+	int argc;
+	char **argv;
+{
+	int ch;
+
+	pid = getpid();
+	while ((ch = getopt(argc, argv, "ands")) != EOF)
+		switch((char)ch) {
+		case 'a':
+			dump(0);
+			exit(0);
+		case 'd':
+			if (argc < 3 || argc > 4)
+				usage();
+			delete(argv[2], argv[3]);
+			exit(0);
+		case 'n':
+			nflag = 1;
+			continue;
+		case 's':
+			if (argc < 4 || argc > 7)
+				usage();
+			exit(set(argc-2, &argv[2]) ? 1 : 0);
+		case '?':
+		default:
+			usage();
+		}
+	if (argc != 2)
+		usage();
+	get(argv[1]);
+	exit(0);
+}
+
+/*
+ * Process a file to set standard arp entries
+ */
+file(name)
+	char *name;
+{
+	FILE *fp;
+	int i, retval;
+	char line[100], arg[5][50], *args[5];
+
+	if ((fp = fopen(name, "r")) == NULL) {
+		fprintf(stderr, "arp: cannot open %s\n", name);
+		exit(1);
+	}
+	args[0] = &arg[0][0];
+	args[1] = &arg[1][0];
+	args[2] = &arg[2][0];
+	args[3] = &arg[3][0];
+	args[4] = &arg[4][0];
+	retval = 0;
+	while(fgets(line, 100, fp) != NULL) {
+		i = sscanf(line, "%s %s %s %s %s", arg[0], arg[1], arg[2],
+		    arg[3], arg[4]);
+		if (i < 2) {
+			fprintf(stderr, "arp: bad line: %s\n", line);
+			retval = 1;
+			continue;
+		}
+		if (set(i, args))
+			retval = 1;
+	}
+	fclose(fp);
+	return (retval);
+}
+
+getsocket() {
+	if (s < 0) {
+		s = socket(PF_ROUTE, SOCK_RAW, 0);
+		if (s < 0) {
+			perror("arp: socket");
+			exit(1);
+		}
+	}
+}
+
+struct	sockaddr_in so_mask = {8, 0, 0, { 0xffffffff}};
+struct	sockaddr_inarp blank_sin = {sizeof(blank_sin), AF_INET }, sin_m;
+struct	sockaddr_dl blank_sdl = {sizeof(blank_sdl), AF_LINK }, sdl_m;
+int	expire_time, flags, export_only, doing_proxy, found_entry;
+struct	{
+	struct	rt_msghdr m_rtm;
+	char	m_space[512];
+}	m_rtmsg;
+
+/*
+ * Set an individual arp entry 
+ */
+set(argc, argv)
+	int argc;
+	char **argv;
+{
+	struct hostent *hp;
+	register struct sockaddr_inarp *sin = &sin_m;
+	register struct sockaddr_dl *sdl;
+	register struct rt_msghdr *rtm = &(m_rtmsg.m_rtm);
+	u_char *ea;
+	char *host = argv[0], *eaddr = argv[1];
+
+	getsocket();
+	argc -= 2;
+	argv += 2;
+	sdl_m = blank_sdl;
+	sin_m = blank_sin;
+	sin->sin_addr.s_addr = inet_addr(host);
+	if (sin->sin_addr.s_addr == -1) {
+		if (!(hp = gethostbyname(host))) {
+			fprintf(stderr, "arp: %s: ", host);
+			herror((char *)NULL);
+			return (1);
+		}
+		bcopy((char *)hp->h_addr, (char *)&sin->sin_addr,
+		    sizeof sin->sin_addr);
+	}
+	ea = (u_char *)LLADDR(&sdl_m);
+	if (ether_aton(eaddr, ea) == 0)
+		sdl_m.sdl_alen = 6;
+	doing_proxy = flags = export_only = expire_time = 0;
+	while (argc-- > 0) {
+		if (strncmp(argv[0], "temp", 4) == 0) {
+			struct timeval time;
+			gettimeofday(&time, 0);
+			expire_time = time.tv_sec + 20 * 60;
+		}
+		else if (strncmp(argv[0], "pub", 3) == 0) {
+			flags |= RTF_ANNOUNCE;
+			doing_proxy = SIN_PROXY;
+		} else if (strncmp(argv[0], "trail", 5) == 0) {
+			printf("%s: Sending trailers is no longer supported\n",
+				host);
+		}
+		argv++;
+	}
+tryagain:
+	if (rtmsg(RTM_GET) < 0) {
+		perror(host);
+		return (1);
+	}
+	sin = (struct sockaddr_inarp *)(rtm + 1);
+	sdl = (struct sockaddr_dl *)(sin->sin_len + (char *)sin);
+	if (sin->sin_addr.s_addr == sin_m.sin_addr.s_addr) {
+		if (sdl->sdl_family == AF_LINK &&
+		    (rtm->rtm_flags & RTF_LLINFO) &&
+		    !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) {
+		case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023:
+		case IFT_ISO88024: case IFT_ISO88025:
+			goto overwrite;
+		}
+		if (doing_proxy == 0) {
+			printf("set: can only proxy for %s\n", host);
+			return (1);
+		}
+		if (sin_m.sin_other & SIN_PROXY) {
+			printf("set: proxy entry exists for non 802 device\n");
+			return(1);
+		}
+		sin_m.sin_other = SIN_PROXY;
+		export_only = 1;
+		goto tryagain;
+	}
+overwrite:
+	if (sdl->sdl_family != AF_LINK) {
+		printf("cannot intuit interface index and type for %s\n", host);
+		return (1);
+	}
+	sdl_m.sdl_type = sdl->sdl_type;
+	sdl_m.sdl_index = sdl->sdl_index;
+	return (rtmsg(RTM_ADD));
+}
+
+/*
+ * Display an individual arp entry
+ */
+get(host)
+	char *host;
+{
+	struct hostent *hp;
+	struct sockaddr_inarp *sin = &sin_m;
+	u_char *ea;
+
+	sin_m = blank_sin;
+	sin->sin_addr.s_addr = inet_addr(host);
+	if (sin->sin_addr.s_addr == -1) {
+		if (!(hp = gethostbyname(host))) {
+			fprintf(stderr, "arp: %s: ", host);
+			herror((char *)NULL);
+			exit(1);
+		}
+		bcopy((char *)hp->h_addr, (char *)&sin->sin_addr,
+		    sizeof sin->sin_addr);
+	}
+	dump(sin->sin_addr.s_addr);
+	if (found_entry == 0) {
+		printf("%s (%s) -- no entry\n",
+		    host, inet_ntoa(sin->sin_addr));
+		exit(1);
+	}
+}
+
+/*
+ * Delete an arp entry 
+ */
+delete(host, info)
+	char *host;
+	char *info;
+{
+	struct hostent *hp;
+	register struct sockaddr_inarp *sin = &sin_m;
+	register struct rt_msghdr *rtm = &m_rtmsg.m_rtm;
+	struct sockaddr_dl *sdl;
+	u_char *ea;
+	char *eaddr;
+
+	if (info && strncmp(info, "pro", 3) )
+		export_only = 1;
+	getsocket();
+	sin_m = blank_sin;
+	sin->sin_addr.s_addr = inet_addr(host);
+	if (sin->sin_addr.s_addr == -1) {
+		if (!(hp = gethostbyname(host))) {
+			fprintf(stderr, "arp: %s: ", host);
+			herror((char *)NULL);
+			return (1);
+		}
+		bcopy((char *)hp->h_addr, (char *)&sin->sin_addr,
+		    sizeof sin->sin_addr);
+	}
+tryagain:
+	if (rtmsg(RTM_GET) < 0) {
+		perror(host);
+		return (1);
+	}
+	sin = (struct sockaddr_inarp *)(rtm + 1);
+	sdl = (struct sockaddr_dl *)(sin->sin_len + (char *)sin);
+	if (sin->sin_addr.s_addr == sin_m.sin_addr.s_addr) {
+		if (sdl->sdl_family == AF_LINK &&
+		    (rtm->rtm_flags & RTF_LLINFO) &&
+		    !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) {
+		case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023:
+		case IFT_ISO88024: case IFT_ISO88025:
+			goto delete;
+		}
+	}
+	if (sin_m.sin_other & SIN_PROXY) {
+		fprintf(stderr, "delete: can't locate %s\n",host);
+		return (1);
+	} else {
+		sin_m.sin_other = SIN_PROXY;
+		goto tryagain;
+	}
+delete:
+	if (sdl->sdl_family != AF_LINK) {
+		printf("cannot locate %s\n", host);
+		return (1);
+	}
+	if (rtmsg(RTM_DELETE) == 0)
+		printf("%s (%s) deleted\n", host, inet_ntoa(sin->sin_addr));
+}
+
+/*
+ * Dump the entire arp table
+ */
+dump(addr)
+u_long addr;
+{
+	int mib[6];
+	size_t needed;
+	char *host, *malloc(), *lim, *buf, *next;
+	struct rt_msghdr *rtm;
+	struct sockaddr_inarp *sin;
+	struct sockaddr_dl *sdl;
+	extern int h_errno;
+	struct hostent *hp;
+
+	mib[0] = CTL_NET;
+	mib[1] = PF_ROUTE;
+	mib[2] = 0;
+	mib[3] = AF_INET;
+	mib[4] = NET_RT_FLAGS;
+	mib[5] = RTF_LLINFO;
+	if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
+		quit("route-sysctl-estimate");
+	if ((buf = malloc(needed)) == NULL)
+		quit("malloc");
+	if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0)
+		quit("actual retrieval of routing table");
+	lim = buf + needed;
+	for (next = buf; next < lim; next += rtm->rtm_msglen) {
+		rtm = (struct rt_msghdr *)next;
+		sin = (struct sockaddr_inarp *)(rtm + 1);
+		sdl = (struct sockaddr_dl *)(sin + 1);
+		if (addr) {
+			if (addr != sin->sin_addr.s_addr)
+				continue;
+			found_entry = 1;
+		}
+		if (nflag == 0)
+			hp = gethostbyaddr((caddr_t)&(sin->sin_addr),
+			    sizeof sin->sin_addr, AF_INET);
+		else
+			hp = 0;
+		if (hp)
+			host = hp->h_name;
+		else {
+			host = "?";
+			if (h_errno == TRY_AGAIN)
+				nflag = 1;
+		}
+		printf("%s (%s) at ", host, inet_ntoa(sin->sin_addr));
+		if (sdl->sdl_alen)
+			ether_print(LLADDR(sdl));
+		else
+			printf("(incomplete)");
+		if (rtm->rtm_rmx.rmx_expire == 0)
+			printf(" permanent");
+		if (sin->sin_other & SIN_PROXY)
+			printf(" published (proxy only)");
+		if (rtm->rtm_addrs & RTA_NETMASK) {
+			sin = (struct sockaddr_inarp *)
+				(sdl->sdl_len + (char *)sdl);
+			if (sin->sin_addr.s_addr == 0xffffffff)
+				printf(" published");
+			if (sin->sin_len != 8)
+				printf("(wierd)");
+		}
+		printf("\n");
+	}
+}
+
+ether_print(cp)
+	u_char *cp;
+{
+	printf("%x:%x:%x:%x:%x:%x", cp[0], cp[1], cp[2], cp[3], cp[4], cp[5]);
+}
+
+ether_aton(a, n)
+	char *a;
+	u_char *n;
+{
+	int i, o[6];
+
+	i = sscanf(a, "%x:%x:%x:%x:%x:%x", &o[0], &o[1], &o[2],
+					   &o[3], &o[4], &o[5]);
+	if (i != 6) {
+		fprintf(stderr, "arp: invalid Ethernet address '%s'\n", a);
+		return (1);
+	}
+	for (i=0; i<6; i++)
+		n[i] = o[i];
+	return (0);
+}
+
+usage()
+{
+	printf("usage: arp hostname\n");
+	printf("       arp -a [kernel] [kernel_memory]\n");
+	printf("       arp -d hostname\n");
+	printf("       arp -s hostname ether_addr [temp] [pub]\n");
+	printf("       arp -f filename\n");
+	exit(1);
+}
+
+rtmsg(cmd)
+{
+	static int seq;
+	int rlen;
+	register struct rt_msghdr *rtm = &m_rtmsg.m_rtm;
+	register char *cp = m_rtmsg.m_space;
+	register int l;
+
+	errno = 0;
+	if (cmd == RTM_DELETE)
+		goto doit;
+	bzero((char *)&m_rtmsg, sizeof(m_rtmsg));
+	rtm->rtm_flags = flags;
+	rtm->rtm_version = RTM_VERSION;
+
+	switch (cmd) {
+	default:
+		fprintf(stderr, "arp: internal wrong cmd\n");
+		exit(1);
+	case RTM_ADD:
+		rtm->rtm_addrs |= RTA_GATEWAY;
+		rtm->rtm_rmx.rmx_expire = expire_time;
+		rtm->rtm_inits = RTV_EXPIRE;
+		rtm->rtm_flags |= (RTF_HOST | RTF_STATIC);
+		sin_m.sin_other = 0;
+		if (doing_proxy) {
+			if (export_only)
+				sin_m.sin_other = SIN_PROXY;
+			else {
+				rtm->rtm_addrs |= RTA_NETMASK;
+				rtm->rtm_flags &= ~RTF_HOST;
+			}
+		}
+		/* FALLTHROUGH */
+	case RTM_GET:
+		rtm->rtm_addrs |= RTA_DST;
+	}
+#define NEXTADDR(w, s) \
+	if (rtm->rtm_addrs & (w)) { \
+		bcopy((char *)&s, cp, sizeof(s)); cp += sizeof(s);}
+
+	NEXTADDR(RTA_DST, sin_m);
+	NEXTADDR(RTA_GATEWAY, sdl_m);
+	NEXTADDR(RTA_NETMASK, so_mask);
+
+	rtm->rtm_msglen = cp - (char *)&m_rtmsg;
+doit:
+	l = rtm->rtm_msglen;
+	rtm->rtm_seq = ++seq;
+	rtm->rtm_type = cmd;
+	if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) {
+		if (errno != ESRCH || cmd != RTM_DELETE) {
+			perror("writing to routing socket");
+			return (-1);
+		}
+	}
+	do {
+		l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg));
+	} while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid));
+	if (l < 0)
+		(void) fprintf(stderr, "arp: read from routing socket: %s\n",
+		    strerror(errno));
+	return (0);
+}
+
+quit(msg)
+char *msg;
+{
+	fprintf(stderr, "%s\n", msg);
+	exit(1);
+}
diff --git a/usr.sbin/arp/arp4.4 b/usr.sbin/arp/arp4.4
new file mode 100644
index 0000000..0cd7161
--- /dev/null
+++ b/usr.sbin/arp/arp4.4
@@ -0,0 +1,124 @@
+.\" Copyright (c) 1985, 1986, 1988, 1994
+.\"	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
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+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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+.\"
+.\"	@(#)arp4.4	6.5 (Berkeley) 4/18/94
+.\"
+.Dd April 18, 1994
+.Dt ARP 4
+.Os BSD 4
+.Sh NAME
+.Nm arp
+.Nd Address Resolution Protocol
+.Sh SYNOPSIS
+.Em "pseudo-device ether"
+.Sh DESCRIPTION
+The Address Resolution Protocol (ARP) is a protocol used to dynamically
+map between Internet host addresses and 10Mb/s Ethernet addresses.
+It is used by all the 10Mb/s Ethernet interface drivers.
+It is not specific to Internet protocols or to 10Mb/s Ethernet,
+but this implementation currently supports only that combination.
+.Pp
+ARP caches Internet-Ethernet address mappings. 
+When an interface requests a mapping for an address not in the cache,
+ARP queues the message which requires the mapping and broadcasts
+a message on the associated network requesting the address mapping.
+If a response is provided, the new mapping is cached and any pending
+message is transmitted.
+ARP will queue at most one packet while waiting for a response to a
+mapping request;
+only the most recently ``transmitted'' packet is kept.
+If the target host does not respond after several requests,
+the host is considered to be down for a short period (normally 20 seconds),
+allowing an error to be returned to transmission attempts during this
+interval.
+The error is
+.Li EHOSTDOWN
+for a non-responding destination host, and
+.Li EHOSTUNREACH
+for a non-responding router.
+.Pp
+The ARP cache is stored in the system routing table as
+dynamically-created host routes.
+The route to a directly-attached Ethernet network is installed as a
+.Dq cloning
+route (one with the
+.Li RTF_CLONING
+flag set),
+causing routes to individual hosts on that network to be created on
+demand.
+These routes time out periodically (normally 20 minutes after validated;
+entries are not validated when not in use).
+An entry for a host which is not responding is a
+.Dq reject
+route (one with the
+.Li RTF_REJECT
+flag set).
+.Pp
+ARP entries may be added, deleted or changed with the
+.Xr arp 8
+utility.
+Manually-added entries may be temporary or permanent,
+and may be
+.Dq published ,
+in which case the system will respond to ARP requests for that host
+as if it were the target of the request.
+.Pp
+In the past,
+ARP was used to negotiate the use of a trailer encapsulation.
+This is no longer supported.
+.Pp
+ARP watches passively for hosts impersonating the local host (i.e. a host
+which responds to an ARP mapping request for the local host's address).
+.Sh DIAGNOSTICS
+.Em "duplicate IP address %x!! sent from ethernet address: %x:%x:%x:%x:%x:%x."
+ARP has discovered another host on the local network which responds to
+mapping requests for its own Internet address with a different Ethernet
+address, generally indicating that two hosts are attempting to use the
+same Internet address.
+.Sh SEE ALSO
+.Xr inet 4 ,
+.Xr route 4 ,
+.Xr arp 8 ,
+.Xr ifconfig 8 ,
+.Xr route 8
+.sp
+.Rs
+.%A Plummer, D.
+.%B "An Ethernet Address Resolution Protocol"
+.%T RFC826
+.Re
+.Rs
+.%A Leffler, S.J.
+.%A Karels, M.J.
+.%B "Trailer Encapsulations
+.%T RFC893
+.Re
+