ARP(8): Import from FreeBSD

1 files changed, 884 insertions, 0 deletions

diff --git a/freebsd/usr.sbin/arp/arp.c b/freebsd/usr.sbin/arp/arp.c
new file mode 100644
index 00000000..951d6f5c
--- /dev/null
+++ b/freebsd/usr.sbin/arp/arp.c
@@ -0,0 +1,884 @@
+#include <machine/rtems-bsd-user-space.h>
+
+/*
+ * 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.
+ * 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.
+ */
+
+#if 0
+#ifndef lint
+static char const copyright[] =
+"@(#) Copyright (c) 1984, 1993\n\
+	The Regents of the University of California.  All rights reserved.\n";
+#endif /* not lint */
+
+#ifndef lint
+static char const sccsid[] = "@(#)from: arp.c	8.2 (Berkeley) 1/2/94";
+#endif /* not lint */
+#endif
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+/*
+ * arp - display, set, and delete arp table entries
+ */
+
+
+#include <rtems/bsd/sys/param.h>
+#include <sys/file.h>
+#include <sys/socket.h>
+#include <sys/sockio.h>
+#include <sys/sysctl.h>
+#include <sys/ioctl.h>
+#include <sys/time.h>
+
+#include <net/if.h>
+#include <net/if_dl.h>
+#include <net/if_types.h>
+#include <net/route.h>
+#include <net/iso88025.h>
+
+#include <netinet/in.h>
+#include <netinet/if_ether.h>
+
+#include <arpa/inet.h>
+
+#include <ctype.h>
+#include <err.h>
+#include <errno.h>
+#include <netdb.h>
+#include <nlist.h>
+#include <paths.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <unistd.h>
+
+typedef void (action_fn)(struct sockaddr_dl *sdl,
+	struct sockaddr_in *s_in, struct rt_msghdr *rtm);
+
+static int search(u_long addr, action_fn *action);
+static action_fn print_entry;
+static action_fn nuke_entry;
+
+static int delete(char *host);
+static void usage(void);
+static int set(int argc, char **argv);
+static int get(char *host);
+static int file(char *name);
+static struct rt_msghdr *rtmsg(int cmd,
+    struct sockaddr_in *dst, struct sockaddr_dl *sdl);
+static int get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr);
+static struct sockaddr_in *getaddr(char *host);
+static int valid_type(int type);
+
+static int nflag;	/* no reverse dns lookups */
+static char *rifname;
+
+static time_t	expire_time;
+static int	flags, doing_proxy;
+
+struct if_nameindex *ifnameindex;
+
+/* which function we're supposed to do */
+#define F_GET		1
+#define F_SET		2
+#define F_FILESET	3
+#define F_REPLACE	4
+#define F_DELETE	5
+
+#define SETFUNC(f)	{ if (func) usage(); func = (f); }
+
+int
+main(int argc, char *argv[])
+{
+	int ch, func = 0;
+	int rtn = 0;
+	int aflag = 0;	/* do it for all entries */
+
+	while ((ch = getopt(argc, argv, "andfsSi:")) != -1)
+		switch(ch) {
+		case 'a':
+			aflag = 1;
+			break;
+		case 'd':
+			SETFUNC(F_DELETE);
+			break;
+		case 'n':
+			nflag = 1;
+			break;
+		case 'S':
+			SETFUNC(F_REPLACE);
+			break;
+		case 's':
+			SETFUNC(F_SET);
+			break;
+		case 'f' :
+			SETFUNC(F_FILESET);
+			break;
+		case 'i':
+			rifname = optarg;
+			break;
+		case '?':
+		default:
+			usage();
+		}
+	argc -= optind;
+	argv += optind;
+
+	if (!func)
+		func = F_GET;
+	if (rifname) {
+		if (func != F_GET && !(func == F_DELETE && aflag))
+			errx(1, "-i not applicable to this operation");
+		if (if_nametoindex(rifname) == 0) {
+			if (errno == ENXIO)
+				errx(1, "interface %s does not exist", rifname);
+			else
+				err(1, "if_nametoindex(%s)", rifname);
+		}
+	}
+	switch (func) {
+	case F_GET:
+		if (aflag) {
+			if (argc != 0)
+				usage();
+			search(0, print_entry);
+		} else {
+			if (argc != 1)
+				usage();
+			rtn = get(argv[0]);
+		}
+		break;
+	case F_SET:
+	case F_REPLACE:
+		if (argc < 2 || argc > 6)
+			usage();
+		if (func == F_REPLACE)
+			(void)delete(argv[0]);
+		rtn = set(argc, argv) ? 1 : 0;
+		break;
+	case F_DELETE:
+		if (aflag) {
+			if (argc != 0)
+				usage();
+			search(0, nuke_entry);
+		} else {
+			if (argc != 1)
+				usage();
+			rtn = delete(argv[0]);
+		}
+		break;
+	case F_FILESET:
+		if (argc != 1)
+			usage();
+		rtn = file(argv[0]);
+		break;
+	}
+
+	if (ifnameindex != NULL)
+		if_freenameindex(ifnameindex);
+
+	return (rtn);
+}
+
+/*
+ * Process a file to set standard arp entries
+ */
+static int
+file(char *name)
+{
+	FILE *fp;
+	int i, retval;
+	char line[100], arg[5][50], *args[5], *p;
+
+	if ((fp = fopen(name, "r")) == NULL)
+		err(1, "cannot open %s", name);
+	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, sizeof(line), fp) != NULL) {
+		if ((p = strchr(line, '#')) != NULL)
+			*p = '\0';
+		for (p = line; isblank(*p); p++);
+		if (*p == '\n' || *p == '\0')
+			continue;
+		i = sscanf(p, "%49s %49s %49s %49s %49s", arg[0], arg[1],
+		    arg[2], arg[3], arg[4]);
+		if (i < 2) {
+			warnx("bad line: %s", line);
+			retval = 1;
+			continue;
+		}
+		if (set(i, args))
+			retval = 1;
+	}
+	fclose(fp);
+	return (retval);
+}
+
+/*
+ * Given a hostname, fills up a (static) struct sockaddr_in with
+ * the address of the host and returns a pointer to the
+ * structure.
+ */
+static struct sockaddr_in *
+getaddr(char *host)
+{
+	struct hostent *hp;
+	static struct sockaddr_in reply;
+
+	bzero(&reply, sizeof(reply));
+	reply.sin_len = sizeof(reply);
+	reply.sin_family = AF_INET;
+	reply.sin_addr.s_addr = inet_addr(host);
+	if (reply.sin_addr.s_addr == INADDR_NONE) {
+		if (!(hp = gethostbyname(host))) {
+			warnx("%s: %s", host, hstrerror(h_errno));
+			return (NULL);
+		}
+		bcopy((char *)hp->h_addr, (char *)&reply.sin_addr,
+			sizeof reply.sin_addr);
+	}
+	return (&reply);
+}
+
+/*
+ * Returns true if the type is a valid one for ARP.
+ */
+static int
+valid_type(int type)
+{
+
+	switch (type) {
+	case IFT_ETHER:
+	case IFT_FDDI:
+	case IFT_INFINIBAND:
+	case IFT_ISO88023:
+	case IFT_ISO88024:
+	case IFT_ISO88025:
+	case IFT_L2VLAN:
+	case IFT_BRIDGE:
+		return (1);
+	default:
+		return (0);
+	}
+}
+
+/*
+ * Set an individual arp entry
+ */
+static int
+set(int argc, char **argv)
+{
+	struct sockaddr_in *addr;
+	struct sockaddr_in *dst;	/* what are we looking for */
+	struct sockaddr_dl *sdl;
+	struct rt_msghdr *rtm;
+	struct ether_addr *ea;
+	char *host = argv[0], *eaddr = argv[1];
+	struct sockaddr_dl sdl_m;
+
+	argc -= 2;
+	argv += 2;
+
+	bzero(&sdl_m, sizeof(sdl_m));
+	sdl_m.sdl_len = sizeof(sdl_m);
+	sdl_m.sdl_family = AF_LINK;
+
+	dst = getaddr(host);
+	if (dst == NULL)
+		return (1);
+	doing_proxy = flags = expire_time = 0;
+	while (argc-- > 0) {
+		if (strncmp(argv[0], "temp", 4) == 0) {
+			struct timespec tp;
+			int max_age;
+			size_t len = sizeof(max_age);
+
+			clock_gettime(CLOCK_MONOTONIC, &tp);
+			if (sysctlbyname("net.link.ether.inet.max_age",
+			    &max_age, &len, NULL, 0) != 0)
+				err(1, "sysctlbyname");
+			expire_time = tp.tv_sec + max_age;
+		} else if (strncmp(argv[0], "pub", 3) == 0) {
+			flags |= RTF_ANNOUNCE;
+			doing_proxy = 1;
+			if (argc && strncmp(argv[1], "only", 3) == 0) {
+				/*
+				 * Compatibility: in pre FreeBSD 8 times
+				 * the "only" keyword used to mean that
+				 * an ARP entry should be announced, but
+				 * not installed into routing table.
+				 */
+				argc--; argv++;
+			}
+		} else if (strncmp(argv[0], "blackhole", 9) == 0) {
+			if (flags & RTF_REJECT) {
+				printf("Choose one of blackhole or reject, not both.\n");
+			}
+			flags |= RTF_BLACKHOLE;
+		} else if (strncmp(argv[0], "reject", 6) == 0) {
+			if (flags & RTF_BLACKHOLE) {
+				printf("Choose one of blackhole or reject, not both.\n");
+			}
+			flags |= RTF_REJECT;
+		} else if (strncmp(argv[0], "trail", 5) == 0) {
+			/* XXX deprecated and undocumented feature */
+			printf("%s: Sending trailers is no longer supported\n",
+				host);
+		}
+		argv++;
+	}
+	ea = (struct ether_addr *)LLADDR(&sdl_m);
+	if (doing_proxy && !strcmp(eaddr, "auto")) {
+		if (!get_ether_addr(dst->sin_addr.s_addr, ea)) {
+			printf("no interface found for %s\n",
+			       inet_ntoa(dst->sin_addr));
+			return (1);
+		}
+		sdl_m.sdl_alen = ETHER_ADDR_LEN;
+	} else {
+		struct ether_addr *ea1 = ether_aton(eaddr);
+
+		if (ea1 == NULL) {
+			warnx("invalid Ethernet address '%s'", eaddr);
+			return (1);
+		} else {
+			*ea = *ea1;
+			sdl_m.sdl_alen = ETHER_ADDR_LEN;
+		}
+	}
+
+	/*
+	 * In the case a proxy-arp entry is being added for
+	 * a remote end point, the RTF_ANNOUNCE flag in the 
+	 * RTM_GET command is an indication to the kernel
+	 * routing code that the interface associated with
+	 * the prefix route covering the local end of the
+	 * PPP link should be returned, on which ARP applies.
+	 */
+	rtm = rtmsg(RTM_GET, dst, &sdl_m);
+	if (rtm == NULL) {
+		warn("%s", host);
+		return (1);
+	}
+	addr = (struct sockaddr_in *)(rtm + 1);
+	sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr);
+
+	if ((sdl->sdl_family != AF_LINK) ||
+	    (rtm->rtm_flags & RTF_GATEWAY) ||
+	    !valid_type(sdl->sdl_type)) {
+		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, dst, &sdl_m) == NULL);
+}
+
+/*
+ * Display an individual arp entry
+ */
+static int
+get(char *host)
+{
+	struct sockaddr_in *addr;
+
+	addr = getaddr(host);
+	if (addr == NULL)
+		return (1);
+	if (0 == search(addr->sin_addr.s_addr, print_entry)) {
+		printf("%s (%s) -- no entry",
+		    host, inet_ntoa(addr->sin_addr));
+		if (rifname)
+			printf(" on %s", rifname);
+		printf("\n");
+		return (1);
+	}
+	return (0);
+}
+
+/*
+ * Delete an arp entry
+ */
+static int
+delete(char *host)
+{
+	struct sockaddr_in *addr, *dst;
+	struct rt_msghdr *rtm;
+	struct sockaddr_dl *sdl;
+	struct sockaddr_dl sdl_m;
+
+	dst = getaddr(host);
+	if (dst == NULL)
+		return (1);
+
+	/*
+	 * Perform a regular entry delete first.
+	 */
+	flags &= ~RTF_ANNOUNCE;
+
+	/*
+	 * setup the data structure to notify the kernel
+	 * it is the ARP entry the RTM_GET is interested
+	 * in
+	 */
+	bzero(&sdl_m, sizeof(sdl_m));
+	sdl_m.sdl_len = sizeof(sdl_m);
+	sdl_m.sdl_family = AF_LINK;
+
+	for (;;) {	/* try twice */
+		rtm = rtmsg(RTM_GET, dst, &sdl_m);
+		if (rtm == NULL) {
+			warn("%s", host);
+			return (1);
+		}
+		addr = (struct sockaddr_in *)(rtm + 1);
+		sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr);
+
+		/*
+		 * With the new L2/L3 restructure, the route 
+		 * returned is a prefix route. The important
+		 * piece of information from the previous
+		 * RTM_GET is the interface index. In the
+		 * case of ECMP, the kernel will traverse
+		 * the route group for the given entry.
+		 */
+		if (sdl->sdl_family == AF_LINK &&
+		    !(rtm->rtm_flags & RTF_GATEWAY) &&
+		    valid_type(sdl->sdl_type) ) {
+			addr->sin_addr.s_addr = dst->sin_addr.s_addr;
+			break;
+		}
+
+		/*
+		 * Regualar entry delete failed, now check if there
+		 * is a proxy-arp entry to remove.
+		 */
+		if (flags & RTF_ANNOUNCE) {
+			fprintf(stderr, "delete: cannot locate %s\n",host);
+			return (1);
+		}
+
+		flags |= RTF_ANNOUNCE;
+	}
+	rtm->rtm_flags |= RTF_LLDATA;
+	if (rtmsg(RTM_DELETE, dst, NULL) != NULL) {
+		printf("%s (%s) deleted\n", host, inet_ntoa(addr->sin_addr));
+		return (0);
+	}
+	return (1);
+}
+
+
+/*
+ * Search the arp table and do some action on matching entries
+ */
+static int
+search(u_long addr, action_fn *action)
+{
+	int mib[6];
+	size_t needed;
+	char *lim, *buf, *next;
+	struct rt_msghdr *rtm;
+	struct sockaddr_in *sin2;
+	struct sockaddr_dl *sdl;
+	char ifname[IF_NAMESIZE];
+	int st, found_entry = 0;
+
+	mib[0] = CTL_NET;
+	mib[1] = PF_ROUTE;
+	mib[2] = 0;
+	mib[3] = AF_INET;
+	mib[4] = NET_RT_FLAGS;
+#ifdef RTF_LLINFO
+	mib[5] = RTF_LLINFO;
+#else
+	mib[5] = 0;
+#endif	
+	if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
+		err(1, "route-sysctl-estimate");
+	if (needed == 0)	/* empty table */
+		return 0;
+	buf = NULL;
+	for (;;) {
+		buf = reallocf(buf, needed);
+		if (buf == NULL)
+			errx(1, "could not reallocate memory");
+		st = sysctl(mib, 6, buf, &needed, NULL, 0);
+		if (st == 0 || errno != ENOMEM)
+			break;
+		needed += needed / 8;
+	}
+	if (st == -1)
+		err(1, "actual retrieval of routing table");
+	lim = buf + needed;
+	for (next = buf; next < lim; next += rtm->rtm_msglen) {
+		rtm = (struct rt_msghdr *)next;
+		sin2 = (struct sockaddr_in *)(rtm + 1);
+		sdl = (struct sockaddr_dl *)((char *)sin2 + SA_SIZE(sin2));
+		if (rifname && if_indextoname(sdl->sdl_index, ifname) &&
+		    strcmp(ifname, rifname))
+			continue;
+		if (addr) {
+			if (addr != sin2->sin_addr.s_addr)
+				continue;
+			found_entry = 1;
+		}
+		(*action)(sdl, sin2, rtm);
+	}
+	free(buf);
+	return (found_entry);
+}
+
+/*
+ * Display an arp entry
+ */
+
+static void
+print_entry(struct sockaddr_dl *sdl,
+	struct sockaddr_in *addr, struct rt_msghdr *rtm)
+{
+	const char *host;
+	struct hostent *hp;
+	struct iso88025_sockaddr_dl_data *trld;
+	struct if_nameindex *p;
+	int seg;
+
+	if (ifnameindex == NULL) 
+		if ((ifnameindex = if_nameindex()) == NULL)
+			err(1, "cannot retrieve interface names");
+
+	if (nflag == 0)
+		hp = gethostbyaddr((caddr_t)&(addr->sin_addr),
+		    sizeof addr->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(addr->sin_addr));
+	if (sdl->sdl_alen) {
+		if ((sdl->sdl_type == IFT_ETHER ||
+		    sdl->sdl_type == IFT_L2VLAN ||
+		    sdl->sdl_type == IFT_BRIDGE) &&
+		    sdl->sdl_alen == ETHER_ADDR_LEN)
+			printf("%s", ether_ntoa((struct ether_addr *)LLADDR(sdl)));
+		else {
+			int n = sdl->sdl_nlen > 0 ? sdl->sdl_nlen + 1 : 0;
+
+			printf("%s", link_ntoa(sdl) + n);
+		}
+	} else
+		printf("(incomplete)");
+
+	for (p = ifnameindex; p && ifnameindex->if_index &&
+		 ifnameindex->if_name; p++) {
+		if (p->if_index == sdl->sdl_index) {
+			printf(" on %s", p->if_name);
+			break;
+		}
+	}
+
+	if (rtm->rtm_rmx.rmx_expire == 0)
+		printf(" permanent");
+	else {
+		static struct timespec tp;
+		if (tp.tv_sec == 0)
+			clock_gettime(CLOCK_MONOTONIC, &tp);
+		if ((expire_time = rtm->rtm_rmx.rmx_expire - tp.tv_sec) > 0)
+			printf(" expires in %d seconds", (int)expire_time);
+		else
+			printf(" expired");
+	}
+	if (rtm->rtm_flags & RTF_ANNOUNCE)
+		printf(" published");
+	switch(sdl->sdl_type) {
+	case IFT_ETHER:
+                printf(" [ethernet]");
+                break;
+	case IFT_ISO88025:
+                printf(" [token-ring]");
+		trld = SDL_ISO88025(sdl);
+		if (trld->trld_rcf != 0) {
+			printf(" rt=%x", ntohs(trld->trld_rcf));
+			for (seg = 0;
+			     seg < ((TR_RCF_RIFLEN(trld->trld_rcf) - 2 ) / 2);
+			     seg++) 
+				printf(":%x", ntohs(*(trld->trld_route[seg])));
+		}
+                break;
+	case IFT_FDDI:
+                printf(" [fddi]");
+                break;
+	case IFT_ATM:
+                printf(" [atm]");
+                break;
+	case IFT_L2VLAN:
+		printf(" [vlan]");
+		break;
+	case IFT_IEEE1394:
+                printf(" [firewire]");
+                break;
+	case IFT_BRIDGE:
+		printf(" [bridge]");
+		break;
+	case IFT_INFINIBAND:
+		printf(" [infiniband]");
+		break;
+	default:
+		break;
+        }
+		
+	printf("\n");
+
+}
+
+/*
+ * Nuke an arp entry
+ */
+static void
+nuke_entry(struct sockaddr_dl *sdl __unused,
+	struct sockaddr_in *addr, struct rt_msghdr *rtm)
+{
+	char ip[20];
+
+	if (rtm->rtm_flags & RTF_PINNED)
+		return;
+
+	snprintf(ip, sizeof(ip), "%s", inet_ntoa(addr->sin_addr));
+	delete(ip);
+}
+
+static void
+usage(void)
+{
+	fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n",
+		"usage: arp [-n] [-i interface] hostname",
+		"       arp [-n] [-i interface] -a",
+		"       arp -d hostname [pub]",
+		"       arp -d [-i interface] -a",
+		"       arp -s hostname ether_addr [temp] [reject | blackhole] [pub [only]]",
+		"       arp -S hostname ether_addr [temp] [reject | blackhole] [pub [only]]",
+		"       arp -f filename");
+	exit(1);
+}
+
+static struct rt_msghdr *
+rtmsg(int cmd, struct sockaddr_in *dst, struct sockaddr_dl *sdl)
+{
+	static int seq;
+	int rlen;
+	int l;
+	struct sockaddr_in so_mask, *som = &so_mask;
+	static int s = -1;
+	static pid_t pid;
+
+	static struct	{
+		struct	rt_msghdr m_rtm;
+		char	m_space[512];
+	}	m_rtmsg;
+
+	struct rt_msghdr *rtm = &m_rtmsg.m_rtm;
+	char *cp = m_rtmsg.m_space;
+
+	if (s < 0) {	/* first time: open socket, get pid */
+		s = socket(PF_ROUTE, SOCK_RAW, 0);
+		if (s < 0)
+			err(1, "socket");
+		pid = getpid();
+	}
+	bzero(&so_mask, sizeof(so_mask));
+	so_mask.sin_len = 8;
+	so_mask.sin_addr.s_addr = 0xffffffff;
+
+	errno = 0;
+	/*
+	 * XXX RTM_DELETE relies on a previous RTM_GET to fill the buffer
+	 * appropriately.
+	 */
+	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:
+		errx(1, "internal wrong cmd");
+	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 | RTF_LLDATA);
+		if (doing_proxy) {
+			rtm->rtm_addrs |= RTA_NETMASK;
+			rtm->rtm_flags &= ~RTF_HOST;
+		}
+		/* FALLTHROUGH */
+	case RTM_GET:
+		rtm->rtm_addrs |= RTA_DST;
+	}
+#define NEXTADDR(w, s)					   \
+	do {						   \
+		if ((s) != NULL && rtm->rtm_addrs & (w)) { \
+			bcopy((s), cp, sizeof(*(s)));	   \
+			cp += SA_SIZE(s);		   \
+		}					   \
+	} while (0)
+
+	NEXTADDR(RTA_DST, dst);
+	NEXTADDR(RTA_GATEWAY, sdl);
+	NEXTADDR(RTA_NETMASK, som);
+
+	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) {
+			warn("writing to routing socket");
+			return (NULL);
+		}
+	}
+	do {
+		l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg));
+	} while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid));
+	if (l < 0)
+		warn("read from routing socket");
+	return (rtm);
+}
+
+/*
+ * get_ether_addr - get the hardware address of an interface on the
+ * the same subnet as ipaddr.
+ */
+#define MAX_IFS		32
+
+static int
+get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr)
+{
+	struct ifreq *ifr, *ifend, *ifp;
+	in_addr_t ina, mask;
+	struct sockaddr_dl *dla;
+	struct ifreq ifreq;
+	struct ifconf ifc;
+	struct ifreq ifs[MAX_IFS];
+	int sock;
+	int retval = 0;
+
+	sock = socket(AF_INET, SOCK_DGRAM, 0);
+	if (sock < 0)
+		err(1, "socket");
+
+	ifc.ifc_len = sizeof(ifs);
+	ifc.ifc_req = ifs;
+	if (ioctl(sock, SIOCGIFCONF, &ifc) < 0) {
+		warnx("ioctl(SIOCGIFCONF)");
+		goto done;
+	}
+
+#define NEXTIFR(i)						\
+    ((struct ifreq *)((char *)&(i)->ifr_addr			\
+	+ MAX((i)->ifr_addr.sa_len, sizeof((i)->ifr_addr))) )
+
+	/*
+	 * Scan through looking for an interface with an Internet
+	 * address on the same subnet as `ipaddr'.
+	 */
+	ifend = (struct ifreq *)(ifc.ifc_buf + ifc.ifc_len);
+	for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr) ) {
+		if (ifr->ifr_addr.sa_family != AF_INET)
+			continue;
+		strncpy(ifreq.ifr_name, ifr->ifr_name,
+			sizeof(ifreq.ifr_name));
+		ifreq.ifr_addr = ifr->ifr_addr;
+		/*
+		 * Check that the interface is up,
+		 * and not point-to-point or loopback.
+		 */
+		if (ioctl(sock, SIOCGIFFLAGS, &ifreq) < 0)
+			continue;
+		if ((ifreq.ifr_flags &
+		     (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT|
+				IFF_LOOPBACK|IFF_NOARP))
+		     != (IFF_UP|IFF_BROADCAST))
+			continue;
+		/*
+		 * Get its netmask and check that it's on 
+		 * the right subnet.
+		 */
+		if (ioctl(sock, SIOCGIFNETMASK, &ifreq) < 0)
+			continue;
+		mask = ((struct sockaddr_in *)
+			&ifreq.ifr_addr)->sin_addr.s_addr;
+		ina = ((struct sockaddr_in *)
+			&ifr->ifr_addr)->sin_addr.s_addr;
+		if ((ipaddr & mask) == (ina & mask))
+			break; /* ok, we got it! */
+	}
+
+	if (ifr >= ifend)
+		goto done;
+
+	/*
+	 * Now scan through again looking for a link-level address
+	 * for this interface.
+	 */
+	ifp = ifr;
+	for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr))
+		if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0 &&
+		    ifr->ifr_addr.sa_family == AF_LINK)
+			break;
+	if (ifr >= ifend)
+		goto done;
+	/*
+	 * Found the link-level address - copy it out
+	 */
+	dla = (struct sockaddr_dl *) &ifr->ifr_addr;
+	memcpy(hwaddr,  LLADDR(dla), dla->sdl_alen);
+	printf("using interface %s for proxy with address ",
+		ifp->ifr_name);
+	printf("%s\n", ether_ntoa(hwaddr));
+	retval = dla->sdl_alen;
+done:
+	close(sock);
+	return (retval);
+}