networking/arp.c

/* vi: set sw=4 ts=4: */
/*
 * arp.c - Manipulate the system ARP cache
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 * Author: Fred N. van Kempen, <waltje at uwalt.nl.mugnet.org>
 * Busybox port: Paul van Gool <pvangool at mimotech.com>
 *
 * modified for getopt32 by Arne Bernin <arne [at] alamut.de>
 */
//config:config ARP
//config:	bool "arp (11 kb)"
//config:	default y
//config:	select PLATFORM_LINUX
//config:	help
//config:	Manipulate the system ARP cache.

//applet:IF_ARP(APPLET(arp, BB_DIR_SBIN, BB_SUID_DROP))

//kbuild:lib-$(CONFIG_ARP) += arp.o interface.o

//usage:#define arp_trivial_usage
//usage:     "\n[-vn]	[-H HWTYPE] [-i IF] -a [HOSTNAME]"
//usage:     "\n[-v]		    [-i IF] -d HOSTNAME [pub]"
//usage:     "\n[-v]	[-H HWTYPE] [-i IF] -s HOSTNAME HWADDR [temp]"
//usage:     "\n[-v]	[-H HWTYPE] [-i IF] -s HOSTNAME HWADDR [netmask MASK] pub"
//usage:     "\n[-v]	[-H HWTYPE] [-i IF] -Ds HOSTNAME IFACE [netmask MASK] pub"
//usage:#define arp_full_usage "\n\n"
//usage:       "Manipulate ARP cache\n"
//usage:       "\n	-a		Display (all) hosts"
//usage:       "\n	-d		Delete ARP entry"
//usage:       "\n	-s		Set new entry"
//usage:       "\n	-v		Verbose"
//usage:       "\n	-n		Don't resolve names"
//usage:       "\n	-i IF		Network interface"
//usage:       "\n	-D		Read HWADDR from IFACE"
//usage:       "\n	-A,-p AF	Protocol family"
//usage:       "\n	-H HWTYPE	Hardware address type"

#include "libbb.h"
#include "common_bufsiz.h"
#include "inet_common.h"

#include <arpa/inet.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <netinet/ether.h>
#include <netpacket/packet.h>

#define DEBUG 0

#define DFLT_AF "inet"
#define DFLT_HW "ether"

enum {
	ARP_OPT_A = (1 << 0),
	ARP_OPT_p = (1 << 1),
	ARP_OPT_H = (1 << 2),
	ARP_OPT_t = (1 << 3),
	ARP_OPT_i = (1 << 4),
	ARP_OPT_a = (1 << 5),
	ARP_OPT_d = (1 << 6),
	ARP_OPT_n = (1 << 7), /* do not resolve addresses */
	ARP_OPT_D = (1 << 8), /* HW-address is devicename */
	ARP_OPT_s = (1 << 9),
	ARP_OPT_v = (1 << 10) * DEBUG, /* debugging output flag */
};

enum {
	sockfd = 3, /* active socket descriptor */
};

struct globals {
	const struct aftype *ap; /* current address family */
	const struct hwtype *hw; /* current hardware type */
	const char *device;      /* current device */
	smallint hw_set;         /* flag if hw-type was set (-H) */
} FIX_ALIASING;
#define G (*(struct globals*)bb_common_bufsiz1)
#define ap         (G.ap        )
#define hw         (G.hw        )
#define device     (G.device    )
#define hw_set     (G.hw_set    )
#define INIT_G() do { \
	setup_common_bufsiz(); \
	device = ""; \
} while (0)


static const char options[] ALIGN1 =
	"pub\0"
	"priv\0"
	"temp\0"
	"trail\0"
	"dontpub\0"
	"auto\0"
	"dev\0"
	"netmask\0";

/* Delete an entry from the ARP cache. */
/* Called only from main, once */
static int arp_del(char **args)
{
	char *host;
	struct arpreq req;
	struct sockaddr sa;
	int flags = 0;
	int err;

	memset(&req, 0, sizeof(req));

	/* Resolve the host name. */
	host = *args;
	if (ap->input(host, &sa) < 0) {
		bb_herror_msg_and_die("%s", host);
	}

	/* If a host has more than one address, use the correct one! */
	memcpy(&req.arp_pa, &sa, sizeof(struct sockaddr));

	if (hw_set)
		req.arp_ha.sa_family = hw->type;

	req.arp_flags = ATF_PERM;
	args++;
	while (*args != NULL) {
		switch (index_in_strings(options, *args)) {
		case 0: /* "pub" */
			flags |= 1;
			args++;
			break;
		case 1: /* "priv" */
			flags |= 2;
			args++;
			break;
		case 2: /* "temp" */
			req.arp_flags &= ~ATF_PERM;
			args++;
			break;
		case 3: /* "trail" */
			req.arp_flags |= ATF_USETRAILERS;
			args++;
			break;
		case 4: /* "dontpub" */
#ifdef HAVE_ATF_DONTPUB
			req.arp_flags |= ATF_DONTPUB;
#else
			bb_error_msg("feature ATF_DONTPUB is not supported");
#endif
			args++;
			break;
		case 5: /* "auto" */
#ifdef HAVE_ATF_MAGIC
			req.arp_flags |= ATF_MAGIC;
#else
			bb_error_msg("feature ATF_MAGIC is not supported");
#endif
			args++;
			break;
		case 6: /* "dev" */
			if (*++args == NULL)
				bb_show_usage();
			device = *args;
			args++;
			break;
		case 7: /* "netmask" */
			if (*++args == NULL)
				bb_show_usage();
			if (strcmp(*args, "255.255.255.255") != 0) {
				host = *args;
				if (ap->input(host, &sa) < 0) {
					bb_herror_msg_and_die("%s", host);
				}
				memcpy(&req.arp_netmask, &sa, sizeof(struct sockaddr));
				req.arp_flags |= ATF_NETMASK;
			}
			args++;
			break;
		default:
			bb_show_usage();
			break;
		}
	}
	if (flags == 0)
		flags = 3;

	strncpy_IFNAMSIZ(req.arp_dev, device);

	err = -1;

	/* Call the kernel. */
	if (flags & 2) {
		if (option_mask32 & ARP_OPT_v)
			bb_error_msg("SIOCDARP(nopub)");
		err = ioctl(sockfd, SIOCDARP, &req);
		if (err < 0) {
			if (errno == ENXIO) {
				if (flags & 1)
					goto nopub;
				printf("No ARP entry for %s\n", host);
				return -1;
			}
			bb_perror_msg_and_die("SIOCDARP(priv)");
		}
	}
	if ((flags & 1) && err) {
 nopub:
		req.arp_flags |= ATF_PUBL;
		if (option_mask32 & ARP_OPT_v)
			bb_error_msg("SIOCDARP(pub)");
		if (ioctl(sockfd, SIOCDARP, &req) < 0) {
			if (errno == ENXIO) {
				printf("No ARP entry for %s\n", host);
				return -1;
			}
			bb_perror_msg_and_die("SIOCDARP(pub)");
		}
	}
	return 0;
}

/* Get the hardware address to a specified interface name */
static void arp_getdevhw(char *ifname, struct sockaddr *sa)
{
	struct ifreq ifr;
	const struct hwtype *xhw;

	strncpy_IFNAMSIZ(ifr.ifr_name, ifname);
	ioctl_or_perror_and_die(sockfd, SIOCGIFHWADDR, &ifr,
					"can't get HW-Address for '%s'", ifname);
	if (hw_set && (ifr.ifr_hwaddr.sa_family != hw->type)) {
		bb_error_msg_and_die("protocol type mismatch");
	}
	memcpy(sa, &(ifr.ifr_hwaddr), sizeof(struct sockaddr));

	if (option_mask32 & ARP_OPT_v) {
		xhw = get_hwntype(ifr.ifr_hwaddr.sa_family);
		if (!xhw || !xhw->print) {
			xhw = get_hwntype(-1);
		}
		bb_error_msg("device '%s' has HW address %s '%s'",
				ifname, xhw->name,
				xhw->print((unsigned char *) &ifr.ifr_hwaddr.sa_data));
	}
}

/* Set an entry in the ARP cache. */
/* Called only from main, once */
static int arp_set(char **args)
{
	char *host;
	struct arpreq req;
	struct sockaddr sa;
	int flags;

	memset(&req, 0, sizeof(req));

	host = *args++;
	if (ap->input(host, &sa) < 0) {
		bb_herror_msg_and_die("%s", host);
	}
	/* If a host has more than one address, use the correct one! */
	memcpy(&req.arp_pa, &sa, sizeof(struct sockaddr));

	/* Fetch the hardware address. */
	if (*args == NULL) {
		bb_error_msg_and_die("need hardware address");
	}
	if (option_mask32 & ARP_OPT_D) {
		arp_getdevhw(*args++, &req.arp_ha);
	} else {
		if (hw->input(*args++, &req.arp_ha) < 0) {
			bb_error_msg_and_die("invalid hardware address");
		}
	}

	/* Check out any modifiers. */
	flags = ATF_PERM | ATF_COM;
	while (*args != NULL) {
		switch (index_in_strings(options, *args)) {
		case 0: /* "pub" */
			flags |= ATF_PUBL;
			args++;
			break;
		case 1: /* "priv" */
			flags &= ~ATF_PUBL;
			args++;
			break;
		case 2: /* "temp" */
			flags &= ~ATF_PERM;
			args++;
			break;
		case 3: /* "trail" */
			flags |= ATF_USETRAILERS;
			args++;
			break;
		case 4: /* "dontpub" */
#ifdef HAVE_ATF_DONTPUB
			flags |= ATF_DONTPUB;
#else
			bb_error_msg("feature ATF_DONTPUB is not supported");
#endif
			args++;
			break;
		case 5: /* "auto" */
#ifdef HAVE_ATF_MAGIC
			flags |= ATF_MAGIC;
#else
			bb_error_msg("feature ATF_MAGIC is not supported");
#endif
			args++;
			break;
		case 6: /* "dev" */
			if (*++args == NULL)
				bb_show_usage();
			device = *args;
			args++;
			break;
		case 7: /* "netmask" */
			if (*++args == NULL)
				bb_show_usage();
			if (strcmp(*args, "255.255.255.255") != 0) {
				host = *args;
				if (ap->input(host, &sa) < 0) {
					bb_herror_msg_and_die("%s", host);
				}
				memcpy(&req.arp_netmask, &sa, sizeof(struct sockaddr));
				flags |= ATF_NETMASK;
			}
			args++;
			break;
		default:
			bb_show_usage();
			break;
		}
	}

	/* Fill in the remainder of the request. */
	req.arp_flags = flags;

	strncpy_IFNAMSIZ(req.arp_dev, device);

	/* Call the kernel. */
	if (option_mask32 & ARP_OPT_v)
		bb_error_msg("SIOCSARP()");
	xioctl(sockfd, SIOCSARP, &req);
	return 0;
}


/* Print the contents of an ARP request block. */
static void
arp_disp(const char *name, char *ip, int type, int arp_flags,
		char *hwa, char *mask, char *dev)
{
	static const int arp_masks[] = {
		ATF_PERM, ATF_PUBL,
#ifdef HAVE_ATF_MAGIC
		ATF_MAGIC,
#endif
#ifdef HAVE_ATF_DONTPUB
		ATF_DONTPUB,
#endif
		ATF_USETRAILERS,
	};
	static const char arp_labels[] ALIGN1 = "PERM\0""PUP\0"
#ifdef HAVE_ATF_MAGIC
		"AUTO\0"
#endif
#ifdef HAVE_ATF_DONTPUB
		"DONTPUB\0"
#endif
		"TRAIL\0"
	;

	const struct hwtype *xhw;

	xhw = get_hwntype(type);
	if (xhw == NULL)
		xhw = get_hwtype(DFLT_HW);

	printf("%s (%s) at ", name, ip);

	if (!(arp_flags & ATF_COM)) {
		if (arp_flags & ATF_PUBL)
			printf("* ");
		else
			printf("<incomplete> ");
	} else {
		printf("%s [%s] ", hwa, xhw->name);
	}

	if (arp_flags & ATF_NETMASK)
		printf("netmask %s ", mask);

	print_flags_separated(arp_masks, arp_labels, arp_flags, " ");
	printf(" on %s\n", dev);
}

/* Display the contents of the ARP cache in the kernel. */
/* Called only from main, once */
static int arp_show(char *name)
{
	const char *host;
	const char *hostname;
	FILE *fp;
	struct sockaddr sa;
	int type, flags;
	int num;
	unsigned entries = 0, shown = 0;
	char ip[128];
	char hwa[128];
	char mask[128];
	char line[128];
	char dev[128];

	host = NULL;
	if (name != NULL) {
		/* Resolve the host name. */
		if (ap->input(name, &sa) < 0) {
			bb_herror_msg_and_die("%s", name);
		}
		host = xstrdup(ap->sprint(&sa, 1));
	}
	fp = xfopen_for_read("/proc/net/arp");
	/* Bypass header -- read one line */
	fgets(line, sizeof(line), fp);

	/* Read the ARP cache entries. */
	while (fgets(line, sizeof(line), fp)) {

		mask[0] = '-'; mask[1] = '\0';
		dev[0] = '-'; dev[1] = '\0';
		/* All these strings can't overflow
		 * because fgets above reads limited amount of data */
		num = sscanf(line, "%s 0x%x 0x%x %s %s %s\n",
					ip, &type, &flags, hwa, mask, dev);
		if (num < 4)
			break;

		entries++;
		/* if the user specified hw-type differs, skip it */
		if (hw_set && (type != hw->type))
			continue;

		/* if the user specified address differs, skip it */
		if (host && strcmp(ip, host) != 0)
			continue;

		/* if the user specified device differs, skip it */
		if (device[0] && strcmp(dev, device) != 0)
			continue;

		shown++;
		/* This IS ugly but it works -be */
		hostname = "?";
		if (!(option_mask32 & ARP_OPT_n)) {
			if (ap->input(ip, &sa) < 0)
				hostname = ip;
			else
				hostname = ap->sprint(&sa, (option_mask32 & ARP_OPT_n) | 0x8000);
			if (strcmp(hostname, ip) == 0)
				hostname = "?";
		}

		arp_disp(hostname, ip, type, flags, hwa, mask, dev);
	}
	if (option_mask32 & ARP_OPT_v)
		printf("Entries: %u\tSkipped: %u\tFound: %u\n",
				entries, entries - shown, shown);

	if (!shown) {
		if (hw_set || host || device[0])
			printf("No match found in %u entries\n", entries);
	}
	if (ENABLE_FEATURE_CLEAN_UP) {
		free((char*)host);
		fclose(fp);
	}
	return 0;
}

int arp_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int arp_main(int argc UNUSED_PARAM, char **argv)
{
	const char *hw_type;
	const char *protocol;
	unsigned opts;

	INIT_G();

	xmove_fd(xsocket(AF_INET, SOCK_DGRAM, 0), sockfd);

	ap = get_aftype(DFLT_AF);
	/* Defaults are always supported */
	//if (!ap)
	//	bb_error_msg_and_die("%s: %s not supported", DFLT_AF, "address family");
	hw = get_hwtype(DFLT_HW);
	//if (!hw)
	//	bb_error_msg_and_die("%s: %s not supported", DFLT_HW, "hardware type");

	opts = getopt32(argv, "A:p:H:t:i:adnDsv", &protocol, &protocol,
				 &hw_type, &hw_type, &device);
	argv += optind;
	if (opts & (ARP_OPT_A | ARP_OPT_p)) {
		ap = get_aftype(protocol);
		if (!ap)
			bb_error_msg_and_die("%s: unknown %s", protocol, "address family");
	}
	if (opts & (ARP_OPT_H | ARP_OPT_t)) {
		hw = get_hwtype(hw_type);
		if (!hw)
			bb_error_msg_and_die("%s: unknown %s", hw_type, "hardware type");
		hw_set = 1;
	}
	//if (opts & ARP_OPT_i)... -i

	if (ap->af != AF_INET) {
		bb_error_msg_and_die("%s: kernel only supports 'inet'", ap->name);
	}
	if (hw->alen <= 0) {
		bb_error_msg_and_die("%s: %s without ARP support",
				hw->name, "hardware type");
	}

	/* Now see what we have to do here... */
	if (opts & (ARP_OPT_d | ARP_OPT_s)) {
		if (argv[0] == NULL)
			bb_error_msg_and_die("need host name");
		if (opts & ARP_OPT_s)
			return arp_set(argv);
		return arp_del(argv);
	}

	//if (opts & ARP_OPT_a) - default
	return arp_show(argv[0]);
}