/*
 * arping.c
 *
 *		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.
 *
 * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *		2006.08.18	erik quanstrom <quanstro@quanstro.net>
 *				use select instead of signals so timeouts will work.
 *				
 */

#include <stdlib.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <linux/sockios.h>
#include <sys/file.h>
#include <sys/time.h>
#include <sys/ioctl.h>
#include <linux/if.h>
#include <linux/if_arp.h>
#include <sys/uio.h>

#include <netdb.h>
#include <unistd.h>
#include <stdio.h>
#include <ctype.h>
#include <errno.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdarg.h>

#include "SNAPSHOT.h"

static void usage(void) __attribute__((noreturn));

char *device="eth0";
int ifindex;
char *source;
struct in_addr src, dst;
char *target;
int dad, unsolicited, advert;
int quiet;
int count=-1;
int ntosend=-1;
int ntorecv=-1;
int timeout;
struct timeval timeouttv;
int unicasting;
int s;
int broadcast_only;

struct sockaddr_ll me;
struct sockaddr_ll he;

struct timeval start, last;

int sent, brd_sent;
int received, brd_recv, req_recv;

#define MS_TDIFF(tv1,tv2) ( ((tv1).tv_sec-(tv2).tv_sec)*1000 + \
			   ((tv1).tv_usec-(tv2).tv_usec)/1000 )

#define pkttrace(...)	/* fprintf(stderr, __VA_ARGS__) */

void
errexit(int err, const char* fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);
	vfprintf(stderr, fmt, ap);
	va_end(ap);
	exit(err);
}
	
void usage(void)
{
	fprintf(stderr,
 		"Usage: arping [-fqbDUAV] [-c count] [-w timeout] [-I device] [-s source] destination\n"
 		"  -f : quit on first reply\n"
		"  -q : be quiet\n"
 		"  -b : keep broadcasting, don't go unicast\n"
		"  -D : duplicate address detection mode\n"
		"  -U : Unsolicited ARP mode, update your neighbours\n"
		"  -A : ARP answer mode, update your neighbours\n"
		"  -V : print version and exit\n"
		"  -c count : how many packets to send\n"
		"  -w timeout : how long to wait for a reply\n"
		"  -I device : which ethernet device to use (eth0)\n"
		"  -s source : source ip address\n"
		"  destination : ask for what ip address\n"
 		);
	exit(2);
}

int send_pack(int s, struct in_addr src, struct in_addr dst,
	      struct sockaddr_ll *ME, struct sockaddr_ll *HE)
{
	int err;
	struct timeval now;
	unsigned char buf[256];
	struct arphdr *ah = (struct arphdr*)buf;
	unsigned char *p = (unsigned char *)(ah+1);

	ah->ar_hrd = htons(ME->sll_hatype);
	if (ah->ar_hrd == htons(ARPHRD_FDDI))
		ah->ar_hrd = htons(ARPHRD_ETHER);
	ah->ar_pro = htons(ETH_P_IP);
	ah->ar_hln = ME->sll_halen;
	ah->ar_pln = 4;
	ah->ar_op  = advert ? htons(ARPOP_REPLY) : htons(ARPOP_REQUEST);

	memcpy(p, &ME->sll_addr, ah->ar_hln);
	p+=ME->sll_halen;

	memcpy(p, &src, 4);
	p+=4;

	if (advert)
		memcpy(p, &ME->sll_addr, ah->ar_hln);
	else
		memcpy(p, &HE->sll_addr, ah->ar_hln);
	p+=ah->ar_hln;

	memcpy(p, &dst, 4);
	p+=4;

	gettimeofday(&now, NULL);
	pkttrace("sendto->\n");
	err = sendto(s, buf, p-buf, 0, (struct sockaddr*)HE, sizeof(*HE));
	pkttrace("sendto<-\n");
	if (err == p-buf) {
		last = now;
		sent++;
		if (!unicasting)
			brd_sent++;
	}
	return err;
}

void finish(void)
{
	if (!quiet) {
		fflush(stdout);
		fprintf(stderr, "Sent %d probes (%d broadcast(s))\n", sent, brd_sent);
		fprintf(stderr, "Received %d response(s)", received);
		if (brd_recv || req_recv) {
			fprintf(stderr, " (");
			if (req_recv)
				fprintf(stderr, "%d request(s)", req_recv);
			if (brd_recv)
				fprintf(stderr, "%s%d broadcast(s)",
				       req_recv ? ", " : "",
				       brd_recv);
			fprintf(stderr, ")");
		}
		fprintf(stderr, "\n");
	}
	if (dad)
		exit(!!received);
	if (unsolicited)
		exit(0);
	exit(!received);
}

void print_hex(unsigned char *p, int len)
{
	int i;
	for (i=0; i<len-1; i++)
		printf(":");
	if(len)
		printf("%02X", p[i]);
}

int recv_pack(unsigned char *buf, int len, struct sockaddr_ll *FROM)
{
	struct timeval tv;
	struct arphdr *ah = (struct arphdr*)buf;
	unsigned char *p = (unsigned char *)(ah+1);
	struct in_addr src_ip, dst_ip;

	gettimeofday(&tv, NULL);

	/* Filter out wild packets */
	if (FROM->sll_pkttype != PACKET_HOST &&
	    FROM->sll_pkttype != PACKET_BROADCAST &&
	    FROM->sll_pkttype != PACKET_MULTICAST)
		return 0;

	/* Only these types are recognised */
	if (ah->ar_op != htons(ARPOP_REQUEST) &&
	    ah->ar_op != htons(ARPOP_REPLY))
		return 0;

	/* ARPHRD check and this darned FDDI hack here :-( */
	if (ah->ar_hrd != htons(FROM->sll_hatype) &&
	    (FROM->sll_hatype != ARPHRD_FDDI || ah->ar_hrd != htons(ARPHRD_ETHER)))
		return 0;

	/* Protocol must be IP. */
	if (ah->ar_pro != htons(ETH_P_IP))
		return 0;
	if (ah->ar_pln != 4)
		return 0;
	if (ah->ar_hln != me.sll_halen)
		return 0;
	if (len < sizeof(*ah) + 2*(4 + ah->ar_hln))
		return 0;
	memcpy(&src_ip, p+ah->ar_hln, 4);
	memcpy(&dst_ip, p+ah->ar_hln+4+ah->ar_hln, 4);
	if (!dad) {
		if (src_ip.s_addr != dst.s_addr)
			return 0;
		if (src.s_addr != dst_ip.s_addr)
			return 0;
		if (memcmp(p+ah->ar_hln+4, &me.sll_addr, ah->ar_hln))
			return 0;
	} else {
		/* DAD packet was:
		   src_ip = 0 (or some src)
		   src_hw = ME
		   dst_ip = tested address
		   dst_hw = <unspec>

		   We fail, if receive request/reply with:
		   src_ip = tested_address
		   src_hw != ME
		   if src_ip in request was not zero, check
		   also that it matches to dst_ip, otherwise
		   dst_ip/dst_hw do not matter.
		 */
		if (src_ip.s_addr != dst.s_addr)
			return 0;
		if (memcmp(p, &me.sll_addr, me.sll_halen) == 0)
			return 0;
		if (src.s_addr && src.s_addr != dst_ip.s_addr)
			return 0;
	}
	if (!quiet) {
		int s_printed = 0;
		printf("%s ", FROM->sll_pkttype==PACKET_HOST ? "Unicast" : "Broadcast");
		printf("%s from ", ah->ar_op == htons(ARPOP_REPLY) ? "reply" : "request");
		printf("%s [", inet_ntoa(src_ip));
		print_hex(p, ah->ar_hln);
		printf("] ");
		if (dst_ip.s_addr != src.s_addr) {
			printf("for %s ", inet_ntoa(dst_ip));
			s_printed = 1;
		}
		if (memcmp(p+ah->ar_hln+4, me.sll_addr, ah->ar_hln)) {
			if (!s_printed)
				printf("for ");
			printf("[");
			print_hex(p+ah->ar_hln+4, ah->ar_hln);
			printf("]");
		}
		if (last.tv_sec) {
			long usecs = (tv.tv_sec-last.tv_sec) * 1000000 +
				tv.tv_usec-last.tv_usec;
			long msecs = (usecs+500)/1000;
			usecs -= msecs*1000 - 500;
			printf(" %ld.%03ldms\n", msecs, usecs);
		} else {
			printf(" UNSOLICITED?\n");
		}
		fflush(stdout);
	}
	received++;
	if (FROM->sll_pkttype != PACKET_HOST)
		brd_recv++;
	if (ah->ar_op == htons(ARPOP_REQUEST))
		req_recv++;
	if(!broadcast_only) {
		memcpy(he.sll_addr, p, me.sll_halen);
		unicasting=1;
	}
	return 1;
}


unsigned char packet[4096];		// too big for stack on some arch.

void
pktloop(void)
{
	struct sockaddr_ll from;
	socklen_t alen = sizeof(from);
	fd_set rset;
	struct timeval tmo;
	int cc, i;

	for(;;){
		if(ntosend-- == 0)
			break;
		send_pack(s, src, dst, &me, &he);

  		gettimeofday(&tmo, 0);
		if(timeout)
			i = MS_TDIFF(timeouttv, tmo) ;
		else
			i = 1000;
		if(i < 0)
			break;
		if(i > 1000)
			i = 1000;		// maximum select 1s.
		tmo.tv_sec = i/1000;
		tmo.tv_usec = (i%1000)*1000;

		FD_ZERO(&rset);
		FD_SET(s, &rset);
		pkttrace("select %d ; %d\n", (int)tmo.tv_sec, (int)tmo.tv_usec);
		i = select(s+1, &rset, 0, 0, &tmo);
		pkttrace("<- select\n");
		if(i == -1){
			perror("arping: select");
			exit(1);
		}
		if(i == 0){
			gettimeofday(&tmo, 0);
			i =  MS_TDIFF(timeouttv, tmo);
			if(timeout && i <= 0)
				break;
			continue;
		}
		if ((cc = recvfrom(s, packet, sizeof(packet), 0,
				   (struct sockaddr *)&from, &alen)) < 0) {
			perror("arping: recvfrom");
			continue;
		}
		if(recv_pack(packet, cc, &from))
			if(--ntorecv == 0)
				break;
	}
}

int
main(int argc, char **argv)
{
	int ch, onereply;

	while ((ch = getopt(argc, argv, "h?bfDUAqc:w:s:I:V")) != EOF) {
		switch(ch) {
		case 'b':
			broadcast_only = 1;
			break;
		case 'D':
			dad++;
			onereply = 1;
			break;
		case 'U':
			unsolicited++;
			break;
		case 'A':
			advert++;
			unsolicited++;
			break;
		case 'q':
			quiet++;
			break;
		case 'c':
			count = atoi(optarg);
			break;
		case 'w':
			gettimeofday(&timeouttv, 0);
			timeouttv.tv_sec += atoi(optarg);
			timeout = 1;
			break;
		case 'I':
 			device = optarg;
 			break;
 		case 'f':
 			onereply = 1;
			break;
		case 's':
			source = optarg;
			break;
		case 'V':
			printf("arping utility, iputils-ss%s\n", SNAPSHOT);
			exit(0);
		case 'h':
		case '?':
		default:
			usage();
		}
	}
	argc -= optind;
	argv += optind;

	if (argc != 1)
		usage();
	target = *argv;

	if(onereply)
		ntorecv = 1;
	if(timeout)			// strange ping compatability.
		ntorecv = count;
	else
		ntosend = count;

	if (device == 0) {
		fprintf(stderr, "arping: device (option -I) is required\n");
		usage();
	}

	s = socket(PF_PACKET, SOCK_DGRAM, 0);
	if (s < 0) {
		perror("arping: socket");
		exit(2);
	}
	setuid(getuid());

	if (1) {
		struct ifreq ifr;
		memset(&ifr, 0, sizeof(ifr));
		strncpy(ifr.ifr_name, device, IFNAMSIZ-1);
		if (ioctl(s, SIOCGIFINDEX, &ifr) < 0) {
			fprintf(stderr, "arping: unknown iface %s\n", device);
			exit(2);
		}
		ifindex = ifr.ifr_ifindex;

		if (ioctl(s, SIOCGIFFLAGS, (char*)&ifr)) {
			perror("arping: ioctl(SIOCGIFFLAGS)");
			exit(2);
		}
		if (!(ifr.ifr_flags&IFF_UP))
			errexit(2, "Interface \"%s\" is down\n", device);
		if (ifr.ifr_flags&(IFF_NOARP|IFF_LOOPBACK))
			errexit(dad ? 0 : 2, "Interface \"%s\" is not ARPable\n", device);
	}

	if (inet_aton(target, &dst) != 1) {
		struct hostent *hp;
		hp = gethostbyname2(target, AF_INET);
		if (!hp) {
			fprintf(stderr, "arping: unknown host %s\n", target);
			exit(2);
		}
		memcpy(&dst, hp->h_addr, 4);
	}

	if (source && inet_aton(source, &src) != 1) {
		fprintf(stderr, "arping: invalid source %s\n", source);
		exit(2);
	}

	if (!dad && unsolicited && src.s_addr == 0)
		src = dst;
	
	if (!dad || src.s_addr) {
		struct sockaddr_in saddr;
		int probe_fd = socket(AF_INET, SOCK_DGRAM, 0);

		if (probe_fd < 0) {
			perror("arping: socket");
			exit(2);
		}
		if (device) {
			if (setsockopt(probe_fd, SOL_SOCKET, SO_BINDTODEVICE, device, strlen(device)+1) == -1)
				perror("WARNING: interface is ignored");
		}
		memset(&saddr, 0, sizeof(saddr));
		saddr.sin_family = AF_INET;
		if (src.s_addr) {
			saddr.sin_addr = src;
			if (bind(probe_fd, (struct sockaddr*)&saddr, sizeof(saddr)) == -1) {
				perror("arping: bind");
				exit(2);
			}
		} else if (!dad) {
			int on = 1;
			socklen_t alen = sizeof(saddr);

			saddr.sin_port = htons(1025);
			saddr.sin_addr = dst;

			if (setsockopt(probe_fd, SOL_SOCKET, SO_DONTROUTE, (char*)&on, sizeof(on)) == -1)
				perror("WARNING: setsockopt(SO_DONTROUTE)");
			if (connect(probe_fd, (struct sockaddr*)&saddr, sizeof(saddr)) == -1) {
				perror("arping: connect");
				exit(2);
			}
			if (getsockname(probe_fd, (struct sockaddr*)&saddr, &alen) == -1) {
				perror("arping: getsockname");
				exit(2);
			}
			src = saddr.sin_addr;
		}
		close(probe_fd);
	};

	me.sll_family = AF_PACKET;
	me.sll_ifindex = ifindex;
	me.sll_protocol = htons(ETH_P_ARP);
	if (bind(s, (struct sockaddr*)&me, sizeof(me)) == -1) {
		perror("arping: bind");
		exit(2);
	}

	if (1) {
		socklen_t alen = sizeof(me);
		if (getsockname(s, (struct sockaddr*)&me, &alen) == -1) {
			perror("arping: getsockname");
			exit(2);
		}
	}
	if (me.sll_halen == 0)
		errexit(dad ? 0 : 2, "Interface \"%s\" is not ARPable (no ll address)\n", device);

	he = me;
	memset(he.sll_addr, -1, he.sll_halen);

	if (!quiet) {
		fprintf(stderr, "ARPING %s ", inet_ntoa(dst));
		fprintf(stderr, "from %s %s\n",  inet_ntoa(src), device ? : "");
	}

	if (!src.s_addr && !dad)
		errexit(2, "arping: no source address in not-DAD mode\n");

	pktloop();
	finish();
	return 1;		// shut up gcc.
}