/*
 * icmp.c
 * 
 * ICMP Protocol engine - for sending out pings and receiving responses.
 */

/*
 * Copyright (c) 1997, 1998 The Internet Software Consortium.
 * 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. Neither the name of The Internet Software Consortium 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 INTERNET SOFTWARE CONSORTIUM 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 INTERNET SOFTWARE CONSORTIUM 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.
 *
 * This software has been written for the Internet Software Consortium
 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
 * Enterprises.  To learn more about the Internet Software Consortium,
 * see ``http://www.vix.com/isc''.  To learn more about Vixie
 * Enterprises, see ``http://www.vix.com''.
 */

#include "dhcpd.h"
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>

static int icmp_protocol_initialized;
static int icmp_protocol_fd;

/* Initialize the ICMP protocol. */

void
icmp_startup(int routep, void (*handler) (struct iaddr, u_int8_t *, int))
{
	struct protoent *proto;
	int protocol = 1, state;

	/* Only initialize icmp once. */
	if (icmp_protocol_initialized)
		error("attempted to reinitialize icmp protocol");
	icmp_protocol_initialized = 1;

	/* Get the protocol number (should be 1). */
	proto = getprotobyname("icmp");
	if (proto)
		protocol = proto->p_proto;

	/* Get a raw socket for the ICMP protocol. */
	icmp_protocol_fd = socket(AF_INET, SOCK_RAW, protocol);
	if (icmp_protocol_fd < 0)
		error("unable to create icmp socket: %m");

	/* Make sure it does routing... */
	state = 0;
	if (setsockopt(icmp_protocol_fd, SOL_SOCKET, SO_DONTROUTE,
	    (char *) &state, sizeof state) < 0)
		error("Unable to disable SO_DONTROUTE on ICMP socket: %m");

	add_protocol("icmp", icmp_protocol_fd, icmp_echoreply,
	    (void *) handler);
}

int 
icmp_echorequest(struct iaddr *addr)
{
	struct sockaddr_in to;
	struct icmp icmp;
	int status;

	if (!icmp_protocol_initialized)
		error("attempt to use ICMP protocol before initialization.");

	memset(&to, 0, sizeof to);
	to.sin_len = sizeof to;
	to.sin_family = AF_INET;
	to.sin_port = 0;	/* unused. */
	memcpy(&to.sin_addr, addr->iabuf, sizeof to.sin_addr);	/* XXX */

	icmp.icmp_type = ICMP_ECHO;
	icmp.icmp_code = 0;
	icmp.icmp_cksum = 0;
	icmp.icmp_seq = 0;
#ifdef PTRSIZE_64BIT
	icmp.icmp_id = (((u_int32_t) (u_int64_t) addr) ^
	    (u_int32_t) (((u_int64_t) addr) >> 32));
#else
	icmp.icmp_id = (u_int32_t) addr;
#endif

	icmp.icmp_cksum = wrapsum(checksum((unsigned char *) &icmp,
	    sizeof icmp, 0));

	/* Send the ICMP packet... */
	status = sendto(icmp_protocol_fd, (char *) &icmp, sizeof icmp, 0,
	    (struct sockaddr *) & to, sizeof to);
	if (status < 0)
		warn("icmp_echorequest %s: %m", inet_ntoa(to.sin_addr));

	if (status != sizeof icmp)
		return 0;
	return 1;
}

void 
icmp_echoreply(struct protocol *protocol)
{
	void (*handler)(struct iaddr, u_int8_t *, int);
	struct sockaddr_in from;
	u_int8_t icbuf[1500];
	struct icmp *icfrom;
	int status, len;
	socklen_t salen;
	struct iaddr ia;

	salen = sizeof from;
	status = recvfrom(protocol->fd, (char *)icbuf, sizeof icbuf, 0,
	    (struct sockaddr *)&from, &salen);
	if (status < 0) {
		warn("icmp_echoreply: %m");
		return;
	}

	/* Probably not for us. */
	if (status < (sizeof(struct ip)) + (sizeof *icfrom))
		return;

	len = status - sizeof(struct ip);
	icfrom = (struct icmp *) (icbuf + sizeof(struct ip));

	/* Silently discard ICMP packets that aren't echoreplies. */
	if (icfrom->icmp_type != ICMP_ECHOREPLY)
		return;

	/* If we were given a second-stage handler, call it. */
	if (protocol->local) {
		handler = ((void (*)(struct iaddr, u_int8_t *, int))
		    protocol->local);
		memcpy(ia.iabuf, &from.sin_addr, sizeof from.sin_addr);
		ia.len = sizeof from.sin_addr;
		(*handler)(ia, icbuf, len);
	}
}