deb-mbse/mbtask/ping.c

/*****************************************************************************
 *
 * $Id$
 * Purpose ...............: mbtask - ping functions
 *
 *****************************************************************************
 * Copyright (C) 1997-2002
 *   
 * Michiel Broek		FIDO:		2:280/2802
 * Beekmansbos 10
 * 1971 BV IJmuiden
 * the Netherlands
 *
 * This file is part of MBSE BBS.
 *
 * This BBS 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, or (at your option) any
 * later version.
 *
 * MBSE BBS is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with MBSE BBS; see the file COPYING.  If not, write to the Free
 * Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 *****************************************************************************/

#include "libs.h"
#include "../lib/structs.h"
#include "taskstat.h"
#include "taskutil.h"
#include "ping.h"





/*
 *  Global variables
 */
extern struct taskrec	TCFG;			/* Task config record	*/
int     		ping_isocket;		/* Ping socket		*/
int     		icmp_errs = 0;		/* ICMP error counter	*/
extern int		internet;		/* Internet is down	*/
extern int		rescan;			/* Master rescan flag	*/
int			pingstate = P_INIT;	/* Ping state		*/
int			pingnr = 1;		/* Ping #, 1 or 2	*/
int			pingresult[2];		/* Ping results		*/
char			pingaddress[41];	/* Ping current address	*/
struct in_addr		paddr;			/* Current ping address	*/



static int      icmp4_errcmp(char *, int, struct in_addr *, char *, int, int);
unsigned short  get_rand16(void);
int             ping_send(struct in_addr);
int             ping_receive(struct in_addr);


/* 
 * different names, same thing... be careful, as these are macros... 
 */
#if defined(__FreeBSD__) || defined(__NetBSD__)
# define icmphdr   icmp
# define iphdr     ip
# define ip_saddr  ip_src.s_addr
# define ip_daddr  ip_dst.s_addr
#else
# define ip_saddr  saddr
# define ip_daddr  daddr
# define ip_hl     ihl
# define ip_p      protocol
#endif


#ifdef __linux__
# define icmp_type  type
# define icmp_code  code
# define icmp_cksum checksum
# ifdef icmp_id
#  undef icmp_id
# endif
# define icmp_id    un.echo.id
# ifdef icmp_seq
#  undef icmp_seq
# endif
# define icmp_seq   un.echo.sequence
#endif

#if defined(__FreeBSD__) || defined(__NetBSD__)
# define ICMP_DEST_UNREACH   ICMP_UNREACH
# define ICMP_TIME_EXCEEDED ICMP_TIMXCEED    
#endif

#define ICMP_BASEHDR_LEN  8
#define ICMP4_ECHO_LEN    ICMP_BASEHDR_LEN



/*
 * Takes a packet as send out and a recieved ICMP packet and looks whether the ICMP packet is 
 * an error reply on the sent-out one. packet is only the packet (without IP header).
 * errmsg includes an IP header.
 * to is the destination address of the original packet (the only thing that is actually
 * compared of the IP header). The RFC sais that we get at least 8 bytes of the offending packet.
 * We do not compare more, as this is all we need.
 */
static int icmp4_errcmp(char *packet, int plen, struct in_addr *to, char *errmsg, int elen, int errtype)
{
	struct iphdr	iph;
	struct icmphdr	icmph;
	struct iphdr	eiph;
	char		*data;

	/* XXX: lots of memcpy to avoid unaligned accesses on alpha */
	if (elen < sizeof(struct iphdr))
                return 0;
	memcpy(&iph, errmsg, sizeof(iph));
	if (iph.ip_p != IPPROTO_ICMP || elen < iph.ip_hl * 4 + ICMP_BASEHDR_LEN + sizeof(eiph))
		return 0;
	memcpy(&icmph, errmsg + iph.ip_hl * 4, ICMP_BASEHDR_LEN);
	memcpy(&eiph, errmsg + iph.ip_hl * 4 + ICMP_BASEHDR_LEN, sizeof(eiph));
	if (elen < iph.ip_hl * 4 + ICMP_BASEHDR_LEN + eiph.ip_hl * 4 + 8)
		return 0;
	data = errmsg + iph.ip_hl * 4 + ICMP_BASEHDR_LEN + eiph.ip_hl * 4;
	return icmph.icmp_type == errtype && memcmp(&to->s_addr, &eiph.ip_daddr, sizeof(to->s_addr)) == 0 && 
		memcmp(data, packet, plen < 8 ?plen:8) == 0;
}



unsigned short get_rand16(void)
{
	return random()&0xffff;
}


short			p_sequence = 0;
unsigned short          id;
struct icmphdr          icmpd;
struct sockaddr_in      to;



/*
 * IPv4/ICMPv4 ping. Called from ping (see below)
 */
int ping_send(struct in_addr addr)
{
	int			len;
	int			isock;
#ifdef __linux__
	struct icmp_filter	f;
#else
	struct protoent		*pe;
	int			SOL_IP;
#endif
	unsigned long		sum;
	unsigned short		*ptr;

#ifndef __linux__
        if (!(pe = getprotobyname("ip"))) {
                tasklog('?', "icmp ping: getprotobyname() failed: %s", strerror(errno));
                return -1;
        }
        SOL_IP = pe->p_proto;
#endif

	isock = ping_isocket;
	p_sequence = 1;
	id = (unsigned short)get_rand16(); /* randomize a ping id */

#ifdef __linux__
	/* Fancy ICMP filering -- only on Linux (as far is I know) */
        
	/* In fact, there should be macros for treating icmp_filter, but I haven't found them in Linux 2.2.15.
	 * So, set it manually and unportable ;-) */
	/* This filter lets ECHO_REPLY (0), DEST_UNREACH(3) and TIME_EXCEEDED(11) pass. */
	/* !(0000 1000 0000 1001) = 0xff ff f7 f6 */
	f.data=0xfffff7f6;
	if (setsockopt(isock, SOL_RAW, ICMP_FILTER, &f, sizeof(f)) == -1) {
		if (icmp_errs < ICMP_MAX_ERRS)
			tasklog('?', "$icmp ping: setsockopt() failed %d", isock);
		return -1;
	}
#endif

	icmpd.icmp_type  = ICMP_ECHO;
	icmpd.icmp_code  = 0;
	icmpd.icmp_cksum = 0;
	icmpd.icmp_id    = htons((short)id);
	icmpd.icmp_seq   = htons(p_sequence);

       	/* Checksumming - Algorithm taken from nmap. Thanks... */

	ptr = (unsigned short *)&icmpd;
	sum = 0;

	for (len = 0; len < 4; len++) {
		sum += *ptr++;
	}
	sum = (sum >> 16) + (sum & 0xffff);
	sum += (sum >> 16);
	icmpd.icmp_cksum = ~sum;

	memset(&to, 0, sizeof(to));
	to.sin_family = AF_INET;
	to.sin_port   = 0;
	to.sin_addr   = addr;
	SET_SOCKA_LEN4(to);
	if (sendto(isock, &icmpd, ICMP4_ECHO_LEN, 0, (struct sockaddr *)&to, sizeof(to)) == -1) {
		return -2;
	}
	return 0;
}



int ping_receive(struct in_addr addr)
{
	char                    buf[1024]; 
	int                     isock;
        int                     len;
        struct sockaddr_in      ffrom;
        struct icmphdr          icmpp;
        struct iphdr            iph;
	socklen_t               sl;        
	struct pollfd           pfd;

	isock = ping_isocket;

	pfd.fd = isock;
	pfd.events = POLLIN;
	/*
 	 *  10 mSec is enough, this function is called at regular intervals.
	 */
	if (poll(&pfd, 1, 10) < 0) {
		if (icmp_errs < ICMP_MAX_ERRS)
			tasklog('?', "$poll/select failed");
		return -3; 
	}

	if (pfd.revents & POLLIN || pfd.revents & POLLERR || pfd.revents & POLLHUP || pfd.revents & POLLNVAL) {
		sl = sizeof(ffrom);
		if ((len = recvfrom(isock, &buf, sizeof(buf), 0,(struct sockaddr *)&ffrom, &sl)) != -1) {
			if (len > sizeof(struct iphdr)) {
				memcpy(&iph, buf, sizeof(iph));
				if (len - iph.ip_hl * 4 >= ICMP_BASEHDR_LEN) {
					memcpy(&icmpp, ((unsigned long int *)buf)+iph.ip_hl, sizeof(icmpp));
					if (iph.ip_saddr == addr.s_addr && 
					    icmpp.icmp_type == ICMP_ECHOREPLY &&
					    ntohs(icmpp.icmp_id) == id && 
					    ntohs(icmpp.icmp_seq) <= p_sequence) {
						return 0;
					} else {
						/* No regular echo reply. Maybe an error? */
						if (icmp4_errcmp((char *)&icmpd, ICMP4_ECHO_LEN, 
						    &to.sin_addr, buf, len, ICMP_DEST_UNREACH) ||
						    icmp4_errcmp((char *)&icmpd, ICMP4_ECHO_LEN, 
						    &to.sin_addr, buf, len, ICMP_TIME_EXCEEDED)) {
							return -4;
						}
					}
				}
			}
		} else {
			return -5; /* error */
		}
	}
	return -6; /* no answer */
}



void check_ping(void)
{
    int		    rc;

    /*
     *  If the previous pingstat is still P_SENT, then we now consider it a timeout.
     */
    if (pingstate == P_SENT) {
	pingresult[pingnr] = FALSE;
	icmp_errs++;
	if (icmp_errs < ICMP_MAX_ERRS)
	    tasklog('p', "ping %s seq=%d timeout", pingaddress, p_sequence);
    }

    /*
     *  Check internet connection with ICMP ping
     */
    rc = 0;
    if (pingnr == 1) {
	pingnr = 2;
	if (strlen(TCFG.isp_ping2)) {
	    sprintf(pingaddress, "%s", TCFG.isp_ping2);
	} else {
	    pingstate = P_NONE;
	}
    } else {
	pingnr = 1;
	if (strlen(TCFG.isp_ping1)) {
	    sprintf(pingaddress, "%s", TCFG.isp_ping1);
	} else {
	    pingstate = P_NONE;
	}
    }

    if (inet_aton(pingaddress, &paddr)) {
	rc = ping_send(paddr);
	if (rc) {
	    if (icmp_errs++ < ICMP_MAX_ERRS)
		tasklog('?', "ping send %s rc=%d", pingaddress, rc);
	    pingstate = P_FAIL;
	    pingresult[pingnr] = FALSE;
	} else {
	    pingstate = P_SENT;
	}
    } else {
	if (icmp_errs++ < ICMP_MAX_ERRS)
	    tasklog('?', "Ping address %d is invalid \"%s\"", pingnr, pingaddress);
	pingstate = P_NONE;
    }

    if (pingresult[1] == FALSE && pingresult[2] == FALSE) {
	icmp_errs++;
	if (internet) {
	    tasklog('!', "Internet connection is down");
	    internet = FALSE;
	    sem_set((char *)"scanout", TRUE);
	    RemoveSema((char *)"is_inet");
	    rescan = TRUE;
	}
    } else {
	if (!internet) {
	    tasklog('!', "Internet connection is up");
	    internet = TRUE;
	    sem_set((char *)"scanout", TRUE);
	    CreateSema((char *)"is_inet");
	    rescan = TRUE;
	}
	icmp_errs = 0;
    }
}



void state_ping(void)
{
    int	    rc;

    /*
     * PING state changes
     */
    switch (pingstate) {
	case P_NONE:    pingresult[pingnr] = TRUE;
			break;
	case P_SENT:    rc = ping_receive(paddr);
			if (!rc) {
			    pingstate = P_OK;
			    pingresult[pingnr] = TRUE;
			} else {
			    if (rc != -6)
				tasklog('p', "ping recv %s id=%d rc=%d", pingaddress, id, rc);
			}
			break;
    }
}