Sweep-fix comparing pointers with 0 (and assigning 0 to pointers).

[dragonfly.git] / usr.sbin / mrouted / mtrace.c

/*
 * mtrace.c
 *
 * This tool traces the branch of a multicast tree from a source to a
 * receiver for a particular multicast group and gives statistics
 * about packet rate and loss for each hop along the path.  It can
 * usually be invoked just as
 *
 *      mtrace source
 *
 * to trace the route from that source to the local host for a default
 * group when only the route is desired and not group-specific packet
 * counts.  See the usage line for more complex forms.
 *
 *
 * Released 4 Apr 1995.  This program was adapted by Steve Casner
 * (USC/ISI) from a prototype written by Ajit Thyagarajan (UDel and
 * Xerox PARC).  It attempts to parallel in command syntax and output
 * format the unicast traceroute program written by Van Jacobson (LBL)
 * for the parts where that makes sense.
 * 
 * Copyright (c) 1995 by the University of Southern California
 * All rights reserved.
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation in source and binary forms for any purposes and without
 * fee is hereby granted, provided that the above copyright notice
 * appear in all copies and that both the copyright notice and this
 * permission notice appear in supporting documentation, and that any
 * documentation, advertising materials, and other materials related to
 * such distribution and use acknowledge that the software was developed
 * by the University of Southern California, Information Sciences
 * Institute.  The name of the University may not be used to endorse or
 * promote products derived from this software without specific prior
 * written permission.
 *
 * THE UNIVERSITY OF SOUTHERN CALIFORNIA makes no representations about
 * the suitability of this software for any purpose.  THIS SOFTWARE IS
 * PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Other copyrights might apply to parts of this software and are so
 * noted when applicable.
 *
 * Parts of this software are derived from mrouted, which has the
 * following license:
 * 
 * The mrouted program is covered by the following license.  Use of the
 * mrouted program represents acceptance of these terms and conditions.
 * 
 * 1. STANFORD grants to LICENSEE a nonexclusive and nontransferable
 * license to use, copy and modify the computer software ``mrouted''
 * (hereinafter called the ``Program''), upon the terms and conditions
 * hereinafter set out and until Licensee discontinues use of the Licensed
 * Program.
 * 
 * 2. LICENSEE acknowledges that the Program is a research tool still in
 * the development state, that it is being supplied ``as is,'' without any
 * accompanying services from STANFORD, and that this license is entered
 * into in order to encourage scientific collaboration aimed at further
 * development and application of the Program.
 * 
 * 3. LICENSEE may copy the Program and may sublicense others to use
 * object code copies of the Program or any derivative version of the
 * Program.  All copies must contain all copyright and other proprietary
 * notices found in the Program as provided by STANFORD.  Title to
 * copyright to the Program remains with STANFORD.
 * 
 * 4. LICENSEE may create derivative versions of the Program.  LICENSEE
 * hereby grants STANFORD a royalty-free license to use, copy, modify,
 * distribute and sublicense any such derivative works.  At the time
 * LICENSEE provides a copy of a derivative version of the Program to a
 * third party, LICENSEE shall provide STANFORD with one copy of the
 * source code of the derivative version at no charge to STANFORD.
 * 
 * 5. STANFORD MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR
 * IMPLIED.  By way of example, but not limitation, STANFORD MAKES NO
 * REPRESENTATION OR WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY
 * PARTICULAR PURPOSE OR THAT THE USE OF THE LICENSED PROGRAM WILL NOT
 * INFRINGE ANY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS. STANFORD
 * shall not be held liable for any liability nor for any direct, indirect
 * or consequential damages with respect to any claim by LICENSEE or any
 * third party on account of or arising from this Agreement or use of the
 * Program.
 * 
 * 6. This agreement shall be construed, interpreted and applied in
 * accordance with the State of California and any legal action arising
 * out of this Agreement or use of the Program shall be filed in a court
 * in the State of California.
 * 
 * 7. Nothing in this Agreement shall be construed as conferring rights to
 * use in advertising, publicity or otherwise any trademark or the name
 * of ``Stanford''.
 * 
 * The mrouted program is COPYRIGHT 1989 by The Board of Trustees of
 * Leland Stanford Junior University.
 *
 *
 * The mtrace program has been modified and improved by Xerox
 * Corporation.  Xerox grants to LICENSEE a non-exclusive and
 * non-transferable license to use, copy, and modify the Xerox modified
 * and improved mrouted software on the same terms and conditions which
 * govern the license Stanford and ISI grant with respect to the mtrace
 * program.  These terms and conditions are incorporated in this grant
 * by reference and shall be deemed to have been accepted by LICENSEE
 * to cover its relationship with Xerox Corporation with respect to any
 * use of the Xerox improved program.
 * 
 * The mtrace program is COPYRIGHT 1998 by Xerox Corporation.
 *
 * $FreeBSD: src/usr.sbin/mrouted/mtrace.c,v 1.17.2.3 2002/09/12 16:27:49 nectar Exp $
 */

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <memory.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <sys/param.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/igmp.h>
#include <sys/ioctl.h>
#ifdef SYSV
#include <sys/sockio.h>
#endif
#include <arpa/inet.h>
#include <stdarg.h>
#ifdef SUNOS5
#include <sys/systeminfo.h>
#endif

typedef unsigned int u_int32;   /* XXX */
#include "mtrace.h"

#define DEFAULT_TIMEOUT 3       /* How long to wait before retrying requests */
#define DEFAULT_RETRIES 3       /* How many times to try */
#define DEFAULT_EXTRAHOPS 3     /* How many hops past a non-responding rtr */
#define MAXHOPS 60              /* Don't need more hops than this */
#define UNICAST_TTL 255         /* TTL for unicast response */
#define MULTICAST_TTL1 127      /* Default TTL for multicast query/response */
#define MULTICAST_TTL_INC 32    /* TTL increment for increase after timeout */
#define MULTICAST_TTL_MAX 192   /* Maximum TTL allowed (protect low-BW links */

#define TRUE 1
#define FALSE 0
#define DVMRP_ASK_NEIGHBORS2    5       /* DVMRP msg requesting neighbors */
#define DVMRP_NEIGHBORS2        6       /* reply to above */
#define DVMRP_NF_DOWN           0x10    /* kernel state of interface */
#define DVMRP_NF_DISABLED       0x20    /* administratively disabled */
#define MAX_IP_PACKET_LEN       576
#define MIN_IP_HEADER_LEN       20
#define MAX_IP_HEADER_LEN       60
#define MAX_DVMRP_DATA_LEN \
                ( MAX_IP_PACKET_LEN - MAX_IP_HEADER_LEN - IGMP_MINLEN )

struct resp_buf {
    u_long qtime;               /* Time query was issued */
    u_long rtime;               /* Time response was received */
    int len;                    /* Number of reports or length of data */
    struct igmp igmp;           /* IGMP header */
    union {
        struct {
            struct tr_query q;          /* Query/response header */
            struct tr_resp r[MAXHOPS];  /* Per-hop reports */
        } t;
        char d[MAX_DVMRP_DATA_LEN];     /* Neighbor data */
    } u;
} base, incr[2];

#define qhdr u.t.q
#define resps u.t.r
#define ndata u.d

char *names[MAXHOPS];

/*
 * In mrouted 3.3 and 3.4 (and in some Cisco IOS releases),
 * cache entries can get deleted even if there is traffic
 * flowing, which will reset the per-source/group counters.
 */
#define         BUG_RESET       0x01

/*
 * Also in mrouted 3.3 and 3.4, there's a bug in neighbor
 * version processing which can cause them to believe that
 * the neighbor is constantly resetting.  This causes them
 * to constantly delete all their state.
 */
#define         BUG_RESET2X     0x02

/*
 * Pre-3.7 mrouted's forget to byte-swap their reports.
 */
#define         BUG_SWAP        0x04

/*
 * Pre-3.9 mrouted's forgot a parenthesis in the htonl()
 * on the time calculation so supply bogus times.
 */
#define         BUG_BOGUSTIME   0x08

#define BUG_NOPRINT     (BUG_RESET | BUG_RESET2X)

int bugs[MAXHOPS];                      /* List of bugs noticed at each hop */

struct mtrace {
        struct mtrace   *next;
        struct resp_buf  base, incr[2];
        struct resp_buf *new, *prev;
        int              nresp;
        struct timeval   last;
        int              bugs[MAXHOPS];
        char            *names[MAXHOPS];
        int              lastqid;
};

int timeout = DEFAULT_TIMEOUT;
int nqueries = DEFAULT_RETRIES;
int numeric = FALSE;
int debug = 0;
int passive = FALSE;
int multicast = FALSE;
int unicast = FALSE;
int statint = 10;
int verbose = FALSE;
int tunstats = FALSE;
int weak = FALSE;
int extrahops = DEFAULT_EXTRAHOPS;
int printstats = TRUE;
int sendopts = TRUE;
int lossthresh = 0;
int fflag = FALSE;
int staticqid = 0;

u_int32 defgrp;                         /* Default group if not specified */
u_int32 query_cast;                     /* All routers multicast addr */
u_int32 resp_cast;                      /* Mtrace response multicast addr */

u_int32 lcl_addr = 0;                   /* This host address, in NET order */
u_int32 dst_netmask = 0;                /* netmask to go with qdst */

/*
 * Query/response parameters, all initialized to zero and set later
 * to default values or from options.
 */
u_int32 qsrc = 0;               /* Source address in the query */
u_int32 qgrp = 0;               /* Group address in the query */
u_int32 qdst = 0;               /* Destination (receiver) address in query */
u_char qno  = 0;                /* Max number of hops to query */
u_int32 raddr = 0;              /* Address where response should be sent */
int    qttl = 0;                /* TTL for the query packet */
u_char rttl = 0;                /* TTL for the response packet */
u_int32 gwy = 0;                /* User-supplied last-hop router address */
u_int32 tdst = 0;               /* Address where trace is sent (last-hop) */

char s1[19];            /* buffers to hold the string representations  */
char s2[19];            /* of IP addresses, to be passed to inet_fmt() */
char s3[19];            /* or inet_fmts().                             */

#if !(defined(BSD) && (BSD >= 199103))
extern int              errno;
extern int              sys_nerr;
extern char *           sys_errlist[];
#endif

#define RECV_BUF_SIZE 8192
char    *send_buf, *recv_buf;
int     igmp_socket;
u_int32 allrtrs_group;
char    router_alert[4];                /* Router Alert IP Option           */
#ifndef IPOPT_RA
#define IPOPT_RA                148
#endif
#ifdef SUNOS5
char    eol[4];                         /* EOL IP Option                    */
int ip_addlen = 0;                      /* Workaround for Option bug #2     */
#endif

/*
 * max macro, with weird case to avoid conflicts
 */
#define MaX(a,b)        ((a) > (b) ? (a) : (b))

typedef int (*callback_t)(int, u_char *, int, struct igmp *, int,
                        struct sockaddr *, int *, struct timeval *);

void                    init_igmp(void);
void                    send_igmp(u_int32 src, u_int32 dst, int type,
                                                int code, u_int32 group,
                                                int datalen);
int                     inet_cksum(u_short *addr, u_int len);
void                    k_set_rcvbuf(int bufsize);
void                    k_hdr_include(int boolv);
void                    k_set_ttl(int t);
void                    k_set_loop(int l);
void                    k_set_if(u_int32 ifa);
void                    k_join(u_int32 grp, u_int32 ifa);
void                    k_leave(u_int32 grp, u_int32 ifa);
char *                  inet_fmt(u_int32 addr, char *s);
char *                  inet_fmts(u_int32 addr, u_int32 mask, char *s);
char *                  inet_name(u_int32 addr);
u_int32                 host_addr(char *name);
/* u_int is promoted u_char */
char *                  proto_type(u_int type);
char *                  flag_type(u_int type);

u_int32                 get_netmask(int s, u_int32 *dst);
int                     get_ttl(struct resp_buf *buf);
int                     t_diff(u_long a, u_long b);
u_long                  byteswap(u_long v);
int                     mtrace_callback(int, u_char *, int, struct igmp *,
                                        int, struct sockaddr *, int *,
                                        struct timeval *);
int                     send_recv(u_int32 dst, int type, int code,
                                        int tries, struct resp_buf *save,
                                        callback_t callback);
void                    passive_mode(void);
char *                  print_host(u_int32 addr);
char *                  print_host2(u_int32 addr1, u_int32 addr2);
void                    print_trace(int idx, struct resp_buf *buf,
                                        char **names);
int                     what_kind(struct resp_buf *buf, char *why);
char *                  scale(int *hop);
void                    stat_line(struct tr_resp *r, struct tr_resp *s,
                                        int have_next, int *res);
void                    fixup_stats(struct resp_buf *base,
                                        struct resp_buf *prev,
                                        struct resp_buf *new,
                                        int *bugs);
int                     check_thresh(int thresh,
                                        struct resp_buf *base,
                                        struct resp_buf *prev,
                                        struct resp_buf *new);
int                     print_stats(struct resp_buf *base,
                                        struct resp_buf *prev,
                                        struct resp_buf *new,
                                        int *bugs,
                                        char **names);
int                     path_changed(struct resp_buf *base,
                                        struct resp_buf *new);
void                    check_vif_state(void);

int                     main(int argc, char **argv);
void                    dolog(int, int, char *, ...) __printflike(3, 4);
static void             usage(void);


/*
 * Open and initialize the igmp socket, and fill in the non-changing
 * IP header fields in the output packet buffer.
 */
void
init_igmp(void)
{
    struct ip *ip;

    recv_buf = (char *)malloc(RECV_BUF_SIZE);
    if (recv_buf == NULL)
        dolog(LOG_ERR, 0, "Out of memory allocating recv_buf!");
    send_buf = (char *)malloc(RECV_BUF_SIZE);
    if (send_buf == NULL)
        dolog(LOG_ERR, 0, "Out of memory allocating send_buf!");

    if ((igmp_socket = socket(AF_INET, SOCK_RAW, IPPROTO_IGMP)) < 0) 
        dolog(LOG_ERR, errno, "IGMP socket");

    k_hdr_include(TRUE);        /* include IP header when sending */
    k_set_rcvbuf(48*1024);      /* lots of input buffering        */
    k_set_ttl(1);               /* restrict multicasts to one hop */
    k_set_loop(FALSE);          /* disable multicast loopback     */

    ip         = (struct ip *)send_buf;
    ip->ip_hl  = sizeof(struct ip) >> 2;
    ip->ip_v   = IPVERSION;
    ip->ip_tos = 0;
    ip->ip_off = 0;
    ip->ip_p   = IPPROTO_IGMP;
    ip->ip_ttl = MAXTTL;        /* applies to unicasts only */

#ifndef INADDR_ALLRTRS_GROUP
#define INADDR_ALLRTRS_GROUP    0xe0000002      /* 224.0.0.2 */
#endif
    allrtrs_group  = htonl(INADDR_ALLRTRS_GROUP);

    router_alert[0] = IPOPT_RA; /* Router Alert */
    router_alert[1] = 4;        /* 4 bytes */
    router_alert[2] = 0;
    router_alert[3] = 0;
}

#ifdef SUNOS5
void
checkforsolarisbug(void)
{
    u_int32 localhost = htonl(0x7f000001);

    eol[0] = IPOPT_EOL;
    eol[1] = IPOPT_EOL;
    eol[2] = IPOPT_EOL;
    eol[3] = IPOPT_EOL;

    setsockopt(igmp_socket, IPPROTO_IP, IP_OPTIONS, eol, sizeof(eol));
    /*
     * Check if the kernel adds the options length to the packet
     * length.  Send myself an IGMP packet of type 0 (illegal),
     * with 4 IPOPT_EOL options, my PID (for collision detection)
     * and 4 bytes of zero (so that the checksum works whether
     * the 4 bytes of zero get truncated or not).
     */
    bzero(send_buf + MIN_IP_HEADER_LEN + IGMP_MINLEN, 8);
    *(int *)(send_buf + MIN_IP_HEADER_LEN + IGMP_MINLEN) = getpid();
    send_igmp(localhost, localhost, 0, 0, 0, 8);
    while (1) {
        int recvlen, dummy = 0;

        recvlen = recvfrom(igmp_socket, recv_buf, RECV_BUF_SIZE,
                                0, NULL, &dummy);
        /* 8 == 4 bytes of options and 4 bytes of PID */
        if (recvlen >= MIN_IP_HEADER_LEN + IGMP_MINLEN + 8) {
            struct ip *ip = (struct ip *)recv_buf;
            struct igmp *igmp;
            int *p;

            if (ip->ip_hl != 6 ||
                ip->ip_p != IPPROTO_IGMP ||
                ip->ip_src.s_addr != localhost ||
                ip->ip_dst.s_addr != localhost)
                continue;

            igmp = (struct igmp *)(recv_buf + (ip->ip_hl << 2));
            if (igmp->igmp_group.s_addr != 0)
                continue;
            if (igmp->igmp_type != 0 || igmp->igmp_code != 0)
                continue;

            p = (int *)((char *)igmp + IGMP_MINLEN);
            if (*p != getpid())
                continue;

#ifdef RAW_INPUT_IS_RAW
            ip->ip_len = ntohs(ip->ip_len);
#endif
            if (ip->ip_len == IGMP_MINLEN + 4)
                ip_addlen = 4;
            else if (ip->ip_len == IGMP_MINLEN + 8)
                ip_addlen = 0;
            else
                dolog(LOG_ERR, 0, "while checking for Solaris bug: Sent %d bytes and got back %d!", IGMP_MINLEN + 8, ip->ip_len);

            break;
        }
    }
}
#endif

/*
 * Construct an IGMP message in the output packet buffer.  The caller may
 * have already placed data in that buffer, of length 'datalen'.  Then send
 * the message from the interface with IP address 'src' to destination 'dst'.
 */
void
send_igmp(u_int32 src, u_int32 dst, int type, int code, u_int32 group,
          int datalen)
{
    struct sockaddr_in sdst;
    struct ip *ip;
    struct igmp *igmp;
    int setloop = 0;
    static int raset = 0;
    int sendra = 0;
    int sendlen;

    ip                      = (struct ip *)send_buf;
    ip->ip_src.s_addr       = src;
    ip->ip_dst.s_addr       = dst;
    ip->ip_len              = MIN_IP_HEADER_LEN + IGMP_MINLEN + datalen;
    sendlen                 = ip->ip_len;
#ifdef SUNOS5
    ip->ip_len             += ip_addlen;
#endif
#ifdef RAW_OUTPUT_IS_RAW
    ip->ip_len              = htons(ip->ip_len);
#endif

    igmp                    = (struct igmp *)(send_buf + MIN_IP_HEADER_LEN);
    igmp->igmp_type         = type;
    igmp->igmp_code         = code;
    igmp->igmp_group.s_addr = group;
    igmp->igmp_cksum        = 0;
    igmp->igmp_cksum        = inet_cksum((u_short *)igmp,
                                         IGMP_MINLEN + datalen);

    if (IN_MULTICAST(ntohl(dst))) {
        k_set_if(src);
        setloop = 1;
        k_set_loop(TRUE);
        if (dst != allrtrs_group)
            sendra = 1;
    }

    if (sendopts && sendra && !raset) {
        setsockopt(igmp_socket, IPPROTO_IP, IP_OPTIONS,
                        router_alert, sizeof(router_alert));
        raset = 1;
    } else if (!sendra && raset) {
#ifdef SUNOS5
        /*
         * SunOS5 < 5.6 cannot properly reset the IP_OPTIONS "socket"
         * option.  Instead, set up a string of 4 EOL's.
         */
        setsockopt(igmp_socket, IPPROTO_IP, IP_OPTIONS,
                        eol, sizeof(eol));
#else
        setsockopt(igmp_socket, IPPROTO_IP, IP_OPTIONS,
                        NULL, 0);
#endif
        raset = 0;
    }

    bzero(&sdst, sizeof(sdst));
    sdst.sin_family = AF_INET;
#if (defined(BSD) && (BSD >= 199103))
    sdst.sin_len = sizeof(sdst);
#endif
    sdst.sin_addr.s_addr = dst;
    if (sendto(igmp_socket, send_buf, sendlen, 0,
                        (struct sockaddr *)&sdst, sizeof(sdst)) < 0) {
            dolog(LOG_WARNING, errno, "sendto to %s on %s",
                inet_fmt(dst, s1), inet_fmt(src, s2));
    }

    if (setloop)
            k_set_loop(FALSE);

    dolog(LOG_DEBUG, 0, "SENT %s from %-15s to %s",
        type == IGMP_MTRACE ? "mtrace request" : "ask_neighbors",
        src == INADDR_ANY ? "INADDR_ANY" : inet_fmt(src, s1),
        inet_fmt(dst, s2));
}

/*
 * inet_cksum extracted from:
 *                      P I N G . C
 *
 * Author -
 *      Mike Muuss
 *      U. S. Army Ballistic Research Laboratory
 *      December, 1983
 * Modified at Uc Berkeley
 *
 * (ping.c) Status -
 *      Public Domain.  Distribution Unlimited.
 *
 *                      I N _ C K S U M
 *
 * Checksum routine for Internet Protocol family headers (C Version)
 *
 */
int
inet_cksum(u_short *addr, u_int len)
{
        int nleft = (int)len;
        u_short *w = addr;
        u_short answer = 0;
        int sum = 0;

        /*
         *  Our algorithm is simple, using a 32 bit accumulator (sum),
         *  we add sequential 16 bit words to it, and at the end, fold
         *  back all the carry bits from the top 16 bits into the lower
         *  16 bits.
         */
        while (nleft > 1)  {
                sum += *w++;
                nleft -= 2;
        }

        /* mop up an odd byte, if necessary */
        if (nleft == 1) {
                *(u_char *) (&answer) = *(u_char *)w ;
                sum += answer;
        }

        /*
         * add back carry outs from top 16 bits to low 16 bits
         */
        sum = (sum >> 16) + (sum & 0xffff);     /* add hi 16 to low 16 */
        sum += (sum >> 16);                     /* add carry */
        answer = ~sum;                          /* truncate to 16 bits */
        return (answer);
}

void
k_set_rcvbuf(int bufsize)
{
    if (setsockopt(igmp_socket, SOL_SOCKET, SO_RCVBUF,
                   (char *)&bufsize, sizeof(bufsize)) < 0)
        dolog(LOG_ERR, errno, "setsockopt SO_RCVBUF %u", bufsize);
}


void
k_hdr_include(int boolv)
{
#ifdef IP_HDRINCL
    if (setsockopt(igmp_socket, IPPROTO_IP, IP_HDRINCL,
                   (char *)&boolv, sizeof(boolv)) < 0)
        dolog(LOG_ERR, errno, "setsockopt IP_HDRINCL %u", boolv);
#endif
}

void
k_set_ttl(int t)
{
    u_char ttl;

    ttl = t;
    if (setsockopt(igmp_socket, IPPROTO_IP, IP_MULTICAST_TTL,
                   (char *)&ttl, sizeof(ttl)) < 0)
        dolog(LOG_ERR, errno, "setsockopt IP_MULTICAST_TTL %u", ttl);
}


void
k_set_loop(int l)
{
    u_char loop;

    loop = l;
    if (setsockopt(igmp_socket, IPPROTO_IP, IP_MULTICAST_LOOP,
                   (char *)&loop, sizeof(loop)) < 0)
        dolog(LOG_ERR, errno, "setsockopt IP_MULTICAST_LOOP %u", loop);
}

void
k_set_if(u_int32 ifa)
{
    struct in_addr adr;

    adr.s_addr = ifa;
    if (setsockopt(igmp_socket, IPPROTO_IP, IP_MULTICAST_IF,
                   (char *)&adr, sizeof(adr)) < 0)
        dolog(LOG_ERR, errno, "setsockopt IP_MULTICAST_IF %s",
                            inet_fmt(ifa, s1));
}

void
k_join(u_int32 grp, u_int32 ifa)
{
    struct ip_mreq mreq;

    mreq.imr_multiaddr.s_addr = grp;
    mreq.imr_interface.s_addr = ifa;

    if (setsockopt(igmp_socket, IPPROTO_IP, IP_ADD_MEMBERSHIP,
                   (char *)&mreq, sizeof(mreq)) < 0)
        dolog(LOG_WARNING, errno, "can't join group %s on interface %s",
                                inet_fmt(grp, s1), inet_fmt(ifa, s2));
}


void
k_leave(u_int32 grp, u_int32 ifa)
{
    struct ip_mreq mreq;

    mreq.imr_multiaddr.s_addr = grp;
    mreq.imr_interface.s_addr = ifa;

    if (setsockopt(igmp_socket, IPPROTO_IP, IP_DROP_MEMBERSHIP,
                   (char *)&mreq, sizeof(mreq)) < 0)
        dolog(LOG_WARNING, errno, "can't leave group %s on interface %s",
                                inet_fmt(grp, s1), inet_fmt(ifa, s2));
}

/*
 * Convert an IP address in u_long (network) format into a printable string.
 */
char *
inet_fmt(u_int32 addr, char *s)
{
    u_char *a;

    a = (u_char *)&addr;
    sprintf(s, "%u.%u.%u.%u", a[0], a[1], a[2], a[3]);
    return (s);
}


/*
 * Convert an IP subnet number in u_long (network) format into a printable
 * string including the netmask as a number of bits.
 */
char *
inet_fmts(u_int32 addr, u_int32 mask, char *s)
{
    u_char *a, *m;
    int bits;

    if ((addr == 0) && (mask == 0)) {
        sprintf(s, "default");
        return (s);
    }
    a = (u_char *)&addr;
    m = (u_char *)&mask;
    bits = 33 - ffs(ntohl(mask));

    if      (m[3] != 0) sprintf(s, "%u.%u.%u.%u/%d", a[0], a[1], a[2], a[3],
                                                bits);
    else if (m[2] != 0) sprintf(s, "%u.%u.%u/%d",    a[0], a[1], a[2], bits);
    else if (m[1] != 0) sprintf(s, "%u.%u/%d",       a[0], a[1], bits);
    else                sprintf(s, "%u/%d",          a[0], bits);

    return (s);
}

char *
inet_name(u_int32 addr)
{
    struct hostent *e;

    e = gethostbyaddr(&addr, sizeof(addr), AF_INET);

    return e ? e->h_name : "?";
}


u_int32 
host_addr(char *name)
{
    struct hostent *e = NULL;
    u_int32  addr;
    int i, dots = 3;
    char        buf[40];
    char        *ip = name;
    char        *op = buf;

    /*
     * Undo BSD's favor -- take fewer than 4 octets as net/subnet address
     * if the name is all numeric.
     */
    for (i = sizeof(buf) - 7; i > 0; --i) {
        if (*ip == '.') --dots;
        else if (*ip == '\0') break;
        else if (!isdigit(*ip)) dots = 0;  /* Not numeric, don't add zeroes */
        *op++ = *ip++;
    }
    for (i = 0; i < dots; ++i) {
        *op++ = '.';
        *op++ = '0';
    }
    *op = '\0';

    if (dots <= 0)
        e = gethostbyname(name);
    if (e && (e->h_length == sizeof(addr))) {
        memcpy((char *)&addr, e->h_addr_list[0], e->h_length);
        if (e->h_addr_list[1])
            fprintf(stderr, "Warning: %s has multiple addresses, using %s\n",
                        name, inet_fmt(addr, s1));
    } else {
        addr = inet_addr(buf);
        if (addr == -1 || (IN_MULTICAST(addr) && dots)) {
            addr = 0;
            printf("Could not parse %s as host name or address\n", name);
        }
    }
    return addr;
}


char *
proto_type(u_int type)
{
    static char buf[80];

    switch (type) {
      case PROTO_DVMRP:
        return ("DVMRP");
      case PROTO_MOSPF:
        return ("MOSPF");
      case PROTO_PIM:
        return ("PIM");
      case PROTO_CBT:
        return ("CBT");
      case PROTO_PIM_SPECIAL:
        return ("PIM/Special");
      case PROTO_PIM_STATIC:
        return ("PIM/Static");
      case PROTO_DVMRP_STATIC:
        return ("DVMRP/Static");
      case PROTO_PIM_BGP4PLUS:
        return ("PIM/BGP4+");
      case PROTO_CBT_SPECIAL:
        return ("CBT/Special");
      case PROTO_CBT_STATIC:
        return ("CBT/Static");
      case PROTO_PIM_ASSERT:
        return ("PIM/Assert");
      case 0:
        return ("None");
      default:
        sprintf(buf, "Unknown protocol code %d", type);
        return (buf);
    }
}


char *
flag_type(u_int type)
{
    static char buf[80];

    switch (type) {
      case TR_NO_ERR:
        return ("");
      case TR_WRONG_IF:
        return ("Wrong interface");
      case TR_PRUNED:
        return ("Prune sent upstream");
      case TR_OPRUNED:
        return ("Output pruned");
      case TR_SCOPED:
        return ("Hit scope boundary");
      case TR_NO_RTE:
        return ("No route");
      case TR_NO_FWD:
        return ("Not forwarding");
      case TR_HIT_RP:
        return ("Reached RP/Core");
      case TR_RPF_IF:
        return ("RPF Interface");
      case TR_NO_MULTI:
        return ("Multicast disabled");
      case TR_OLD_ROUTER:
        return ("Next router no mtrace");
      case TR_NO_SPACE:
        return ("No space in packet");
      case TR_ADMIN_PROHIB:
        return ("Admin. Prohibited");
      default:
        sprintf(buf, "Unknown error code %d", type);
        return (buf);
    }
}    

/*
 * If destination is on a local net, get the netmask, else set the
 * netmask to all ones.  There are two side effects: if the local
 * address was not explicitly set, and if the destination is on a
 * local net, use that one; in either case, verify that the local
 * address is valid.
 */
u_int32
get_netmask(int s, u_int32 *dst)
{
    unsigned int n;
    struct ifconf ifc;
    struct ifreq *ifrp, *ifend;
    u_int32 if_addr, if_mask;
    u_int32 retval = 0xFFFFFFFF;
    int found = FALSE;
    int num_ifreq = 32;

    ifc.ifc_len = num_ifreq * sizeof(struct ifreq);
    ifc.ifc_buf = malloc(ifc.ifc_len);
    while (ifc.ifc_buf) {
        if (ioctl(s, SIOCGIFCONF, (char *)&ifc) < 0) {
            perror("ioctl SIOCGIFCONF");
            return retval;
        }

        /*
         * If the buffer was large enough to hold all the addresses
         * then break out, otherwise increase the buffer size and
         * try again.
         *
         * The only way to know that we definitely had enough space
         * is to know that there was enough space for at least one
         * more struct ifreq. ???
         */
        if ((num_ifreq * sizeof(struct ifreq)) >=
             ifc.ifc_len + sizeof(struct ifreq))
             break;

        num_ifreq *= 2;
        ifc.ifc_len = num_ifreq * sizeof(struct ifreq);
        ifc.ifc_buf = realloc(ifc.ifc_buf, ifc.ifc_len);
    }
    if (ifc.ifc_buf == NULL) {
        fprintf(stderr, "getting interface list: ran out of memory");
        exit(1);
    }

    ifrp = (struct ifreq *)ifc.ifc_buf;
    ifend = (struct ifreq *)(ifc.ifc_buf + ifc.ifc_len);
    /*
     * Loop through all of the interfaces.
     */
    for (; ifrp < ifend && !found; ifrp = (struct ifreq *)((char *)ifrp + n)) {
#if BSD >= 199006
        n = ifrp->ifr_addr.sa_len + sizeof(ifrp->ifr_name);
        if (n < sizeof(*ifrp))
            n = sizeof(*ifrp);
#else
        n = sizeof(*ifrp);
#endif
        /*
         * Ignore any interface for an address family other than IP.
         */
        if (ifrp->ifr_addr.sa_family != AF_INET)
            continue;

        if_addr = ((struct sockaddr_in *)&(ifrp->ifr_addr))->sin_addr.s_addr;
        if (ioctl(s, SIOCGIFFLAGS, (char *)ifrp) < 0) {
            fprintf(stderr, "SIOCGIFFLAGS on ");
            perror(ifrp->ifr_name);
            continue;
        }
        if ((ifrp->ifr_flags & (IFF_MULTICAST|IFF_UP|IFF_LOOPBACK)) !=
                                (IFF_MULTICAST|IFF_UP))
            continue;
        if (*dst == 0)
            *dst = if_addr;
        if (ioctl(s, SIOCGIFNETMASK, (char *)ifrp) >= 0) {
            if_mask = ((struct sockaddr_in *)&(ifrp->ifr_addr))->sin_addr.s_addr;
            if (if_mask != 0 && (*dst & if_mask) == (if_addr & if_mask)) {
                retval = if_mask;
                if (lcl_addr == 0) lcl_addr = if_addr;  /* XXX what about aliases? */
            }
        }
        if (lcl_addr == if_addr) found = TRUE;
    }
    if (!found && lcl_addr != 0) {
        printf("Interface address is not valid\n");
        exit(1);
    }
    return (retval);
}


/*
 * Try to pick a TTL that will get past all the thresholds in the path.
 */
int
get_ttl(struct resp_buf *buf)
{
    int rno;
    struct tr_resp *b;
    u_int ttl;

    if (buf && (rno = buf->len) > 0) {
        b = buf->resps + rno - 1;
        ttl = b->tr_fttl;

        while (--rno > 0) {
            --b;
            if (ttl < b->tr_fttl) ttl = b->tr_fttl;
            else ++ttl;
        }
        ttl += MULTICAST_TTL_INC;
        if (ttl < MULTICAST_TTL1) ttl = MULTICAST_TTL1;
        if (ttl > MULTICAST_TTL_MAX) ttl = MULTICAST_TTL_MAX;
        return (ttl);
    } else return(MULTICAST_TTL1);
}

/*
 * Calculate the difference between two 32-bit NTP timestamps and return
 * the result in milliseconds.
 */
int
t_diff(u_long a, u_long b)
{
    int d = a - b;

    return ((d * 125) >> 13);
}

/*
 * Swap bytes for poor little-endian machines that don't byte-swap
 */
u_long
byteswap(u_long v)
{
    return ((v << 24) | ((v & 0xff00) << 8) |
            ((v >> 8) & 0xff00) | (v >> 24));
}

#if 0
/*
 * XXX incomplete - need private callback data, too?
 * XXX since dst doesn't get passed through?
 */
int
neighbors_callback(int tmo, u_char *buf, int buflen, struct igmp *igmp,
                   int igmplen, struct sockaddr *addr, int *addrlen,
                   struct timeval *ts)
{
    int len;
    u_int32 dst;
    struct ip *ip = (struct ip *)buf;

    if (tmo)
        return 0;

    if (igmp->igmp_code != DVMRP_NEIGHBORS2)
        return 0;
    len = igmplen;
    /*
     * Accept DVMRP_NEIGHBORS2 response if it comes from the
     * address queried or if that address is one of the local
     * addresses in the response.
     */
    if (ip->ip_src.s_addr != dst) {
        u_int32 *p = (u_int32 *)(igmp + 1);
        u_int32 *ep = p + (len >> 2);
        while (p < ep) {
            u_int32 laddr = *p++;
            int n = ntohl(*p++) & 0xFF;
            if (laddr == dst) {
                ep = p + 1;             /* ensure p < ep after loop */
                break;
            }
            p += n;
        }
        if (p >= ep)
            return 0;
    }
    return buflen;
}
#endif

int
mtrace_callback(int tmo, u_char *buf, int buflen, struct igmp *igmp,
                int igmplen, struct sockaddr *addr, int *addrlen,
                struct timeval *ts)
{
    static u_char *savbuf = NULL;
    static int savbuflen;
    static struct sockaddr *savaddr;
    static int savaddrlen;
    static struct timeval savts;

    int len = (igmplen - QLEN) / RLEN;
    struct tr_resp *r = (struct tr_resp *)((struct tr_query *)(igmp + 1) + 1);

    if (tmo == 1) {
        /*
         * If we timed out with a packet saved, then return that packet.
         * send_recv won't send this same packet to the callback again.
         */
        if (savbuf) {
            bcopy(savbuf, buf, savbuflen);
            free(savbuf);
            savbuf = NULL;
            bcopy(savaddr, addr, savaddrlen);
            free(savaddr);
            *addrlen = savaddrlen;
            bcopy(&savts, ts, sizeof(savts));
            return savbuflen;
        }
        return 0;
    }
    if (savbuf) {
        free(savbuf);
        savbuf = NULL;
        free(savaddr);
    }
    /*
     * Check for IOS bug described in CSCdi68628, where a router that does
     *  not have multicast enabled responds to an mtrace request with a 1-hop
     *  error packet.
     * Heuristic is:
     *  If there is only one hop reported in the packet,
     *  And the protocol code is 0,
     *  And there is no previous hop,
     *  And the forwarding information is "Not Forwarding",
     *  And the router is not on the same subnet as the destination of the
     *          trace,
     *  then drop this packet.  The "#if 0"'d code saves it and returns
     *   it on timeout, but timeouts are too common (e.g. routers with
     *   limited unicast routing tables, etc).
     */
    if (len == 1 && r->tr_rproto == 0 && r->tr_rmtaddr == 0 &&
                                        r->tr_rflags == TR_NO_FWD) {
        u_int32 smask;

        VAL_TO_MASK(smask, r->tr_smask);
        if ((r->tr_outaddr & smask) != (qdst & smask)) {
#if 0
            /* XXX should do this silently? */
            fprintf(stderr, "mtrace: probably IOS-buggy packet from %s\n",
                inet_fmt(((struct sockaddr_in *)addr)->sin_addr.s_addr, s1));
            /* Save the packet to return if a timeout occurs. */
            savbuf = (u_char *)malloc(buflen);
            if (savbuf != NULL) {
                bcopy(buf, savbuf, buflen);
                savbuflen = buflen;
                savaddr = (struct sockaddr *)malloc(*addrlen);
                if (savaddr != NULL) {
                    bcopy(addr, savaddr, *addrlen);
                    savaddrlen = *addrlen;
                    bcopy(ts, &savts, sizeof(savts));
                } else {
                    free(savbuf);
                    savbuf = NULL;
                }
            }
#endif
            return 0;
        }
    }
    return buflen;
}

int
send_recv(u_int32 dst, int type, int code, int tries, struct resp_buf *save,
          callback_t callback)
{
    fd_set  fds;
    struct timeval tq, tr, tv;
    struct ip *ip;
    struct igmp *igmp;
    struct tr_query *query, *rquery;
    struct tr_resp *r;
    struct sockaddr_in recvaddr;
    u_int32 local, group;
    int ipdatalen, iphdrlen, igmpdatalen;
    int datalen;
    int count, recvlen, socklen = sizeof(recvaddr);
    int len;
    int i;

    if (type == IGMP_MTRACE) {
        group = qgrp;
        datalen = sizeof(struct tr_query);
    } else {
        group = htonl(0xff03);
        datalen = 0;
    }
    if (IN_MULTICAST(ntohl(dst))) local = lcl_addr;
    else local = INADDR_ANY;

    /*
     * If the reply address was not explictly specified, start off
     * with the standard multicast reply address, or the unicast
     * address of this host if the unicast flag was specified.
     * Then, if there is no response after trying half the tries
     * with multicast, switch to the unicast address of this host
     * if the multicast flag was not specified.  If the TTL was
     * also not specified, set a multicast TTL and increase it
     * for every try.
     */
    query = (struct tr_query *)(send_buf + MIN_IP_HEADER_LEN + IGMP_MINLEN);
    query->tr_raddr = raddr ? raddr : unicast ? lcl_addr : resp_cast;
    TR_SETTTL(query->tr_rttlqid, rttl ? rttl :
      IN_MULTICAST(ntohl(query->tr_raddr)) ? get_ttl(save) : UNICAST_TTL);
    query->tr_src   = qsrc;
    query->tr_dst   = qdst;

    for (i = tries ; i > 0; --i) {
        int oqid;

        if (tries == nqueries && raddr == 0) {
            if (i == (nqueries >> 1)) {
                if (multicast && unicast) {
                    query->tr_raddr = resp_cast;
                    if (!rttl)
                        TR_SETTTL(query->tr_rttlqid, get_ttl(save));
                } else if (!multicast) {
                    query->tr_raddr = lcl_addr;
                    TR_SETTTL(query->tr_rttlqid, UNICAST_TTL);
                }
            }
            if (i < tries && IN_MULTICAST(ntohl(query->tr_raddr)) &&
                                                                rttl == 0) {
                TR_SETTTL(query->tr_rttlqid,
                        TR_GETTTL(query->tr_rttlqid) + MULTICAST_TTL_INC);
                if (TR_GETTTL(query->tr_rttlqid) > MULTICAST_TTL_MAX)
                  TR_SETTTL(query->tr_rttlqid, MULTICAST_TTL_MAX);
            }
        }

        /*
         * Change the qid for each request sent to avoid being confused
         * by duplicate responses
         */
        oqid = TR_GETQID(query->tr_rttlqid);
        if (staticqid)
            TR_SETQID(query->tr_rttlqid, staticqid);
        else
#ifdef SYSV    
            TR_SETQID(query->tr_rttlqid, ((u_int32)lrand48() >> 8));
#else
            TR_SETQID(query->tr_rttlqid, ((u_int32)arc4random() >> 8));
#endif

        /*
         * Set timer to calculate delays, then send query
         */
        gettimeofday(&tq, 0);
        send_igmp(local, dst, type, code, group, datalen);

        /*
         * Wait for response, discarding false alarms
         */
        while (TRUE) {
            if (igmp_socket >= FD_SETSIZE)
                    dolog(LOG_ERR, 0, "descriptor too big");
            FD_ZERO(&fds);
            FD_SET(igmp_socket, &fds);
            gettimeofday(&tv, 0);
            tv.tv_sec = tq.tv_sec + timeout - tv.tv_sec;
            tv.tv_usec = tq.tv_usec - tv.tv_usec;
            if (tv.tv_usec < 0) tv.tv_usec += 1000000L, --tv.tv_sec;
            if (tv.tv_sec < 0) tv.tv_sec = tv.tv_usec = 0;

            count = select(igmp_socket + 1, &fds, NULL, NULL, &tv);

            if (count < 0) {
                if (errno != EINTR) warn("select");
                continue;
            } else if (count == 0) {
                /*
                 * Timed out.  Notify the callback.
                 */
                if (!callback || (recvlen = (callback)(1, recv_buf, 0, NULL, 0, (struct sockaddr *)&recvaddr, &socklen, &tr)) == 0) {
                    printf("* ");
                    fflush(stdout);
                    break;
                }
            } else {
                /*
                 * Data is available on the socket, so read it.
                 */
                gettimeofday(&tr, 0);
                recvlen = recvfrom(igmp_socket, recv_buf, RECV_BUF_SIZE,
                                   0, (struct sockaddr *)&recvaddr, &socklen);
            }

            if (recvlen <= 0) {
                if (recvlen && errno != EINTR) warn("recvfrom");
                continue;
            }

            if (recvlen < sizeof(struct ip)) {
                warnx("packet too short (%u bytes) for IP header", recvlen);
                continue;
            }
            ip = (struct ip *) recv_buf;
            if (ip->ip_p == 0)  /* ignore cache creation requests */
                continue;

            iphdrlen = ip->ip_hl << 2;
#ifdef RAW_INPUT_IS_RAW
            ipdatalen = ntohs(ip->ip_len);
#else
            ipdatalen = ip->ip_len;
#endif
            if (iphdrlen + ipdatalen != recvlen) {
                warnx("packet shorter (%u bytes) than hdr+data len (%u+%u)",
                        recvlen, iphdrlen, ipdatalen);
                continue;
            }

            igmp = (struct igmp *) (recv_buf + iphdrlen);
            igmpdatalen = ipdatalen - IGMP_MINLEN;
            if (igmpdatalen < 0) {
                warnx("IP data field too short (%u bytes) for IGMP from %s",
                        ipdatalen, inet_fmt(ip->ip_src.s_addr, s1));
                continue;
            }

            switch (igmp->igmp_type) {

              case IGMP_DVMRP:
                if (type != IGMP_DVMRP || code != DVMRP_ASK_NEIGHBORS2)
                        continue;
                if (igmp->igmp_code != DVMRP_NEIGHBORS2) continue;
                len = igmpdatalen;
                /*
                 * Accept DVMRP_NEIGHBORS2 response if it comes from the
                 * address queried or if that address is one of the local
                 * addresses in the response.
                 */
                if (ip->ip_src.s_addr != dst) {
                    u_int32 *p = (u_int32 *)(igmp + 1);
                    u_int32 *ep = p + (len >> 2);
                    while (p < ep) {
                        u_int32 laddr = *p++;
                        int n = ntohl(*p++) & 0xFF;
                        if (laddr == dst) {
                            ep = p + 1;         /* ensure p < ep after loop */
                            break;
                        }
                        p += n;
                    }
                    if (p >= ep) continue;
                }
                break;

              case IGMP_MTRACE:     /* For backward compatibility with 3.3 */
              case IGMP_MTRACE_RESP:
                if (type != IGMP_MTRACE) continue;
                if (igmpdatalen <= QLEN) continue;
                if ((igmpdatalen - QLEN)%RLEN) {
                    printf("packet with incomplete responses (%d bytes)\n",
                        igmpdatalen);
                    continue;
                }

                /*
                 * Ignore responses that don't match query.
                 */
                rquery = (struct tr_query *)(igmp + 1);
                if (rquery->tr_src != qsrc || rquery->tr_dst != qdst)
                    continue;
                if (TR_GETQID(rquery->tr_rttlqid) !=
                        TR_GETQID(query->tr_rttlqid)) {
                    if (verbose && TR_GETQID(rquery->tr_rttlqid) == oqid)
                        printf("[D]");
                    continue;
                }
                len = (igmpdatalen - QLEN)/RLEN;
                r = (struct tr_resp *)(rquery+1) + len - 1;

                /*
                 * Ignore trace queries passing through this node when
                 * mtrace is run on an mrouter that is in the path
                 * (needed only because IGMP_MTRACE is accepted above
                 * for backward compatibility with multicast release 3.3).
                 */
                if (igmp->igmp_type == IGMP_MTRACE) {
                    u_int32 smask;

                    VAL_TO_MASK(smask, r->tr_smask);
                    if (len < code && (r->tr_inaddr & smask) != (qsrc & smask)
                        && r->tr_rmtaddr != 0 && !(r->tr_rflags & 0x80))
                      continue;
                }
                /*
                 * Some routers will return error messages without
                 * filling in their addresses.  We fill in the address
                 * for them.
                 */
                if (r->tr_outaddr == 0)
                    r->tr_outaddr = recvaddr.sin_addr.s_addr;

                /*
                 * A match, we'll keep this one.
                 */
                if (len > code) {
                    warnx("num hops received (%d) exceeds request (%d)",
                            len, code);
                }
                rquery->tr_raddr = query->tr_raddr;     /* Insure these are */
                TR_SETTTL(rquery->tr_rttlqid, TR_GETTTL(query->tr_rttlqid));
                                                        /* as we sent them */
                break;

              default:
                continue;
            }

            /*
             * We're pretty sure we want to use this packet now,
             * but if the caller gave a callback function, it might
             * want to handle it instead.  Give the callback a chance,
             * unless the select timed out (in which case the only way
             * to get here is because the callback returned a packet).
             */
            if (callback && (count != 0) && ((callback)(0, recv_buf, recvlen, igmp, igmpdatalen, (struct sockaddr*)&recvaddr, &socklen, &tr)) == 0) {
                /*
                 * The callback function didn't like this packet.
                 * Go try receiving another one.
                 */
                continue;
            }

            /*
             * Most of the sanity checking done at this point.
             * Return this packet we have been waiting for.
             */
            if (save) {
                save->qtime = ((tq.tv_sec + JAN_1970) << 16) +
                              (tq.tv_usec << 10) / 15625;
                save->rtime = ((tr.tv_sec + JAN_1970) << 16) +
                              (tr.tv_usec << 10) / 15625;
                save->len = len;
                bcopy((char *)igmp, (char *)&save->igmp, ipdatalen);
            }
            return (recvlen);
        }
    }
    return (0);
}

/*
 * Most of this code is duplicated elsewhere.  I'm not sure if
 * the duplication is absolutely required or not.
 *
 * Ideally, this would keep track of ongoing statistics
 * collection and print out statistics.  (& keep track
 * of h-b-h traces and only print the longest)  For now,
 * it just snoops on what traces it can.
 */
void
passive_mode(void)
{
    struct timeval tr;
    time_t tr_sec;
    struct ip *ip;
    struct igmp *igmp;
    struct tr_resp *r;
    struct sockaddr_in recvaddr;
    struct tm *now;
    char timebuf[32];
    int socklen;
    int ipdatalen, iphdrlen, igmpdatalen;
    int len, recvlen;
    int qid;
    u_int32 smask;
    struct mtrace *remembered = NULL, *m, *n, **nn;
    int pc = 0;

    if (raddr) {
        if (IN_MULTICAST(ntohl(raddr))) k_join(raddr, lcl_addr);
    } else k_join(htonl(0xE0000120), lcl_addr);

    while (1) {
        fflush(stdout);         /* make sure previous trace is flushed */

        socklen = sizeof(recvaddr);
        recvlen = recvfrom(igmp_socket, recv_buf, RECV_BUF_SIZE,
                           0, (struct sockaddr *)&recvaddr, &socklen);
        gettimeofday(&tr,0);

        if (recvlen <= 0) {
            if (recvlen && errno != EINTR) warn("recvfrom");
            continue;
        }

        if (recvlen < sizeof(struct ip)) {
            warnx("packet too short (%u bytes) for IP header", recvlen);
            continue;
        }
        ip = (struct ip *) recv_buf;
        if (ip->ip_p == 0)      /* ignore cache creation requests */
            continue;

        iphdrlen = ip->ip_hl << 2;
#ifdef RAW_INPUT_IS_RAW
        ipdatalen = ntohs(ip->ip_len);
#else
        ipdatalen = ip->ip_len;
#endif
        if (iphdrlen + ipdatalen != recvlen) {
            warnx("packet shorter (%u bytes) than hdr+data len (%u+%u)",
                    recvlen, iphdrlen, ipdatalen);
            continue;
        }

        igmp = (struct igmp *) (recv_buf + iphdrlen);
        igmpdatalen = ipdatalen - IGMP_MINLEN;
        if (igmpdatalen < 0) {
            warnx("IP data field too short (%u bytes) for IGMP from %s",
                    ipdatalen, inet_fmt(ip->ip_src.s_addr, s1));
            continue;
        }

        switch (igmp->igmp_type) {

          case IGMP_MTRACE:         /* For backward compatibility with 3.3 */
          case IGMP_MTRACE_RESP:
            if (igmpdatalen < QLEN) continue;
            if ((igmpdatalen - QLEN)%RLEN) {
                printf("packet with incorrect datalen\n");
                continue;
            }

            len = (igmpdatalen - QLEN)/RLEN;

            break;

          default:
            continue;
        }

        base.qtime = ((tr.tv_sec + JAN_1970) << 16) +
                      (tr.tv_usec << 10) / 15625;
        base.rtime = ((tr.tv_sec + JAN_1970) << 16) +
                      (tr.tv_usec << 10) / 15625;
        base.len = len;
        bcopy((char *)igmp, (char *)&base.igmp, ipdatalen);
        /*
         * If the user specified which traces to monitor,
         * only accept traces that correspond to the
         * request
         */
        if ((qsrc != 0 && qsrc != base.qhdr.tr_src) ||
            (qdst != 0 && qdst != base.qhdr.tr_dst) ||
            (qgrp != 0 && qgrp != igmp->igmp_group.s_addr))
            continue;

        /* XXX This should be a hash table */
        /* XXX garbage-collection should be more efficient */
        for (nn = &remembered, n = *nn, m = NULL; n; n = *nn) {
            if ((n->base.qhdr.tr_src == base.qhdr.tr_src) &&
                (n->base.qhdr.tr_dst == base.qhdr.tr_dst) &&
                (n->base.igmp.igmp_group.s_addr == igmp->igmp_group.s_addr)) {
                m = n;
                m->last = tr;
            }
            if (tr.tv_sec - n->last.tv_sec > 500) { /* XXX don't hardcode */
                *nn = n->next;
                free(n);
            } else {
                nn = &n->next;
            }
        }

        tr_sec = tr.tv_sec;
        now = localtime(&tr_sec);
        strftime(timebuf, sizeof(timebuf) - 1, "%b %e %k:%M:%S", now);
        printf("Mtrace %s at %s",
                len == 0 ? "query" :
                           igmp->igmp_type == IGMP_MTRACE_RESP ? "response" :
                                                                 "in transit",
                timebuf);
        if (len == 0)
                printf(" by %s", inet_fmt(recvaddr.sin_addr.s_addr, s1));
        if (!IN_MULTICAST(base.qhdr.tr_raddr))
                printf(", resp to %s", (len == 0 && recvaddr.sin_addr.s_addr == base.qhdr.tr_raddr) ? "same" : inet_fmt(base.qhdr.tr_raddr, s1));
        else
                printf(", respttl %d", TR_GETTTL(base.qhdr.tr_rttlqid));
        printf(", qid %06x\n", qid = TR_GETQID(base.qhdr.tr_rttlqid));
        printf("packet from %s to %s\n",
                inet_fmt(ip->ip_src.s_addr, s1),
                inet_fmt(ip->ip_dst.s_addr, s2));

        printf("from %s to %s via group %s (mxhop=%d)\n",
                inet_fmt(base.qhdr.tr_dst, s1), inet_fmt(base.qhdr.tr_src, s2),
                inet_fmt(igmp->igmp_group.s_addr, s3), igmp->igmp_code);
        if (len == 0) {
            printf("\n");
            continue;
        }
        r = base.resps + base.len - 1;
        /*
         * Some routers will return error messages without
         * filling in their addresses.  We fill in the address
         * for them.
         */
        if (r->tr_outaddr == 0)
            r->tr_outaddr = recvaddr.sin_addr.s_addr;

        /*
         * If there was a previous trace, it see if this is a
         * statistics candidate.
         */
        if (m && base.len == m->base.len &&
                !(pc = path_changed(&m->base, &base))) {
            /*
             * Some mtrace responders send multiple copies of the same
             * reply.  Skip this packet if it's got the same query-id
             * as the last one.
             */
            if (m->lastqid == qid) {
                printf("Skipping duplicate reply\n");
                continue;
            }

            m->lastqid = qid;

            ++m->nresp;

            bcopy(&base, m->new, sizeof(base));

            printf("Results after %d seconds:\n\n",
                   (int)((m->new->qtime - m->base.qtime) >> 16));
            fixup_stats(&m->base, m->prev, m->new, m->bugs);
            print_stats(&m->base, m->prev, m->new, m->bugs, m->names);
            m->prev = m->new;
            m->new = &m->incr[(m->nresp & 1)];

            continue;
        }

        if (m == NULL) {
            m = (struct mtrace *)malloc(sizeof(struct mtrace));
            if (m == NULL) {
                fprintf(stderr, "Out of memory!\n");
                continue;
            }
            bzero(m, sizeof(struct mtrace));
            m->next = remembered;
            remembered = m;
            bcopy(&tr, &m->last, sizeof(tr));
        }

        /* Either it's a hop-by-hop in progress, or the path changed. */
        if (pc) {
            printf("[Path Changed...]\n");
            bzero(m->bugs, sizeof(m->bugs));
        }
        bcopy(&base, &m->base, sizeof(base));
        m->prev = &m->base;
        m->new = &m->incr[0];
        m->nresp = 0;

        printf("  0  ");
        print_host(base.qhdr.tr_dst);
        printf("\n");
        print_trace(1, &base, m->names);
        VAL_TO_MASK(smask, r->tr_smask);
        if ((r->tr_inaddr & smask) == (base.qhdr.tr_src & smask)) {
            printf("%3d  ", -(base.len+1));
            print_host(base.qhdr.tr_src);
            printf("\n");
        } else if (r->tr_rmtaddr != 0) {
            printf("%3d  ", -(base.len+1));
            print_host(r->tr_rmtaddr);
            printf(" %s\n", r->tr_rflags == TR_OLD_ROUTER ?
                                   "doesn't support mtrace"
                                 : "is the next hop");
        }
        printf("\n");
    }
}

char *
print_host(u_int32 addr)
{
    return print_host2(addr, 0);
}

/*
 * On some routers, one interface has a name and the other doesn't.
 * We always print the address of the outgoing interface, but can
 * sometimes get the name from the incoming interface.  This might be
 * confusing but should be slightly more helpful than just a "?".
 */
char *
print_host2(u_int32 addr1, u_int32 addr2)
{
    char *name;

    if (numeric) {
        printf("%s", inet_fmt(addr1, s1));
        return ("");
    }
    name = inet_name(addr1);
    if (*name == '?' && *(name + 1) == '\0' && addr2 != 0)
        name = inet_name(addr2);
    printf("%s (%s)", name, inet_fmt(addr1, s1));
    return (name);
}

/*
 * Print responses as received (reverse path from dst to src)
 */
void
print_trace(int idx, struct resp_buf *buf, char **names)
{
    struct tr_resp *r;
    char *name;
    int i;
    int hop;
    char *ms;

    i = abs(idx);
    r = buf->resps + i - 1;

    for (; i <= buf->len; ++i, ++r) {
        if (idx > 0) printf("%3d  ", -i);
        name = print_host2(r->tr_outaddr, r->tr_inaddr);
        if (r->tr_rflags != TR_NO_RTE)
            printf("  %s  thresh^ %d", proto_type(r->tr_rproto), r->tr_fttl);
        if (verbose) {
            hop = t_diff(ntohl(r->tr_qarr), buf->qtime);
            ms = scale(&hop);
            printf("  %d%s", hop, ms);
        }
        printf("  %s", flag_type(r->tr_rflags));
        if (i > 1 && r->tr_outaddr != (r-1)->tr_rmtaddr) {
            printf(" !RPF!");
            print_host((r-1)->tr_rmtaddr);
        }
        if (r->tr_rflags != TR_NO_RTE) {
            if (r->tr_smask <= 1)    /* MASK_TO_VAL() returns 1 for default */
                printf(" [default]");
            else if (verbose) {
                u_int32 smask;

                VAL_TO_MASK(smask, r->tr_smask);
                printf(" [%s]", inet_fmts(buf->qhdr.tr_src & smask,
                                                        smask, s1));
            }
        }
        printf("\n");
        if (names[i-1])
            free(names[i-1]);
        names[i-1]=malloc(strlen(name) + 1);
        strcpy(names[i-1], name);
    }
}

/*
 * See what kind of router is the next hop
 */
int
what_kind(struct resp_buf *buf, char *why)
{
    u_int32 smask;
    int retval;
    int hops = buf->len;
    struct tr_resp *r = buf->resps + hops - 1;
    u_int32 next = r->tr_rmtaddr;

    retval = send_recv(next, IGMP_DVMRP, DVMRP_ASK_NEIGHBORS2, 1, &incr[0], NULL);
    print_host(next);
    if (retval) {
        u_int32 version = ntohl(incr[0].igmp.igmp_group.s_addr);
        u_int32 *p = (u_int32 *)incr[0].ndata;
        u_int32 *ep = p + (incr[0].len >> 2);
        char *type = "version ";

        retval = 0;
        switch (version & 0xFF) {
          case 1:
            type = "proteon/mrouted ";
            retval = 1;
            break;

          case 10:
          case 11:
            type = "cisco ";
        }
        printf(" [%s%d.%d] %s\n",
               type, version & 0xFF, (version >> 8) & 0xFF,
               why);
        VAL_TO_MASK(smask, r->tr_smask);
        while (p < ep) {
            u_int32 laddr = *p++;
            int flags = (ntohl(*p) & 0xFF00) >> 8;
            int n = ntohl(*p++) & 0xFF;
            if (!(flags & (DVMRP_NF_DOWN | DVMRP_NF_DISABLED)) &&
                 (laddr & smask) == (qsrc & smask)) {
                printf("%3d  ", -(hops+2));
                print_host(qsrc);
                printf("\n");
                return 1;
            }
            p += n;
        }
        return retval;
    }
    printf(" %s\n", why);
    return 0;
}


char *
scale(int *hop)
{
    if (*hop > -1000 && *hop < 10000) 
            return (" ms");
    *hop /= 1000;
    if (*hop > -1000 && *hop < 10000) 
            return (" s ");
    return ("s ");
}

/*
 * Calculate and print one line of packet loss and packet rate statistics.
 * Checks for count of all ones from mrouted 2.3 that doesn't have counters.
 */
#define NEITHER 0
#define INS     1
#define OUTS    2
#define BOTH    3
void
stat_line(struct tr_resp *r, struct tr_resp *s, int have_next, int *rst)
{
    int timediff = (ntohl(s->tr_qarr) - ntohl(r->tr_qarr)) >> 16;
    int v_lost, v_pct;
    int g_lost, g_pct;
    int v_out = ntohl(s->tr_vifout) - ntohl(r->tr_vifout);
    int g_out = ntohl(s->tr_pktcnt) - ntohl(r->tr_pktcnt);
    int v_pps, g_pps;
    char v_str[8], g_str[8];
    int vhave = NEITHER;
    int ghave = NEITHER;
    int gmissing = NEITHER;
    char whochar;
    int badtime = 0;

    if (timediff == 0) {
        badtime = 1;
        /* Might be 32 bits of int seconds instead of 16int+16frac */
        timediff = ntohl(s->tr_qarr) - ntohl(r->tr_qarr);
        if (timediff == 0 || abs(timediff - statint) > statint)
            timediff = 1;
    }
    v_pps = v_out / timediff;
    g_pps = g_out / timediff;

#define STATS_MISSING(x)        ((x) == 0xFFFFFFFF)

    if (!STATS_MISSING(s->tr_vifout) && !STATS_MISSING(r->tr_vifout))
            vhave |= OUTS;
    if (STATS_MISSING(s->tr_pktcnt) || STATS_MISSING(r->tr_pktcnt))
            gmissing |= OUTS;
    if (!(*rst & BUG_NOPRINT))
            ghave |= OUTS;

    if (have_next) {
        --r,  --s,  --rst;
        if (!STATS_MISSING(s->tr_vifin) && !STATS_MISSING(r->tr_vifin))
            vhave |= INS;
        if (STATS_MISSING(s->tr_pktcnt) || STATS_MISSING(r->tr_pktcnt))
            gmissing |= INS;
        if (!(*rst & BUG_NOPRINT))
            ghave |= INS;
    }

    /*
     * Stats can be missing for any number of reasons:
     * - The hop may not be capable of collecting stats
     * - Traffic may be getting dropped at the previous hop
     *   and so this hop may not have any state
     *
     * We need a stronger heuristic to tell between these
     * two cases; in case 1 we don't want to print the stats
     * and in case 2 we want to print 100% loss.  We used to
     * err on the side of not printing, which is less useful
     * than printing 100% loss and dealing with it.
     */
#if 0
    /*
     * If both hops report as missing, then it's likely that there's just
     * no traffic flowing.
     *
     * If just one hop is missing, then we really don't have it.
     */
    if (gmissing != BOTH)
        ghave &= ~gmissing;
#endif

    whochar = have_next ? '^' : ' ';
    switch (vhave) {
      case BOTH:
        v_lost = v_out - (ntohl(s->tr_vifin) - ntohl(r->tr_vifin));
        if (v_out) v_pct = v_lost * 100 / v_out;
        else v_pct = 0;
        if (-20 < v_pct && v_pct < 101 && v_out > 10)
          sprintf(v_str, "%3d%%", v_pct);
        else if (v_pct < -900 && v_out > 10)
          sprintf(v_str, "%3dx", (int)(-v_pct / 100. + 1.));
        else if (v_pct <= -20 && v_out > 10)
          sprintf(v_str, "%1.1fx", -v_pct / 100. + 1.);
        else
          memcpy(v_str, " -- ", 5);

        if (tunstats)
            printf("%6d/%-5d=%s", v_lost, v_out, v_str);
        else
            printf("   ");
        printf("%4d pps", v_pps);
        if (v_pps && badtime)
            printf("?");

        break;

      case INS:
        v_out = ntohl(s->tr_vifin) - ntohl(r->tr_vifin);
        v_pps = v_out / timediff;
        whochar = 'v';
        /* FALLTHROUGH */

      case OUTS:
        if (tunstats)
            printf("      %c%-5d     ", whochar, v_out);
        else
            printf("  %c", whochar);
        printf("%4d pps", v_pps);
        if (v_pps && badtime)
            printf("?");

        break;

      case NEITHER:
        if (ghave != NEITHER)
            if (tunstats)
                printf("                         ");
            else
                printf("           ");

        break;
    }

    whochar = have_next ? '^' : ' ';
    switch (ghave) {
      case BOTH:
        g_lost = g_out - (ntohl(s->tr_pktcnt) - ntohl(r->tr_pktcnt));
        if (g_out) g_pct = g_lost * 100 / g_out;
        else g_pct = 0;
        if (-20 < g_pct && g_pct < 101 && g_out > 10)
          sprintf(g_str, "%3d%%", g_pct);
        else if (g_pct < -900 && g_out > 10)
          sprintf(g_str, "%3dx", (int)(-g_pct / 100. + 1.));
        else if (g_pct <= -20 && g_out > 10)
          sprintf(g_str, "%1.1fx", -g_pct / 100. + 1.);
        else
          memcpy(g_str, " -- ", 5);

        printf("%s%6d/%-5d=%s%4d pps",
               tunstats ? "" : "   ", g_lost, g_out, g_str, g_pps);
        if (g_pps && badtime)
            printf("?");
        printf("\n");
        break;

#if 0
      case INS:
        g_out = ntohl(s->tr_pktcnt) - ntohl(r->tr_pktcnt);
        g_pps = g_out / timediff;
        whochar = 'v';
        /* FALLTHROUGH */
#endif

      case OUTS:
        printf("%s     ?/%-5d     %4d pps",
               tunstats ? "" : "   ", g_out, g_pps);
        if (badtime)
            printf("?");
        printf("\n");
        break;

      case INS:
      case NEITHER:
        printf("\n");
        break;
    }


    if (debug > 2) {
        printf("\t\t\t\tv_in: %ld ", (long)ntohl(s->tr_vifin));
        printf("v_out: %ld ", (long)ntohl(s->tr_vifout));
        printf("pkts: %ld\n", (long)ntohl(s->tr_pktcnt));
        printf("\t\t\t\tv_in: %ld ", (long)ntohl(r->tr_vifin));
        printf("v_out: %ld ", (long)ntohl(r->tr_vifout));
        printf("pkts: %ld\n", (long)ntohl(r->tr_pktcnt));
        printf("\t\t\t\tv_in: %ld ",
            (long)(ntohl(s->tr_vifin) - ntohl(r->tr_vifin)));
        printf("v_out: %ld ",
            (long)(ntohl(s->tr_vifout) - ntohl(r->tr_vifout)));
        printf("pkts: %ld ", (long)(ntohl(s->tr_pktcnt) - ntohl(r->tr_pktcnt)));
        printf("time: %d\n", timediff);
        printf("\t\t\t\treset: %x hoptime: %lx\n", *rst, ntohl(s->tr_qarr));
    }
}

/*
 * A fixup to check if any pktcnt has been reset, and to fix the
 * byteorder bugs in mrouted 3.6 on little-endian machines.
 *
 * XXX Since periodic traffic sources are likely to have their
 *     pktcnt periodically reset, should we save old values when
 *     the reset occurs to keep slightly better statistics over
 *     the long term?  (e.g. SAP)
 */
void
fixup_stats(struct resp_buf *base, struct resp_buf *prev, struct resp_buf *new,
            int *bugs)
{
    int rno = base->len;
    struct tr_resp *b = base->resps + rno;
    struct tr_resp *p = prev->resps + rno;
    struct tr_resp *n = new->resps + rno;
    int *r = bugs + rno;
    int res;
    int cleanup = 0;

    /* Check for byte-swappers.  Only check on the first trace,
     * since long-running traces can wrap around and falsely trigger. */
    while (--rno >= 0) {
#ifdef TEST_ONLY
        u_int32 nvifout = ntohl(n->tr_vifout);
        u_int32 pvifout = ntohl(p->tr_vifout);
#endif
        --n; --p; --b;
#ifdef TEST_ONLY        /*XXX this is still buggy, so disable it for release */
        if ((*r & BUG_SWAP) ||
            ((base == prev) &&
             (nvifout - pvifout) > (byteswap(nvifout) - byteswap(pvifout)))) {
            if (1 || debug > 2) {
                printf("ip %s swaps; b %08x p %08x n %08x\n",
                        inet_fmt(n->tr_inaddr, s1),
                        ntohl(b->tr_vifout), pvifout, nvifout);
            }
            /* This host sends byteswapped reports; swap 'em */
            if (!(*r & BUG_SWAP)) {
                *r |= BUG_SWAP;
                b->tr_qarr = byteswap(b->tr_qarr);
                b->tr_vifin = byteswap(b->tr_vifin);
                b->tr_vifout = byteswap(b->tr_vifout);
                b->tr_pktcnt = byteswap(b->tr_pktcnt);
            }

            n->tr_qarr = byteswap(n->tr_qarr);
            n->tr_vifin = byteswap(n->tr_vifin);
            n->tr_vifout = byteswap(n->tr_vifout);
            n->tr_pktcnt = byteswap(n->tr_pktcnt);
        }
#endif
        /*
         * A missing parenthesis in mrouted 3.5-3.8's prune.c
         * causes extremely bogus time diff's.
         * One half of the time calculation was
         * inside an htonl() and one half wasn't.  Therefore, on
         * a little-endian machine, both halves of the calculation
         * would get added together in the little end.  Thus, the
         * low-order 2 bytes are either 0000 (no overflow) or
         * 0100 (overflow from the addition).
         *
         * Odds are against these particular bit patterns
         * happening in both prev and new for actual time values.
         */
        if ((*r & BUG_BOGUSTIME) || (((ntohl(n->tr_qarr) & 0xfeff) == 0x0000) &&
            ((ntohl(p->tr_qarr) & 0xfeff) == 0x0000))) {
            *r |= BUG_BOGUSTIME;
            n->tr_qarr = new->rtime;
            p->tr_qarr = prev->rtime;
            b->tr_qarr = base->rtime;
        }
    }

    rno = base->len;
    b = base->resps + rno;
    p = prev->resps + rno;
    n = new->resps + rno;
    r = bugs + rno;

    while (--rno >= 0) {
        --n; --p; --b; --r;
        /*
         * This hop has reset if:
         * - There were statistics in the base AND previous pass, AND
         *   - There are less packets this time than the first time and
         *     we didn't reset last time, OR
         *   - There are less packets this time than last time, OR
         *   - There are no statistics on this pass.
         *
         * The "and we didn't reset last time" is necessary in the
         * first branch of the OR because if the base is large and
         * we reset last time but the constant-resetter-avoidance
         * code kicked in so we delayed the copy of prev to base,
         * new could still be below base so we trigger the
         * constant-resetter code even though it was really only
         * a single reset.
         */
        res = ((b->tr_pktcnt != 0xFFFFFFFF) && (p->tr_pktcnt != 0xFFFFFFFF) &&
               ((!(*r & BUG_RESET) && ntohl(n->tr_pktcnt) < ntohl(b->tr_pktcnt)) ||
                (ntohl(n->tr_pktcnt) < ntohl(p->tr_pktcnt)) ||
                (n->tr_pktcnt == 0xFFFFFFFF)));
        if (debug > 2) {
            printf("\t\tip=%s, r=%d, res=%d\n", inet_fmt(b->tr_inaddr, s1), *r, res);
            if (res)
                printf("\t\tbase=%ld, prev=%ld, new=%ld\n", ntohl(b->tr_pktcnt),
                            ntohl(p->tr_pktcnt), ntohl(n->tr_pktcnt));
        }
        if (*r & BUG_RESET) {
            if (res || (*r & BUG_RESET2X)) {
                /*
                 * This router appears to be a 3.4 with that nasty ol'
                 * neighbor version bug, which causes it to constantly
                 * reset.  Just nuke the statistics for this node, and
                 * don't even bother giving it the benefit of the
                 * doubt from now on.
                 */
                p->tr_pktcnt = b->tr_pktcnt = n->tr_pktcnt;
                *r |= BUG_RESET2X;
            } else {
                /*
                 * This is simply the situation that the original
                 * fixup_stats was meant to deal with -- that a
                 * 3.3 or 3.4 router deleted a cache entry while
                 * traffic was still active.
                 */
                *r &= ~BUG_RESET;
                cleanup = 1;
            }
        } else
            if (res)
                *r |= BUG_RESET;
    }

    if (cleanup == 0) return;

    /*
     * If some hop reset its counters and didn't continue to
     * reset, then we pretend that the previous
     * trace was the first one.
     */
    rno = base->len;
    b = base->resps + rno;
    p = prev->resps + rno;

    while (--rno >= 0) (--b)->tr_pktcnt = (--p)->tr_pktcnt;
    base->qtime = prev->qtime;
    base->rtime = prev->rtime;
}

/*
 * Check per-source losses along path and compare with threshold.
 */
int
check_thresh(int thresh, struct resp_buf *base, struct resp_buf *prev,
             struct resp_buf *new)
{
    int rno = base->len - 1;
    struct tr_resp *b = base->resps + rno;
    struct tr_resp *p = prev->resps + rno;
    struct tr_resp *n = new->resps + rno;
    int g_out, g_lost;

    while (TRUE) {
        if ((n->tr_inaddr != b->tr_inaddr) ||
            (n->tr_outaddr != b->tr_outaddr) ||
            (n->tr_rmtaddr != b->tr_rmtaddr))
          return 1;             /* Route changed */

        if (rno-- < 1) break;
        g_out = ntohl(n->tr_pktcnt) - ntohl(p->tr_pktcnt);
        b--; n--; p--;
        g_lost = g_out - (ntohl(n->tr_pktcnt) - ntohl(p->tr_pktcnt));
        if (g_out && ((g_lost * 100 + (g_out >> 1))/ g_out) > thresh) {
            return TRUE;
        }
    }
    return FALSE;
}

/*
 * Print responses with statistics for forward path (from src to dst)
 */
int
print_stats(struct resp_buf *base, struct resp_buf *prev, struct resp_buf *new,
            int *bugs, char **names)
{
    int rtt, hop;
    char *ms;
    u_int32 smask;
    int rno = base->len - 1;
    struct tr_resp *b = base->resps + rno;
    struct tr_resp *p = prev->resps + rno;
    struct tr_resp *n = new->resps + rno;
    int *r = bugs + rno;
    u_long resptime = new->rtime;
    u_long qarrtime = ntohl(n->tr_qarr);
    u_int ttl = MaX(1, n->tr_fttl) + 1;
    int first = (base == prev);

    VAL_TO_MASK(smask, b->tr_smask);
    printf("  Source        Response Dest    ");
    if (tunstats)
        printf("Packet Statistics For     Only For Traffic\n");
    else
        printf("Overall     Packet Statistics For Traffic From\n");
    inet_fmt(base->qhdr.tr_src, s1);
    printf("%-15s %-15s  ",
           ((b->tr_inaddr & smask) == (base->qhdr.tr_src & smask)) ?
                s1 : "   * * *       ",
           inet_fmt(base->qhdr.tr_raddr, s2));
    inet_fmt(base->igmp.igmp_group.s_addr, s2);
    if (tunstats)
        printf("All Multicast Traffic     From %s\n", s1);
    else
        printf("Packet      %s To %s\n", s1, s2);
    rtt = t_diff(resptime, new->qtime);
    ms = scale(&rtt);
    printf("     %c       __/  rtt%5d%s    ",
           (first && !verbose) ? 'v' : '|', rtt, ms);
    if (tunstats)
        printf("Lost/Sent = Pct  Rate       To %s\n", s2);
    else
        printf(" Rate       Lost/Sent = Pct  Rate\n");
    if (!first || verbose) {
        hop = t_diff(resptime, qarrtime);
        ms = scale(&hop);
        printf("     v      /     hop%5d%s    ", hop, ms);
        if (tunstats)
            printf("---------------------     --------------------\n");
        else
            printf("-------     ---------------------\n");
    }
    if ((b->tr_inaddr & smask) != (base->qhdr.tr_src & smask) &&
            b->tr_rmtaddr != 0) {
        printf("%-15s %-14s is the previous hop\n", inet_fmt(b->tr_rmtaddr, s1),
                inet_name(b->tr_rmtaddr));
        printf("     v     ^\n");
    }
    if (debug > 2) {
        printf("\t\t\t\tv_in: %ld ", (long)ntohl(n->tr_vifin));
        printf("v_out: %ld ", (long)ntohl(n->tr_vifout));
        printf("pkts: %ld\n", (long)ntohl(n->tr_pktcnt));
        printf("\t\t\t\tv_in: %ld ", (long)ntohl(b->tr_vifin));
        printf("v_out: %ld ", (long)ntohl(b->tr_vifout));
        printf("pkts: %ld\n", (long)ntohl(b->tr_pktcnt));
        printf("\t\t\t\tv_in: %ld ",
            (long)(ntohl(n->tr_vifin) - ntohl(b->tr_vifin)));
        printf("v_out: %ld ",
            (long)(ntohl(n->tr_vifout) - ntohl(b->tr_vifout)));
        printf("pkts: %ld\n",
            (long)(ntohl(n->tr_pktcnt) - ntohl(b->tr_pktcnt)));
        printf("\t\t\t\treset: %x hoptime: %lx\n", *r, (long)ntohl(n->tr_qarr));
    }

    while (TRUE) {
        if ((n->tr_inaddr != b->tr_inaddr) ||
            (n->tr_outaddr != b->tr_outaddr) ||
            (n->tr_rmtaddr != b->tr_rmtaddr))
          return 1;             /* Route changed */

        if ((n->tr_inaddr != n->tr_outaddr) && n->tr_inaddr)
          printf("%-15s\n", inet_fmt(n->tr_inaddr, s1));
        printf("%-15s %-14s %s%s\n", inet_fmt(n->tr_outaddr, s1), names[rno],
                 flag_type(n->tr_rflags),
                 (*r & BUG_NOPRINT) ? " [reset counters]" : "");

        if (rno-- < 1) break;

        printf("     %c     ^      ttl%5d   ", (first && !verbose) ? 'v' : '|',
                                                                ttl);
        stat_line(p, n, TRUE, r);
        if (!first || verbose) {
            resptime = qarrtime;
            qarrtime = ntohl((n-1)->tr_qarr);
            hop = t_diff(resptime, qarrtime);
            ms = scale(&hop);
            printf("     v     |      hop%5d%s", hop, ms);
            if (first)
                printf("\n");
            else
                stat_line(b, n, TRUE, r);
        }

        --b, --p, --n, --r;
        ttl = MaX(ttl, MaX(1, n->tr_fttl) + base->len - rno);
    }
           
    printf("     %c      \\__   ttl%5d   ", (first && !verbose) ? 'v' : '|',
                                                        ttl);
    stat_line(p, n, FALSE, r);
    if (!first || verbose) {
        hop = t_diff(qarrtime, new->qtime);
        ms = scale(&hop);
        printf("     v         \\  hop%5d%s", hop, ms);
        if (first)
            printf("\n");
        else
            stat_line(b, n, FALSE, r);
    }
    printf("%-15s %s\n", inet_fmt(base->qhdr.tr_dst, s1),
                        !passive ? inet_fmt(lcl_addr, s2) : "   * * *       ");
    printf("  Receiver      Query Source\n\n");
    return 0;
}

/*
 * Determine whether or not the path has changed.
 */
int
path_changed(struct resp_buf *base, struct resp_buf *new)
{
    int rno = base->len - 1;
    struct tr_resp *b = base->resps + rno;
    struct tr_resp *n = new->resps + rno;

    while (rno-- >= 0) {
        if ((n->tr_inaddr != b->tr_inaddr) ||
            (n->tr_outaddr != b->tr_outaddr) ||
            (n->tr_rmtaddr != b->tr_rmtaddr))
          return 1;             /* Route changed */
        if ((b->tr_rflags == TR_NO_RTE) &&
            (n->tr_rflags != TR_NO_RTE))
          return 1;             /* Route got longer? */
        --n;
        --b;
    }
    return 0;
}


/***************************************************************************
 *      main
 ***************************************************************************/

int
main(int argc, char **argv)
{
    int udp;
    struct sockaddr_in addr;
    int addrlen = sizeof(addr);
    int recvlen;
    struct timeval tv;
    struct resp_buf *prev, *new;
    struct tr_resp *r;
    u_int32 smask;
    int rno;
    int hops, nexthop, tries;
    u_int32 lastout = 0;
    int numstats = 1;
    int waittime;
    int seed;
    int hopbyhop;
    int i;
    int printed = 1;

    if (geteuid() != 0)
        errx(1, "must be root");

    /*
     * We might get spawned by vat with the audio device open.
     * Close everything but stdin, stdout, stderr.
     */
    for (i = 3; i < 255; i++)
        close(i);

    init_igmp();
    setuid(getuid());

    argv++, argc--;
    if (argc == 0) usage();

    while (argc > 0 && *argv[0] == '-') {
        char *p = *argv++;  argc--;
        p++;
        do {
            char c = *p++;
            char *arg = NULL;
            if (isdigit(*p)) {
                arg = p;
                p = "";
            } else if (argc > 0) arg = argv[0];
            switch (c) {
              case 'd':                 /* Unlisted debug print option */
                if (arg && isdigit(*arg)) {
                    debug = atoi(arg);
                    if (debug < 0) debug = 0;
                    if (debug > 3) debug = 3;
                    if (arg == argv[0]) argv++, argc--;
                    break;
                } else
                    usage();
              case 'M':                 /* Use multicast for reponse */
                multicast = TRUE;
                break;
              case 'U':                 /* Use unicast for response */
                unicast = TRUE;
                break;
              case 'L':                 /* Trace w/ loss threshold */
                if (arg && isdigit(*arg)) {
                    lossthresh = atoi(arg);
                    if (lossthresh < 0)
                        lossthresh = 0;
                    numstats = 3153600;
                    if (arg == argv[0]) argv++, argc--;
                    break;
                } else
                    usage();
                break;
              case 'O':                 /* Don't use IP options */
                sendopts = FALSE;
                break;
              case 'P':                 /* Just watch the path */
                printstats = FALSE;
                numstats = 3153600;
                break;
              case 'Q':                 /* (undoc.) always use this QID */
                if (arg && isdigit(*arg)) {
                    staticqid = atoi(arg);
                    if (staticqid < 0)
                        staticqid = 0;
                    if (arg == argv[0]) argv++, argc--;
                    break;
                } else
                    usage();
                break;
              case 'T':                 /* Print confusing tunnel stats */
                tunstats = TRUE;
                break;
              case 'W':                 /* Cisco's "weak" mtrace */
                weak = TRUE;
                break;
              case 'V':                 /* Print version and exit */
                fprintf(stderr, "mtrace version 5.2\n");
                exit(1);
                break;
              case 'l':                 /* Loop updating stats indefinitely */
                numstats = 3153600;
                break;
              case 'n':                 /* Don't reverse map host addresses */
                numeric = TRUE;
                break;
              case 'p':                 /* Passive listen for traces */
                passive = TRUE;
                break;
              case 'v':                 /* Verbosity */
                verbose = TRUE;
                break;
              case 's':                 /* Short form, don't wait for stats */
                numstats = 0;
                break;
              case 'w':                 /* Time to wait for packet arrival */
                if (arg && isdigit(*arg)) {
                    timeout = atoi(arg);
                    if (timeout < 1) timeout = 1;
                    if (arg == argv[0]) argv++, argc--;
                    break;
                } else
                    usage();
              case 'f':                 /* first hop */
                if (arg && isdigit(*arg)) {
                    qno = atoi(arg);
                    if (qno > MAXHOPS) qno = MAXHOPS;
                    else if (qno < 1) qno = 0;
                    if (arg == argv[0]) argv++, argc--;
                    fflag++;
                    break;
                } else
                    usage();
              case 'm':                 /* Max number of hops to trace */
                if (arg && isdigit(*arg)) {
                    qno = atoi(arg);
                    if (qno > MAXHOPS) qno = MAXHOPS;
                    else if (qno < 1) qno = 0;
                    if (arg == argv[0]) argv++, argc--;
                    break;
                } else
                    usage();
              case 'q':                 /* Number of query retries */
                if (arg && isdigit(*arg)) {
                    nqueries = atoi(arg);
                    if (nqueries < 1) nqueries = 1;
                    if (arg == argv[0]) argv++, argc--;
                    break;
                } else
                    usage();
              case 'g':                 /* Last-hop gateway (dest of query) */
                if (arg && (gwy = host_addr(arg))) {
                    if (arg == argv[0]) argv++, argc--;
                    break;
                } else
                    usage();
              case 't':                 /* TTL for query packet */
                if (arg && isdigit(*arg)) {
                    qttl = atoi(arg);
                    if (qttl < 1) qttl = 1;
                    rttl = qttl;
                    if (arg == argv[0]) argv++, argc--;
                    break;
                } else
                    usage();
              case 'e':                 /* Extra hops past non-responder */
                if (arg && isdigit(*arg)) {
                    extrahops = atoi(arg);
                    if (extrahops < 0) extrahops = 0;
                    if (arg == argv[0]) argv++, argc--;
                    break;
                } else
                    usage();
              case 'r':                 /* Dest for response packet */
                if (arg && (raddr = host_addr(arg))) {
                    if (arg == argv[0]) argv++, argc--;
                    break;
                } else
                    usage();
              case 'i':                 /* Local interface address */
                if (arg && (lcl_addr = host_addr(arg))) {
                    if (arg == argv[0]) argv++, argc--;
                    break;
                } else
                    usage();
              case 'S':                 /* Stat accumulation interval */
                if (arg && isdigit(*arg)) {
                    statint = atoi(arg);
                    if (statint < 1) statint = 1;
                    if (arg == argv[0]) argv++, argc--;
                    break;
                } else
                    usage();
              default:
                usage();
            }
        } while (*p);
    }

    if (argc > 0 && (qsrc = host_addr(argv[0]))) {          /* Source of path */
        if (IN_MULTICAST(ntohl(qsrc))) {
            if (gwy) {
                /* Should probably rewrite arg parsing at some point, as
                 * this makes "mtrace -g foo 224.1.2.3 224.2.3.4" valid!... */
                qgrp = qsrc;
                qsrc = 0;
            } else {
                usage();
            }
        }
        argv++, argc--;
        if (argc > 0 && (qdst = host_addr(argv[0]))) {      /* Dest of path */
            argv++, argc--;
            if (argc > 0 && (qgrp = host_addr(argv[0]))) {  /* Path via group */
                argv++, argc--;
            }
            if (IN_MULTICAST(ntohl(qdst))) {
                u_int32 temp = qdst;
                qdst = qgrp;
                qgrp = temp;
                if (IN_MULTICAST(ntohl(qdst))) usage();
            } else if (qgrp && !IN_MULTICAST(ntohl(qgrp))) usage();
        }
    }

    if (passive) {
        passive_mode();
        return(0);
    }

    if (argc > 0) {
        usage();
    }

#ifdef SUNOS5
    if (sendopts)
        checkforsolarisbug();
#endif

    /*
     * Set useful defaults for as many parameters as possible.
     */

    defgrp = 0;                         /* Default to no group */
    query_cast = htonl(0xE0000002);     /* All routers multicast addr */
    resp_cast = htonl(0xE0000120);      /* Mtrace response multicast addr */
    if (qgrp == 0) {
        if (!weak)
            qgrp = defgrp;
        if (printstats && numstats != 0 && !tunstats) {
            /* Stats are useless without a group */
            warnx(
        "WARNING: no multicast group specified, so no statistics printed");
            numstats = 0;
        }
    } else {
        if (weak)
            warnx(
        "WARNING: group was specified so not performing \"weak\" mtrace");
    }

    /*
     * Get default local address for multicasts to use in setting defaults.
     */
    addr.sin_family = AF_INET;
#if (defined(BSD) && (BSD >= 199103))
    addr.sin_len = sizeof(addr);
#endif
    addr.sin_addr.s_addr = qgrp ? qgrp : query_cast;
    addr.sin_port = htons(2000);        /* Any port above 1024 will do */

    /*
     * Note that getsockname() can return 0 on some systems
     * (notably SunOS 5.x, x < 6).  This is taken care of in
     * get_netmask().  If the default multicast interface (set
     * with the route for 224.0.0.0) is not the same as the
     * hostname, mtrace -i [if_addr] will have to be used.
     */
    if (((udp = socket(AF_INET, SOCK_DGRAM, 0)) < 0) ||
        (connect(udp, (struct sockaddr *) &addr, sizeof(addr)) < 0) ||
        getsockname(udp, (struct sockaddr *) &addr, &addrlen) < 0)
        err(-1, "determining local address");

#ifdef SUNOS5
    /*
     * SunOS 5.X prior to SunOS 2.6, getsockname returns 0 for udp socket.
     * This call to sysinfo will return the hostname.
     * If the default multicast interfface (set with the route
     * for 224.0.0.0) is not the same as the hostname,
     * mtrace -i [if_addr] will have to be used.
     */
    if (addr.sin_addr.s_addr == 0) {
        char myhostname[MAXHOSTNAMELEN];
        struct hostent *hp;
        int error;
    
        error = sysinfo(SI_HOSTNAME, myhostname, sizeof(myhostname));
        if (error == -1)
            err(1, "getting my hostname");

        hp = gethostbyname(myhostname);
        if (hp == NULL || hp->h_addrtype != AF_INET ||
            hp->h_length != sizeof(addr.sin_addr))
            err(1, "finding IP address for my hostname");

        memcpy((char *)&addr.sin_addr.s_addr, hp->h_addr, hp->h_length);
    }
#endif

    /*
     * Default destination for path to be queried is the local host.
     * When gateway specified, default destination is that gateway
     *  and default source is local host.
     */
    if (qdst == 0) {
        qdst = lcl_addr ? lcl_addr : addr.sin_addr.s_addr;
        dst_netmask = get_netmask(udp, &qdst);
        if (gwy && (gwy & dst_netmask) != (qdst & dst_netmask) &&
                !IN_MULTICAST(ntohl(gwy)))
            qdst = gwy;
    }
    if (qsrc == 0 && gwy)
        qsrc = lcl_addr ? lcl_addr : addr.sin_addr.s_addr;
    if (qsrc == 0)
        usage();
    if (!dst_netmask)
        dst_netmask = get_netmask(udp, &qdst);
    close(udp);
    if (lcl_addr == 0) lcl_addr = addr.sin_addr.s_addr;

    /*
     * Initialize the seed for random query identifiers.
     */
    gettimeofday(&tv, 0);
    seed = tv.tv_usec ^ lcl_addr;
#ifdef SYSV    
    srand48(seed);
#endif

    /*
     * Protect against unicast queries to mrouted versions that might crash.
     * Also use the obsolete "can mtrace" neighbor bit to warn about
     * older implementations.
     */
    if (gwy && !IN_MULTICAST(ntohl(gwy)))
      if (send_recv(gwy, IGMP_DVMRP, DVMRP_ASK_NEIGHBORS2, 1, &incr[0], NULL)) {
        int flags = ntohl(incr[0].igmp.igmp_group.s_addr);
        int version = flags & 0xFFFF;
        int info = (flags & 0xFF0000) >> 16;

        if (version == 0x0303 || version == 0x0503) {
            printf("Don't use -g to address an mrouted 3.%d, it might crash\n",
                   (version >> 8) & 0xFF);
            exit(0);
        }
        if ((info & 0x08) == 0) {
            printf("mtrace: ");
            print_host(gwy);
            printf(" probably doesn't support mtrace, trying anyway...\n");
        }
      }

    printf("Mtrace from %s to %s via group %s\n",
           inet_fmt(qsrc, s1), inet_fmt(qdst, s2), inet_fmt(qgrp, s3));

    if ((qdst & dst_netmask) == (qsrc & dst_netmask))
        fprintf(stderr, "mtrace: Source & receiver appear to be directly connected\n");

    /*
     * If the response is to be a multicast address, make sure we 
     * are listening on that multicast address.
     */
    if (raddr) {
        if (IN_MULTICAST(ntohl(raddr))) k_join(raddr, lcl_addr);
    } else k_join(resp_cast, lcl_addr);

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

    /*
     * If the destination is on the local net, the last-hop router can
     * be found by multicast to the all-routers multicast group.
     * Otherwise, use the group address that is the subject of the
     * query since by definition the last-hop router will be a member.
     * Set default TTLs for local remote multicasts.
     */
    if (gwy == 0)
      if ((qdst & dst_netmask) == (lcl_addr & dst_netmask)) tdst = query_cast;
      else tdst = qgrp;
    else tdst = gwy;
    if (tdst == 0 && qgrp == 0)
        errx(1, "mtrace: weak mtrace requires -g if destination is not local.\n");

    if (IN_MULTICAST(ntohl(tdst))) {
      k_set_loop(1);    /* If I am running on a router, I need to hear this */
      if (tdst == query_cast) k_set_ttl(qttl ? qttl : 1);
      else k_set_ttl(qttl ? qttl : MULTICAST_TTL1);
    }

    /*
     * Try a query at the requested number of hops or MAXHOPS if unspecified.
     */
    if (qno == 0) {
        hops = MAXHOPS;
        tries = 1;
        printf("Querying full reverse path... ");
        fflush(stdout);
    } else {
        hops = qno;
        tries = nqueries;
        if (fflag)
            printf("Querying full reverse path, starting at hop %d...", qno);
        else
            printf("Querying reverse path, maximum %d hops... ", qno);
        fflush(stdout); 
    }
    base.rtime = 0;
    base.len = 0;
    hopbyhop = FALSE;

    recvlen = send_recv(tdst, IGMP_MTRACE, hops, tries, &base, mtrace_callback);

    /*
     * If the initial query was successful, print it.  Otherwise, if
     * the query max hop count is the default of zero, loop starting
     * from one until there is no response for extrahops more hops.  The
     * extra hops allow getting past an mtrace-capable mrouter that can't
     * send multicast packets because all phyints are disabled.
     */
    if (recvlen) {
        printf("\n  0  ");
        print_host(qdst);
        printf("\n");
        print_trace(1, &base, names);
        r = base.resps + base.len - 1;
        if (r->tr_rflags == TR_OLD_ROUTER || r->tr_rflags == TR_NO_SPACE ||
                (qno != 0 && r->tr_rmtaddr != 0 && !fflag)) {
            printf("%3d  ", -(base.len+1));
            what_kind(&base, r->tr_rflags == TR_OLD_ROUTER ?
                                   "doesn't support mtrace"
                                 : "is the next hop");
        } else {
            if (fflag) {
                nexthop = hops = qno;
                goto continuehop;
            }
            VAL_TO_MASK(smask, r->tr_smask);
            if ((r->tr_inaddr & smask) == (qsrc & smask)) {
                printf("%3d  ", -(base.len+1));
                print_host(qsrc);
                printf("\n");
            }
        }
    } else if (qno == 0) {
        hopbyhop = TRUE;
        printf("switching to hop-by-hop:\n  0  ");
        print_host(qdst);
        printf("\n");

        for (hops = 1, nexthop = 1; hops <= MAXHOPS; ++hops) {
            printf("%3d  ", -hops);
            fflush(stdout);

            /*
             * After a successful first hop, try switching to the unicast
             * address of the last-hop router instead of multicasting the
             * trace query.  This should be safe for mrouted versions 3.3
             * and 3.5 because there is a long route timeout with metric
             * infinity before a route disappears.  Switching to unicast
             * reduces the amount of multicast traffic and avoids a bug
             * with duplicate suppression in mrouted 3.5.
             */
            if (hops == 2 && gwy == 0 && lastout != 0 &&
                (recvlen = send_recv(lastout, IGMP_MTRACE, hops, 1, &base, mtrace_callback)))
              tdst = lastout;
            else recvlen = send_recv(tdst, IGMP_MTRACE, hops, nqueries, &base, mtrace_callback);

            if (recvlen == 0) {
                /*if (hops == 1) break;*/
                if (hops == nexthop) {
                    if (hops == 1) {
                        printf("\n");
                    } else if (what_kind(&base, "didn't respond")) {
                        /* the ask_neighbors determined that the
                         * not-responding router is the first-hop. */
                        break;
                    }
                    if (extrahops == 0)
                        break;
                } else if (hops < nexthop + extrahops) {
                    printf("\n");
                } else {
                    printf("...giving up\n");
                    break;
                }
                continue;
            }
            if (base.len == hops &&
                (hops == 1 || (base.resps+nexthop-2)->tr_outaddr == lastout)) {
                if (hops == nexthop) {
                    print_trace(-hops, &base, names);
                } else {
                    printf("\nResuming...\n");
                    print_trace(nexthop, &base, names);
                }
            } else {
                if (base.len < hops) {
                    /*
                     * A shorter trace than requested means a fatal error
                     * occurred along the path, or that the route changed
                     * to a shorter one.
                     *
                     * If the trace is longer than the last one we received,
                     * then we are resuming from a skipped router (but there
                     * is still probably a problem).
                     *
                     * If the trace is shorter than the last one we
                     * received, then the route must have changed (and
                     * there is still probably a problem).
                     */
                    if (nexthop <= base.len) {
                        printf("\nResuming...\n");
                        print_trace(nexthop, &base, names);
                    } else if (nexthop > base.len + 1) {
                        hops = base.len;
                        printf("\nRoute must have changed...\n");
                        print_trace(1, &base, names);
                    }
                } else {
                    /*
                     * The last hop address is not the same as it was.
                     * If we didn't know the last hop then we just
                     * got the first response from a hop-by-hop trace;
                     * if we did know the last hop then
                     * the route probably changed underneath us.
                     */
                    hops = base.len;
                    if (lastout != 0)
                        printf("\nRoute must have changed...\n");
                    else
                        printf("\nResuming...\n");
                    print_trace(1, &base, names);
                }
            }
continuehop:
            r = base.resps + base.len - 1;
            lastout = r->tr_outaddr;

            if (base.len < hops ||
                r->tr_rmtaddr == 0 ||
                (r->tr_rflags & 0x80)) {
                VAL_TO_MASK(smask, r->tr_smask);
                if (r->tr_rmtaddr) {
                    if (hops != nexthop) {
                        printf("\n%3d  ", -(base.len+1));
                    }
                    what_kind(&base, r->tr_rflags == TR_OLD_ROUTER ?
                                "doesn't support mtrace" :
                                "would be the next hop");
                    /* XXX could do segmented trace if TR_NO_SPACE */
                } else if (r->tr_rflags == TR_NO_ERR &&
                           (r->tr_inaddr & smask) == (qsrc & smask)) {
                    printf("%3d  ", -(hops + 1));
                    print_host(qsrc);
                    printf("\n");
                }
                break;
            }

            nexthop = hops + 1;
        }
    }

    if (base.rtime == 0) {
        printf("Timed out receiving responses\n");
        if (IN_MULTICAST(ntohl(tdst)))
          if (tdst == query_cast)
            printf("Perhaps no local router has a route for source %s\n",
                   inet_fmt(qsrc, s1));
          else
            printf("Perhaps receiver %s is not a member of group %s,\n\
or no router local to it has a route for source %s,\n\
or multicast at ttl %d doesn't reach its last-hop router for that source\n",
                   inet_fmt(qdst, s2), inet_fmt(qgrp, s3), inet_fmt(qsrc, s1),
                   qttl ? qttl : MULTICAST_TTL1);
        exit(1);
    }

    printf("Round trip time %d ms; ", t_diff(base.rtime, base.qtime));
    {
        struct tr_resp *n = base.resps + base.len - 1;
        u_int ttl = n->tr_fttl + 1;

        rno = base.len - 1;
        while (--rno > 0) {
            --n;
            ttl = MaX(ttl, MaX(1, n->tr_fttl) + base.len - rno);
        }
        printf("total ttl of %d required.\n\n",ttl);
    }

    /*
     * Use the saved response which was the longest one received,
     * and make additional probes after delay to measure loss.
     */
    raddr = base.qhdr.tr_raddr;
    rttl = TR_GETTTL(base.qhdr.tr_rttlqid);
    gettimeofday(&tv, 0);
    waittime = statint - (((tv.tv_sec + JAN_1970) & 0xFFFF) - (base.qtime >> 16));
    prev = &base;
    new = &incr[numstats&1];

    /*
     * Zero out bug-avoidance counters
     */
    memset(bugs, 0, sizeof(bugs));

    if (!printstats)
        printf("Monitoring path..");

    while (numstats--) {
        if (waittime < 1) printf("\n");
        else {
            if (printstats && (lossthresh == 0 || printed)) {
                printf("Waiting to accumulate statistics...");
            } else {
                printf(".");
            }
            fflush(stdout);
            sleep((unsigned)waittime);
        }
        printed = 0;
        rno = hopbyhop ? base.len : qno ? qno : MAXHOPS;
        recvlen = send_recv(tdst, IGMP_MTRACE, rno, nqueries, new, mtrace_callback);

        if (recvlen == 0) {
            printf("Timed out.\n");
            if (numstats) {
                numstats++;
                continue;
            } else
                exit(1);
        }

        if (base.len != new->len || path_changed(&base, new)) {
            printf("%s", base.len == new->len ? "Route changed" :
                                        "Trace length doesn't match");
            if (!printstats)
                printf(" after %d seconds",
                   (int)((new->qtime - base.qtime) >> 16));
            printf(":\n");
printandcontinue:
            print_trace(1, new, names);
            numstats++;
            bcopy(new, &base, sizeof(base));
            nexthop = hops = new->len;
            printf("Continuing with hop-by-hop...\n");
            goto continuehop;
        }

        if (printstats) {
            if (new->igmp.igmp_group.s_addr != qgrp ||
                new->qhdr.tr_src != qsrc || new->qhdr.tr_dst != qdst)
                printf("\nWARNING: trace modified en route; statistics may be incorrect\n");
            fixup_stats(&base, prev, new, bugs);
            if ((lossthresh == 0) || check_thresh(lossthresh, &base, prev, new)) {
                printf("Results after %d seconds",
                       (int)((new->qtime - base.qtime) >> 16));
                if (lossthresh)
                    printf(" (this trace %d seconds)",
                           (int)((new->qtime - prev->qtime) >> 16));
                if (verbose) {
                    time_t t = time(0);
                    struct tm *qr = localtime(&t);

                    printf(" qid 0x%06x at %2d:%02d:%02d",
                                TR_GETQID(base.qhdr.tr_rttlqid),
                                qr->tm_hour, qr->tm_min, qr->tm_sec);
                }
                printf(":\n\n");
                printed = 1;
                if (print_stats(&base, prev, new, bugs, names)) {
                    printf("This should have been detected earlier, but ");
                    printf("Route changed:\n");
                    goto printandcontinue;
                }
            }
        }
        prev = new;
        new = &incr[numstats&1];
        waittime = statint;
    }

    /*
     * If the response was multicast back, leave the group
     */
    if (raddr) {
        if (IN_MULTICAST(ntohl(raddr))) k_leave(raddr, lcl_addr);
    } else k_leave(resp_cast, lcl_addr);

    return (0);
}

static void
usage(void)
{
        fprintf(stderr, "%s\n%s\n%s\n",
        "usage: mtrace [-MUOPTWVlnpvs] [-e extra_hops] [-f first_hop] [-i if_addr]",
        "              [-g gateway] [-m max_hops] [-q nqueries] [-r resp_dest]",
        "              [-S statint] [-t ttl] [-w wait] source [receiver] [group]");
        exit(1);
}

void
check_vif_state(void)
{
    dolog(LOG_WARNING, errno, "sendto");
}

/*
 * Log errors and other messages to stderr, according to the severity
 * of the message and the current debug level.  For errors of severity
 * LOG_ERR or worse, terminate the program.
 */
void
dolog(int severity, int syserr, char *format, ...)
{
        va_list ap;
        char    fmt[100];

        va_start(ap, format);

    switch (debug) {
        case 0: if (severity > LOG_WARNING) return;
        case 1: if (severity > LOG_NOTICE) return;
        case 2: if (severity > LOG_INFO  ) return;
        default:
            fmt[0] = '\0';
            if (severity == LOG_WARNING) 
                strcpy(fmt, "warning - ");
            strncat(fmt, format, sizeof(fmt)-strlen(fmt));
            fmt[sizeof(fmt)-1]='\0';
            vfprintf(stderr, fmt, ap);
            if (syserr == 0)
                fprintf(stderr, "\n");
            else if (syserr < sys_nerr)
                fprintf(stderr, ": %s\n", sys_errlist[syserr]);
            else
                fprintf(stderr, ": errno %d\n", syserr);
    }
    if (severity <= LOG_ERR) exit(1);
}