/*
 *  IPv4 packet sniffer for Linux 2.x
 *
 *  Copyright (C) 2002  Christophe Devine
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <netpacket/packet.h>
#include <netinet/ip_icmp.h>
#include <netinet/udp.h>
#include <netinet/tcp.h>
#include <netinet/ip.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <string.h>
#include <stdio.h>
#include <time.h>

#define ETH_P_ALL 0x0003
#define ETH_P_IP  0x0800

int main( int argc, char *argv[] )
{
    unsigned char buffer[4096];
    unsigned short sport, dport;
    int raw_sock, buflen, fromlen;
    struct sockaddr_ll sll, from;
    struct packet_mreq mr;
    struct ifreq ifr;

    struct in_addr src, dst;
    struct icmphdr *icmp;
    struct udphdr  *udp;
    struct tcphdr  *tcp;
    struct iphdr   *ip;
    struct tm *lt;
    time_t tt;

    /* check the argument */

    if( argc != 2 )
    {
        printf( "usage: %s <interface>\n", argv[0] );
        return( 1 );
    }

    /* create the raw socket */

    if( ( raw_sock = socket( PF_PACKET, SOCK_DGRAM,
                             htons( ETH_P_ALL ) ) ) == -1 )
    {
        perror( "socket" );
        return( 1 );
    }

    /* find the interface index */

    memset( &ifr, 0, sizeof( ifr ) );
    strncpy( ifr.ifr_name, argv[1], sizeof( ifr.ifr_name ) );

    if( ioctl( raw_sock, SIOCGIFINDEX, &ifr ) == -1 )
    {
        perror( "ioctl(SIOCGIFINDEX)" );
        return( 1 );
    }

    /* this raw socket will receive all ethernet packets */

    memset( &sll, 0, sizeof( sll ) );
    sll.sll_family   = AF_PACKET;
    sll.sll_ifindex  = ifr.ifr_ifindex;
    sll.sll_protocol = htons( ETH_P_ALL );

    /* bind the raw socket to the interface */

    if( bind( raw_sock, (struct sockaddr *) &sll, sizeof( sll ) ) == -1 )
    {
        perror( "bind" );
        return( 1 );
    }

    /* enable promiscuous mode */

    memset( &mr, 0, sizeof( mr ) );
    mr.mr_ifindex = ifr.ifr_ifindex;
    mr.mr_type    = PACKET_MR_PROMISC;

    if( setsockopt( raw_sock, SOL_PACKET, PACKET_ADD_MEMBERSHIP,
                    &mr, sizeof( mr ) ) == -1 )
    {
        perror( "setsockopt" );
        return( 1 );
    }

    while( 1 )
    {
        /* wait for packets */

        fromlen = sizeof( from );
        if( ( buflen = recvfrom( raw_sock, buffer, 4096, 0,
            (struct sockaddr *) &from, &fromlen ) ) == -1 )
        {
            perror( "recvfrom" );
            return( 1 );
        }

        /* skip duplicate packets on the loopback interface */

        if( ! strcmp( argv[1], "lo" ) && from.sll_pkttype == PACKET_OUTGOING )
        {
            continue;
        }

        /* verify the socket family */

        if( from.sll_family != AF_PACKET )
        {
            printf( "socket family is %d, should be %d (AF_PACKET)\n",
                    from.sll_protocol, AF_PACKET );
            continue;
        }

        /* we're only interested in standard IPv4 packets */

        if( ntohs( from.sll_protocol ) != ETH_P_IP )
        {
            continue;
        }

        /* have a look inside the IP header */

        ip = (struct iphdr *) buffer;

        src.s_addr = ip->saddr;
        dst.s_addr = ip->daddr;

        /* print the local time */

        tt = time( 0 );
        lt = localtime( &tt );
        printf( "%02d-%02d %02d:%02d:%02d ", lt->tm_mon, lt->tm_mday,
                lt->tm_hour, lt->tm_min, lt->tm_sec );

        switch( ip->protocol )
        {
            case SOL_TCP:

                printf( " TCP: " );

                tcp = (struct tcphdr *) \
                        ( (void *) ip + sizeof( struct iphdr ) );

                /* grab source and destination port */

                sport = htons( tcp->source );
                dport = htons( tcp->dest );

            common:

                /* and print the most interesting informations */

                printf( "%15s : %-5d", inet_ntoa( src ), sport );
                printf( " -> " );
                printf( "%15s : %-5d", inet_ntoa( dst ), dport );
                printf( "  %4d\n", buflen );
                break;

            case SOL_UDP:

                udp = (struct udphdr *) \
                        ( (void *) ip + sizeof( struct iphdr ) );

                printf( " UDP: " );

                sport = htons( udp->source );
                dport = htons( udp->dest );

                goto common;

            case 1: /* SOL_ICMP */

                icmp = (struct icmphdr *) \
                        ( (void *) ip + sizeof( struct iphdr ) );

                printf( "ICMP: " );

                sport = icmp->type;
                dport = icmp->code;

                goto common;

            default :

                printf( "unsupported IP protocol %d\n", ip->protocol );
                break;
        }
    }

    return( 0 );
}