/*
 * Copyright (c) 2001 Fenris, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * File:  parser.c
 *
 * Purpose:  This source file defines the interface for parser().  This
 * function is a nested switch case statement that takes a packet through
 * the layers of the known protocols (TCP/IP stack as of rev 1.)  A packet
 * header object (as declared in headers.h) is populated by this function.
 *
 */


#include <sys/param.h>          /* ntoh[ls]() BSD */
#include <netinet/in.h>         /* ntoh[ls]() Linux */

#include "headers.h"            /* packet_headers */
#include "parser.h"


int parse(const unsigned char *buf, Packet_Headers *p)
{

    p->ll.eth = (Eth_Header *)buf;
    p->ll.eth->eth_typ = ntohs(p->ll.eth->eth_typ);
    buf += 14;

    switch (p->ll.eth->eth_typ) {
    case ETH_TYP_ARP:
    case ETH_TYP_RARP:
        p->type = arp_t;
        p->nl.arp = (Arp_Header *)buf;
        p->nl.arp->arp_hrd_typ = ntohs(p->nl.arp->arp_hrd_typ);
        p->nl.arp->arp_prt_typ = ntohs(p->nl.arp->arp_prt_typ);
        p->nl.arp->arp_typ = ntohs(p->nl.arp->arp_typ);
        buf += 28;
        break;
    case ETH_TYP_IP:
        p->nl.ip = (Ip_Header *)buf;
        p->nl.ip->ip_pkt_len = ntohs(p->nl.ip->ip_pkt_len);
        p->nl.ip->ip_id = ntohs(p->nl.ip->ip_id);
        p->nl.ip->ip_frg_off = ntohs(p->nl.ip->ip_frg_off);
        p->nl.ip->ip_chksum = ntohs(p->nl.ip->ip_chksum);
        p->nl.ip->ip_src = ntohl(p->nl.ip->ip_src);
        p->nl.ip->ip_dst = ntohl(p->nl.ip->ip_dst);
        buf += (p->nl.ip->ip_hdr_len * 4);

        switch (p->nl.ip->ip_protocol) {
        case IP_PRT_TCP:
            p->type = tcp_t;
            p->tl.tcp = (Tcp_Header *)buf;
            p->tl.tcp->tcp_src_port = ntohs(p->tl.tcp->tcp_src_port);
            p->tl.tcp->tcp_dst_port = ntohs(p->tl.tcp->tcp_dst_port);
            p->tl.tcp->tcp_seq_num = ntohl(p->tl.tcp->tcp_seq_num);
            p->tl.tcp->tcp_ack_num = ntohl(p->tl.tcp->tcp_ack_num);
            p->tl.tcp->tcp_win_siz = ntohs(p->tl.tcp->tcp_win_siz);
            p->tl.tcp->tcp_chksum = ntohs(p->tl.tcp->tcp_chksum);
            p->tl.tcp->tcp_urg_ptr = ntohs(p->tl.tcp->tcp_urg_ptr);
            buf += (p->tl.tcp->tcp_hdr_len * 4);
            break;
        case IP_PRT_UDP:
            p->type = udp_t;
            p->tl.udp = (Udp_Header *)buf;
            p->tl.udp->udp_src_port = ntohs(p->tl.udp->udp_src_port);
            p->tl.udp->udp_dst_port = ntohs(p->tl.udp->udp_dst_port);
            p->tl.udp->udp_len = ntohs(p->tl.udp->udp_len);
            p->tl.udp->udp_chksum = ntohs(p->tl.udp->udp_chksum);
            buf += 8;
            break;
        case IP_PRT_ICMP:
            p->type = icmp_t;
            p->tl.icmp = (Icmp_Header *)buf;
            p->tl.icmp->icmp_chksum = ntohs(p->tl.icmp->icmp_chksum);
            buf += 4;
            break;
        case IP_PRT_IGMP:
            p->type = igmp_t;
            p->tl.igmp = (Igmp_Header *)buf;
            p->tl.igmp->igmp_chksum = ntohs(p->tl.igmp->igmp_chksum);
            buf += 8;
            break;
        default:
            return -1;
            break;
        }
        break;
    default:
        return -1;
        break;
    }

    p->data = buf;
    return 0;
}