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/****************************************************************************
** File: ip.c
**
** Author: Mike Borella
**
** Comments: Dump IP header information
**
*****************************************************************************/
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include "config.h"
#include "ip.h"
#include "esp.h"
#include "ah.h"
#include "icmp.h"
#include "tcp.h"
#include "udp.h"
extern struct arg_t *my_args;
/*----------------------------------------------------------------------------
**
** in_cksum.c
**
** Do IP checksum
**
**----------------------------------------------------------------------------
*/
u_int16_t in_cksum(u_int16_t *addr, int len)
{
int nleft = len;
u_int16_t *w = addr;
u_int32_t sum = 0;
u_int16_t answer = 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_int8_t *)(&answer) = *(u_int8_t *)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);
}
/*----------------------------------------------------------------------------
**
** dump_ip()
**
** Parse IP header and dump fields
**
**----------------------------------------------------------------------------
*/
void dump_ip(const u_char *bp, int length)
{
IPHdr *ip, ip2;
u_int hlen, len, off;
u_char *cp = NULL;
u_int frag_off;
u_char tos;
u_int16_t csum;
u_int16_t my_csum;
/*
* Dump header announcement
*/
printf("-----------------------------------------------------------------\n");
printf(" IP Header\n");
printf("-----------------------------------------------------------------\n");
/*
* View the packet as an IP header
*/
ip = (IPHdr *) bp;
/*
* Check for truncated header and truncated packet
*/
if (length < sizeof(IPHdr))
{
printf("Truncated header, length = %d bytes\n", length);
return;
}
len = ntohs(ip->ip_len);
if (length < len)
{
printf("Truncated packet: length field = %d, actual length = %d\n",
len, length);
return;
}
/*
* Dump header fields
*/
csum = ntohs(ip->ip_csum);
hlen = ip->ip_hl*4;
if (!my_args->n)
{
/* Don't print anything except src and dst addresses in minmal mode */
if (!my_args->m)
{
printf("Version: %d\n", ip->ip_v);
printf("Header length: %d\n", hlen);
tos = ip->ip_tos;
printf("Type of service: %d", tos);
printf(" (precedence=%d, D=%d, T=%d, R=%d, U=%d)\n",
tos >> 5, (tos & 0x10) >> 4, (tos & 0x08) >> 3,
(tos & 0x04) >> 2, tos & 0x03);
printf("Total length: %d\n", ntohs(ip->ip_len));
printf("Identification #: %d\n", ntohs(ip->ip_id));
frag_off = ntohs(ip->ip_off);
printf("Fragmentation offset: %d", (frag_off & 0x1fff) * 8);
frag_off &= 0xe000;
printf(" (U=%d, DF=%d, MF=%d)\n", (frag_off & 0x8000) >> 15,
(frag_off & 0x4000) >> 14, (frag_off & 0x2000) >> 13);
printf("Time to live: %d\n", ip->ip_ttl);
printf("Protocol: %d\n", ip->ip_p);
printf("Header checksum: %d ", csum);
memcpy((void *) &ip2, (void *) ip, sizeof(IPHdr));
ip2.ip_csum = 0;
my_csum = ntohs(in_cksum((u_int16_t *) &ip2, sizeof(IPHdr)));
if (my_csum != csum) printf("(error: should be %d)", my_csum);
printf("\n");
}
printf("Source address %s\n", inet_ntoa(ip->ip_src));
printf("Destination address %s\n", inet_ntoa(ip->ip_dst));
}
/*
* If this is fragment zero, hand it to the next higher
* level protocol.
*/
len -= hlen;
off = ntohs(ip->ip_off);
if ((off & 0x1fff) == 0)
{
cp = (u_char *) ip + hlen;
switch (ip->ip_p)
{
case TCP_NEXT_HEADER:
dump_tcp(cp, len);
break;
case UDP_NEXT_HEADER:
dump_udp(cp, len);
break;
case ICMP_NEXT_HEADER:
dump_icmp(cp);
break;
case IP_NEXT_HEADER:
dump_ip(cp, len);
break;
case ESP_NEXT_HEADER:
dump_esp(cp, len);
break;
case AH_NEXT_HEADER:
dump_ah(cp, len);
break;
default:
break;
}
}
}
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