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/* @(#) $Header: /home/ax25-cvs/ax25-apps/listen/tcpdump.c,v 1.2 2001/09/12 13:18:44 terry Exp $ */
/* TCP header tracing routines
* Copyright 1991 Phil Karn, KA9Q
*/
#include <stdio.h>
#include <string.h>
#include "listen.h"
#define FIN 0x01
#define SYN 0x02
#define RST 0x04
#define PSH 0x08
#define ACK 0x10
#define URG 0x20
#define CE 0x40
/* TCP options */
#define EOL_KIND 0
#define NOOP_KIND 1
#define MSS_KIND 2
#define MSS_LENGTH 4
#define TCPLEN 20
#define max(a,b) ((a) > (b) ? (a) : (b))
/* Dump a TCP segment header. Assumed to be in network byte order */
void tcp_dump(unsigned char *data, int length, int hexdump)
{
int source, dest;
int seq;
int ack;
int flags;
int wnd;
int up;
int hdrlen;
int mss = 0;
source = get16(data + 0);
dest = get16(data + 2);
seq = get32(data + 4);
ack = get32(data + 8);
hdrlen = (data[12] & 0xF0) >> 2;
flags = data[13];
wnd = get16(data + 14);
up = get16(data + 18);
lprintf(T_PROTOCOL, "TCP:");
lprintf(T_TCPHDR, " %s->", servname(source, "tcp"));
lprintf(T_TCPHDR, "%s Seq x%x", servname(dest, "tcp"), seq);
if (flags & ACK)
lprintf(T_TCPHDR, " Ack x%x", ack);
if (flags & CE)
lprintf(T_TCPHDR, " CE");
if (flags & URG)
lprintf(T_TCPHDR, " URG");
if (flags & ACK)
lprintf(T_TCPHDR, " ACK");
if (flags & PSH)
lprintf(T_TCPHDR, " PSH");
if (flags & RST)
lprintf(T_TCPHDR, " RST");
if (flags & SYN)
lprintf(T_TCPHDR, " SYN");
if (flags & FIN)
lprintf(T_TCPHDR, " FIN");
lprintf(T_TCPHDR, " Wnd %d", wnd);
if (flags & URG)
lprintf(T_TCPHDR, " UP x%x", up);
/* Process options, if any */
if (hdrlen > TCPLEN && length >= hdrlen) {
unsigned char *cp = data + TCPLEN;
int i = hdrlen - TCPLEN;
int kind, optlen;
while (i > 0) {
kind = *cp++;
/* Process single-byte options */
switch (kind) {
case EOL_KIND:
i--;
cp++;
break;
case NOOP_KIND:
i--;
cp++;
continue;
}
/* All other options have a length field */
optlen = *cp++;
/* Process valid multi-byte options */
switch (kind) {
case MSS_KIND:
if (optlen == MSS_LENGTH)
mss = get16(cp);
break;
}
optlen = max(2, optlen); /* Enforce legal minimum */
i -= optlen;
cp += optlen - 2;
}
}
if (mss != 0)
lprintf(T_TCPHDR, " MSS %d", mss);
length -= hdrlen;
data += hdrlen;
if (length > 0) {
lprintf(T_TCPHDR, " Data %d\n", length);
data_dump(data, length, hexdump);
return;
}
lprintf(T_TCPHDR, "\n");
}
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