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/*
* tcpnice.c
*
* Slow down TCP connections already in progress.
*
* Copyright (c) 2000 Dug Song <dugsong@monkey.org>
*
* $Id: tcpnice.c,v 1.17 2001/03/17 07:41:51 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 MIN_WIN 1 /* XXX */
#define MIN_MTU 68 /* RFC 1191 */
static int Opt_icmp;
static int Opt_pmtu;
static int Opt_win;
static int pcap_off;
static u_char buf[BUFSIZ];
static void
usage(void)
{
fprintf(stderr, "Version: " VERSION "\n"
"Usage: tcpnice [-A] [-I] [-M] [-i interface] expression\n");
exit(1);
}
static void
send_tcp_window_advertisement(int sock, struct libnet_ip_hdr *ip,
struct libnet_tcp_hdr *tcp)
{
int len;
ip->ip_hl = 5;
ip->ip_len = htons(IP_H + TCP_H);
ip->ip_id = libnet_get_prand(PRu16);
memcpy(buf, (u_char *)ip, IP_H);
tcp->th_off = 5;
tcp->th_win = htons(MIN_WIN);
memcpy(buf + IP_H, (u_char *)tcp, TCP_H);
libnet_do_checksum(buf, IPPROTO_TCP, TCP_H);
len = IP_H + TCP_H;
if (libnet_write_ip(sock, buf, len) != len)
warn("write");
fprintf(stderr, "%s:%d > %s:%d: . ack %lu win %d\n",
libnet_host_lookup(ip->ip_src.s_addr, 0), ntohs(tcp->th_sport),
libnet_host_lookup(ip->ip_dst.s_addr, 0), ntohs(tcp->th_dport),
ntohl(tcp->th_ack), 1);
}
static void
send_icmp_source_quench(int sock, struct libnet_ip_hdr *ip)
{
struct libnet_icmp_hdr *icmp;
int len;
len = (ip->ip_hl * 4) + 8;
libnet_build_ip(ICMP_ECHO_H + len, 0, libnet_get_prand(PRu16),
0, 64, IPPROTO_ICMP, ip->ip_dst.s_addr,
ip->ip_src.s_addr, NULL, 0, buf);
icmp = (struct libnet_icmp_hdr *)(buf + IP_H);
icmp->icmp_type = ICMP_SOURCEQUENCH;
icmp->icmp_code = 0;
memcpy((u_char *)icmp + ICMP_ECHO_H, (u_char *)ip, len);
libnet_do_checksum(buf, IPPROTO_ICMP, ICMP_ECHO_H + len);
len += (IP_H + ICMP_ECHO_H);
if (libnet_write_ip(sock, buf, len) != len)
warn("write");
fprintf(stderr, "%s > %s: icmp: source quench\n",
libnet_host_lookup(ip->ip_dst.s_addr, 0),
libnet_host_lookup(ip->ip_src.s_addr, 0));
}
static void
send_icmp_frag_needed(int sock, struct libnet_ip_hdr *ip)
{
struct libnet_icmp_hdr *icmp;
int len;
len = (ip->ip_hl * 4) + 8;
libnet_build_ip(ICMP_MASK_H + len, 4, libnet_get_prand(PRu16),
0, 64, IPPROTO_ICMP, ip->ip_dst.s_addr,
ip->ip_src.s_addr, NULL, 0, buf);
icmp = (struct libnet_icmp_hdr *)(buf + IP_H);
icmp->icmp_type = ICMP_UNREACH;
icmp->icmp_code = ICMP_UNREACH_NEEDFRAG;
icmp->hun.frag.pad = 0;
icmp->hun.frag.mtu = htons(MIN_MTU);
memcpy((u_char *)icmp + ICMP_MASK_H, (u_char *)ip, len);
libnet_do_checksum(buf, IPPROTO_ICMP, ICMP_MASK_H + len);
len += (IP_H + ICMP_MASK_H);
if (libnet_write_ip(sock, buf, len) != len)
warn("write");
fprintf(stderr, "%s > %s: icmp: ",
libnet_host_lookup(ip->ip_dst.s_addr, 0),
libnet_host_lookup(ip->ip_src.s_addr, 0));
fprintf(stderr, "%s unreachable - need to frag (mtu %d)\n",
libnet_host_lookup(ip->ip_src.s_addr, 0), MIN_MTU);
}
static void
tcp_nice_cb(u_char *user, const struct pcap_pkthdr *pcap, const u_char *pkt)
{
struct libnet_ip_hdr *ip;
struct libnet_tcp_hdr *tcp;
int *sock, len;
sock = (int *)user;
pkt += pcap_off;
len = pcap->caplen - pcap_off;
ip = (struct libnet_ip_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;
if (ntohs(ip->ip_len) > (ip->ip_hl << 2) + (tcp->th_off << 2)) {
if (Opt_icmp)
send_icmp_source_quench(*sock, ip);
if (Opt_win)
send_tcp_window_advertisement(*sock, ip, tcp);
if (Opt_pmtu)
send_icmp_frag_needed(*sock, ip);
}
}
int
main(int argc, char *argv[])
{
extern char *optarg;
extern int optind;
int c, sock;
char *intf, *filter, ebuf[PCAP_ERRBUF_SIZE];
pcap_t *pd;
intf = NULL;
while ((c = getopt(argc, argv, "i:AIMh?V")) != -1) {
switch (c) {
case 'i':
intf = optarg;
break;
case 'A':
Opt_win = 1;
break;
case 'I':
Opt_icmp = 1;
break;
case 'M':
Opt_pmtu = 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();
if ((Opt_win | Opt_icmp | Opt_pmtu) == 0)
Opt_win = Opt_icmp = Opt_pmtu = 1;
filter = copy_argv(argv);
if ((pd = pcap_init(intf, filter, 128)) == NULL)
errx(1, "couldn't initialize sniffing");
if ((pcap_off = pcap_dloff(pd)) < 0)
errx(1, "couldn't determine link layer offset");
if ((sock = libnet_open_raw_sock(IPPROTO_RAW)) == -1)
errx(1, "couldn't initialize sending");
libnet_seed_prand();
warnx("listening on %s [%s]", intf, filter);
pcap_loop(pd, -1, tcp_nice_cb, (u_char *)&sock);
/* NOTREACHED */
exit(0);
}
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