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Decrease TTL for forwarded packets

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This commit is contained in:
adamdunkels 2008-02-24 21:14:25 +00:00
parent 3106840c56
commit 57f2dfa743
4 changed files with 82 additions and 25 deletions
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89
tools/wpcapslip/wpcapslip.c
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@ -30,7 +30,7 @@
*
* Author: Oliver Schmidt <ol.sc@web.de>
*
* $Id: wpcapslip.c,v 1.1 2008/02/07 09:39:35 adamdunkels Exp $
* $Id: wpcapslip.c,v 1.2 2008/02/24 21:14:25 adamdunkels Exp $
*/
@ -71,6 +71,21 @@ void wpcap_send(void *buf, int len);
uint16_t wpcap_poll(char **buf);
#include "net/tcpdump.h"
static int should_print = 0;
#define IP_HLEN 20
/*---------------------------------------------------------------------------*/
static void
print_packet(uint8_t *packet, int len)
{
char buf[2000];
if(should_print) {
tcpdump_format(packet, len, buf, sizeof(buf));
printf("%s\n", buf);
}
}
/*---------------------------------------------------------------------------*/
void cleanup(void);
/*---------------------------------------------------------------------------*/
@ -109,7 +124,7 @@ struct ip {
u_int16_t uh_sum; /* udp checksum */
};
static int ip_id;
static int ip_id, last_id;
int
ssystem(const char *fmt, ...) __attribute__((__format__ (__printf__, 1, 2)));
@ -163,6 +178,12 @@ ip4sum(u_int16_t sum, const void *_p, u_int16_t len)
return sum;
}
static uint16_t
chksum(const void *p, uint16_t len)
{
uint16_t sum = ip4sum(0, p, len);
return (sum == 0) ? 0xffff : htons(sum);
}
int
check_ip(const struct ip *ip, unsigned ip_len)
@ -170,20 +191,24 @@ check_ip(const struct ip *ip, unsigned ip_len)
u_int16_t sum, ip_hl;
/* Check IP version and length. */
if((ip->ip_vhl & IP_V) != IP_V4)
if((ip->ip_vhl & IP_V) != IP_V4) {
return -1;
}
if(ntohs(ip->ip_len) > ip_len)
if(ntohs(ip->ip_len) > ip_len) {
return -2;
}
if(ntohs(ip->ip_len) < ip_len)
if(ntohs(ip->ip_len) < ip_len) {
return -3;
}
/* Check IP header. */
ip_hl = 4*(ip->ip_vhl & IP_HL);
sum = ip4sum(0, ip, ip_hl);
if(sum != 0xffff && sum != 0x0)
if(sum != 0xffff && sum != 0x0) {
return -4;
}
if(ip->ip_p == 6 || ip->ip_p == 17) { /* Check TCP or UDP header. */
u_int16_t tcp_len = ip_len - ip_hl;
@ -196,21 +221,23 @@ check_ip(const struct ip *ip, unsigned ip_len)
sum = ip4sum(sum, (u_int8_t*)ip + ip_hl, tcp_len);
/* Failed checksum test? */
if (sum != 0xffff && sum != 0x0) {
if (ip->ip_p == 6) { /* TCP == 6 */
if(sum != 0xffff && sum != 0x0) {
if(ip->ip_p == 6) { /* TCP == 6 */
return -5;
} else { /* UDP */
/* Deal with disabled UDP checksums. */
if (ip->uh_sum != 0)
if(ip->uh_sum != 0) {
return -6;
}
}
}
} else if (ip->ip_p == 1) { /* ICMP */
u_int16_t icmp_len = ip_len - ip_hl;
sum = ip4sum(0, (u_int8_t*)ip + ip_hl, icmp_len);
if(sum != 0xffff && sum != 0x0)
if(sum != 0xffff && sum != 0x0) {
return -7;
}
}
return 0;
}
@ -331,6 +358,7 @@ serial_to_wpcap(FILE *inslip)
err(1, "serial_to_tun: write");
}*/
/* printf("Sending to wpcap\n");*/
print_packet(uip.inbuf, inbufptr);
wpcap_send(uip.inbuf, inbufptr);
/* printf("After sending to wpcap\n");*/
inbufptr = 0;
@ -429,11 +457,25 @@ write_to_serial(int outfd, void *inbuf, int len)
}
ecode = check_ip(inbuf, len);
if(ecode < 0) {
fprintf(stderr, "tun_to_serial: drop packet %d\n", ecode);
fprintf(stderr, "write_to_serial: drop packet %d\n", ecode);
return;
}
}
iphdr->ip_ttl = htons(htons(iphdr->ip_ttl) + 1);
if(iphdr->ip_ttl == 0) {
fprintf(stderr, "Packet with ttl %d dropped\n", iphdr->ip_ttl);
return;
}
iphdr->ip_sum = 0;
iphdr->ip_sum = ~chksum(iphdr, 4 * (iphdr->ip_vhl & IP_HL));
ecode = check_ip(inbuf, len);
if(ecode < 0) {
fprintf(stderr, "write_to_serial: drop packet %d\n", ecode);
return;
}
/* It would be ``nice'' to send a SLIP_END here but it's not
* really necessary.
*/
@ -456,6 +498,7 @@ write_to_serial(int outfd, void *inbuf, int len)
}
slip_send(outfd, SLIP_END);
/* printf("slip end\n");*/
PROGRESS("t");
}
/*---------------------------------------------------------------------------*/
@ -626,7 +669,7 @@ main(int argc, char **argv)
setvbuf(stdout, NULL, _IOLBF, 0); /* Line buffered output. */
while((c = getopt(argc, argv, "B:D:hs:t:")) != -1) {
while((c = getopt(argc, argv, "B:D:hs:t:T")) != -1) {
switch (c) {
case 'B':
baudrate = atoi(optarg);
@ -653,11 +696,15 @@ main(int argc, char **argv)
}
break;
#endif /* 0 */
case 'T':
should_print = 1;
break;
case '?':
case 'h':
default:
err(1, "usage: wpcapslip [-B baudrate] [-s siodev] [-D dhcp-server] ipaddress netmask [dhcp-server]");
err(1, "usage: wpcapslip [-B baudrate] [-s siodev] [-D dhcp-server] [-T] ipaddress netmask [dhcp-server]");
break;
}
}
@ -665,7 +712,7 @@ main(int argc, char **argv)
argv += (optind - 1);
if(argc != 4) {
err(1, "usage: wpcapslip [-s siodev] [-D dhcp-server] <IP address of local Ethernet card> <IP address of SLIP network> <netmask of SLIP network>");
err(1, "usage: wpcapslip [-s siodev] [-D dhcp-server] [-T] <IP address of local Ethernet card> <IP address of SLIP network> <netmask of SLIP network>");
}
/* ipaddr = argv[1];
netmask = argv[2];*/
@ -848,11 +895,15 @@ main(int argc, char **argv)
ret = wpcap_poll(&pbuf);
if(ret > 0) {
/* printf("wpcap_poll ret %d", ret);
printf("IP packet\n");*/
write_to_serial(slipfd, pbuf, ret);
slip_flushbuf(slipfd);
sigalarm_reset();
struct ip *iphdr = (struct ip *)pbuf;
if(iphdr->ip_id != last_id) {
last_id = iphdr->ip_id;
/* printf("------ wpcap_poll ret %d\n", ret);*/
print_packet(pbuf, ret);
write_to_serial(slipfd, pbuf, ret);
slip_flushbuf(slipfd);
sigalarm_reset();
}
}
/* } else {
printf("!slip_empty\n");*/