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* (C) 2000-2002 by Harald Welte <laforge@gnumonks.org>
* based on RR's ip_conntrack_ftp.c
*
* ip_conntrack_irc.c,v 1.21 2002/02/05 14:49:26 laforge Exp
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
**
* Module load syntax:
* insmod ip_conntrack_irc.o ports=port1,port2,...port<MAX_PORTS>
* max_dcc_channels=n dcc_timeout=secs
*
* please give the ports of all IRC servers You wish to connect to.
* If You don't specify ports, the default will be port 6667.
* With max_dcc_channels you can define the maximum number of not
* yet answered DCC channels per IRC session (default 8).
* With dcc_timeout you can specify how long the system waits for
* an expected DCC channel (default 300 seconds).
*
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/netfilter.h>
#include <linux/ip.h>
#include <net/checksum.h>
#include <net/tcp.h>
#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
#include <linux/netfilter_ipv4/ip_conntrack_irc.h>
#include <linux/moduleparam.h>
#define MAX_PORTS 8
static unsigned short ports[MAX_PORTS];
static int ports_c;
static unsigned int max_dcc_channels = 8;
static unsigned int dcc_timeout = 300;
/* This is slow, but it's simple. --RR */
static char *irc_buffer;
static DEFINE_SPINLOCK(irc_buffer_lock);
unsigned int (*ip_nat_irc_hook)(struct sk_buff **pskb,
enum ip_conntrack_info ctinfo,
unsigned int matchoff,
unsigned int matchlen,
struct ip_conntrack_expect *exp);
EXPORT_SYMBOL_GPL(ip_nat_irc_hook);
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("IRC (DCC) connection tracking helper");
MODULE_LICENSE("GPL");
module_param_array(ports, ushort, &ports_c, 0400);
MODULE_PARM_DESC(ports, "port numbers of IRC servers");
module_param(max_dcc_channels, uint, 0400);
MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per IRC session");
module_param(dcc_timeout, uint, 0400);
MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels");
static const char *dccprotos[] = { "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " };
#define MINMATCHLEN 5
#if 0
#define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s:" format, \
__FILE__, __FUNCTION__ , ## args)
#else
#define DEBUGP(format, args...)
#endif
static int parse_dcc(char *data, char *data_end, u_int32_t *ip,
u_int16_t *port, char **ad_beg_p, char **ad_end_p)
/* tries to get the ip_addr and port out of a dcc command
return value: -1 on failure, 0 on success
data pointer to first byte of DCC command data
data_end pointer to last byte of dcc command data
ip returns parsed ip of dcc command
port returns parsed port of dcc command
ad_beg_p returns pointer to first byte of addr data
ad_end_p returns pointer to last byte of addr data */
{
/* at least 12: "AAAAAAAA P\1\n" */
while (*data++ != ' ')
if (data > data_end - 12)
return -1;
*ad_beg_p = data;
*ip = simple_strtoul(data, &data, 10);
/* skip blanks between ip and port */
while (*data == ' ') {
if (data >= data_end)
return -1;
data++;
}
*port = simple_strtoul(data, &data, 10);
*ad_end_p = data;
return 0;
}
static int help(struct sk_buff **pskb,
struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
{
unsigned int dataoff;
struct tcphdr _tcph, *th;
char *data, *data_limit, *ib_ptr;
int dir = CTINFO2DIR(ctinfo);
struct ip_conntrack_expect *exp;
u32 seq;
u_int32_t dcc_ip;
u_int16_t dcc_port;
int i, ret = NF_ACCEPT;
char *addr_beg_p, *addr_end_p;
DEBUGP("entered\n");
/* If packet is coming from IRC server */
if (dir == IP_CT_DIR_REPLY)
return NF_ACCEPT;
/* Until there's been traffic both ways, don't look in packets. */
if (ctinfo != IP_CT_ESTABLISHED
&& ctinfo != IP_CT_ESTABLISHED + IP_CT_IS_REPLY) {
DEBUGP("Conntrackinfo = %u\n", ctinfo);
return NF_ACCEPT;
}
/* Not a full tcp header? */
th = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4,
sizeof(_tcph), &_tcph);
if (th == NULL)
return NF_ACCEPT;
/* No data? */
dataoff = (*pskb)->nh.iph->ihl*4 + th->doff*4;
if (dataoff >= (*pskb)->len)
return NF_ACCEPT;
spin_lock_bh(&irc_buffer_lock);
ib_ptr = skb_header_pointer(*pskb, dataoff,
(*pskb)->len - dataoff, irc_buffer);
BUG_ON(ib_ptr == NULL);
data = ib_ptr;
data_limit = ib_ptr + (*pskb)->len - dataoff;
/* strlen("\1DCC SENT t AAAAAAAA P\1\n")=24
* 5+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=14 */
while (data < (data_limit - (19 + MINMATCHLEN))) {
if (memcmp(data, "\1DCC ", 5)) {
data++;
continue;
}
data += 5;
/* we have at least (19+MINMATCHLEN)-5 bytes valid data left */
DEBUGP("DCC found in master %u.%u.%u.%u:%u %u.%u.%u.%u:%u...\n",
NIPQUAD(iph->saddr), ntohs(th->source),
NIPQUAD(iph->daddr), ntohs(th->dest));
for (i = 0; i < ARRAY_SIZE(dccprotos); i++) {
if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) {
/* no match */
continue;
}
DEBUGP("DCC %s detected\n", dccprotos[i]);
data += strlen(dccprotos[i]);
/* we have at least
* (19+MINMATCHLEN)-5-dccprotos[i].matchlen bytes valid
* data left (== 14/13 bytes) */
if (parse_dcc((char *)data, data_limit, &dcc_ip,
&dcc_port, &addr_beg_p, &addr_end_p)) {
/* unable to parse */
DEBUGP("unable to parse dcc command\n");
continue;
}
DEBUGP("DCC bound ip/port: %u.%u.%u.%u:%u\n",
HIPQUAD(dcc_ip), dcc_port);
/* dcc_ip can be the internal OR external (NAT'ed) IP
* Tiago Sousa <mirage@kaotik.org> */
if (ct->tuplehash[dir].tuple.src.ip != htonl(dcc_ip)
&& ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip != htonl(dcc_ip)) {
if (net_ratelimit())
printk(KERN_WARNING
"Forged DCC command from "
"%u.%u.%u.%u: %u.%u.%u.%u:%u\n",
NIPQUAD(ct->tuplehash[dir].tuple.src.ip),
HIPQUAD(dcc_ip), dcc_port);
continue;
}
exp = ip_conntrack_expect_alloc(ct);
if (exp == NULL) {
ret = NF_DROP;
goto out;
}
/* save position of address in dcc string,
* necessary for NAT */
DEBUGP("tcph->seq = %u\n", th->seq);
seq = ntohl(th->seq) + (addr_beg_p - ib_ptr);
/* We refer to the reverse direction ("!dir")
* tuples here, because we're expecting
* something in the other * direction.
* Doesn't matter unless NAT is happening. */
exp->tuple = ((struct ip_conntrack_tuple)
{ { 0, { 0 } },
{ ct->tuplehash[!dir].tuple.dst.ip,
{ .tcp = { htons(dcc_port) } },
IPPROTO_TCP }});
exp->mask = ((struct ip_conntrack_tuple)
{ { 0, { 0 } },
{ 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFF }});
exp->expectfn = NULL;
exp->flags = 0;
if (ip_nat_irc_hook)
ret = ip_nat_irc_hook(pskb, ctinfo,
addr_beg_p - ib_ptr,
addr_end_p - addr_beg_p,
exp);
else if (ip_conntrack_expect_related(exp) != 0)
ret = NF_DROP;
ip_conntrack_expect_put(exp);
goto out;
} /* for .. NUM_DCCPROTO */
} /* while data < ... */
out:
spin_unlock_bh(&irc_buffer_lock);
return ret;
}
static struct ip_conntrack_helper irc_helpers[MAX_PORTS];
static char irc_names[MAX_PORTS][sizeof("irc-65535")];
static void ip_conntrack_irc_fini(void);
static int __init ip_conntrack_irc_init(void)
{
int i, ret;
struct ip_conntrack_helper *hlpr;
char *tmpname;
if (max_dcc_channels < 1) {
printk("ip_conntrack_irc: max_dcc_channels must be a positive integer\n");
return -EBUSY;
}
irc_buffer = kmalloc(65536, GFP_KERNEL);
if (!irc_buffer)
return -ENOMEM;
/* If no port given, default to standard irc port */
if (ports_c == 0)
ports[ports_c++] = IRC_PORT;
for (i = 0; i < ports_c; i++) {
hlpr = &irc_helpers[i];
hlpr->tuple.src.u.tcp.port = htons(ports[i]);
hlpr->tuple.dst.protonum = IPPROTO_TCP;
hlpr->mask.src.u.tcp.port = 0xFFFF;
hlpr->mask.dst.protonum = 0xFF;
hlpr->max_expected = max_dcc_channels;
hlpr->timeout = dcc_timeout;
hlpr->me = THIS_MODULE;
hlpr->help = help;
tmpname = &irc_names[i][0];
if (ports[i] == IRC_PORT)
sprintf(tmpname, "irc");
else
sprintf(tmpname, "irc-%d", i);
hlpr->name = tmpname;
DEBUGP("port #%d: %d\n", i, ports[i]);
ret = ip_conntrack_helper_register(hlpr);
if (ret) {
printk("ip_conntrack_irc: ERROR registering port %d\n",
ports[i]);
ip_conntrack_irc_fini();
return -EBUSY;
}
}
return 0;
}
/* This function is intentionally _NOT_ defined as __exit, because
* it is needed by the init function */
static void ip_conntrack_irc_fini(void)
{
int i;
for (i = 0; i < ports_c; i++) {
DEBUGP("unregistering port %d\n",
ports[i]);
ip_conntrack_helper_unregister(&irc_helpers[i]);
}
kfree(irc_buffer);
}
module_init(ip_conntrack_irc_init);
module_exit(ip_conntrack_irc_fini);
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