nf_nat_irc.c

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/* IRC extension for TCP NAT alteration.
 *
 * (C) 2000-2001 by Harald Welte <[email protected]>
 * (C) 2004 Rusty Russell <[email protected]> IBM Corporation
 * based on a copy of RR's ip_nat_ftp.c
 *
 * 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.
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/tcp.h>
#include <linux/kernel.h>

#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_helper.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <linux/netfilter/nf_conntrack_irc.h>

MODULE_AUTHOR("Harald Welte <[email protected]>");
MODULE_DESCRIPTION("IRC (DCC) NAT helper");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ip_nat_irc");

static unsigned int help(struct sk_buff *skb,
             enum ip_conntrack_info ctinfo,
             unsigned int protoff,
             unsigned int matchoff,
             unsigned int matchlen,
             struct nf_conntrack_expect *exp)
{
    char buffer[sizeof("4294967296 65635")];
    u_int16_t port;
    unsigned int ret;

    /* Reply comes from server. */
    exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
    exp->dir = IP_CT_DIR_REPLY;
    exp->expectfn = nf_nat_follow_master;

    /* Try to get same port: if not, try to change it. */
    for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
        int ret;

        exp->tuple.dst.u.tcp.port = htons(port);
        ret = nf_ct_expect_related(exp);
        if (ret == 0)
            break;
        else if (ret != -EBUSY) {
            port = 0;
            break;
        }
    }

    if (port == 0)
        return NF_DROP;

    ret = nf_nat_mangle_tcp_packet(skb, exp->master, ctinfo,
                       protoff, matchoff, matchlen, buffer,
                       strlen(buffer));
    if (ret != NF_ACCEPT)
        nf_ct_unexpect_related(exp);
    return ret;
}

static void __exit nf_nat_irc_fini(void)
{
    RCU_INIT_POINTER(nf_nat_irc_hook, NULL);
    synchronize_rcu();
}

static int __init nf_nat_irc_init(void)
{
    BUG_ON(nf_nat_irc_hook != NULL);
    RCU_INIT_POINTER(nf_nat_irc_hook, help);
    return 0;
}

/* Prior to 2.6.11, we had a ports param.  No longer, but don't break users. */
static int warn_set(const char *val, struct kernel_param *kp)
{
    printk(KERN_INFO KBUILD_MODNAME
           ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
    return 0;
}
module_param_call(ports, warn_set, NULL, NULL, 0);

module_init(nf_nat_irc_init);
module_exit(nf_nat_irc_fini);