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8
9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10
11#include <linux/module.h>
12#include <linux/moduleparam.h>
13#include <linux/tcp.h>
14#include <linux/kernel.h>
15
16#include <net/netfilter/nf_nat.h>
17#include <net/netfilter/nf_nat_helper.h>
18#include <net/netfilter/nf_conntrack_helper.h>
19#include <net/netfilter/nf_conntrack_expect.h>
20#include <linux/netfilter/nf_conntrack_irc.h>
21
22#define NAT_HELPER_NAME "irc"
23
24MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
25MODULE_DESCRIPTION("IRC (DCC) NAT helper");
26MODULE_LICENSE("GPL");
27MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME);
28
29static struct nf_conntrack_nat_helper nat_helper_irc =
30 NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME);
31
32static unsigned int help(struct sk_buff *skb,
33 enum ip_conntrack_info ctinfo,
34 unsigned int protoff,
35 unsigned int matchoff,
36 unsigned int matchlen,
37 struct nf_conntrack_expect *exp)
38{
39 char buffer[sizeof("4294967296 65635")];
40 struct nf_conn *ct = exp->master;
41 union nf_inet_addr newaddr;
42 u_int16_t port;
43
44
45 newaddr = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3;
46
47 exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
48 exp->dir = IP_CT_DIR_REPLY;
49 exp->expectfn = nf_nat_follow_master;
50
51
52 for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
53 int ret;
54
55 exp->tuple.dst.u.tcp.port = htons(port);
56 ret = nf_ct_expect_related(exp, 0);
57 if (ret == 0)
58 break;
59 else if (ret != -EBUSY) {
60 port = 0;
61 break;
62 }
63 }
64
65 if (port == 0) {
66 nf_ct_helper_log(skb, ct, "all ports in use");
67 return NF_DROP;
68 }
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83
84 snprintf(buffer, sizeof(buffer), "%u %u", ntohl(newaddr.ip), port);
85 pr_debug("inserting '%s' == %pI4, port %u\n",
86 buffer, &newaddr.ip, port);
87
88 if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff,
89 matchlen, buffer, strlen(buffer))) {
90 nf_ct_helper_log(skb, ct, "cannot mangle packet");
91 nf_ct_unexpect_related(exp);
92 return NF_DROP;
93 }
94
95 return NF_ACCEPT;
96}
97
98static void __exit nf_nat_irc_fini(void)
99{
100 nf_nat_helper_unregister(&nat_helper_irc);
101 RCU_INIT_POINTER(nf_nat_irc_hook, NULL);
102 synchronize_rcu();
103}
104
105static int __init nf_nat_irc_init(void)
106{
107 BUG_ON(nf_nat_irc_hook != NULL);
108 nf_nat_helper_register(&nat_helper_irc);
109 RCU_INIT_POINTER(nf_nat_irc_hook, help);
110 return 0;
111}
112
113
114static int warn_set(const char *val, const struct kernel_param *kp)
115{
116 pr_info("kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
117 return 0;
118}
119module_param_call(ports, warn_set, NULL, NULL, 0);
120
121module_init(nf_nat_irc_init);
122module_exit(nf_nat_irc_fini);
123