nf_nat_irc.c 3.4 KB

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122
  1. // SPDX-License-Identifier: GPL-2.0-or-later
  2. /* IRC extension for TCP NAT alteration.
  3. *
  4. * (C) 2000-2001 by Harald Welte <laforge@gnumonks.org>
  5. * (C) 2004 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
  6. * based on a copy of RR's ip_nat_ftp.c
  7. */
  8. #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  9. #include <linux/module.h>
  10. #include <linux/moduleparam.h>
  11. #include <linux/tcp.h>
  12. #include <linux/kernel.h>
  13. #include <net/netfilter/nf_nat.h>
  14. #include <net/netfilter/nf_nat_helper.h>
  15. #include <net/netfilter/nf_conntrack_helper.h>
  16. #include <net/netfilter/nf_conntrack_expect.h>
  17. #include <linux/netfilter/nf_conntrack_irc.h>
  18. #define NAT_HELPER_NAME "irc"
  19. MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  20. MODULE_DESCRIPTION("IRC (DCC) NAT helper");
  21. MODULE_LICENSE("GPL");
  22. MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME);
  23. static struct nf_conntrack_nat_helper nat_helper_irc =
  24. NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME);
  25. static unsigned int help(struct sk_buff *skb,
  26. enum ip_conntrack_info ctinfo,
  27. unsigned int protoff,
  28. unsigned int matchoff,
  29. unsigned int matchlen,
  30. struct nf_conntrack_expect *exp)
  31. {
  32. char buffer[sizeof("4294967296 65635")];
  33. struct nf_conn *ct = exp->master;
  34. union nf_inet_addr newaddr;
  35. u_int16_t port;
  36. /* Reply comes from server. */
  37. newaddr = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3;
  38. exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
  39. exp->dir = IP_CT_DIR_REPLY;
  40. exp->expectfn = nf_nat_follow_master;
  41. /* Try to get same port: if not, try to change it. */
  42. for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
  43. int ret;
  44. exp->tuple.dst.u.tcp.port = htons(port);
  45. ret = nf_ct_expect_related(exp, 0);
  46. if (ret == 0)
  47. break;
  48. else if (ret != -EBUSY) {
  49. port = 0;
  50. break;
  51. }
  52. }
  53. if (port == 0) {
  54. nf_ct_helper_log(skb, ct, "all ports in use");
  55. return NF_DROP;
  56. }
  57. /* strlen("\1DCC CHAT chat AAAAAAAA P\1\n")=27
  58. * strlen("\1DCC SCHAT chat AAAAAAAA P\1\n")=28
  59. * strlen("\1DCC SEND F AAAAAAAA P S\1\n")=26
  60. * strlen("\1DCC MOVE F AAAAAAAA P S\1\n")=26
  61. * strlen("\1DCC TSEND F AAAAAAAA P S\1\n")=27
  62. *
  63. * AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits,
  64. * 255.255.255.255==4294967296, 10 digits)
  65. * P: bound port (min 1 d, max 5d (65635))
  66. * F: filename (min 1 d )
  67. * S: size (min 1 d )
  68. * 0x01, \n: terminators
  69. */
  70. /* AAA = "us", ie. where server normally talks to. */
  71. snprintf(buffer, sizeof(buffer), "%u %u", ntohl(newaddr.ip), port);
  72. pr_debug("inserting '%s' == %pI4, port %u\n",
  73. buffer, &newaddr.ip, port);
  74. if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff,
  75. matchlen, buffer, strlen(buffer))) {
  76. nf_ct_helper_log(skb, ct, "cannot mangle packet");
  77. nf_ct_unexpect_related(exp);
  78. return NF_DROP;
  79. }
  80. return NF_ACCEPT;
  81. }
  82. static void __exit nf_nat_irc_fini(void)
  83. {
  84. nf_nat_helper_unregister(&nat_helper_irc);
  85. RCU_INIT_POINTER(nf_nat_irc_hook, NULL);
  86. synchronize_rcu();
  87. }
  88. static int __init nf_nat_irc_init(void)
  89. {
  90. BUG_ON(nf_nat_irc_hook != NULL);
  91. nf_nat_helper_register(&nat_helper_irc);
  92. RCU_INIT_POINTER(nf_nat_irc_hook, help);
  93. return 0;
  94. }
  95. /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */
  96. static int warn_set(const char *val, const struct kernel_param *kp)
  97. {
  98. pr_info("kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
  99. return 0;
  100. }
  101. module_param_call(ports, warn_set, NULL, NULL, 0);
  102. module_init(nf_nat_irc_init);
  103. module_exit(nf_nat_irc_fini);