net/netfilter/nf_nat_tftp.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu>
   3  */
   4
   5 #include <linux/module.h>
   6 #include <linux/udp.h>
   7
   8 #include <net/netfilter/nf_conntrack_helper.h>
   9 #include <net/netfilter/nf_conntrack_expect.h>
  10 #include <net/netfilter/nf_nat_helper.h>
  11 #include <linux/netfilter/nf_conntrack_tftp.h>
  12
  13 #define NAT_HELPER_NAME "tftp"
  14
  15 MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
  16 MODULE_DESCRIPTION("TFTP NAT helper");
  17 MODULE_LICENSE("GPL");
  18 MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME);
  19
  20 static struct nf_conntrack_nat_helper nat_helper_tftp =
  21         NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME);
  22
  23 static unsigned int help(struct sk_buff *skb,
  24                          enum ip_conntrack_info ctinfo,
  25                          struct nf_conntrack_expect *exp)
  26 {
  27         const struct nf_conn *ct = exp->master;
  28
  29         exp->saved_proto.udp.port
  30                 = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
  31         exp->dir = IP_CT_DIR_REPLY;
  32         exp->expectfn = nf_nat_follow_master;
  33         if (nf_ct_expect_related(exp, 0) != 0) {
  34                 nf_ct_helper_log(skb, exp->master, "cannot add expectation");
  35                 return NF_DROP;
  36         }
  37         return NF_ACCEPT;
  38 }
  39
  40 static void __exit nf_nat_tftp_fini(void)
  41 {
  42         nf_nat_helper_unregister(&nat_helper_tftp);
  43         RCU_INIT_POINTER(nf_nat_tftp_hook, NULL);
  44         synchronize_rcu();
  45 }
  46
  47 static int __init nf_nat_tftp_init(void)
  48 {
  49         BUG_ON(nf_nat_tftp_hook != NULL);
  50         nf_nat_helper_register(&nat_helper_tftp);
  51         RCU_INIT_POINTER(nf_nat_tftp_hook, help);
  52         return 0;
  53 }
  54
  55 module_init(nf_nat_tftp_init);
  56 module_exit(nf_nat_tftp_fini);