net/netfilter/nf_conntrack_tftp.c

   1 /* (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu>
   2  *
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License version 2 as
   5  * published by the Free Software Foundation.
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/moduleparam.h>
  10 #include <linux/in.h>
  11 #include <linux/udp.h>
  12 #include <linux/netfilter.h>
  13
  14 #include <net/netfilter/nf_conntrack.h>
  15 #include <net/netfilter/nf_conntrack_tuple.h>
  16 #include <net/netfilter/nf_conntrack_expect.h>
  17 #include <net/netfilter/nf_conntrack_ecache.h>
  18 #include <net/netfilter/nf_conntrack_helper.h>
  19 #include <linux/netfilter/nf_conntrack_tftp.h>
  20
  21 MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
  22 MODULE_DESCRIPTION("TFTP connection tracking helper");
  23 MODULE_LICENSE("GPL");
  24 MODULE_ALIAS("ip_conntrack_tftp");
  25
  26 #define MAX_PORTS 8
  27 static unsigned short ports[MAX_PORTS];
  28 static unsigned int ports_c;
  29 module_param_array(ports, ushort, &ports_c, 0400);
  30 MODULE_PARM_DESC(ports, "Port numbers of TFTP servers");
  31
  32 unsigned int (*nf_nat_tftp_hook)(struct sk_buff *skb,
  33                                  enum ip_conntrack_info ctinfo,
  34                                  struct nf_conntrack_expect *exp) __read_mostly;
  35 EXPORT_SYMBOL_GPL(nf_nat_tftp_hook);
  36
  37 static int tftp_help(struct sk_buff *skb,
  38                      unsigned int protoff,
  39                      struct nf_conn *ct,
  40                      enum ip_conntrack_info ctinfo)
  41 {
  42         const struct tftphdr *tfh;
  43         struct tftphdr _tftph;
  44         struct nf_conntrack_expect *exp;
  45         struct nf_conntrack_tuple *tuple;
  46         unsigned int ret = NF_ACCEPT;
  47         typeof(nf_nat_tftp_hook) nf_nat_tftp;
  48
  49         tfh = skb_header_pointer(skb, protoff + sizeof(struct udphdr),
  50                                  sizeof(_tftph), &_tftph);
  51         if (tfh == NULL)
  52                 return NF_ACCEPT;
  53
  54         switch (ntohs(tfh->opcode)) {
  55         case TFTP_OPCODE_READ:
  56         case TFTP_OPCODE_WRITE:
  57                 /* RRQ and WRQ works the same way */
  58                 nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
  59                 nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  60
  61                 exp = nf_ct_expect_alloc(ct);
  62                 if (exp == NULL)
  63                         return NF_DROP;
  64                 tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  65                 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
  66                                   nf_ct_l3num(ct),
  67                                   &tuple->src.u3, &tuple->dst.u3,
  68                                   IPPROTO_UDP, NULL, &tuple->dst.u.udp.port);
  69
  70                 pr_debug("expect: ");
  71                 nf_ct_dump_tuple(&exp->tuple);
  72
  73                 nf_nat_tftp = rcu_dereference(nf_nat_tftp_hook);
  74                 if (nf_nat_tftp && ct->status & IPS_NAT_MASK)
  75                         ret = nf_nat_tftp(skb, ctinfo, exp);
  76                 else if (nf_ct_expect_related(exp) != 0)
  77                         ret = NF_DROP;
  78                 nf_ct_expect_put(exp);
  79                 break;
  80         case TFTP_OPCODE_DATA:
  81         case TFTP_OPCODE_ACK:
  82                 pr_debug("Data/ACK opcode\n");
  83                 break;
  84         case TFTP_OPCODE_ERROR:
  85                 pr_debug("Error opcode\n");
  86                 break;
  87         default:
  88                 pr_debug("Unknown opcode\n");
  89         }
  90         return ret;
  91 }
  92
  93 static struct nf_conntrack_helper tftp[MAX_PORTS][2] __read_mostly;
  94 static char tftp_names[MAX_PORTS][2][sizeof("tftp-65535")] __read_mostly;
  95
  96 static const struct nf_conntrack_expect_policy tftp_exp_policy = {
  97         .max_expected   = 1,
  98         .timeout        = 5 * 60,
  99 };
 100
 101 static void nf_conntrack_tftp_fini(void)
 102 {
 103         int i, j;
 104
 105         for (i = 0; i < ports_c; i++) {
 106                 for (j = 0; j < 2; j++)
 107                         nf_conntrack_helper_unregister(&tftp[i][j]);
 108         }
 109 }
 110
 111 static int __init nf_conntrack_tftp_init(void)
 112 {
 113         int i, j, ret;
 114         char *tmpname;
 115
 116         if (ports_c == 0)
 117                 ports[ports_c++] = TFTP_PORT;
 118
 119         for (i = 0; i < ports_c; i++) {
 120                 memset(&tftp[i], 0, sizeof(tftp[i]));
 121
 122                 tftp[i][0].tuple.src.l3num = AF_INET;
 123                 tftp[i][1].tuple.src.l3num = AF_INET6;
 124                 for (j = 0; j < 2; j++) {
 125                         tftp[i][j].tuple.dst.protonum = IPPROTO_UDP;
 126                         tftp[i][j].tuple.src.u.udp.port = htons(ports[i]);
 127                         tftp[i][j].expect_policy = &tftp_exp_policy;
 128                         tftp[i][j].me = THIS_MODULE;
 129                         tftp[i][j].help = tftp_help;
 130
 131                         tmpname = &tftp_names[i][j][0];
 132                         if (ports[i] == TFTP_PORT)
 133                                 sprintf(tmpname, "tftp");
 134                         else
 135                                 sprintf(tmpname, "tftp-%u", i);
 136                         tftp[i][j].name = tmpname;
 137
 138                         ret = nf_conntrack_helper_register(&tftp[i][j]);
 139                         if (ret) {
 140                                 printk("nf_ct_tftp: failed to register helper "
 141                                        "for pf: %u port: %u\n",
 142                                         tftp[i][j].tuple.src.l3num, ports[i]);
 143                                 nf_conntrack_tftp_fini();
 144                                 return ret;
 145                         }
 146                 }
 147         }
 148         return 0;
 149 }
 150
 151 module_init(nf_conntrack_tftp_init);
 152 module_exit(nf_conntrack_tftp_fini);