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         int family = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.l3num;
  48         typeof(nf_nat_tftp_hook) nf_nat_tftp;
  49
  50         tfh = skb_header_pointer(skb, protoff + sizeof(struct udphdr),
  51                                  sizeof(_tftph), &_tftph);
  52         if (tfh == NULL)
  53                 return NF_ACCEPT;
  54
  55         switch (ntohs(tfh->opcode)) {
  56         case TFTP_OPCODE_READ:
  57         case TFTP_OPCODE_WRITE:
  58                 /* RRQ and WRQ works the same way */
  59                 NF_CT_DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
  60                 NF_CT_DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  61
  62                 exp = nf_ct_expect_alloc(ct);
  63                 if (exp == NULL)
  64                         return NF_DROP;
  65                 tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  66                 nf_ct_expect_init(exp, family, &tuple->src.u3, &tuple->dst.u3,
  67                                   IPPROTO_UDP, NULL, &tuple->dst.u.udp.port);
  68
  69                 pr_debug("expect: ");
  70                 NF_CT_DUMP_TUPLE(&exp->tuple);
  71
  72                 nf_nat_tftp = rcu_dereference(nf_nat_tftp_hook);
  73                 if (nf_nat_tftp && ct->status & IPS_NAT_MASK)
  74                         ret = nf_nat_tftp(skb, ctinfo, exp);
  75                 else if (nf_ct_expect_related(exp) != 0)
  76                         ret = NF_DROP;
  77                 nf_ct_expect_put(exp);
  78                 break;
  79         case TFTP_OPCODE_DATA:
  80         case TFTP_OPCODE_ACK:
  81                 pr_debug("Data/ACK opcode\n");
  82                 break;
  83         case TFTP_OPCODE_ERROR:
  84                 pr_debug("Error opcode\n");
  85                 break;
  86         default:
  87                 pr_debug("Unknown opcode\n");
  88         }
  89         return ret;
  90 }
  91
  92 static struct nf_conntrack_helper tftp[MAX_PORTS][2] __read_mostly;
  93 static char tftp_names[MAX_PORTS][2][sizeof("tftp-65535")] __read_mostly;
  94
  95 static void nf_conntrack_tftp_fini(void)
  96 {
  97         int i, j;
  98
  99         for (i = 0; i < ports_c; i++) {
 100                 for (j = 0; j < 2; j++)
 101                         nf_conntrack_helper_unregister(&tftp[i][j]);
 102         }
 103 }
 104
 105 static int __init nf_conntrack_tftp_init(void)
 106 {
 107         int i, j, ret;
 108         char *tmpname;
 109
 110         if (ports_c == 0)
 111                 ports[ports_c++] = TFTP_PORT;
 112
 113         for (i = 0; i < ports_c; i++) {
 114                 memset(&tftp[i], 0, sizeof(tftp[i]));
 115
 116                 tftp[i][0].tuple.src.l3num = AF_INET;
 117                 tftp[i][1].tuple.src.l3num = AF_INET6;
 118                 for (j = 0; j < 2; j++) {
 119                         tftp[i][j].tuple.dst.protonum = IPPROTO_UDP;
 120                         tftp[i][j].tuple.src.u.udp.port = htons(ports[i]);
 121                         tftp[i][j].max_expected = 1;
 122                         tftp[i][j].timeout = 5 * 60; /* 5 minutes */
 123                         tftp[i][j].me = THIS_MODULE;
 124                         tftp[i][j].help = tftp_help;
 125
 126                         tmpname = &tftp_names[i][j][0];
 127                         if (ports[i] == TFTP_PORT)
 128                                 sprintf(tmpname, "tftp");
 129                         else
 130                                 sprintf(tmpname, "tftp-%u", i);
 131                         tftp[i][j].name = tmpname;
 132
 133                         ret = nf_conntrack_helper_register(&tftp[i][j]);
 134                         if (ret) {
 135                                 printk("nf_ct_tftp: failed to register helper "
 136                                        "for pf: %u port: %u\n",
 137                                         tftp[i][j].tuple.src.l3num, ports[i]);
 138                                 nf_conntrack_tftp_fini();
 139                                 return ret;
 140                         }
 141                 }
 142         }
 143         return 0;
 144 }
 145
 146 module_init(nf_conntrack_tftp_init);
 147 module_exit(nf_conntrack_tftp_fini);