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 int ports_c;
  29 module_param_array(ports, ushort, &ports_c, 0400);
  30 MODULE_PARM_DESC(ports, "Port numbers of TFTP servers");
  31
  32 #if 0
  33 #define DEBUGP(format, args...) printk("%s:%s:" format, \
  34                                        __FILE__, __FUNCTION__ , ## args)
  35 #else
  36 #define DEBUGP(format, args...)
  37 #endif
  38
  39 unsigned int (*nf_nat_tftp_hook)(struct sk_buff **pskb,
  40                                  enum ip_conntrack_info ctinfo,
  41                                  struct nf_conntrack_expect *exp) __read_mostly;
  42 EXPORT_SYMBOL_GPL(nf_nat_tftp_hook);
  43
  44 static int tftp_help(struct sk_buff **pskb,
  45                      unsigned int protoff,
  46                      struct nf_conn *ct,
  47                      enum ip_conntrack_info ctinfo)
  48 {
  49         struct tftphdr _tftph, *tfh;
  50         struct nf_conntrack_expect *exp;
  51         struct nf_conntrack_tuple *tuple;
  52         unsigned int ret = NF_ACCEPT;
  53         int family = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.l3num;
  54         typeof(nf_nat_tftp_hook) nf_nat_tftp;
  55
  56         tfh = skb_header_pointer(*pskb, protoff + sizeof(struct udphdr),
  57                                  sizeof(_tftph), &_tftph);
  58         if (tfh == NULL)
  59                 return NF_ACCEPT;
  60
  61         switch (ntohs(tfh->opcode)) {
  62         case TFTP_OPCODE_READ:
  63         case TFTP_OPCODE_WRITE:
  64                 /* RRQ and WRQ works the same way */
  65                 DEBUGP("");
  66                 NF_CT_DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
  67                 NF_CT_DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  68
  69                 exp = nf_conntrack_expect_alloc(ct);
  70                 if (exp == NULL)
  71                         return NF_DROP;
  72                 tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  73                 nf_conntrack_expect_init(exp, family,
  74                                          &tuple->src.u3, &tuple->dst.u3,
  75                                          IPPROTO_UDP,
  76                                          NULL, &tuple->dst.u.udp.port);
  77
  78                 DEBUGP("expect: ");
  79                 NF_CT_DUMP_TUPLE(&exp->tuple);
  80                 NF_CT_DUMP_TUPLE(&exp->mask);
  81
  82                 nf_nat_tftp = rcu_dereference(nf_nat_tftp_hook);
  83                 if (nf_nat_tftp && ct->status & IPS_NAT_MASK)
  84                         ret = nf_nat_tftp(pskb, ctinfo, exp);
  85                 else if (nf_conntrack_expect_related(exp) != 0)
  86                         ret = NF_DROP;
  87                 nf_conntrack_expect_put(exp);
  88                 break;
  89         case TFTP_OPCODE_DATA:
  90         case TFTP_OPCODE_ACK:
  91                 DEBUGP("Data/ACK opcode\n");
  92                 break;
  93         case TFTP_OPCODE_ERROR:
  94                 DEBUGP("Error opcode\n");
  95                 break;
  96         default:
  97                 DEBUGP("Unknown opcode\n");
  98         }
  99         return ret;
 100 }
 101
 102 static struct nf_conntrack_helper tftp[MAX_PORTS][2] __read_mostly;
 103 static char tftp_names[MAX_PORTS][2][sizeof("tftp-65535")] __read_mostly;
 104
 105 static void nf_conntrack_tftp_fini(void)
 106 {
 107         int i, j;
 108
 109         for (i = 0; i < ports_c; i++) {
 110                 for (j = 0; j < 2; j++)
 111                         nf_conntrack_helper_unregister(&tftp[i][j]);
 112         }
 113 }
 114
 115 static int __init nf_conntrack_tftp_init(void)
 116 {
 117         int i, j, ret;
 118         char *tmpname;
 119
 120         if (ports_c == 0)
 121                 ports[ports_c++] = TFTP_PORT;
 122
 123         for (i = 0; i < ports_c; i++) {
 124                 memset(&tftp[i], 0, sizeof(tftp[i]));
 125
 126                 tftp[i][0].tuple.src.l3num = AF_INET;
 127                 tftp[i][1].tuple.src.l3num = AF_INET6;
 128                 for (j = 0; j < 2; j++) {
 129                         tftp[i][j].tuple.dst.protonum = IPPROTO_UDP;
 130                         tftp[i][j].tuple.src.u.udp.port = htons(ports[i]);
 131                         tftp[i][j].mask.src.l3num = 0xFFFF;
 132                         tftp[i][j].mask.dst.protonum = 0xFF;
 133                         tftp[i][j].mask.src.u.udp.port = htons(0xFFFF);
 134                         tftp[i][j].max_expected = 1;
 135                         tftp[i][j].timeout = 5 * 60; /* 5 minutes */
 136                         tftp[i][j].me = THIS_MODULE;
 137                         tftp[i][j].help = tftp_help;
 138
 139                         tmpname = &tftp_names[i][j][0];
 140                         if (ports[i] == TFTP_PORT)
 141                                 sprintf(tmpname, "tftp");
 142                         else
 143                                 sprintf(tmpname, "tftp-%u", i);
 144                         tftp[i][j].name = tmpname;
 145
 146                         ret = nf_conntrack_helper_register(&tftp[i][j]);
 147                         if (ret) {
 148                                 printk("nf_ct_tftp: failed to register helper "
 149                                        "for pf: %u port: %u\n",
 150                                         tftp[i][j].tuple.src.l3num, ports[i]);
 151                                 nf_conntrack_tftp_fini();
 152                                 return ret;
 153                         }
 154                 }
 155         }
 156         return 0;
 157 }
 158
 159 module_init(nf_conntrack_tftp_init);
 160 module_exit(nf_conntrack_tftp_fini);