net/ipv4/netfilter/ip_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  * Version: 0.0.7
   8  *
   9  * Thu 21 Mar 2002 Harald Welte <laforge@gnumonks.org>
  10  *      - port to newnat API
  11  *
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/ip.h>
  16 #include <linux/udp.h>
  17
  18 #include <linux/netfilter.h>
  19 #include <linux/netfilter_ipv4/ip_tables.h>
  20 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  21 #include <linux/netfilter_ipv4/ip_conntrack_tftp.h>
  22 #include <linux/moduleparam.h>
  23
  24 MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
  25 MODULE_DESCRIPTION("tftp connection tracking helper");
  26 MODULE_LICENSE("GPL");
  27
  28 #define MAX_PORTS 8
  29 static unsigned short ports[MAX_PORTS];
  30 static int ports_c;
  31 module_param_array(ports, ushort, &ports_c, 0400);
  32 MODULE_PARM_DESC(ports, "port numbers of tftp servers");
  33
  34 #if 0
  35 #define DEBUGP(format, args...) printk("%s:%s:" format, \
  36                                        __FILE__, __FUNCTION__ , ## args)
  37 #else
  38 #define DEBUGP(format, args...)
  39 #endif
  40
  41 unsigned int (*ip_nat_tftp_hook)(struct sk_buff **pskb,
  42                                  enum ip_conntrack_info ctinfo,
  43                                  struct ip_conntrack_expect *exp);
  44 EXPORT_SYMBOL_GPL(ip_nat_tftp_hook);
  45
  46 static int tftp_help(struct sk_buff **pskb,
  47                      struct ip_conntrack *ct,
  48                      enum ip_conntrack_info ctinfo)
  49 {
  50         struct tftphdr _tftph, *tfh;
  51         struct ip_conntrack_expect *exp;
  52         unsigned int ret = NF_ACCEPT;
  53
  54         tfh = skb_header_pointer(*pskb,
  55                                  (*pskb)->nh.iph->ihl*4+sizeof(struct udphdr),
  56                                  sizeof(_tftph), &_tftph);
  57         if (tfh == NULL)
  58                 return NF_ACCEPT;
  59
  60         switch (ntohs(tfh->opcode)) {
  61         /* RRQ and WRQ works the same way */
  62         case TFTP_OPCODE_READ:
  63         case TFTP_OPCODE_WRITE:
  64                 DEBUGP("");
  65                 DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
  66                 DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  67
  68                 exp = ip_conntrack_expect_alloc(ct);
  69                 if (exp == NULL)
  70                         return NF_DROP;
  71
  72                 exp->tuple = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  73                 exp->mask.src.ip = 0xffffffff;
  74                 exp->mask.dst.ip = 0xffffffff;
  75                 exp->mask.dst.u.udp.port = 0xffff;
  76                 exp->mask.dst.protonum = 0xff;
  77                 exp->expectfn = NULL;
  78                 exp->flags = 0;
  79
  80                 DEBUGP("expect: ");
  81                 DUMP_TUPLE(&exp->tuple);
  82                 DUMP_TUPLE(&exp->mask);
  83                 if (ip_nat_tftp_hook)
  84                         ret = ip_nat_tftp_hook(pskb, ctinfo, exp);
  85                 else if (ip_conntrack_expect_related(exp) != 0)
  86                         ret = NF_DROP;
  87                 ip_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 NF_ACCEPT;
 100 }
 101
 102 static struct ip_conntrack_helper tftp[MAX_PORTS];
 103 static char tftp_names[MAX_PORTS][sizeof("tftp-65535")];
 104
 105 static void fini(void)
 106 {
 107         int i;
 108
 109         for (i = 0 ; i < ports_c; i++) {
 110                 DEBUGP("unregistering helper for port %d\n",
 111                         ports[i]);
 112                 ip_conntrack_helper_unregister(&tftp[i]);
 113         }
 114 }
 115
 116 static int __init init(void)
 117 {
 118         int i, ret;
 119         char *tmpname;
 120
 121         if (ports_c == 0)
 122                 ports[ports_c++] = TFTP_PORT;
 123
 124         for (i = 0; i < ports_c; i++) {
 125                 /* Create helper structure */
 126                 memset(&tftp[i], 0, sizeof(struct ip_conntrack_helper));
 127
 128                 tftp[i].tuple.dst.protonum = IPPROTO_UDP;
 129                 tftp[i].tuple.src.u.udp.port = htons(ports[i]);
 130                 tftp[i].mask.dst.protonum = 0xFF;
 131                 tftp[i].mask.src.u.udp.port = 0xFFFF;
 132                 tftp[i].max_expected = 1;
 133                 tftp[i].timeout = 5 * 60; /* 5 minutes */
 134                 tftp[i].me = THIS_MODULE;
 135                 tftp[i].help = tftp_help;
 136
 137                 tmpname = &tftp_names[i][0];
 138                 if (ports[i] == TFTP_PORT)
 139                         sprintf(tmpname, "tftp");
 140                 else
 141                         sprintf(tmpname, "tftp-%d", i);
 142                 tftp[i].name = tmpname;
 143
 144                 DEBUGP("port #%d: %d\n", i, ports[i]);
 145
 146                 ret=ip_conntrack_helper_register(&tftp[i]);
 147                 if (ret) {
 148                         printk("ERROR registering helper for port %d\n",
 149                                 ports[i]);
 150                         fini();
 151                         return(ret);
 152                 }
 153         }
 154         return(0);
 155 }
 156
 157 module_init(init);
 158 module_exit(fini);