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 int ports[MAX_PORTS];
  30 static int ports_c;
  31 module_param_array(ports, int, &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();
  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->master = ct;
  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                         ip_conntrack_expect_free(exp);
  87                         ret = NF_DROP;
  88                 }
  89                 break;
  90         case TFTP_OPCODE_DATA:
  91         case TFTP_OPCODE_ACK:
  92                 DEBUGP("Data/ACK opcode\n");
  93                 break;
  94         case TFTP_OPCODE_ERROR:
  95                 DEBUGP("Error opcode\n");
  96                 break;
  97         default:
  98                 DEBUGP("Unknown opcode\n");
  99         }
 100         return NF_ACCEPT;
 101 }
 102
 103 static struct ip_conntrack_helper tftp[MAX_PORTS];
 104 static char tftp_names[MAX_PORTS][10];
 105
 106 static void fini(void)
 107 {
 108         int i;
 109
 110         for (i = 0 ; i < ports_c; i++) {
 111                 DEBUGP("unregistering helper for port %d\n",
 112                         ports[i]);
 113                 ip_conntrack_helper_unregister(&tftp[i]);
 114         }
 115 }
 116
 117 static int __init init(void)
 118 {
 119         int i, ret;
 120         char *tmpname;
 121
 122         if (ports_c == 0)
 123                 ports[ports_c++] = TFTP_PORT;
 124
 125         for (i = 0; i < ports_c; i++) {
 126                 /* Create helper structure */
 127                 memset(&tftp[i], 0, sizeof(struct ip_conntrack_helper));
 128
 129                 tftp[i].tuple.dst.protonum = IPPROTO_UDP;
 130                 tftp[i].tuple.src.u.udp.port = htons(ports[i]);
 131                 tftp[i].mask.dst.protonum = 0xFF;
 132                 tftp[i].mask.src.u.udp.port = 0xFFFF;
 133                 tftp[i].max_expected = 1;
 134                 tftp[i].timeout = 5 * 60; /* 5 minutes */
 135                 tftp[i].me = THIS_MODULE;
 136                 tftp[i].help = tftp_help;
 137
 138                 tmpname = &tftp_names[i][0];
 139                 if (ports[i] == TFTP_PORT)
 140                         sprintf(tmpname, "tftp");
 141                 else
 142                         sprintf(tmpname, "tftp-%d", i);
 143                 tftp[i].name = tmpname;
 144
 145                 DEBUGP("port #%d: %d\n", i, ports[i]);
 146
 147                 ret=ip_conntrack_helper_register(&tftp[i]);
 148                 if (ret) {
 149                         printk("ERROR registering helper for port %d\n",
 150                                 ports[i]);
 151                         fini();
 152                         return(ret);
 153                 }
 154         }
 155         return(0);
 156 }
 157
 158 module_init(init);
 159 module_exit(fini);