net/ipv4/netfilter/ip_nat_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  * This module currently supports DNAT:
  13  * iptables -t nat -A PREROUTING -d x.x.x.x -j DNAT --to-dest x.x.x.y
  14  *
  15  * and SNAT:
  16  * iptables -t nat -A POSTROUTING { -j MASQUERADE , -j SNAT --to-source x.x.x.x }
  17  *
  18  * It has not been tested with
  19  * -j SNAT --to-source x.x.x.x-x.x.x.y since I only have one external ip
  20  * If you do test this please let me know if it works or not.
  21  *
  22  */
  23
  24 #include <linux/module.h>
  25 #include <linux/netfilter_ipv4.h>
  26 #include <linux/ip.h>
  27 #include <linux/udp.h>
  28
  29 #include <linux/netfilter.h>
  30 #include <linux/netfilter_ipv4/ip_tables.h>
  31 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  32 #include <linux/netfilter_ipv4/ip_conntrack_tftp.h>
  33 #include <linux/netfilter_ipv4/ip_nat_helper.h>
  34 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  35 #include <linux/moduleparam.h>
  36
  37 MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
  38 MODULE_DESCRIPTION("tftp NAT helper");
  39 MODULE_LICENSE("GPL");
  40
  41 #define MAX_PORTS 8
  42
  43 static int ports[MAX_PORTS];
  44 static int ports_c = 0;
  45 module_param_array(ports, int, ports_c, 0400);
  46 MODULE_PARM_DESC(ports, "port numbers of tftp servers");
  47
  48 #if 0
  49 #define DEBUGP(format, args...) printk("%s:%s:" format, \
  50                                        __FILE__, __FUNCTION__ , ## args)
  51 #else
  52 #define DEBUGP(format, args...)
  53 #endif
  54 static unsigned int
  55 tftp_nat_help(struct ip_conntrack *ct,
  56               struct ip_conntrack_expect *exp,
  57               struct ip_nat_info *info,
  58               enum ip_conntrack_info ctinfo,
  59               unsigned int hooknum,
  60               struct sk_buff **pskb)
  61 {
  62         int dir = CTINFO2DIR(ctinfo);
  63         struct tftphdr _tftph, *tfh;
  64         struct ip_conntrack_tuple repl;
  65
  66         if (!((hooknum == NF_IP_POST_ROUTING && dir == IP_CT_DIR_ORIGINAL)
  67               || (hooknum == NF_IP_PRE_ROUTING && dir == IP_CT_DIR_REPLY)))
  68                 return NF_ACCEPT;
  69
  70         if (!exp) {
  71                 DEBUGP("no conntrack expectation to modify\n");
  72                 return NF_ACCEPT;
  73         }
  74
  75         tfh = skb_header_pointer(*pskb,
  76                                  (*pskb)->nh.iph->ihl*4+sizeof(struct udphdr),
  77                                  sizeof(_tftph), &_tftph);
  78         if (tfh == NULL)
  79                 return NF_DROP;
  80
  81         switch (ntohs(tfh->opcode)) {
  82         /* RRQ and WRQ works the same way */
  83         case TFTP_OPCODE_READ:
  84         case TFTP_OPCODE_WRITE:
  85                 repl = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  86                 DEBUGP("");
  87                 DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
  88                 DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  89                 DEBUGP("expecting: ");
  90                 DUMP_TUPLE(&repl);
  91                 DUMP_TUPLE(&exp->mask);
  92                 ip_conntrack_change_expect(exp, &repl);
  93                 break;
  94         default:
  95                 DEBUGP("Unknown opcode\n");
  96         }
  97
  98         return NF_ACCEPT;
  99 }
 100
 101 static unsigned int
 102 tftp_nat_expected(struct sk_buff **pskb,
 103                   unsigned int hooknum,
 104                   struct ip_conntrack *ct,
 105                   struct ip_nat_info *info)
 106 {
 107         const struct ip_conntrack *master = ct->master->expectant;
 108         const struct ip_conntrack_tuple *orig =
 109                         &master->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 110         struct ip_nat_multi_range mr;
 111 #if 0
 112         const struct ip_conntrack_tuple *repl =
 113                         &master->tuplehash[IP_CT_DIR_REPLY].tuple;
 114         struct udphdr _udph, *uh;
 115
 116         uh = skb_header_pointer(*pskb,
 117                                 (*pskb)->nh.iph->ihl*4,
 118                                 sizeof(_udph), &_udph);
 119         if (uh == NULL)
 120                 return NF_DROP;
 121 #endif
 122
 123         IP_NF_ASSERT(info);
 124         IP_NF_ASSERT(master);
 125         IP_NF_ASSERT(!(info->initialized & (1 << HOOK2MANIP(hooknum))));
 126
 127         mr.rangesize = 1;
 128         mr.range[0].flags = IP_NAT_RANGE_MAP_IPS;
 129
 130         if (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC) {
 131                 mr.range[0].min_ip = mr.range[0].max_ip = orig->dst.ip;
 132                 DEBUGP("orig: %u.%u.%u.%u:%u <-> %u.%u.%u.%u:%u "
 133                         "newsrc: %u.%u.%u.%u\n",
 134                         NIPQUAD((*pskb)->nh.iph->saddr), ntohs(uh->source),
 135                         NIPQUAD((*pskb)->nh.iph->daddr), ntohs(uh->dest),
 136                         NIPQUAD(orig->dst.ip));
 137         } else {
 138                 mr.range[0].min_ip = mr.range[0].max_ip = orig->src.ip;
 139                 mr.range[0].min.udp.port = mr.range[0].max.udp.port =
 140                                                         orig->src.u.udp.port;
 141                 mr.range[0].flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
 142
 143                 DEBUGP("orig: %u.%u.%u.%u:%u <-> %u.%u.%u.%u:%u "
 144                         "newdst: %u.%u.%u.%u:%u\n",
 145                         NIPQUAD((*pskb)->nh.iph->saddr), ntohs(uh->source),
 146                         NIPQUAD((*pskb)->nh.iph->daddr), ntohs(uh->dest),
 147                         NIPQUAD(orig->src.ip), ntohs(orig->src.u.udp.port));
 148         }
 149
 150         return ip_nat_setup_info(ct,&mr,hooknum);
 151 }
 152
 153 static struct ip_nat_helper tftp[MAX_PORTS];
 154 static char tftp_names[MAX_PORTS][10];
 155
 156 static void fini(void)
 157 {
 158         int i;
 159
 160         for (i = 0 ; i < ports_c; i++) {
 161                 DEBUGP("unregistering helper for port %d\n", ports[i]);
 162                 ip_nat_helper_unregister(&tftp[i]);
 163         }
 164 }
 165
 166 static int __init init(void)
 167 {
 168         int i, ret = 0;
 169         char *tmpname;
 170
 171         if (ports_c == 0)
 172                 ports[ports_c++] = TFTP_PORT;
 173
 174         for (i = 0; i < ports_c; i++) {
 175                 memset(&tftp[i], 0, sizeof(struct ip_nat_helper));
 176
 177                 tftp[i].tuple.dst.protonum = IPPROTO_UDP;
 178                 tftp[i].tuple.src.u.udp.port = htons(ports[i]);
 179                 tftp[i].mask.dst.protonum = 0xFFFF;
 180                 tftp[i].mask.src.u.udp.port = 0xFFFF;
 181                 tftp[i].help = tftp_nat_help;
 182                 tftp[i].flags = 0;
 183                 tftp[i].me = THIS_MODULE;
 184                 tftp[i].expect = tftp_nat_expected;
 185
 186                 tmpname = &tftp_names[i][0];
 187                 if (ports[i] == TFTP_PORT)
 188                         sprintf(tmpname, "tftp");
 189                 else
 190                         sprintf(tmpname, "tftp-%d", i);
 191                 tftp[i].name = tmpname;
 192
 193                 DEBUGP("ip_nat_tftp: registering for port %d: name %s\n",
 194                         ports[i], tftp[i].name);
 195                 ret = ip_nat_helper_register(&tftp[i]);
 196
 197                 if (ret) {
 198                         printk("ip_nat_tftp: unable to register for port %d\n",
 199                                 ports[i]);
 200                         fini();
 201                         return ret;
 202                 }
 203         }
 204         return ret;
 205 }
 206
 207 module_init(init);
 208 module_exit(fini);