release/src/linux/linux/net/ipv4/netfilter/ip_nat_tftp.c

   1 /*
   2  * Licensed under GNU GPL version 2 Copyright Magnus Boden <mb@ozaba.mine.nu>
   3  * Version: 0.0.7
   4  *
   5  * Thu 21 Mar 2002 Harald Welte <laforge@gnumonks.org>
   6  *      - Port to newnat API
   7  *
   8  * This module currently supports DNAT:
   9  * iptables -t nat -A PREROUTING -d x.x.x.x -j DNAT --to-dest x.x.x.y
  10  *
  11  * and SNAT:
  12  * iptables -t nat -A POSTROUTING { -j MASQUERADE , -j SNAT --to-source x.x.x.x }
  13  *
  14  * It has not been tested with
  15  * -j SNAT --to-source x.x.x.x-x.x.x.y since I only have one external ip
  16  * If you do test this please let me know if it works or not.
  17  *
  18  */
  19
  20 #include <linux/module.h>
  21 #include <linux/netfilter_ipv4.h>
  22 #include <linux/ip.h>
  23 #include <linux/udp.h>
  24
  25 #include <linux/netfilter.h>
  26 #include <linux/netfilter_ipv4/ip_tables.h>
  27 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  28 #include <linux/netfilter_ipv4/ip_conntrack_tftp.h>
  29 #include <linux/netfilter_ipv4/ip_nat_helper.h>
  30 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  31
  32 MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
  33 MODULE_DESCRIPTION("Netfilter NAT helper for tftp");
  34 MODULE_LICENSE("GPL");
  35
  36 #define MAX_PORTS 8
  37
  38 static int ports[MAX_PORTS];
  39 static int ports_c = 0;
  40 #ifdef MODULE_PARM
  41 MODULE_PARM(ports,"1-" __MODULE_STRING(MAX_PORTS) "i");
  42 MODULE_PARM_DESC(ports, "port numbers of tftp servers");
  43 #endif
  44
  45 #define DEBUGP(format, args...)
  46 static unsigned int
  47 tftp_nat_help(struct ip_conntrack *ct,
  48               struct ip_conntrack_expect *exp,
  49               struct ip_nat_info *info,
  50               enum ip_conntrack_info ctinfo,
  51               unsigned int hooknum,
  52               struct sk_buff **pskb)
  53 {
  54         int dir = CTINFO2DIR(ctinfo);
  55         struct iphdr *iph = (*pskb)->nh.iph;
  56         struct udphdr *udph = (void *)iph + iph->ihl * 4;
  57         struct tftphdr *tftph = (void *)udph + 8;
  58         struct ip_conntrack_tuple repl;
  59
  60         if (!((hooknum == NF_IP_POST_ROUTING && dir == IP_CT_DIR_ORIGINAL)
  61               || (hooknum == NF_IP_PRE_ROUTING && dir == IP_CT_DIR_REPLY)))
  62                 return NF_ACCEPT;
  63
  64         if (!exp) {
  65                 DEBUGP("no conntrack expectation to modify\n");
  66                 return NF_ACCEPT;
  67         }
  68
  69         switch (ntohs(tftph->opcode)) {
  70         /* RRQ and WRQ works the same way */
  71         case TFTP_OPCODE_READ:
  72         case TFTP_OPCODE_WRITE:
  73                 repl = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  74                 DEBUGP("");
  75                 DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
  76                 DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  77                 DEBUGP("expecting: ");
  78                 DUMP_TUPLE_RAW(&repl);
  79                 DUMP_TUPLE_RAW(&exp->mask);
  80                 ip_conntrack_change_expect(exp, &repl);
  81                 break;
  82         default:
  83                 DEBUGP("Unknown opcode\n");
  84         }
  85
  86         return NF_ACCEPT;
  87 }
  88
  89 static unsigned int
  90 tftp_nat_expected(struct sk_buff **pskb,
  91                   unsigned int hooknum,
  92                   struct ip_conntrack *ct,
  93                   struct ip_nat_info *info)
  94 {
  95         const struct ip_conntrack *master = ct->master->expectant;
  96         const struct ip_conntrack_tuple *orig =
  97                         &master->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
  98         struct ip_nat_multi_range mr;
  99
 100         IP_NF_ASSERT(info);
 101         IP_NF_ASSERT(master);
 102         IP_NF_ASSERT(!(info->initialized & (1 << HOOK2MANIP(hooknum))));
 103
 104         mr.rangesize = 1;
 105         mr.range[0].flags = IP_NAT_RANGE_MAP_IPS;
 106
 107         if (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC) {
 108                 mr.range[0].min_ip = mr.range[0].max_ip = orig->dst.ip;
 109                 DEBUGP("orig: %u.%u.%u.%u:%u <-> %u.%u.%u.%u:%u "
 110                         "newsrc: %u.%u.%u.%u\n",
 111                         NIPQUAD((*pskb)->nh.iph->saddr), ntohs(udph->source),
 112                         NIPQUAD((*pskb)->nh.iph->daddr), ntohs(udph->dest),
 113                         NIPQUAD(orig->dst.ip));
 114         } else {
 115                 mr.range[0].min_ip = mr.range[0].max_ip = orig->src.ip;
 116                 mr.range[0].min.udp.port = mr.range[0].max.udp.port =
 117                                                         orig->src.u.udp.port;
 118                 mr.range[0].flags |= IP_NAT_RANGE_PROTO_SPECIFIED;
 119
 120                 DEBUGP("orig: %u.%u.%u.%u:%u <-> %u.%u.%u.%u:%u "
 121                         "newdst: %u.%u.%u.%u:%u\n",
 122                         NIPQUAD((*pskb)->nh.iph->saddr), ntohs(udph->source),
 123                         NIPQUAD((*pskb)->nh.iph->daddr), ntohs(udph->dest),
 124                         NIPQUAD(orig->src.ip), ntohs(orig->src.u.udp.port));
 125         }
 126
 127         return ip_nat_setup_info(ct,&mr,hooknum);
 128 }
 129
 130 static struct ip_nat_helper tftp[MAX_PORTS];
 131 static char tftp_names[MAX_PORTS][10];
 132
 133 static void fini(void)
 134 {
 135         int i;
 136
 137         for (i = 0 ; i < ports_c; i++) {
 138                 DEBUGP("unregistering helper for port %d\n", ports[i]);
 139                 ip_nat_helper_unregister(&tftp[i]);
 140         }
 141 }
 142
 143 static int __init init(void)
 144 {
 145         int i, ret;
 146         char *tmpname;
 147
 148         if (!ports[0])
 149                 ports[0] = TFTP_PORT;
 150
 151         for (i = 0 ; (i < MAX_PORTS) && ports[i] ; i++) {
 152                 memset(&tftp[i], 0, sizeof(struct ip_nat_helper));
 153
 154                 tftp[i].tuple.dst.protonum = IPPROTO_UDP;
 155                 tftp[i].tuple.src.u.udp.port = htons(ports[i]);
 156                 tftp[i].mask.dst.protonum = 0xFFFF;
 157                 tftp[i].mask.src.u.udp.port = 0xFFFF;
 158                 tftp[i].help = tftp_nat_help;
 159                 tftp[i].flags = 0;
 160                 tftp[i].me = THIS_MODULE;
 161                 tftp[i].expect = tftp_nat_expected;
 162
 163                 tmpname = &tftp_names[i][0];
 164                 if (ports[i] == TFTP_PORT)
 165                         sprintf(tmpname, "tftp");
 166                 else
 167                         sprintf(tmpname, "tftp-%d", i);
 168                 tftp[i].name = tmpname;
 169
 170                 DEBUGP("ip_nat_tftp: registering for port %d: name %s\n",
 171                         ports[i], tftp[i].name);
 172                 ret = ip_nat_helper_register(&tftp[i]);
 173
 174                 if (ret) {
 175                         printk("ip_nat_tftp: unable to register for port %d\n",
 176                                 ports[i]);
 177                         fini();
 178                         return ret;
 179                 }
 180                 ports_c++;
 181         }
 182         return ret;
 183 }
 184
 185 module_init(init);
 186 module_exit(fini);