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
  23 MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
  24 MODULE_DESCRIPTION("tftp connection tracking helper");
  25 MODULE_LICENSE("GPL");
  26
  27 #define MAX_PORTS 8
  28 static int ports[MAX_PORTS];
  29 static int ports_c;
  30 #ifdef MODULE_PARM
  31 MODULE_PARM(ports, "1-" __MODULE_STRING(MAX_PORTS) "i");
  32 MODULE_PARM_DESC(ports, "port numbers of tftp servers");
  33 #endif
  34
  35 #if 0
  36 #define DEBUGP(format, args...) printk("%s:%s:" format, \
  37                                        __FILE__, __FUNCTION__ , ## args)
  38 #else
  39 #define DEBUGP(format, args...)
  40 #endif
  41
  42 static int tftp_help(struct sk_buff *skb,
  43                      struct ip_conntrack *ct,
  44                      enum ip_conntrack_info ctinfo)
  45 {
  46         struct tftphdr tftph;
  47         struct ip_conntrack_expect *exp;
  48
  49         if (skb_copy_bits(skb, skb->nh.iph->ihl * 4 + sizeof(struct udphdr),
  50                           &tftph, sizeof(tftph)) != 0)
  51                 return NF_ACCEPT;
  52
  53         switch (ntohs(tftph.opcode)) {
  54         /* RRQ and WRQ works the same way */
  55         case TFTP_OPCODE_READ:
  56         case TFTP_OPCODE_WRITE:
  57                 DEBUGP("");
  58                 DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
  59                 DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  60
  61                 exp = ip_conntrack_expect_alloc();
  62                 if (exp == NULL)
  63                         return NF_ACCEPT;
  64
  65                 exp->tuple = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  66                 exp->mask.src.ip = 0xffffffff;
  67                 exp->mask.dst.ip = 0xffffffff;
  68                 exp->mask.dst.u.udp.port = 0xffff;
  69                 exp->mask.dst.protonum = 0xffff;
  70                 exp->expectfn = NULL;
  71
  72                 DEBUGP("expect: ");
  73                 DUMP_TUPLE(&exp->tuple);
  74                 DUMP_TUPLE(&exp->mask);
  75                 ip_conntrack_expect_related(exp, ct);
  76                 break;
  77         case TFTP_OPCODE_DATA:
  78         case TFTP_OPCODE_ACK:
  79                 DEBUGP("Data/ACK opcode\n");
  80                 break;
  81         case TFTP_OPCODE_ERROR:
  82                 DEBUGP("Error opcode\n");
  83                 break;
  84         default:
  85                 DEBUGP("Unknown opcode\n");
  86         }
  87         return NF_ACCEPT;
  88 }
  89
  90 static struct ip_conntrack_helper tftp[MAX_PORTS];
  91 static char tftp_names[MAX_PORTS][10];
  92
  93 static void fini(void)
  94 {
  95         int i;
  96
  97         for (i = 0 ; i < ports_c; i++) {
  98                 DEBUGP("unregistering helper for port %d\n",
  99                         ports[i]);
 100                 ip_conntrack_helper_unregister(&tftp[i]);
 101         }
 102 }
 103
 104 static int __init init(void)
 105 {
 106         int i, ret;
 107         char *tmpname;
 108
 109         if (!ports[0])
 110                 ports[0]=TFTP_PORT;
 111
 112         for (i = 0 ; (i < MAX_PORTS) && ports[i] ; i++) {
 113                 /* Create helper structure */
 114                 memset(&tftp[i], 0, sizeof(struct ip_conntrack_helper));
 115
 116                 tftp[i].tuple.dst.protonum = IPPROTO_UDP;
 117                 tftp[i].tuple.src.u.udp.port = htons(ports[i]);
 118                 tftp[i].mask.dst.protonum = 0xFFFF;
 119                 tftp[i].mask.src.u.udp.port = 0xFFFF;
 120                 tftp[i].max_expected = 1;
 121                 tftp[i].timeout = 0;
 122                 tftp[i].flags = IP_CT_HELPER_F_REUSE_EXPECT;
 123                 tftp[i].me = THIS_MODULE;
 124                 tftp[i].help = tftp_help;
 125
 126                 tmpname = &tftp_names[i][0];
 127                 if (ports[i] == TFTP_PORT)
 128                         sprintf(tmpname, "tftp");
 129                 else
 130                         sprintf(tmpname, "tftp-%d", i);
 131                 tftp[i].name = tmpname;
 132
 133                 DEBUGP("port #%d: %d\n", i, ports[i]);
 134
 135                 ret=ip_conntrack_helper_register(&tftp[i]);
 136                 if (ret) {
 137                         printk("ERROR registering helper for port %d\n",
 138                                 ports[i]);
 139                         fini();
 140                         return(ret);
 141                 }
 142                 ports_c++;
 143         }
 144         return(0);
 145 }
 146
 147 PROVIDES_CONNTRACK(tftp);
 148
 149 module_init(init);
 150 module_exit(fini);