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