net/ipv4/netfilter/ip_conntrack_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  */
   9
  10 #include <linux/module.h>
  11 #include <linux/ip.h>
  12 #include <linux/udp.h>
  13
  14 #include <linux/netfilter.h>
  15 #include <linux/netfilter_ipv4/ip_tables.h>
  16 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  17 #include <linux/netfilter_ipv4/ip_conntrack_tftp.h>
  18
  19 MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
  20 MODULE_DESCRIPTION("Netfilter connection tracking module for tftp");
  21 MODULE_LICENSE("GPL");
  22
  23 #define MAX_PORTS 8
  24 static int ports[MAX_PORTS];
  25 static int ports_c = 0;
  26 #ifdef MODULE_PARM
  27 MODULE_PARM(ports, "1-" __MODULE_STRING(MAX_PORTS) "i");
  28 MODULE_PARM_DESC(ports, "port numbers of tftp servers");
  29 #endif
  30
  31 #if 0
  32 #define DEBUGP(format, args...) printk(__FILE__ ":" __FUNCTION__ ": " \
  33                                        format, ## args)
  34 #else
  35 #define DEBUGP(format, args...)
  36 #endif
  37
  38 static int tftp_help(struct sk_buff *skb,
  39                      struct ip_conntrack *ct,
  40                      enum ip_conntrack_info ctinfo)
  41 {
  42         struct tftphdr tftph;
  43         struct ip_conntrack_expect exp;
  44
  45         if (skb_copy_bits(skb, skb->nh.iph->ihl * 4 + sizeof(struct udphdr),
  46                           &tftph, sizeof(tftph)) != 0)
  47                 return -1;
  48
  49         switch (ntohs(tftph.opcode)) {
  50         /* RRQ and WRQ works the same way */
  51         case TFTP_OPCODE_READ:
  52         case TFTP_OPCODE_WRITE:
  53                 DEBUGP("");
  54                 DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
  55                 DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  56                 memset(&exp, 0, sizeof(exp));
  57
  58                 exp.tuple = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  59                 exp.mask.src.ip = 0xffffffff;
  60                 exp.mask.dst.ip = 0xffffffff;
  61                 exp.mask.dst.u.udp.port = 0xffff;
  62                 exp.mask.dst.protonum = 0xffff;
  63                 exp.expectfn = NULL;
  64
  65                 DEBUGP("expect: ");
  66                 DUMP_TUPLE(&exp.tuple);
  67                 DUMP_TUPLE(&exp.mask);
  68                 ip_conntrack_expect_related(ct, &exp);
  69                 break;
  70         default:
  71                 DEBUGP("Unknown opcode\n");
  72         }
  73         return NF_ACCEPT;
  74 }
  75
  76 static struct ip_conntrack_helper tftp[MAX_PORTS];
  77 static char tftp_names[MAX_PORTS][10];
  78
  79 static void fini(void)
  80 {
  81         int i;
  82
  83         for (i = 0 ; i < ports_c; i++) {
  84                 DEBUGP("unregistering helper for port %d\n",
  85                         ports[i]);
  86                 ip_conntrack_helper_unregister(&tftp[i]);
  87         }
  88 }
  89
  90 static int __init init(void)
  91 {
  92         int i, ret;
  93         char *tmpname;
  94
  95         if (!ports[0])
  96                 ports[0]=TFTP_PORT;
  97
  98         for (i = 0 ; (i < MAX_PORTS) && ports[i] ; i++) {
  99                 /* Create helper structure */
 100                 memset(&tftp[i], 0, sizeof(struct ip_conntrack_helper));
 101
 102                 tftp[i].tuple.dst.protonum = IPPROTO_UDP;
 103                 tftp[i].tuple.src.u.udp.port = htons(ports[i]);
 104                 tftp[i].mask.dst.protonum = 0xFFFF;
 105                 tftp[i].mask.src.u.udp.port = 0xFFFF;
 106                 tftp[i].max_expected = 1;
 107                 tftp[i].timeout = 0;
 108                 tftp[i].flags = IP_CT_HELPER_F_REUSE_EXPECT;
 109                 tftp[i].me = THIS_MODULE;
 110                 tftp[i].help = tftp_help;
 111
 112                 tmpname = &tftp_names[i][0];
 113                 if (ports[i] == TFTP_PORT)
 114                         sprintf(tmpname, "tftp");
 115                 else
 116                         sprintf(tmpname, "tftp-%d", i);
 117                 tftp[i].name = tmpname;
 118
 119                 DEBUGP("port #%d: %d\n", i, ports[i]);
 120
 121                 ret=ip_conntrack_helper_register(&tftp[i]);
 122                 if (ret) {
 123                         printk("ERROR registering helper for port %d\n",
 124                                 ports[i]);
 125                         fini();
 126                         return(ret);
 127                 }
 128                 ports_c++;
 129         }
 130         return(0);
 131 }
 132
 133 PROVIDES_CONNTRACK(tftp);
 134
 135 module_init(init);
 136 module_exit(fini);