linux/net/netfilter/nf_conntrack_tftp.c
<<
>>
Prefs
   1/* (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu>
   2 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
   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
   8#include <linux/module.h>
   9#include <linux/moduleparam.h>
  10#include <linux/in.h>
  11#include <linux/udp.h>
  12#include <linux/netfilter.h>
  13
  14#include <net/netfilter/nf_conntrack.h>
  15#include <net/netfilter/nf_conntrack_tuple.h>
  16#include <net/netfilter/nf_conntrack_expect.h>
  17#include <net/netfilter/nf_conntrack_ecache.h>
  18#include <net/netfilter/nf_conntrack_helper.h>
  19#include <linux/netfilter/nf_conntrack_tftp.h>
  20
  21MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
  22MODULE_DESCRIPTION("TFTP connection tracking helper");
  23MODULE_LICENSE("GPL");
  24MODULE_ALIAS("ip_conntrack_tftp");
  25MODULE_ALIAS_NFCT_HELPER("tftp");
  26
  27#define MAX_PORTS 8
  28static unsigned short ports[MAX_PORTS];
  29static unsigned int ports_c;
  30module_param_array(ports, ushort, &ports_c, 0400);
  31MODULE_PARM_DESC(ports, "Port numbers of TFTP servers");
  32
  33unsigned int (*nf_nat_tftp_hook)(struct sk_buff *skb,
  34                                 enum ip_conntrack_info ctinfo,
  35                                 struct nf_conntrack_expect *exp) __read_mostly;
  36EXPORT_SYMBOL_GPL(nf_nat_tftp_hook);
  37
  38static int tftp_help(struct sk_buff *skb,
  39                     unsigned int protoff,
  40                     struct nf_conn *ct,
  41                     enum ip_conntrack_info ctinfo)
  42{
  43        const struct tftphdr *tfh;
  44        struct tftphdr _tftph;
  45        struct nf_conntrack_expect *exp;
  46        struct nf_conntrack_tuple *tuple;
  47        unsigned int ret = NF_ACCEPT;
  48        typeof(nf_nat_tftp_hook) nf_nat_tftp;
  49
  50        tfh = skb_header_pointer(skb, protoff + sizeof(struct udphdr),
  51                                 sizeof(_tftph), &_tftph);
  52        if (tfh == NULL)
  53                return NF_ACCEPT;
  54
  55        switch (ntohs(tfh->opcode)) {
  56        case TFTP_OPCODE_READ:
  57        case TFTP_OPCODE_WRITE:
  58                /* RRQ and WRQ works the same way */
  59                nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
  60                nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
  61
  62                exp = nf_ct_expect_alloc(ct);
  63                if (exp == NULL) {
  64                        nf_ct_helper_log(skb, ct, "cannot alloc expectation");
  65                        return NF_DROP;
  66                }
  67                tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  68                nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
  69                                  nf_ct_l3num(ct),
  70                                  &tuple->src.u3, &tuple->dst.u3,
  71                                  IPPROTO_UDP, NULL, &tuple->dst.u.udp.port);
  72
  73                pr_debug("expect: ");
  74                nf_ct_dump_tuple(&exp->tuple);
  75
  76                nf_nat_tftp = rcu_dereference(nf_nat_tftp_hook);
  77                if (nf_nat_tftp && ct->status & IPS_NAT_MASK)
  78                        ret = nf_nat_tftp(skb, ctinfo, exp);
  79                else if (nf_ct_expect_related(exp) != 0) {
  80                        nf_ct_helper_log(skb, ct, "cannot add expectation");
  81                        ret = NF_DROP;
  82                }
  83                nf_ct_expect_put(exp);
  84                break;
  85        case TFTP_OPCODE_DATA:
  86        case TFTP_OPCODE_ACK:
  87                pr_debug("Data/ACK opcode\n");
  88                break;
  89        case TFTP_OPCODE_ERROR:
  90                pr_debug("Error opcode\n");
  91                break;
  92        default:
  93                pr_debug("Unknown opcode\n");
  94        }
  95        return ret;
  96}
  97
  98static struct nf_conntrack_helper tftp[MAX_PORTS][2] __read_mostly;
  99
 100static const struct nf_conntrack_expect_policy tftp_exp_policy = {
 101        .max_expected   = 1,
 102        .timeout        = 5 * 60,
 103};
 104
 105static void nf_conntrack_tftp_fini(void)
 106{
 107        int i, j;
 108
 109        for (i = 0; i < ports_c; i++) {
 110                for (j = 0; j < 2; j++)
 111                        nf_conntrack_helper_unregister(&tftp[i][j]);
 112        }
 113}
 114
 115static int __init nf_conntrack_tftp_init(void)
 116{
 117        int i, j, ret;
 118
 119        if (ports_c == 0)
 120                ports[ports_c++] = TFTP_PORT;
 121
 122        for (i = 0; i < ports_c; i++) {
 123                memset(&tftp[i], 0, sizeof(tftp[i]));
 124
 125                tftp[i][0].tuple.src.l3num = AF_INET;
 126                tftp[i][1].tuple.src.l3num = AF_INET6;
 127                for (j = 0; j < 2; j++) {
 128                        tftp[i][j].tuple.dst.protonum = IPPROTO_UDP;
 129                        tftp[i][j].tuple.src.u.udp.port = htons(ports[i]);
 130                        tftp[i][j].expect_policy = &tftp_exp_policy;
 131                        tftp[i][j].me = THIS_MODULE;
 132                        tftp[i][j].help = tftp_help;
 133
 134                        if (ports[i] == TFTP_PORT)
 135                                sprintf(tftp[i][j].name, "tftp");
 136                        else
 137                                sprintf(tftp[i][j].name, "tftp-%u", i);
 138
 139                        ret = nf_conntrack_helper_register(&tftp[i][j]);
 140                        if (ret) {
 141                                printk(KERN_ERR "nf_ct_tftp: failed to register"
 142                                       " helper for pf: %u port: %u\n",
 143                                        tftp[i][j].tuple.src.l3num, ports[i]);
 144                                nf_conntrack_tftp_fini();
 145                                return ret;
 146                        }
 147                }
 148        }
 149        return 0;
 150}
 151
 152module_init(nf_conntrack_tftp_init);
 153module_exit(nf_conntrack_tftp_fini);
 154
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.