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Linux/net/netfilter/nf_conntrack_tftp.c

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  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 
 21 MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
 22 MODULE_DESCRIPTION("TFTP connection tracking helper");
 23 MODULE_LICENSE("GPL");
 24 MODULE_ALIAS("ip_conntrack_tftp");
 25 MODULE_ALIAS_NFCT_HELPER("tftp");
 26 
 27 #define MAX_PORTS 8
 28 static unsigned short ports[MAX_PORTS];
 29 static unsigned int ports_c;
 30 module_param_array(ports, ushort, &ports_c, 0400);
 31 MODULE_PARM_DESC(ports, "Port numbers of TFTP servers");
 32 
 33 unsigned int (*nf_nat_tftp_hook)(struct sk_buff *skb,
 34                                  enum ip_conntrack_info ctinfo,
 35                                  struct nf_conntrack_expect *exp) __read_mostly;
 36 EXPORT_SYMBOL_GPL(nf_nat_tftp_hook);
 37 
 38 static 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 
 98 static struct nf_conntrack_helper tftp[MAX_PORTS][2] __read_mostly;
 99 
100 static const struct nf_conntrack_expect_policy tftp_exp_policy = {
101         .max_expected   = 1,
102         .timeout        = 5 * 60,
103 };
104 
105 static 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 
115 static 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 
152 module_init(nf_conntrack_tftp_init);
153 module_exit(nf_conntrack_tftp_fini);
154 

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