net/netfilter/nf_conntrack_amanda.c

   1 /* Amanda extension for IP connection tracking
   2  *
   3  * (C) 2002 by Brian J. Murrell <netfilter@interlinx.bc.ca>
   4  * based on HW's ip_conntrack_irc.c as well as other modules
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11 #include <linux/kernel.h>
  12 #include <linux/module.h>
  13 #include <linux/moduleparam.h>
  14 #include <linux/textsearch.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/in.h>
  17 #include <linux/udp.h>
  18 #include <linux/netfilter.h>
  19
  20 #include <net/netfilter/nf_conntrack.h>
  21 #include <net/netfilter/nf_conntrack_expect.h>
  22 #include <net/netfilter/nf_conntrack_ecache.h>
  23 #include <net/netfilter/nf_conntrack_helper.h>
  24 #include <linux/netfilter/nf_conntrack_amanda.h>
  25
  26 static unsigned int master_timeout __read_mostly = 300;
  27 static char *ts_algo = "kmp";
  28
  29 MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
  30 MODULE_DESCRIPTION("Amanda connection tracking module");
  31 MODULE_LICENSE("GPL");
  32 MODULE_ALIAS("ip_conntrack_amanda");
  33
  34 module_param(master_timeout, uint, 0600);
  35 MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
  36 module_param(ts_algo, charp, 0400);
  37 MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
  38
  39 unsigned int (*nf_nat_amanda_hook)(struct sk_buff *skb,
  40                                    enum ip_conntrack_info ctinfo,
  41                                    unsigned int matchoff,
  42                                    unsigned int matchlen,
  43                                    struct nf_conntrack_expect *exp)
  44                                    __read_mostly;
  45 EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
  46
  47 enum amanda_strings {
  48         SEARCH_CONNECT,
  49         SEARCH_NEWLINE,
  50         SEARCH_DATA,
  51         SEARCH_MESG,
  52         SEARCH_INDEX,
  53 };
  54
  55 static struct {
  56         const char              *string;
  57         size_t                  len;
  58         struct ts_config        *ts;
  59 } search[] __read_mostly = {
  60         [SEARCH_CONNECT] = {
  61                 .string = "CONNECT ",
  62                 .len    = 8,
  63         },
  64         [SEARCH_NEWLINE] = {
  65                 .string = "\n",
  66                 .len    = 1,
  67         },
  68         [SEARCH_DATA] = {
  69                 .string = "DATA ",
  70                 .len    = 5,
  71         },
  72         [SEARCH_MESG] = {
  73                 .string = "MESG ",
  74                 .len    = 5,
  75         },
  76         [SEARCH_INDEX] = {
  77                 .string = "INDEX ",
  78                 .len    = 6,
  79         },
  80 };
  81
  82 static int amanda_help(struct sk_buff *skb,
  83                        unsigned int protoff,
  84                        struct nf_conn *ct,
  85                        enum ip_conntrack_info ctinfo)
  86 {
  87         struct ts_state ts;
  88         struct nf_conntrack_expect *exp;
  89         struct nf_conntrack_tuple *tuple;
  90         unsigned int dataoff, start, stop, off, i;
  91         char pbuf[sizeof("65535")], *tmp;
  92         u_int16_t len;
  93         __be16 port;
  94         int ret = NF_ACCEPT;
  95         typeof(nf_nat_amanda_hook) nf_nat_amanda;
  96
  97         /* Only look at packets from the Amanda server */
  98         if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL)
  99                 return NF_ACCEPT;
 100
 101         /* increase the UDP timeout of the master connection as replies from
 102          * Amanda clients to the server can be quite delayed */
 103         nf_ct_refresh(ct, skb, master_timeout * HZ);
 104
 105         /* No data? */
 106         dataoff = protoff + sizeof(struct udphdr);
 107         if (dataoff >= skb->len) {
 108                 if (net_ratelimit())
 109                         printk("amanda_help: skblen = %u\n", skb->len);
 110                 return NF_ACCEPT;
 111         }
 112
 113         memset(&ts, 0, sizeof(ts));
 114         start = skb_find_text(skb, dataoff, skb->len,
 115                               search[SEARCH_CONNECT].ts, &ts);
 116         if (start == UINT_MAX)
 117                 goto out;
 118         start += dataoff + search[SEARCH_CONNECT].len;
 119
 120         memset(&ts, 0, sizeof(ts));
 121         stop = skb_find_text(skb, start, skb->len,
 122                              search[SEARCH_NEWLINE].ts, &ts);
 123         if (stop == UINT_MAX)
 124                 goto out;
 125         stop += start;
 126
 127         for (i = SEARCH_DATA; i <= SEARCH_INDEX; i++) {
 128                 memset(&ts, 0, sizeof(ts));
 129                 off = skb_find_text(skb, start, stop, search[i].ts, &ts);
 130                 if (off == UINT_MAX)
 131                         continue;
 132                 off += start + search[i].len;
 133
 134                 len = min_t(unsigned int, sizeof(pbuf) - 1, stop - off);
 135                 if (skb_copy_bits(skb, off, pbuf, len))
 136                         break;
 137                 pbuf[len] = '\0';
 138
 139                 port = htons(simple_strtoul(pbuf, &tmp, 10));
 140                 len = tmp - pbuf;
 141                 if (port == 0 || len > 5)
 142                         break;
 143
 144                 exp = nf_ct_expect_alloc(ct);
 145                 if (exp == NULL) {
 146                         ret = NF_DROP;
 147                         goto out;
 148                 }
 149                 tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 150                 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
 151                                   nf_ct_l3num(ct),
 152                                   &tuple->src.u3, &tuple->dst.u3,
 153                                   IPPROTO_TCP, NULL, &port);
 154
 155                 nf_nat_amanda = rcu_dereference(nf_nat_amanda_hook);
 156                 if (nf_nat_amanda && ct->status & IPS_NAT_MASK)
 157                         ret = nf_nat_amanda(skb, ctinfo, off - dataoff,
 158                                             len, exp);
 159                 else if (nf_ct_expect_related(exp) != 0)
 160                         ret = NF_DROP;
 161                 nf_ct_expect_put(exp);
 162         }
 163
 164 out:
 165         return ret;
 166 }
 167
 168 static const struct nf_conntrack_expect_policy amanda_exp_policy = {
 169         .max_expected           = 3,
 170         .timeout                = 180,
 171 };
 172
 173 static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
 174         {
 175                 .name                   = "amanda",
 176                 .me                     = THIS_MODULE,
 177                 .help                   = amanda_help,
 178                 .tuple.src.l3num        = AF_INET,
 179                 .tuple.src.u.udp.port   = __constant_htons(10080),
 180                 .tuple.dst.protonum     = IPPROTO_UDP,
 181                 .expect_policy          = &amanda_exp_policy,
 182         },
 183         {
 184                 .name                   = "amanda",
 185                 .me                     = THIS_MODULE,
 186                 .help                   = amanda_help,
 187                 .tuple.src.l3num        = AF_INET6,
 188                 .tuple.src.u.udp.port   = __constant_htons(10080),
 189                 .tuple.dst.protonum     = IPPROTO_UDP,
 190                 .expect_policy          = &amanda_exp_policy,
 191         },
 192 };
 193
 194 static void __exit nf_conntrack_amanda_fini(void)
 195 {
 196         int i;
 197
 198         nf_conntrack_helper_unregister(&amanda_helper[0]);
 199         nf_conntrack_helper_unregister(&amanda_helper[1]);
 200         for (i = 0; i < ARRAY_SIZE(search); i++)
 201                 textsearch_destroy(search[i].ts);
 202 }
 203
 204 static int __init nf_conntrack_amanda_init(void)
 205 {
 206         int ret, i;
 207
 208         for (i = 0; i < ARRAY_SIZE(search); i++) {
 209                 search[i].ts = textsearch_prepare(ts_algo, search[i].string,
 210                                                   search[i].len,
 211                                                   GFP_KERNEL, TS_AUTOLOAD);
 212                 if (IS_ERR(search[i].ts)) {
 213                         ret = PTR_ERR(search[i].ts);
 214                         goto err1;
 215                 }
 216         }
 217         ret = nf_conntrack_helper_register(&amanda_helper[0]);
 218         if (ret < 0)
 219                 goto err1;
 220         ret = nf_conntrack_helper_register(&amanda_helper[1]);
 221         if (ret < 0)
 222                 goto err2;
 223         return 0;
 224
 225 err2:
 226         nf_conntrack_helper_unregister(&amanda_helper[0]);
 227 err1:
 228         while (--i >= 0)
 229                 textsearch_destroy(search[i].ts);
 230
 231         return ret;
 232 }
 233
 234 module_init(nf_conntrack_amanda_init);
 235 module_exit(nf_conntrack_amanda_fini);