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 MODULE_ALIAS_NFCT_HELPER("amanda");
  34
  35 module_param(master_timeout, uint, 0600);
  36 MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
  37 module_param(ts_algo, charp, 0400);
  38 MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
  39
  40 unsigned int (*nf_nat_amanda_hook)(struct sk_buff *skb,
  41                                    enum ip_conntrack_info ctinfo,
  42                                    unsigned int matchoff,
  43                                    unsigned int matchlen,
  44                                    struct nf_conntrack_expect *exp)
  45                                    __read_mostly;
  46 EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
  47
  48 enum amanda_strings {
  49         SEARCH_CONNECT,
  50         SEARCH_NEWLINE,
  51         SEARCH_DATA,
  52         SEARCH_MESG,
  53         SEARCH_INDEX,
  54 };
  55
  56 static struct {
  57         const char              *string;
  58         size_t                  len;
  59         struct ts_config        *ts;
  60 } search[] __read_mostly = {
  61         [SEARCH_CONNECT] = {
  62                 .string = "CONNECT ",
  63                 .len    = 8,
  64         },
  65         [SEARCH_NEWLINE] = {
  66                 .string = "\n",
  67                 .len    = 1,
  68         },
  69         [SEARCH_DATA] = {
  70                 .string = "DATA ",
  71                 .len    = 5,
  72         },
  73         [SEARCH_MESG] = {
  74                 .string = "MESG ",
  75                 .len    = 5,
  76         },
  77         [SEARCH_INDEX] = {
  78                 .string = "INDEX ",
  79                 .len    = 6,
  80         },
  81 };
  82
  83 static int amanda_help(struct sk_buff *skb,
  84                        unsigned int protoff,
  85                        struct nf_conn *ct,
  86                        enum ip_conntrack_info ctinfo)
  87 {
  88         struct ts_state ts;
  89         struct nf_conntrack_expect *exp;
  90         struct nf_conntrack_tuple *tuple;
  91         unsigned int dataoff, start, stop, off, i;
  92         char pbuf[sizeof("65535")], *tmp;
  93         u_int16_t len;
  94         __be16 port;
  95         int ret = NF_ACCEPT;
  96         typeof(nf_nat_amanda_hook) nf_nat_amanda;
  97
  98         /* Only look at packets from the Amanda server */
  99         if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL)
 100                 return NF_ACCEPT;
 101
 102         /* increase the UDP timeout of the master connection as replies from
 103          * Amanda clients to the server can be quite delayed */
 104         nf_ct_refresh(ct, skb, master_timeout * HZ);
 105
 106         /* No data? */
 107         dataoff = protoff + sizeof(struct udphdr);
 108         if (dataoff >= skb->len) {
 109                 if (net_ratelimit())
 110                         printk("amanda_help: skblen = %u\n", skb->len);
 111                 return NF_ACCEPT;
 112         }
 113
 114         memset(&ts, 0, sizeof(ts));
 115         start = skb_find_text(skb, dataoff, skb->len,
 116                               search[SEARCH_CONNECT].ts, &ts);
 117         if (start == UINT_MAX)
 118                 goto out;
 119         start += dataoff + search[SEARCH_CONNECT].len;
 120
 121         memset(&ts, 0, sizeof(ts));
 122         stop = skb_find_text(skb, start, skb->len,
 123                              search[SEARCH_NEWLINE].ts, &ts);
 124         if (stop == UINT_MAX)
 125                 goto out;
 126         stop += start;
 127
 128         for (i = SEARCH_DATA; i <= SEARCH_INDEX; i++) {
 129                 memset(&ts, 0, sizeof(ts));
 130                 off = skb_find_text(skb, start, stop, search[i].ts, &ts);
 131                 if (off == UINT_MAX)
 132                         continue;
 133                 off += start + search[i].len;
 134
 135                 len = min_t(unsigned int, sizeof(pbuf) - 1, stop - off);
 136                 if (skb_copy_bits(skb, off, pbuf, len))
 137                         break;
 138                 pbuf[len] = '\0';
 139
 140                 port = htons(simple_strtoul(pbuf, &tmp, 10));
 141                 len = tmp - pbuf;
 142                 if (port == 0 || len > 5)
 143                         break;
 144
 145                 exp = nf_ct_expect_alloc(ct);
 146                 if (exp == NULL) {
 147                         ret = NF_DROP;
 148                         goto out;
 149                 }
 150                 tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 151                 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
 152                                   nf_ct_l3num(ct),
 153                                   &tuple->src.u3, &tuple->dst.u3,
 154                                   IPPROTO_TCP, NULL, &port);
 155
 156                 nf_nat_amanda = rcu_dereference(nf_nat_amanda_hook);
 157                 if (nf_nat_amanda && ct->status & IPS_NAT_MASK)
 158                         ret = nf_nat_amanda(skb, ctinfo, off - dataoff,
 159                                             len, exp);
 160                 else if (nf_ct_expect_related(exp) != 0)
 161                         ret = NF_DROP;
 162                 nf_ct_expect_put(exp);
 163         }
 164
 165 out:
 166         return ret;
 167 }
 168
 169 static const struct nf_conntrack_expect_policy amanda_exp_policy = {
 170         .max_expected           = 3,
 171         .timeout                = 180,
 172 };
 173
 174 static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
 175         {
 176                 .name                   = "amanda",
 177                 .me                     = THIS_MODULE,
 178                 .help                   = amanda_help,
 179                 .tuple.src.l3num        = AF_INET,
 180                 .tuple.src.u.udp.port   = cpu_to_be16(10080),
 181                 .tuple.dst.protonum     = IPPROTO_UDP,
 182                 .expect_policy          = &amanda_exp_policy,
 183         },
 184         {
 185                 .name                   = "amanda",
 186                 .me                     = THIS_MODULE,
 187                 .help                   = amanda_help,
 188                 .tuple.src.l3num        = AF_INET6,
 189                 .tuple.src.u.udp.port   = cpu_to_be16(10080),
 190                 .tuple.dst.protonum     = IPPROTO_UDP,
 191                 .expect_policy          = &amanda_exp_policy,
 192         },
 193 };
 194
 195 static void __exit nf_conntrack_amanda_fini(void)
 196 {
 197         int i;
 198
 199         nf_conntrack_helper_unregister(&amanda_helper[0]);
 200         nf_conntrack_helper_unregister(&amanda_helper[1]);
 201         for (i = 0; i < ARRAY_SIZE(search); i++)
 202                 textsearch_destroy(search[i].ts);
 203 }
 204
 205 static int __init nf_conntrack_amanda_init(void)
 206 {
 207         int ret, i;
 208
 209         for (i = 0; i < ARRAY_SIZE(search); i++) {
 210                 search[i].ts = textsearch_prepare(ts_algo, search[i].string,
 211                                                   search[i].len,
 212                                                   GFP_KERNEL, TS_AUTOLOAD);
 213                 if (IS_ERR(search[i].ts)) {
 214                         ret = PTR_ERR(search[i].ts);
 215                         goto err1;
 216                 }
 217         }
 218         ret = nf_conntrack_helper_register(&amanda_helper[0]);
 219         if (ret < 0)
 220                 goto err1;
 221         ret = nf_conntrack_helper_register(&amanda_helper[1]);
 222         if (ret < 0)
 223                 goto err2;
 224         return 0;
 225
 226 err2:
 227         nf_conntrack_helper_unregister(&amanda_helper[0]);
 228 err1:
 229         while (--i >= 0)
 230                 textsearch_destroy(search[i].ts);
 231
 232         return ret;
 233 }
 234
 235 module_init(nf_conntrack_amanda_init);
 236 module_exit(nf_conntrack_amanda_fini);