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  * (C) 2006 Patrick McHardy <kaber@trash.net>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version
  10  * 2 of the License, or (at your option) any later version.
  11  */
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/moduleparam.h>
  15 #include <linux/textsearch.h>
  16 #include <linux/skbuff.h>
  17 #include <linux/in.h>
  18 #include <linux/udp.h>
  19 #include <linux/netfilter.h>
  20 #include <linux/gfp.h>
  21
  22 #include <net/netfilter/nf_conntrack.h>
  23 #include <net/netfilter/nf_conntrack_expect.h>
  24 #include <net/netfilter/nf_conntrack_ecache.h>
  25 #include <net/netfilter/nf_conntrack_helper.h>
  26 #include <linux/netfilter/nf_conntrack_amanda.h>
  27
  28 static unsigned int master_timeout __read_mostly = 300;
  29 static char *ts_algo = "kmp";
  30
  31 MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
  32 MODULE_DESCRIPTION("Amanda connection tracking module");
  33 MODULE_LICENSE("GPL");
  34 MODULE_ALIAS("ip_conntrack_amanda");
  35 MODULE_ALIAS_NFCT_HELPER("amanda");
  36
  37 module_param(master_timeout, uint, 0600);
  38 MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
  39 module_param(ts_algo, charp, 0400);
  40 MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
  41
  42 unsigned int (*nf_nat_amanda_hook)(struct sk_buff *skb,
  43                                    enum ip_conntrack_info ctinfo,
  44                                    unsigned int protoff,
  45                                    unsigned int matchoff,
  46                                    unsigned int matchlen,
  47                                    struct nf_conntrack_expect *exp)
  48                                    __read_mostly;
  49 EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
  50
  51 enum amanda_strings {
  52         SEARCH_CONNECT,
  53         SEARCH_NEWLINE,
  54         SEARCH_DATA,
  55         SEARCH_MESG,
  56         SEARCH_INDEX,
  57 };
  58
  59 static struct {
  60         const char              *string;
  61         size_t                  len;
  62         struct ts_config        *ts;
  63 } search[] __read_mostly = {
  64         [SEARCH_CONNECT] = {
  65                 .string = "CONNECT ",
  66                 .len    = 8,
  67         },
  68         [SEARCH_NEWLINE] = {
  69                 .string = "\n",
  70                 .len    = 1,
  71         },
  72         [SEARCH_DATA] = {
  73                 .string = "DATA ",
  74                 .len    = 5,
  75         },
  76         [SEARCH_MESG] = {
  77                 .string = "MESG ",
  78                 .len    = 5,
  79         },
  80         [SEARCH_INDEX] = {
  81                 .string = "INDEX ",
  82                 .len    = 6,
  83         },
  84 };
  85
  86 static int amanda_help(struct sk_buff *skb,
  87                        unsigned int protoff,
  88                        struct nf_conn *ct,
  89                        enum ip_conntrack_info ctinfo)
  90 {
  91         struct ts_state ts;
  92         struct nf_conntrack_expect *exp;
  93         struct nf_conntrack_tuple *tuple;
  94         unsigned int dataoff, start, stop, off, i;
  95         char pbuf[sizeof("65535")], *tmp;
  96         u_int16_t len;
  97         __be16 port;
  98         int ret = NF_ACCEPT;
  99         typeof(nf_nat_amanda_hook) nf_nat_amanda;
 100
 101         /* Only look at packets from the Amanda server */
 102         if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL)
 103                 return NF_ACCEPT;
 104
 105         /* increase the UDP timeout of the master connection as replies from
 106          * Amanda clients to the server can be quite delayed */
 107         nf_ct_refresh(ct, skb, master_timeout * HZ);
 108
 109         /* No data? */
 110         dataoff = protoff + sizeof(struct udphdr);
 111         if (dataoff >= skb->len) {
 112                 net_err_ratelimited("amanda_help: skblen = %u\n", skb->len);
 113                 return NF_ACCEPT;
 114         }
 115
 116         memset(&ts, 0, sizeof(ts));
 117         start = skb_find_text(skb, dataoff, skb->len,
 118                               search[SEARCH_CONNECT].ts, &ts);
 119         if (start == UINT_MAX)
 120                 goto out;
 121         start += dataoff + search[SEARCH_CONNECT].len;
 122
 123         memset(&ts, 0, sizeof(ts));
 124         stop = skb_find_text(skb, start, skb->len,
 125                              search[SEARCH_NEWLINE].ts, &ts);
 126         if (stop == UINT_MAX)
 127                 goto out;
 128         stop += start;
 129
 130         for (i = SEARCH_DATA; i <= SEARCH_INDEX; i++) {
 131                 memset(&ts, 0, sizeof(ts));
 132                 off = skb_find_text(skb, start, stop, search[i].ts, &ts);
 133                 if (off == UINT_MAX)
 134                         continue;
 135                 off += start + search[i].len;
 136
 137                 len = min_t(unsigned int, sizeof(pbuf) - 1, stop - off);
 138                 if (skb_copy_bits(skb, off, pbuf, len))
 139                         break;
 140                 pbuf[len] = '\0';
 141
 142                 port = htons(simple_strtoul(pbuf, &tmp, 10));
 143                 len = tmp - pbuf;
 144                 if (port == 0 || len > 5)
 145                         break;
 146
 147                 exp = nf_ct_expect_alloc(ct);
 148                 if (exp == NULL) {
 149                         nf_ct_helper_log(skb, ct, "cannot alloc expectation");
 150                         ret = NF_DROP;
 151                         goto out;
 152                 }
 153                 tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 154                 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
 155                                   nf_ct_l3num(ct),
 156                                   &tuple->src.u3, &tuple->dst.u3,
 157                                   IPPROTO_TCP, NULL, &port);
 158
 159                 nf_nat_amanda = rcu_dereference(nf_nat_amanda_hook);
 160                 if (nf_nat_amanda && ct->status & IPS_NAT_MASK)
 161                         ret = nf_nat_amanda(skb, ctinfo, protoff,
 162                                             off - dataoff, len, exp);
 163                 else if (nf_ct_expect_related(exp) != 0) {
 164                         nf_ct_helper_log(skb, ct, "cannot add expectation");
 165                         ret = NF_DROP;
 166                 }
 167                 nf_ct_expect_put(exp);
 168         }
 169
 170 out:
 171         return ret;
 172 }
 173
 174 static const struct nf_conntrack_expect_policy amanda_exp_policy = {
 175         .max_expected           = 3,
 176         .timeout                = 180,
 177 };
 178
 179 static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
 180         {
 181                 .name                   = "amanda",
 182                 .me                     = THIS_MODULE,
 183                 .help                   = amanda_help,
 184                 .tuple.src.l3num        = AF_INET,
 185                 .tuple.src.u.udp.port   = cpu_to_be16(10080),
 186                 .tuple.dst.protonum     = IPPROTO_UDP,
 187                 .expect_policy          = &amanda_exp_policy,
 188         },
 189         {
 190                 .name                   = "amanda",
 191                 .me                     = THIS_MODULE,
 192                 .help                   = amanda_help,
 193                 .tuple.src.l3num        = AF_INET6,
 194                 .tuple.src.u.udp.port   = cpu_to_be16(10080),
 195                 .tuple.dst.protonum     = IPPROTO_UDP,
 196                 .expect_policy          = &amanda_exp_policy,
 197         },
 198 };
 199
 200 static void __exit nf_conntrack_amanda_fini(void)
 201 {
 202         int i;
 203
 204         nf_conntrack_helper_unregister(&amanda_helper[0]);
 205         nf_conntrack_helper_unregister(&amanda_helper[1]);
 206         for (i = 0; i < ARRAY_SIZE(search); i++)
 207                 textsearch_destroy(search[i].ts);
 208 }
 209
 210 static int __init nf_conntrack_amanda_init(void)
 211 {
 212         int ret, i;
 213
 214         for (i = 0; i < ARRAY_SIZE(search); i++) {
 215                 search[i].ts = textsearch_prepare(ts_algo, search[i].string,
 216                                                   search[i].len,
 217                                                   GFP_KERNEL, TS_AUTOLOAD);
 218                 if (IS_ERR(search[i].ts)) {
 219                         ret = PTR_ERR(search[i].ts);
 220                         goto err1;
 221                 }
 222         }
 223         ret = nf_conntrack_helper_register(&amanda_helper[0]);
 224         if (ret < 0)
 225                 goto err1;
 226         ret = nf_conntrack_helper_register(&amanda_helper[1]);
 227         if (ret < 0)
 228                 goto err2;
 229         return 0;
 230
 231 err2:
 232         nf_conntrack_helper_unregister(&amanda_helper[0]);
 233 err1:
 234         while (--i >= 0)
 235                 textsearch_destroy(search[i].ts);
 236
 237         return ret;
 238 }
 239
 240 module_init(nf_conntrack_amanda_init);
 241 module_exit(nf_conntrack_amanda_fini);