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