linux/net/netfilter/nf_conntrack_amanda.c
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   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
  26static unsigned int master_timeout __read_mostly = 300;
  27static char *ts_algo = "kmp";
  28
  29MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
  30MODULE_DESCRIPTION("Amanda connection tracking module");
  31MODULE_LICENSE("GPL");
  32MODULE_ALIAS("ip_conntrack_amanda");
  33
  34module_param(master_timeout, uint, 0600);
  35MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
  36module_param(ts_algo, charp, 0400);
  37MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
  38
  39unsigned 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;
  45EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
  46
  47enum amanda_strings {
  48        SEARCH_CONNECT,
  49        SEARCH_NEWLINE,
  50        SEARCH_DATA,
  51        SEARCH_MESG,
  52        SEARCH_INDEX,
  53};
  54
  55static 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
  82static 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
 164out:
 165        return ret;
 166}
 167
 168static const struct nf_conntrack_expect_policy amanda_exp_policy = {
 169        .max_expected           = 3,
 170        .timeout                = 180,
 171};
 172
 173static 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
 194static 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
 204static 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
 225err2:
 226        nf_conntrack_helper_unregister(&amanda_helper[0]);
 227err1:
 228        while (--i >= 0)
 229                textsearch_destroy(search[i].ts);
 230
 231        return ret;
 232}
 233
 234module_init(nf_conntrack_amanda_init);
 235module_exit(nf_conntrack_amanda_fini);
 236