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#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
  27static unsigned int master_timeout __read_mostly = 300;
  28static char *ts_algo = "kmp";
  29
  30MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
  31MODULE_DESCRIPTION("Amanda connection tracking module");
  32MODULE_LICENSE("GPL");
  33MODULE_ALIAS("ip_conntrack_amanda");
  34MODULE_ALIAS_NFCT_HELPER("amanda");
  35
  36module_param(master_timeout, uint, 0600);
  37MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
  38module_param(ts_algo, charp, 0400);
  39MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
  40
  41unsigned 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;
  48EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
  49
  50enum amanda_strings {
  51        SEARCH_CONNECT,
  52        SEARCH_NEWLINE,
  53        SEARCH_DATA,
  54        SEARCH_MESG,
  55        SEARCH_INDEX,
  56};
  57
  58static 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
  85static 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                        ret = NF_DROP;
 149                        goto out;
 150                }
 151                tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 152                nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
 153                                  nf_ct_l3num(ct),
 154                                  &tuple->src.u3, &tuple->dst.u3,
 155                                  IPPROTO_TCP, NULL, &port);
 156
 157                nf_nat_amanda = rcu_dereference(nf_nat_amanda_hook);
 158                if (nf_nat_amanda && ct->status & IPS_NAT_MASK)
 159                        ret = nf_nat_amanda(skb, ctinfo, protoff,
 160                                            off - dataoff, len, exp);
 161                else if (nf_ct_expect_related(exp) != 0)
 162                        ret = NF_DROP;
 163                nf_ct_expect_put(exp);
 164        }
 165
 166out:
 167        return ret;
 168}
 169
 170static const struct nf_conntrack_expect_policy amanda_exp_policy = {
 171        .max_expected           = 3,
 172        .timeout                = 180,
 173};
 174
 175static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
 176        {
 177                .name                   = "amanda",
 178                .me                     = THIS_MODULE,
 179                .help                   = amanda_help,
 180                .tuple.src.l3num        = AF_INET,
 181                .tuple.src.u.udp.port   = cpu_to_be16(10080),
 182                .tuple.dst.protonum     = IPPROTO_UDP,
 183                .expect_policy          = &amanda_exp_policy,
 184        },
 185        {
 186                .name                   = "amanda",
 187                .me                     = THIS_MODULE,
 188                .help                   = amanda_help,
 189                .tuple.src.l3num        = AF_INET6,
 190                .tuple.src.u.udp.port   = cpu_to_be16(10080),
 191                .tuple.dst.protonum     = IPPROTO_UDP,
 192                .expect_policy          = &amanda_exp_policy,
 193        },
 194};
 195
 196static void __exit nf_conntrack_amanda_fini(void)
 197{
 198        int i;
 199
 200        nf_conntrack_helper_unregister(&amanda_helper[0]);
 201        nf_conntrack_helper_unregister(&amanda_helper[1]);
 202        for (i = 0; i < ARRAY_SIZE(search); i++)
 203                textsearch_destroy(search[i].ts);
 204}
 205
 206static int __init nf_conntrack_amanda_init(void)
 207{
 208        int ret, i;
 209
 210        for (i = 0; i < ARRAY_SIZE(search); i++) {
 211                search[i].ts = textsearch_prepare(ts_algo, search[i].string,
 212                                                  search[i].len,
 213                                                  GFP_KERNEL, TS_AUTOLOAD);
 214                if (IS_ERR(search[i].ts)) {
 215                        ret = PTR_ERR(search[i].ts);
 216                        goto err1;
 217                }
 218        }
 219        ret = nf_conntrack_helper_register(&amanda_helper[0]);
 220        if (ret < 0)
 221                goto err1;
 222        ret = nf_conntrack_helper_register(&amanda_helper[1]);
 223        if (ret < 0)
 224                goto err2;
 225        return 0;
 226
 227err2:
 228        nf_conntrack_helper_unregister(&amanda_helper[0]);
 229err1:
 230        while (--i >= 0)
 231                textsearch_destroy(search[i].ts);
 232
 233        return ret;
 234}
 235
 236module_init(nf_conntrack_amanda_init);
 237module_exit(nf_conntrack_amanda_fini);
 238
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