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 * (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
  28static unsigned int master_timeout __read_mostly = 300;
  29static char *ts_algo = "kmp";
  30
  31MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
  32MODULE_DESCRIPTION("Amanda connection tracking module");
  33MODULE_LICENSE("GPL");
  34MODULE_ALIAS("ip_conntrack_amanda");
  35MODULE_ALIAS_NFCT_HELPER("amanda");
  36
  37module_param(master_timeout, uint, 0600);
  38MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
  39module_param(ts_algo, charp, 0400);
  40MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
  41
  42unsigned 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;
  49EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
  50
  51enum amanda_strings {
  52        SEARCH_CONNECT,
  53        SEARCH_NEWLINE,
  54        SEARCH_DATA,
  55        SEARCH_MESG,
  56        SEARCH_INDEX,
  57};
  58
  59static 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
  86static 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
 170out:
 171        return ret;
 172}
 173
 174static const struct nf_conntrack_expect_policy amanda_exp_policy = {
 175        .max_expected           = 3,
 176        .timeout                = 180,
 177};
 178
 179static 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
 200static 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
 210static 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
 231err2:
 232        nf_conntrack_helper_unregister(&amanda_helper[0]);
 233err1:
 234        while (--i >= 0)
 235                textsearch_destroy(search[i].ts);
 236
 237        return ret;
 238}
 239
 240module_init(nf_conntrack_amanda_init);
 241module_exit(nf_conntrack_amanda_fini);
 242
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