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");
  33MODULE_ALIAS_NFCT_HELPER("amanda");
  34
  35module_param(master_timeout, uint, 0600);
  36MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
  37module_param(ts_algo, charp, 0400);
  38MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
  39
  40unsigned int (*nf_nat_amanda_hook)(struct sk_buff *skb,
  41                                   enum ip_conntrack_info ctinfo,
  42                                   unsigned int matchoff,
  43                                   unsigned int matchlen,
  44                                   struct nf_conntrack_expect *exp)
  45                                   __read_mostly;
  46EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
  47
  48enum amanda_strings {
  49        SEARCH_CONNECT,
  50        SEARCH_NEWLINE,
  51        SEARCH_DATA,
  52        SEARCH_MESG,
  53        SEARCH_INDEX,
  54};
  55
  56static struct {
  57        const char              *string;
  58        size_t                  len;
  59        struct ts_config        *ts;
  60} search[] __read_mostly = {
  61        [SEARCH_CONNECT] = {
  62                .string = "CONNECT ",
  63                .len    = 8,
  64        },
  65        [SEARCH_NEWLINE] = {
  66                .string = "\n",
  67                .len    = 1,
  68        },
  69        [SEARCH_DATA] = {
  70                .string = "DATA ",
  71                .len    = 5,
  72        },
  73        [SEARCH_MESG] = {
  74                .string = "MESG ",
  75                .len    = 5,
  76        },
  77        [SEARCH_INDEX] = {
  78                .string = "INDEX ",
  79                .len    = 6,
  80        },
  81};
  82
  83static int amanda_help(struct sk_buff *skb,
  84                       unsigned int protoff,
  85                       struct nf_conn *ct,
  86                       enum ip_conntrack_info ctinfo)
  87{
  88        struct ts_state ts;
  89        struct nf_conntrack_expect *exp;
  90        struct nf_conntrack_tuple *tuple;
  91        unsigned int dataoff, start, stop, off, i;
  92        char pbuf[sizeof("65535")], *tmp;
  93        u_int16_t len;
  94        __be16 port;
  95        int ret = NF_ACCEPT;
  96        typeof(nf_nat_amanda_hook) nf_nat_amanda;
  97
  98        /* Only look at packets from the Amanda server */
  99        if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL)
 100                return NF_ACCEPT;
 101
 102        /* increase the UDP timeout of the master connection as replies from
 103         * Amanda clients to the server can be quite delayed */
 104        nf_ct_refresh(ct, skb, master_timeout * HZ);
 105
 106        /* No data? */
 107        dataoff = protoff + sizeof(struct udphdr);
 108        if (dataoff >= skb->len) {
 109                if (net_ratelimit())
 110                        printk("amanda_help: skblen = %u\n", skb->len);
 111                return NF_ACCEPT;
 112        }
 113
 114        memset(&ts, 0, sizeof(ts));
 115        start = skb_find_text(skb, dataoff, skb->len,
 116                              search[SEARCH_CONNECT].ts, &ts);
 117        if (start == UINT_MAX)
 118                goto out;
 119        start += dataoff + search[SEARCH_CONNECT].len;
 120
 121        memset(&ts, 0, sizeof(ts));
 122        stop = skb_find_text(skb, start, skb->len,
 123                             search[SEARCH_NEWLINE].ts, &ts);
 124        if (stop == UINT_MAX)
 125                goto out;
 126        stop += start;
 127
 128        for (i = SEARCH_DATA; i <= SEARCH_INDEX; i++) {
 129                memset(&ts, 0, sizeof(ts));
 130                off = skb_find_text(skb, start, stop, search[i].ts, &ts);
 131                if (off == UINT_MAX)
 132                        continue;
 133                off += start + search[i].len;
 134
 135                len = min_t(unsigned int, sizeof(pbuf) - 1, stop - off);
 136                if (skb_copy_bits(skb, off, pbuf, len))
 137                        break;
 138                pbuf[len] = '\0';
 139
 140                port = htons(simple_strtoul(pbuf, &tmp, 10));
 141                len = tmp - pbuf;
 142                if (port == 0 || len > 5)
 143                        break;
 144
 145                exp = nf_ct_expect_alloc(ct);
 146                if (exp == NULL) {
 147                        ret = NF_DROP;
 148                        goto out;
 149                }
 150                tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 151                nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
 152                                  nf_ct_l3num(ct),
 153                                  &tuple->src.u3, &tuple->dst.u3,
 154                                  IPPROTO_TCP, NULL, &port);
 155
 156                nf_nat_amanda = rcu_dereference(nf_nat_amanda_hook);
 157                if (nf_nat_amanda && ct->status & IPS_NAT_MASK)
 158                        ret = nf_nat_amanda(skb, ctinfo, off - dataoff,
 159                                            len, exp);
 160                else if (nf_ct_expect_related(exp) != 0)
 161                        ret = NF_DROP;
 162                nf_ct_expect_put(exp);
 163        }
 164
 165out:
 166        return ret;
 167}
 168
 169static const struct nf_conntrack_expect_policy amanda_exp_policy = {
 170        .max_expected           = 3,
 171        .timeout                = 180,
 172};
 173
 174static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
 175        {
 176                .name                   = "amanda",
 177                .me                     = THIS_MODULE,
 178                .help                   = amanda_help,
 179                .tuple.src.l3num        = AF_INET,
 180                .tuple.src.u.udp.port   = cpu_to_be16(10080),
 181                .tuple.dst.protonum     = IPPROTO_UDP,
 182                .expect_policy          = &amanda_exp_policy,
 183        },
 184        {
 185                .name                   = "amanda",
 186                .me                     = THIS_MODULE,
 187                .help                   = amanda_help,
 188                .tuple.src.l3num        = AF_INET6,
 189                .tuple.src.u.udp.port   = cpu_to_be16(10080),
 190                .tuple.dst.protonum     = IPPROTO_UDP,
 191                .expect_policy          = &amanda_exp_policy,
 192        },
 193};
 194
 195static void __exit nf_conntrack_amanda_fini(void)
 196{
 197        int i;
 198
 199        nf_conntrack_helper_unregister(&amanda_helper[0]);
 200        nf_conntrack_helper_unregister(&amanda_helper[1]);
 201        for (i = 0; i < ARRAY_SIZE(search); i++)
 202                textsearch_destroy(search[i].ts);
 203}
 204
 205static int __init nf_conntrack_amanda_init(void)
 206{
 207        int ret, i;
 208
 209        for (i = 0; i < ARRAY_SIZE(search); i++) {
 210                search[i].ts = textsearch_prepare(ts_algo, search[i].string,
 211                                                  search[i].len,
 212                                                  GFP_KERNEL, TS_AUTOLOAD);
 213                if (IS_ERR(search[i].ts)) {
 214                        ret = PTR_ERR(search[i].ts);
 215                        goto err1;
 216                }
 217        }
 218        ret = nf_conntrack_helper_register(&amanda_helper[0]);
 219        if (ret < 0)
 220                goto err1;
 221        ret = nf_conntrack_helper_register(&amanda_helper[1]);
 222        if (ret < 0)
 223                goto err2;
 224        return 0;
 225
 226err2:
 227        nf_conntrack_helper_unregister(&amanda_helper[0]);
 228err1:
 229        while (--i >= 0)
 230                textsearch_destroy(search[i].ts);
 231
 232        return ret;
 233}
 234
 235module_init(nf_conntrack_amanda_init);
 236module_exit(nf_conntrack_amanda_fini);
 237