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  * (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
  28 static unsigned int master_timeout __read_mostly = 300;
  29 static char *ts_algo = "kmp";
  30
  31 MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
  32 MODULE_DESCRIPTION("Amanda connection tracking module");
  33 MODULE_LICENSE("GPL");
  34 MODULE_ALIAS("ip_conntrack_amanda");
  35 MODULE_ALIAS_NFCT_HELPER("amanda");
  36
  37 module_param(master_timeout, uint, 0600);
  38 MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
  39 module_param(ts_algo, charp, 0400);
  40 MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
  41
  42 unsigned 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;
  49 EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
  50
  51 enum amanda_strings {
  52         SEARCH_CONNECT,
  53         SEARCH_NEWLINE,
  54         SEARCH_DATA,
  55         SEARCH_MESG,
  56         SEARCH_INDEX,
  57 };
  58
  59 static 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
  86 static 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 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         start = skb_find_text(skb, dataoff, skb->len,
 116                               search[SEARCH_CONNECT].ts);
 117         if (start == UINT_MAX)
 118                 goto out;
 119         start += dataoff + search[SEARCH_CONNECT].len;
 120
 121         stop = skb_find_text(skb, start, skb->len,
 122                              search[SEARCH_NEWLINE].ts);
 123         if (stop == UINT_MAX)
 124                 goto out;
 125         stop += start;
 126
 127         for (i = SEARCH_DATA; i <= SEARCH_INDEX; i++) {
 128                 off = skb_find_text(skb, start, stop, search[i].ts);
 129                 if (off == UINT_MAX)
 130                         continue;
 131                 off += start + search[i].len;
 132
 133                 len = min_t(unsigned int, sizeof(pbuf) - 1, stop - off);
 134                 if (skb_copy_bits(skb, off, pbuf, len))
 135                         break;
 136                 pbuf[len] = '\0';
 137
 138                 port = htons(simple_strtoul(pbuf, &tmp, 10));
 139                 len = tmp - pbuf;
 140                 if (port == 0 || len > 5)
 141                         break;
 142
 143                 exp = nf_ct_expect_alloc(ct);
 144                 if (exp == NULL) {
 145                         nf_ct_helper_log(skb, ct, "cannot alloc expectation");
 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, protoff,
 158                                             off - dataoff, len, exp);
 159                 else if (nf_ct_expect_related(exp) != 0) {
 160                         nf_ct_helper_log(skb, ct, "cannot add expectation");
 161                         ret = NF_DROP;
 162                 }
 163                 nf_ct_expect_put(exp);
 164         }
 165
 166 out:
 167         return ret;
 168 }
 169
 170 static const struct nf_conntrack_expect_policy amanda_exp_policy = {
 171         .max_expected           = 3,
 172         .timeout                = 180,
 173 };
 174
 175 static 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
 196 static void __exit nf_conntrack_amanda_fini(void)
 197 {
 198         int i;
 199
 200         nf_conntrack_helpers_unregister(amanda_helper,
 201                                         ARRAY_SIZE(amanda_helper));
 202         for (i = 0; i < ARRAY_SIZE(search); i++)
 203                 textsearch_destroy(search[i].ts);
 204 }
 205
 206 static int __init nf_conntrack_amanda_init(void)
 207 {
 208         int ret, i;
 209
 210         NF_CT_HELPER_BUILD_BUG_ON(0);
 211
 212         for (i = 0; i < ARRAY_SIZE(search); i++) {
 213                 search[i].ts = textsearch_prepare(ts_algo, search[i].string,
 214                                                   search[i].len,
 215                                                   GFP_KERNEL, TS_AUTOLOAD);
 216                 if (IS_ERR(search[i].ts)) {
 217                         ret = PTR_ERR(search[i].ts);
 218                         goto err1;
 219                 }
 220         }
 221         ret = nf_conntrack_helpers_register(amanda_helper,
 222                                             ARRAY_SIZE(amanda_helper));
 223         if (ret < 0)
 224                 goto err1;
 225         return 0;
 226
 227 err1:
 228         while (--i >= 0)
 229                 textsearch_destroy(search[i].ts);
 230
 231         return ret;
 232 }
 233
 234 module_init(nf_conntrack_amanda_init);
 235 module_exit(nf_conntrack_amanda_fini);