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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 
 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 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 
170 out:
171         return ret;
172 }
173 
174 static const struct nf_conntrack_expect_policy amanda_exp_policy = {
175         .max_expected           = 3,
176         .timeout                = 180,
177 };
178 
179 static 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 
200 static 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 
210 static 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 
231 err2:
232         nf_conntrack_helper_unregister(&amanda_helper[0]);
233 err1:
234         while (--i >= 0)
235                 textsearch_destroy(search[i].ts);
236 
237         return ret;
238 }
239 
240 module_init(nf_conntrack_amanda_init);
241 module_exit(nf_conntrack_amanda_fini);
242 

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