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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  *
  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 
 26 static unsigned int master_timeout __read_mostly = 300;
 27 static char *ts_algo = "kmp";
 28 
 29 MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
 30 MODULE_DESCRIPTION("Amanda connection tracking module");
 31 MODULE_LICENSE("GPL");
 32 MODULE_ALIAS("ip_conntrack_amanda");
 33 MODULE_ALIAS_NFCT_HELPER("amanda");
 34 
 35 module_param(master_timeout, uint, 0600);
 36 MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
 37 module_param(ts_algo, charp, 0400);
 38 MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
 39 
 40 unsigned 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;
 46 EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
 47 
 48 enum amanda_strings {
 49         SEARCH_CONNECT,
 50         SEARCH_NEWLINE,
 51         SEARCH_DATA,
 52         SEARCH_MESG,
 53         SEARCH_INDEX,
 54 };
 55 
 56 static 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 
 83 static 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 
165 out:
166         return ret;
167 }
168 
169 static const struct nf_conntrack_expect_policy amanda_exp_policy = {
170         .max_expected           = 3,
171         .timeout                = 180,
172 };
173 
174 static 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 
195 static 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 
205 static 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 
226 err2:
227         nf_conntrack_helper_unregister(&amanda_helper[0]);
228 err1:
229         while (--i >= 0)
230                 textsearch_destroy(search[i].ts);
231 
232         return ret;
233 }
234 
235 module_init(nf_conntrack_amanda_init);
236 module_exit(nf_conntrack_amanda_fini);
237 

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