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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 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);
236 

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