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TOMOYO Linux Cross Reference
Linux/net/netfilter/nf_synproxy_core.c

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  1 /*
  2  * Copyright (c) 2013 Patrick McHardy <kaber@trash.net>
  3  *
  4  * This program is free software; you can redistribute it and/or modify
  5  * it under the terms of the GNU General Public License version 2 as
  6  * published by the Free Software Foundation.
  7  */
  8 
  9 #include <linux/module.h>
 10 #include <linux/skbuff.h>
 11 #include <asm/unaligned.h>
 12 #include <net/tcp.h>
 13 #include <net/netns/generic.h>
 14 
 15 #include <linux/netfilter_ipv4/ip_tables.h>
 16 #include <linux/netfilter/x_tables.h>
 17 #include <linux/netfilter/xt_tcpudp.h>
 18 #include <linux/netfilter/xt_SYNPROXY.h>
 19 #include <net/netfilter/nf_conntrack.h>
 20 #include <net/netfilter/nf_conntrack_extend.h>
 21 #include <net/netfilter/nf_conntrack_seqadj.h>
 22 #include <net/netfilter/nf_conntrack_synproxy.h>
 23 
 24 int synproxy_net_id;
 25 EXPORT_SYMBOL_GPL(synproxy_net_id);
 26 
 27 bool
 28 synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
 29                        const struct tcphdr *th, struct synproxy_options *opts)
 30 {
 31         int length = (th->doff * 4) - sizeof(*th);
 32         u8 buf[40], *ptr;
 33 
 34         ptr = skb_header_pointer(skb, doff + sizeof(*th), length, buf);
 35         if (ptr == NULL)
 36                 return false;
 37 
 38         opts->options = 0;
 39         while (length > 0) {
 40                 int opcode = *ptr++;
 41                 int opsize;
 42 
 43                 switch (opcode) {
 44                 case TCPOPT_EOL:
 45                         return true;
 46                 case TCPOPT_NOP:
 47                         length--;
 48                         continue;
 49                 default:
 50                         opsize = *ptr++;
 51                         if (opsize < 2)
 52                                 return true;
 53                         if (opsize > length)
 54                                 return true;
 55 
 56                         switch (opcode) {
 57                         case TCPOPT_MSS:
 58                                 if (opsize == TCPOLEN_MSS) {
 59                                         opts->mss = get_unaligned_be16(ptr);
 60                                         opts->options |= XT_SYNPROXY_OPT_MSS;
 61                                 }
 62                                 break;
 63                         case TCPOPT_WINDOW:
 64                                 if (opsize == TCPOLEN_WINDOW) {
 65                                         opts->wscale = *ptr;
 66                                         if (opts->wscale > 14)
 67                                                 opts->wscale = 14;
 68                                         opts->options |= XT_SYNPROXY_OPT_WSCALE;
 69                                 }
 70                                 break;
 71                         case TCPOPT_TIMESTAMP:
 72                                 if (opsize == TCPOLEN_TIMESTAMP) {
 73                                         opts->tsval = get_unaligned_be32(ptr);
 74                                         opts->tsecr = get_unaligned_be32(ptr + 4);
 75                                         opts->options |= XT_SYNPROXY_OPT_TIMESTAMP;
 76                                 }
 77                                 break;
 78                         case TCPOPT_SACK_PERM:
 79                                 if (opsize == TCPOLEN_SACK_PERM)
 80                                         opts->options |= XT_SYNPROXY_OPT_SACK_PERM;
 81                                 break;
 82                         }
 83 
 84                         ptr += opsize - 2;
 85                         length -= opsize;
 86                 }
 87         }
 88         return true;
 89 }
 90 EXPORT_SYMBOL_GPL(synproxy_parse_options);
 91 
 92 unsigned int synproxy_options_size(const struct synproxy_options *opts)
 93 {
 94         unsigned int size = 0;
 95 
 96         if (opts->options & XT_SYNPROXY_OPT_MSS)
 97                 size += TCPOLEN_MSS_ALIGNED;
 98         if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP)
 99                 size += TCPOLEN_TSTAMP_ALIGNED;
100         else if (opts->options & XT_SYNPROXY_OPT_SACK_PERM)
101                 size += TCPOLEN_SACKPERM_ALIGNED;
102         if (opts->options & XT_SYNPROXY_OPT_WSCALE)
103                 size += TCPOLEN_WSCALE_ALIGNED;
104 
105         return size;
106 }
107 EXPORT_SYMBOL_GPL(synproxy_options_size);
108 
109 void
110 synproxy_build_options(struct tcphdr *th, const struct synproxy_options *opts)
111 {
112         __be32 *ptr = (__be32 *)(th + 1);
113         u8 options = opts->options;
114 
115         if (options & XT_SYNPROXY_OPT_MSS)
116                 *ptr++ = htonl((TCPOPT_MSS << 24) |
117                                (TCPOLEN_MSS << 16) |
118                                opts->mss);
119 
120         if (options & XT_SYNPROXY_OPT_TIMESTAMP) {
121                 if (options & XT_SYNPROXY_OPT_SACK_PERM)
122                         *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
123                                        (TCPOLEN_SACK_PERM << 16) |
124                                        (TCPOPT_TIMESTAMP << 8) |
125                                        TCPOLEN_TIMESTAMP);
126                 else
127                         *ptr++ = htonl((TCPOPT_NOP << 24) |
128                                        (TCPOPT_NOP << 16) |
129                                        (TCPOPT_TIMESTAMP << 8) |
130                                        TCPOLEN_TIMESTAMP);
131 
132                 *ptr++ = htonl(opts->tsval);
133                 *ptr++ = htonl(opts->tsecr);
134         } else if (options & XT_SYNPROXY_OPT_SACK_PERM)
135                 *ptr++ = htonl((TCPOPT_NOP << 24) |
136                                (TCPOPT_NOP << 16) |
137                                (TCPOPT_SACK_PERM << 8) |
138                                TCPOLEN_SACK_PERM);
139 
140         if (options & XT_SYNPROXY_OPT_WSCALE)
141                 *ptr++ = htonl((TCPOPT_NOP << 24) |
142                                (TCPOPT_WINDOW << 16) |
143                                (TCPOLEN_WINDOW << 8) |
144                                opts->wscale);
145 }
146 EXPORT_SYMBOL_GPL(synproxy_build_options);
147 
148 void synproxy_init_timestamp_cookie(const struct xt_synproxy_info *info,
149                                     struct synproxy_options *opts)
150 {
151         opts->tsecr = opts->tsval;
152         opts->tsval = tcp_time_stamp & ~0x3f;
153 
154         if (opts->options & XT_SYNPROXY_OPT_WSCALE) {
155                 opts->tsval |= opts->wscale;
156                 opts->wscale = info->wscale;
157         } else
158                 opts->tsval |= 0xf;
159 
160         if (opts->options & XT_SYNPROXY_OPT_SACK_PERM)
161                 opts->tsval |= 1 << 4;
162 
163         if (opts->options & XT_SYNPROXY_OPT_ECN)
164                 opts->tsval |= 1 << 5;
165 }
166 EXPORT_SYMBOL_GPL(synproxy_init_timestamp_cookie);
167 
168 void synproxy_check_timestamp_cookie(struct synproxy_options *opts)
169 {
170         opts->wscale = opts->tsecr & 0xf;
171         if (opts->wscale != 0xf)
172                 opts->options |= XT_SYNPROXY_OPT_WSCALE;
173 
174         opts->options |= opts->tsecr & (1 << 4) ? XT_SYNPROXY_OPT_SACK_PERM : 0;
175 
176         opts->options |= opts->tsecr & (1 << 5) ? XT_SYNPROXY_OPT_ECN : 0;
177 }
178 EXPORT_SYMBOL_GPL(synproxy_check_timestamp_cookie);
179 
180 unsigned int synproxy_tstamp_adjust(struct sk_buff *skb,
181                                     unsigned int protoff,
182                                     struct tcphdr *th,
183                                     struct nf_conn *ct,
184                                     enum ip_conntrack_info ctinfo,
185                                     const struct nf_conn_synproxy *synproxy)
186 {
187         unsigned int optoff, optend;
188         u32 *ptr, old;
189 
190         if (synproxy->tsoff == 0)
191                 return 1;
192 
193         optoff = protoff + sizeof(struct tcphdr);
194         optend = protoff + th->doff * 4;
195 
196         if (!skb_make_writable(skb, optend))
197                 return 0;
198 
199         while (optoff < optend) {
200                 unsigned char *op = skb->data + optoff;
201 
202                 switch (op[0]) {
203                 case TCPOPT_EOL:
204                         return 1;
205                 case TCPOPT_NOP:
206                         optoff++;
207                         continue;
208                 default:
209                         if (optoff + 1 == optend ||
210                             optoff + op[1] > optend ||
211                             op[1] < 2)
212                                 return 0;
213                         if (op[0] == TCPOPT_TIMESTAMP &&
214                             op[1] == TCPOLEN_TIMESTAMP) {
215                                 if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
216                                         ptr = (u32 *)&op[2];
217                                         old = *ptr;
218                                         *ptr = htonl(ntohl(*ptr) -
219                                                      synproxy->tsoff);
220                                 } else {
221                                         ptr = (u32 *)&op[6];
222                                         old = *ptr;
223                                         *ptr = htonl(ntohl(*ptr) +
224                                                      synproxy->tsoff);
225                                 }
226                                 inet_proto_csum_replace4(&th->check, skb,
227                                                          old, *ptr, 0);
228                                 return 1;
229                         }
230                         optoff += op[1];
231                 }
232         }
233         return 1;
234 }
235 EXPORT_SYMBOL_GPL(synproxy_tstamp_adjust);
236 
237 static struct nf_ct_ext_type nf_ct_synproxy_extend __read_mostly = {
238         .len            = sizeof(struct nf_conn_synproxy),
239         .align          = __alignof__(struct nf_conn_synproxy),
240         .id             = NF_CT_EXT_SYNPROXY,
241 };
242 
243 #ifdef CONFIG_PROC_FS
244 static void *synproxy_cpu_seq_start(struct seq_file *seq, loff_t *pos)
245 {
246         struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
247         int cpu;
248 
249         if (*pos == 0)
250                 return SEQ_START_TOKEN;
251 
252         for (cpu = *pos - 1; cpu < nr_cpu_ids; cpu++) {
253                 if (!cpu_possible(cpu))
254                         continue;
255                 *pos = cpu + 1;
256                 return per_cpu_ptr(snet->stats, cpu);
257         }
258 
259         return NULL;
260 }
261 
262 static void *synproxy_cpu_seq_next(struct seq_file *seq, void *v, loff_t *pos)
263 {
264         struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
265         int cpu;
266 
267         for (cpu = *pos; cpu < nr_cpu_ids; cpu++) {
268                 if (!cpu_possible(cpu))
269                         continue;
270                 *pos = cpu + 1;
271                 return per_cpu_ptr(snet->stats, cpu);
272         }
273 
274         return NULL;
275 }
276 
277 static void synproxy_cpu_seq_stop(struct seq_file *seq, void *v)
278 {
279         return;
280 }
281 
282 static int synproxy_cpu_seq_show(struct seq_file *seq, void *v)
283 {
284         struct synproxy_stats *stats = v;
285 
286         if (v == SEQ_START_TOKEN) {
287                 seq_printf(seq, "entries\t\tsyn_received\t"
288                                 "cookie_invalid\tcookie_valid\t"
289                                 "cookie_retrans\tconn_reopened\n");
290                 return 0;
291         }
292 
293         seq_printf(seq, "%08x\t%08x\t%08x\t%08x\t%08x\t%08x\n", 0,
294                    stats->syn_received,
295                    stats->cookie_invalid,
296                    stats->cookie_valid,
297                    stats->cookie_retrans,
298                    stats->conn_reopened);
299 
300         return 0;
301 }
302 
303 static const struct seq_operations synproxy_cpu_seq_ops = {
304         .start          = synproxy_cpu_seq_start,
305         .next           = synproxy_cpu_seq_next,
306         .stop           = synproxy_cpu_seq_stop,
307         .show           = synproxy_cpu_seq_show,
308 };
309 
310 static int synproxy_cpu_seq_open(struct inode *inode, struct file *file)
311 {
312         return seq_open_net(inode, file, &synproxy_cpu_seq_ops,
313                             sizeof(struct seq_net_private));
314 }
315 
316 static const struct file_operations synproxy_cpu_seq_fops = {
317         .owner          = THIS_MODULE,
318         .open           = synproxy_cpu_seq_open,
319         .read           = seq_read,
320         .llseek         = seq_lseek,
321         .release        = seq_release_net,
322 };
323 
324 static int __net_init synproxy_proc_init(struct net *net)
325 {
326         if (!proc_create("synproxy", S_IRUGO, net->proc_net_stat,
327                          &synproxy_cpu_seq_fops))
328                 return -ENOMEM;
329         return 0;
330 }
331 
332 static void __net_exit synproxy_proc_exit(struct net *net)
333 {
334         remove_proc_entry("synproxy", net->proc_net_stat);
335 }
336 #else
337 static int __net_init synproxy_proc_init(struct net *net)
338 {
339         return 0;
340 }
341 
342 static void __net_exit synproxy_proc_exit(struct net *net)
343 {
344         return;
345 }
346 #endif /* CONFIG_PROC_FS */
347 
348 static int __net_init synproxy_net_init(struct net *net)
349 {
350         struct synproxy_net *snet = synproxy_pernet(net);
351         struct nf_conntrack_tuple t;
352         struct nf_conn *ct;
353         int err = -ENOMEM;
354 
355         memset(&t, 0, sizeof(t));
356         ct = nf_conntrack_alloc(net, 0, &t, &t, GFP_KERNEL);
357         if (IS_ERR(ct)) {
358                 err = PTR_ERR(ct);
359                 goto err1;
360         }
361 
362         if (!nfct_seqadj_ext_add(ct))
363                 goto err2;
364         if (!nfct_synproxy_ext_add(ct))
365                 goto err2;
366 
367         nf_conntrack_tmpl_insert(net, ct);
368         snet->tmpl = ct;
369 
370         snet->stats = alloc_percpu(struct synproxy_stats);
371         if (snet->stats == NULL)
372                 goto err2;
373 
374         err = synproxy_proc_init(net);
375         if (err < 0)
376                 goto err3;
377 
378         return 0;
379 
380 err3:
381         free_percpu(snet->stats);
382 err2:
383         nf_conntrack_free(ct);
384 err1:
385         return err;
386 }
387 
388 static void __net_exit synproxy_net_exit(struct net *net)
389 {
390         struct synproxy_net *snet = synproxy_pernet(net);
391 
392         nf_ct_put(snet->tmpl);
393         synproxy_proc_exit(net);
394         free_percpu(snet->stats);
395 }
396 
397 static struct pernet_operations synproxy_net_ops = {
398         .init           = synproxy_net_init,
399         .exit           = synproxy_net_exit,
400         .id             = &synproxy_net_id,
401         .size           = sizeof(struct synproxy_net),
402 };
403 
404 static int __init synproxy_core_init(void)
405 {
406         int err;
407 
408         err = nf_ct_extend_register(&nf_ct_synproxy_extend);
409         if (err < 0)
410                 goto err1;
411 
412         err = register_pernet_subsys(&synproxy_net_ops);
413         if (err < 0)
414                 goto err2;
415 
416         return 0;
417 
418 err2:
419         nf_ct_extend_unregister(&nf_ct_synproxy_extend);
420 err1:
421         return err;
422 }
423 
424 static void __exit synproxy_core_exit(void)
425 {
426         unregister_pernet_subsys(&synproxy_net_ops);
427         nf_ct_extend_unregister(&nf_ct_synproxy_extend);
428 }
429 
430 module_init(synproxy_core_init);
431 module_exit(synproxy_core_exit);
432 
433 MODULE_LICENSE("GPL");
434 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
435 

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