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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 | __set_bit(IPS_TEMPLATE_BIT, &ct->status); |
367 | __set_bit(IPS_CONFIRMED_BIT, &ct->status); |
368 | |
369 | snet->tmpl = ct; |
370 | |
371 | snet->stats = alloc_percpu(struct synproxy_stats); |
372 | if (snet->stats == NULL) |
373 | goto err2; |
374 | |
375 | err = synproxy_proc_init(net); |
376 | if (err < 0) |
377 | goto err3; |
378 | |
379 | return 0; |
380 | |
381 | err3: |
382 | free_percpu(snet->stats); |
383 | err2: |
384 | nf_conntrack_free(ct); |
385 | err1: |
386 | return err; |
387 | } |
388 | |
389 | static void __net_exit synproxy_net_exit(struct net *net) |
390 | { |
391 | struct synproxy_net *snet = synproxy_pernet(net); |
392 | |
393 | nf_conntrack_free(snet->tmpl); |
394 | synproxy_proc_exit(net); |
395 | free_percpu(snet->stats); |
396 | } |
397 | |
398 | static struct pernet_operations synproxy_net_ops = { |
399 | .init = synproxy_net_init, |
400 | .exit = synproxy_net_exit, |
401 | .id = &synproxy_net_id, |
402 | .size = sizeof(struct synproxy_net), |
403 | }; |
404 | |
405 | static int __init synproxy_core_init(void) |
406 | { |
407 | int err; |
408 | |
409 | err = nf_ct_extend_register(&nf_ct_synproxy_extend); |
410 | if (err < 0) |
411 | goto err1; |
412 | |
413 | err = register_pernet_subsys(&synproxy_net_ops); |
414 | if (err < 0) |
415 | goto err2; |
416 | |
417 | return 0; |
418 | |
419 | err2: |
420 | nf_ct_extend_unregister(&nf_ct_synproxy_extend); |
421 | err1: |
422 | return err; |
423 | } |
424 | |
425 | static void __exit synproxy_core_exit(void) |
426 | { |
427 | unregister_pernet_subsys(&synproxy_net_ops); |
428 | nf_ct_extend_unregister(&nf_ct_synproxy_extend); |
429 | } |
430 | |
431 | module_init(synproxy_core_init); |
432 | module_exit(synproxy_core_exit); |
433 | |
434 | MODULE_LICENSE("GPL"); |
435 | MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); |
436 |
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