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48b1de4c PM |
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 | ||
f4a87e7b | 27 | bool |
48b1de4c PM |
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); | |
f4a87e7b PM |
35 | if (ptr == NULL) |
36 | return false; | |
48b1de4c PM |
37 | |
38 | opts->options = 0; | |
39 | while (length > 0) { | |
40 | int opcode = *ptr++; | |
41 | int opsize; | |
42 | ||
43 | switch (opcode) { | |
44 | case TCPOPT_EOL: | |
f4a87e7b | 45 | return true; |
48b1de4c PM |
46 | case TCPOPT_NOP: |
47 | length--; | |
48 | continue; | |
49 | default: | |
50 | opsize = *ptr++; | |
51 | if (opsize < 2) | |
f4a87e7b | 52 | return true; |
48b1de4c | 53 | if (opsize > length) |
f4a87e7b | 54 | return true; |
48b1de4c PM |
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 | } | |
f4a87e7b | 88 | return true; |
48b1de4c PM |
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 | ||
c1898c4c MT |
154 | if (opts->options & XT_SYNPROXY_OPT_WSCALE) { |
155 | opts->tsval |= opts->wscale; | |
156 | opts->wscale = info->wscale; | |
157 | } else | |
48b1de4c PM |
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 | ||
48b1de4c PM |
362 | if (!nfct_seqadj_ext_add(ct)) |
363 | goto err2; | |
364 | if (!nfct_synproxy_ext_add(ct)) | |
365 | goto err2; | |
366 | ||
e53376be | 367 | nf_conntrack_tmpl_insert(net, ct); |
48b1de4c PM |
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 | ||
e53376be | 392 | nf_ct_put(snet->tmpl); |
48b1de4c PM |
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>"); |