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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> | |
10c04a8e | 14 | #include <linux/proc_fs.h> |
48b1de4c PM |
15 | |
16 | #include <linux/netfilter_ipv4/ip_tables.h> | |
17 | #include <linux/netfilter/x_tables.h> | |
18 | #include <linux/netfilter/xt_tcpudp.h> | |
19 | #include <linux/netfilter/xt_SYNPROXY.h> | |
308ac914 | 20 | |
48b1de4c PM |
21 | #include <net/netfilter/nf_conntrack.h> |
22 | #include <net/netfilter/nf_conntrack_extend.h> | |
23 | #include <net/netfilter/nf_conntrack_seqadj.h> | |
24 | #include <net/netfilter/nf_conntrack_synproxy.h> | |
308ac914 | 25 | #include <net/netfilter/nf_conntrack_zones.h> |
48b1de4c | 26 | |
c7d03a00 | 27 | unsigned int synproxy_net_id; |
48b1de4c PM |
28 | EXPORT_SYMBOL_GPL(synproxy_net_id); |
29 | ||
f4a87e7b | 30 | bool |
48b1de4c PM |
31 | synproxy_parse_options(const struct sk_buff *skb, unsigned int doff, |
32 | const struct tcphdr *th, struct synproxy_options *opts) | |
33 | { | |
34 | int length = (th->doff * 4) - sizeof(*th); | |
35 | u8 buf[40], *ptr; | |
36 | ||
37 | ptr = skb_header_pointer(skb, doff + sizeof(*th), length, buf); | |
f4a87e7b PM |
38 | if (ptr == NULL) |
39 | return false; | |
48b1de4c PM |
40 | |
41 | opts->options = 0; | |
42 | while (length > 0) { | |
43 | int opcode = *ptr++; | |
44 | int opsize; | |
45 | ||
46 | switch (opcode) { | |
47 | case TCPOPT_EOL: | |
f4a87e7b | 48 | return true; |
48b1de4c PM |
49 | case TCPOPT_NOP: |
50 | length--; | |
51 | continue; | |
52 | default: | |
53 | opsize = *ptr++; | |
54 | if (opsize < 2) | |
f4a87e7b | 55 | return true; |
48b1de4c | 56 | if (opsize > length) |
f4a87e7b | 57 | return true; |
48b1de4c PM |
58 | |
59 | switch (opcode) { | |
60 | case TCPOPT_MSS: | |
61 | if (opsize == TCPOLEN_MSS) { | |
62 | opts->mss = get_unaligned_be16(ptr); | |
63 | opts->options |= XT_SYNPROXY_OPT_MSS; | |
64 | } | |
65 | break; | |
66 | case TCPOPT_WINDOW: | |
67 | if (opsize == TCPOLEN_WINDOW) { | |
68 | opts->wscale = *ptr; | |
122868b3 GF |
69 | if (opts->wscale > TCP_MAX_WSCALE) |
70 | opts->wscale = TCP_MAX_WSCALE; | |
48b1de4c PM |
71 | opts->options |= XT_SYNPROXY_OPT_WSCALE; |
72 | } | |
73 | break; | |
74 | case TCPOPT_TIMESTAMP: | |
75 | if (opsize == TCPOLEN_TIMESTAMP) { | |
76 | opts->tsval = get_unaligned_be32(ptr); | |
77 | opts->tsecr = get_unaligned_be32(ptr + 4); | |
78 | opts->options |= XT_SYNPROXY_OPT_TIMESTAMP; | |
79 | } | |
80 | break; | |
81 | case TCPOPT_SACK_PERM: | |
82 | if (opsize == TCPOLEN_SACK_PERM) | |
83 | opts->options |= XT_SYNPROXY_OPT_SACK_PERM; | |
84 | break; | |
85 | } | |
86 | ||
87 | ptr += opsize - 2; | |
88 | length -= opsize; | |
89 | } | |
90 | } | |
f4a87e7b | 91 | return true; |
48b1de4c PM |
92 | } |
93 | EXPORT_SYMBOL_GPL(synproxy_parse_options); | |
94 | ||
95 | unsigned int synproxy_options_size(const struct synproxy_options *opts) | |
96 | { | |
97 | unsigned int size = 0; | |
98 | ||
99 | if (opts->options & XT_SYNPROXY_OPT_MSS) | |
100 | size += TCPOLEN_MSS_ALIGNED; | |
101 | if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP) | |
102 | size += TCPOLEN_TSTAMP_ALIGNED; | |
103 | else if (opts->options & XT_SYNPROXY_OPT_SACK_PERM) | |
104 | size += TCPOLEN_SACKPERM_ALIGNED; | |
105 | if (opts->options & XT_SYNPROXY_OPT_WSCALE) | |
106 | size += TCPOLEN_WSCALE_ALIGNED; | |
107 | ||
108 | return size; | |
109 | } | |
110 | EXPORT_SYMBOL_GPL(synproxy_options_size); | |
111 | ||
112 | void | |
113 | synproxy_build_options(struct tcphdr *th, const struct synproxy_options *opts) | |
114 | { | |
115 | __be32 *ptr = (__be32 *)(th + 1); | |
116 | u8 options = opts->options; | |
117 | ||
118 | if (options & XT_SYNPROXY_OPT_MSS) | |
119 | *ptr++ = htonl((TCPOPT_MSS << 24) | | |
120 | (TCPOLEN_MSS << 16) | | |
121 | opts->mss); | |
122 | ||
123 | if (options & XT_SYNPROXY_OPT_TIMESTAMP) { | |
124 | if (options & XT_SYNPROXY_OPT_SACK_PERM) | |
125 | *ptr++ = htonl((TCPOPT_SACK_PERM << 24) | | |
126 | (TCPOLEN_SACK_PERM << 16) | | |
127 | (TCPOPT_TIMESTAMP << 8) | | |
128 | TCPOLEN_TIMESTAMP); | |
129 | else | |
130 | *ptr++ = htonl((TCPOPT_NOP << 24) | | |
131 | (TCPOPT_NOP << 16) | | |
132 | (TCPOPT_TIMESTAMP << 8) | | |
133 | TCPOLEN_TIMESTAMP); | |
134 | ||
135 | *ptr++ = htonl(opts->tsval); | |
136 | *ptr++ = htonl(opts->tsecr); | |
137 | } else if (options & XT_SYNPROXY_OPT_SACK_PERM) | |
138 | *ptr++ = htonl((TCPOPT_NOP << 24) | | |
139 | (TCPOPT_NOP << 16) | | |
140 | (TCPOPT_SACK_PERM << 8) | | |
141 | TCPOLEN_SACK_PERM); | |
142 | ||
143 | if (options & XT_SYNPROXY_OPT_WSCALE) | |
144 | *ptr++ = htonl((TCPOPT_NOP << 24) | | |
145 | (TCPOPT_WINDOW << 16) | | |
146 | (TCPOLEN_WINDOW << 8) | | |
147 | opts->wscale); | |
148 | } | |
149 | EXPORT_SYMBOL_GPL(synproxy_build_options); | |
150 | ||
151 | void synproxy_init_timestamp_cookie(const struct xt_synproxy_info *info, | |
152 | struct synproxy_options *opts) | |
153 | { | |
154 | opts->tsecr = opts->tsval; | |
9a568de4 | 155 | opts->tsval = tcp_time_stamp_raw() & ~0x3f; |
48b1de4c | 156 | |
c1898c4c MT |
157 | if (opts->options & XT_SYNPROXY_OPT_WSCALE) { |
158 | opts->tsval |= opts->wscale; | |
159 | opts->wscale = info->wscale; | |
160 | } else | |
48b1de4c PM |
161 | opts->tsval |= 0xf; |
162 | ||
163 | if (opts->options & XT_SYNPROXY_OPT_SACK_PERM) | |
164 | opts->tsval |= 1 << 4; | |
165 | ||
166 | if (opts->options & XT_SYNPROXY_OPT_ECN) | |
167 | opts->tsval |= 1 << 5; | |
168 | } | |
169 | EXPORT_SYMBOL_GPL(synproxy_init_timestamp_cookie); | |
170 | ||
171 | void synproxy_check_timestamp_cookie(struct synproxy_options *opts) | |
172 | { | |
173 | opts->wscale = opts->tsecr & 0xf; | |
174 | if (opts->wscale != 0xf) | |
175 | opts->options |= XT_SYNPROXY_OPT_WSCALE; | |
176 | ||
177 | opts->options |= opts->tsecr & (1 << 4) ? XT_SYNPROXY_OPT_SACK_PERM : 0; | |
178 | ||
179 | opts->options |= opts->tsecr & (1 << 5) ? XT_SYNPROXY_OPT_ECN : 0; | |
180 | } | |
181 | EXPORT_SYMBOL_GPL(synproxy_check_timestamp_cookie); | |
182 | ||
183 | unsigned int synproxy_tstamp_adjust(struct sk_buff *skb, | |
184 | unsigned int protoff, | |
185 | struct tcphdr *th, | |
186 | struct nf_conn *ct, | |
187 | enum ip_conntrack_info ctinfo, | |
188 | const struct nf_conn_synproxy *synproxy) | |
189 | { | |
190 | unsigned int optoff, optend; | |
851345c5 | 191 | __be32 *ptr, old; |
48b1de4c PM |
192 | |
193 | if (synproxy->tsoff == 0) | |
194 | return 1; | |
195 | ||
196 | optoff = protoff + sizeof(struct tcphdr); | |
197 | optend = protoff + th->doff * 4; | |
198 | ||
199 | if (!skb_make_writable(skb, optend)) | |
200 | return 0; | |
201 | ||
202 | while (optoff < optend) { | |
203 | unsigned char *op = skb->data + optoff; | |
204 | ||
205 | switch (op[0]) { | |
206 | case TCPOPT_EOL: | |
207 | return 1; | |
208 | case TCPOPT_NOP: | |
209 | optoff++; | |
210 | continue; | |
211 | default: | |
212 | if (optoff + 1 == optend || | |
213 | optoff + op[1] > optend || | |
214 | op[1] < 2) | |
215 | return 0; | |
216 | if (op[0] == TCPOPT_TIMESTAMP && | |
217 | op[1] == TCPOLEN_TIMESTAMP) { | |
218 | if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) { | |
851345c5 | 219 | ptr = (__be32 *)&op[2]; |
48b1de4c PM |
220 | old = *ptr; |
221 | *ptr = htonl(ntohl(*ptr) - | |
222 | synproxy->tsoff); | |
223 | } else { | |
851345c5 | 224 | ptr = (__be32 *)&op[6]; |
48b1de4c PM |
225 | old = *ptr; |
226 | *ptr = htonl(ntohl(*ptr) + | |
227 | synproxy->tsoff); | |
228 | } | |
229 | inet_proto_csum_replace4(&th->check, skb, | |
4b048d6d | 230 | old, *ptr, false); |
48b1de4c PM |
231 | return 1; |
232 | } | |
233 | optoff += op[1]; | |
234 | } | |
235 | } | |
236 | return 1; | |
237 | } | |
238 | EXPORT_SYMBOL_GPL(synproxy_tstamp_adjust); | |
239 | ||
240 | static struct nf_ct_ext_type nf_ct_synproxy_extend __read_mostly = { | |
241 | .len = sizeof(struct nf_conn_synproxy), | |
242 | .align = __alignof__(struct nf_conn_synproxy), | |
243 | .id = NF_CT_EXT_SYNPROXY, | |
244 | }; | |
245 | ||
246 | #ifdef CONFIG_PROC_FS | |
247 | static void *synproxy_cpu_seq_start(struct seq_file *seq, loff_t *pos) | |
248 | { | |
249 | struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq)); | |
250 | int cpu; | |
251 | ||
252 | if (*pos == 0) | |
253 | return SEQ_START_TOKEN; | |
254 | ||
255 | for (cpu = *pos - 1; cpu < nr_cpu_ids; cpu++) { | |
256 | if (!cpu_possible(cpu)) | |
257 | continue; | |
258 | *pos = cpu + 1; | |
259 | return per_cpu_ptr(snet->stats, cpu); | |
260 | } | |
261 | ||
262 | return NULL; | |
263 | } | |
264 | ||
265 | static void *synproxy_cpu_seq_next(struct seq_file *seq, void *v, loff_t *pos) | |
266 | { | |
267 | struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq)); | |
268 | int cpu; | |
269 | ||
270 | for (cpu = *pos; cpu < nr_cpu_ids; cpu++) { | |
271 | if (!cpu_possible(cpu)) | |
272 | continue; | |
273 | *pos = cpu + 1; | |
274 | return per_cpu_ptr(snet->stats, cpu); | |
275 | } | |
276 | ||
277 | return NULL; | |
278 | } | |
279 | ||
280 | static void synproxy_cpu_seq_stop(struct seq_file *seq, void *v) | |
281 | { | |
282 | return; | |
283 | } | |
284 | ||
285 | static int synproxy_cpu_seq_show(struct seq_file *seq, void *v) | |
286 | { | |
287 | struct synproxy_stats *stats = v; | |
288 | ||
289 | if (v == SEQ_START_TOKEN) { | |
cdec2685 | 290 | seq_puts(seq, "entries\t\tsyn_received\t" |
291 | "cookie_invalid\tcookie_valid\t" | |
292 | "cookie_retrans\tconn_reopened\n"); | |
48b1de4c PM |
293 | return 0; |
294 | } | |
295 | ||
296 | seq_printf(seq, "%08x\t%08x\t%08x\t%08x\t%08x\t%08x\n", 0, | |
297 | stats->syn_received, | |
298 | stats->cookie_invalid, | |
299 | stats->cookie_valid, | |
300 | stats->cookie_retrans, | |
301 | stats->conn_reopened); | |
302 | ||
303 | return 0; | |
304 | } | |
305 | ||
306 | static const struct seq_operations synproxy_cpu_seq_ops = { | |
307 | .start = synproxy_cpu_seq_start, | |
308 | .next = synproxy_cpu_seq_next, | |
309 | .stop = synproxy_cpu_seq_stop, | |
310 | .show = synproxy_cpu_seq_show, | |
311 | }; | |
312 | ||
313 | static int synproxy_cpu_seq_open(struct inode *inode, struct file *file) | |
314 | { | |
315 | return seq_open_net(inode, file, &synproxy_cpu_seq_ops, | |
316 | sizeof(struct seq_net_private)); | |
317 | } | |
318 | ||
319 | static const struct file_operations synproxy_cpu_seq_fops = { | |
320 | .owner = THIS_MODULE, | |
321 | .open = synproxy_cpu_seq_open, | |
322 | .read = seq_read, | |
323 | .llseek = seq_lseek, | |
324 | .release = seq_release_net, | |
325 | }; | |
326 | ||
327 | static int __net_init synproxy_proc_init(struct net *net) | |
328 | { | |
329 | if (!proc_create("synproxy", S_IRUGO, net->proc_net_stat, | |
330 | &synproxy_cpu_seq_fops)) | |
331 | return -ENOMEM; | |
332 | return 0; | |
333 | } | |
334 | ||
335 | static void __net_exit synproxy_proc_exit(struct net *net) | |
336 | { | |
337 | remove_proc_entry("synproxy", net->proc_net_stat); | |
338 | } | |
339 | #else | |
340 | static int __net_init synproxy_proc_init(struct net *net) | |
341 | { | |
342 | return 0; | |
343 | } | |
344 | ||
345 | static void __net_exit synproxy_proc_exit(struct net *net) | |
346 | { | |
347 | return; | |
348 | } | |
349 | #endif /* CONFIG_PROC_FS */ | |
350 | ||
351 | static int __net_init synproxy_net_init(struct net *net) | |
352 | { | |
353 | struct synproxy_net *snet = synproxy_pernet(net); | |
48b1de4c PM |
354 | struct nf_conn *ct; |
355 | int err = -ENOMEM; | |
356 | ||
308ac914 | 357 | ct = nf_ct_tmpl_alloc(net, &nf_ct_zone_dflt, GFP_KERNEL); |
1a727c63 | 358 | if (!ct) |
48b1de4c | 359 | goto err1; |
48b1de4c | 360 | |
48b1de4c PM |
361 | if (!nfct_seqadj_ext_add(ct)) |
362 | goto err2; | |
363 | if (!nfct_synproxy_ext_add(ct)) | |
364 | goto err2; | |
365 | ||
0838aa7f PNA |
366 | __set_bit(IPS_CONFIRMED_BIT, &ct->status); |
367 | nf_conntrack_get(&ct->ct_general); | |
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: | |
9cf94eab | 383 | nf_ct_tmpl_free(ct); |
48b1de4c PM |
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>"); |