1/* SPDX-License-Identifier: GPL-2.0 */
2#include <linux/types.h>
3#include <linux/ip.h>
4#include <linux/netfilter.h>
5#include <linux/netfilter_ipv6.h>
6#include <linux/netfilter_bridge.h>
7#include <linux/module.h>
8#include <linux/skbuff.h>
9#include <linux/icmp.h>
10#include <linux/sysctl.h>
11#include <net/route.h>
12#include <net/ip.h>
13
14#include <net/netfilter/nf_conntrack.h>
15#include <net/netfilter/nf_conntrack_core.h>
16#include <net/netfilter/nf_conntrack_helper.h>
17#include <net/netfilter/nf_conntrack_bridge.h>
18
19#include <linux/netfilter/nf_tables.h>
20#include <net/netfilter/nf_tables.h>
21
22#include "../br_private.h"
23
24/* Best effort variant of ip_do_fragment which preserves geometry, unless skbuff
25 * has been linearized or cloned.
26 */
27static int nf_br_ip_fragment(struct net *net, struct sock *sk,
28 struct sk_buff *skb,
29 struct nf_bridge_frag_data *data,
30 int (*output)(struct net *, struct sock *sk,
31 const struct nf_bridge_frag_data *data,
32 struct sk_buff *))
33{
34 int frag_max_size = BR_INPUT_SKB_CB(skb)->frag_max_size;
35 u8 tstamp_type = skb->tstamp_type;
36 unsigned int hlen, ll_rs, mtu;
37 ktime_t tstamp = skb->tstamp;
38 struct ip_frag_state state;
39 struct iphdr *iph;
40 int err = 0;
41
42 /* for offloaded checksums cleanup checksum before fragmentation */
43 if (skb->ip_summed == CHECKSUM_PARTIAL &&
44 (err = skb_checksum_help(skb)))
45 goto blackhole;
46
47 iph = ip_hdr(skb);
48
49 /*
50 * Setup starting values
51 */
52
53 hlen = iph->ihl * 4;
54 frag_max_size -= hlen;
55 ll_rs = LL_RESERVED_SPACE(skb->dev);
56 mtu = skb->dev->mtu;
57
58 if (skb_has_frag_list(skb)) {
59 unsigned int first_len = skb_pagelen(skb);
60 struct ip_fraglist_iter iter;
61 struct sk_buff *frag;
62
63 if (first_len - hlen > mtu)
64 goto blackhole;
65
66 if (skb_cloned(skb) ||
67 skb_headroom(skb) < ll_rs)
68 goto slow_path;
69
70 skb_walk_frags(skb, frag) {
71 if (frag->len > mtu)
72 goto blackhole;
73
74 if (skb_shared(skb: frag) ||
75 skb_headroom(skb: frag) < hlen + ll_rs)
76 goto slow_path;
77 }
78
79 ip_fraglist_init(skb, iph, hlen, iter: &iter);
80
81 for (;;) {
82 if (iter.frag)
83 ip_fraglist_prepare(skb, iter: &iter);
84
85 skb_set_delivery_time(skb, kt: tstamp, tstamp_type);
86 err = output(net, sk, data, skb);
87 if (err || !iter.frag)
88 break;
89
90 skb = ip_fraglist_next(iter: &iter);
91 }
92
93 if (!err)
94 return 0;
95
96 kfree_skb_list(segs: iter.frag);
97
98 return err;
99 }
100slow_path:
101 /* This is a linearized skbuff, the original geometry is lost for us.
102 * This may also be a clone skbuff, we could preserve the geometry for
103 * the copies but probably not worth the effort.
104 */
105 ip_frag_init(skb, hlen, ll_rs, mtu: frag_max_size, DF: false, state: &state);
106
107 while (state.left > 0) {
108 struct sk_buff *skb2;
109
110 skb2 = ip_frag_next(skb, state: &state);
111 if (IS_ERR(ptr: skb2)) {
112 err = PTR_ERR(ptr: skb2);
113 goto blackhole;
114 }
115
116 skb_set_delivery_time(skb: skb2, kt: tstamp, tstamp_type);
117 err = output(net, sk, data, skb2);
118 if (err)
119 goto blackhole;
120 }
121 consume_skb(skb);
122 return err;
123
124blackhole:
125 kfree_skb(skb);
126 return 0;
127}
128
129/* ip_defrag() expects IPCB() in place. */
130static void br_skb_cb_save(struct sk_buff *skb, struct br_input_skb_cb *cb,
131 size_t inet_skb_parm_size)
132{
133 memcpy(cb, skb->cb, sizeof(*cb));
134 memset(skb->cb, 0, inet_skb_parm_size);
135}
136
137static void br_skb_cb_restore(struct sk_buff *skb,
138 const struct br_input_skb_cb *cb,
139 u16 fragsz)
140{
141 memcpy(skb->cb, cb, sizeof(*cb));
142 BR_INPUT_SKB_CB(skb)->frag_max_size = fragsz;
143}
144
145static unsigned int nf_ct_br_defrag4(struct sk_buff *skb,
146 const struct nf_hook_state *state)
147{
148 u16 zone_id = NF_CT_DEFAULT_ZONE_ID;
149 enum ip_conntrack_info ctinfo;
150 struct br_input_skb_cb cb;
151 const struct nf_conn *ct;
152 int err;
153
154 if (!ip_is_fragment(iph: ip_hdr(skb)))
155 return NF_ACCEPT;
156
157 ct = nf_ct_get(skb, ctinfo: &ctinfo);
158 if (ct)
159 zone_id = nf_ct_zone_id(zone: nf_ct_zone(ct), CTINFO2DIR(ctinfo));
160
161 br_skb_cb_save(skb, cb: &cb, inet_skb_parm_size: sizeof(struct inet_skb_parm));
162 local_bh_disable();
163 err = ip_defrag(net: state->net, skb,
164 user: IP_DEFRAG_CONNTRACK_BRIDGE_IN + zone_id);
165 local_bh_enable();
166 if (!err) {
167 br_skb_cb_restore(skb, cb: &cb, IPCB(skb)->frag_max_size);
168 skb->ignore_df = 1;
169 return NF_ACCEPT;
170 }
171
172 return NF_STOLEN;
173}
174
175static unsigned int nf_ct_br_defrag6(struct sk_buff *skb,
176 const struct nf_hook_state *state)
177{
178#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
179 u16 zone_id = NF_CT_DEFAULT_ZONE_ID;
180 enum ip_conntrack_info ctinfo;
181 struct br_input_skb_cb cb;
182 const struct nf_conn *ct;
183 int err;
184
185 ct = nf_ct_get(skb, ctinfo: &ctinfo);
186 if (ct)
187 zone_id = nf_ct_zone_id(zone: nf_ct_zone(ct), CTINFO2DIR(ctinfo));
188
189 br_skb_cb_save(skb, cb: &cb, inet_skb_parm_size: sizeof(struct inet6_skb_parm));
190
191 err = nf_ct_frag6_gather(net: state->net, skb,
192 user: IP_DEFRAG_CONNTRACK_BRIDGE_IN + zone_id);
193 /* queued */
194 if (err == -EINPROGRESS)
195 return NF_STOLEN;
196
197 br_skb_cb_restore(skb, cb: &cb, IP6CB(skb)->frag_max_size);
198 return err == 0 ? NF_ACCEPT : NF_DROP;
199#else
200 return NF_ACCEPT;
201#endif
202}
203
204static int nf_ct_br_ip_check(const struct sk_buff *skb)
205{
206 const struct iphdr *iph;
207 int nhoff, len;
208
209 nhoff = skb_network_offset(skb);
210 iph = ip_hdr(skb);
211 if (iph->ihl < 5 ||
212 iph->version != 4)
213 return -1;
214
215 len = skb_ip_totlen(skb);
216 if (skb->len < nhoff + len ||
217 len < (iph->ihl * 4))
218 return -1;
219
220 return 0;
221}
222
223static int nf_ct_br_ipv6_check(const struct sk_buff *skb)
224{
225 const struct ipv6hdr *hdr;
226 int nhoff, len;
227
228 nhoff = skb_network_offset(skb);
229 hdr = ipv6_hdr(skb);
230 if (hdr->version != 6)
231 return -1;
232
233 len = ntohs(hdr->payload_len) + sizeof(struct ipv6hdr) + nhoff;
234 if (skb->len < len)
235 return -1;
236
237 return 0;
238}
239
240static unsigned int nf_ct_bridge_pre(void *priv, struct sk_buff *skb,
241 const struct nf_hook_state *state)
242{
243 struct nf_hook_state bridge_state = *state;
244 enum ip_conntrack_info ctinfo;
245 struct nf_conn *ct;
246 u32 len;
247 int ret;
248
249 ct = nf_ct_get(skb, ctinfo: &ctinfo);
250 if ((ct && !nf_ct_is_template(ct)) ||
251 ctinfo == IP_CT_UNTRACKED)
252 return NF_ACCEPT;
253
254 switch (skb->protocol) {
255 case htons(ETH_P_IP):
256 if (!pskb_may_pull(skb, len: sizeof(struct iphdr)))
257 return NF_ACCEPT;
258
259 len = skb_ip_totlen(skb);
260 if (pskb_trim_rcsum(skb, len))
261 return NF_ACCEPT;
262
263 if (nf_ct_br_ip_check(skb))
264 return NF_ACCEPT;
265
266 bridge_state.pf = NFPROTO_IPV4;
267 ret = nf_ct_br_defrag4(skb, state: &bridge_state);
268 break;
269 case htons(ETH_P_IPV6):
270 if (!pskb_may_pull(skb, len: sizeof(struct ipv6hdr)))
271 return NF_ACCEPT;
272
273 len = sizeof(struct ipv6hdr) + ntohs(ipv6_hdr(skb)->payload_len);
274 if (pskb_trim_rcsum(skb, len))
275 return NF_ACCEPT;
276
277 if (nf_ct_br_ipv6_check(skb))
278 return NF_ACCEPT;
279
280 bridge_state.pf = NFPROTO_IPV6;
281 ret = nf_ct_br_defrag6(skb, state: &bridge_state);
282 break;
283 default:
284 nf_ct_set(skb, NULL, info: IP_CT_UNTRACKED);
285 return NF_ACCEPT;
286 }
287
288 if (ret != NF_ACCEPT)
289 return ret;
290
291 return nf_conntrack_in(skb, state: &bridge_state);
292}
293
294static unsigned int nf_ct_bridge_in(void *priv, struct sk_buff *skb,
295 const struct nf_hook_state *state)
296{
297 bool promisc = BR_INPUT_SKB_CB(skb)->promisc;
298 struct nf_conntrack *nfct = skb_nfct(skb);
299 struct nf_conn *ct;
300
301 if (promisc) {
302 nf_reset_ct(skb);
303 return NF_ACCEPT;
304 }
305
306 if (!nfct || skb->pkt_type == PACKET_HOST)
307 return NF_ACCEPT;
308
309 /* nf_conntrack_confirm() cannot handle concurrent clones,
310 * this happens for broad/multicast frames with e.g. macvlan on top
311 * of the bridge device.
312 */
313 ct = container_of(nfct, struct nf_conn, ct_general);
314 if (nf_ct_is_confirmed(ct) || nf_ct_is_template(ct))
315 return NF_ACCEPT;
316
317 /* let inet prerouting call conntrack again */
318 skb->_nfct = 0;
319 nf_ct_put(ct);
320
321 return NF_ACCEPT;
322}
323
324static void nf_ct_bridge_frag_save(struct sk_buff *skb,
325 struct nf_bridge_frag_data *data)
326{
327 if (skb_vlan_tag_present(skb)) {
328 data->vlan_present = true;
329 data->vlan_tci = skb->vlan_tci;
330 data->vlan_proto = skb->vlan_proto;
331 } else {
332 data->vlan_present = false;
333 }
334 skb_copy_from_linear_data_offset(skb, offset: -ETH_HLEN, to: data->mac, ETH_HLEN);
335}
336
337static unsigned int
338nf_ct_bridge_refrag(struct sk_buff *skb, const struct nf_hook_state *state,
339 int (*output)(struct net *, struct sock *sk,
340 const struct nf_bridge_frag_data *data,
341 struct sk_buff *))
342{
343 struct nf_bridge_frag_data data;
344
345 if (!BR_INPUT_SKB_CB(skb)->frag_max_size)
346 return NF_ACCEPT;
347
348 nf_ct_bridge_frag_save(skb, data: &data);
349 switch (skb->protocol) {
350 case htons(ETH_P_IP):
351 nf_br_ip_fragment(net: state->net, sk: state->sk, skb, data: &data, output);
352 break;
353 case htons(ETH_P_IPV6):
354 nf_br_ip6_fragment(net: state->net, sk: state->sk, skb, data: &data, output);
355 break;
356 default:
357 WARN_ON_ONCE(1);
358 return NF_DROP;
359 }
360
361 return NF_STOLEN;
362}
363
364/* Actually only slow path refragmentation needs this. */
365static int nf_ct_bridge_frag_restore(struct sk_buff *skb,
366 const struct nf_bridge_frag_data *data)
367{
368 int err;
369
370 err = skb_cow_head(skb, ETH_HLEN);
371 if (err) {
372 kfree_skb(skb);
373 return -ENOMEM;
374 }
375 if (data->vlan_present)
376 __vlan_hwaccel_put_tag(skb, vlan_proto: data->vlan_proto, vlan_tci: data->vlan_tci);
377 else if (skb_vlan_tag_present(skb))
378 __vlan_hwaccel_clear_tag(skb);
379
380 skb_copy_to_linear_data_offset(skb, offset: -ETH_HLEN, from: data->mac, ETH_HLEN);
381 skb_reset_mac_header(skb);
382
383 return 0;
384}
385
386static int nf_ct_bridge_refrag_post(struct net *net, struct sock *sk,
387 const struct nf_bridge_frag_data *data,
388 struct sk_buff *skb)
389{
390 int err;
391
392 err = nf_ct_bridge_frag_restore(skb, data);
393 if (err < 0)
394 return err;
395
396 return br_dev_queue_push_xmit(net, sk, skb);
397}
398
399static unsigned int nf_ct_bridge_post(void *priv, struct sk_buff *skb,
400 const struct nf_hook_state *state)
401{
402 int ret;
403
404 ret = nf_confirm(priv, skb, state);
405 if (ret != NF_ACCEPT)
406 return ret;
407
408 return nf_ct_bridge_refrag(skb, state, output: nf_ct_bridge_refrag_post);
409}
410
411static struct nf_hook_ops nf_ct_bridge_hook_ops[] __read_mostly = {
412 {
413 .hook = nf_ct_bridge_pre,
414 .pf = NFPROTO_BRIDGE,
415 .hooknum = NF_BR_PRE_ROUTING,
416 .priority = NF_IP_PRI_CONNTRACK,
417 },
418 {
419 .hook = nf_ct_bridge_in,
420 .pf = NFPROTO_BRIDGE,
421 .hooknum = NF_BR_LOCAL_IN,
422 .priority = NF_IP_PRI_CONNTRACK_CONFIRM,
423 },
424 {
425 .hook = nf_ct_bridge_post,
426 .pf = NFPROTO_BRIDGE,
427 .hooknum = NF_BR_POST_ROUTING,
428 .priority = NF_IP_PRI_CONNTRACK_CONFIRM,
429 },
430};
431
432static struct nf_ct_bridge_info bridge_info = {
433 .ops = nf_ct_bridge_hook_ops,
434 .ops_size = ARRAY_SIZE(nf_ct_bridge_hook_ops),
435 .me = THIS_MODULE,
436};
437
438static int __init nf_conntrack_l3proto_bridge_init(void)
439{
440 nf_ct_bridge_register(info: &bridge_info);
441
442 return 0;
443}
444
445static void __exit nf_conntrack_l3proto_bridge_fini(void)
446{
447 nf_ct_bridge_unregister(info: &bridge_info);
448}
449
450module_init(nf_conntrack_l3proto_bridge_init);
451module_exit(nf_conntrack_l3proto_bridge_fini);
452
453MODULE_ALIAS("nf_conntrack-" __stringify(AF_BRIDGE));
454MODULE_LICENSE("GPL");
455MODULE_DESCRIPTION("Bridge IPv4 and IPv6 connection tracking");
456

source code of linux/net/bridge/netfilter/nf_conntrack_bridge.c