net/bridge/netfilter/nf_conntrack_bridge.c

   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  */
  27 static 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         unsigned int hlen, ll_rs, mtu;
  36         ktime_t tstamp = skb->tstamp;
  37         struct ip_frag_state state;
  38         struct iphdr *iph;
  39         int err;
  40
  41         /* for offloaded checksums cleanup checksum before fragmentation */
  42         if (skb->ip_summed == CHECKSUM_PARTIAL &&
  43             (err = skb_checksum_help(skb)))
  44                 goto blackhole;
  45
  46         iph = ip_hdr(skb);
  47
  48         /*
  49          *      Setup starting values
  50          */
  51
  52         hlen = iph->ihl * 4;
  53         frag_max_size -= hlen;
  54         ll_rs = LL_RESERVED_SPACE(skb->dev);
  55         mtu = skb->dev->mtu;
  56
  57         if (skb_has_frag_list(skb)) {
  58                 unsigned int first_len = skb_pagelen(skb);
  59                 struct ip_fraglist_iter iter;
  60                 struct sk_buff *frag;
  61
  62                 if (first_len - hlen > mtu ||
  63                     skb_headroom(skb) < ll_rs)
  64                         goto blackhole;
  65
  66                 if (skb_cloned(skb))
  67                         goto slow_path;
  68
  69                 skb_walk_frags(skb, frag) {
  70                         if (frag->len > mtu ||
  71                             skb_headroom(frag) < hlen + ll_rs)
  72                                 goto blackhole;
  73
  74                         if (skb_shared(frag))
  75                                 goto slow_path;
  76                 }
  77
  78                 ip_fraglist_init(skb, iph, hlen, &iter);
  79
  80                 for (;;) {
  81                         if (iter.frag)
  82                                 ip_fraglist_prepare(skb, &iter);
  83
  84                         skb->tstamp = tstamp;
  85                         err = output(net, sk, data, skb);
  86                         if (err || !iter.frag)
  87                                 break;
  88
  89                         skb = ip_fraglist_next(&iter);
  90                 }
  91                 return err;
  92         }
  93 slow_path:
  94         /* This is a linearized skbuff, the original geometry is lost for us.
  95          * This may also be a clone skbuff, we could preserve the geometry for
  96          * the copies but probably not worth the effort.
  97          */
  98         ip_frag_init(skb, hlen, ll_rs, frag_max_size, false, &state);
  99
 100         while (state.left > 0) {
 101                 struct sk_buff *skb2;
 102
 103                 skb2 = ip_frag_next(skb, &state);
 104                 if (IS_ERR(skb2)) {
 105                         err = PTR_ERR(skb2);
 106                         goto blackhole;
 107                 }
 108
 109                 skb2->tstamp = tstamp;
 110                 err = output(net, sk, data, skb2);
 111                 if (err)
 112                         goto blackhole;
 113         }
 114         consume_skb(skb);
 115         return err;
 116
 117 blackhole:
 118         kfree_skb(skb);
 119         return 0;
 120 }
 121
 122 /* ip_defrag() expects IPCB() in place. */
 123 static void br_skb_cb_save(struct sk_buff *skb, struct br_input_skb_cb *cb,
 124                            size_t inet_skb_parm_size)
 125 {
 126         memcpy(cb, skb->cb, sizeof(*cb));
 127         memset(skb->cb, 0, inet_skb_parm_size);
 128 }
 129
 130 static void br_skb_cb_restore(struct sk_buff *skb,
 131                               const struct br_input_skb_cb *cb,
 132                               u16 fragsz)
 133 {
 134         memcpy(skb->cb, cb, sizeof(*cb));
 135         BR_INPUT_SKB_CB(skb)->frag_max_size = fragsz;
 136 }
 137
 138 static unsigned int nf_ct_br_defrag4(struct sk_buff *skb,
 139                                      const struct nf_hook_state *state)
 140 {
 141         u16 zone_id = NF_CT_DEFAULT_ZONE_ID;
 142         enum ip_conntrack_info ctinfo;
 143         struct br_input_skb_cb cb;
 144         const struct nf_conn *ct;
 145         int err;
 146
 147         if (!ip_is_fragment(ip_hdr(skb)))
 148                 return NF_ACCEPT;
 149
 150         ct = nf_ct_get(skb, &ctinfo);
 151         if (ct)
 152                 zone_id = nf_ct_zone_id(nf_ct_zone(ct), CTINFO2DIR(ctinfo));
 153
 154         br_skb_cb_save(skb, &cb, sizeof(struct inet_skb_parm));
 155         local_bh_disable();
 156         err = ip_defrag(state->net, skb,
 157                         IP_DEFRAG_CONNTRACK_BRIDGE_IN + zone_id);
 158         local_bh_enable();
 159         if (!err) {
 160                 br_skb_cb_restore(skb, &cb, IPCB(skb)->frag_max_size);
 161                 skb->ignore_df = 1;
 162                 return NF_ACCEPT;
 163         }
 164
 165         return NF_STOLEN;
 166 }
 167
 168 static unsigned int nf_ct_br_defrag6(struct sk_buff *skb,
 169                                      const struct nf_hook_state *state)
 170 {
 171 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
 172         u16 zone_id = NF_CT_DEFAULT_ZONE_ID;
 173         enum ip_conntrack_info ctinfo;
 174         struct br_input_skb_cb cb;
 175         const struct nf_conn *ct;
 176         int err;
 177
 178         ct = nf_ct_get(skb, &ctinfo);
 179         if (ct)
 180                 zone_id = nf_ct_zone_id(nf_ct_zone(ct), CTINFO2DIR(ctinfo));
 181
 182         br_skb_cb_save(skb, &cb, sizeof(struct inet6_skb_parm));
 183
 184         err = nf_ct_frag6_gather(state->net, skb,
 185                                  IP_DEFRAG_CONNTRACK_BRIDGE_IN + zone_id);
 186         /* queued */
 187         if (err == -EINPROGRESS)
 188                 return NF_STOLEN;
 189
 190         br_skb_cb_restore(skb, &cb, IP6CB(skb)->frag_max_size);
 191         return err == 0 ? NF_ACCEPT : NF_DROP;
 192 #else
 193         return NF_ACCEPT;
 194 #endif
 195 }
 196
 197 static int nf_ct_br_ip_check(const struct sk_buff *skb)
 198 {
 199         const struct iphdr *iph;
 200         int nhoff, len;
 201
 202         nhoff = skb_network_offset(skb);
 203         iph = ip_hdr(skb);
 204         if (iph->ihl < 5 ||
 205             iph->version != 4)
 206                 return -1;
 207
 208         len = ntohs(iph->tot_len);
 209         if (skb->len < nhoff + len ||
 210             len < (iph->ihl * 4))
 211                 return -1;
 212
 213         return 0;
 214 }
 215
 216 static int nf_ct_br_ipv6_check(const struct sk_buff *skb)
 217 {
 218         const struct ipv6hdr *hdr;
 219         int nhoff, len;
 220
 221         nhoff = skb_network_offset(skb);
 222         hdr = ipv6_hdr(skb);
 223         if (hdr->version != 6)
 224                 return -1;
 225
 226         len = ntohs(hdr->payload_len) + sizeof(struct ipv6hdr) + nhoff;
 227         if (skb->len < len)
 228                 return -1;
 229
 230         return 0;
 231 }
 232
 233 static unsigned int nf_ct_bridge_pre(void *priv, struct sk_buff *skb,
 234                                      const struct nf_hook_state *state)
 235 {
 236         struct nf_hook_state bridge_state = *state;
 237         enum ip_conntrack_info ctinfo;
 238         struct nf_conn *ct;
 239         u32 len;
 240         int ret;
 241
 242         ct = nf_ct_get(skb, &ctinfo);
 243         if ((ct && !nf_ct_is_template(ct)) ||
 244             ctinfo == IP_CT_UNTRACKED)
 245                 return NF_ACCEPT;
 246
 247         switch (skb->protocol) {
 248         case htons(ETH_P_IP):
 249                 if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 250                         return NF_ACCEPT;
 251
 252                 len = ntohs(ip_hdr(skb)->tot_len);
 253                 if (pskb_trim_rcsum(skb, len))
 254                         return NF_ACCEPT;
 255
 256                 if (nf_ct_br_ip_check(skb))
 257                         return NF_ACCEPT;
 258
 259                 bridge_state.pf = NFPROTO_IPV4;
 260                 ret = nf_ct_br_defrag4(skb, &bridge_state);
 261                 break;
 262         case htons(ETH_P_IPV6):
 263                 if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
 264                         return NF_ACCEPT;
 265
 266                 len = sizeof(struct ipv6hdr) + ntohs(ipv6_hdr(skb)->payload_len);
 267                 if (pskb_trim_rcsum(skb, len))
 268                         return NF_ACCEPT;
 269
 270                 if (nf_ct_br_ipv6_check(skb))
 271                         return NF_ACCEPT;
 272
 273                 bridge_state.pf = NFPROTO_IPV6;
 274                 ret = nf_ct_br_defrag6(skb, &bridge_state);
 275                 break;
 276         default:
 277                 nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
 278                 return NF_ACCEPT;
 279         }
 280
 281         if (ret != NF_ACCEPT)
 282                 return ret;
 283
 284         return nf_conntrack_in(skb, &bridge_state);
 285 }
 286
 287 static void nf_ct_bridge_frag_save(struct sk_buff *skb,
 288                                    struct nf_bridge_frag_data *data)
 289 {
 290         if (skb_vlan_tag_present(skb)) {
 291                 data->vlan_present = true;
 292                 data->vlan_tci = skb->vlan_tci;
 293                 data->vlan_proto = skb->vlan_proto;
 294         } else {
 295                 data->vlan_present = false;
 296         }
 297         skb_copy_from_linear_data_offset(skb, -ETH_HLEN, data->mac, ETH_HLEN);
 298 }
 299
 300 static unsigned int
 301 nf_ct_bridge_refrag(struct sk_buff *skb, const struct nf_hook_state *state,
 302                     int (*output)(struct net *, struct sock *sk,
 303                                   const struct nf_bridge_frag_data *data,
 304                                   struct sk_buff *))
 305 {
 306         struct nf_bridge_frag_data data;
 307
 308         if (!BR_INPUT_SKB_CB(skb)->frag_max_size)
 309                 return NF_ACCEPT;
 310
 311         nf_ct_bridge_frag_save(skb, &data);
 312         switch (skb->protocol) {
 313         case htons(ETH_P_IP):
 314                 nf_br_ip_fragment(state->net, state->sk, skb, &data, output);
 315                 break;
 316         case htons(ETH_P_IPV6):
 317                 nf_br_ip6_fragment(state->net, state->sk, skb, &data, output);
 318                 break;
 319         default:
 320                 WARN_ON_ONCE(1);
 321                 return NF_DROP;
 322         }
 323
 324         return NF_STOLEN;
 325 }
 326
 327 /* Actually only slow path refragmentation needs this. */
 328 static int nf_ct_bridge_frag_restore(struct sk_buff *skb,
 329                                      const struct nf_bridge_frag_data *data)
 330 {
 331         int err;
 332
 333         err = skb_cow_head(skb, ETH_HLEN);
 334         if (err) {
 335                 kfree_skb(skb);
 336                 return -ENOMEM;
 337         }
 338         if (data->vlan_present)
 339                 __vlan_hwaccel_put_tag(skb, data->vlan_proto, data->vlan_tci);
 340         else if (skb_vlan_tag_present(skb))
 341                 __vlan_hwaccel_clear_tag(skb);
 342
 343         skb_copy_to_linear_data_offset(skb, -ETH_HLEN, data->mac, ETH_HLEN);
 344         skb_reset_mac_header(skb);
 345
 346         return 0;
 347 }
 348
 349 static int nf_ct_bridge_refrag_post(struct net *net, struct sock *sk,
 350                                     const struct nf_bridge_frag_data *data,
 351                                     struct sk_buff *skb)
 352 {
 353         int err;
 354
 355         err = nf_ct_bridge_frag_restore(skb, data);
 356         if (err < 0)
 357                 return err;
 358
 359         return br_dev_queue_push_xmit(net, sk, skb);
 360 }
 361
 362 static unsigned int nf_ct_bridge_confirm(struct sk_buff *skb)
 363 {
 364         enum ip_conntrack_info ctinfo;
 365         struct nf_conn *ct;
 366         int protoff;
 367
 368         ct = nf_ct_get(skb, &ctinfo);
 369         if (!ct || ctinfo == IP_CT_RELATED_REPLY)
 370                 return nf_conntrack_confirm(skb);
 371
 372         switch (skb->protocol) {
 373         case htons(ETH_P_IP):
 374                 protoff = skb_network_offset(skb) + ip_hdrlen(skb);
 375                 break;
 376         case htons(ETH_P_IPV6): {
 377                  unsigned char pnum = ipv6_hdr(skb)->nexthdr;
 378                 __be16 frag_off;
 379
 380                 protoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &pnum,
 381                                            &frag_off);
 382                 if (protoff < 0 || (frag_off & htons(~0x7)) != 0)
 383                         return nf_conntrack_confirm(skb);
 384                 }
 385                 break;
 386         default:
 387                 return NF_ACCEPT;
 388         }
 389         return nf_confirm(skb, protoff, ct, ctinfo);
 390 }
 391
 392 static unsigned int nf_ct_bridge_post(void *priv, struct sk_buff *skb,
 393                                       const struct nf_hook_state *state)
 394 {
 395         int ret;
 396
 397         ret = nf_ct_bridge_confirm(skb);
 398         if (ret != NF_ACCEPT)
 399                 return ret;
 400
 401         return nf_ct_bridge_refrag(skb, state, nf_ct_bridge_refrag_post);
 402 }
 403
 404 static struct nf_hook_ops nf_ct_bridge_hook_ops[] __read_mostly = {
 405         {
 406                 .hook           = nf_ct_bridge_pre,
 407                 .pf             = NFPROTO_BRIDGE,
 408                 .hooknum        = NF_BR_PRE_ROUTING,
 409                 .priority       = NF_IP_PRI_CONNTRACK,
 410         },
 411         {
 412                 .hook           = nf_ct_bridge_post,
 413                 .pf             = NFPROTO_BRIDGE,
 414                 .hooknum        = NF_BR_POST_ROUTING,
 415                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM,
 416         },
 417 };
 418
 419 static struct nf_ct_bridge_info bridge_info = {
 420         .ops            = nf_ct_bridge_hook_ops,
 421         .ops_size       = ARRAY_SIZE(nf_ct_bridge_hook_ops),
 422         .me             = THIS_MODULE,
 423 };
 424
 425 static int __init nf_conntrack_l3proto_bridge_init(void)
 426 {
 427         nf_ct_bridge_register(&bridge_info);
 428
 429         return 0;
 430 }
 431
 432 static void __exit nf_conntrack_l3proto_bridge_fini(void)
 433 {
 434         nf_ct_bridge_unregister(&bridge_info);
 435 }
 436
 437 module_init(nf_conntrack_l3proto_bridge_init);
 438 module_exit(nf_conntrack_l3proto_bridge_fini);
 439
 440 MODULE_ALIAS("nf_conntrack-" __stringify(AF_BRIDGE));
 441 MODULE_LICENSE("GPL");