net/bridge/br_input.c

   1 /*
   2  *      Handle incoming frames
   3  *      Linux ethernet bridge
   4  *
   5  *      Authors:
   6  *      Lennert Buytenhek               <buytenh@gnu.org>
   7  *
   8  *      This program is free software; you can redistribute it and/or
   9  *      modify it under the terms of the GNU General Public License
  10  *      as published by the Free Software Foundation; either version
  11  *      2 of the License, or (at your option) any later version.
  12  */
  13
  14 #include <linux/slab.h>
  15 #include <linux/kernel.h>
  16 #include <linux/netdevice.h>
  17 #include <linux/etherdevice.h>
  18 #include <linux/netfilter_bridge.h>
  19 #include <linux/neighbour.h>
  20 #include <net/arp.h>
  21 #include <linux/export.h>
  22 #include <linux/rculist.h>
  23 #include "br_private.h"
  24
  25 /* Hook for brouter */
  26 br_should_route_hook_t __rcu *br_should_route_hook __read_mostly;
  27 EXPORT_SYMBOL(br_should_route_hook);
  28
  29 static int
  30 br_netif_receive_skb(struct net *net, struct sock *sk, struct sk_buff *skb)
  31 {
  32         return netif_receive_skb(skb);
  33 }
  34
  35 static int br_pass_frame_up(struct sk_buff *skb)
  36 {
  37         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
  38         struct net_bridge *br = netdev_priv(brdev);
  39         struct net_bridge_vlan_group *vg;
  40         struct pcpu_sw_netstats *brstats = this_cpu_ptr(br->stats);
  41
  42         u64_stats_update_begin(&brstats->syncp);
  43         brstats->rx_packets++;
  44         brstats->rx_bytes += skb->len;
  45         u64_stats_update_end(&brstats->syncp);
  46
  47         vg = br_vlan_group_rcu(br);
  48         /* Bridge is just like any other port.  Make sure the
  49          * packet is allowed except in promisc modue when someone
  50          * may be running packet capture.
  51          */
  52         if (!(brdev->flags & IFF_PROMISC) &&
  53             !br_allowed_egress(vg, skb)) {
  54                 kfree_skb(skb);
  55                 return NET_RX_DROP;
  56         }
  57
  58         indev = skb->dev;
  59         skb->dev = brdev;
  60         skb = br_handle_vlan(br, vg, skb);
  61         if (!skb)
  62                 return NET_RX_DROP;
  63
  64         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN,
  65                        dev_net(indev), NULL, skb, indev, NULL,
  66                        br_netif_receive_skb);
  67 }
  68
  69 static void br_do_proxy_arp(struct sk_buff *skb, struct net_bridge *br,
  70                             u16 vid, struct net_bridge_port *p)
  71 {
  72         struct net_device *dev = br->dev;
  73         struct neighbour *n;
  74         struct arphdr *parp;
  75         u8 *arpptr, *sha;
  76         __be32 sip, tip;
  77
  78         BR_INPUT_SKB_CB(skb)->proxyarp_replied = false;
  79
  80         if (dev->flags & IFF_NOARP)
  81                 return;
  82
  83         if (!pskb_may_pull(skb, arp_hdr_len(dev))) {
  84                 dev->stats.tx_dropped++;
  85                 return;
  86         }
  87         parp = arp_hdr(skb);
  88
  89         if (parp->ar_pro != htons(ETH_P_IP) ||
  90             parp->ar_op != htons(ARPOP_REQUEST) ||
  91             parp->ar_hln != dev->addr_len ||
  92             parp->ar_pln != 4)
  93                 return;
  94
  95         arpptr = (u8 *)parp + sizeof(struct arphdr);
  96         sha = arpptr;
  97         arpptr += dev->addr_len;        /* sha */
  98         memcpy(&sip, arpptr, sizeof(sip));
  99         arpptr += sizeof(sip);
 100         arpptr += dev->addr_len;        /* tha */
 101         memcpy(&tip, arpptr, sizeof(tip));
 102
 103         if (ipv4_is_loopback(tip) ||
 104             ipv4_is_multicast(tip))
 105                 return;
 106
 107         n = neigh_lookup(&arp_tbl, &tip, dev);
 108         if (n) {
 109                 struct net_bridge_fdb_entry *f;
 110
 111                 if (!(n->nud_state & NUD_VALID)) {
 112                         neigh_release(n);
 113                         return;
 114                 }
 115
 116                 f = __br_fdb_get(br, n->ha, vid);
 117                 if (f && ((p->flags & BR_PROXYARP) ||
 118                           (f->dst && (f->dst->flags & BR_PROXYARP_WIFI)))) {
 119                         arp_send(ARPOP_REPLY, ETH_P_ARP, sip, skb->dev, tip,
 120                                  sha, n->ha, sha);
 121                         BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
 122                 }
 123
 124                 neigh_release(n);
 125         }
 126 }
 127
 128 /* note: already called with rcu_read_lock */
 129 int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 130 {
 131         const unsigned char *dest = eth_hdr(skb)->h_dest;
 132         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 133         struct net_bridge *br;
 134         struct net_bridge_fdb_entry *dst;
 135         struct net_bridge_mdb_entry *mdst;
 136         struct sk_buff *skb2;
 137         bool unicast = true;
 138         u16 vid = 0;
 139
 140         if (!p || p->state == BR_STATE_DISABLED)
 141                 goto drop;
 142
 143         if (!br_allowed_ingress(p->br, nbp_vlan_group_rcu(p), skb, &vid))
 144                 goto out;
 145
 146         /* insert into forwarding database after filtering to avoid spoofing */
 147         br = p->br;
 148         if (p->flags & BR_LEARNING)
 149                 br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
 150
 151         if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
 152             br_multicast_rcv(br, p, skb, vid))
 153                 goto drop;
 154
 155         if (p->state == BR_STATE_LEARNING)
 156                 goto drop;
 157
 158         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
 159
 160         /* The packet skb2 goes to the local host (NULL to skip). */
 161         skb2 = NULL;
 162
 163         if (br->dev->flags & IFF_PROMISC)
 164                 skb2 = skb;
 165
 166         dst = NULL;
 167
 168         if (IS_ENABLED(CONFIG_INET) && skb->protocol == htons(ETH_P_ARP))
 169                 br_do_proxy_arp(skb, br, vid, p);
 170
 171         if (is_broadcast_ether_addr(dest)) {
 172                 skb2 = skb;
 173                 unicast = false;
 174         } else if (is_multicast_ether_addr(dest)) {
 175                 mdst = br_mdb_get(br, skb, vid);
 176                 if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
 177                     br_multicast_querier_exists(br, eth_hdr(skb))) {
 178                         if ((mdst && mdst->mglist) ||
 179                             br_multicast_is_router(br))
 180                                 skb2 = skb;
 181                         br_multicast_forward(mdst, skb, skb2);
 182                         skb = NULL;
 183                         if (!skb2)
 184                                 goto out;
 185                 } else
 186                         skb2 = skb;
 187
 188                 unicast = false;
 189                 br->dev->stats.multicast++;
 190         } else if ((dst = __br_fdb_get(br, dest, vid)) &&
 191                         dst->is_local) {
 192                 skb2 = skb;
 193                 /* Do not forward the packet since it's local. */
 194                 skb = NULL;
 195         }
 196
 197         if (skb) {
 198                 if (dst) {
 199                         dst->used = jiffies;
 200                         br_forward(dst->dst, skb, skb2);
 201                 } else
 202                         br_flood_forward(br, skb, skb2, unicast);
 203         }
 204
 205         if (skb2)
 206                 return br_pass_frame_up(skb2);
 207
 208 out:
 209         return 0;
 210 drop:
 211         kfree_skb(skb);
 212         goto out;
 213 }
 214 EXPORT_SYMBOL_GPL(br_handle_frame_finish);
 215
 216 static void __br_handle_local_finish(struct sk_buff *skb)
 217 {
 218         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 219         u16 vid = 0;
 220
 221         /* check if vlan is allowed, to avoid spoofing */
 222         if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
 223                 br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
 224 }
 225
 226 /* note: already called with rcu_read_lock */
 227 static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 228 {
 229         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 230
 231         __br_handle_local_finish(skb);
 232
 233         BR_INPUT_SKB_CB(skb)->brdev = p->br->dev;
 234         br_pass_frame_up(skb);
 235         return 0;
 236 }
 237
 238 /*
 239  * Return NULL if skb is handled
 240  * note: already called with rcu_read_lock
 241  */
 242 rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 243 {
 244         struct net_bridge_port *p;
 245         struct sk_buff *skb = *pskb;
 246         const unsigned char *dest = eth_hdr(skb)->h_dest;
 247         br_should_route_hook_t *rhook;
 248
 249         if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
 250                 return RX_HANDLER_PASS;
 251
 252         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 253                 goto drop;
 254
 255         skb = skb_share_check(skb, GFP_ATOMIC);
 256         if (!skb)
 257                 return RX_HANDLER_CONSUMED;
 258
 259         p = br_port_get_rcu(skb->dev);
 260
 261         if (unlikely(is_link_local_ether_addr(dest))) {
 262                 u16 fwd_mask = p->br->group_fwd_mask_required;
 263
 264                 /*
 265                  * See IEEE 802.1D Table 7-10 Reserved addresses
 266                  *
 267                  * Assignment                           Value
 268                  * Bridge Group Address         01-80-C2-00-00-00
 269                  * (MAC Control) 802.3          01-80-C2-00-00-01
 270                  * (Link Aggregation) 802.3     01-80-C2-00-00-02
 271                  * 802.1X PAE address           01-80-C2-00-00-03
 272                  *
 273                  * 802.1AB LLDP                 01-80-C2-00-00-0E
 274                  *
 275                  * Others reserved for future standardization
 276                  */
 277                 switch (dest[5]) {
 278                 case 0x00:      /* Bridge Group Address */
 279                         /* If STP is turned off,
 280                            then must forward to keep loop detection */
 281                         if (p->br->stp_enabled == BR_NO_STP ||
 282                             fwd_mask & (1u << dest[5]))
 283                                 goto forward;
 284                         *pskb = skb;
 285                         __br_handle_local_finish(skb);
 286                         return RX_HANDLER_PASS;
 287
 288                 case 0x01:      /* IEEE MAC (Pause) */
 289                         goto drop;
 290
 291                 default:
 292                         /* Allow selective forwarding for most other protocols */
 293                         fwd_mask |= p->br->group_fwd_mask;
 294                         if (fwd_mask & (1u << dest[5]))
 295                                 goto forward;
 296                 }
 297
 298                 /* Deliver packet to local host only */
 299                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, dev_net(skb->dev),
 300                         NULL, skb, skb->dev, NULL, br_handle_local_finish);
 301                 return RX_HANDLER_CONSUMED;
 302         }
 303
 304 forward:
 305         switch (p->state) {
 306         case BR_STATE_FORWARDING:
 307                 rhook = rcu_dereference(br_should_route_hook);
 308                 if (rhook) {
 309                         if ((*rhook)(skb)) {
 310                                 *pskb = skb;
 311                                 return RX_HANDLER_PASS;
 312                         }
 313                         dest = eth_hdr(skb)->h_dest;
 314                 }
 315                 /* fall through */
 316         case BR_STATE_LEARNING:
 317                 if (ether_addr_equal(p->br->dev->dev_addr, dest))
 318                         skb->pkt_type = PACKET_HOST;
 319
 320                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING,
 321                         dev_net(skb->dev), NULL, skb, skb->dev, NULL,
 322                         br_handle_frame_finish);
 323                 break;
 324         default:
 325 drop:
 326                 kfree_skb(skb);
 327         }
 328         return RX_HANDLER_CONSUMED;
 329 }