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