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/export.h>
  20 #include "br_private.h"
  21
  22 /* Bridge group multicast address 802.1d (pg 51). */
  23 const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
  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 br_pass_frame_up(struct sk_buff *skb)
  30 {
  31         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
  32         struct net_bridge *br = netdev_priv(brdev);
  33         struct br_cpu_netstats *brstats = this_cpu_ptr(br->stats);
  34
  35         u64_stats_update_begin(&brstats->syncp);
  36         brstats->rx_packets++;
  37         brstats->rx_bytes += skb->len;
  38         u64_stats_update_end(&brstats->syncp);
  39
  40         indev = skb->dev;
  41         skb->dev = brdev;
  42
  43         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
  44                        netif_receive_skb);
  45 }
  46
  47 /* note: already called with rcu_read_lock */
  48 int br_handle_frame_finish(struct sk_buff *skb)
  49 {
  50         const unsigned char *dest = eth_hdr(skb)->h_dest;
  51         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
  52         struct net_bridge *br;
  53         struct net_bridge_fdb_entry *dst;
  54         struct net_bridge_mdb_entry *mdst;
  55         struct sk_buff *skb2;
  56
  57         if (!p || p->state == BR_STATE_DISABLED)
  58                 goto drop;
  59
  60         /* insert into forwarding database after filtering to avoid spoofing */
  61         br = p->br;
  62         br_fdb_update(br, p, eth_hdr(skb)->h_source);
  63
  64         if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
  65             br_multicast_rcv(br, p, skb))
  66                 goto drop;
  67
  68         if (p->state == BR_STATE_LEARNING)
  69                 goto drop;
  70
  71         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
  72
  73         /* The packet skb2 goes to the local host (NULL to skip). */
  74         skb2 = NULL;
  75
  76         if (br->dev->flags & IFF_PROMISC)
  77                 skb2 = skb;
  78
  79         dst = NULL;
  80
  81         if (is_broadcast_ether_addr(dest))
  82                 skb2 = skb;
  83         else if (is_multicast_ether_addr(dest)) {
  84                 mdst = br_mdb_get(br, skb);
  85                 if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) {
  86                         if ((mdst && mdst->mglist) ||
  87                             br_multicast_is_router(br))
  88                                 skb2 = skb;
  89                         br_multicast_forward(mdst, skb, skb2);
  90                         skb = NULL;
  91                         if (!skb2)
  92                                 goto out;
  93                 } else
  94                         skb2 = skb;
  95
  96                 br->dev->stats.multicast++;
  97         } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
  98                 skb2 = skb;
  99                 /* Do not forward the packet since it's local. */
 100                 skb = NULL;
 101         }
 102
 103         if (skb) {
 104                 if (dst) {
 105                         dst->used = jiffies;
 106                         br_forward(dst->dst, skb, skb2);
 107                 } else
 108                         br_flood_forward(br, skb, skb2);
 109         }
 110
 111         if (skb2)
 112                 return br_pass_frame_up(skb2);
 113
 114 out:
 115         return 0;
 116 drop:
 117         kfree_skb(skb);
 118         goto out;
 119 }
 120
 121 /* note: already called with rcu_read_lock */
 122 static int br_handle_local_finish(struct sk_buff *skb)
 123 {
 124         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 125
 126         br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
 127         return 0;        /* process further */
 128 }
 129
 130 /* Does address match the link local multicast address.
 131  * 01:80:c2:00:00:0X
 132  */
 133 static inline int is_link_local(const unsigned char *dest)
 134 {
 135         __be16 *a = (__be16 *)dest;
 136         static const __be16 *b = (const __be16 *)br_group_address;
 137         static const __be16 m = cpu_to_be16(0xfff0);
 138
 139         return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
 140 }
 141
 142 /*
 143  * Return NULL if skb is handled
 144  * note: already called with rcu_read_lock
 145  */
 146 rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 147 {
 148         struct net_bridge_port *p;
 149         struct sk_buff *skb = *pskb;
 150         const unsigned char *dest = eth_hdr(skb)->h_dest;
 151         br_should_route_hook_t *rhook;
 152
 153         if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
 154                 return RX_HANDLER_PASS;
 155
 156         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 157                 goto drop;
 158
 159         skb = skb_share_check(skb, GFP_ATOMIC);
 160         if (!skb)
 161                 return RX_HANDLER_CONSUMED;
 162
 163         p = br_port_get_rcu(skb->dev);
 164
 165         if (unlikely(is_link_local(dest))) {
 166                 /*
 167                  * See IEEE 802.1D Table 7-10 Reserved addresses
 168                  *
 169                  * Assignment                           Value
 170                  * Bridge Group Address         01-80-C2-00-00-00
 171                  * (MAC Control) 802.3          01-80-C2-00-00-01
 172                  * (Link Aggregation) 802.3     01-80-C2-00-00-02
 173                  * 802.1X PAE address           01-80-C2-00-00-03
 174                  *
 175                  * 802.1AB LLDP                 01-80-C2-00-00-0E
 176                  *
 177                  * Others reserved for future standardization
 178                  */
 179                 switch (dest[5]) {
 180                 case 0x00:      /* Bridge Group Address */
 181                         /* If STP is turned off,
 182                            then must forward to keep loop detection */
 183                         if (p->br->stp_enabled == BR_NO_STP)
 184                                 goto forward;
 185                         break;
 186
 187                 case 0x01:      /* IEEE MAC (Pause) */
 188                         goto drop;
 189
 190                 default:
 191                         /* Allow selective forwarding for most other protocols */
 192                         if (p->br->group_fwd_mask & (1u << dest[5]))
 193                                 goto forward;
 194                 }
 195
 196                 /* Deliver packet to local host only */
 197                 if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
 198                             NULL, br_handle_local_finish)) {
 199                         return RX_HANDLER_CONSUMED; /* consumed by filter */
 200                 } else {
 201                         *pskb = skb;
 202                         return RX_HANDLER_PASS; /* continue processing */
 203                 }
 204         }
 205
 206 forward:
 207         switch (p->state) {
 208         case BR_STATE_FORWARDING:
 209                 rhook = rcu_dereference(br_should_route_hook);
 210                 if (rhook) {
 211                         if ((*rhook)(skb)) {
 212                                 *pskb = skb;
 213                                 return RX_HANDLER_PASS;
 214                         }
 215                         dest = eth_hdr(skb)->h_dest;
 216                 }
 217                 /* fall through */
 218         case BR_STATE_LEARNING:
 219                 if (!compare_ether_addr(p->br->dev->dev_addr, dest))
 220                         skb->pkt_type = PACKET_HOST;
 221
 222                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
 223                         br_handle_frame_finish);
 224                 break;
 225         default:
 226 drop:
 227                 kfree_skb(skb);
 228         }
 229         return RX_HANDLER_CONSUMED;
 230 }