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 /* Hook for brouter */
  23 br_should_route_hook_t __rcu *br_should_route_hook __read_mostly;
  24 EXPORT_SYMBOL(br_should_route_hook);
  25
  26 static int br_pass_frame_up(struct sk_buff *skb)
  27 {
  28         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
  29         struct net_bridge *br = netdev_priv(brdev);
  30         struct br_cpu_netstats *brstats = this_cpu_ptr(br->stats);
  31
  32         u64_stats_update_begin(&brstats->syncp);
  33         brstats->rx_packets++;
  34         brstats->rx_bytes += skb->len;
  35         u64_stats_update_end(&brstats->syncp);
  36
  37         indev = skb->dev;
  38         skb->dev = brdev;
  39
  40         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
  41                        netif_receive_skb);
  42 }
  43
  44 /* note: already called with rcu_read_lock */
  45 int br_handle_frame_finish(struct sk_buff *skb)
  46 {
  47         const unsigned char *dest = eth_hdr(skb)->h_dest;
  48         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
  49         struct net_bridge *br;
  50         struct net_bridge_fdb_entry *dst;
  51         struct net_bridge_mdb_entry *mdst;
  52         struct sk_buff *skb2;
  53
  54         if (!p || p->state == BR_STATE_DISABLED)
  55                 goto drop;
  56
  57         /* insert into forwarding database after filtering to avoid spoofing */
  58         br = p->br;
  59         br_fdb_update(br, p, eth_hdr(skb)->h_source);
  60
  61         if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
  62             br_multicast_rcv(br, p, skb))
  63                 goto drop;
  64
  65         if (p->state == BR_STATE_LEARNING)
  66                 goto drop;
  67
  68         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
  69
  70         /* The packet skb2 goes to the local host (NULL to skip). */
  71         skb2 = NULL;
  72
  73         if (br->dev->flags & IFF_PROMISC)
  74                 skb2 = skb;
  75
  76         dst = NULL;
  77
  78         if (is_broadcast_ether_addr(dest))
  79                 skb2 = skb;
  80         else if (is_multicast_ether_addr(dest)) {
  81                 mdst = br_mdb_get(br, skb);
  82                 if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) {
  83                         if ((mdst && mdst->mglist) ||
  84                             br_multicast_is_router(br))
  85                                 skb2 = skb;
  86                         br_multicast_forward(mdst, skb, skb2);
  87                         skb = NULL;
  88                         if (!skb2)
  89                                 goto out;
  90                 } else
  91                         skb2 = skb;
  92
  93                 br->dev->stats.multicast++;
  94         } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
  95                 skb2 = skb;
  96                 /* Do not forward the packet since it's local. */
  97                 skb = NULL;
  98         }
  99
 100         if (skb) {
 101                 if (dst) {
 102                         dst->used = jiffies;
 103                         br_forward(dst->dst, skb, skb2);
 104                 } else
 105                         br_flood_forward(br, skb, skb2);
 106         }
 107
 108         if (skb2)
 109                 return br_pass_frame_up(skb2);
 110
 111 out:
 112         return 0;
 113 drop:
 114         kfree_skb(skb);
 115         goto out;
 116 }
 117
 118 /* note: already called with rcu_read_lock */
 119 static int br_handle_local_finish(struct sk_buff *skb)
 120 {
 121         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 122
 123         br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
 124         return 0;        /* process further */
 125 }
 126
 127 /*
 128  * Return NULL if skb is handled
 129  * note: already called with rcu_read_lock
 130  */
 131 rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 132 {
 133         struct net_bridge_port *p;
 134         struct sk_buff *skb = *pskb;
 135         const unsigned char *dest = eth_hdr(skb)->h_dest;
 136         br_should_route_hook_t *rhook;
 137
 138         if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
 139                 return RX_HANDLER_PASS;
 140
 141         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 142                 goto drop;
 143
 144         skb = skb_share_check(skb, GFP_ATOMIC);
 145         if (!skb)
 146                 return RX_HANDLER_CONSUMED;
 147
 148         p = br_port_get_rcu(skb->dev);
 149
 150         if (unlikely(is_link_local(dest))) {
 151                 /*
 152                  * See IEEE 802.1D Table 7-10 Reserved addresses
 153                  *
 154                  * Assignment                           Value
 155                  * Bridge Group Address         01-80-C2-00-00-00
 156                  * (MAC Control) 802.3          01-80-C2-00-00-01
 157                  * (Link Aggregation) 802.3     01-80-C2-00-00-02
 158                  * 802.1X PAE address           01-80-C2-00-00-03
 159                  *
 160                  * 802.1AB LLDP                 01-80-C2-00-00-0E
 161                  *
 162                  * Others reserved for future standardization
 163                  */
 164                 switch (dest[5]) {
 165                 case 0x00:      /* Bridge Group Address */
 166                         /* If STP is turned off,
 167                            then must forward to keep loop detection */
 168                         if (p->br->stp_enabled == BR_NO_STP)
 169                                 goto forward;
 170                         break;
 171
 172                 case 0x01:      /* IEEE MAC (Pause) */
 173                         goto drop;
 174
 175                 default:
 176                         /* Allow selective forwarding for most other protocols */
 177                         if (p->br->group_fwd_mask & (1u << dest[5]))
 178                                 goto forward;
 179                 }
 180
 181                 /* Deliver packet to local host only */
 182                 if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
 183                             NULL, br_handle_local_finish)) {
 184                         return RX_HANDLER_CONSUMED; /* consumed by filter */
 185                 } else {
 186                         *pskb = skb;
 187                         return RX_HANDLER_PASS; /* continue processing */
 188                 }
 189         }
 190
 191 forward:
 192         switch (p->state) {
 193         case BR_STATE_FORWARDING:
 194                 rhook = rcu_dereference(br_should_route_hook);
 195                 if (rhook) {
 196                         if ((*rhook)(skb)) {
 197                                 *pskb = skb;
 198                                 return RX_HANDLER_PASS;
 199                         }
 200                         dest = eth_hdr(skb)->h_dest;
 201                 }
 202                 /* fall through */
 203         case BR_STATE_LEARNING:
 204                 if (ether_addr_equal(p->br->dev->dev_addr, dest))
 205                         skb->pkt_type = PACKET_HOST;
 206
 207                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
 208                         br_handle_frame_finish);
 209                 break;
 210         default:
 211 drop:
 212                 kfree_skb(skb);
 213         }
 214         return RX_HANDLER_CONSUMED;
 215 }