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 <linux/rculist.h>
  21 #include "br_private.h"
  22
  23 /* Hook for brouter */
  24 br_should_route_hook_t __rcu *br_should_route_hook __read_mostly;
  25 EXPORT_SYMBOL(br_should_route_hook);
  26
  27 static int br_pass_frame_up(struct sk_buff *skb)
  28 {
  29         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
  30         struct net_bridge *br = netdev_priv(brdev);
  31         struct pcpu_sw_netstats *brstats = this_cpu_ptr(br->stats);
  32         struct net_port_vlans *pv;
  33
  34         u64_stats_update_begin(&brstats->syncp);
  35         brstats->rx_packets++;
  36         brstats->rx_bytes += skb->len;
  37         u64_stats_update_end(&brstats->syncp);
  38
  39         /* Bridge is just like any other port.  Make sure the
  40          * packet is allowed except in promisc modue when someone
  41          * may be running packet capture.
  42          */
  43         pv = br_get_vlan_info(br);
  44         if (!(brdev->flags & IFF_PROMISC) &&
  45             !br_allowed_egress(br, pv, skb)) {
  46                 kfree_skb(skb);
  47                 return NET_RX_DROP;
  48         }
  49
  50         indev = skb->dev;
  51         skb->dev = brdev;
  52         skb = br_handle_vlan(br, pv, skb);
  53         if (!skb)
  54                 return NET_RX_DROP;
  55
  56         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
  57                        netif_receive_skb);
  58 }
  59
  60 /* note: already called with rcu_read_lock */
  61 int br_handle_frame_finish(struct sk_buff *skb)
  62 {
  63         const unsigned char *dest = eth_hdr(skb)->h_dest;
  64         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
  65         struct net_bridge *br;
  66         struct net_bridge_fdb_entry *dst;
  67         struct net_bridge_mdb_entry *mdst;
  68         struct sk_buff *skb2;
  69         bool unicast = true;
  70         u16 vid = 0;
  71
  72         if (!p || p->state == BR_STATE_DISABLED)
  73                 goto drop;
  74
  75         if (!br_allowed_ingress(p->br, nbp_get_vlan_info(p), skb, &vid))
  76                 goto out;
  77
  78         /* insert into forwarding database after filtering to avoid spoofing */
  79         br = p->br;
  80         if (p->flags & BR_LEARNING)
  81                 br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
  82
  83         if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
  84             br_multicast_rcv(br, p, skb, vid))
  85                 goto drop;
  86
  87         if (p->state == BR_STATE_LEARNING)
  88                 goto drop;
  89
  90         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
  91
  92         /* The packet skb2 goes to the local host (NULL to skip). */
  93         skb2 = NULL;
  94
  95         if (br->dev->flags & IFF_PROMISC)
  96                 skb2 = skb;
  97
  98         dst = NULL;
  99
 100         if (is_broadcast_ether_addr(dest)) {
 101                 skb2 = skb;
 102                 unicast = false;
 103         } else if (is_multicast_ether_addr(dest)) {
 104                 mdst = br_mdb_get(br, skb, vid);
 105                 if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
 106                     br_multicast_querier_exists(br, eth_hdr(skb))) {
 107                         if ((mdst && mdst->mglist) ||
 108                             br_multicast_is_router(br))
 109                                 skb2 = skb;
 110                         br_multicast_forward(mdst, skb, skb2);
 111                         skb = NULL;
 112                         if (!skb2)
 113                                 goto out;
 114                 } else
 115                         skb2 = skb;
 116
 117                 unicast = false;
 118                 br->dev->stats.multicast++;
 119         } else if ((dst = __br_fdb_get(br, dest, vid)) &&
 120                         dst->is_local) {
 121                 skb2 = skb;
 122                 /* Do not forward the packet since it's local. */
 123                 skb = NULL;
 124         }
 125
 126         if (skb) {
 127                 if (dst) {
 128                         dst->used = jiffies;
 129                         br_forward(dst->dst, skb, skb2);
 130                 } else
 131                         br_flood_forward(br, skb, skb2, unicast);
 132         }
 133
 134         if (skb2)
 135                 return br_pass_frame_up(skb2);
 136
 137 out:
 138         return 0;
 139 drop:
 140         kfree_skb(skb);
 141         goto out;
 142 }
 143
 144 /* note: already called with rcu_read_lock */
 145 static int br_handle_local_finish(struct sk_buff *skb)
 146 {
 147         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 148         u16 vid = 0;
 149
 150         /* check if vlan is allowed, to avoid spoofing */
 151         if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
 152                 br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
 153         return 0;        /* process further */
 154 }
 155
 156 /*
 157  * Return NULL if skb is handled
 158  * note: already called with rcu_read_lock
 159  */
 160 rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 161 {
 162         struct net_bridge_port *p;
 163         struct sk_buff *skb = *pskb;
 164         const unsigned char *dest = eth_hdr(skb)->h_dest;
 165         br_should_route_hook_t *rhook;
 166
 167         if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
 168                 return RX_HANDLER_PASS;
 169
 170         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 171                 goto drop;
 172
 173         skb = skb_share_check(skb, GFP_ATOMIC);
 174         if (!skb)
 175                 return RX_HANDLER_CONSUMED;
 176
 177         p = br_port_get_rcu(skb->dev);
 178
 179         if (unlikely(is_link_local_ether_addr(dest))) {
 180                 u16 fwd_mask = p->br->group_fwd_mask_required;
 181
 182                 /*
 183                  * See IEEE 802.1D Table 7-10 Reserved addresses
 184                  *
 185                  * Assignment                           Value
 186                  * Bridge Group Address         01-80-C2-00-00-00
 187                  * (MAC Control) 802.3          01-80-C2-00-00-01
 188                  * (Link Aggregation) 802.3     01-80-C2-00-00-02
 189                  * 802.1X PAE address           01-80-C2-00-00-03
 190                  *
 191                  * 802.1AB LLDP                 01-80-C2-00-00-0E
 192                  *
 193                  * Others reserved for future standardization
 194                  */
 195                 switch (dest[5]) {
 196                 case 0x00:      /* Bridge Group Address */
 197                         /* If STP is turned off,
 198                            then must forward to keep loop detection */
 199                         if (p->br->stp_enabled == BR_NO_STP ||
 200                             fwd_mask & (1u << dest[5]))
 201                                 goto forward;
 202                         break;
 203
 204                 case 0x01:      /* IEEE MAC (Pause) */
 205                         goto drop;
 206
 207                 default:
 208                         /* Allow selective forwarding for most other protocols */
 209                         fwd_mask |= p->br->group_fwd_mask;
 210                         if (fwd_mask & (1u << dest[5]))
 211                                 goto forward;
 212                 }
 213
 214                 /* Deliver packet to local host only */
 215                 if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
 216                             NULL, br_handle_local_finish)) {
 217                         return RX_HANDLER_CONSUMED; /* consumed by filter */
 218                 } else {
 219                         *pskb = skb;
 220                         return RX_HANDLER_PASS; /* continue processing */
 221                 }
 222         }
 223
 224 forward:
 225         switch (p->state) {
 226         case BR_STATE_FORWARDING:
 227                 rhook = rcu_dereference(br_should_route_hook);
 228                 if (rhook) {
 229                         if ((*rhook)(skb)) {
 230                                 *pskb = skb;
 231                                 return RX_HANDLER_PASS;
 232                         }
 233                         dest = eth_hdr(skb)->h_dest;
 234                 }
 235                 /* fall through */
 236         case BR_STATE_LEARNING:
 237                 if (ether_addr_equal(p->br->dev->dev_addr, dest))
 238                         skb->pkt_type = PACKET_HOST;
 239
 240                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
 241                         br_handle_frame_finish);
 242                 break;
 243         default:
 244 drop:
 245                 kfree_skb(skb);
 246         }
 247         return RX_HANDLER_CONSUMED;
 248 }