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/kernel.h>
  15 #include <linux/netdevice.h>
  16 #include <linux/etherdevice.h>
  17 #include <linux/netfilter_bridge.h>
  18 #include "br_private.h"
  19
  20 /* Bridge group multicast address 802.1d (pg 51). */
  21 const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
  22
  23 static int br_pass_frame_up(struct sk_buff *skb)
  24 {
  25         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
  26
  27         brdev->stats.rx_packets++;
  28         brdev->stats.rx_bytes += skb->len;
  29
  30         indev = skb->dev;
  31         skb->dev = brdev;
  32
  33         return NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
  34                        netif_receive_skb);
  35 }
  36
  37 /* note: already called with rcu_read_lock (preempt_disabled) */
  38 int br_handle_frame_finish(struct sk_buff *skb)
  39 {
  40         const unsigned char *dest = eth_hdr(skb)->h_dest;
  41         struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
  42         struct net_bridge *br;
  43         struct net_bridge_fdb_entry *dst;
  44         struct net_bridge_mdb_entry *mdst;
  45         struct sk_buff *skb2;
  46
  47         if (!p || p->state == BR_STATE_DISABLED)
  48                 goto drop;
  49
  50         /* insert into forwarding database after filtering to avoid spoofing */
  51         br = p->br;
  52         br_fdb_update(br, p, eth_hdr(skb)->h_source);
  53
  54         if (is_multicast_ether_addr(dest) &&
  55             br_multicast_rcv(br, p, skb))
  56                 goto drop;
  57
  58         if (p->state == BR_STATE_LEARNING)
  59                 goto drop;
  60
  61         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
  62
  63         /* The packet skb2 goes to the local host (NULL to skip). */
  64         skb2 = NULL;
  65
  66         if (br->dev->flags & IFF_PROMISC)
  67                 skb2 = skb;
  68
  69         dst = NULL;
  70
  71         if (is_multicast_ether_addr(dest)) {
  72                 mdst = br_mdb_get(br, skb);
  73                 if (mdst || BR_INPUT_SKB_CB(skb)->mrouters_only) {
  74                         if ((mdst && !hlist_unhashed(&mdst->mglist)) ||
  75                             br_multicast_is_router(br))
  76                                 skb2 = skb;
  77                         br_multicast_forward(mdst, skb, skb2);
  78                         skb = NULL;
  79                         if (!skb2)
  80                                 goto out;
  81                 } else
  82                         skb2 = skb;
  83
  84                 br->dev->stats.multicast++;
  85         } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
  86                 skb2 = skb;
  87                 /* Do not forward the packet since it's local. */
  88                 skb = NULL;
  89         }
  90
  91         if (skb) {
  92                 if (dst)
  93                         br_forward(dst->dst, skb);
  94                 else
  95                         br_flood_forward(br, skb, skb2);
  96         }
  97
  98         if (skb2)
  99                 return br_pass_frame_up(skb2);
 100
 101 out:
 102         return 0;
 103 drop:
 104         kfree_skb(skb);
 105         goto out;
 106 }
 107
 108 /* note: already called with rcu_read_lock (preempt_disabled) */
 109 static int br_handle_local_finish(struct sk_buff *skb)
 110 {
 111         struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
 112
 113         if (p)
 114                 br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
 115         return 0;        /* process further */
 116 }
 117
 118 /* Does address match the link local multicast address.
 119  * 01:80:c2:00:00:0X
 120  */
 121 static inline int is_link_local(const unsigned char *dest)
 122 {
 123         __be16 *a = (__be16 *)dest;
 124         static const __be16 *b = (const __be16 *)br_group_address;
 125         static const __be16 m = cpu_to_be16(0xfff0);
 126
 127         return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
 128 }
 129
 130 /*
 131  * Called via br_handle_frame_hook.
 132  * Return NULL if skb is handled
 133  * note: already called with rcu_read_lock (preempt_disabled)
 134  */
 135 struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
 136 {
 137         const unsigned char *dest = eth_hdr(skb)->h_dest;
 138         int (*rhook)(struct sk_buff *skb);
 139
 140         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 141                 goto drop;
 142
 143         skb = skb_share_check(skb, GFP_ATOMIC);
 144         if (!skb)
 145                 return NULL;
 146
 147         if (unlikely(is_link_local(dest))) {
 148                 /* Pause frames shouldn't be passed up by driver anyway */
 149                 if (skb->protocol == htons(ETH_P_PAUSE))
 150                         goto drop;
 151
 152                 /* If STP is turned off, then forward */
 153                 if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
 154                         goto forward;
 155
 156                 if (NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
 157                             NULL, br_handle_local_finish))
 158                         return NULL;    /* frame consumed by filter */
 159                 else
 160                         return skb;     /* continue processing */
 161         }
 162
 163 forward:
 164         switch (p->state) {
 165         case BR_STATE_FORWARDING:
 166                 rhook = rcu_dereference(br_should_route_hook);
 167                 if (rhook != NULL) {
 168                         if (rhook(skb))
 169                                 return skb;
 170                         dest = eth_hdr(skb)->h_dest;
 171                 }
 172                 /* fall through */
 173         case BR_STATE_LEARNING:
 174                 if (!compare_ether_addr(p->br->dev->dev_addr, dest))
 175                         skb->pkt_type = PACKET_HOST;
 176
 177                 NF_HOOK(PF_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
 178                         br_handle_frame_finish);
 179                 break;
 180         default:
 181 drop:
 182                 kfree_skb(skb);
 183         }
 184         return NULL;
 185 }