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 "br_private.h"
  20
  21 /* Bridge group multicast address 802.1d (pg 51). */
  22 const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
  23
  24 static int br_pass_frame_up(struct sk_buff *skb)
  25 {
  26         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
  27         struct net_bridge *br = netdev_priv(brdev);
  28         struct br_cpu_netstats *brstats = this_cpu_ptr(br->stats);
  29
  30         brstats->rx_packets++;
  31         brstats->rx_bytes += skb->len;
  32
  33         indev = skb->dev;
  34         skb->dev = brdev;
  35
  36         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
  37                        netif_receive_skb);
  38 }
  39
  40 /* note: already called with rcu_read_lock (preempt_disabled) */
  41 int br_handle_frame_finish(struct sk_buff *skb)
  42 {
  43         const unsigned char *dest = eth_hdr(skb)->h_dest;
  44         struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
  45         struct net_bridge *br;
  46         struct net_bridge_fdb_entry *dst;
  47         struct net_bridge_mdb_entry *mdst;
  48         struct sk_buff *skb2;
  49
  50         if (!p || p->state == BR_STATE_DISABLED)
  51                 goto drop;
  52
  53         /* insert into forwarding database after filtering to avoid spoofing */
  54         br = p->br;
  55         br_fdb_update(br, p, eth_hdr(skb)->h_source);
  56
  57         if (is_multicast_ether_addr(dest) &&
  58             br_multicast_rcv(br, p, skb))
  59                 goto drop;
  60
  61         if (p->state == BR_STATE_LEARNING)
  62                 goto drop;
  63
  64         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
  65
  66         /* The packet skb2 goes to the local host (NULL to skip). */
  67         skb2 = NULL;
  68
  69         if (br->dev->flags & IFF_PROMISC)
  70                 skb2 = skb;
  71
  72         dst = NULL;
  73
  74         if (is_multicast_ether_addr(dest)) {
  75                 mdst = br_mdb_get(br, skb);
  76                 if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) {
  77                         if ((mdst && !hlist_unhashed(&mdst->mglist)) ||
  78                             br_multicast_is_router(br))
  79                                 skb2 = skb;
  80                         br_multicast_forward(mdst, skb, skb2);
  81                         skb = NULL;
  82                         if (!skb2)
  83                                 goto out;
  84                 } else
  85                         skb2 = skb;
  86
  87                 br->dev->stats.multicast++;
  88         } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
  89                 skb2 = skb;
  90                 /* Do not forward the packet since it's local. */
  91                 skb = NULL;
  92         }
  93
  94         if (skb) {
  95                 if (dst)
  96                         br_forward(dst->dst, skb, skb2);
  97                 else
  98                         br_flood_forward(br, skb, skb2);
  99         }
 100
 101         if (skb2)
 102                 return br_pass_frame_up(skb2);
 103
 104 out:
 105         return 0;
 106 drop:
 107         kfree_skb(skb);
 108         goto out;
 109 }
 110
 111 /* note: already called with rcu_read_lock (preempt_disabled) */
 112 static int br_handle_local_finish(struct sk_buff *skb)
 113 {
 114         struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
 115
 116         if (p)
 117                 br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
 118         return 0;        /* process further */
 119 }
 120
 121 /* Does address match the link local multicast address.
 122  * 01:80:c2:00:00:0X
 123  */
 124 static inline int is_link_local(const unsigned char *dest)
 125 {
 126         __be16 *a = (__be16 *)dest;
 127         static const __be16 *b = (const __be16 *)br_group_address;
 128         static const __be16 m = cpu_to_be16(0xfff0);
 129
 130         return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
 131 }
 132
 133 /*
 134  * Called via br_handle_frame_hook.
 135  * Return NULL if skb is handled
 136  * note: already called with rcu_read_lock (preempt_disabled)
 137  */
 138 struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
 139 {
 140         const unsigned char *dest = eth_hdr(skb)->h_dest;
 141         int (*rhook)(struct sk_buff *skb);
 142
 143         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 144                 goto drop;
 145
 146         skb = skb_share_check(skb, GFP_ATOMIC);
 147         if (!skb)
 148                 return NULL;
 149
 150         if (unlikely(is_link_local(dest))) {
 151                 /* Pause frames shouldn't be passed up by driver anyway */
 152                 if (skb->protocol == htons(ETH_P_PAUSE))
 153                         goto drop;
 154
 155                 /* If STP is turned off, then forward */
 156                 if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
 157                         goto forward;
 158
 159                 if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
 160                             NULL, br_handle_local_finish))
 161                         return NULL;    /* frame consumed by filter */
 162                 else
 163                         return skb;     /* continue processing */
 164         }
 165
 166 forward:
 167         switch (p->state) {
 168         case BR_STATE_FORWARDING:
 169                 rhook = rcu_dereference(br_should_route_hook);
 170                 if (rhook != NULL) {
 171                         if (rhook(skb))
 172                                 return skb;
 173                         dest = eth_hdr(skb)->h_dest;
 174                 }
 175                 /* fall through */
 176         case BR_STATE_LEARNING:
 177                 if (!compare_ether_addr(p->br->dev->dev_addr, dest))
 178                         skb->pkt_type = PACKET_HOST;
 179
 180                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
 181                         br_handle_frame_finish);
 182                 break;
 183         default:
 184 drop:
 185                 kfree_skb(skb);
 186         }
 187         return NULL;
 188 }